Manipulability optimization for coordinated motion control of multi-arm space robots

By maximizing manipulability, the coordination of multi-arm can be enhanced. In this paper, a method to optimize the manipulability index of cooperative manipulation for a free-floating multi-arm space robot is proposed. Firstly, the manipulability optimization is formulated as a nonlinear optimize problem at position level which is hard to solve online. By redefining constraint equation and manipulability index, it is transformed to a constrained quadratic program problem at velocity level incorporating joint velocity physical limits, which generates joint velocity commands to control the multi-arm to complete predefined tasks. Owing to dynamic coupling effects and closed chain constraints formed by cooperative manipulation, the manipulability index is more complex than that of fixed-base or mobile-base manipulators. Hence, the gradient of the index is approximated by numerical algorithms. Simulations based on a dual-arm space robot model are conducted and the results prove that the proposed method is efficient to optimize the manipulability index.