Robust fuzzy adaptive fault-tolerant control for a class of nonlinear systems with mismatched uncertainties and actuator faults

This paper studies the adaptive fuzzy fault-tolerant control (FTC) problem for a class of nonlinear systems with mismatched uncertainties and actuator faults. Two control schemes are designed to compensate for the actuator faults including outage, stuck and loss of effectiveness. The fuzzy logic systems are applied to approximate the bound of unknown nonlinear functions without knowing the information about the upper bound of mismatched uncertainties. By using projection modification algorithm and the improved adaptation law with σ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sigma $$\end{document}-modification, the adaptive fuzzy FTC scheme is designed. It is shown that the system states can converge asymptotically to zero even in the presence of actuator faults. However, the chattering phenomenon may occur. To overcome the undesirable chattering phenomenon, a continuous-state feedback control strategy is adopted for the control design so that the required assumption can be removed. It is shown that all the signals in the resulting closed-loop system are semi-globally uniformly ultimately bounded. Finally, simulation results are presented to demonstrate the effectiveness of the proposed control methods.