Novel controller design for fault tolerant tracking with general additive faults and disturbances

Abstract

A formulation of the problem of fault tolerant tracking (FTT) in presence of general additive faults and disturbances is given. It is proved that a necessary condition for the FTT problem is that the plant is minimum‐phase. Then the problem is solved for the minimum‐phase descriptor systems, but possibly with zeros at infinity. The proposed overall controller consists of a feedback controller, which is stabilizing, and a feedforward controller, whose role is to achieve the tracking of an arbitrary reference signal by the controlled output. The feedback controller consists of a possibly unstable, improper and non‐minimum‐phase nominal controller, a fault estimator, and a fault compensator. The role of the nominal controller is to achieve a nominal tracking behavior in absence of faults. The role of the fault compensator is to achieve a nominal tracking behavior in presence of faults, in case that the fault estimation is accurate. However, the fault estimation need not to be accurate, if a design parameter, depending on the nominal controller, can be chosen small. Illustrative examples are given.