Reply To: Using PIDE for Fermenter Temperature Control

#2869
Fred Graham
Fred Graham
Keymaster
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Hi Jim and welcome to the forums.

It would be difficult to say without seeing the response curves of your process. My gut is telling me that the gains values you have may be part of the issue. A proportional of 200 seems excessive, can I ask how did you arrive at these gain values? Trending the responses over time would yield more concrete evidence to analyze.

Not sure if you’re aware (I assume you are and it’s why you’re here) but I am putting together a YouTube series on this very topic – ControlLogix PID Essentials.

I would be curious to see in a trend what exactly is going on, perhaps the error on startup is insurmountable for the controller to overcome due to the excessive proportional action, and as you say, once the operator manually brings the temperature to within setpoint “bumpless transfer” the controller can maintain.

Again with these gains that you have, I would like to see how it is maintaining. Are there oscillations? Is there a significant phase shift between CV and PV? Are you seeing any noise or amplification of noise? What about deadtime and lagtime in your process? A trend would yield meaningful information about all these things. Have you tried an Autotune?

Fred