Abstract: The coupling of passive joints and actuated joints in passive redundaney space robots are analyzed, and formulated a measure about the coupling which can be considered as a performance index in planning robot motion. The kinematics singularity of passive redundancy robots and the difference about the singularity between the passive and the non-passive redundaney robots also are analyzed. A passive redundancy robot manipulability index which also can be used in planning robot motion, is defined. The concept of “proximate self-motion” for the passive redundancy robot, is presented the “proximate self – motion” can optimum the motion when robot completes a end-effector mission. In the simulation fuction, a planar 3-DOF space station robot exbibits the ability of the “proximate self – motion” in avoiding the kinematics singularity.

Key words: Passive-joint, Redundancy, Space-robot