Disturbance Rejection?


#1

Greetings from Michigan, USA!

I’m using a RMC150 to cycle a valve on a part-under-test. We’ve been doing this for some time and it works good, however I want to know what I can do for better disturbance rejection. I can tune the loop manually and get the pressure trace right where I want it, cycling the valve at ~2 Hz. However, over time (usually a couple hours of cycling at ~2 Hz) as the part-under-test begins to “break in”, the trace starts drifting and usually is over-shooting on the ramp up. So then of course I have to de-tune, which typically I just bring the integral gain down some until the trace is back where I want it. After some time when the part-under-test is fully broken in and I’ve tuned the control loop to the fully broken in part, its fine and it can run like clock work for days at 2 Hz cycle rate (ramp up, ramp down, etc). What can I do to mitigate or eliminate having to adjust the tuning periodically until the part-under-test is fully broken in?? Is it a simple matter of better PID tuning? Will that take care of the “problem” or is adjusting the tuning parameters inevitable for some scenarios such as mine? Thank you.


#2

Maybe you could use the technique in this post: