ELEC 490289 Proposal by epmd

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									             ELEC 490/2/8/9 Proposal



REMOTE CONTROL OF AN EXCAVATOR ROBOT
         SECOND GENERATION




                 Submitted By:


                   Group 32
                Shamir Charania
                  Noel Johnston
                Tavis MacCallum


               Faculty Supervisor:


            Dr. Keyvan Hashtrudi-Zaad
                            EXECUTIVE SUMMARY:


This project proposal describes the design and modification for a commercially available
excavator toy to improve control and to enable wireless monitoring of its bucket position
and contact forces. A toy excavator will be purchased and retrofitted with rotation sensors
on the boom and stick part of its arm for gathering data on the placement of the excavator
arm, as well as two encoders on the tread tracks for gathering data on the current position
of the excavator in the test space. A motor driver board will be added to control the
excavator motors and a microprocessor will be added to control the overall system and
communicate via wireless transmitters to a user at a computer. The user will control the
excavator using two linear joysticks. A diagram of the system is shown in Appendix A.


The user of this excavator will be able to make use of coordinated motion to move the
bucket portion of the excavator arm accurately along two axes of motion. Two rotation
sensors will read the position of the angles of the boom and stick portions of the
excavator arm, and send the data to the computer. This angle data will be used to
calculate, in real time, the bucket in Cartesian coordinates.


A graphical simulation will be built so that the user will be able to keep track of the
excavator’s position and that of the components of the excavator arm. Angle data
provided by the rotation sensors will be used to calculate the current position of the
boom, stick, and bucket in 3D space. The data from the encoders will be used to keep
track of the movement of the excavator. From the encoder data, a history of where the
excavator has moved can be created, and the current position of the excavator in 3D
space can be displayed to the user. Numerical values of the angles of the boom and stick
will be presented to the user, as well as values showing the force acting upon the load in
the bucket. Feedback from the motor driver board will be used by the microprocessor to
calculate these values.


This project is expected to take 8 months to reach completion and cost approximately
$400.
                      Table of Contents


1. Introduction……………………………….…………………………………………….1
    1.1 Purpose...………………………………………………………………………1
    1.2 Work Objective..……………………………………………………………....1
    1.3 Scope of Project……………………………………………………………….2
2. Functional Description…………………………………………………………….……2
    2.1 General …………………………………………………………..……………2
    Figure A: An overall diagram of the system………………………………………3
    2.2 Interface Specifications…………………………………………………..……4
    2.3 Performance Specifications…………………………………………….……..4
3. Design and Production Approach………………………………………………….…...5
    3.1 Process………………………………………………………………………...5
    3.2 Division of Labour………………………………………………………….…6
4. Verification of Correctness……………………………………………………………..6
5. Resource Requirements………………………………………………………………...7
    5.1 Schedule…………………………………………………………………….....7
    5.2 Materials and Other Resources…………………………………………...…...8
6. Conclusion………………………………………………………………………...……8
7. References………………………………………………………………………………9
Appendix A –The Entire System….…………………………………………...………...10
Appendix B - Coordinated Motion………………………………………………………11
1.0 Introduction
Using skills learned from electronics, digital systems, microprocessor design, computer
graphics, signals and systems, and robotic-related courses, this project involves
modifying an excavator that can be controlled remotely. This modification will enhance
the control of the excavator by implementing wireless control, switching physical control
to two joysticks, displaying data relevant to the control of the excavator in a useable
interface, and by changing the movement range of the excavator arm by use of
coordinated motion.


1.1 Purpose
This document will summarize the Elec 490 project being proposed by group 32.


1.2 Work Objective
The purpose of our project is to, using existing work, build a larger, more functional
excavator that can be viewed and controlled wirelessly.


The motivation for this project comes from the risk of working in dangerous situations.
With a wirelessly controlled excavator, diging in hard to reach places, or harsh
environments can be completed with ease and minimal risk to the operators .


The solution proposed involves the modification of an excavator with a control board.
The excavator would have sensors to read the position of the boom and stick
(components of the arm of the excavator), and the distance traveled. In addition, the
excavator would have sensors to monitor the forces acting upon the bucket portion of the
excavator arm. This information can then be transmitted wirelessly to a computer where
a graphical simulation would relay the information to a user. The user would be able to
control the robot using two joysticks and be able to see the result in real time.




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1.3 Scope of Project
The first part of this project will involve acquiring a larger excavator. It was determined
that a larger excavator is needed to hold all the required circuitry. In addition to
modifying the larger excavator, the following tasks will be undertaken:
      The PCB board for driving the excavator motors will be redesigned so that it is
       smaller and more efficient.
      The graphical interface will be improved so that it is fully functional and shows
       the movement of the excavator itself, with respect to its original position, as well
       as the movement of the back-hoe. This interface should also be able to calculate
       the forces acting on the bucket by the environment.
      Two-way wireless communication will be developed, so that the excavator can be
       controlled wirelessly by two joysticks via computer.
      Coordinated motion, an interpretation of signals to control motion in a Cartesian
       mapped space, should be developed (see Appendix B for graphical
       representation). Useful information on this topic can be found from reference
       number [4].


2.0 Functional Description
When finished, the Excavator Robot will be able to transmit data on its bucket position as
well as its physical position to the user wirelessly. Two linear joysticks, one for the
movement of the excavator and one for the movement of the boom and stick will replace
the control pad. Coordinated motion of the boom and stick will be used to improve the
performance of the excavator arm. Pushing forward on the joystick will move the arm
forward solely in the horizontal axis, while pushing the joystick to the side will move the
arm solely in the vertical axis
2.1 General
A new larger version of last year’s excavator will be fitted with the existing sensors and
either the 68HC11 or the 68HC12. The initial design phase will implement the movement
of the excavator’s treads and arms by the use of a motor driver board (PCB). This board
will take digital control signals from the HC11/12 and convert them to analog signals



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used to control the boom and stick angles as well as the two treads. Each mobile device
(boom, stick, treads) will also have sensors to provide the HC11/12 with their current
angular position. This information will be sent to the HC11/12 as an analog signal,
interpreted by the microcontroller, and then sent to the computer. In the initial phase, the
HC11/12 will be hooked to the PC via the serial port to analyze the input data.


The second phase will involve taking raw output data from the excavator’s sensors and
translating it into data for a 3D graphical user interface. Alongside this development, the
wireless connection will be implemented and tested. There is a possibility that a
PocketPC may be available to aid the development of a wireless connection to the PC,
However, if this is not possible, then a wireless transmitter will be designed and
produced.


The third phase brings all the individual components together. Once the sensors are
known to be functional, and movement of the excavator arm is possible, development of
coordinated motion will be implemented. The end goal will be to have the bucket of the
excavator represented properly in Cartesian coordinates. Using this scheme, pushing
forward on the joystick will move the arm forward solely in the horizontal axis, while
pushing the joystick to the side will move the arm solely in the vertical axis. A diagram
of the complete system is shown in Figure A.




       Figure A: An overall diagram of the system.




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In previous excavator projects, software was developed for the 3D graphical user
interface (GUI). However, the software could only graphically represent the bucket
angles. This year’s project proposes to finish the 3D GUI so that any movement of the
excavator will be properly represented. The proposed software units will consist of:


           1. A computer program that communicates between a standard PC and the
               controllers (joysticks).
           2. HC11/12 programming (in assembly)
           3. A peer-to-peer application to transmit and receive control and sensor
               information.
           4. A computer graphics program that will interpret the sensor information
               from program three to a 3D interface.


2.2 Interface Specifications
The user controls the excavator via two linear joysticks. The joysticks have a full range of
motion, meaning that the harder the user pushes on the joystick, the faster the joints of the
boom and stick will rotate. The user receives information about the positions of the
boom, stick and bucket in the form of angle data through a 3D graphical representation of
the excavator. Furthermore, the computer program will show where the excavator robot
has moved since operation began, as well as the amount of force that is currently being
exerted on the load in the bucket of the excavator.


2.3 Performance Specifications
The excavator’s response should be instantaneous once the user changes the joystick
positions. In terms of the wireless connection, range to the excavator should be small;
the transmitters will be designed for use in a lab setting. The 3D representation of the
excavator will be detailed enough for the 3 main parts of the arm (boom, stick, and
bucket).




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3.0 Design and Production Approach
3.1 Process
A careful reading of the reports of previous years will provide valuable insight. Some
hardware, such as the sensors, and some software, such as part of the 3D GUI, has been
completed in past years, and may be salvageable. It is known that a part of the old motor
driver board is non-functional, and a new H-bridge will have to be purchased. It is
expected that other components will be non-functional, and new sensors or chips will
have to be purchased. If some of the work by past years is salvageable, it will be of great
value, since it would free up the current group to expand the scope of the project, for
example, by adding force feedback to the joysticks.


The choice of using the HC11 over the HC12 is dependent on design specifications.
Given a goal to produce a smaller PCB footprint on the excavator, the smaller HC11
would be ideal. Last year’s project code was too large to fit in the memory of the HC12.
The HC11 has 64Kbytes memory and 32Kbytes of free ram whereas the HC12 has 32KB
memory, and 512 KB free ram [1]. However, the HC12 has an improved A/D with the
use of 8 channel samples at once. The HC11 only has 4 samples at a time [2]. The coding
for the HC12 would be simpler when dealing with the 8 channels as opposed to the code
involved in multiplexing the two 4 channels on the HC11. Given that the current design
has four analog sensors (for boom angle, stick angle and two signals for feedback from
the H-Bridge PCB [3]) then only the HC11 is required. At this time in project
development, the 68HC11 is the favoured microprocessor.


Short group meetings will be held at the beginning of each week to gauge progress and
plan for the week ahead.




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3.2 Division of Labour
Project work will be divided according to whom has the most knowledge and experience
in specific areas of the project. The distribution of work in this project is shown in Table
1.0.


                                          Noel           Tavis         Shamir
Wireless Connection                         P                              S
PCB Design                                  P              S
Integration of Components                   P              S
Coordinated Motion                                         P               S
Documentation/Webpage                       S              P
Computer Programming                        S                              P
Graphics Design                                            S               P
HC11 Programming                                           S               P

Table 1.0 - Work Breakdown Structure



P = primary responsibility
S= secondary responsibility


4.0 Testing and Evaluation
Testing of this excavator robot will entail comparing computed results with measured
values. By performing several different maneuvers, the results generated by the
computer program can be checked with actual measurements. This can satisfy testing for
areas of the project such as determining the displacement in position, and also the
configuration of the back-hoe. As for testing of coordinated motion, a simple test can be
designed and viewed to ensure that the back-hoe moves in the correct axis of motion
given the correct input.




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5.0 Resource Requirements
5.1 Schedule


October 11th


       1. Website for project is created.
       2. Survey of hardware components from previous years completed.
       3. Begin to look for a new excavator.


November 1st


       4. Hardware components from previous years have been tested to confirm that
           they operate correctly.
       5. Decision on what components to keep and what to throw out is made.
       6. Design of all elements of the project finalized.
       7. New Excavator purchased.


December 1st


       8. PCB board completed.
       9. All components constructed and tested individually and integrated into the
           system. System tested with serial communication.


February 1st


       10. 3D Graphic Interface and GUI completed.
       11. Wireless Transmitters completed.


February 15th



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       12. Coordinated Motion completed.


March 1st
       13. Testing of project as a whole.


March 15th
       14. Faulty systems are fixed.
       15. System is refined.
       16. Project completed.


5.2 Materials and Other Resources
       This project will require:
                 Motorola 68HC12 or 68HC11
                 PC with VB and Open GL
                 An excavator toy
                 Lab bench with oscilloscope and multi meter for testing, soldering tools
                 Wireless transmitter or PDA
                 Two linear joysticks


6.0 Conclusion
            Our initiative is to design a wirelessly controlled excavator. In a real-time
system, this excavator will provide live position data to a graphical user interface. The
operator sees updates to the screen and provides control via joysticks. Our main goal is to
implement this functional robot so that it makes use of coordinated motion.




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7.0 References

[1]   Matthew Cole, Lee-Anne Edmunds, Danah Kassabian, (2003-2004). ELEC490
      Project – Control of An Excavator, (Page 9)
      Queen’s University, Kingston, Canada,

[2]   Various authors, (2004). 68HC11 User Reference Manual, [ONLINE]. Available:
      http://www.motorola.com

[3]   Jim Brown, (1998) Brief H-Bridge theory of operation, [ONLINE]. Available:
      http://www.dprg.org/tutorials/1998-04a/

[4]   GÄunter Schreiber and Gerd Hirzinger, (1999) REALTIME COORDINATED
      REDUNDANT MOTION OF A NONHOLONOMIC MOBILE MANIPULATOR -
      DLR Institute of Robotics and Mechatronics, (Page 3) 82230 Wessling, Germany,
      [ONLINE]. Available:
      http://www.morpha.de/download/publications/DLR_RealtimeCoordinated-
      Nonholonomic.pdf




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Appendix A – The Entire System




     Figure A: An overall diagram of the system.




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Appendix B – Coordinated Motion, a Graphical Representation




Figure B: Coordinated Motion requires an endpoint (the bucket) to move in a level plane (diagram by Noel
Johnston).




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