Estimator-based active fault tolerant control for switched nonlinear systems with performance constraints

This paper is concerned with the estimator-based active fault tolerant control (AFTC) problem for switched nonlinear systems with performance constraints. In this study, the estimated faults are allowed to be of multiple types, e.g., process fault, actuator bias fault and actuator loss of effectiveness (LoE). A new adaptive estimator is designed to estimate the system state and unknown fault. Furthermore, according to the obtained fault estimation signal, the fault detection mechanism is constructed. To cope with the compensation error induced from the estimator, the adaptive error compensation mechanism is established, and the compensation-based fault tolerant control protocols are designed according to a simplified backstepping design strategy. The prominent advantages of the design strategy are that the assumption requiring a prior knowledge of higher-order derivatives of reference signal is eliminated, and “explosion of complexity” is prevented without adopting filtering techniques. Subsequently, a new performance constraint method is integrated into the control scheme to achieve asymptotic tracking under no strict initial conditions, while maintaining good transient tracking performance, i.e., the fast fixed-time convergence without obvious overshoot. It is proved that all the signals of the closed-loop system are semi-global uniform ultimate bounded (SUUB) under arbitrary switching. Finally, simulation results verify the feasibility of the proposed control scheme.