Adaptive output feedback tracking for time-delay nonlinear systems with unknown control coefficient and application to chemical reactors

In this paper, the problem of global adaptive output feedback tracking is considered for a class of highly nonlinear time-delay systems with unknown control coefficient and relaxed lower-triangular growth constraints. Based on the non-separation principle, a non identifier-based adaptive output feedback controller is proposed by designing a novel update law of the dynamic gain in observer and controller. The novel gain can simultaneously compensate the uncertain parameters, the output-polynomial growth rate and the unknown time-varying delay. The proposed controller is well universal attributed to using the non-identification adaptive mechanism, and all design parameters are easy to get by simple calculation. With the help of Lyapunov-Krasovskii functionals and Barbalat's lemma, it is shown that the solutions of the resulting closed-loop system are globally uniformly ultimately bounded by improving the backstepping design and dynamic high-gain scaling approach; the adaptive tracking is achieved under any small pre-given tracking error. Finally, the effectiveness of the proposed controller is illustrated by two examples. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

This paper proposes a non identifier-based adaptive output feedback controller for highly nonlinear time-delay systems, achieving global output tracking. The control parameters can be easily obtained through simple calculation, and the stability of the system is demonstrated using Lyapunov-Krasovskii functionals and Barbalat's lemma.