Active Fault-Tolerant Control Against Intermittent Faults for State-Constrained Nonlinear Systems

Intermittent faults (IFs) are characterized by random occurrence and disappearance, making fault diagnosis and fault-tolerant control (FTC) more challenging compared to permanent faults. This article is devoted to active FTC (AFTC) for full-state-constrained nonlinear systems with unknown mismatched disturbances and actuator IFs. By integrating fault diagnosis and controller design, a novel fault-diagnosis-based FTC strategy is proposed to compensate for the IF, and a sufficient condition is established for the fault detectability of the proposed scheme. Besides, the fault detection delay and estimation error, considered new external disturbances, are compensated adaptively along with the mismatched disturbances. The fault-tolerant controller is designed to guarantee that all signals in the system are bounded and the tracking error converges into a small neighborhood near the origin in finite time, without violating the predefined asymmetric time-varying constraints of the states. A numerical simulation example and an application to the active steering system (ASS) of vehicle chassis are provided to demonstrate the effectiveness of the developed AFTC strategy.