Disturbance Observer based Fractional-order Control for Free-floating Space Manipulator

This paper devotes to the precise joint space tracking control of the free-floating space manipulator. The system kinematics and dynamics with disturbance considered is first developed. The momentum conservation is adopted to solve the coupling between the joints and the spacecraft. To compensate for disturbance and reduce control gains, a high order sliding mode observer is designed, which ensures finitetime convergence of the estimation error. For improving the transient and steady-state performance, the fractional-order calculus is introduced to construct a novel terminal sliding surface. A continuous reaching law is designed to guarantee the system is chatteringfree. Compared with conventional controllers, the proposed method perfoms better in distubance rejection, improving tracking accuracy, and eliminating chattering. Theoretical analysis and simulation results are presented to verify the effectiveness of the proposed method.