Adaptive event-triggered tracking using nonlinear disturbance observer of arbitrarily switched uncertain nonlinear systems in pure-feedback form

Abstract

An adaptive nonlinear disturbance observer (NDO) strategy is proposed for event-triggered tracking of switched uncertain pure-feedback nonlinear systems with mismatched external disturbances and arbitrary switching. Contrary to existing control results using NDOs for switched nonlinear systems, the main contribution of this study is the development of a common NDO-based event-triggered tracker with a triggering law to handle arbitrarily switched unknown nonaffine nonlinearities. Using the common Lyapunov function approach, a recursive NDO-based tracker design methodology is investigated to guarantee that all the closed-loop signals are uniformly ultimately bounded, and Zeno behavior is excluded in the resulting event-triggering mechanism. In each recursive step, the same adaptive estimate terms in the control laws and the NDO are derived via the function approximation technique to compensate for mismatched and switched unknown nonaffine nonlinearities. Finally, simulation examples are considered to verify the effectiveness of the proposed control technique.