Adaptive observer for a class of nonlinear systems with time-varying delays

Abstract

The adaptive observer design problems have been extensively studied in literature for both linear and nonlinear systems. Some researches have also been carried out on adaptive observer design for linear time-delay systems, but there is no significant work on adaptive observer design for nonlinear time-delay systems. In this work, the adaptive observer design problem for a class of nonlinear time-delay systems is considered. The observer is designed for the nonlinear systems whose nonlinear functions satisfy Lipschitz condition. Like conventional adaptive observers for the systems without time delays, this observer also estimates both states and unknown parameters simultaneously. For this property, it will be very much useful for many real-time systems where time delays cannot be avoided. The sufficient conditions for existence of the observer are derived using the linear matrix inequality approach. With the help of a numerical example, effectiveness of the proposed observer is demonstrated. Copyright (c) 2012 John Wiley & Sons, Ltd.