Tele-manipulation with a humanoid robot under autonomous joint impedance regulation and vibrotactile balancing feedback

This work presents an enriched human-machine interface for performing effective tele-manipulation using a humanoid robot. To provide the slave with the ability to dexterously interact with the remote environment, we implement an autonomous impedance controller that regulates the slave´s joints stiffness and damping according to the manipulation loading conditions. In the proposed strategy, free-space operations are performed with compliant limbs to ensure safe interactions during unforeseen collisions on the whole-arm together with a soft behaviour at the initial phase of contact. During the manipulation task, the designed controller accounts for the arm configuration and the direction/amplitude of the external force sensed at the end-effector to stiffen the humanoid arm joints, permitting to handle the task loads. Experiments performed on the compliant humanoid robot COMAN demonstrate the effectiveness of this human-inspired impedance controller during a teleoperated pick-and-place task. The interaction forces during manipulation can destabilize the floating base humanoid robot. To address this concern we also investigate the operators ability to rely on a cutaneous feedback of the slave´s balance state to adjust their teleoperation strategy when required so as to complete the task while maintaining the slave´s balance. A comparative study shows that the proposed vibrotactile feedback allows for a proper recognition of the slave´s drop of stability during interaction tasks and that the tactile guidance leads to enhanced teleoperation performances characterized by a significantly lower number of falls.