what is the different of PI and PID controller??

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Is there any general equations for P controller and I controller?? why do some systems need a PID controller, some with PI controller will do??

-- Pui Sim Leaw (peixin79@hotmail.com), March 26, 2003


Hi, P controller: controller output=Kp*e I controller: controller output=Ki*e/s The purpose of P controller is to decrease the steady-state error, but it has the side effect, that is, larger overshoot and could give rise to the oscillation. The purpose of I controller is to eliminate the steady-state error, since it increases one pole in origin. The D controller is used to increase the stability, but when you want to use that, be careful since it will increase the noise in high frequency.

-- Jessy (hawan01@student.sdu.dk), April 08, 2003.

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