High-Precision Trajectory Tracking Control for Space Manipulator With Neutral Uncertainty and Deadzone Nonlinearity

This brief investigates the high-precision trajectory tracking control of space manipulator after capturing an unknown target. The neutral uncertainty induced by parameter variation poses great challenges to the controller design. Moreover, the existence of actuator deadzone nonlinearity makes the situation more complicated. In order to address the aforementioned difficulties, a novel control scheme is proposed in this brief. First, to reduce the conservativeness in the descriptions of uncertainties, the dynamic of space manipulator is described by an uncertain system with neutral uncertainty, state-dependent uncertainty, and norm-bounded uncertainty for the first time. Then, by incorporating a novel deadzone compensation control effort, a composite controller is proposed to attenuate these uncertainties and compensate the deadzone nonlinearity. Finally, stability and robustness analyses are carried out, and simulation results are given to demonstrate the effectiveness of the proposed methods.

I. Introduction

Precise trajectory tracking control, when an unknown space target is captured by the space manipulator, plays an increasingly important role especially in space debris removal, on-orbit assembly, satellite maintenance, and some other related on-orbit service missions [1]. Therefore, considerable attentions have been attracted to address this problem [2]–[4]. However, when an unknown target is captured, neutral uncertainty and other types of uncertainties will be induced for the space manipulator system. As a result, these uncertainties will degrade the system performances of trajectory tracking severely and even induce the instability of the whole system [1], [5]. Furthermore, due to the actuator imperfection, the actuator deadzone is often encountered, which will seriously deteriorate the control accuracy. Consequently, the conjunct effects of the uncertainties and deadzone nonlinearity will hinder the accomplishment of precise operations for space targets [6], [7]. Hence, further studies need to be performed to tackle the aforementioned problems.