Global output-feedback stabilization for high-order nonlinear systems with additive input disturbances

Abstract

This paper is devoted to the global output-feedback stabilization for a class of high-order nonlinear systems with additive input disturbances and unknown growth rate. To compensate these system unknowns, a time-varying output-feedback control design scheme is proposed. Detailedly, a time-scaling transformation is first introduced, and then under the assumption that all system states are available for feedback, a state-feedback controller is designed. By replacing the unmeasured system states in the designed state-feedback controller by its appropriate estimation which is builded by an appropriate time-varying observer, the resulting output-feedback controller is thus obtained. It is shown that all the signals of the closed-loop system are bounded, and furthermore, the original system states and observer states converge to zero. It should be pointed out that, the additive input disturbances may not be periodic or bounded by any known constant, and hence essentially more general than those studied in the existing related works.