Robust tracking control of uncertain nonlinear systems using disturbance observer

In this paper, we propose the disturbance-observer-based robust tracking control for a class of uncertain nonlinear systems with unknown external disturbance and system uncertainty. Aiming at the unknown disturbance and the unknown system uncertainty, the disturbance observer is designed to well monitor them. Invoking backstepping and disturbance observer based techniques, the robust tracking control is developed to tracking the desired system output in the presence of unknown system uncertainty and external disturbance. Under the proposed disturbance-observer-based robust tracking control, uniform asymptotical convergence of all closed-loop signals are guaranteed via Lyapunov analysis. Numerical simulation results are given to illustrate the effectiveness of the proposed tracking control.