Output-feedback robust adaptive backstepping control for a class of multivariable nonlinear systems with guaranteed L∞ tracking performance

This paper is devoted to output-feedback adaptive control for a class of multivariable nonlinear systems with both unknown parameters and unknown nonlinear functions. Under the Hurwitz condition for the high-frequency gain matrix, a robust adaptive backstepping control scheme is proposed, which is able to guarantee the L tracking performance and needs only one parameter to be updated online regardless of the system order and input-output dimension. To cope with the unknown nonlinear functions and improve the tracking performance, a kind of high-gain K-filters is introduced. It is proved that all signals of the closed-loop system are globally uniformly bounded. Simulation results on coupled inverted double pendulums are presented to illustrate the effectiveness of the proposed scheme. Copyright (c) 2012 John Wiley & Sons, Ltd.