Global Practical Tracking via Adaptive Output-Feedback for A Class of Uncertain Nonlinear Systems

This paper considers the global practical tracking via adaptive output-feedback for a class of uncertain nonlinear systems with function control coefficients. The feature of the system under investigation is that the control coefficients are functions of output, and the growth rate is of polynomial-of-output multiplying an unknown constant. To solve the problem, a high-gain observer is introduced to reconstruct the unmeasured system states, and then an adaptive output-feedback controller is designed. Different from the existing related literature, only a high-gain is introduced to overcome the serious unknowns caused by the growth rate and the reference signal, and the system nonlinearities reflected by the control coefficients and the growth rate. The designed controller guarantees that all signals of the closed-loop system are bounded, and furthermore, the tracking error will be ultimately prescribed sufficiently small.