Kinematic and dynamic manipulability analysis for free-floating space robots with closed chain constraints

Abstract

This paper presents the manipulability analysis of free-floating multi-arm space robots. Evaluation of manipulator capability is useful both in the design and in the operation phase. After capturing a target, closed kinematic chains are formed with multi-arm cooperative manipulating a common object. Owing to the dynamic coupling effect, the manipulability analysis of free-floating systems is more complex than that of ground-fixed closed chain systems. To analyze the cooperative manipulability, kinematic and dynamic formulations for the free-floating closed chain systems are firstly derived. The formulations describe the mapping of joint velocities and torques, respectively, to task velocities and forces, as well as joint torques to task accelerations and forces, by using the generalized Jacobian matrices. Next, the well-known concepts of manipulability ellipsoid, manipulability measure and task compatibility of the free-floating closed chain system are formally extended. Besides, a new approach called scaling factor method is used in the analysis of the task compatibility, which is more accurate compared with the manipulability ellipsoid method. Three applications of the performance indices are considered: (1) the feasibility analysis for a given task, (2) the trajectory planing giving a desired task path, and (3) configuration optimization with different task requirements. The proposed index is proved a very efficient tool that can be utilized in the cooperative manipulation tasks for free-floating space robotic systems.