Observer-based fault detection and accommodation for nonlinear time-delay systems with a prescribed performance mechanism

In this paper, delay-independent fault detection and accommodation (FDA) control is developed for a class of uncertain nonlinear time-delay systems with multiple time-delay faults and external disturbances. Compared with the existing results, the system states are unmeasurable and the bounds of model uncertainties and the disturbances only exist but are unknown. A novel parameter-varying observer is designed for fault detection and state estimation. The modified prescribed performance bound (PPB) is used as detection threshold. It is shown that the state estimate error is guaranteed within a PPB before the fault occurs. Then, a backstepping-based adaptive fuzzy fault accommodation controller is designed and activated after the detection, which compensates multiple time-delay faults and guarantees the state estimate error which has violated the performance constraint returns into a new PPB. The effectiveness of the proposed FDA method is illustrated through a simulation example on the robot manipulator system.