Dc Motor Speed Controller Using Pic Controller__ce-28_a_

HEM ELECTRONIQUES, MIDC, MIRAJ

DC MOTOR SPEED CONTROLLER USING PID MODE (CE-28 A)/1

DC MOTOR SPEED CONTROLLER USING PID MODE (CE-28 A)

This DC motor speed control system is designed to demonstrate the application of PID control mode for DC motor. The unit is self-contained. 24 v, 2 Amp DC motor mounted on a fixed base & provided loading arrangement. The speed of the motor made variable with the help of Pot P1. The Armature voltage is derived from a regulated DC power supply 35 v, 3 Amp capacity. The unit is provided with analog Ammeter (0-2A). The front panel of the system having various controls for the study of the system with open loop and close loop mode. In close loop we can study the system performance with proportional mode, P+I mode & P+I+D mode. The potentiometers for proportional gain, integral time constant & derivative time constant are provided on the system. The reference speed can be varied by using Pot P1. The same reference Pot is also associated with a soft start arrangement to avoid sudden start of the system. In the open loop mode, we can observe that at set speed if we apply a load the speed of the system is decreases. But in closed loop mode, even if load increases the speed of the system is constant. thus the entire system enables to observe the effect of load variations on the system performances. In the open loop, the system operates in the range 200 – 1500 rpm & in closed loop the system operates 200 – 900 rpm with max. Current of 2 Amps. Please note that Soft start is provided in both open loop and closed loop modes. So for open loop :- Motor will start running only when ref is <=10 For Closed loop :- Motor will start running only when SP >=50 and <=100 rpm. A) Operating Instructions for open loop operation:

1) Before you switch ON the unit please study all the controls on the panel & try to understand their functions also.

2) Keep Sw1 in upward position i.e. in open loop position. 3) Keep Sw2 in upward position i.e. in normal position. 4) Keep Sw3 in upward position i.e. start position.



5) Start the motor with the help of pot P1 at ref 10 (i.e. ADC value) indicated by LCD

6) Set the speed 1500-rpm max. At 1500 rpm motor takes 200 mA current i.e. no load current.

6) Apply a load (in the range 200 – 800 mA max) & enter the reading in tabular form.

Open Loop mode Set Speed =1500 rpm READINGS FORMAT :-

Sr no Current in Amp

Actual Speed (rpm)

1 0.2 (no load) 1500 2 0.3 970 3 0.4 750 4 0.5 600 5 1 420 6 1.5 325

(SAMPLE READINGS only for trend ) Conclusion: in the open loop mode the system is very sensitive to disturbances i.e. change in load B) Close loop with proportional action:

1) Keep Sw1 in lower (Close loop) position. 2) Keep Sw2 in lower (mode check) position & set the proportional gain Kp at

30. Then keep the Sw2 at higher (normal) position. 3) Keep Sw3 in upward position i.e. start position. 4) Then start the motor with the help of pot P1 from 50 -100 rpm above and

set point slowly from 200 to 800 rpm indicated by LCD. 5) Apply a load (in the range 200 – 2 amp max) & enter the reading in tabular form.

READING1 Proportional mode Kp = 30 Set Speed = 850 rpm (These are only reference readings) Sr no Current in

Amp Actual Speed (rpm)

Set speed

1

110 250 2 220 350



3 No load (without loading the motor)

280 450 4 370 550 5 460 650 6 550 750 7 650 850 8 770 900 Conclusion1:- In proportional mode there will always some error (set speed- actual speed) As you go on increasing value of ‘KP’ error will be reduced. READING 2:- For Condition1 :- Set speed = 700 , Actual speed = 550, Kp = 30 ,Ki=0,kd=0 No load current = 300 ma For Condition2 :- Now you load the motor slightly i.e. Load current = 1 amp Set speed = 700 , Actual speed = 350, Kp = 30 ,Ki=0,kd=0 Because of increase in the load on the motor actual speed is reduced Actual speed @1 = 550 rpm at 0.3 amp load Actual speed @2 = 350 rpm at 1 amp load Difference between actual speed1 and speed2 is called as offset error. Conclusion2:- There will be always some offset error for change in load on the motor in proportional mode C) Close loop with proportional +Integral (P+I) action:


30 & Ki = 1 by pot P2 & P3 respectively. Then keep the Sw2 at higher (normal) position.

3) Keep Sw3 in upward position i.e. start position. 4) Then start the motor with the help of pot P1 from 150 -200 rpm above and

set the speed slowly at 850 rpm indicated by LCD.



5) Apply a load (in the range 200 – 800 mA max) & enter the reading in tabular form.

(sample readings for only for trend) Proportional +Integral mode Kp = 30 & Ki = 1 Set Speed = 850 rpm Sr no Current in


1 0.1 (no load) 850 2 0.2 850 3 0.5 850 4 0.8 850 5 1 850 6 1.2 850 7 1.5 850 8 2 850 Conclusion: Thus we conclude that the P+I control removes OFFSET error completely but may give poor transient performance (may be osciallations) for some settings. D) Close loop with proportional +Integral + Derivative (P+I+D) action:


30, Ki = 1 & Kd = 4 by pot P2, P3 & P4 respectively. Then keep the Sw2 at higher (normal) position.

3) Keep Sw3 in upward position i.e. start position. 4) Then start the motor with the help of pot P1 from 150 -200 rpm above and

set the speed at 850 rpm indicated by LCD. 5) Apply a load (in the range 200 – 2 Amp mA max) & enter the reading in tabular form.

Proportional +Integral mode Kp = 30 & Ki = 1 & Kd = 4 Set Speed = 850 rpm Sr no Current in


1 0.1 (no load) 850 2 0.2 850



kp= 105 ki= 1 kd = 4 PID CL LOOP

3 0.5 850 4 0.8 850 5 1 850 6 1.2 850 7 1.5 850 8 2 850 Conclusion: Thus PID control mode offers good transient response and no OFFSET error.

Some Additional Instructions:

1) Switch Sw1 is used for open loop & close loop operation. 2) Switch Sw2 is used for normal & mode check operation. 3) Switch Sw2 in upward position (normal) LCD indicates.

REF COUNT = for open loop operation when Sw1 in upward AP= RUN /STOP position.

4) Switch Sw2 in downward position (mode check) LCD indicates for close loop operation when Sw1 in downward position.

5) Switch Sw3 is used for Start & Stop the operation. PRECAUTIONS:

1) Please note that the max speed for open loop is 200 – 1500 & closed loop is 200 – 900 rpm at max load current 2 Amps

2) Do not load & unload the motor suddenly. 3) Operate the pots P1, P2, P3 & P4 carefully. 4) Do not overload the motor above 2 Amp , motor may stop running

completely. In this scenario goto Stop and restart the operation from zero.

5) Always operate in range of 2 Amp current . 6) Do not change over from Open loop to close loop and vice versa

when motor is in running mode. 7) Always operate the motor with some small load (around 0.5 Amp) for

better performance.

8) If you load or / unload the motor suddenly or change from open to close loop when motor is in running mode then controller may go



into oscillatory mode because of very high error signal applied suddenly. ---------------------------------------------------------------------------------------------------







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Dc Motor Speed Controller Using Pic Controller__ce-28_a_