Withdrawal strategy for human safety based on a virtual force model

The Human-Robot Interaction gets increasingly closer. In consequence, human safety has become a key issue for the success of the symbiosis between humans and robots. When the minimum distance between a human and a robot is too short, it can be naturally considered that the probability of a collision increases. Therefore, we consider that the robot should increase the distance to the human when the human is getting closer. We propose Withdrawal strategy as a method that aims to increase the distance by moving the end-effector not only away from the human but also to a parking position that can be previously assessed to be safer. To withdraw the end-effector, we use a virtual force model consisting of two virtual forces: a repelling force exerted by the human and an attractive force exerted by the parking position. We carry out experiments using a human-sized humanoid robot and five human subjects, and report the task completion time to evaluate the efficiency of the robot when performing a simple task.