Tuning PID Controller in InfoWorks ICM

Hi,

I have recently discovered the use of PID controllers and have been using them to control sluice gates based on the water level in a downstream interceptor in a sanitary sewer system. I have a bit of trouble tuning the P,I, and D variables though. Although I can typically get my curve to smooth out after much effort and trial/error, I was wondering if anyone had any tips on tuning the variables in an efficient way. I can usually get the curve to oscillate centered on my target interceptor level with the P variable, but from there it goes out of control until I get the D variable tuned back in. If I change some parameters in my model or change up the rainfall event I find the need to re-tune the D variable, which is not very time friendly the way I am doing it now. I have attached an image of one of my tuned controllers as well as one that occurs after I have changed to a different rainfall event and have not tuned.

Any help is greatly appreciated!

Thanks,

Nick

Hello Nick,
Can you show the constants you are using for the PID controller?
Regards,
Robert Dickinson

Absolutely! For the tuned image in my original post I am using a time step measurement of 240s and my constants for P, I, and D are -0.5, 0.0, and 0.5, respectively.

For the un tuned image in my original post the time step measurement is 180s and my constants for P, I, and D are the same as the tuned image - -0.5, 0.0, 0.5, respectively.

I did get my curves to smooth out. Though, I did not changed my time step measurement or constants. All I did this time was match the crown of the pipe flowing into the interceptor with the same elevation as the depth set for the sensor. I am still interested in your input though as I am sure that I will need to re-tune once again if I change something.

Thanks,

Nick

I do need to make a correction on my first post from today. My D constant is 5 not 0.5...