Calculate gain and phase margin on simulink

Hi there... I wanted to know how to find out the gain and phase margin of the open loop system that is in series with a PID controller. I want to access the stability margins continuously and tune my PID accordingly. These values are given as input to fuzzy controller and PID values are set in reference with the user defined stability margins. How can I do that? I would be really happy if someone can help me out...I have also attached the simulink block(just to show) Thanks in advance..

Answer 1

[Yogananda Jeppu]

This is interesting. Can you define a time response equivalent instead (second order response) and tweak your controller to get the desired time response. Or compute the linmod with the plant and PID every time and tweak PID. Another approach is to input a sine sweep, do an fft and get the TF. Get the Gm and Pm and tweak. It is not an exact solution.