Prescribed performance fuzzy adaptive fault-tolerant control of non-linear systems with actuator faults

This study investigates the adaptive fuzzy fault-tolerant control (FTC) problem for a class of uncertain non-linear strict-feedback systems with unmeasured states. The considered non-linear systems contain unknown continuous functions and do not satisfy the matching condition. The actuator failures under study are types of both abrupt faults and lock-in-place and loss of effectiveness. The fuzzy logic systems are employed to approximate the unknown continuous functions, and a fuzzy state observer is developed and the unmeasured states are obtained. Under the framework of the backstepping design technique and incorporated by the dynamic surface control approach and predefined performance bounds, an adaptive fuzzy FTC method has been presented. From the Lyapunov stability analysis, it is shown that all the signals of the resulting closed-loop system are bounded and the tracking error surfaces remain within the prescribed performance bounds in the presence of unknown non-linear actuator faults. The simulation results and comparisons with the previous methods indicate the effectiveness of the proposed adaptive fuzzy FTC.