Applet shows the controller outputs of a type 0 system with PID control and a unit step input.

The response is in Green and the error in Blue. The P controller output (Orange) is K times the error. The D controller output (Cyan) depends on the derivative of the error. It goes to zero at the maxima and minima of the error and has turning points where the derivative of the error is a maximum or minimum. The derivative of the I controller output (Red) depends on the error. The gradient is zero(turning point) at the zeros of the error. The output from both the P and D controllers go to zero at large times while that of the I controller becomes equal to the output.

Gif image below show how the applet should appear.

COPYRIGHT © 2006 Cuthbert Nyack.