Automatic tuning of gain-scheduled control for asymmetrical processes

Abstract

This paper presents an automatic tuning procedure for gain-scheduled control of asymmetrical processes. A modified relay feedback is employed to obtain a frequency response estimation for the dual dynamics of the asymmetrical process, where a novel gain-matching and frequency-matching method is developed to correct an asymmetry phenomenon associated with the oscillations induced from a direct application of basic relay feedback. Based on the frequency response estimation and a closed-loop identification of the process gain, two first-order transfer function models are fitted to the process. Subsequently, a gain-scheduled PI control can be tuned according to the process models, so that the compensated system satisfies user-specified gain and phase margin requirements. Simulation examples are provided for illustration. © 1998 Published by Elsevier Science Ltd. All rights reserved.