PID controllers are a way of controlling a changing system. The user specifies a set-point and the system will try to reach the set point. Changing the P, I, or D effect the response curve of the system, they can be thought of as tuning parameters. A motor control system is used to demonstrate effects of changing P, I, or D. There is a potentiometer providing feedback to the controller(PID equation) as to the position of the motor. The user inputs a specified number of revolutions of the motor shaft and the controller will send a signal to the motor to turn the required amount. As the motor reaches the number of turns, approaches the specified value, it will decrease its speed until it stops in the right position. Changing the values of P, I, or D effect the system differently, this can be seen in the following graphs. In our experiment, we changed values of P, I, and D (Kp, Ki, and Kd) and performed one test with nominal values. All tests began with the potentiometer at 1000 and were run until it reached 2000 (i.e. 5 turns).
Test 1: Kp=1.0 Kd=.01 Ki=.01
Test 2: Kp=2.0 Kd=.01 Ki=.01
Test 3: Kp=1.0 Kd=.01 Ki=.50
Test 4: Kp=1.0 Kd=.50 Ki=.01