Abstract: Aiming at the control problem of space robot with load capture, a sliding mode variable structure control method based on target mass observer is proposed, considering the joint flexibility of manipulator and the unknown mass of noncooperative target. Firstly, aiming at the problem of unknown quality of space non cooperative target, an improved least square iterative algorithm is designed to realize online identification of noncooperative target quality. Then, the dynamic model of flexible joint space robot on floating base is established by using Lagrange method and the principle of moment of momentum conservation. According to the rigid flexible coupling characteristics of the dynamic model, the system model is approximately decomposed into fast and slow varying subsystems based on singular perturbation theory. For the slow varying subsystem, the sliding mode variable structure controller is designed to ensure the robustness and dynamic characteristics of the system. For the fast changing subsystem, the feedback compensation control algorithm based on the speed difference is designed to suppress the residual vibration of the flexible joint and ensure the control accuracy. Finally, the mechanism of fast and slow subsystems is analyzed by experiments, and the effectiveness of the control method is verified.

Key words: flexible joint, space robot, singular perturbation theory, sliding mode control, mass observer