PI Design Method Based on Sensitivity

Abstract

A new robust proportional−integral (PI) autotuning method based on the maximum sensitivity is proposed in this paper which can be applied to unknown, stable, and minimum-phase plants. The presented algorithm chooses the maximum sensitivity as the design parameter. The PI controller parameters are obtained by making the Nyquist curve of the loop transfer function tangentially touch the sensitivity circle at a specified frequency. The process frequency response at the frequency where the maximum sensitivity is achieved is identified by relay feedback test, and the derivatives of amplitude and phase of the plant with respect to frequency can be estimated by process frequency response by introducing Bode's integrals. No intermediate model is needed. Therefore, the presented method does not suffer from the modeling error. Simulation examples for different kinds of processes illustrate the simplicity and the effectiveness of the proposed method.