Virtual-base modeling and coordinated control of a dual-arm space robot for target capturing and manipulation

A dual-arm space robotic system has large potential in on-orbit servicing missions, such as satellite repairing, large space structure construction and space debris removal. However, there exist multiple dynamic couplings between the base, the manipulators and the target, bringing large challenge to the motion planning and control. In this paper, avirtual-base modeling method (VBM) and coordinated control strategy are proposed for a dual-arm space robot. One of the arms' end-effector is considered as the virtual base, and the other bodies, including each link of the arms and the center body of the spacecraft, form a combined manipulator. Correspondingly, we derive the kinematic and dynamic equations of the combined manipulator with the virtual base, taking it as a hyper-redundant space manipulator. Furthermore, the coordinated trajectory planning and control methods are presented for capturing and manipulating a space target. For the pre-contact stage, the virtual base and end-effector are controlled simultaneously to track the desired trajectory in the inertial space. During contact, the operational force is regulated using admittance control law, by simplifying the operational forces of the two arms as the equivalent operational force of the combined manipulator. After the target is captured and fixed to the two arms, its pose is adjusted by simultaneously controlling the trajectory and the operational force of the virtual base and the combined manipulator. Finally, a co-simulation system is created based on MATLAB/Simulink and MSC.ADAMS. Simulation results verify the effectiveness and robustness of the proposed methods.