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					                         Motor Module - Robotic Platform 100 Kg (RP100)
                         P07202 - Concept Development Packet
                         Status:     High Level Design Review   Last Updated:     7/13/2011 12:04 PM
                                                                Last Reviewed:   10/20/2006 11:00 PM




    Team Member         Discipline              Role                   Email Address
    Wayne Walter        ME                      Guide                  wwweme@rit.edu
    Jeff Webb           ME                      Consultant             jbw3914@rit.edu
    George Slack        EE                      Consultant             gbseee@rit.edu
    Saul Rosa           EE                      Member                 scr3319@rit.edu
    Vincent Capra       EE                      Member                 vpc4089@rit.edu
    Derrick Lee         EE                      Member                 dgl2578@rit.edu
    Muhammad Moazam EE                          Member                 mxl0333@rit.edu
    Robert Saltarelli   CE                      Project Manager        robert.saltarelli@gmail.com
    Dustin Collins      ME                      Member                 dc4fire@gmail.com
    Jasen Lomnick       ME                      Member                 jal2768@rit.edu
    Erich Hauenstein    ME                      Member                 esh9953@gmail.com
1
 2   Table of Contents
 3   I.    Project Summary ................................................................................................ 2
 4   II.   Team Roles & Responsibilities .............................................................................. 3
 5   III. Introduction ....................................................................................................... 3
 6   IV. Customer Needs ................................................................................................. 4
 7   V.    Specifications ..................................................................................................... 6
 8   VI. Related Projects & Dependencies .......................................................................... 9
 9   VII. Concept Generation and Selection......................................................................... 9
10       A. Mechanical ...................................................................................................... 9
11        A1 Motor Concept Development ........................................................................ 10
12        A2 Transmission .............................................................................................. 14
13        A3 Braking Subsystem ..................................................................................... 19
14        A4 Steering Concept Development ..................................................................... 23
15        A5 Overall Mechanical Architectures ................................................................... 30
16       B. Electrical ....................................................................................................... 31
17        B1 Controllers Concept Comparison ................................................................... 31
18        B2 Control Circuit Concepts .............................................................................. 37
19        B3 Power Sub-System ...................................................................................... 43
20        B4 Power Systems ........................................................................................... 43
21        B5 Proof of Concept – Single Battery Regulation .................................................. 47
22       C. Microprocessor ............................................................................................... 59
23        C1 Control Concepts ........................................................................................ 59
24        C2 Command and Instruction Concepts .............................................................. 63
25        C3 Architecture Concepts.................................................................................. 64
26        C4 Communication Protocols ............................................................................. 68
27   VIII. Risk Analysis .................................................................................................... 70
28   IX. Schedule ......................................................................................................... 73
29   X.    Appendix ......................................................................................................... 74
30   XI. Change History ................................................................................................. 83
31




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32   I. Project Summary
33




34

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35   II. Team Roles & Responsibilities
36




37
38


39   III.          Introduction
40   This motor module is part of the Vehicle Systems Technology Track of projects with the goal
41   of developing a land-based, scalable, modular open architecture, open source, full
42   instrumented robotic/remote controlled vehicular platform for use in a variety of education,
43   research & development, and outreach applications within and beyond the RIT KGCOE.
44
45   The particular mission of this student team is to develop a fully functional, scalable motor
46   module subsystem for use on the 100 kg (RP100) robotic vehicular platform. The overall
47   functioning of module is as follows:
48




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49
50
51   This high-level overview can be further decomposed into subsystems:




52
53
54


55   IV.       Customer Needs
56   Formulating a thorough statement of customer needs is a critical process as these needs will
57   be the foundation of all future work. The customer requirements for this motor module were
58   outlined in the P07202 Project Readiness Package (section X.2). These were translated into
59   needs statements by expressing the customer‟s requests: as an attribute of the project; in
60   terms of what the product has to do rather than in terms of how it might do it; as
61   specifically as the raw data allows; and using positive phrases when appropriate. This was
62   done so as to produce need statements that are independent of particular technological
63   solutions, maintain the detail of raw data with full fidelity, and facilitate translation into


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 64   product specifications. Once the needs statements were generated, they were sorted by
 65   logical divisions and organized into a hierarchy.
 66
 67   Customer Needs Listing:
 68
 69   1) Physical Requirements
 70   1.1) The motor modules must be configurable such that certain combinations can facilitate
 71   payloads ranging from 10kg to 100kg.
 72   1.2) The unit should support 3, 4, and 6 wheel configurations.
 73   1.3) The maximum size of the assembled unit must be within the volume constraints of 0
 74          .6x0.75x0.5 m^3.
 75   1.4) The maximum tare weight of the unit must be equal to or less than 40kg.
 76   1.5) The speed of the assembled unit must be able to reach 4.5 m/s.
 77   1.6) Each mounting location should be compatible with both idle modules and driven
 78   motored module
 79   1.7) The speed of the unit must be controllable.
 80   1.8) The unit must have a rechargeable energy source
 81   1.9) This energy source must have a max-payload run time of at least an hour.
 82   1.10) The system must have an on board shut-down intelligence, and a fail-safe braking
 83   system
 84   1.11) Must be capable of braking
 85   1.12) Must be capable of steering
 86   1.13) The system must be capable of reading the angular speed and rotations of the motor.
 87   1.14) Each motor module must be able to give feedback and receive instructions from the
 88   central processor.
 89
 90   2) Production Constraints
 91   2.1) must be open architecture, such that it can facilitate future additions.
 92   2.2) must be manufacturable in lots as small as 1 and as large as 10.
 93   2.3) Commercial concerns for this product are negligible.
 94   2.4) Must comply with federal, state, and local laws and regulations and RIT‟s policies and
 95   procedures.
 96
 97   3) Document Requirements
 98   3.1) Design documents must be open source
 99   3.2) Must be designed such that other SD teams have the option to adapt the design in the
100   future.
101   3.3) All documentation (when applicable) must reference federal, state, and local laws and
102   regulations as well as RIT‟s policies and procedures.
103
104   4) Quality Control
105   4.1) The ultimate result of this project must increase the reputation and visibility of the RIT
106   senior design program and the robotics technology “skill level” on a national basis.
107   4.2) The robotic platform must be clearly impressive to any student, parent, engineer,
108   mentor, or individual familiar with the US FIRST robotics competition.
109   4.3) The robot must have the technology and durability to be useful for the next 5+ years.
110
111   5) Compatibility
112   5.1) The processing platform of the robot must be able to integrate with project results of
113   SD team projects P07301 and P07302.
114   5.2) The robotic platform must be able to integrate with the SD P07203 results.
115
116

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117   V.        Specifications
118   The next crucial phase of the design process was to generate engineering specifications that
119   serve as the crucible when evaluating possible solutions. To generate our specifications, a
120   needs-metrics matrix was created to elucidate the dependencies between applicable
121   customer needs and possible engineering metrics.
122
                                         Engineering Metrics




                                         Mounting Site supports Idler and Driven Modules




                                         Electronics Power Consumption

                                         Wheel Position Resolution

                                         Communications Protocol
                                         Operating Temperature
                                         Mechanical Advantage




                                         Min Turning Angle
                                         Stopping Torque




                                         Processor Speed



                                         Steering Torque

                                         Instruction Set



                                          Motor Voltage
                                         Charging Time
                                         Battery Power
                                         Axle Strength

                                         Motor Torque
                                         Motor Power




      Customer Requirements
      1.1) Payloads ranging from 10kg to
      100kg.                             X   X X X X X            X    X              X
      1.2) The unit should support 3, 4,
      and 6 wheel configurations.          X X X X X X            X    X
      1.3) Volume Constraints              X               X   X
      1.4) The maximum tare weight of
      the unit must be equal to or less
      than 40kg.                         X   X X X X X     X   X
      1.5) The speed of the assembled
      unit must be able to reach 4.5
      m/s.                               X   X X X X X   X X     X
      1.7) The speed of the unit must be
      controllable.                                      X       X X
      1.8) The unit must have a
      rechargeable energy source                     X X
      1.9) This energy source must have
      a max-payload run time of at least
      an hour.                               X X X   X       X X                      X
      1.10) The system must have an on
      board shut-down intelligence, and                  X         X


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          a fail-safe braking system
          1.11) Must be capable of braking                  X X                              X
          1.12) Must be capable of steering                             X          X         X
          1.13) The system must be capable
          of reading the angular speed and
          rotations of the motor.                                    X                   X
          1.14) Each motor module must be
          able to give feedback and receive
          instructions from the central
          processor.                                                 X                       X
          2.1) must be open architecture,
          such that it can facilitate future
          additions.                                                                             X
          3.2) Must be designed such that
          other SD teams have the option to
          adapt the design in the future.                                                    X X
          4.3) The robot must have the
          technology and durability to be
          useful for the next 5+ years.         X X                                                  X
          5.1) The processing platform of the
          robot must be able to integrate
          with project results of SD team
          projects P07301 and P07302.                                                        X X
          5.2) The robotic platform must be
          able to integrate with the SD
          P07203 results.                             X X
123                                        Table V.i: Needs-metrics matrix
124
125       Using these relations in conjunction with an engineering analysis and meetings with the
126       customer allowed for the aforementioned customer needs to be translated into the following
127       specifications:
128
                 Customer
Specification                                                                    Unit of                       Ideal
                   Need              Design Specification          Importance                Marginal Value
  Number                                                                        Measure                        Value
                  Number
                               Physical Requirements
      1               1.1      Max Payload                             9          kg                 80         100
      2          1.1,1.4,4.3 Axle Strength                             6          Pa
                1.1,1.2,1.4,1.
      3              5,5.2     Motor Torque                            9          N-m                1.25        2
                1.1,1.2,1.4,1.
      4           5,1.9,5.2 Motor Power                                9           W                 150        300
                1.1,1.2,1.4,1.
      5           5,1.9,1.11 Stopping Torque                           9          N-m                    4       6
                     1.1-
      6         1.4,1.9,1.12 Steering Force                            3           N                 24         39
                               The unit should support 3, 4, and
      7               1.2      6 wheel configurations                  9          List           3 and/or 4    3,4 & 6
                                                                                                              <0.6x0.7
      8             1.3     Packaging Envelope                         9          m              <.8x.95x.7     5x0.5
      9             1.4     Tare Weight                                9          kg                <60          <40


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10        1.5     Max Speed                               9     m/s      2.5    4.5
                                                              Samples/
11    1.5,1.7,1.13 Wheel Position Resolution              3     Sec
     1.5,1.7,1.10,1
12      .13,1.14 Processor Speed                          3     IPS      4000
                    Each mounting location is
                    compatible with both idle
     1.2,1.3,1.6,4. modules and driven motored
13          3       modules                               9    Binary    Yes    Yes
14         1.7      Speed Control                         3     m/s      0.2    0.1
15         1.8      Rechargeable energy source            9    Binary    Yes    Yes
     1.1,1.2,1.4,1. Battery max-payload run time at            Amp-
16      5,1.8,1.9 50-60% Duty Cycle                       9     Hour     50     100
17         1.8      Charging Time                         1     Hour      4      1
                    On board shut-down intelligence
18        1.10      and a fail-safe braking system        9    Binary    Yes    Yes
19        1.11      Brake distance (from top speed)       3      m        <5    <3.5
20        1.12      Turning radius                        3      m       <1.5    <1
21    1.1-1.5,1.12 Min Turning Angle                      3     Deg       20     40
                    Angular speed and rotation
22        1.13      detection                             9     rpm      35     15
                    Motor module must be able to
                    give feedback and receive
                    instructions from the central
23        1.14      processor                             9    Binary    Yes    Yes
                    Production Constraints
                    Must be open architecture, such
                    that it can facilitate future
24         2.1      additions                             9    Binary    Yes    Yes
                    Must be manufacturable in lots
25         2.2      as small as 1 and as large as 10      3    Binary    Yes    Yes
                    Must comply with federal, state,
                    and local laws and regulations
26         2.4      and RIT‟s policies and procedures     9    Binary    Yes    Yes
                    Document Requirements
                    Design documents must be open
27         3.1      source                                9    Binary    Yes    Yes
                    Must be designed such that other
                    SD teams have the option to
28         3.2      adapt the design in the future.       3    Binary    Yes    Yes
                    All documentation (when
                    applicable) must reference
                    federal, state, and local laws and
                    regulations as well as RIT‟s
29         3.3      policies and procedures.              9    Binary    Yes    Yes
                    Quality Control
                    The ultimate result of this project
                    must increase the reputation and
                    visibility of the RIT senior design
                    program and the robotics
30         4.1      technology “skill level” on a         1    Subj.     Yes    Yes


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                        national basis.

                        The robotic platform must be
                        clearly impressive to any
                        student, parent, engineer,
                        mentor, or individual familiar
                        with the US FIRST robotics
      31         4.2    competition.                              1    Subj.        Yes         Yes
                        The robot must be durable and
      32         4.3    have a long life                          3    Years         3           5
                        Compatibility
                        The processing platform of the
                        robot must be able to integrate
                        with project results of SD team
      33         5.1    projects P07301 and P07302.               9    Binary       Yes         Yes
                        The robotic platform must be
                        able to integrate with the SD
      34         5.2    P07203 results.                           9    Binary       Yes         Yes
129                                      Table V.ii - Specifications


130    VI.       Related Projects & Dependencies
131    P07302 – Controller: protocol must interface; instructions must correlate
132
133    P07203 – Dynamometer: Must be compatible
134
135    P07201 – 10 Kg Motor Module


136    VII.      Concept Generation and Selection
137

138    A. Mechanical
139    The motor module which we will be designing will consist of a mix between mechanical and
140    electrical components. The mechanical components will be explained in detail below. They
141    consist of four different subsystems which are the motor, braking, transmission, and
142    steering. All needed calculations are included as well as detailed explanations for all
143    decisions.
144
145    The subsystems will all have to be put together into one unit along with the addition of all
146    electrical components. Multiple architectures have been considered. The first would be to
147    have all mechanical components working in the same plane and having steering being
148    applied to only the wheel. Another idea is to have the steering move the whole module, not
149    just the wheel. The other option to save space or for other reasons would be to have the
150    system operating in two different planes; the output shaft of the motor would be 90 degrees
151    from the output of the transmission. Other combinations of the components will be looked
152    at after each subsystem has been broken down.
153
154    Mechanical information is as follows:
155                         A1 - Motor
156                         A2 - Transmission
157                         A3 - Brakes


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158                         A4 – Steering
159                         A5 – Risk Assessment
160                         A6 - Architectures

161   A1     Motor Concept Development
162   The motor will be the means of converting the voltage and current into a mechanical energy,
163   and ultimately result in torque and angular velocity of an output shaft. The motor will run on
164   DC as specified in the PRP.
165
166   Possible Concepts:
167
168   A1.i - Permanent Magnet Brushed
169   A2.ii - Permanent Magnet Brushless
170   A3.iii - Permanent Magnet Stepper
171   A4.iv - Servo
172   A5.v -RC Servo Kit
173

174   A1.i   PM Brushed
175   This is the motor that is typically used for this application.
176
177   Pros
178         High torque, low speed applications
179         Cheaper
180         Accurate/predictable
181         Smaller size for same output
182

183   A1.ii PM Brushless
184   Used for high speed applications requiring low speed deviations; quick and precise.
185
186   Pros
187         Better heat dissipation resulting in ability to run at higher continuous loads
188         Less maintenance, longer life
189         Quieter
190         Cleaner
191         Quicker Accel/Decel
192

193   A1.iii PM Stepper
194   Divides full rotation into certain number of steps.
195
196   Pros
197         Less maintenance, longer life
198         Optimum characteristics for resolution of speed/load
199         Accurate and has ability to rigidly stay in position
200         Easy to control
201
202   Cons:
203       Generates high heat at stand still
204       Open loop- no feedback
205       Non-continuous- not smooth

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206         Big and heavy
207         Larger power consumption
208

209   A1.iv Servo
210   Servos operate on the principle of negative feedback, where the control input is compared
211   to the actual position of the mechanical system as measured by some sort of transducer at
212   the output.
213
214   Pro:
215         Don‟t have to constantly attach and detach power source
216         Ability to go in reverse easily
217
218   Con:
219         Motor will slow with increased payload
220         Needs an encoder
221         Speed and current draw effected by payload
222         Complex circuitry
223

224   A1.v RC Servo
225   Same as servo, except comes in a kit that includes a gearbox, encoder, and control circuitry.
226
227   Pro:
228         Complete system including motor, gearbox and feedback device, servo control
229          circuitry, drive circuitry
230         Easily controlled
231         Low Voltage draw
232   Con:
233         No flexibility
234         No Modularity
235         No Scalability
236
237   Analysis:
238
239   Comparison with Baseline:
240   Baseline is PM Brushed but it is not be an efficient solution. While it is very inexpensive, it is
241   extremely heavy, is very big, and also requires over a 100 amps to operate. We have to
242   match our required motor output with the specific model we purchase.
243
244   Applicable Customer Needs:
245      Payload range- 10kg to 100kg w/ multiple configurations
246      Tare weight 40kg
247      Top speed of 4.5m/s
248      Controllable speed
249      Run time of 1 hour (power consumption)
250      Ability to read angular speed
251      Feedback
252      COTS
253      Durability of 5 + years
254      Cost
255


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256   Pugh Diagram:
                                                                                            Motor Concepts
                                                         A1.i                A2.ii              A3.iii                 A4.iv                A5.v
                                                     (reference)
                                                                       Brushless PM               Stepper              Servo             RC Servo
                                                    Brushed PM
                                                            Weighted            Weighted              Weighted             Weighted             Weighted
           Selection Criteria         Weight       Rating    Score     Rating    Score      Rating     Score     Rating     Score     Rating     Score

           Weight                      10%           3          0.3      3           0.3      1           0.1      3           0.3      2           0.2
           Operating Speed/Accel        5%           4          0.2      5           0.25     3           0.15     2           0.1      2           0.1
           Torque                      10%           5          0.5      4           0.4      4           0.4      3           0.3      3           0.3
           Controllability             10%           4          0.4      4           0.4      5           0.5      3           0.3      3           0.3
           Power Consumption            8%           3          0.24     3           0.24     1           0.08     5           0.4      5           0.4
           Feedback                     5%           1          0.05     5           0.25     5           0.25     1           0.05     5           0.25
           COTS                        10%           5          0.5      5           0.5      5           0.5      5           0.5      5           0.5
           Durability/Maintainence      5%           2          0.1      4           0.2      4           0.2      2           0.1      3           0.15
           Temperature                  5%           3          0.15     3           0.15     1           0.05     3           0.15     3           0.15
           Cost                        15%           4          0.6      2           0.3      1           0.15     4           0.6      2           0.3
           Modularity                   8%           3          0.24     3           0.24     1           0.08     3           0.24     2           0.16
           Size                         9%           3          0.27     2           0.18     1           0.09     4           0.36     4           0.36
                                     Total Score         3.55                3.41                  2.55                3.40                 3.17
                                          Rank              1                   2                    5                    3                    4
                                      Continue?          Yes                 Yes                     No                   No                   No
257
258
259   Conclusion:
260   The Pugh clearly shows that Brush and Brushless are the best solutions. They meet every
261   need to some degree, the big argument here is Maintenance versus cost. The small amount
262   of upkeep required for brushed motors is not a problem.
263
264   Additionally, brushed DC motors meet the calculated needs very well. Dr. Hensel also
265   mentioned the need for low production cost of the motor module. The final product will be a
266   Brushed PM Motor unless we can find no manufacturer to make something to match the
267   needs.
268
269   Manufacturers/Vendors:
270      Source Engineering, http://www.sei-automation.com/products.html
271      Globe, http://www.globe-motors.com/home.html
272      Mabuchi, http://www.mabuchi-motor.co.jp/en_US/index.html
273      Bodine, http://www.bodine-electric.com/
274      Leeson, http://www.leeson.com/products/stock_dcmotors.htm
275      Maxon Motors, http://www.maxonmotorusa.com
276      www.robotmarketplace.com
277      www.robotics.com
278
279   Calculations for PM Brushed Motors:
280




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                                                    MAXIMUM TORQUE REQUIREMENTS
      Weight                      140     kg         Driven Wheels Max Motor Torque (N-m)   Max Motor Torque (Oz-in) Max Motor Torque (in-lbs)
      MaxForce Friction (N)     27.32     N                1                1.93                      274                    17.07
      Max Force(N)             170.88 N                    2                0.96                      137                     8.54
      Max Wheel Torque (N-m)     8.68 N-m                  3                0.64                      91                      5.69
                                                           4                0.48                      68                      4.27
                                                           5                0.39                      55                      3.41
      max incline=                   6   deg               6                0.32                      46                      2.85
                                  0.10   rad
      veh. Velocity=                 3   m/s              T                   5             s                             Vf^2=V1^2+2AX
      coef. of rolling res.       0.02                    V1                  0             m/s                               Vf=Vi+at
      g=                          9.81   m/s^2            V2                  3             m/s
      Wheel diameter=          0.1016    m                a=                 0.6            m/s^2
      Gear Ratio=                    5
      Gear Efficiency=             0.9

      Wheel Shaft Speed=        563.9 rpm
      Motor Speed=             2819.7 rpm           MINIMUM TORQUE REQUIREMENTS
                                                     Driven Wheels Max Motor Torque (N-m)   Max Motor Torque (Oz-in) Max Motor Torque (in-lbs)
      Total Power=              512.6 W                    1                0.95                      135                     8.39
                                0.687 HP                   2                0.47                      67                      4.20
                                                           3                0.32                      45                      2.80
              F=ma                                         4                0.24                      34                      2.10
               F=                  84 N                    5                0.19                      27                      1.68
281      Max Wheel Torque=     4.2672 N*m                  6                0.16                      22                      1.40

282
283          *See section X for equations used in calculations.
284
285   Specific Model Possibilities:
286       Bodine Electric Model N4802
287       Dewalt 24v Hammerdrill Motor
288       Maxon F 2260, Winding 881
289       SEI Automation, Model ZY125-249-12
290
291




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292   A2      Transmission
293   The transmission for our motor module has a few characteristics that are important to its
294   use. The first is that it must have some sort of mechanical advantage, meaning that it has
295   to help us choose the most efficient motor.        Another key characteristic is that our
296   transmission must be small, light, and inexpensive. Also there are factors like noise,
297   maintenance, and assembly ease. All these characteristics will be discussed in further detail
298   and conclusions below.
299
300   Possible Concepts:
301
302   A2.i - V-belts
303   A2.ii - Synchronous Belts
304   A2.iii - Gears
305   A2.iv - Chains
306   A2.v - Direct drive
307

308   A2.i    V-Belts
309   This is the most popular type of belt used for transmissions. The v-shape causes the belt to
310   wedge tightly into the pulley which increases friction and allows for higher operating torque.
311   The belts contain tensile members which are the main load carrying elements. The rest of
312   the belt is made from an elastomer which transmits the load from the tensile fibers to the
313   flanges of the pulley. There is jacket/skin around the entire belt that protects the belt from
314   the environment.
315
316   There are three types of designs that v-belts consist of:
317    Narrow design: Narrower and lighter than the classic design for low power and high RPM.
318
319    COG design: This has grooves in the inner surface in order to increase belt flexibility,
320               allowing the belt to turn a smaller radii; thus it can be used with smaller
321               pulleys. This also increases the durability of the belt.
322
323    Multiple design: Several v-belts connected side by side. This increases the amount of
324                 power transferred.
325
326   These designs will be researched further if v-belts are chosen as the component of our
327   transmission. Here is the breakdown of advantages and disadvantages to v-belts:
328
329   Pros:
330          Smooth
331          Quiet
332          Inexpensive
333          Ease of assembly
334          No lubrication
335
336   Cons:
337          Creep
338          Not good for high temp
339          Low torque only
340          Slip
341          70-96% efficiency


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342          ± 3% speed
343          Rely on friction to transmit power
344
345   It is easy to see here that this belt is no good because of the efficiency range that we get
346   and that it is prone to creep. It also does not transmit speed perfectly and there will be slip.
347   But on the other hand there is no lubrication, it is quiet, and very inexpensive.
348

349   A2.ii Synchronous Belts
350   These belts are used where input and output shafts must be synchronized. They combine
351   the advantages of flat belts with the positive grip features of gears and chains. These belts
352   do not rely on friction to transmit power so they have a high efficiency. The belts are made
353   of an elastomer but are reinforced with glass or aramid fibers. This allows for maximum
354   performance and gets rid of slipping and creep. Synchronous belts require low belt tension
355   so there is much less load on the bearings that support the sheaves and shafts. There are
356   two general designs of synchronous belts which are the standard design (trapezoidal teeth)
357   and the HTD design (curvilinear teeth.) The HTD design is usually used for high torque
358   applications. The synchronous belt has many pros and some cons about it, they are:
359
360   Pros:
361          98% efficiency
362          Input/output shafts synchronized
363          Do not rely on friction to transmit power
364          Less slip and creep
365          Low belt tension
366
367   Cons:
368       Not good for high temp
369
370   It seems here that the synchronous belt is really the choice to go with over the two belts,
371   but we need to compare it to some other systems. It is very efficient and reasonable
372   inexpensive. But it is not good for high temperatures because it is made of an elastomer.
373   This belt does not require any lubrication and its operation is quiet.
374

375   A2.iii Gears
376   Gears are used to transmit power between rotating shafts at different speeds and high
377   torques. They offer perfect synchronization. There are many different types of gears:
378
379    Spur gears:    These gears have straight teeth parallel to the axis of rotation.     They are
380                  easy to manufacture and cheap.
381
382    Helical gears: Have teeth inclined at an angle with respect to the axis of rotation. This
383                 angle is termed the helix angle and is usually at 45 degrees. This angle
384                 provides a more gradual engagement of the teeth during meshing and
385                 produces less impact and noise. This smooth operation makes them good
386                 candidates for high speed applications, but because of the helix angle, thrust
387                 forces are produced.
388
389    Herringbone gears: Has two opposite-hand helical gears butted against each other with
390               the purpose of counterbalancing the thrust forces.
391


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392    Bevel gear:    Have teeth formed on a conical surface and are used to transmit motion
393                  between non parallel shafts. Used for reducing speed.
394
395    Worm gear:      Used to transmit motion between nonparallel shafts.     Very efficient when
396                  higher ratios are necessary.
397
398   Each of these specific designs have valid reasons to their benefits but we are going to break
399   down the good and bad of these gears as a whole:
400
401                  Pros:
402                         Small packaging size
403                         Handles high torques
404                         98-99% operating efficiency
405                         Perfect synchronization
406                         Can orient input and output in different planes
407
408                  Cons:
409                      Needs lubrication
410                      Center distance is not flexible
411                      High cost
412
413   Gears give us the highest operating efficiencies as well as the smallest packaging size
414   capabilities. They offer perfect synchronization and they can orient the input and output
415   shafts in different planes. The key player here is that we can orient the input and output
416   shafts to the transmission in different planes. The problems with gears are that the center
417   distance is fixed, they need lubrication, and they are expensive.
418

419   A2.iv Chains
420   Chains transmit power through interlocking links wrapping on a sprocket. These drives are
421   less expensive than gears and they can transmit high loads. They have a long service life
422   and are not effected by temperature. Here are some types of chains:
423
424    Roller chain: The most common chain. It has pins that pivot inside a roller bushing.
425
426    Inverted tooth chain: Use in applications for high speed, smooth, and quiet operation is
427                required. Expensive.
428
429   Looks like our project would use the inexpensive common (roller) chain.         It has some
430   advantages and disadvantages:
431
432                  Pros:
433                         Less expensive than gears
434                         Transmit high torque
435                         No slippage
436                         98% efficiency
437                         Long service life
438                         No temperature limits
439                         Do not require initial tension
440
441                  Cons:
442                      Fatigue
443                      Noise

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444                                 Lubrication
445
446   Chains look like a good choice because they are cheaper than gears, transmit high torque,
447   have long life, and there is no initial tension required making for easy installation. But the
448   problem is that there will be fatigue in the chain along with noise and lubrication issues.
449

450   A2.v Direct Drive (no transmission)
451   The idea of a direct drive was looked into because maybe there was no need for a
452   transmission. This is not the most efficient idea since there will be no mechanical
453   advantage but maybe we don‟t need that advantage. The pros to this system are that there
454   is not transmission which makes it very inexpensive and efficient. The only con to the idea
455   is that there is no mechanical advantage. This factor alone rules out the idea of direct drive.
456
457   Pugh Diagram:
                                                                                 Transmission Concepts
                                                      A2.i                A2.ii          A2.iii                    A2.iv               A2.v
                                                                                      (reference)
                                                      V-belt          Sync. Belt                                   Chain          Direct Drive
                                                                                         Gears
                                                         Weighted            Weighted             Weighted            Weighted            Weighted
           Selection Criteria         Weight     Rating   Score     Rating    Score      Rating    Score     Rating    Score     Rating    Score
           Out of Plane Flex.            5%        1       0.05       1           0.05     5       0.25        1       0.05        1          0.05
           In Plane Flex.               10%        5       0.5        5           0.5      2       0.2         5       0.5         1          0.1
           Weight                        5%        4       0.2        4           0.2      2       0.1         3       0.15        5          0.25
           Efficiency                    8%        1       0.08       4           0.32     4       0.32        4       0.32        5          0.4
           Modularity                    5%
           Scalability                   5%        4       0.2        4        0.2         4        0.2        4        0.2        5       0.25
           COTS                         12%        5       0.6        5        0.6         5        0.6        5        0.6        5        0.6
           Durability/Maintainence       8%        3       0.24       4       0.32         3       0.24        3       0.24        5        0.4
           Cost                         15%        5       0.75       5       0.75         3       0.45        4        0.6        5       0.75
           Size                         10%        4       0.4        4        0.4         3        0.3        4        0.4        5        0.5
           Noise                         2%        5       0.1        5        0.1         3       0.06        2       0.04        5        0.1
           Torque Transfer               8%        2       0.16       5        0.4         5        0.4        5        0.4        5        0.4
           Mech. Adv.                    5%        5       0.25       5       0.25         5       0.25        5       0.25        1       0.05
           Temperature                   2%        2       0.04       3       0.06         5        0.1        5        0.1        5        0.1
                                     Total Score 3.57                     4.15                 3.47                3.85                3.95
                                           Rank    5                       1                    4                    2                  3
                                      Continue?         No                Yes                  Yes                  No                 Yes
458

459   This diagram shows us how our concepts performed when placed against the others
460   according to customer needs. The top three are the synchronous belt, the chain, and the
461   direct drive. We don‟t want to look at chains due to its low ranking on noise and
462   maintenance and we don‟t want v-belts due to there very low efficiency. The gears are
463   chosen over the chain because they offer the unique characteristic of out of plane flex, when
464   none of the others do.
465
466   Analysis:
467
468   Comparison with Baseline:
469   It seems that the timing belt option would be the lightest, easiest to assemble, cheap, and
470   efficient option that we have. They seem to have the highest amount of pros and the
471   lowest amount of cons. We just need to see how it fits into our customer needs and if it will
472   transfer over to the 10 kg and 1000 kg models. It exceeds most of the qualities of our
473   baseline of drive gears, but the baseline offers easy combinations of one or two motors and
474   I am not sure if that changeover is so easy with timing belts.
475


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476   Applicable Customer Needs:
477      Payload range- 10kg to 100kg w/ multiple configurations
478      Tare weight 40kg
479      Top speed of 4.5m/s
480      COTS
481      Durability of 5 + years
482      Cost
483
484   Conclusion:
485   The baseline gears seem to be a good option because of the variety of gearing ratios
486   available when using gears. But the problem of lubrication and noise is not the best thing
487   to have. The transmission may have to be enclosed in order to keep dirt and debris out of
488   the gearing. The gear drive is the only option that allows for the input and output shafts to
489   be in different planes. The chain drive is a good option because of its flexibility and that it
490   does not have any initial tension on it. The lubrication and noise issues are not very
491   desirable. The V-belts are great because they are very common but they are not really
492   efficient at all. That leaves us with the timing belt which seems to have the greatest
493   qualities. It has all of the qualities of the chain and gear drives plus it is quiet, requires no
494   lubrication, and it is lightweight compared to those. Also this choice is supported by the
495   Pugh diagram which is based on our customer needs. The timing belt will be the option if
496   we can stay in one plane because it meets our customer requirements the best of all the
497   choices.
498
499   Companies/Manufacturers:
500      Dodge-PT, http://www.dodge-pt.com/index.html
501      Boston Gear, http://www.bostongear.com/
502      Goodyear, http://www.goodyearindustrialproducts.com/powertransmission/
503      Emerson Power Transmission, http://www.emerson-ept.com/
504




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505   A3      Braking Subsystem
506   The braking subsystem will be responsible for stopping the rotary shaft motion of the
507   module. Through an input voltage and current the system will utilize one or several means
508   of stopping the wheel from spinning.
509
510   Possible Concepts:
511   A3.i - Dynamic Braking
512   A3.ii - Power-off Mechanical Spring
513   A3.iii - Motor Shorting
514   A3.iv - Via Speed Controller
515   A3.v - Combination
516   A3.vi - Automotive Style Disc Brakes
517   A3.vii - Automotive Style Drum Brakes
518

519   A3.i    Dynamic Braking
520   Dynamic Braking requires a switching device, resistor and circuit. It detects differences in
521   motor speed and desired speed to convert mechanical energy to electrical energy that can
522   be used as utility power.
523
524   Pros:
525          Simple design
526          Reduced power consumption due to regenerative property
527          Cheap $5-$35
528          Smooth operation
529          Good for regular deceleration
530
531   Cons:
532       Low output torques-rule of thumb-stopping distance=accel distance (dependant on
533         motor)
534       Will not work without power (emergencies)
535       Dependant on load and motor used
536       High motor temperatures
537       Custom H-bridge required
538

539   A3.ii Power-off spring
540   A spring actuated disc brake is released when power is on, when the power is cut the brake
541   is applied.
542
543   Pros:
544          Safety consideration for power cut-off
545          High output torques
546          Doesn‟t effect motor
547          Very scalable
548
549   Cons:
550          More expensive
551          Heavier
552          Not necessarily smooth
553          Always consuming power

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554         Mounting hardware required
555         More space
556

557   A3.iii Motor Shorting
558   The motor is short circuited, causing it to generate an opposing magnetic field. This greatly
559   increases the motor‟s resistance.
560
561
562
563
564
565
566
567
568
569
570   Figure 1: Possible Motor Shorting Circuit
571
572   Pros:
573       No more major parts added
574           o Light weight
575           o Cheap <$10
576       Simple design
577
578   Cons:
579       Low output torques
580       Will not work without power
581       Difficult to predict analytically
582

583   A3.iv Using Speed Controller
584   Some Speed controllers come with a Brake/Coast feature that would ultimately act as a
585   motor shorting technique. See Motor Shorting for Pros/Cons.
586

587   A3.v Combination
588   By combining the use of the power-off brakes with either dynamic braking or short circuiting
589   there may be a considerable gain in advantages.
590
591   Pros:
592       Reduce the size required for Power-off brakes, thus price and weight
593       Greater braking torque
594       Fail Safe
595
596   Cons:
597       More complex
598       Harder to characterize
599

600   A3.vi Automotive Style Disc Brakes
601   A power-on mechanical brake used in most modern cars.

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602
603   Pros:
604       High output torque
605       Easy to find manufacturers
606
607   Cons:
608       Won‟t work if power is cut
609       Too heavy
610       Too complex
611

612   A3.vii Automotive Style Drum Brakes
613   A cheaper power-on mechanical brake found in most older cars.
614
615   Pros:
616       Relatively cheap
617
618   Cons:
619       Low output torque
620       Too heavy
621       Won‟t work if power is cut
622
623   Analysis:
624
625   Comparison with baseline:
626      No mechanical braking system provided
627      Short Circuit and Characterize Motor
628      Utilize Victor Speed Controller to characterize braking capabilities
629
630   Applicable Customer Needs:
631      Fail-safe braking
632      Durability for 5 years
633      COTS Item
634      Run time of 1 hour (power)
635      Controllable speed
636      Tare weight of 40kg
637      Brake within 1m
638      Cost
639      Scalable
640
641   Pugh Diagram:




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                                                                                        Braking Concepts
                                                       A3.i               A3.ii               A3.iii              A3.v
                                                   (reference)
                                                                      Power-Off           Short Circuit           Combo
                                                    Dynamic
                                                         Weighted            Weighted            Weighted            Weighted
           Selection Criteria         Weight     Rating   Score     Rating    Score     Rating    Score     Rating    Score
           Fail-Safe                   20%         1        0.2       5         1          1        0.2       5          1
           Weight                       5%         4        0.2       2        0.1         5       0.25       2         0.1
           Braking Torque              18%         3       0.54       5        0.9         3       0.54       5         0.9
           Modularity                   7%         5       0.35       3       0.21         5       0.35       4        0.28
           Controllability              5%         5       0.25       3       0.15         3       0.15       5        0.25
           Power Consumption            5%         3       0.15       4        0.2         4        0.2       3        0.15
           Scalability                  8%         4       0.32       5        0.4         4       0.32       5         0.4
           COTS                        12%         4       0.48       4       0.48         4       0.48       4        0.48
           Durability/Maintainence      3%         5       0.15       4       0.12         5       0.15       4        0.12
           Cost                        13%         4       0.52       2       0.26         5       0.65       2        0.26
           Size                         4%         4       0.16       2       0.08         5        0.2       2        0.08
                                     Total Score       3.32               3.90                 3.49                4.02
                                           Rank          4                  2                    3                   1
                                      Continue?         No                Yes                   No                 Yes
642
643
644   Conclusion:
645   Combination is the best solution due to the fail-safe requirement as well as the large cost of
646   fail-safe mechanical brakes.
647
648   The solution is to combine Dynamic Braking (because of its predictability and controllability
649   over short circuiting) with the safety of Power-off mechanical braking. Additionally we will
650   consider utilizing regenerative braking with the Dynamic Braking over an H-Bridge. A
651   possible circuit to accomplish this is shown below.
652




653
654   Figure 2: Possible Regenerative Braking Circuit
655
656   Manufacturers/Vendors:
657      MC Supply Co., http://www.mcsupplyco.com
658      Acroname, http://www.acroname.com/index.html
659      Texas Instruments, http://www.ti.com
660      Ogura Industrial, http://ogura-clutch.com
661      See Controllers for additional Dynamic Braking products
662
663   Calculations:
664




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      Power Off (torque input)                                 Dynamic Brakes (torque input)                    Combined (torque input)
      Wheel rad                               0.0508   m       Motor Power                         80   W       Brake torque=Wheel torque=    11.37957   N-m
      Static Torque=                            5.65   N-m     Motor Efficiency                   0.7           Wheel force                   224.0073   N
      Brake torque=Wheel torque=              5.2545   N-m     Voltage During Braking              12   Volts   # braking wheels=                    2
      Wheel force                            103.435   N       Motor Speed                      2740    RPM     Total braking force=          448.0147   N
      # braking wheels=                            2           Dynamic Resistor Current        0.351    Amps    veh. Mass=                         140   kg
      Total braking force=                  206.8701   N       Resistance                        0.38   Ohms    deceleration=                 3.200105   m/s^2
      veh. Mass=                                 140   kg      Braking Power                  377.95    W       velocity                             3   m/s
      deceleration=                         1.477643   m/s^2   Braking Torque                    1.32   N-m     Stopping distance=            1.406204   m
      velocity                                     3   m/s     Wheel torque                 6.125073    N-m
      Stopping distance=                     3.04539   m       Wheel force                  120.5723    N
      GR=                                          5           # braking wheels=                    2
      W/ Decline                                               Total braking force=         241.1446    N
      Weight effect-                        14.35594   N       veh. Mass=                        140    kg
      Overall Force-                        192.5141   N       deceleration=                1.722462    m/s^2
      deceleration=                         1.375101   m/s^2   velocity                             3   m/s
      velocity                                     3   m/s     Stopping distance=            2.61254    m
      Stopping distance=                    3.272487   m


      Overall system (deceleration input)                      Overall system w/ Incline                        Affects on Inertia (add. Torque requirement)
      d=Vi^2/2a                                                Ftotal=                           420    N
      Vi=                   3 m/s                              max incline=                        6    deg     I=1/2 mr^2
      a=                    3 m/s^2                                                             0.10    rad     Wheel mass=                       0.33   kg
      d=                  1.5 m                                Fweight=                     143.5594    N       Wheel radius=                   0.0508   m
                                                               Fbraking=                    563.5594    N       Wheel inertia=                0.000426   kg*m^2
      F=ma                420 N                                F per wheel=                 281.7797    N       Motor inertia=                    1.29   kg*m^2
      F per wheel=        210 N                                T per wheel=                 14.31441    N*m     Pulley 1 mass=
      T=F*r            10.668 N*m                                                                               Pulley 1 radius=
                                                                                                                Pulley 1 inertia=
                                                                                                                Pulley 2 mass=
                                                                                                                Pulley 2 radius=
                                                                                                                Pulley 2 inertia=
                                                                                                                Transmission inertia=
                                                                                                                Total system inertia=         1.290426 kg*m^2
                                                                                                                alpha=                               4 rad/s^2
665                                                                                                             I*alpha=                     5.161703 N*m

666
667        *See section X.1 for equations used in calculations.
668

669   A4         Steering Concept Development
670   The steering system will be responsible for outputting a torque capable of rotating the
671   vehicle platform. It will convert a voltage and current into mechanical energy.
672
673   Possible Concepts:
674
675   A4.i - Skid
676   A4.ii - Center of wheel turning on-axis
677   A4.iii - Module turning off-axis
678   A4.iv - Pneumatic
679

680   A4.i       Skid
681   Skid steering utilizes forward and reverse motions of individual wheels to control steering.
682   There is our choice of reference system.
683




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684
685                                       Figure 3: Skid Steering
686   Pros:
687          Infinite Turning radius
688          Minimal additional weight
689          Ease of control/ Accuracy
690          Durable
691
692   Cons:
693          Not very smooth
694          Low dynamic usage
695          Non-main stream components
696          Does not meet all wheel configurations
697

698   A4.ii Center of wheel turning on-axis
699   Single wheel turns with aid of Motor (servo)
700




701

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702                             Figure 4: Center of wheel turning on-axis
703   Pros:
704          Low power consumption
705          Easily Scalable
706          Compatible in all wheel configurations
707          Smoother than skid
708          Smaller and lighter than pneumatic
709          Lower Torque requirement
710          Larger range of individual turning angles
711
712   Cons:
713       Higher cost
714       Additional hardware
715       Additional tare weight
716

717   A4.iii Module turning off-axis
718   Suspension and wheel turns with aid of servo, on different axis than wheel servo.




719
720                                  Figure 5: Module turning off-axis
721
722   Pros:
723          Low power consumption
724          Easily Scalable
725          Compatible in all wheel configurations
726          Smoother than skid
727          Single attachment of suspension and steering motor
728
729   Cons:
730          Higher cost
731          Higher Torque requirements than turning on-axis
732          Smaller range of turning individual angles
733          Additional hardware
734          Additional tare weight
735



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736   A4.iv Pneumatic
737   Utilization of pressurized gas to control steering.
738
739   Pros:
740       Easily scalable
741       Operates in all configurations
742       Large Torque available
743
744   Cons:
745       High additional tare weight
746       Lower efficiency than dc servo
747       Continuous drain on battery to maintain pressure
748
749
750
751
752   Analysis:
753   The steering motor will need to overcome the following frictional force during operation in
754   order to turn the wheels:
755
                              s  0.6
      Ff  s (N )
                             PL  Payload  10  100kg
756   WTare  40kg (max)
                              n  Number of wheels  3  6
                     PL
      N  (WTare       ) * g g  9.8 m s
                     n
757
758   Testing the 3-6 wheel configurations with the max pay load and tare weight:
759
                                          Number of Wheels
                                      3         4        5        6
      Normal Force (N)            719.4    637.65    588.6    555.9
      Frictional Force (N)       431.64    382.59   353.16   333.54
760
761
762   Comparison with Baseline:
763
764   There is no baseline system provided since the model provided is not capable of steering.
765   We looked at skid steering as our reference.
766
767   Applicable Customer Needs:
768
769         Tare weight 40kg
770         Run time of 1 hour (power consumption)
771         Ability to read angular speed
772         Feedback
773         COTS
774         Durability of 5 + years
775         Cost
776
777


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778   Pugh Diagram:
                                                                                    Steering Concepts
                                                              A4.i                A4.ii           A4.iii                 A4.iv
                                                          (reference)             Motor           Motor
                                                                                                                     Pneumatic
                                                              Skid               On-Axis         Off-Axis
                                                                Weighted            Weighted            Weighted            Weighted
           Selection Criteria                Weight     Rating   Score     Rating    Score     Rating    Score     Rating    Score
           Smoothness                          9%         1       0.05       3        0.15       3       0.15        3       0.15
           Weight                              4%         5       0.75       4         0.6       4        0.6        1       0.15
           Turning Radius                      7%         5       0.25       4         0.2       3       0.15        2        0.1
           Controllability/Accuracy            7%         5        0.5       3         0.3       3        0.3        2        0.2
           Power Consumption                   7%         2        0.1       4         0.2       3       0.15        1       0.05
           Scalability                         5%         4        0.6       5        0.75       5       0.75        5       0.75
           COTS                                9%         4        0.4       4         0.4       3        0.3        5        0.5
           Durability/Maintainence             5%         4        0.2       4         0.2       4        0.2        3       0.15
           Cost                               12%         4        0.4       3         0.3       3        0.3        2        0.2
           Operation in different configs     20%         1       0.02       5         0.1       5        0.1        5        0.1
           Dynamic Usage                       7%         1        0.1       4         0.4       3        0.3        3        0.3
           Modularity                          4%         2       0.12       4        0.24       4       0.24        4       0.24
           Size                                4%         5        0.1       4        0.08       4       0.08        2       0.04
                                            Total Score       3.59                3.92               3.62                2.93
                                                  Rank          2                   1                  3                   4
                                             Continue?         No                 Yes                 No                  No
779
780
781   Conclusion:
782   Center of wheel turning on-axis is the most efficient choice for our application. This model
783   will have less power consumption due to lower torque requirements than off-axis steering,
784   and has ability to meet all customer requirements such as multiple wheel configurations.
785   Skid steering would allow for a large range of motion and minimal additional components
786   but is not compatible in 3 wheel design.
787
788
789   Companies/Manufacturers:
790      www.memagazine.org
791      www.robotmarketplace.com
792      www.robotics.com
793




                                                              27 of 84
                                                              P07202
794   Risk Assessment
795   In regards to mechanical systems for the 100kg motor module robot, it is of the utmost
796   importance to carefully consider the customer needs and specifications within the confines
797   of what is practical and attainable. Many risks surface through the speeds, sizes, and costs
798   necessary to satisfy these specifications. While these risks are outlined below, the mitigation
799   and management of these risks are shown in section X.
800
801   Torque output capable of climbing the max incline
802   Torque and power considerations of the motor is essential, especially when considering the
803   maximum incline the robot will be required to climb. While it is simply a careful calculation
804   that will ultimately eliminate this risk, service factors and efficiency must be monitored
805   closely in calculating the correct specifications. From this the best solution (considering cost,
806   weight, torque, speed, power, and other specifications) must be chosen from the available
807   consumer market.
808
809   Braking safely (minimum distance and fail-safe aspects)
810   Braking is the highest risk from the mechanical aspect. This is because safety is the largest
811   concern of the P07202 project. Like torque calculations, braking calculations must be
812   carefully made under several conditions, including maximum decline and power failure. It is
813   important to protect people first, and then the building and its equipment second. The
814   safety of the vehicle is regarded well behind these previously mentioned entities.
815
816   Packaging in small, modular space
817   As modularity and compatibility are essential to the success of not only our project, but our
818   group as a whole, the packaging size becomes an increased risk. In considering the module
819   packaging, it is essential to not only select the smallest and lightest components which can
820   adequately satisfy our specifications, but to select such components that are compatible
821   with one another in regards to the overall packaging.
822
823   Drivetrain Failure (static and fatigue)
824   The high torques and operating speeds associated with the motor of this module will make
825   drivetrain failure a considerable problem. These previously mentioned specifications require
826   careful analysis of both static stresses and fatigue stresses experienced by components such
827   as the axle and transmission.
828
829   Steering Failure (static, fatigue, and torque)
830   Similar to drivetrain failure, but even greater a risk is steering failure. The transmission
831   amplifies torque through mechanical advantage. The steering system may be more likely to
832   experience a mechanical failure because of this. Additionally, the steering system is more
833   complex due to an additional steering motor, as well as universal joint and axle connection.
834
835
836   Moving the Robot with power off
837   One key risk that arose in considering the consequences of a mechanical power-off brake is
838   wheel lock experienced during the “off” mode. During this mode the brake will be locked on
839   and thus the robot will not roll freely. While some power-off brakes come with a manual
840   release, nearly all of these models are either too costly or do not accommodate the braking
841   specifications. It is from this that the consideration for alternative methods of detaching the
842   motor and transmission from the wheel has been explored. Among feasible solutions is that
843   of the power-on clutch and simply disconnecting the shaft in such a way that the wheel
844   would rotate freely.
845
846   Characterize motor in timely fashion

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                                                  P07202
847   The risk of characterizing the baseline has become more of an issue as of late. With
848   difficulties in locating an on campus dynamometer capable of handling the motor
849   specifications, this item has been pushed further along the project schedule. Valuable
850   specifications can be gained from this characterization, in addition to the testing of various
851   unknown set-ups including short-circuit braking.
852
853   Weight (impact on torque requirement)
854   The increase of weight of various components of the system, or the system as a whole has
855   considerable adverse affects on the motor module. Among the key concerns is the weight‟s
856   impact on robot performance, specifically braking, accelerating and steering.
857
858   Motor Temperature
859   The final mechanical risk is motor temperature. Limitations in space surrounding the motor
860   and circulation, consumed power, as well as energy lost from friction will all add to the
861   overall temperature of the system. This heat can have an adverse affect on motor
862   performance and operator safety should it reach certain temperatures. This must be
863   carefully monitored, and in the event that it becomes an issue, must be eliminated through
864   the use of increased convection and conduction.
865




                                                29 of 84
                                                P07202
866   A5         Overall Mechanical Architectures
867

                                                            Current                                                  Current                    Current

                                                                         Rotary Motion
                                                                          Stopped or               Stepped Down                                                 Stepped down rotary
       Current                            Rotary Motion                    Engaged                     Speed                    Rotary Motion                   motion that can stop
                        Motor                               Brake                        Tranny                      Steering                   Wheel
                                                                                                                                                                and go in any chosen
                                                                                                                                                                direction


                  RPM, temp, etc.                                                                                    Position            Slip, Speed, etc.


868   This architecture shows the brake before the transmission and the steering connected
869   directly to the wheel. This setup is advantageous because the brake will have less torque to
870   stop in this format
871
                                                                                         Current                     Current                    Current

                                                                                                   Rotary Motion
                                                                        Stepped Down                Stopped or                                                  Stepped down rotary
       Current                            Rotary Motion                     Speed                    Engaged                    Rotary Motion                   motion that can stop
                        Motor                               Tranny                       Brake                       Steering                   Wheel
                                                                                                                                                                and go in any chosen
                                                                                                                                                                direction


                  RPM, temp, etc.                                                                                    Position            Slip, Speed, etc.


872   This format puts the brake after the transmission. This may be the best way to organize
873   the size and layout of the module regardless of whether or not is advantageous to the brake.

                                              Variable rotary
                                                                                                    Current                          Current           874
                                              motion                                                                                                875
                                              controlled by
                                                                                 Stepped Down                                                                 Stepped down rotary
                                              the motor input
       Current                                                                       Speed                         Rotary Motion     Wheel                    motion that can stop
                            Motor                                     Tranny                        Steering
                                                                                                                                                              and go in any chosen
                                                                                                                                                              direction
                                                                                                                                                             876
                     RPM, temp, etc.                                                                Position                    Slip, Speed, etc.

877
878   The above architecture is a representation what we would have without a brake, using the
879   motor to brake. It is a nice setup because it is a smaller package size and less items to
880   monitor and program.

                                                  Current                                Current                                                Current
                            Multi
                            directional                                                            Rotary Motion
                                                                                                                                                                Motor module that has
                            motor                                                                   Stopped or                  Stepped Down
                                                                                                                                                                 stepped down rotary
       Current              module                                       Rotary Motion               Engaged                        Speed
                 Steering                          Motor                                 Brake                       Tranny                     Wheel            motion and can stop
                                                                                                                                                                and go in any chosen
                                                                                                                                                                      direction


                 Position                     RPM, temp, etc.                                                                            Slip, Speed, etc.



881   The final architecture discussed has the entire module being steered. This option came up
882   when looking at steering options and it seems that instead of steering the wheels we have
883   the ability to steer the whole module. Everything will be fixed to the module but the entire
884   module will rotate when needed.
885

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                                                                                     P07202
886   B. Electrical
887   The following documentation will address the power and controls design concepts that were
888   conceived in order to meet the design specifications of our customer needs. The Power
889   concepts design took into consideration the different components that need to be driven
890   within our motor module. In general, the breakdown of power consumption will be the
891   motor itself and the control circuitry that will be regulating its functions. The scale of the
892   robot and its weight parameters were a large influence in terms of power consumption. The
893   percent power output and battery life was also factored into our considerations for power
894   consumption and power loss in an overall sense. From a broad-spectrum, the power
895   required to drive the motors will be on the magnitude of 75 Amp hours, while the control
896   circuitry should concurrently be designed to handle such high loads of current. The
897   subsequent documentation will give a more detailed insight into the design considerations of
898   our project.
899
900   The Control systems design concepts were developed based on the customer desired
901   features in the sense that the system that will be designed, when implemented will provide
902   complex control signals and applications from a simple interface for any user to operate
903   without prior experience. Initially, the high power consumption of the motor was taken into
904   consideration in terms of tolerances and heat build up within the control circuitry.
905   Subsequently, proper feedback designs by using various circuit elements were considered
906   for reading information back to the user and protection to the control circuits from “worst
907   case scenarios” current build up within the circuitry due to controlled or unforeseen system
908   disturbances (i.e. interrupts). The architecture considered for our design was based on a
909   linear system, in that the microprocessor will drive the motor module and its various
910   features of breaking, steering, and a speed encoder to feedback information to the
911   microprocessor to measure its speed and displacement. The custom circuitry built will drive
912   the output signals from the microprocessor to ensure a smooth operation of the robot.
913
914   The subsystem decomposition of our design concepts will be presented as follows in the
915   subsequent pages of this documentation:
916      B.1) Controllers Concept Comparison
917      B.2) Control Circuits
918      B.3) Power Sub-Systems
919      B.4) Power System
920      B.5) Proof of Concept
921

922   B1     Controllers Concept Comparison
923   Investigating and comparing different options for parts and processes stemming from the
924   Refined Control System Architecture flowchart document will be the primary objective for
925   this document. Different architectures will be investigated and potential parts will be
926   compared.
927
928   The goal is to determine the most feasible motor control module of this project. The
929   systems investigated below will receive external power from the system batteries and
930   commands from the microprocessor over the system bus. From here the control system will
931   eventually take these inputs and correctly power the wheel. In accordance with the P07202
932   readiness package specifications the system should: supply enough current to drive 100kg
933   load at a speed of 4.5 m/s, use the power available for a 1 hour steady-state run time,
934   determine the angular speed of the drive shaft, and be easily modifiable in the future.
935


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                                                P07202
936   Motor control Concepts:
937   Currently, the most commonly used option for control of the motor is to use an H-bridge,
938   which will be controlled by a pulse-width-modulated wave. This basic concept can have two
939   different architectures. First, the PWM wave can come directly from the microprocessor
940   (given the processor is capable). This concept would then have circuitry before the H-bridge
941   to ensure proper duty cycles and to eliminate transient spikes. This concept is shown below
942   in Figure 1, concept B1.i. Another concept would be to have an external PWM source
943   controlled by more basic commands from the micro processor. This second scenario is
944   shown below in Figure 2, concept B1.ii. A third choice would be to simply purchase a motor
945   controller which has the capability of controlling everything in one package. This
946   configuration is shown below in Figure 3, concept B1.iii.
947
948                         Figure 1(concept B1.i): Processor controlled PWM
                                                                                Micro Processor
                                                     External Filtering
                   Motor         H-Bridge                                         PWM_OUT
                                                         Circuitry


949
950
951                               Figure 2(concept B1.ii): External PWM

                                                       Pulse Width
                   Motor         H-Bridge                                       Micro Processor
                                                        Modulator

952
953
954                              Figure 3(concept B1.iii): Motor Controller

                                                 Motor
                   Motor                                                        Micro Processor
                                                Controller

955
956
957   These three different architectures each offer a wide variation of pros and cons. These
958   factors are listed below.
959
960

961   B1.i   Concept Architecture:
962   Pros
963             Users have control over system refinement as the project progresses
964             Least expensive option (assuming the same processor for each case)
965             Products used will most easily be found and definitely acceptable COTS
966             Should result in less power connections
967   Cons
968             Might prove difficult to implement with bus delays
969             Signal lines travel susceptible to noise and physical strain
970

971   B1.ii Figure 2 Architecture:
972   Pros
973             More impervious to noise
974             All components can be interfaced on one board
975             Reduces workload of processor; hence, provides faster overall system response


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                                                  P07202
 976                Easily programmable
 977   Cons
 978                Might be excessive
 979                Difficult to synchronize with microprocessor
 980                Additional electronic design
 981

 982   B1.iii Figure 3 Architecture:
 983   Pros
 984                Least I/O lines
 985                Most reliable
 986                Easily configurable
 987                Almost completely impervious to noise
 988   Cons
 989                Least room customization
 990                Compatibility with microprocessor
 991                Most costly scenario
 992                Might be difficult to find a suitable COTS device
 993
 994
 995
 996
 997
 998                                          Table B1.1: Possible devices
                         Product               Input        Continuous                Bi-                PWM
       Company           Description           Voltage      current          Price    directional        Freq
       National          H-Bridge              12 to 55        3 Amps         $8.50   Yes                n/a
       Texas Inst.       H-Bridge              0 to 33         3 Amps         $5.18   Yes                n/a
       Freescale         H-Bridge              5 to 40         5 Amps         $6.77   Yes                n/a
       Parallax          Motor Controller      6 to 16         25 Amps       $49.95   Yes                9.2kHz
       Critical
       Velocity          PWM Controller        5.5 to 36       15 Amps       $49.95   No                 200 Hz
       National          Motor Controller      0 to 7          N/A           $33.60   No                 8kHz
 999
1000   Given these devices and architectures there are many new considerations. The practicality
1001   of each setup will be reviewed with the group for input and approval.
1002
1003                                      Table B1.2: Concept Pugh Diagram
                                                                       Concept
                                                        A                 B                         C
          Selection Criteria           Weight    Rating   Weight   Rating   Weight      Rating          Weight
        Hardware Connections            10%        4        0.4      2        0.2         3               0.3
         Software Interfacing           15%        4        0.6      2        0.3         3              0.45
         Max Operating Temp              5%        3       0.15      3       0.15         4               0.2
         Programmable Ease              15%        3       0.45      2        0.3         4               0.6
            Noise Immunity              10%        2        0.2      3        0.3         4               0.4
        System Response Time            10%        3        0.3      3        0.3         5               0.5
          System Refinement
                 Ease                   15%         4          0.6       2     0.3          3            0.45
                 Cost                   10%         4          0.4       3     0.3          3             0.3


                                                           33 of 84
                                                           P07202
            Open Source           10%         5          0.5      4          0.4        2           0.2
                                  Total
                                  score           3.35                2.55                    3.4
                                  Rank              2                   3                      1
                                Continue?          No                  No                     Yes
1004
1005   Since the initial conception of this document the concepts outlined above have been
1006   reviewed, and a Pugh diagram was constructed (shown above in Table 2). The best decision
1007   moving forward with the project would be to use the National Semiconductor motor control
1008   LM628M-8 (shown in Table 3 below). In addition to it being the clear winner in the Pugh
1009   diagram a short list of reasons for choosing this item is below.
1010
1011                               Table B1.3: Controller Pugh Diagram
                                                                Concept
                                               LM629           CV-2114B            Parallax HB-25
          Selection Criteria     Weight   Rating Weight Rating Weight              Rating Weight
            Output power          20%        4        0.8     3         0.6          3       0.6
                  Cost            15%        4        0.6     2         0.3          2       0.3
         Operating Frequency      15%        5       0.75     2         0.3          4       0.6
           Circuit protection     15%        3       0.45     3        0.45          4       0.6
                  Size            10%        4        0.4     2         0.2          2       0.2
           Programmability        25%        3       0.75     4          1           4        1
                                  Total
                                  score         3.75              2.85                  3.3
                                  Rank            1                 3                    2
                                Continue?       Yes                no                   no
1012
1013   Reasons to use the LM629M-8:
1014   - One of the most enticing features of this unit is its ability to integrate with a speed
1015   encoder such as the Renco R35i series. It has three inputs from the encoder on the chip
1016   which goes directly to the internal software programmable PID controller. This has two
1017   major benefits. First, since the controlling feedback is not going all the way back to the
1018   central processor, it will be much less affected by noise. However, this is not to say that the
1019   processor will not receive speed, position, and temperature readings. Also, this will help to
1020   avoid unnecessary system bus use and avoid the processor handling all speed correction on
1021   the module itself.
1022   - The LM629 is capable of operating at 8MHz. This should allow for sufficiently minimal
1023   communication with the microprocessor and reduce time on the system bus.
1024   - The cost is a major plus for this device. Available on the Digikey website for $42.02 with
1025   six modules, and assuming a cost for an H-bridge and wiring, all the electrical components
1026   for the modules should equate to, roughly $365.
1027   - This particular controller also has two different control modes.
1028
1029   Position mode: This mode requests that the user defines a final displacement, a velocity
1030   limit, and an acceleration rate. Given this information the controller will create a velocity
1031   profile. Additionally, the user has the ability to change the velocity limit or displacement
1032   values on the fly. Therefore, if coupled with timed steering and proper data writing from the
1033   microprocessor the user can define intricate paths of motion for the robot.
1034



                                                  34 of 84
                                                  P07202
1035   Velocity mode: This mode requests that the user gives a determined velocity and
1036   acceleration. With this the controller with bring the module up to speed and stay there until
1037   issued a stop command. This mode seems like it could be very useful for small robotic feats
1038   and easy to use as a debug mode in the early stages of Senior Design 2.
1039
1040   - This controller has several user defined interrupts. This will prove useful in the early
1041   stages of building the robot and will serve as a good safety net for the system.
1042   - The LM629 Does not explicitly claim that it‟s I2C capable, but it should integrate easily with
1043   that platform. If the bus will allow it, the microprocessor can address all of the controllers
1044   simultaneously and greatly increase system efficiency.
1045   - The chip has a 27 instruction set which is a two-byte hex input to allow for complete
1046   control of the system from the programmer. This will allow for a very adaptable user defined
1047   system, as opposed to any hard-programmed circuitry.
1048
1049   Speed Encoder Concepts:
1050   Once the control architecture of the motor is established steps must be taken to monitor the
1051   system. By monitoring the speed of the wheel and the angular displacement of the steering
1052   actuator complete control of the vehicle can be established in the design code. However,
1053   these systems need to be connected back to the microprocessor so it can make corrections
1054   to the system command outputs based on the feedback it receives.
1055
1056   Nearly every option listed above in Table 1 can incorporate a generic feedback system that
1057   doesn‟t intrude on the input circuitry at all. This is accomplished by placing a commercial
1058   speed encoder on the motor‟s drive shaft. This can then be fed back to the micro processor
1059   via a PID controller which can be configured throughout the design phase. This is a natural
1060   solution with its own set of pros and cons. However, the National brand motor controller
1061   from Table 1 above (mfg. part number LM629) offers a different approach to this problem.
1062   The LM629 had a built in PID controller and the internal circuitry to correct its own output.
1063   This again offers its own set of pros and cons outlined below.
1064

1065   B1.iv Independent encoder setup:
1066   Pros
1067             Will not contribute to overheating of motor controller
1068   Cons
1069             Depends on central processor to perform system monitoring
1070             Feedback is susceptible to noise
1071             More wiring/interfacing
1072             Supplied power issues
1073

1074   B1.v Motor Controller monitoring
1075   Pros
1076             Does not depend on micro processor to make adjustments
1077             Makes the system more modular
1078             Less I/O interfacing
1079             Still have the ability to customize the encoder
1080             PID programmable to the hardware
1081   Cons
1082             Might be prone to overheating issues, because of the increased workload
1083             Unforeseen difficulties interfacing with microcontroller
1084             Will not control braking mechanism


                                                  35 of 84
                                                  P07202
1085
1086   Regardless of the concept chosen to monitor and correct the feedback, the motor speed
1087   encoder is still going to be necessary to the system. This encoder will rest on the motor
1088   armature prior to the transmission connection and give its results to either the motor
1089   controller or the micro processor of the system.
1090
1091   Conclusion
1092   In the end the decision to go with the Nation Semiconductor LM629 chip should prove most
1093   effective for this project. Its cost is still low enough to fit within the budget. Also, it is a
1094   commercial product with a fully descriptive data sheet to show operation. This concept
1095   should yield complete control over the speed of our motor unit. This method should also
1096   prove to be very modular and adaptable in the future with a code set that will be easy to
1097   understand and highly configurable. The system communication over the chosen bus will be
1098   effective and highly responsive.
1099
1100   There is a short list of concerns to keep in mind for the future, however. When attached to a
1101   robot the motor modules need to be able to work together to attain a cohesive robotic
1102   dynamic. If parallel communication to the modules is not available the series instructions
1103   should be made timely or cycle through the module such that they will operate
1104   simultaneously with their movement profiles. The H-bridge should be able to take it‟s
1105   interrupts from the controller‟s programmable ones so that during an error state the
1106   circuitry will in no way malfunction or become damaged. Additionally, with the magnitude of
1107   power this system will consume it is essential that thermal concerns be kept in mind
1108   throughout the fabrication process.
1109
1110   If these concerns are addressed at the modules are built there is no reason why this
1111   architecture should not be fully functional end efficient.




1112
1113

                                                  36 of 84
                                                  P07202
1114   B2        Control Circuit Concepts
1115
1116   The following subsystem design concepts are for the project P07202: Motor Module RP100.
1117   The subsequent report shall give an overview of the types of possible control circuit
1118   concepts that may be viable to the following project. Choosing an optimal control circuit
1119   depends on the type of motor being driven and the types of inputs and outputs
1120   desired/required to be transmitted back and forth between the circuitry.
1121
1122                                               Circuit types:

1123   B2.i      H-Bridges
1124   “An H-bridge is an electronic circuit which enables DC electric motors to be run forwards or
1125   backwards. These circuits are often used in robotics. H-bridges are available as integrated
1126   circuits, or can be built from separate components. A solid-state H-bridge is typically
1127   constructed using reverse polarity devices.”1
1128        Pros
1129               1. Simple design (architecture)
1130               2. Easy to create (circuit wise)
1131               3. Cheap, easy to obtain
1132               4. Easy to integrate with many types of motors
1133        Cons
1134               1. Initial reset may close a short circuit or stress on the H-bridge. (Inductive
1135                   loads and protection diodes will solve problem)
1136               2. May not be able to handle high loads depending on its constraints (Possible
1137                   currents that motors may draw could damage circuitry)




1138
1139                                         Example of H-Bridge circuit2
1140
1141   Reference:
1142   http://www.robotroom.com/HBridge.html
1143
1144
1145
1146
1147


       1
           http://en.wikipedia.org/wiki/H_bridge
       2
           http://www.robotroom.com/HBridge.html

                                                      37 of 84
                                                      P07202
1148   B2.ii Variable Frequency Drive (VFD)
1149   “A Variable Frequency Drive (sometimes abbreviated VFD) is a system for controlling the
1150   rotational speed of an alternating current (AC) electric motor by controlling the frequency of
1151   the electrical power supplied to the motor. A variable frequency drive is a specific type of
1152   adjustable speed drive. Variable frequency drives are also known as adjustable frequency
1153   drives (AFD), variable speed drives (VSD), AC drives or inverter drives.” 3 DC Variable
1154   Speed Drives (VSD) is also available for DC drives.
1155        Pros
1156               1. An embedded microprocessor governs the overall operation of the VFD
1157                   controller.
1158               2. Modern VFDs are affordable and reliable, have flexibility of control, and offer
1159                   significant electrical energy savings.
1160               3. User can customize the VFD controller to suit specific motor and driven
1161                   equipment requirements.
1162               4. Many of today‟s VFD‟s come with bypasses, in the event of a drive failure to
1163                   ensure the system or process would remain on line.
1164        Cons
1165               1. The main microprocessor programming is in firmware that is inaccessible to
1166                   the VFD user.
1167               2. Variable frequency drives can produce harmonics that can make their way
1168                   back to the rest of the circuitry and interfere with sensitive electronic
1169                   equipment and machines. Harmonic filtering may be necessary in some
1170                   applications.
1171               3. Operation at a constant voltage (reduced V/Hz) above a given frequency
1172                   provides reduced torque capability and constant power capability above that
1173                   frequency.




1174
1175                                           Example of PWM VFD circuit4
1176
1177   Reference:
1178   http://www.ecmweb.com/mag/electric_understanding_variable_speed_3/index.html
1179
1180
1181
1182
1183

       3
           http://en.wikipedia.org/wiki/Variable_Frequency_Drive
       4
           Ibid

                                                            38 of 84
                                                            P07202
1184   B2.iii Optical Isolator
1185   “In electronics, an opto-isolator (or optical isolator, optocoupler or photocoupler) is a
1186   device that uses a short optical transmission path to transfer a signal between elements of a
1187   circuit, typically a transmitter and a receiver, while keeping them electrically isolated - since
1188   the signal goes from an electrical signal to an optical signal back to an electrical signal,
1189   electrical contact along the path is broken.”5 Among other applications, opto-isolators can
1190   help cut down on ground loops and block voltage spikes.
1191
1192             Pros
1193                 1. Compatible with both single and dual power supply sources.
1194                 2. Will help protect equipment from dangerous ground loops, spikes and surges
1195                    that may be generated from the motors.
1196                 3. Readily available in industry, comes in various sizes and circuit types
1197                 4. Ideal for receiving encoded digital data (Speed Controller)
1198             Cons
1199                 1. Maybe a bit expensive, depending on our system requirements.
1200                 2. Ideally used for digital signals.
1201




1202
1203                                            Example of Optical Isolator IC6
1204
1205   Reference:
1206   http://www.bb-elec.com/product_family.asp?FamilyId=1
1207   http://www1.jaycar.com.au/images_uploaded/optocoup.pdf
1208   http://electronents.v21hosting.co.uk/optocoupler-applications.htm
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224

       5
           http://en.wikipedia.org/wiki/Opto-isolator
       6
           Ibid

                                                           39 of 84
                                                           P07202
1225   B2.iv Pulse Width Modulators (PWM)
1226   “Pulse-width modulation of a signal or power source involves the modulation of its duty
1227   cycle, to either convey information over a communications channel or control the amount of
1228   power sent to a load.”7 This type of data transmission maybe used to encode and decode
1229   specific data between systems. PWM is also often used to control the supply of electrical
1230   power to another device such as in speed control of electric motors.
1231
1232             Pros
1233                 1.   Many modern microcontrollers come with PWM transmission types.
1234                 2.   PWM signals can be generated in a number of ways.
1235                 3.   Readily available chips that use PWM transmission systems.
1236                 4.   System costs and power consumption can be drastically reduced.
1237             Cons
1238                 1.   Cost, in the sense that either the PWM will be included in the microprocessor
1239                      chosen to be used or it may be external, thus needing additional design and
1240                      integration.




1241
1242                                           Example of a PWM controller8
1243
1244   Reference:
1245   http://homepages.which.net/~paul.hills/Circuits/PwmGenerators/PwmGenerators.html
1246   http://www.netrino.com/Publications/Glossary/PWM.html
1247
1248
1249
1250
1251
1252
1253

       7
           http://en.wikipedia.org/wiki/Pulse-width_modulation
       8
           http://www.nomad.ee/micros/pwm555.html

                                                            40 of 84
                                                            P07202
1254   Discussion:
1255   As shown in the Pugh diagrams above, controllers that may be used for the motor will either
1256   be a Variable Frequency Drive or a Pulse width Modulator. From the documentation above,
1257   one may be preferred over the other depending on the type of motor being driven (DC or
1258   AC motor). AC motors operate by passing a current through the coil, generating a torque
1259   on the coil. Since the current is alternating, the motor will run smoothly only at the
1260   frequency of the sine wave. One of the drawbacks of this kind of AC motor is the high
1261   current which must flow through the rotating contacts. Sparking and heating at those
1262   contacts can waste energy and shorten the lifetime of the motor. 9 In comparison; a DC
1263   motor operates similarly to an AC motor however, in terms of controllability, they are
1264   generally easier to control.
1265   In terms of pricing, the general size and magnitude needed for this design project, the
1266   motors selected will generally be the same price. There may be a variation in the sense of
1267   forty to eighty or so dollars, so that may be negligible. In terms of power consumption,
1268   VFD controllers designed to operate at 110 volts to 690 volts are often classified as low
1269   voltage units. Low voltage units are typically designed for use with motors rated to deliver
1270   0.2kW or 1/4 horsepower (Hp) up to at least 750kW or 1000Hp10. Thus they may not be
1271   ideal for this project; in contrast the PWM is used in many applications and has many
1272   advantages over the VFD shown in the following Pugh diagrams below.
1273
                                                            Motor Control types
                                                                   B1.ii                   B1.iv
                                                            Variable Frequency          Pulse Width
                                                                   Drive                 Modulator

                           Selection Criteria     Weight    Rating     Weighted      Rating    Weighted
                                                                        Score                   Score
                           Noise Immunity           25%           3           0.75        4             1
                           Ease of                  10%           3            0.3        4           0.4
                           Implementation
                           Size                     10%           3            0.3        4           0.4
                           Cost effective           20%           2            0.4        3           0.6
                           Ease of                  10%           3            0.3        4           0.4
                           replacements
                           Power                      5%          1           0.05        4           0.2
                           consumption
                           Ease of                  10%           3            0.3        4           0.4
                           integration
                                                Net Score             2.4                     3.4
                                                    Rank               2                       1
1274
1275                                  Table B1.a: Comparison of motor controllers
1276
1277
1278
1279
1280
1281

       9
           http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/motorac.html
       10
            http://en.wikipedia.org/wiki/Variable_frequency_drive

                                                            41 of 84
                                                            P07202
                                                  Control Subsystem Concepts
                                                   B1.i                B1.ii                        B1.iv
                                                 H-Bridge             Variable                   Pulse Width
                                                                  Frequency Drive                 Modulator
            Selection Criteria     Weight    Rating    Weighted        Rating     Weighted    Rating    Weighted
                                                        Score                      Score                 Score
            Adaptability             20%          4            0.8          4           0.8        4          0.8
            Ease of use               5%          4            0.2          3          0.15        3         0.15
            Readability of            5%          3           0.15          4           0.2        4          0.2
            Settings
            Durability                5%          3           0.15          4           0.2        3         0.15
            Ease of                  20%          4            0.8          4           0.8        4          0.8
            Manufacturing
            (COTS)
            Price                    20%          5              1          3           0.6        4           0.8
            Power                     5%          4            0.2          4           0.2        4           0.2
            consumption
            Troubleshooting           10%         3            0.3          3           0.3        3           0.3
            Sensitivity               10%         2            0.2          2           0.2        3           0.3
                                 Net Score            3.8                       3.45                   3.7
                                     Rank              1                          3                     2
1282
1283                                Table B1.b: Comparison of motor controllers
1284
1285   Summary:
1286   In summary, they design concepts presented above are the choices considered for
1287   controlling the motor module. From the comparisons and Pugh diagrams, the variable
1288   frequency drive would most likely not be considered in this design.         The operation
1289   parameters and power requirements does not appear to fit with the design parameters of
1290   this project. On a secondary note, the Optical isolator may be used in the overall circuitry,
1291   not as a controller type but as a junction between the speed encoder and the
1292   microprocessor.
1293
1294   By comparing and contrasting the various controller systems, and contrasting the types of
1295   motor modules available to our project, the overall controller will include an H-Bridge to
1296   control the driving direction of the motor (forward and reverse). The Pulse width Modulator
1297   (PWM) will be used to vary the speed of the motor and tying all these systems together the
1298   microcontroller should be sending all the instructions.
1299
1300   During design, many worst case scenario situations will be considered when implementation
1301   takes effect. A few of these considerations that would greatly affect the proper operation of
1302   our control system would be noise that might affect signals being sent, power surges that
1303   may occur from external and internal sources and proper timing in the circuitry for
1304   synchronous operation. These design risks shall be addressed in additional documentation
1305   afterward.
1306




                                                            42 of 84
                                                            P07202
1307   B3       Power Sub-System
1308   There are two concepts for the power supply. The first is two have a single power supply for
1309   the complete system and then step it down to provide lower voltages for the logic circuit
1310   design. The second concept is to have a different power supply for motors and logic circuitry.
1311
1312   The concept 1 for the power design is simple to implement as one is dealing with only one
1313   main power unit. Also any other low power consuming unit can be easily integrated into the
1314   design without worrying any power mismatch in the design. The whole system will go down
1315   if battery runs out of energy and hence shut down the complete system which is one of the
1316   requirements of the design. The only extra work in this system is the design of step down
1317   circuitry for lower power circuit.
1318
                                 Step Down Power
                                                                                    Main Power
                                 Circuit for Logical
                                                                                      Supply
                                     Circuitry




         7302 Control                                             microcontroller
                                  microProcessor                                      Motors
            Board                                                 and other Logic

1319
1320                              Fig1: Concept 1 for power distribution
1321
1322   The concept 2 is easy to implement in the sense that no circuitry for stepping down is
1323   required. The down side of this type system is that to integrate any other system along with
1324   this, one has to use another power circuitry for that. The problem one will face is the
1325   recharging of the battery as two separate systems have to be designed to charge the
1326   battery separately. It‟s difficult to see which system goes down if any of the supply run out
1327   of energy and last is the fact that as the design requires shutting the complete system for
1328   safety precaution, it is obvious from this design that this cannot be achieved with this kind
1329   of implementation.
1330
                                  Power Supply for                                  Main Power
                                  Logical Circuitry                                   Supply




         7302 Control                                             microcontroller
                                  microProcessor                                      Motors
            Board                                                 and other Logic

1331
1332                              Fig2: Concept 2 for power distribution
1333

1334   B4       Power Systems
1335


                                                       43 of 84
                                                       P07202
1336   Power Systems consists of the central distribution and regulation of all power sources. A
1337   crucial part in mobile robotics, clean power is needed for the microprocessor to function
1338   correctly, and sufficient power to meet the motor requirements.
1339
1340   This document will attempt to categorize and compare the different approaches to building a
1341   robust power system useful for the P7202 project.
1342
1343   Arrangements
1344   Two arrangements have been presented two battery method and a single battery method.
1345   In the dual battery method one smaller battery will power the digital systems while the
1346   other is used primarily for the motor system. In the single battery method one battery will
1347   power all systems. (Refer to figure B1.1)
1348

                                           Indirect Charge Logic Battery charged from external Power
          2 Battery System
                                           Direct Charge     Logic Battery charged from Motor Battery
                                                             when in Stand By
          1 Battery System
1349
1350                                                Figure B1.1.0
1351
                                       PRO                               CON
       2 Batteries (Indirect)          -Isolation of Power               -Requires 2 regulations
                                       -Less Regulation needed           units to charge each
                                       on digital Side                   battery individually
       2 Batteries (Direct)            -Isolation of Power               -Requires 2 regulation
                                       -Less regulation needed on        units to charge one
                                       digital Side                      battery from the other
                                                                         -Need to wait for logic
                                                                         battery to charge from
                                                                         motor battery
       1 Battery                       -Simplicity                       -Requires Regulation
                                       -Easy to swap battery and         -Heavy regulation to kill
                                       continue working with the         transients in the signal
                                       robot
1352                            Table B1.1.0: Battery Pro/Con Comparison Table
1353
1354   Power Loss Calculations
1355   Power Loss calculations can be done with some simple estimation below in figure 2.0 is a
1356   tree list of powered sub systems.


                                               Power System




                                   Motor Controls         Power Controls
              Motor               (estimate: 10%<        (estimate: 10% of                  Logic
                                      of Motor)             total power)
1357
1358                                                Figure B1.2.0

                                                      44 of 84
                                                      P07202
1359
1360   Motor:
1361   Based of the motor used in first on average 27 Amps, peak of 67.9Amps (Peak will exceed
1362   this if the system stalls, the Micro-Controller should kill power if current is seen going above
1363   the peak current)
1364
1365   Motor Controls:
1366   10% of Motor (Heavy over estimate for initial consideration)
1367
1368   Logic:
1369   Based off the Altera Cyclone II which uses 0.5Watts in its worst case scenario, we can
1370   assume 1 to 2 Watts of power consumption.
1371
1372   Power Controls:
1373   10% of total System (Heavy over estimate for initial consideration)
1374
                                              Peak                       Average
                     Device       Volts      Amps       Watts    Volts   Amps       Watts
                      Motor        12        67.9*      814.8     12      27*        324
                      Motor
                     Controls     12          N/A       81.48    12       N/A        32.4
                      Logic       N/A         N/A         2      N/A      N/A         2
                      Power
                     Controls      12         N/A       89.828    12      N/A       35.84

                        Total      12   82.34233    988.108  12   32.85333          394.24
1375                                Table B1.2.0: Power Use Summary
1376
1377   *Numbers taken from FIRST Motor used for characterization, only one motor considered.
1378
1379   For the purposes of comparison the Odyssey batteries have been used
1380   (http://www.odysseybatteries.com/batteries.htm) the PC925 can do 27Ah for 10 hours,
1381   more than meeting our needs but consuming 26lb of weight from our available 88lb, and
1382   pushing the battery.
1383
1384
1385
1386
                                                            Concepts
                                                    A                      B
                                                One Battery           Two Batteries
       Selection                                  Weighted              Weighted
       Criteria          Weight           Rating Score           Rating Score
       Ease of Use               10%           5             0.5      2              0.2
       Ease of Design            10%           5             0.5      1              0.1
       Running Time              15%           3            0.45      4              0.6
       Charging Time             20%           5               1      2              0.4
       Weight                    10%           4             0.4      2              0.2
       Size                      20%           3             0.6      3              0.6
       Price                     15%           4             0.6      3             0.45
                         Total Score               4.05                   2.55


                                                     45 of 84
                                                     P07202
                        Rank                   1                      2
                        Continue?             Yes                     No
1387                     Table B1.3.0: Pugh diagram of the Battery Comparison
1388
                                                               Concepts
                                                      A                         B
                                                    LiIon                      SLA
                                                    Weighted                   Weighted
       Selection Criteria   Weight         Rating   Score             Rating   Score
       Price                         15%        1              0.15        5              0.75
       Size                          25%        5              1.25        4                 1
       Charging
       Complexity                   10%        2           0.2       3            0.3
       Weight                       25%        5          1.25       2            0.5
       Durability                   25%        3          0.75       5           1.25
                            Total Score            3.6                   3.8
                            Rank                    2                     1
                            Continue?              No                    Yes
1389                        Table B1.3.1: Table Comparing Large Battery Supplies
1390
                                                                     Concepts
                                                A                        B                     C
                                              LiIon                    NiMH             Standard Battery
       Selection                               Weighted                 Weighted              Weighted
       Criteria        Weight          Rating Score             Rating Score           Rating Score
       Price                     15%        1        0.15            3        0.45          5         0.75
       Size                      10%        5         0.5            3         0.3          4          0.4
       Charging
       Complexity               10%          2          0.2           4          0.4         0            0
       Weight                   20%          4          0.8           3          0.6         4          0.8
       Durability               35%          4          1.4           2          0.7         1         0.35
       Charging Time            10%          5          0.5           3          0.3         5          0.5
                       Total Score             3.05               2.45                           2.3
                       Rank                      1                  2                             3
                       Continue?               Yes               Develop                         No
1391                         Table B1.3.2:   Comparing Small Battery Supplies
1392
1393   Conclusion
1394   Using one battery versus two comparisons shows an advantage in using a single source to
1395   power the entire robot. Comparing the battery choices for simplicity and meeting industry
1396   working standards a SLA (Sealed Lead-Acid) battery is the best choice. If the choice is still
1397   decided that dual battery system will be used based off of customer feedback (Customer is
1398   willing to negate simplicity for increased isolation of power) and or other Pugh charts
1399   negating the results found in table B1.3.0, a comparison shows a LiIon as being the best
1400   choice for the logic systems battery providing the best charge and, if price is found to be a
1401   larger determining factor than it is currently considered a NiMH battery would be the runner
1402   up, using a standard battery such as an Alkaline falls outside of our requirements since its
1403   not rechargeable and would require frequent replacement.
1404
1405
1406
                                                    46 of 84
                                                    P07202
1407   B5     Proof of Concept – Single Battery Regulation
1408   Some concerns were mentioned at the use of a single battery system. The concern was over
1409   feedback from the motors. To illustrate the effectiveness of a Switching Regulator some
1410   quick estimation PSpice models have been made up to illustrate the spike suppression. Due
1411   to the limited time a model of the Switching regulator wasn‟t available, in its place a linear
1412   regulator was used in the simulation simply for proof of concept.
1413
1414   Design Description:
1415   The design consists of the most basic elements, assuming an ideal 12VDC battery, a pulse
1416   generator is placed inline with it to generate 100 Volt spikes in both the positive and
1417   negative direction; this will illustrate the effect of direction changes and abrupt stopping of
1418   the motor. TVS, Transient voltage suppressors are simply bidirectional forms of Zener
1419   diodes to suppress voltage spikes from both the positive and negative line. In this
1420   simulation the negative line is omitted and it has been grounded. The overall circuit omits
1421   grounding issues and ties all grounds together for the purposes of simple simulation. Zener
1422   diodes where used for the input voltage the Zener‟s selected at 15V Zener‟s, meaning
1423   spikes above 15V will be suppressed by the Zener‟s. More than one was used because each
1424   was only 1Watt (models of larger TVS‟s were unavailable). A large input capacitor is used to
1425   help maintain voltages when a negative spike occurs; the inline diode is to keep the
1426   negative spike from draining its current from the capacitor. The negative spike will clearly
1427   be the biggest risk in the design, if the future design uses a dual battery system with +12V
1428   and -12V suppression of this negative spike will be easier by using a diode bridge, similar to
1429   those used to regulate AC to DC. Next a linear regulator is setup to regulate 5VDC at
1430   7.5Amps more than meeting out digital logic need. The output is also regulated with a large
1431   capacitor to help protect against random power spikes (turning a device on and off) from
1432   the logic side. A second Zener on that side in application is more to project the logic lines
1433   form external spikes, but it also serves to assist the linear regulator in cleaning up the
1434   output.
1435
1436   Placing a resistor from the input Zener diodes to the backflow diode will assist and almost
1437   entirely neutralize any transients from a positive spike but comes at a cost to the power
1438   consumption.
1439
1440   Design/Simulation:




                                                  47 of 84
                                                  P07202
                                  Vinput




                                       V
        V1 = 0       V4
        V2 = 100
                          I
        TD = 1m
        TR = 1u
        TF = 1u
        PW = 1m
        PER =

                     V3
         VOFF = 0                                                                              U1
         VAMPL = 0                                                  R8            D7           LT1084/LT                                  Vout
       FREQ = 1k                                                                  1    2   3                    2




                                                                                                       ADJ
                                                                                                IN       OUT
                                                                    100           1N4500
                                    D11                  D10                                                        R2        D9          C2                 V
                     V2                                                       I
            12Vdc                    D1N4744             D1N4744                               C1                       121   D1N4733     150u          R1




                                                                                                     1
                                               D12                 D13                         1000u                                                    2.5

                                               D1N4744             D1N4744                                              R3
                     V1
              0Vac
              0Vdc
                                                                                                                        365        0           M2                     Von_off


                                                                                                                                          MbreakN
                                                                                                                    0

                              0

                                                                                                                                                                 V1 = 5       V5
                                                                                                                                                    0            V2 = 5
                                                                                                                                                                 TD = 1m
                                                                                                                                                                 TR = 1u
                                                                                                                                                                 TF = 1u
                                                                                                                                                                 PW = 1m
                                                                                                                                                                 PER = 2.5m


1441                                                                                                                                                                            0

1442                                           Figure B2.1.0: Positive 100V transient test circuit
1443
                   2.0A

                                                               Current on R8
                   1.0A



                     0A
                                  I(R8)
                   200V


                                                                             Vinput
                   100V



                     0V
                                  V(D10:2)
            5.004V
                                                           (1.0273m,5.0034)

                                                                                           Vout
            5.002V

                                                                              (2.0354m,5.0010)
             SEL>>
            5.000V
                  0s                                           2.0ms                                           4.0ms                    6.0ms
                                  V(U1:OUT)
1444                                                                                Time

                                                                                   48 of 84
                                                                                   P07202
1445                                   Figure B2.1.1: Overall circuit simulation of Figure B2.1.0
1446
1447
                              Vinput




                                   V
        V1 = 0       V4
        V2 = -100
        TD = 1m
        TR = 1u
        TF = 1u
        PW = 1m
        PER =

                     V3
         VOFF = 0                                                                         U1
         VAMPL = 0                                              R8           D7           LT1084/LT                               Vout
       FREQ = 1k                                                             1    2   3                   2




                                                                                                  ADJ
                                                                                           IN       OUT
                                                                100          1N4500
                                D11                  D10                                                      R2        D9        C2                 V
                     V2                                                  I
            12Vdc                D1N4744             D1N4744                              C1                      121   D1N4733   150u          R1




                                                                                                1
                                           D12                 D13                        1000u                                                 2.5

                                           D1N4744             D1N4744                                            R3
                     V1
              0Vac
              0Vdc
                                                                                                                  365        0         M2                     Von_off


                                                                                                                                  MbreakN
                                                                                                              0

                          0

                                                                                                                                                         V1 = 5       V5
                                                                                                                                            0            V2 = 5
                                                                                                                                                         TD = 1m
                                                                                                                                                         TR = 1u
                                                                                                                                                         TF = 1u
                                                                                                                                                         PW = 1m
                                                                                                                                                         PER = 2.5m


1448                                                                                                                                                                    0

1449                                       Figure B2.2.0: Negative 100V transient test circuit.
1450




                                                                              49 of 84
                                                                              P07202
                 200mA

                                                                              Current on R8
                          0A



                 -200mA
                                        I(R8)
                     100V

                                                                                 Vinput
                          0V



                 -100V
                                        V(D10:2)
            5.0020V
                                                            (2.0329m,5.0017)
                                                                                               Vout
            5.0015V

                                              (1.0325m,5.0014)
              SEL>>
            5.0010V
                   0s                                                 2.0ms                                        4.0ms                  6.0ms
                                        V(U1:OUT)
1451                                                                                     Time
1452                                          Figure B2.2.1: Overall circuit simulation of Figure 2.0
1453
                               Vinput


                                          V
        V1 = 0       V4
        V2 = 0
        TD = 0
        TR = 0
        TF = 0
        PW = 0
        PER =

                     V3
         VOFF = 0                                                                                  U1
         VAMPL = 0                                                      R8            D7           LT1084/LT                                Vout
       FREQ = 1k                                                                      1    2   3                   2
                                                                                                           ADJ




                                                                                                    IN       OUT
                                                                        100           1N4500
                                        D11                 D10                                                        R2        D9         C2                 V
                      V2                                                          I
            12Vdc                       D1N4744             D1N4744                                C1                      121   D1N4733    150u          R1
                                                                                                         1




                                                  D12                  D13                         1000u                                                  2.5

                                                  D1N4744              D1N4744                                             R3
                     V1
              1Vac
              0Vdc
                                                                                                                           365        0          M2                     Von_off


                                                                                                                                            MbreakN
                                                                                                                       0

                           0

                                                                                                                                                                   V1 = 5       V5
                                                                                                                                                      0            V2 = 5
                                                                                                                                                                   TD = 1m
                                                                                                                                                                   TR = 1u
                                                                                                                                                                   TF = 1u
                                                                                                                                                                   PW = 1m
                                                                                                                                                                   PER = 2.5m


1454                                                                                                                                                                              0

1455                                                    Figure B2.3.0: Circuit for AC Sweep analysis

                                                                                       50 of 84
                                                                                       P07202
1456
             -0d             -50
       1                2




                                                                                                                                          (19.953K,-89.076)
           -50d

                             -100



           -100d



                             -150

           -150d




                               >>
           -200d             -200
                               1.0Hz                                            100Hz                                            10KHz                                    1.0MHz
                                  1          P(V(U1:OUT))             2         DB(V(U1:OUT))
1457                                                                                       Frequency
1458       Figure B2.3.1: Bode Plot of the frequency response at the output of the circuit in figure
1459                                               B2.3.0
1460
1461   As can be seen in figure B2.3.1 the frequency response is heavily damped to prevent high
1462   frequency surges from passing threw with a worst case damping at 19.953k Hz; because of
1463   this the following noise analysis is done at that frequency.
1464
                              Vinput


                                         V
           V1 = 0       V4
           V2 = 0
           TD = 0
           TR = 0
           TF = 0
           PW = 0
           PER =

                        V3
           VOFF = 0                                                                                U1
         VAMPL = 25                                                    R8             D7           LT1084/LT                                       Vout
       FREQ = 19.953k                                                                 1    2   3                   2
                                                                                                           ADJ




                                                                                                    IN       OUT
                                                                       100            1N4500
                                       D11                 D10                                                         R2            D9            C2             V
                        V2                                                        I
               12Vdc                   D1N4744              D1N4744                                C1                      121           D1N4733   150u          R1
                                                                                                         1




                                                 D12                  D13                          1000u                                                         2.5

                                                 D1N4744              D1N4744                                              R3
                        V1
                0Vac
                0Vdc
                                                                                                                           365             0            M2                  Von_off


                                                                                                                                                   MbreakN
                                                                                                                       0

                             0

                                                                                                                                                                       V1 = 5       V5
                                                                                                                                                             0         V2 = 5
                                                                                                                                                                       TD = 1m
                                                                                                                                                                       TR = 1u
                                                                                                                                                                       TF = 1u
                                                                                                                                                                       PW = 1m
                                                                                                                                                                       PER = 2.5m


1465                                                                                                                                                                                  0

1466                                                       Figure B2.4.0: Test circuit for AC hum

                                                                                      51 of 84
                                                                                      P07202
1467
                 40V




                    0V



                                                                                            Vinput

                 -40V
                              V(D10:2)
           5.004V


                                                                                                Vout


           5.002V




            SEL>>
           5.000V
                 0s                                    1.0ms                   2.0ms                                3.0ms              4.0ms                           5.0ms
                              V(U1:OUT)
1468                                                                                                 Time
1469      Figure B2.4.1: AC hum signal analysis done on worst case frequency from figure B2.4.0
1470
                              Vinput


                                         V
        V1 = 0       V4
        V2 = 0
        TD = 0
        TR = 0
        TF = 0
        PW = 0
        PER =

                     V3
         VOFF = 0                                                                               U1
       VAMPL = 0                                                      R8           D7           LT1084/LT                                 Vout
       FREQ = 1k                                                                   1    2   3                   2
                                                                                                        ADJ




                                                                                                 IN       OUT
                                                                      100          1N4500
                                       D11                 D10                                                      R2        D9         C2                  V
                         V2                                                    I
            12Vdc                      D1N4744             D1N4744                              C1                      121   D1N4733     150u          R1
                                                                                                      1




                                                 D12                 D13                        1000u                                                   2.5

                                                 D1N4744             D1N4744                                            R3
                     V1
              0Vac
              0Vdc
                                                                                                                        365        0           M2                     Von_off


                                                                                                                                          MbreakN
                                                                                                                    0

                              0

                                                                                                                                                                 V1 = 0       V5
                                                                                                                                                    0            V2 = 5
                                                                                                                                                                 TD = 1m
                                                                                                                                                                 TR = 1u
                                                                                                                                                                 TF = 1u
                                                                                                                                                                 PW = 1m
                                                                                                                                                                 PER = 2.5m


1471                                                                                                                                                                            0

1472                      Figure B2.5.0: Output test circuit for logic device being turned on and off
1473




                                                                                    52 of 84
                                                                                    P07202
          16.000mA
                       Current for R8

          15.995mA


             SEL>>
          15.990mA
                      I(R8)
              20V
                              Vinput

              10V



               0V
                      V(D10:2)
          5.0018V

                                 Vout
          5.0016V



          5.0014V
                 0s                    1.0ms   2.0ms           3.0ms           4.0ms         5.0ms
                      V(U1:OUT)
1474                                                    Time
1475     Figure B2.4.1: Output response to the logic devices being turned on and off from figure
1476                                             B2.5.0
1477
1478   Conclusions
1479   The overall goal of this document is to convince the reader and myself in the feasibility of
1480   using a single battery power source and then filtering the power for the logic systems. From
1481   the extreme spikes shown and with the consideration that the motors will be protected with
1482   there own feedback diodes and that the Logic devices have there own built in single stage
1483   regulation witch should more than nullify the remaining transients on the line. Based on the
1484   simulations it is feasible to use a single power source in the robotic design.
1485
1486   Motor Characteristics Comparison
1487   The motor used for the FIRST robotics was characterized to provide a basis of comparison to
1488   the power systems. Below you‟ll find the wave forms taken from a series of tests done to
1489   show worst case conditions on the motor.
1490




                                                53 of 84
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1491
1492   Figure 7.0: High Voltage Spike from AC hum when running the Motor with no resistance
1493




1494
1495   Figure 7.1: Low Voltage Spike from AC hum when running the Motor with no resistance
1496




                                             54 of 84
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1497
1498       Figure 8.0: Motor turn on voltage spike
1499
1500




1501
1502   Figure 8.1: Motor reverse direction voltage spike
1503
1504
       Measurements         Recorded (V)   Simulation (V)   Pass
                      Max       18.5           100          Yes
       AC Hum         Min        8.5            25          Yes

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                                         Max       N/A           N/A       N/A
                          Motor Turn On  Min        0.6           0        Yes
                                         Max       20.9          100       Yes
                       Reverse Direction Min        6.2           0        Yes
1505       Table 1.0: Comparison test values to values measured from characterization motor
1506
1507   Conclusion
1508   Table 1.0 shows that based off the proof of concept test circuit, cleaning up the signal even
1509   when faced with the noise, feedback, and spikes generated by the motor is easily feasible
1510   and practical.
1511
1512   Risk assessment
1513   In regards to electrical for the 100kg motor module robot, there are many considerations to
1514   take in when designing a viable and easy to use structure for the operation of the robot.
1515   The basic characteristics that needs to be regulated are its Driving and speed characteristics,
1516   in addition to controlling the breaking and steering system of the module. Due to the size
1517   and specifications required by the motor module, high powered devices are most likely to be
1518   considered. The power considerations are mainly driven by the motor requirements and
1519   from our customer needs. Based on these design specifications, 3 major risks were assets
1520   during the design process. Noise, power regulation, and the types of control circuitry used
1521   during implementation (mainly its architecture). The following documentation will attempt
1522   to address these three issues and call into question the feasibility of certain design concepts.
1523
1524   Noise
1525   Noise is a big concern for the types of signals that will be sent and received in the circuit.
1526   The sources for noise are numerous and can hamper the proper operation of our motor
1527   module. Noise can come from both internal and external sources, examples of this would
1528   include;
1529        The motor itself
1530        Signal inputs
1531        Power supply connections
1532        Ground connections and loops (feedback)
1533
1534   The methods that maybe implemented to counteract this would be to use Low pass filters,
1535   proper wiring of circuit elements (Diodes, opto-isolators/couplers), and proper debug during
1536   the prototyping process. Much of the implementation for this solution is done during design
1537   and testing state of this project. The options available are vast however choosing the best
1538   circuit type or architecture for implementation would require more testing and internal
1539   referencing within our resources available (Professors, previous SD projects, etc).
1540
1541   Power regulation
1542   Being in the 100kg motor module group, power regulation for both the control circuitry and
1543   the motor itself is going to be a great issue. The motor may require a large amount of
1544   current and voltage when compared to the digital electronics and should any of that power
1545   feedback thought the control circuitry the possibility of overload is imminent. The sources
1546   of large power feeding back through the system may be from;
1547        Unfiltered Noise
1548        Large feedback from the motor
1549        Power up and power down of the motor module
1550        Unpredicted surges (Internal and external)
1551   Again, similar with the Noise solution implementation most of these problems should be and
1552   will be dealt with during the design and prototyping stage. Proper surge protection using


                                                  56 of 84
                                                  P07202
1553   filters, or the use of properly placed diodes should mitigate any unwanted back surges from
1554   feeding back into the electronics. Characterization of the motor module and the various
1555   worst case scenarios can be tested and measured to gauge the severity of any possible
1556   surge in the circuit. Not all possibilities may be found, however should any damage occur,
1557   ideally the damaged part should be easily replaced.
1558
1559   Architecture
1560   Based on the customer needs and the requirements desired to be implemented with this
1561   motor module, how the controller will be implemented is of great concern. Ideally, the
1562   customer wanted the following (summary);
1563          Safety
1564          COTS items
1565          Cost
1566          Controller is adaptable and there is room for future design and improvements
1567          Low end controller for high end functions (Customer quote)
1568          Ease of use
1569          Easy to modify
1570
1571   The major issues that is confronted here is implementation of these control systems to
1572   satisfy the customer needs. Taking into considerations the above topics, the two options
1573   that were available are:
1574
1575                 1. All in one inclusive controller type packages
1576                 2. Separate external controller packages connected together
1577
1578   Both systems have the potential to do what is desired for our design however each system
1579   has a significant advantage over the other.
1580
1581   All in one packages
1582
1583   Advantages:
1584       Includes all the controller systems desired to be implemented for the motor module
1585        (Internal PWM, noise immunity, surge protection, MIMO device)
1586       May already have desired specifications implemented for easy of use and possibly
1587        easy of implementation (programming)
1588       May include everything needed without hassle of extra design
1589
1590
1591   Disadvantages:
1592       Large all in one package types may be expensive
1593       Worst case scenario: A large surge may unexpectedly damage circuit, possibly
1594         forcing user to replace entire system
1595       May not fit customer desired function of Low end controller for high end
1596         specifications
1597       Future upgrades of the controller would mean replacing the entire all in one package.
1598
1599   External architecture
1600
1601   Advantages:
1602       Packages are all separated so it may be easy to modify should any unexpected
1603        damage occur or user desires an upgrade on certain parts of the controller. (Easy to
1604        modify)
1605       Many COTS available

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                                                P07202
1606         Overall cost will be higher for the purchase of multiple parts; however replacement
1607          and repair would be significantly cheaper.
1608         Overall scheme may satisfy customer need of Low end controller for high end
1609          operations
1610         Adds a little custom element to our implementation
1611
1612   Disadvantages:
1613       Implementation of the overall system may not be easy or work as intended.
1614       Power regulation and Noise issues may present a problem should certain sections of
1615         circuitry fail. May be difficult to debug.
1616       Use of additional circuitry components may need to be implemented due to possible
1617         unforeseen anomalies.
1618
1619   In conclusion, the major risks that plague our design would be seen in the architecture
1620   scheme of the controller/microprocessor.       Proper consultation with more experienced
1621   sources of information may lean the design to one side or the other. For the noise and
1622   power regulation specifications, the baseline kit that was provided to us gave a sense of
1623   what to expect when our motor module will be selected.              In general, the types of
1624   measurements and characterizations that were performed on the baseline kit will mostly
1625   likely be used for the actual motor selected. The methods and calculations will be the same
1626   however, in addition to the design process, a lot of prototyping and debugging will be
1627   performed in order to rectify any control issues that should arise.
1628
1629




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                                                P07202
1630   C. Microprocessor
1631   The motor module‟s processor is responsible for: facilitating communications with an
1632   external control board; instruction decoding; signal conditioning; and possibly feedback
1633   control. There are many ways these capabilities can implemented; however, they will all
1634   involve some combination of software and hardware description programming.
1635
1636   The concepts for the programming were developed by first considering the following:
1637                     C.1)     Control concepts
1638                     C.2)     Command and Instruction concepts
1639                     C.3)     Architectural concepts
1640                     C.4)     Protocols

1641   C1     Control Concepts
1642   To provide precision control over the motors it is necessary to adjust their output based on
1643   the deviation from the requested action. This is known as a control loop and it involves the
1644   following:
1645           Measurement the operation of plant
1646           Determining the correction in the controller element
1647           Acting through an output device to achieve that correction

1648   C1.i   PID Control
1649   4 variables:
1650      1. Proportional gain: Kp * Ec
1651      2. Intergral gain: Ki * Ec + Sum{all previous integral terms}
1652      3. Derivate gain: Kd * (En – Ec)
1653      4. Error term (Ec): feedback (motor speed) – set point (set speed)
1654          *number of encoder cnts per unit time




1655
1656                                     Fig C1.i.a – PID Control


                                                 59 of 84
                                                 P07202
1657   The PID controller is a widely used standard and is effective at accounting for the present
1658   (proportional), past (integral), and future (derivative) deviations from the desired output.
1659   Its transfer function is as follows:
1660


1661
1662
1663   There is a major concern when using a PID controller: the parameters must be precisely
1664   tuned so that the system does not continually oscillate around the desired value. Figure
1665   C1.i.b shows the results of a simple simulation where a PID controller is used to maintain a
1666   velocity. The three plots correspond to differing parameter values.
1667




1668
1669                                           Fig. C1.i.b
1670
1671   The third plot (shown in green) is an example of optimal parameter tuning. There are a
1672   variety of ways to tune these parameters ranging from simple trial and error with varying
1673   values to algorithmic approaches such as Ziegler-Nichols method.

1674   C1.ii Feedfoward control
1675   Reacts to changes in its environment, usually to maintain some desired state of the system.
1676   A system which exhibits feed-forward behavior responds to a measured disturbance in a
1677   pre-defined way
1678




                                                60 of 84
                                                P07202
1679
1680                                  Fig C1.ii – Feedfoward Control
1681
1682
1683   Let Gp and Gd be the transfer functions for the plant output and the stored program output
1684   (deviation) respectively:


1685


1686
1687
1688   The transfer function for this system is then Gd/Gp:



1689
1690
1691   Feedforward controls can be optimized to result in near perfect output; however, the ability
1692   to this is directly related to how well the system can predict the necessary adjustment to
1693   the output based on the environmental changes being measured.

1694   C1.iii Internal feedback-efferent
1695   Compares the efferent <exiting -> external> feedback with the internal feedback to fine-
1696   tune output
1697




1698

                                                 61 of 84
                                                 P07202
1699                                  Fig C1.ii – Feedfoward-efferent
1700
1701   This approach allows for the output of the internal control system to be improved using an
1702   external feedback that more quickly recognizes a deviation in the output.

1703   C1.iv Nonlinear Feedback Analysis
1704   A standard non-linear feedback system analysis problem was formulated by A.I. Lur'e.
1705   Control systems described by the Lur'e problem have a forward path that is linear and time-
1706   invariant, and a feedback path that contains a memory-less, possibly time-varying, non-
1707   linearity.
1708
1709




1710
1711                                     C1.iv: Nonlinear feedback
1712
1713   The linear part can be characterized by four matrices (A,B,C,D), while the non-linear part is
1714   Φ(y) E [a,b], a<b (a sector non-linearity).
1715
1716   Absolute stability problem:
1717          (A,B) is controllable
1718          (C,A) is observable
1719          Two real numbers a, b with a<b, defining a sector for function Φ
1720
1721   Must derive conditions involving only the transfer matrix H(s) and {a,b} such that x=0 is a
1722   globally uniformly asymptotically stable equilibrium of the system. This is the Lur'e problem.
1723
1724   The Popov theorem is one of primary ways to address this problem.
1725
1726   Popov criterion
                                                   where x E Rn,
                                                   ξ,u,y are scalars
                                                   A,b,c,d have commensurate dimensions




1727   The non-linear element Φ: R → R is a time-invariant nonlinearity belonging to open sector
1728   (0, ∞) thus Φ(0) = 0, y Φ(y) > 0, !A y ≠ 0;
1729
1730   The transfer function from u to y is given by:


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                                                  P07202
1731
1732
1733   Characteristics of a system where Popov criterion is applicable:
1734          Autonomous
1735          Pole at the origin and no direct pass-through from input to output
1736          Non-linearity Φ belongs to an open sector
1737

1738   C2    Command and Instruction Concepts
1739
1740   Commands
1741   ACC(Vf,a), ACC(d,a), ACC(t,a)
1742   MOVE(d,t), MOVE(d,v), MOVE(d,v,a), MOVE(d,v,t)
1743
1744   TURN(of, vo), TURN(o,t), TURN(o,do)
1745   ROTATE(o,t), ROTATE(o,v), ROTATE(o,d,v)
1746




1747
1748
1749   Instruction Encoding
1750          Dependent on precision of motor -> #bits needed for params
1751          #bits for codeword must cover all necessary commands (~15-20) and should
1752            leave room for growth
1753          BW/throughput optimization considerations effect sizing
1754          Must include address of the motor and other components (e.g. sensors)
1755          Consider providing capability for broadcasting to all and to groups
1756          Perhaps include priority to facilitate interrupts and IRQ masking
1757
1758
1759




                                                63 of 84
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1760   Instruction Processing




1761
1762

1763   C3     Architecture Concepts
1764
1765   Concepts
1766      1. State Machine
1767      2. Subroutines
1768      3. “Cognitive State Machine”
1769

1770   C3.i   State Machine
1771   Module States
1772   The following diagram illustrates all the various states that the module can be in:
1773




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                                                  P07202
1774
1775
1776   It illustrates that upon booting the motor module will do a built in self test (BIST) and report
1777   an error if something is wrong. If it successfully boots it can be initialized with certain
1778   parameters (e.g wheel size) and will report an error it that initialization fails. Upon success
1779   it will enter a ready state where it can receive commands and execute them.
1780
1781   Running States




1782
1783   *note that the system must either be fast enough to give the appearance that turning and
1784   accelerating occur simultaneously or this state machine must be expanded to include such a
1785   combination state.

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1786
1787   Implementations
       Hardware                                      Software
       FPGA                                          coded with ASM, c, c++, or java
                                                     execute on Stamp, EPIC, or PC/104
                                                     board

       Pros:                                         Pros:
                  Reliability                                   Scalability
                  Power Consumption
                                                     Cons:
       Cons:                                                     Cost
                  Scalability                                   Power Consumption
                  Capabilities
1788

1789   C3.ii Device Drivers
1790   No concepts of states; simply provide driver subroutines which implement the various
1791   commands: controlling motor/motor controllers; signal processing; and data acquisition.
1792
1793   Potential Modes
1794         Polling
1795         Interrupt
1796
1797   Pros:
1798              Ease of implementation
1799              Cost
1800
1801   Cons:
1802              More difficult for the customer to use
1803
1804

1805   C3.iii “Cognitive State Machine”
1806   Motor module posses “awareness” of self. Rather than issuing commands and directly
1807   instructing the processor, the system is given a „request‟. From there the software decides
1808   how to execute it by going through a series of cognitive states:
1809
1810   IDEA (what is the request?)
1811   PLAN (how can I accomplish the request?)
1812   PROGRAM (what pulses, signals, etc. are needed to do this?)
1813   EXECUTION (output/dispatch the necessary pulses/signals)
1814   MOVEMENT (the desired movement is optimally performed)
1815
1816   Pros:
1817              Easy for customer to use since it handles all complex processing
1818              Modularity
1819              Capabilities
1820
1821   Cons:
1822              High component and development costs
1823              Complexity means high risk for reliability issues


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1824
                                    Programming/Processor Concepts
                                           A                  B               C                D
                                   State Machine -    State Machine - Subroutines - SW Cognitive Model -
                                        FPGA          SW + Medium        + Basic Proc    SW + Adv Proc
                                                            Proc
                                   Rating Weighted Rating Weighted Rating Weighted Rating Weighted
       Selection Criteria   Weight           Score              Score           Score            Score
       Scalability           17.0%       3      0.51        4      0.68     4       0.68     4      0.68
       Usability              9.5%       4      0.38        4      0.38     2       0.19     5     0.475
       Reliability           15.0%       5      0.75        4        0.6    4        0.6     2        0.3
       Modularity            13.0%       4      0.52        4      0.52     3       0.39     5      0.65
       Capabilities          12.5%       3     0.375        4        0.5    3     0.375      5     0.625
       Manufacturability     11.0%       4      0.44        4      0.44     4       0.44     3      0.33
       Development Cost       2.5%       4        0.1       3     0.075     4        0.1     1     0.025
       Component Cost        12.0%       4      0.48        3      0.36     4       0.48     1      0.12
       Power
       Consumption           2.5%         5    0.125       3    0.075       4       0.1       3    0.075
       Durability            5.0%         4       0.2      4       0.2      4       0.2       4       0.2
                        Net Score         3.88             3.83             3.555             3.48
                            Rank            1                2                3                 4
                Continue?                 Yes*             Yes*              No                No
1825
1826   *Performance testing is required. Performance is not included on this chart because without
1827   quantifiable metrics the rating would be too subjective. However, it is possible that with that
1828   added category may make the ultimate decision.
1829
1830   Conclusion
1831   Both implementations of the state diagram are good solutions that afford different
1832   advantages. Most of the advantages of the software implementation could be achieved in
1833   addition to the benefits of the FPGA if a combination microprocessor and FPGA board was
1834   used. Cost considerations will be the ultimate limiting factor on that; however, necessary
1835   performance will also contribute.
1836
1837   To estimate the performance necessary considering dependencies:
1838          #ops needed to execute each command
1839          #relative frequency of each commands
1840          #minimum processing time required to:
1841                 Mediate communications
1842                 Condition data signals
1843                 Maintain desired precision of motor output
1844          time required for delays, overhead, etc.
1845
1846   Elaborating on these to include system parameters yields:
1847
1848   bits needed for motor control velocities:
1849   #signals = (Vmax – Vmin) / precision
1850
1851   For example, if 4.5 m/s is desired with a .1 m/s precision then (4.5 – 0) / .1 = 45 (or, with
1852   a bit for direction, 90) Thus approximately 7 bits is needed.
1853


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1854   For the sensors, the equation is similar: #bits is function of the range and precision of the
1855   sensor.
1856
1857   The data needed for the encoding is: target + instr. code + params …
1858
1859   Lastly, if the cycles needed for the fetching, decoding, execution are Tx, Dx, and Ex
1860   respectively then:
1861
1862   Processing lag = Tx + Dx + Ex / clk. freq.
1863
1864   Companies/Manufacturers:
1865   www.altera.com
1866   www.xylinx.com
1867   www.atmel.com
1868   www.oopic.com

1869   C4     Communication Protocols
1870   RS-232, 422, and 485 are most commonly used serial communication way but mostly used
1871   for communicating between two modules or peripherals. The noise immunity level for RS-
1872   232 is low since it is unbalanced protocol comparing to RS-422 and 485 which use a pair of
1873   wires for Rx and Tx signals to improve the noise immunity.
1874        Both RS-422 and 485 can be connected to more than one device simultaneously.
1875        maximum distance for these devices is very good and they are useful for low cost
1876          implementation
1877        cannot be used for intercommunication purposes within the devices because of their
1878          low speed and high voltage requirements.
1879
1880   The most commonly used communication protocols used for communicating between the
1881   devices e.g. microprocessors or DSPs are I²C and SPI. I²C is introduced by Philips Inc. The
1882   power requirement for I²C is very low to meet the low noise margin requirements. The
1883   implementation of I²C is very simple. Regardless of how many slave units are attached to
1884   I²C bus, there are only two data lines that are used for all devices, which reduces the cost
1885   and complexity of the circuit. This mechanism is complicated as only two data lines are used
1886   for all devices; each device has its separate address.
1887         I²C bus can support up to 3.4 Mbps of data transfer.
1888         I²C has built in collision detection, 10-bit addressing, multi-master support and data
1889            broadcast.
1890         One of biggest drawback of I²C is the use of only two data lines presents additional
1891            complexity of handling the overhead addressing and acknowledgments.
1892         I²C does not support bidirectional data transfer at the same time. It can be either
1893            transmitting the data or receiving it.
1894




1895
1896                                     Figure1: I²C Configuration
1897


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1898   SPI is serial communication bus developed by Motorola. It is a full- duplex protocol which
1899   functions on the master-slave paradigm that is ideally suited to data streaming applications.
1900   SPI requires four signal lines, twice as much of I²C, which includes clock and slave select
1901   additional to the two data transferring lines.
1902       The full duplex allows transmitting and receiving of data to occur at the same time,
1903          feature SPI is very useful for communication betweens two DSPs and/ or
1904          microprocessor.
1905       Like I²C the power requirements for SPI is also very low to meet the low noise
1906          margin requirements.
1907       The maximum speed for SPI is more than 10 Mbps.
1908
1909   Because of the master-slave concept of the SPI bus, each slave has its own select signal
1910   which can some times lead to the more complex circuit design in terms of more traces.
1911   Unlike I²C, SPI does not have a specific high level protocol, which means that there is
1912   almost no over head.




1913
1914                                   Figure 2: SPI Configuration
1915
1916
1917   The comparison of the above protocols is given in the chart below.
1918
1919                             Table1: Pugh Chart for different protocols
                 Features            Weight    RS-232 RS-422 RS-485 I²C             SPI
       Data transfer Rate (Kbps)      15%         2          3        3       4      5
            Max. Distance(ft)         15%         3          4        4       2      2
       Bidirectional at same time     15%         4          3        3       3      5
            Max. No. of Bits          10%         3          3        3       4      5
         Implementation Ease          10%         2          2        2       4      3
            Noise Immunity            10%         2          3        3       4      4
                Reliability            5%         2          2        2       4      5
                Scalability            5%         2          3        4       4      4
           Development Cost           2.5%        2          2        2       5      5
            Component Cost            2.5%        2          2        2       4      5
          Power Consumption           7.5%        2          2        2       4      4
                Durability            2.5%        4          4        4       3      3
                                   Net Score     2.5       2.75      2.8    3.75   4.25
                                      Rank        5          4        3       2      1
                                   Continue?     No         No        No    Yes*   Yes*
1920




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                                                 P07202
1921    Because of the nature of our system, SPI is more suitable to use comparing to I²C, as our
1922    system requires high data transfer rate, sending and receiving of data at the same time for
1923    feedback system and communication between different types of devices.
1924
1925    References:
1926    www.embedded.com
1927    http://www.mct.net/faq/spi.html
1928    http://www.epanorama.net/links/serialbus.html
1929
1930    Risk Assessment
1931    Many of the risks for the electrical subsystems are shared by the microprocessor subsystem.
1932    This is especially true if the devices are integrated so that one board is responsible for the
1933    control and processing duties. There are; however, three very important risks specific to the
1934    microprocessor/programming subsystem: the device lacks the power needed to perform all
1935    required duties, the instruction set is not fully compatible with the P07302 controller board,
1936    and the bus is not capable of handling the transmissions.
1937
1938    Performance
1939    The chosen device must be capable of meeting the minimum demands: fetching, decoding,
1940    and delegating/executing instructions; monitoring and conditioning sensor data signals; and
1941    possibly directly handling the control functionality. However, cost is a major concern so it
1942    will suffice to significantly overestimate what is required. In order to make an accurate
1943    determination, a processing model will be created that can be used to estimate the
1944    requirements.
1945
1946    Incompatibility
1947    It is a necessity that the instructions implemented by the P07302 team are supported by
1948    this module. Achieving this requires inter-team collaboration and the establishment of a well
1949    defined encoding scheme and protocol
1950
1951    Insufficient Bus
1952    A bus that cannot support the bandwidth and communication requirements will be a
1953    significant bottleneck for the module. Avoiding this issue requires a thorough analysis of all
1954    devices that will share the bus and their transmission requirements. Using these,
1955    calculations can be made to characterize these minimum requirements. Additionally,
1956    simulation of communications between devices can be done to determine whether the bus
1957    needs to be bidirectional, support interrupts, etc.
1958


1959    VIII.              Risk Management
1960
 Risk   Corresponding        Description of Risk      Probability     Impact     Importance Classification         Mitigation Strategy
  ID       Spec #'s                                     (0 - 1)     (low, med,
                                                                       high)
  1       10, 14, 22     Asynchronous module speeds       0.3         med            1.5    Technical        Make sure bus time is budgeted
                                                                                                             Modules must respond
                                                                                                             identically
                         Interfacing with data
  2       18, 23, 26     communication protocol           0.4         high            4     Technical        Support/ integration circuitry
                                                                                                             Purchase of compatible parts
                         Speed encoder feedback
  3     10, 11, 14, 22   failure                          0.1         med            0.5    Safety           Purchase a durable part


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                                                                P07202
                                                                                              Interrupt for lack of signal
                                                                                              Use of filters on susceptible
4          most         Noise susceptibility           0.5         high    0     Technical    signal lines
                                                                                              Use of durable wiring and
                                                                                              interconnects
                                                                                              Proper grounding throughout
                                                                                              system
                        Transient power spikes (back                                          Proper grounding throughout
5          most         emf)                           0.3         high    3     Safety       system
                                                                                              Power isolation for delicate
                                                                                              circuitry
                                                                                              Placing heatsinks on necessary
6      18, 14, 19, 20   Overheating components         0.7         med    3.5    Technical    components
                                                                                              Keeping circuitry in open air
                                                                                              spaces
7        15, 16, 17     Battery chemical leak          0.05         low   0.05   Safety       Place battery low in the system
                                                                                              Keep it stable with necessary
                                                                                              restrains
     12, 14, 18, 20, 22,                                                                      Pre-determine necessary
8            23          Insufficient microprocessor   0.4         high    4     Technical    computational power
                                                                                              Pre-determine the input/output
                                                                                              signals required
9          33, 34       Inter-group communication      0.4          low   0.4    Technical    Choose a unanimous structure
                                                                                              Use interfacing devices to bridge
                                                                                              protocol
                                                                                              Use a part capable of >100 W
10       10, 14, 18     H-bridge Failure               0.1         med    0.5    Technical    power consumption
                                                                                              Use h-bridges in parallel to
                                                                                              distribute power
11         most         Long-lead items                0.2         med     1     Logistical   Order parts in advance
                                                                                              Use COTS products
                                                                                              Test and determine final circuitry
12         most         PCB layout                     0.9         high    9     Logistical   as quick as possible
                                                                                              Utilize tools on campus
                                                                                              Hand solder components to save
                                                                                              money
                                                                                              Select individual components as
13           -          Long part lead times           0.5         High    5     Schedule     soon as possible
                                                                                              Order individual components as
                                                                                              soon as possible
                                                                                              Utilize most common COTS
                                                                                              parts, as they are more easily
                                                                                              attainable and readily available
                                                                                              Have as many alternate vendors
                                                                                              lined up as possible
                        Torque output not
                        capable of climbing the                                               Check motor calculations with
14        1,3,4,10      max incline                    0.1         Low    0.1    Technical    professors and P0720
                                                                                              Include Service Factor in motor
                                                                                              selection
                        Braking safely
                        (minimum distance and                                                 Check braking calculations with
15    1,510,14,18,19    fail-safe)                     0.25        High   2.5    Safety       professors and P07201
                                                                                              Characterize Dynamic braking
                                                                                              through baseline prototyping
                                                                                              Utilize mechanical power-off
                                                                                              brake
                        Packaging in small,                                                   Minimize size of all individual
16         8,13         modular space                  0.5         Med    2.5    Technical    components


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                                                              P07202
                                                                                           Packaging minimization through
                                                                                           3D modeling
                                                                                           Standardize mounting with
                                                                                           P07201
                        Drivetrain Failure
  17      1,2,32        (static and fatigue)        0.1         Low   0.1    Reliability   DME Calculations
                                                                                           Correct choice of safety factor
                        Steering Failure (static,
  18   1,2,6,20,21,32   fatigue, and torque)        0.25        Med   1.25   Reliability   DME Calculations
                                                                                           Correct choice of safety factor
                                                                                           Motor torque requirement
                                                                                           calculations
                        Moving Robot with                                                  Utilize clutch (power-on or
  19         -          power off                   0.75        Low   0.75   Technical     manual)
                                                                                           Backup plan- disconnect
                                                                                           transmission via set screw or
                                                                                           equivalent
                                                                                           Work with Dave Krispinsky in
                        Characterize motor in                                              and develop dyno mounting
  20         -          timely fashion              0.5         Low   0.5    Schedule      technique
                                                                                           Generate and develop alternate
                                                                                           characterization techniques
                        Weight (impact on                                                  Monitor and sum component
  21   1,2,3,4,5,6,9    torque requirement)         0.25        Low   0.25   Technical     weights
                                                                                           Verify total with motor
                                                                                           calculations before ordering
                                                                                           motor
                                                                                           Include motor Service Factor
                                                                                           Quantify heat output with
  22        23          Motor Temperature           0.25        Med   1.25   Reliability   baseline characterization
                                                                                           Backup plan- add a cooling fan
1961
1962




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                                                           P07202
1963   IX.   Schedule
1964




1965




                        73 of 84
                        P07202
1966
1967


1968   X.           Appendix
1969
1970   X.1 Calculations
1971
1972   Key:
1973   m=mass
1974   g= acceleration due to gravity
1975   f=coefficient of rolling resistance
1976   incline angle
1977   N= number of driven wheels
1978   d=wheel diameter
1979   GR= gear ratio
1980   = transmission efficiency
1981   vmax = max velocity
1982   vmin = min velocity
1983   a= acceleration
1984   V=voltage
1985   R=resistance
1986
1987   Motor Calculations:
1988
1989   Max Torque Requirement
1990   F friction  m  g  f  Cos


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                                             P07202
1991   Fweight  m  g  Sin
1992   Ftotal  F friction  Fweight
1993   Fwheel  Ftotal  N
                         d
1994   Twheel  Fwheel 
                         2
                Twheel
1995   Tmotor 
                GR 
1996   Min Torque Requirement
               v
           v 1997
       a  max min
              1998
               t
              1999
2000   Ftotal  m  a
2001   Motor Speed
                  vmax  60
2002   nwheel 
                    d
2003   nmotor    nwheel  GR
2004   Power
2005   P  Ftotal  vm ax
2006
2007   Braking Calculations
2008
2009   Power off
2010   Tpow  Tstatic  0.93
                   Tpow
2011   Fwheel 
                 d 2
2012   Fbrakes  Fwheel  N
2013   Fweight  m  g  Sin
2014   Ftotal  Fbrakes  Fweight
             Ftotal
2015   a
              m
                      2
                 vm ax
2016   d stop 
                  2a
2017
2018   Dynamic Braking Calculations
                V2
2019   Pbrakes 
                  R
               P
2020   Tdyn  brakes
                  2
               n
                  60
2021   Twheel  0.93  Tdyn  GR
2022
2023   Combined

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                                       P07202
2024   Tcombined  Tpow  Tdyn
2025
2026   Overall System
                         2
                v
2027   d stop  m ax
                2a
2028   Ftotal  m  a
2029   Fwheel  Ftotal  N
                         d
2030   Twheel  F 
                         2
2031
2032   Overall System w/ Incline
2033   Fweight  m  g  Sin
2034   Fbrakes  Ftotal  Fweight
2035
2036   Inertial Effects
                       1
2037   I sol .cyl.      m  v2
                       2
              a
2038   
              r
2039   Tinertia  ( I   )
2040
2041   X.2 P07202 Project Readiness Package
2042   This document describes and serves as a template for preparation of a Project Readiness Package.
2043   The objective of the Project Readiness Package is to document:
2044          Customer needs and expectations
2045          Project deliverables (including time frame)
2046          Budget
2047          Personnel / organizations affiliated with the project

2048   It will serve as the primary source of information for students necessary during Phase 0 (Planning) to
2049   develop a SD I plan and schedule including specific deliverables and due dates. The Project Readiness
2050   Package will also support Faculty evaluation of project suitability in terms of depth, scope, and student /
2051   faculty resources by discipline.


2052   Administrative Information
2053   Project Name
2054   Motor Module - Robotic Platform 100 kg (RP100)
2055   Project Number
2056   P07202
2057   Track
2058   Vehicle Systems Technology
2059   Start Term
2060   2006-1


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                                                        P07202
2061   End Term
2062   2006-2
2063   Faculty Consultant
2064   Jeff Webb, Prof. George Slack
2065   Faculty Guide
2066   Dr. Wayne Walter
2067   Primary Customer
2068   Dr. Hensel (ME Dept. Head)
2069   Secondary Customers
2070   Dr. Crassidis (ME), Dr. Hu (CE), Dr. Yang (CE), Dr. Sahin (EE), and Dr. Walter (ME)
2071   Customer contact information
2072   Dr. Edward Hensel, PE
2073   Professor and Head
2074   echeme@rit.edu
2075
2076

2077   Project Overview
2078   The mission of this student team is to develop a fully functional, scalable motor module subsystem for use
2079   on the 100 kg (RP100) robotic vehicular platform. The team must provide complete documentation of the
2080   analysis, design, manufacturing, fabrication, test, and evaluation of this subsystem to a level of detail that
2081   a subsequent team can build upon their work with no more than one week of background research.

2082   Staffing Requirements
                        Number of
       Discipline                                                    Skills Required
                         Students
                                       Ability to work with microcontrollers, DC motor controllers, encoders,
           EE       4                  power supplies et. al; and their interaction with each other and mechanical
                                       systems.
                                       Ability to characterize power transmission within mechanical systems, and
          ME        2
                                       to work with the interaction between electrical and mechanical systems.
          CE        0                  N/A
          ISE       0                  N/A
         Other      0                  N/A


2083   Continuation, Platform, or Building Block Project Information
2084   The mission of the Vehicle Systems Technology Track of projects is to develop a land-based, scalable,
2085   modular open architecture, open source, full instrumented robotic/remote controlled vehicular platform for
2086   use in a variety of education, research & development, and outreach applications within and beyond the
2087   RIT KGCOE. The collection of projects should use an engineering design process to develop modules
2088   and subsystems that can be integrated by subsequent senior design teams. This project, P07200, serves
2089   as the foundation or starting point for a series of senior design projects.
2090   The mission of each student team contributing to this track is to develop or enhance a particular
2091   subsystem for a robotic vehicular platform, and provide complete documentation of the analysis, design,
2092   manufacturing, fabrication, test, and evaluation of each subsystem to a level of detail that a subsequent
2093   team can build upon their work with no more than one week of background research.



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                                                         P07202
2094   This roadmap will be initiated during the Fall Quarter, 2006-1, with three closely related projects.
2095   Additionally, these three projects have significant overlap with projects from the Aerospace Systems and
2096   Technology Track (P07100), and the Systems and Controls Track (P07300).

2097   Principle Sponsor or Sponsoring Organization
2098   Gleason Foundation


2099   Detailed Project Description
2100   Customer Needs
2101          The motor module must be scalable, and specificaly shown to have the ability to be scaled up to
2102        1000kg.
2103          The motor module must be modular (Modules must be inter-changeable between platforms of
2104        same scale)
2105          The motor module must be open architecture (All COTS components must be available from
2106        multiple vendors)
2107          The motor module must be open source (All drawings, programs, documentation, data, etc. must
2108        be open source published in standard formats)
2109          The motor module must be manufacturable in lots as small as one and as large as 10.
2110          The motor module shall NOT be designed assuming that it is targeted for a commercial product.
2111          The motor module design shall be available for use and adoption by other commercially oriented
2112        SD teams.
2113          The motor modules of the robotic platform shall be re-configurable into many different
2114        configurations. For example, it should be EASY and LOW COST to take expensive drive
2115        components for individual wheel drives and assemble them into 3-wheel, 4-wheel, and 6-wheel
2116        configurations, with the number of driven wheels ranging from 1 to 6.
2117          The motor modules must be able to be constructed as either idler or driven modules. They must
2118        also be easily converted from idler to driven and back.
2119          The results of this platform should increase the reputation and visibility of the RIT SD program
2120        and our robotics technology "skill level" on a national basis.
2121          This robotic platform must be clearly impressive to any student, parent, engineer, mentor, or
2122        individual familiar with the US FIRST robotics competition.

2123   Customer Deliverables
2124   Design, build, and fully characterized working prototypes of 4 idler modules and 3 powered motor
2125   modules. See the "Detailed Course Deliverables" section for more specifics.

2126   Customer and Sponsor Involvement
2127   The team will be expected to carry out the vast majority of their interactions with the Team Guide (Dr.
2128   Walter), and the teaching assistant (Jeff Webb). Dr. Hensel (The sponsor and customer) will be available
2129   for a series of meetings during the course of the project. Dr. Hensel will meet with a group of teams
2130   during the beginning of SD1 to lay out common goals, objectives, and philosophies for the sequence of
2131   projects being sponsored by the Gleason Foundation gift to the ME Department. It is anticipated that Dr.
2132   Hensel will meet with the team (or multiple related teams) for 2 hour meetings approximately 4 times
2133   during senior design 1, and twice during senior design 2. Dr. Hensel will participate with team
2134   communications electronically, through the web site as well.

2135   Regulatory Requirements

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                                                       P07202
2136          The design shall comply with all applicable federal, state, and local laws and regulations. The
2137        team's design project report should include references to, and compliance with all applicable federal,
2138        state, and local laws and regulations.
2139          The design shall comply with all applicable RIT Policies and Procedures. The team's design
2140        project report should include references to, and compliance with all applicable RIT Policies and
2141        Procedures.
2142          Wherever practical, the design should follow industry standard codes and standards (e.g.
2143        Restriction of Hazardous Substances (RoHS), FCC regulations, IEEE standards, and relevant safety
2144        standards as prescribed by IEC, including IEC60601). The team's design project report should
2145        include references to, and compliance with industry codes or standards.

2146   Project Budget and Special Procurement Processes
2147          The total development budget for the Vehicle Systems Technology Track is not anticipated to
2148        exceed $15,000 during AY06-07 and 07-08 for first article prototypes of each project. The
2149        distribution of this amount between projects in the roadmap is left to the discretion of the
2150        Coordinator.
2151          The cost to manufacture subsequent copies of the final design, sub-assembly, or part should
2152        decrease with increasing volume.
2153          The cost to manufacture subsequent copies of the final design, sub-assembly, or part should
2154        decrease with decreasing levels of instrumentation, but shall remain capable of being retro-fitted
2155        with instrumentation after initial manufacturing.
2156          The cost to manufacture subsequent copies of the final design, sub-assembly, or part should be
2157        borne by the team, faculty member, research project, company, or department desiring to use the
2158        item for their research and development work.
2159          The design team is not expected to account for the nominal labor costs of RIT shop personnel as
2160        long as their time commitment does not greatly exceed that of other typical SD projects.
2161          The design team is not expected to account for the nominal labor costs of TA's, Faculty, or other
2162        staff assigned to assist and guide then team, as long as their time commitment does not greatly
2163        exceed that of other typical SD projects.
2164          The design team is not expected to recover the investment costs associated with the platform
2165        development.

2166   Intellectual Property Considerations
2167   Everything associated with this project is public domain.

2168   Engineering Specifications
2169   Motor Module Specifications
2170         The motor module must be capable of integrating onto a platform with future features and
2171       projects such as data acquisition, data logging, advanced user interface, power and control of
2172       peripherals, and autonomous control.
2173         The motor module must be designed in such a way as to be easily modified for future work with
2174       active steering.
2175         The motor module must be easy for a third party to understand, use, and modify.
2176         The motor module must have some way to determine the angular speed and total number of
2177       rotations of the motor (e.g. an encoder).
2178         The speed of the wheel must be easily controlled.
2179         The preferred motion control technology is drive by wire.
2180         Each motor module must be addressable and able to "talk" with a central processor.



                                                        79 of 84
                                                        P07202
2181          A braking system must be included. The team will research braking systems and determine
2182        requirements. These requirements will mostly be driven by safety considerations for humans,
2183        facilities, and the motor modules themselves (in that order). Team decisions must be approved by
2184        the coordinator.
2185          The preferred energy source is rechargeable DC battery.
2186          Each module will have a steady-state run time of at least one hour.

2187   100kg Robot Specifications
2188   The motor modules must be able to meet the following requirements when used together on a platform:
2189         The range of the robotic platform shall be the entire second floor of the James E. Gleason
2190       Building, RIT Bldg #09.
2191         The platform must be functional in the two different configurations shown below.




2192
2193   Figure 1: Prototype Configuration Requirments
2194          The design enveloped for relevant engineering specifications for this platform are tabulated below.


                                             Table 1: Tradeoff Assessment
                               Tare Weight        Payload            Speed         Turning            Remote
       Model      Size (m)
                                   (kg)         Capacity (kg)        (m/s)        Radius (m)         Range (m)
                0.60 x 0.75
       R100                    40              100                 4.5          1.00               60
                x 0.50


2195   Safety Constraints
2196         The top speed of the vehicular platform should be scaled with its size, and should be safe for its
2197        operating range and environment.
2198         The vehicular platform shall have on-board and remote "kill switches".
2199         Human safety takes precedence over all other design objectives.
2200         Building and facilities safety takes precedence over robotic vehicle platform damage.
2201         The vehicle should be robust to damage by inexperienced operators.


2202   Detailed Course Deliverables


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                                                       P07202
2203   Note that this level describes an absolute level of expectation for the design itself, and for the hardware.
2204   However, the student team must also meet all requirements related to analysis, documentation,
2205   presentations, web sites, and posters, etc. that are implicit to all projects.
2206   See Senior Design I Course Deliverables for detail.
2207   The following tasks should be completed by the end of SD1:
2208          Build the baseline system provided by the Teaching Assistant.
2209          Fully characterize the baseline system. This will include, but is not limited to:
2210         o         Current
2211         o         Speed
2212         o         Torque
2213         o         Efficiency
2214          Design a new motor module system.

2215   The following tasks should be completed by the end of SD2:
2216     Deliver working prototypes of 4 idler modules and 3 powered motor modules.
2217     Fully characterize the prototypes in the same manner as the baseline system.


2218   Preliminary Work Breakdown
2219   The following roles are not necessarily to be followed by the team. It is merely to justify the number of
2220   students from each discipline. The student team is expected to develop their own work breakdown
2221   structure, consistent with the general work outline presented in the workshop series at the beginning of
2222   SD1. However, the customer requests a level of detail NO GREATER than weekly tasks to be completed
2223   by each student team member for the benefit of the other team members. The customer DOES NOT
2224   request any level of detail finer than one-week intervals, but will assist the team members if they wish to
2225   develop a finer level of detail to support their own efforts.
2226   ME:
2227    1.     Powertrain (i.e. motor, transmission, etc.).
2228    2.     Yoke and any other necessary hardware not previously mentioned.

2229   EE:
2230    1.     Microprocessor hardware and integration, sensing, and overall architecture.
2231    2.     Software.
2232    3.     Power electronics (i.e. motor controller, etc.).
2233    4.     Power (i.e. batteries, AC/DC converters, etc.).


2234   Grading and Assessment Scheme
2235   Grading of students in this project will be fully consistent with grading policies established for the SD1 and
2236   SD2 courses. The following level describes an absolute level of expectation for the design itself, and for
2237   the hardware. However, the student team must also meet all requirements related to analysis,
2238   documentation, presentations, web sites, and posters, etc. that are implicit to all projects.
2239   Level D:
2240   The student team will build and fully characterize the baseline robot kit provided by the Teaching
2241   Assistant. The student team will deliver cost effective working motor module prototypes, capable of
2242   controlled motion. The prototypes will also be fully characterized.
2243   Level C:
2244   The student team will deliver all elements of Level D PLUS: The motor module prototypes will meet all
2245   customer specifications. The prototypes developed will be 100% open architecture and open source.
2246   They will use no proprietary components, only COTS components available from multiple manufacturers.

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                                                         P07202
2247   Level B:
2248   The student team will deliver all elements of Level D and C PLUS: The motor module prototypes will show
2249   quantitative improvements over the baseline robot kit for the customer's application. There will also be
2250   marked improvement over the baseline robot kit in the areas of control and user interface.
2251   Level A:
2252   The student team will deliver all elements of Level D, C, and B PLUS: The motor module prototypes will
2253   exceed the baseline robot kit in every aspect asked for by the customer. The prototypes will be
2254   completely ready for "plug and play" use on a robot platform.


2255   Three-Week SDI Schedule
2256   This project will closely follow the three week project workshop schedule presented in SD1. See the
2257   Course Calender for Details.
2258   In addition, the following tasks should be completed ASAP:
2259   1. Go over the information on the edge website, from the Design Project Management Robotics Platform
2260   Roadmap, and in the Preliminary Information binder.
2261   2. Build the kit provided by the Teaching Assistant.
2262   3. Test and fully characterize the equipment in the kit.
2263   4. Compare the results with the other Vehicle Systems Technology Track teams.


2264   Required Resources

                                         Faculty
          Item         Source                 Description                 Available
       Prof. Walter    ME         Faculty Guide/Coordinator/Mentor        Yes
       Prof. Hensel    ME         Customer                                Yes
       Prof. Slack     EE         Technical Consultant                    Yes

                                   Environment
           Item             Source            Description         Available
       Robotics Lab     ME 09-2230       Work Space/Storage       Yes
       Sr Design Lab    EE 09-3xxx       Work Space               Yes
       ME Shop          ME 09-2360       Parts Fabrication        Yes

                                         Equipment
            Item                     Source                 Description       Available
       DC Motor Dyno        EE Electric Machines Lab     Characterization     Unknown
       Power-supply         EE Department                Used for Testing     Unknown
       Desktop PC           Throughout                   Programming          Yes
2267   The team members will be expected to procure the materials needed for the project, excluding the
2268   following:
2269

                                               Materials



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                                                           P07202
                 Item               Source               Description        Available
       Super Droid Robot ATR   Teaching Assistant   10kg payload example    Yes
       IFI Robotics Kit        Teaching Assistant   100kg payload example   Yes
2270
2271
2272


2273   XI.Change History
2274
       Change                                                          Changed By       Date

2275
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