Sensor and Actuator Fault-Tolerant Fuzzy Adaptive Control for Fractional-Order Strict Feedback Nonlinear Systems Subject to Input Saturation

This paper introduces a fault-tolerant fuzzy adaptive controller for a specific class of strict-feedback fractional-order nonlinear systems. Systems are susceptible to actuator and sensor failures, input saturation, and external disturbances. The proposed control scheme effectively addresses four types of faults that affect sensors and actuators, including additive faults such as bias, drift, and loss of accuracy, as well as the multiplicative fault of loss of effectiveness. In contrast to the complexity associated with the back-stepping technique, the proposed approach relies on state transformation. Fuzzy logic systems (FLS) are incorporated to approximate unknown smooth nonlinear functions. A tracking-error observer is introduced to estimate unknown new states, and the properties of the reciprocal function and the strictly positive real function (SPR) are leveraged to overcome the unavailability of original state variables. Stability analysis of the closed-loop system is conducted using the Lyapunov theory. The results of the numerical simulation are presented to validate the feasibility and effectiveness of the proposed controller.