Potential Runaway Motion Volume in Task Space for Estimating The Probability of Occurrence of A Human-Robot Collision

The paper deals with a critical safety issue on a human-robot coexistence system which is highly expected to be introduced in such fields of manufacturing as cell production lines. We discuss a method for quantitatively estimating the probability of occurrence of a collision between a human and a fixed-type robot when it falls into a runaway state. We apply the concept of dynamic manipulability ellipsoid to compute the potential runaway space of a robot. Then, we conduct a psychological experiment in which each subject avoids abrupt approaching motion of the end effector of the robot and determine the collision simulation parameters. Further, we show an estimation procedure of protective separation distance taking into account the avoidance action on the participants' side. The study contributes to obtaining the protective separation distance required for a robot to be separated from a worker. We finally confirm that the experimental results validate the separation distance to converge.