On the Analysis and Synthesis of Control Systems with Input Saturation

A saturating actuator can cause stability and performance issues such as windup for a feedback control system designed on linear methods. Anti-windup techniques can be used to preserve the linear behavior in the presence of saturation. Specifically, a local feedback around the saturating actuator via a compensator H can be used. The loop transmission Ln(s) around the actuator has been shown to be the key factor for saturation compensation. An independent Ln(s) can be created by introducing H . In this paper, detailed analysis on the nonlinear responses in terms of Ln(s) and the corresponding linear responses is presented. Synthesis of H is achieved through the solution of an equivalent input disturbance rejection problem. This new synthesis scheme can accommodate the plant uncertainty and the extension to multi-input multi-output (MIMO) plants. Also, it facilitates the application of robust control tools. Examples solved using H∞ and μ-synthesis demonstrate the effectiveness of the proposed approach.