Finite-time fuzzy control for constrained nonlinear systems with non-affine faults, input saturation and dead-zone

This paper investigates the issue of finite-time adaptive fuzzy output feedback control for a category of non-strict feedback nonlinear systems, which are affected by non-affine nonlinear faults and full-state constraints, while also considering the presence of saturation and dead-zone nonlinearities in the input signal. To address the nonlinear faults and uncertain functions within the system, the universal approximation capability of fuzzy logic systems is utilized, and then a fuzzy state observer is developed. Simultaneously, the Butterworth low-pass filter and the properties of fuzzy basis functions are leveraged to address the algebraic loop problem caused by the non-strict feedback structure. Based on finite-time stability criteria, within the framework of the backstepping control design method, an adaptive fuzzy controller is formulated by incorporating logarithmic barrier Lyapunov function, where the dynamic surface control technique, assisted by first-order linear filters, is employed to avoid the problem of “complexity explosion”. Stability analysis shows that the presented control scheme can ensure that all signals within the closed-loop system remain bounded, and that the tracking error converges to a small neighborhood around the origin in finite time, while ensuring that all states remain within a predefined set. Finally, two practical examples are presented to validate the effectiveness of the proposed control design approach.