Reply To: Using PIDE for Fermenter Temperature Control

AdminFred Graham
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Hi Jim,

Yes, I imagine that would make the distillers “cranky”! As the other Fred said, it may be beneficial after you’ve setup some trends to effectively quantify some of your process variables to setup an offline model that makes use of the DEDT and LDLG instructions to simulate the process.

Just a quick question, you are describing a direct-acting process. Have you confirmed in the PIDE that you are in fact set for direct action, E = PV – SP.

When the opportunity arises, I would suggest an Autotune on the controller. This needs to be done in open-loop control mode. In the test you will be able to specify a CV Step Change limit as well as a PV Change Limit. The autotune procedure will then perform a “bump-test” on CV that will measure the dynamic response of your process as it “bleeds” back to zero. The nice thing about this is it will take into account any deadtime or lead-lag time in your process as well.

In the meantime, setup your trend, study your process’s dynamics, and setup an offline model if possible.