Constrained Fixed-Time Terminal Sliding-Mode Control With Prescribed Performance for Space Manipulator System

This article focuses on the high-precision position tracking problem for the free-float space manipulator (FFSM) system subject to parametric uncertainties, input saturation, and state constraints. To this end, the screw-based dynamics using the Newton-Euler iterative method, with a global and unique attitude representation, are established; then, a chattering-free fixed-time sliding-mode control (FTSMC) scheme is developed based on the proposed dynamics model. A radial basis function neural network (RBFNN) with proper hidden layers and nodes is integrated into the proposed controller, while modeling approximation errors are well-inhibited by adaptive laws. Since the tracking error has been explicitly constrained by an exponential decay function, the Lyapunov analysis indicates that the transient and steady performance and state constraints can be guaranteed simultaneously. Simulation experiments taking an FFSM with six-degree-of-freedom (DOF) illustrate the effectiveness of the proposed control scheme from two aspects: joint-space positioning and trajectory tracking.