Reduced-order observer-based output-feedback tracking control of nonlinear systems with state delay and disturbance

In this paper, we investigate the problem of output-feedback tracking control for a class of nonlinear SISO systems in the strick-feedback form, which are subject to both uncertain delay-related functions and disturbances. A reduced-order observer is first introduced to provide the estimates of the unmeasured states. Then, an output-feedback controller is recursively designed based on the backsteppng method. By constructing an appropriate Lyapunov-Krasovskii functional, we prove that all the signals in the closed-loop system are bounded. The tracking performance is guaranteed by suitably choosing the design parameters. Finally, a simulation example is provided to demonstrate the effectiveness of the proposed control algorithm. Copyright (C) 2009 John Wiley & Sons, Ltd.