Simultaneous fault and state estimation in time-delay nonlinear systems having triangular form

This paper investigates the problem of simultaneous fault and state estimation of either bounded state or globally Lipschtiz nonlinear systems subject to time delay and unknown input. We assume that the system has a triangular structure and the fault is a scalar and polynomial time dependent function. Based on the Lyapunov analysis method, we show that the observer design is related to neither delay dependent nor delay independent conditions, irrespective of the size of the delay. Simulation results along with a proof of convergence of the observer are given to highlight the efficacy of the proposed design.