Simultaneous Sensor and Actuator Fault Detection, Isolation and Estimation of Nonlinear Euler-Lagrange Systems Using Sliding Mode Observers

In this paper, the problem of simultaneous sensor and actuator fault detection, isolation and estimation (FDIE) for nonlinear Euler-Lagrange (EL) systems is addressed. First, an output redefinition and a state coordinate transformation are employed that do not use any a priori knowledge about the system nonlinearities to decouple the system into two subsystems where each subsystem is only affected by either a sensor or an actuator fault. Then, two separate sliding mode observers (SMO) are employed to estimate sensor and actuator faults corresponding to these subsystems. Simulation results are provided for an Autonomous Underwater Vehicle (AUV) that is modeled by EL equations. The results demonstrate the capabilities and benefits as well as the performance of our proposed FDIE approach as compared to the existing results in the literature.