“…Distance measuring is a procedure, before collision avoidance, to determine the possibility of collisions. As computing the distance from a manipulator to obstacles using accurate topology is very time consuming, many researchers have been trying to find efficient approaches to speed up the calculation, for example, covering the links of a robot manipulator with polytope, polyhedron [5], [6], sphere [7], [8], [10], [11], ellipsoid, etc., which can significantly reduce computing time. Based on the measured distance between the robot arm and obstacles in the environment, collision avoidance algorithms are then used to steer the movement of a robot arm away from obstacles while fulfilling its task.…”