Fuzzy Adaptive Output Feedback Fault-Tolerant Tracking Control of a Class of Uncertain Nonlinear Systems With Nonaffine Nonlinear Faults

This paper studies the fuzzy adaptive output feedback fault-tolerant control (FTC) problem for a class of single-input and single-output uncertain nonlinear systems with time-varying nonaffine nonlinear faults in strict-feedback form. In the design procedure, filtered signals are adopted to circumvent algebraic loop problems on implementing the usual controllers. By using fuzzy logic systems to approximate the unknown nonlinearity effects and changes in model dynamics due to faults, a fuzzy state observer is first presented to estimate the unmeasured states. Based on the online estimating information from the adaptive mechanism, an observer-based dynamic output feedback fault-tolerant controller is designed via the backstepping technique. It is shown that the stability and tracking performances of the closed-loop system can be achieved even in the presence of unknown nonlinear faults. In comparison with the existing approaches, the FTC scheme can handle the nonaffine nonlinear faults effectively. Finally, a simulation example is included to validate the advantages of the proposed approaches.