How to design a PID controller with no additional i) gain margin, ii) phase margin

bode plotcontrol system

Given a system G(s), how do I design a controller C(s) such that no additional phase or gain margin is incurred? I would like to do this analytically

Surely I could go through the step of drawing a Nyquist plot of the CP(s) system and then tune the parameters one by one, but are there easier methods for which this can be done without going through the Nyquist or Bode plot?

Best Answer

How to design a PID controller with no additional i) gain margin, ii) phase margin?

A PID introduces gain (the "P" in PID means "proportional") so if you don't want extra gain maybe you'd be happy with gains between 0 and 1?

The I is integration and that creates a whole different phase angle that may or may not make the phase margin worse. So maybe "I" should be left alone leaving "D", the differential signal. "D" also creates a phase change so in short you cannot really have a PID controller.

You can have a "P" controller that has a gain between 0 and 1.