An observer-based fault-accommodating controller for nonlinear systems in the presence of sensor failures

This paper addresses the issue of designing a fault accommodating control algorithm which, after a sensor fault occurrence, takes information about the degraded sensor into account and drives the system such that performance recovery is achieved. A general class of single input nonlinear systems is considered, containing also a disturbance term. An observer is used to reconstruct the degraded state variable, and is activated as soon as the Fault Detection and Identification unit signals the location and occurrence of a sensor fault. Asymptotical convergence of the observer within an arbitrary finite time is proved, under some assumptions about the plant structure.