Adaptive Control of Nonlinear System Subjected to Input Constraints with Composite Adaptive Law

Abstract

An adaptive control scheme with composite adaptation, which combines the prediction-error estimation for uncertainty, is proposed for uncertain nonlinear systems under input actuator constraints, including the amplitude and rate saturation. Together with the conventional tracking-error estimation, the prediction-error estimation is used to enhance the estimation of uncertainties in the system. It brings additional stabilizing properties for parameter estimation error, which is absent in conventional adaptive control. An auxiliary dynamics driven by the actuator saturation error is constructed to form an augmented tracking error, which is used in the design to guarantee the stability of the closed-loop system with actuator saturations. Model uncertainties, such as unknown parameters and disturbance, including the unknown control input gain, are considered in the system. Stability analysis and simulation examples on wing rock are provided in this study.