Automatic Process Modeling From Relay Feedback

Abstract Relay feedback is a proven technique for auto-tuning of PID controllers. In this paper, the same method is used to automatically generate an approximate process model under closed-loop control. The process ultimate gain and ultimate period are obtained from a relay feedback experiment, and subsequently any step change in the set point will yield an accurate estimate for either process static gain or dead time. A more accurate process model can then be recomputed and used to commission an appropriate model-based advanced controller. The effectiveness and robustness of the method are substantiated by extensive simulation study.