Fault estimation for a class of interconnected non-linear systems with time-varying delay using robust adaptive unknown input observers

In this paper, a fault detection and estimation scheme for a class of interconnected non-linear systems with time-varying delays and sensor, actuator and component faults is presented. In no fault condition, a set of H-infinity observers are used to detect the faults. With the aid of H-infinity performance index, the common assumption regarding the observer matching condition is no longer required. A novel descriptor system approach and the unknown input observer technique are invoked to estimate both the system states and the faults for non-linear systems which satisfy Lipschitz condition, when a H-infinity condition is satisfied. Stability of the observers is proved with the aid of Lyapunov-Krasovskii approach. A simulation example is provided to illustrate the effectiveness of the proposed fault estimation scheme. The results show the effectiveness of approach.