Backdrivable Redundantly Actuated Parallel Robot for Sensorless Physical Human-Robot Interaction

Abstract

This paper introduces a new redundantly actuated parallel robot capable of sensorless physical human-robot interaction. Three 3-DoF legs are attached to an end-effector platform through spherical joints. This architecture alleviates most parallel singularities, thus enabling a very large workspace. The use of quasi-direct-drive actuators yields a backdrivable robot with very low impedance, since all actuators are fixed to the base. Furthermore, since the actuators are force/torque controlled, internal antagonistic forces can be controlled without additional sensing devices. Experiments are carried out on a physical prototype and validate the large workspace and physical interaction capabilities of the robot.