Anti-windup via the creation of an independent loop transmission around the saturating actuator

Stability and performance degradation in feedback control systems under saturation can be overcome by anti-windup techniques. The loop transmission around the actuator is the key factor for saturation compensation. In this paper, the importance of this loop transmission is emphasized. First, a representation of the nonlinear system in terms of this loop transmission is presented, incorporating another decomposition proposed by Weston and Postlethwaite (2000), which facilitates the analysis of the nonlinear system stability and performance. Second, a synthesis method based on this representation, considering both robust stability and performance, is proposed by solving a standard H_infin problem. The merits of this method are the simplicity and generality. It allows for plant uncertainties and applies to multi-variable systems. It generalizes many existing anti-windup schemes in the literature, notably, coprime factorization based approaches