Adaptive fault identification for a class of nonlinear dynamic systems

This paper is concerned with the diagnosis problem of actuator faults for a class of nonlinear systems. It is assumed that the upper bound of the Lipschtiz constant of the nonlinearity in the faulty system is unknown. Then, a new nonlinear observer for fault diagnosis based on an adaptive estimator is proposed. Moreover, by making use of the designed adaptive observer with on-line update control law without σ-modification condition to approximate the faulty system, it is proved that the estimate error of the adaptive control parameter, the output observation error and the error between the system fault and the corresponding estimate value are uniformly ultimately bounded via Lyapunov stability analysis. Finally, simulation examples are provided to illustrate the efficiency of the proposed fault identification approach.