Augmented observer-based actuator fault diagnosis for nonlinear systems

An actuator fault diagnosis approach is proposed for linear systems and a class of nonlinear systems with Lipschitz constraints. Considering the actuator fault as an auxiliary state vector, an augmented system is constructed. And then an augmented state observer is designed by the linear matrix inequality technique. The asymptotic estimates of the original system state vector and the actuator fault term are obtained simultaneously. Stability and convergence of the proposed observer is analyzed based on the Lyapunov theory. Finally, the proposed approach is applied to actuator fault diagnosis for the satellite attitude control system. Simulation examples illustrate the effectiveness of the presented method.