Closed Loop Tuning of Cascade Controllers Based on Setpoint Experiment

Abstract

This study presents online PI/PID controller tuning rules for cascade control configuration. The necessary process data are determined with the help of a simple setpoint experiment in a single closed-loop mode with the proportional controller only. The obtained process data is recorded in terms of the overshoot, controller gain, peak time, and relative output change. The data is then utilized to establish a correlation with PI/PID settings through simulations. Further, the proposed PI/PID controller tuning rule for a single loop has been extended to the cascade control configuration. The inner loop controller is tuned first, and then the primary loop is tuned by considering a well-tuned inner loop as a part of the primary plant. Finally, simulation examples demonstrate that the proposed method delivers significant disturbance rejection and better setpoint response when compared to the recently reported methods from the literature. The proposed method is also able to deliver stable closed-loop performances when subjected to large parametric uncertainties and measurement noise.

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