Reconstruction of actuator fault for a class of nonlinear systems using sliding mode observer

The present paper proposes a sliding mode observer (SMO) for detection and isolation of actuator faults for a class of uncertain nonlinear systems (Lipschitz nonlinear systems). The sufficient condition of stability of the proposed SMO has been derived and expressed as Linear Matrix Inequalities (LMIs). The design parameters of the proposed SMO are determined by using LMI techniques. The constraint of the switching gain has been determined such that the proposed SMO satisfies the reachability condition. Then the equivalent output error injection is employed to reconstruct the actuator fault based on the structure of the uncertainty. The effectiveness of the proposed SMO in reconstructing actuator fault has been illustrated considering an example of a single-link flexible joint robot system and has been found to be satisfactory even with the presence of sensor noise.