ACTIVE DOCKING OPERATION OF DUAL-ARM SPACE ROBOT CAPTURE SATELLITE FORCE/POSTURE IMPEDANCE CONTROL BASED ON FINITE TIME CONVERGENT

The force and position impedance control of dual-arm space robot capture satellite active docking operation is studied. In order to prevent the joints of the space robot from being damaged by impact force generated when contact and impact between the end-effector of the manipulator and the satellite during the process of capture operation, a spring damping buffer device (SDBD) is added between each joint motor and manipulator. In order to solve the problems of nonholonomic dynamic constraints in the process of capture operation and the coordinated control of the closed-chain hybrid system after capture, combined with Newton's third law, velocity constraints of captured points and closed-chain geometric constraints, the closed-chain dynamic model of hybrid system after capture operation is obtained, and the impact effect and impact force are calculated by the law of conservation of momentum. The Jacobian matrix between the docking device relative to the base of space robot is established by analyzing the kinematic relationship of the docking device in the base coordinate system. On this basis, a second-order linear impedance model based on force is established to achieve high precision output force control of the docking device. Considering that the active docking operation requires the controller to have the characteristics of fast convergence and high precision control of position and attitude, a nonsingular fast terminal sliding mode impedance control strategy which combining the advantages of terminal sliding mode and super-twisting sliding mode is proposed. This control strategy can not only realize the rapid response of position, attitude and output force in the process of active docking operation, but also effectively solve the chattering problem of sliding mode to ensure the position, attitude and output force high precision control. The stability of the closed-chain hybrid system is proved by Lyapunov theorem. The impact resistance of the buffer device and the effectiveness of the proposed impedance control strategy are verified by numerical simulation.