Fractional-order resolved acceleration control for free-floating space manipulator with system uncertainty

This paper investigates the task-space trajectory tracking control of free-floating space manipulator (FFSM) with system uncertainty considered. The dynamics of the FFSM, as well as the mapping between the task space and the joint space, are first established. To estimate and compensate for the uncertainty, a disturbance observer is designed which ensures the estimation error converges to zero within finite time. To improve the task-space tracking performance, the fractional-order resolved acceleration control (FORAC) scheme is proposed. The proposed control method utilizes the fractional-order integral to construct a sliding surface and stirs the tracking error to converge along this surface, which improves the robustness and transient performance of the entire system. Besides, the estimated uncertainty is introduced into the controller to compensate for the influence of actual system uncertainty, and reduce the control gains. Theoretical analysis is given to show the closed-loop behavior of the proposed controller and observer. Simulations are conducted to verify the effectiveness of the proposed method.