EXPERMENT 8 SPEED CONTROL OF A PERMANENT MAGNET DC MOTOR : PID CONTROLOBJECT: To design PID controller for velocity control of a permanent magnet D.C. motor.3.1 Open Loop Performance For gain 1Voltage : Voltage does not change .Current : 0.6 ATorque : We can say there is nearly no torque.We can stop it easily. For gain 3Voltage : Voltage does not change .Current : 0.6 ATorque : We can say there is nearly no torque.We can stop it easily.As you see from the experimental results amplifier gain does not effect the motor characteristics.Voltage and the current is same for variable gain values.3.2 Closed Loop Performance 3.2.1 Speed control of a permanent Magnet DC motor with the proportional P controlMotor speed=15 rev/sec For gain 1Motor stall voltage= 7VMotor stall current=1.05 A Torque : In 3.1 Open Loop Performance there is nearly no torque.But here more torquen the system.

For gain 3Motor stall voltage = 9V Motor stall current = 1.36 A Torque : Here the torque is greater than the gain 1 s torque. For gain 4Motor stall voltage = 9.2 V Motor stall current = 0.34 A Torque : Torque is the greatest for gain = 4 among all of the gain values.Conclusion As you see from the experimental results increasing the gain will increase the torque.In DC motors, while gain is increasing a noisy sound in the motor is increasing this is because of back emf and frequency fluctuations in the motor.3.2.2. Speed control of a permanenet magnet DC motor with the proportional plus integral,PI controlMotor speed=15 rev/sec, Motor voltage=9VFor gain = 1For =1s We applied torque and speed decreased to 10 rev/sec and we just released it and measured it as 27 rev/sec.Then it slowly decreased to 15 rev/sec.For =10s We applied torque and speed decreased to 1 rev/sec and we just released it and measured it as 28 rev/sec.Then it slowly decreased to 15 rev/sec.But here the time required to come back to 15 rev/sec takes more time than =1s . For =100ms Here there is very rapip change , it comes back to 15rev/sec very fast.Here in loading condition voltage is same while we are applying load.

No Load ConditionIf we look at the responses of the gain 1 and gain 3 ;We can say that higher gain means shorter response times. The responses with respect to the time constants of the gain 1 will be slower than the gain 3 s responses.And also for gain 3 increasing time constant will be slower.3.2.3 PID (Proportial+Integral+Derivative) ControlIn this part, we just observe the system response and systems noise.Conclusion For This Part; The rate of change of speed of speed and the overshoot should be reduced by the introduction of derivative and varying the time constant of the differentiator and low pass filter reduce the noise in motor. It is because low pass filter does not let the pass for high frequencies for that reason noise is reuced.