Event-triggered practical tracking control for an uncertain free-flying flexible-joint space robot with dead-zone input

Abstract

This paper is devoted to the event-triggered practical tracking control of a class of uncertain free-flying flexible-joint space robots (FFSRs) under unknown dead-zone input. The remarkable characteristics of the paper are reflected by the coarse information on the reference signal since its time derivatives are not necessarily available for feedback, and moreover, by the serious uncertainties which contain unknown nonlinear dynamics, parameters without known nominal parts, and the external disturbance. Then, the traditional control schemes on this topic become incapable. For this, a novel event-triggered control scheme is proposed by a skilful use of adaptive technique. Specifically, a dynamic gain with a smart choice of its updating law is incorporated into the vectorial backstepping framework, which not only overcomes the serious uncertainties contained in the system and dead-zone input but also handles the influence of sampling errors. Consequently, two adaptive event-triggered controllers are designed which ensure that all the states of the resulting closed-loop system are bounded while the system output practically tracks the reference signal, along with the exclusion of the Zeno phenomenon. Finally, an example is given to validate the effectiveness of the proposed theoretical results.