Abstract: The problem of estimating collision between the robot links and the object in environment is translated into solving the minimum distance between the points on the link center lines and on the objects’ surface, so the successful probability to avoid collision is expressed by the distance between center lines and obstacle during self-motion process. The weighted average of all points on center lines, defined as colli-sion-avoidance quotient (CAQ) The robot’s capability in colli-sion-avoidance is represented, which depends only upon the robot’s structural parameters and the pose of the end-effector. Any pose of end-effector has an individual CAQ. The average of CAQs in the workspace with weight of the distribution probability of tasks is defined as global collision-avoidance quotient (GCAQ), which represents the robot’s global capabil-ity of collision-avoidance in the workspace. As an example, the GCAQ of a 7-DOF redundant manipulator is calculated for two cases. Finally the influence of the links’ dimension on GCAQ is analyzed.

Key words: Capability of collision-avoidance, Collision-avoidance quotient, Redundant robot, Self-motion