Performance-Based Adaptive Control Preventing Input Saturation: A Monitoring Modulation Approach

Eliminating the effect of input saturation is greatly significant in maintaining system performance. This article proposes a performance-based adaptive anti-saturation control scheme for a class of uncertain nonlinear systems with input saturation limit. Unlike the compensation-based anti-saturation schemes that do not take saturation occurrence into account, the proposed method adopts a monitoring modulation approach to proactively prevent the occurrence of input saturation. Specifically, an adaptive controller is first designed based on prescribed performances and shifting functions. Then, a monitoring module is employed to supervise the behavior of the control signal, and a modulation module is intended to implement the controller reconfiguration by updating the shifting functions. It is shown that by using the proposed scheme, the control signal never violates the saturation limit, the Zeno phenomenon is avoided, and the tracking error satisfies a modified prescribed performance.