Actuator fault-tolerant control based on invariant set separation

In this paper an actuator fault-tolerant control (FTC) strategy based on invariant set computation is presented. The proposed scheme is based on a bank of observers which match different fault situations that can occur in the plant. Each of these observers produces an estimation error with a distinctive behavior when the observer matches the current fault situation in the plant. With the information of the estimation errors from each of the considered observers, a fault diagnosis and isolation (FDI) module is able to reconfigure the control loop by selecting the appropriate stabilising controller from a bank of precomputed control laws, each of them related to one of the considered fault models. The decision criteria of the FDI is based on the computation of invariant sets of the estimation errors for each fault scenario and for each control configuration. Conditions for the design of the FDI module and for fault- tolerant closed-loop stability are given, and the effectiveness of the approach is illustrated with an example.