Parallel robot with proprioceptive actuation for low-impedance sensorless pHRI

This paper presents a kinematically redundant 9-DoF parallel robot engineered for seamless, sensorless physical human-robot interaction. The robot features three identical 3-DoF RU/2-RUS legs that connect a reconfigurable platform to the base via spherical joints. By configuring all actuators on the base, the robot achieves significantly lower moving mass and inertia. By employing backdrivable direct-drive motors, the system realizes proprioceptive actuation, enabling an intuitive, low-impedance, and high-bandwidth interaction. An impedance control strategy is developed on SE ( 3 ) × R 3 , and a stability analysis using singular perturbation theory highlights the crucial role of actuator dynamics and thus the significance of the choice of the actuation strategy. Experimental results confirm the robot’s stability, extended workspace, and effective human-robot interaction performance.