Delay-independent fault detection and accommodation for non-linear strict-feedback systems with unknown time-varying delays

This study presents a time-delay-independent fault detection and adaptive accommodation control scheme for strict-feedback systems with unknown multiple time-delayed non-linear faults. The magnitude and occurrence time of the multiple faults with unknown time-varying delays are unknown. First, a detection threshold is derived to design a time-delay-independent fault detection scheme for the time-delay systems and the fault detectability is analysed. Second, an adaptive approximation design for a time-delay-independent fault accommodation control is addressed. The adaptation technique is applied to learn weights of function approximators and thus the multiple faults can be compensated after the detection of the first fault. It is shown that all signals of the closed-loop system are semi-globally uniformly ultimately bounded and the tracking error converges to an adjustable neighbourhood of the origin.