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A COMPARATIVE ANALYSIS OF SPEED CONTROL OF SEPARATELY EXCITED DC MOTORS BY CONVENTIONAL-2

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A COMPARATIVE ANALYSIS OF SPEED CONTROL OF SEPARATELY EXCITED DC MOTORS BY CONVENTIONAL-2 Powered By Docstoc
					INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING
 International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 2, March – April (2013), © IAEME
                            & TECHNOLOGY (IJEET)
ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
Volume 4, Issue 2, March – April (2013), pp. 229-244
                                                                              IJEET
© IAEME: www.iaeme.com/ijeet.asp
Journal Impact Factor (2013): 5.5028 (Calculated by GISI)                 ©IAEME
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        A COMPARATIVE ANALYSIS OF SPEED CONTROL OF
    SEPARATELY EXCITED DC MOTORS BY CONVENTIONAL AND
          VARIOUS AI TECHNIQUE BASED CONTROLLERS

                                         Debirupa Hore*
                (M.Tech Power and Energy systems, B.E Electrical Engineering)
                    *Assistant Professor Electrical Engineering Department
                 KJ Educational Institutes” KJCOEMR Pune Maharashtra India


  ABSTRACT

          This paper presents a comparison of speed control of a separately excited DC motor
  using different types of controllers. Conventional controllers are generally used to control the
  speed of the separately excited DC motors in various industrial applications. It is found to be
  simple and high effective if the load disturbances are small. But during high load or large
  variation of load the AI technique based controllers such as proves to be fast and reliable. To
  control the speed of the motor a step down chopper is also used. The control scheme of the
  motor was tested with convention PI controller following the Fuzzy controller and then
  ANFIS Based speed controller. All the responses were analyzed in MATLAB/SIMULINK
  environment. The simulation results show that the Artificial Intelligence based speed
  controllers gives good performance and high robustness in large load disturbances.

  I. INTRODUCTION

          Development of high performance motor drives is very essential for industrial
  applications. A high performance motor drive system must have good dynamic speed
  command tracking and load regulating response. Depending on the application, some of them
  have fixed speed and some have variable speed. The variable speed drives, have various
  limitations such as poor efficiencies, lower speeds etc. With the advent of power electronics
  today we have variable drive systems which are not only smaller in size but also very
  efficient, highly reliable and meeting all the stringent demands of the various industries of
  modern era. DC motors provide excellent control of speed for acceleration and deceleration.
  The power supply of a DC motor connects directly to the field of the motor which allows for

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precise voltage control, and is necessary for speed and torque control applications. DC
drives, because of their simplicity, ease of application, reliability and favorable cost
have long been a backbone of industrial applications. DC drives are less complex as
compared to AC drives system. DC drives are normally less expensive for low horsepower
ratings. DC motors have a long tradition of being used as adjustable speed machines and a
wide range of options have evolved for this purpose. Cooling blowers and inlet air flanges
provide cooling air for a wide speed range at constant torque. DC regenerative drives are
available for applications requiring continuous regeneration for overhauling loads. AC drives
with this capability would be more complex and expensive. Properly applied brush and
maintenance of commutator is minimal. DC motors can provide high starting torques which
is required for traction drives. They are also used for mobile equipment such as golf carts,
quarry and mining applications. DC motors are conveniently portable and well fit to
special applications, like industrial equipments and machineries that are not easily run
from remote power sources.
        With the advent of thyristors and thyristor power converters the variable voltage to
the dc motor is obtained from static power converters. Phase controlled rectifiers provide
variable dc voltage from constant voltage, constant frequency mains. The static apparatus is
very efficient, compact and has a very good dynamic behavior. It is very easy to provide a
four quadrant drive with slight modifications in the converter. A dc chopper can be used to
obtain a variable voltage from a constant dc voltage. The average value of the output voltage
can be varied by varying the time ratio of the chopper.
II. CHOPPERS
        A DC chopper is a static power electronic device that converts fixed dc input voltage
to a variable dc output voltage. A Chopper may be considered as dc equivalent of an AC
transformer since they behave in an identical manner. As chopper involves one stage
conversion, these are more efficient. Choppers are now being used all over the world for
rapid transit systems. These are also used in trolley cars, battery-operated vehicles, traction-
motor control, and control of induction motors, marine hoists, forklift trucks and mine
haulers. The future electric automobiles are likely to use choppers for their speed control and
braking. Besides, the saving in power, the DC chopper offers greater efficiency, faster
response, lower maintenance, small size, smooth control, regeneration facility and for many
applications, lower cost, than motor-generator sets or gas tubes approaches.

A. PRINCIPLE OF STEP-DOWN CHOPPER (BUCK-CONVERTER) OR CLASS A
  CHOPPER

        A chopper is a high speed ON or OFF semiconductor switch which is consists of
power semiconductor devices, input dc power supply, elements (R, L, C, etc.) and output
load. The average output voltage across the load is controlled by varying on-period and off-
period (or duty cycle) of the switch In fig.1 when chopper CH1 is ON, V0 = and current i0
flows in the arrow direction shown. When CH1 IS OFF, V0 = 0 but i0 in the load continues
flowing in the same direction through freewheeling diode FD. Hence average values of both
load voltage and current, i.e. and I0 are always positive as shown by the hatched area in the
first quadrant of - plane in fig.1 (b). The power flow in type-A chopper is always from
source to load. This chopper is also called step-down chopper as average output voltage V0 is
always less than the input dc voltage.

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                               Fig. 1(a) Class A Chopper Circuit




                           Fig. 1(b): Voltage and Current Directions

The variations in on and off periods of the switch provides an output voltage with an
adjustable average value.




                                    Fig 1(c): Voltage Waveforms

Average voltage,     =(       /(      +    ))*
                     =(      /T)*

                     =α                     (1)
                        = on-time
                       = off-time
                 T=       +     = chopping period
Thus the voltage can be controlled by varying duty cycle.

                   = f*   *                      (2)
        f = 1/T = chopping frequency

III.   MODELLING OF SEPARATELY EXCITED DC MOTOR

       A separately excited dc motor is very versatile as a variable speed motor. Its speed can be
varied by varying the applied voltage to the armature or field current. The speed control using the
variation of armature voltage can be used for constant torque application in the speed range from
zero to rated speed (base speed). Speeds above base speed are obtained by means of field
weakening, the armature voltage being kept at the rated value. The speed control in this case is at
constant power. In both cases the speed control is smooth and step-less

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                                   2
                               Fig 2(a): Separately Excited DC motor




                      Fig 2(b): Complete layout for DC motor speed control

A. OPERATION OF SEPARATELY EXCITED DC MOTOR

          When a separately excited dc motor is excited by a field current of if and an armature
                                                                                  balance the load
current of ia flows in the circuit, the motor develops a back EMF and a torque to ba
torque at a particular speed. The field current if is independent of the armature current ia.. Each
winding is supplied separately. Any change in the armature current has no effect on the field
current. In general ia is much less than if.

B. FIELD AND ARMATURE EQUATIONS

Instantaneous field current:
                  dif
   f = Rf if + Lf                                      (3)
                  dt

       ,                       resis
Where, Rf and Lf are the field resistor and inductor, respectively.
Instantaneous armature current:
               dia
  a = Raia+La      + Eg                          (4)
               dt
                             armature
    Where, Ra and La are the armatu resistor and inductance respectively.
The motor back emf, which is also known as speed voltage, is expressed as:

E g = Kv ω i f                                         (5)
Kv is the motor voltage constant (in V/A-rad/sec and ω is the motor speed (in rad/sec).
                                 (                                         in

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 C. BASIC TORQUE EQUATION

The torque developed by the motor is:

 d   = Kt if ia                                        (6)

 where, (Kt=Kv) is the torque constant.(in V/A-rad/s)
                                           V/A

                                                   equal
For normal operation, the developed torque must be equal to the load torque plus the friction and
inertia, i.e.

           dω
 d   =J           + Bω +    L                       (7)
           dt
                                    , (N.m/rad/s)
Where, B: viscous friction constant, (
          : load torque (N.m)
                                (kg.m
        J: inertia of the motor (kg.m2)

           STATE
 D. STEADY-STATE TORQUE AND SPEED

 The motor speed can be easily derived:
 ω = ( a - aRa)/Kv f                                (8)

                                                      motor
 If Ra is a small value (which is usual), or when the motor is lightly loaded, i.e. Ia is small,

  ω=       a   /Kv   f                              (9)

 That is if the field current is kept constant, the motor speed depends only on the supply voltage.
 The developed torque is:
  d = Kt f a = Bω + L                            (10)

 The required power is:
  Pd = d ω                                      (11)

 E. TORQUE AND SPEED CONTROL

                                                steady
          An important fact can be deduced for steady-state operation of DC motor. For a fixed field
 current, or flux ( f) the torque demand can be satisfied by varying the armature current a. The
 motor speed can be controlled by controlling a (voltage control) or controlling f (field control).

 F. VARIABLE SPEED OPERATION




                     Fig. 3(a): Torque Vs Speed Characteristic for Different Armature Voltages

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Family of steady state torque speed curves for a range of armature voltage can be drawn as above. The
speed of DC motor can simply be set by applying the correct voltage. The speed variation from no
load to full load (rated) can be quite small. It depends on the armature resistance.

G. BASE SPEED AND FIELD-WEAKENING




  Fig. 3(b): Torque Vs Speed and Power Vs Speed Characteristic of Separately Excited DC Motor

The motor speed can be varied by-
(a) Controlling the armature voltage , known as voltage control;
(b) Controlling the field current , known as field control; and
(c) Torque demand, which corresponds to an armature current , for a fixed field current .

The speed corresponds to the rated armature voltage, rated field current and rated armature current
which is known as the rated (or base) speed. In practice, for a speed less than the base speed, the
armature current and field currents are maintained constant to meet the torque demand, and the
armature voltage     is varied to control the speed. For speed higher than the base speed, the armature
voltage is maintained at the rated value and the field current is varied to control the speed. However,
the power developed by the motor (power = torque * speed) remains constant.
Base speed (       )
-The speed which correspond to the rated       , rated and rated .
Constant torque region (W<          )
-Ia and If are maintained constant to met torque demand.        is varied to control the speed as power
increases with speed.
Constant power region (W>           )
-      is maintained at the rated value and If is reduced to increase speed. However the power
developed by the motor (= torque x speed) remains constant. This phenomenon is known as Field
weakening.




           Fig 3(c): Typical Operating Regions of Separately Excited DC Machines

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IV. DESIGN OF CONTROLLER

Three types of controllers were used and the result was analyzed. Design of Controller
involves the design of three types of controller
   1. Conventional PI Controller
   2. Fuzzy Controller
   3. ANFIS Controller

A. DESIGN OF PI CONTROLLER

1. DESIGN CURRENT CONTROLLER




                          Fig4: Block diagram for design of Current Controller
                                                  d


                     KtKp(1+ is)*( Ra )
     a                    is(1+s a)
         =                                          (12)
 aref            KtKp(1+ is)*(Ra)          K1
                     is(1+s a)            1+ 1s


                              Para
Here, (Current Controller Parameter) can be varied as when required. should be chosen
                                                  the
such that it cancels the largest time constant in the transfer function in order to reduce order
of the system in 7.2.and, the response will be much faster. Assuming
             Ti=Ta
Now, putting the value in equation (12) we have

 a             KtKp/Ras    a
         =                                          (13)
aref           K1KtKp/Ra       a
                s(1+ 1s)


               KtKp
Let Ko =
                RaTa


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So,
                                           /
                       =   =
                                       (       )
                       (           )
                   =                                 (14)
                       ²


Therefore, the characteristic equation of the above equation is given as
       s² + s + K K =0
       s² + +        =0

              s² + 2€ ω + ω ²=0;                   ω=

              €=1/(2        )=
For a second order system value of €=0.707 to have a proper response.
              0.707=

                           K K =1/2

                                       =            (15)


                           K =                      (16)

From Eq.14 we have
            (      )
  =
                       ²                   )


    (         )/
=                                                    (17)
    ² ²



The zero in the above equation may result in an overshoot. Therefore, we will use a time lag
filter to cancel its effect. The current loop time constant is much higher than filter time
constant. For a small delay we can write


(1 +          s)       =                             (18)
                               ²



    =                                                (19)
          ²


Neglecting s² term we have

    =                                                (20)

This equation is used as a response for the speed controller.


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2. DESIGN OF SPEED CONTROLLER




                          Fig5: Block diagram for design of Speed Controller

ω(s)/ ω(s)(ref) = (K /K )(Ra/K           )(1 +     /(1 +      ) ²)/ 1 + (K Ra/K K          )(1 +
   /(1 +      ) ²)(K1/(1 + 1 ))                                                                    (21)

Here, we have the option to Tn such that it cancels the largest time constant of the transfer function
So, Tn=2T2
Hence, equation 21 will be written as:

ω(s)/ω(s)(ref. ) = (K Ra/K K            )(1 + 1 )/ K K           (1 + 1 ) + K RaK1             (22)
Ideally, ω(s) =1/S (S²+αs+β)
The damping constant is zero in above transfer function because of absence of S term, which results in
oscillatory and unstable system. To optimize this we must get transfer function whose gain is close to
unity
Then using Modulus og Hugging method and deducing the above equation we finally get

 ( )( )/     ( )(    ) = 1/( 1 +        1+          1+         1)                                 (23)

3. DESIGN OF FUZZY CONTROLLER

          The fuzzy controller used in this scheme is a Speed Controller. The Conventional Speed PI
Controller is replaced by a Fuzzy Logic Based speed Controller for providing more reliable controller
outputs for the Speed control of The Induction Motor. The main objective of the fuzzy controller is that
the actual speed response of the induction motor must track the reference speed response The design of
a Fuzzy logic system includes the design of a rule base, the design of the member-ship functions
determination of the Linguistic values. Here, the inputs of fuzzy controllers are the error in speed and
the rate of change of this error at any time interval. The output of the fuzzy controller is the Active
Power. Here, five fuzzy sets (NB, N, Z, P, and PB) are adopted for each input and output variables.
The Character NB, N Z, P, PB represents Negative big, Negative, Zero, Positive, Positive Big. The
membership functions of the two input variables and the one output variable has normalized universe
of discourse over the interval [- 1, 1].For the implementation of FLC, firstly, the universe of discourse
of input and output variables of FLC are determined. In practice, each universe is restricted to an
interval that is related to the maximal and minimal possible values of the respective variables. That is
to the operating range of the variable. The universe of discourse of the input and output variables of the
Mamdani type (PI like) FLC can be determined as-

  The universe of the error is defined by the maximal and minimal values of the variables. It {emin,
  emax] is the interval where:
             =
            =



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 Analogously the change in error and the change of the output have operating ranges between
 [            ] and [            ].
    Where,
    `          =
              =
               =
               =

The operating ranges are defined with respect to the external values of the relevant variables. They
can be further adjusted by taking into account the dynamics of the controlled systems and the
sampling intervals.
For simplification and unification of the design of the FLC and its computer implementation,
however it is more convenient to operate with normalizes universe of discourse of the input and
output variables of the FLC. The normalized universes are well defined domains; the fuzzy values
of input and output variables are fuzzy subsets of these domains. In general, the normalized
universes can be identical to the real operating ranges of the variables, but in most applications
they coincide with the closed interval [-1 1].Otherwise ,scaling of both input and output variables
are done in order to bring the values within prescribed limit.
The Rule Table is formulated based on which the Fuzzy Controller is designed.




                              Table:1 Rule base for speed controller

 4.    DESIGN OF ANFIS CONTROLLER

 Steps Involved in the making of the ANFIS Controller
 Step1: Get the Error and Change in Error values from the previous model and save it in workspace
 and finally define these values in a matrix in the M-file of Matlab.
 Step2: Run the matrix file.
 Step3: Open the ANFIS editor.
 Step4: Load data from workspace in the ANFIS editor.
 Step5:Generate FIS using Grid Partition. Here, the number of Member Functions and type of
 Member Functions are taken.
 Step6: Train the data using training FIS. Here the Error tolerance and epochs are also given.
 Step7: The data is trained using Train FIS.
 Step8: Step2 to 7 are performed using Checking Data.
 Step9: The file is saved in both workspace and matlab-file by exporting it.
 Step10: The Simulink model for ANFIS is opened and the controller is named after the name of
 the file saved in Step9.
 The ANFIS Speed Controller is obtained using the above steps.


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V. SIMULATION RESULTS AND DISCUSSIONS

        The graph responses of the Fuzzy and ANFIS controllers has been compared with the.
conventional PI controller. With the implementation of AI techniques (Fuzzy & ANFIS), the
response shows that there is much flexibly with the variation of load found as compared to
conventional model. In all the responses it has been found that the actual speed of the DC
motor is as par with the reference speed of the motor. With Conventional PI speed controller
the actual speed of the motor is tracking the reference speed of the motor up to the rated
speed and even beyond it. But with Fuzzy & ANFIS Controller the actual speed of the motor
is tracking the reference speed of the motor upto the rated speed and when the motor is
overloaded the responses falls and error goes on increasing concluding that the motors fails to
start or the motor stops. Thus the AI technique based controllers provides much better and
precise control of the DC motor.




         FIG 6:-Block Representation of Motor Model with Fuzzy & PI Controller




         Fig 7:-Block Representation of Motor Model with ANFIS & PI Controller



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Appendix
                                                                                                                                         Table:2




I. Performance of DC motor using PI speed Controller

        It is observed from the responses that the actual speed of the DC motor tracks the reference
speed of the motor up to the rated speed of the motor (55rpm). Beyond the rated speed the PI
controller has limitations in controlling the speed of the dc motor.
                                                                                                                                              Reference Speed
                                                                                     60

                                                                                     40
                                                   S p e e d in rp m




                                                                                     20

                                                                                     0

                                                                                 -20
                                                                                          0         0.5       1                    1.5    2         2.5         3       3.5     4       4.5         5
                                                                                                                   Time in Sec
                                                                                                                                                Actual Speed

                                                                                     60
                                                    S p e e d in rp m




                                                                                     40
                                                                                     20
                                                                                     0
                                                                                 -20
                                                                                          0         0.5       1                    1.5    2         2.5         3       3.5     4       4.5         5
                                                                                                                   Time in Sec
                                                                                                                                               Error Speed

                                                                                 60
                                                      S p e e d in rp m




                                                                                 40

                                                                                 20
                                                                                     0

                                                                                 -20
                                                                                         0      0.5           1                   1.5     2         2.5         3       3.5     4       4.5         5
                                                                                                                   Time in Sec


   Fig 8: Speed Responses of a Separately Excited dc Motor with Step Source as Input Using PI
                                                                                                                                         Controller


                                                                                                                                              Reference Speed
                                                                           60
                               S p e e d in rp m




                                                                           40

                                                                           20

                                                                             0
                                                                                 0            0.5         1                      1.5      2          2.5            3     3.5       4         4.5       5
                                                                                                              Time in Sec
                                                                                                                                                Actual Speed
                                                                            60
                          S p e e d i n rp m




                                                                            40

                                                                            20

                                                                             0
                                                                                 0            0.5         1                       1.5     2          2.5            3     3.5       4         4.5       5
                                                                                                                  Time in Sec
                                                                                                                                               Error Speed
                                                                            1
                        S p e e d i n rp m




                                                                          0.5


                                                                            0


                                                                          -0.5
                                                                                 0            0.5         1                      1.5      2         2.5         3        3.5        4         4.5       5
                                                                                                              Time in Sec

Fig 9: Speed Responses of a Separately Excited dc Motor with Ramp Source as Input Using
                                      PI Controller

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II. Performance of DC motor using Fuzzy speed Controller

A.    With motor running up to rated speed
                                                                                                                 Reference Speed

                                                      60




                              S p e e d in r p m
                                                      40

                                                      20

                                                       0
                                                           0       0.5     1                     1.5     2             2.5         3       3.5     4       4.5     5
                                                                               Time in Sec

                                                                                                                  Actual Speed

                                                      60
                            S p e e d in rp m




                                                      40
                                                      20
                                                       0
                                                           0       0.5     1                     1.5     2             2.5         3       3.5     4       4.5     5
                                                                               Time in Sec
                                                                                                                   Error Speed

                                                      60
                            S p e e d in rp m




                                                      40
                                                      20
                                                       0
                                                           0       0.5     1                     1.5     2             2.5         3       3.5     4       4.5     5
                                                                               Time in Sec

     Fig 9: Speed Responses of a Separately Excited dc Motor with Step Source as Input with
                              Rated Load Using Fuzzy Controller


                                                                                                                 Reference Speed
                                                        60
                                 S p e e d in rp m




                                                        40

                                                        20

                                                           0
                                                               0    0.5        1                  1.5        2           2.5           3    3.5        4     4.5       5
                                                                                   Time in Sec
                                                                                                                    Actual Speed
                                                        60
                                 S p e e d in r p m




                                                        40

                                                        20

                                                           0
                                                               0     0.5       1                   1.5       2           2.5           3     3.5       4     4.5       5
                                                                                   Time in Sec
                                                                                                                   Error Speed
                                                        1
                                 S p e e d in r p m




                                                      0.5


                                                        0


                                                      -0.5
                                                             0      0.5        1                  1.5        2          2.5            3    3.5        4    4.5        5
                                                                                   Time in Sec




     Fig10: Speed Responses of a Separately Excited dc Motor with Ramp Source as Input with
                               Rated Load Using Fuzzy Controller




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  B.   With motor running at overloaded condition
                                                                                                                                                      Reference Speed
                                                                         60




                                         S p e e d in rp m
                                                                         40

                                                                         20

                                                                          0
                                                                              0              0.5           1                     1.5         2               2.5              3        3.5        4       4.5     5
                                                                                                               Time in Sec
                                                                                                                                                         Actual Speed
                                                                          0
                                         S p e e d i n rp m

                                                                        -200


                                                                        -400
                                                                               0             0.5           1                     1.5         2               2.5              3        3.5        4       4.5     5
                                                                                                               Time in Sec
                                                                                                                                                         Error Speed
                                                                        500
                                                                        400
                                        S p e e d in rp m




                                                                        300
                                                                        200
                                                                        100
                                                                          0
                                                                              0              0.5           1                     1.5         2               2.5              3        3.5        4       4.5     5
                                                                                                               Time in Sec

  Fig 11: Speed Responses of a Separately Excited dc Motor with Step Source as Input with
                     Over Loading Condition Using Fuzzy Controller

                                                                                                                                                        Reference Speed
                                                                         100
                                                S p e e d in rp m




                                                                          50


                                                                               0
                                                                                   0          0.5              1                  1.5            2               2.5              3     3.5           4    4.5        5
                                                                                                                   Time in Sec

                                                                                                                                                          Actual Speed
                                                                               0
                                               S p e e d in rp m




                                                                         -200


                                                                         -400
                                                                                   0           0.5             1                   1.5           2               2.5              3         3.5       4     4.5       5
                                                                                                                   Time in Sec

                                                                                                                                                          Error Speed
                                         S p e e d in rp m




                                                                          300

                                                                          200
                                                                          100
                                                                               0
                                                                                   0           0.5             1                   1.5           2               2.5              3         3.5       4     4.5       5
                                                                                                                   Time in Sec




 Fig 12: Speed Responses of a Separately Excited dc Motor with Ramp Source as Input with
                                 Over Loading Condition

III. Performance of DC motor using ANFIS based speed Controller
 A. With motor running up to rated speed
                                                                                                                                             Reference Speed
                                                       60
                    S p e e d in rp m




                                                       40

                                                       20

                                                              0
                                                                    0                  0.5           1                    1.5            2                 2.5            3           3.5         4       4.5     5
                                                                                                         Time in Sec
                                                                                                                                                     Actual Speed

                                                       60
                    S p e e d in rp m




                                                       40

                                                       20

                                                              0
                                                                    0                  0.5           1                    1.5            2                 2.5            3           3.5         4       4.5     5
                                                                                                         Time in Sec
                                                                                                                                                     Error Speed

                                                       60
                    S p e e d in rp m




                                                       40

                                                       20

                                                              0
                                                                    0                  0.5           1                    1.5            2                 2.5            3           3.5         4       4.5     5
                                                                                                         Time in Sec


 Fig 13: Speed Responses of a Separately Excited dc Motor with Step Source as Input with
                          Rated Load Using ANFIS Controller

                                                                                                                                                      242
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 2, March – April (2013), © IAEME
                                                                                                                                                          Reference Speed
                                                                                    60




                                 S p e e d in rp m
                                                                                    40

                                                                                    20

                                                                                            0
                                                                                                 0        0.5     1                      1.5          2            2.5             3       3.5              4       4.5       5
                                                                                                                      Time in Sec
                                                                                                                                                              Actual Speed
                                                                                    60

                                                                                    40




                       S p e e d in rp m
                                                                                    20

                                                                                            0

                                                                                                 0        0.5     1                      1.5          2            2.5             3       3.5              4       4.5       5
                                                                                                                      Time in Sec
                                                                                                                                                               Error Speed
                                                                                         60

                                                                                         40
                          S p e e d in r p m




                                                                                         20

                                                                                            0
                                                                                                 0        0.5     1                      1.5          2            2.5             3        3.5             4       4.5           5
                                                                                                                          Time in Sec




Fig 14: Speed Responses of a Separately Excited dc Motor with Ramp Source as Input with
                         Rated Load Using ANFIS Controller

B. With motor running at overloaded condition

                                                                                                                                                          Reference Speed
                                                                                                 60
                                                S p e e d in r p m




                                                                                                 40

                                                                                                 20

                                                                                                 0
                                                                                                      0    0.5        1                   1.5         2             2.5            3        3.5         4           4.5       5
                                                                                                                           Time in Sec

                                                                                                                                                              Actual Speed
                                                                                                 0
                                               S p e e d in rp m




                                                                                            -20
                                                                                            -40
                                                                                            -60
                                                                                                      0    0.5        1                   1.5         2             2.5            3        3.5         4           4.5       5
                                                                                                                           Time in Sec


                                                                                                                                                               Error Speed
                                               S p e e d in rp m




                                                                                            100


                                                                                                 50


                                                                                                 0
                                                                                                      0    0.5        1                   1.5         2             2.5            3        3.5         4           4.5       5
                                                                                                                           Time in Sec


 Fig 15: Speed Responses of a Separately Excited dc Motor with Step Source as Input with
                   Over Loading Condition Using ANFIS Controller


                                                                                                                                                          Reference Speed
                                                                                            60
                                                                             S p e e d in rp m




                                                                                            40

                                                                                            20

                                                                                                 0
                                                                                                     0    0.5     1                      1.5          2            2.5             3       3.5          4       4.5       5
                                                                                                                          Time in Sec
                                                                                                                                                              Actual Speed
                                                                                                 0
                                                                     S p e e d in rp m




                                                                                  -100


                                                                                  -200
                                                                                                     0    0.5     1                      1.5          2            2.5             3       3.5          4       4.5       5
                                                                                                                          Time in Sec
                                                                                                                                                              Error Speed
                                                                                     200
                                                                        S p e e d in rp m




                                                                                     100


                                                                                                 0
                                                                                                     0      0.5             1                   1.5       2                  2.5       3          3.5           4         4.5
                                                                                                                          Time in Sec

Fig 16: Speed Responses of a Separately Excited dc Motor with Ramp Source as Input with
                  Over Loading Condition Using ANFIS Controller .


                                                                                                                                                          243
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 2, March – April (2013), © IAEME

VI. CONCLUSION

        In this paper the speed of a dc motor has been done using three different types of
Controllers viz Speed PI controller, Fuzzy logic based controller and ANFIS based controller.
The responses of the motor with three different types of controllers are simulated and studied
and compared with step and ramp responses. With varying load responses it is observed that
the AI technique based controllers’ gives a flexible and precise control of speed both on
normal loaded and overloaded condition as compared to the conventional PI controller.

REFERENCES

[1].Waleed I. Hameed1 and Khearia A. Mohamad2” Speed control of separately excited dc
motor using fuzzy neural model reference controller” International Journal of Instrumentation
and Control Systems (IJICS) Vol.2, No.4, October 2012 PP 27-39.
[2] Dr.P.S Bimbhra “Power Electronics”,Khanna Publishers.
[3]Ronald R Yager, Dimitar P Filev, “Essentials of Fuzzy Modeling and Control “Wiley
Interscience Publications.
[4]Jun Yan, Michael Ryan, James Power “Using Fuzzy
Logic towards Intelligent systems”
[5]Singari.v.s.r Pavankumar, Sande.krishnaveni, Y.B.Venugopal, Y.S.Kishore Babu, “A
Neuro- Fuzzy Based Speed Control of Separately Excited DC Motor”, IEEE Transactions on
Computational Intelligence and Communication Networks, pp. 93-98, 2010.
[6] Basma A. Omar, Amira Y. Haikal, Fayz F. Areed, “An Adaptive Neuro-Fuzzy Speed
Controller for a Separately excited DC Motor”, International Journal of Computer
Applications, pp. 29-37, Vol. 39 No.9, February 2012.
[7] Vandana Jha, Dr. Pankaj Rai and Dibya Bharti, “Modelling and Analysis of Dc-Dc
Converter Using Simulink for Dc Motor Control”, International Journal of Electrical
Engineering & Technology (IJEET), Volume 3, Issue 2, 2012, pp. 58 - 68, ISSN Print : 0976-
6545, ISSN Online: 0976-6553.
[8] M.Gowrisankar and Dr. A. Nirmalkumar, “Implementation & Simulation of Fuzzy Logic
Controllers for the Speed Control of Induction Motor and Performance Evaluation of Certain
Membership Functions”, International Journal of Electrical Engineering & Technology
(IJEET), Volume 2, Issue 1, 2011, pp. 25 - 35, ISSN Print : 0976-6545, ISSN Online: 0976-
6553.

BIBLIOGRAPHY


              Debirupa Hore was born in Guwahati Assam India on April 19th 1983.She
              received her B.E Degree in Electrical Engineering from Assam Engineering
              College Guwahati in 2006 and M.Tech in Energy and Power Systems in 2010
              from NIT Silchar. She worked in GIMT Guwahati for 5 years as Assistant
              Professor. Currently she is working as an Assistant Professor in Electrical
              Engineering Department in KJ Educational Institutes, KJCOEMR, Pune
              (Maharashtra).Her research areas of interest includes Power Systems, AI
Techniques, Power Electronics and Drives etc.



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