Global output feedback practical tracking for time-delay systems with uncertain polynomial growth rate

In this paper, the problem of global practical output tracking is investigated by output feedback for a class of uncertain nonlinear time-delay systems. Compared with the existing results, we allow the nonlinearities to nonlinearly grow in unmeasured free-delay and time-delay states with the uncertain time-delay output polynomial growth rate. Based on the ideas of universal adaptive control and dead zone, we develop an adaptive high-gain observer with a novel monotone non-decreasing dynamic law. By the Lyapunov-Krasovskii theorem, a memoryless controller is constructed to achieve global practical output tracking for uncertain nonlinear systems with multiple time delays. Finally, two examples are given to illustrate the usefulness of our results.