Global Practical Tracking via Adaptive Output-Feedback for A Class of Uncertain Nonlinear Systems With Polynomial Output Depending Growth Rate

This paper investigates the problem of global practical tracking by adaptive output-feedback for a class of uncertain nonlinear systems. Unlike closely related works, the systems have unmeasured states of growth with a growth rate polynomial of output-input multiplying an unknown constant. Mainly because of the presence of unknown polynomial function of the input, this kind of tracking problem is very different from the previous research. Inspired by the related stabilization problem, an observer is constructed by introducing two novel dynamic gains, and an adaptive output-feedback controller is designed to make all the states of the closed-loop system globally bounded, as well as the tracking error will be prescribed arbitrarily small after a finite time. A numerical example is provided to illustrate the effectiveness of the theoretical results.