Contact control for grasping a non-cooperative satellite by a space robot

In this paper, the contact control problem of a space robot to grasp a non-cooperative satellite is investigated in detail, and a new capture control strategy is proposed. Firstly, the dynamic equation of the robot system is derived based on the multibody dynamics theory, and a modified Hertz model is used to describe the contact force between the robot end-effector and the target satellite. Then, a novel position-based impedance control strategy for capturing the target satellite is proposed. This control strategy is to capture the target satellite by realizing soft contact between the end-effector and the target satellite, thus the target satellite will not depart from the end-effector after their contact. Different from the other existing capture control strategies, the proposed strategy needs only the kinematic information of the space robot, so the control performance requirement is lower and is easier to implement in practice. To verify the validity of the proposed capture control strategy, simulations are conducted at the end of this paper, and the results indicate that the target satellite can be grasped effectively using the proposed capture control strategy if the motion of the target satellite is translational or tumbling.