Quantitative safety guarantees for physical human-robot interaction

If robots are to be introduced into the human world as assistants to aid a person in the completion of a manual task two key problems of today's robots must be solved. The human-robot interface must be intuitive to use and the safety of the user with respect to injuries inflicted by collisions with the robot must be guaranteed. In this paper we describe the formulation and implementation of a control strategy for robot manipulators which provides quantitative safety guarantees for the user of assistant-type robots. We propose a control scheme for robot manipulators that restricts the torque commands of a position control algorithm to values that comply to preset safety restrictions. These safety restrictions limit the potential impact force of the robot in the case of a collision with a person. Such accidental collisions may occur with any part of the robot and therefore the impact force not only of the robot's hand but of all surfaces is controlled by the scheme. The integration of a visual control interface and the safety controlled robot allows the safe and intuitive interaction between a person and the robot. As an example application, the system is programmed to retrieve eye-gaze-selected objects from a table and to hand them over to the user on demand.