Robust adaptive observer for nonlinear time-delay systems with disturbances and uncertainties

AbstractA method of designing robust adaptive observer for nonlinear continuous-time systems with time-delays is presented. It is assumed that the nonlinear functions of the system satisfy Lipschitz condition. The observer is derived considering plant disturbances, structured parameter uncertainties and unknown parameters. Like any other adaptive observer for nonlinear systems with ideal working conditions, it also simultaneously estimates both the states and unknown parameters. This property is very much useful for many applications like fault diagnosis. The convergence of the state errors and estimated unknown parameters are analysed by H∞-control. The sufficient conditions for the existence of the observer are determined and expressed in linear matrix inequality form. With the help of a numerical example, the effectiveness of the proposed observer is demonstrated.