Re: How Tune PID in octave using Frequency Response data

[Nicklas SB Karlsson]

> Hello,
> 
> I have the frequency response data of a plant. What steps would I take to
> tune a PID in octave?
> 
> Thanks,
> Stephen

For tuning there are several options, Ziegler-Nichols method is one but it 
might be better to do some mathematical analysis on how your gains effect the 
bode plot of the closed system. Noise may also be a problem if you do not want 
this to enter control loop, integral gain is least sensistivity for noise, 
proportional gain in between and derivative gain most sensitive to noise. 
Usually there is a choice between noise entering control loop, it may also make 
audible noise and speed. Charging batteries is a slow process while unstable 
processes like inverted pendulum must be fast enough to stabilized pendulum.

The tuned system may be checked with nyquist(...) by closing the control loop 
with your PID regulator. You probably want to check phase and amplitude 
margins, maybe also sensitivity.

System may be closed by transfer function if you have this but as I understand 
it you have frequency response. You may calculate frequency response of your 
PID regulator with bode(...) function and use numeric calculations on 
amplitudes and phases for your PID regulator and frequency response of plant. 
If do not know how to make these calculations I might try to get an hour or so 
thinkging about it and help you.


Nicklas SB Karlsson