A Novel Proprioceptive Feedback System for Supernumerary Robotic Limb

A novel system to provide the user with proprioceptive feedback from a supernumerary robotic limb through vibrotactile stimulation is presented. The system is composed of a dedicated electronic board that converts the robot state, acquired through serial communication, into a vibration amplitude-frequency value and commands up to sixteen eccentric motors, placed on the user’s leg skin. The system is designed to allow the subject to have cues on the robot state even without visual feedback. Two different feedback encoding paradigms, one based on a kinematic approach and the other on a dynamic one, have been tested in three healthy subjects to validate the platform. In a planar task and with slow robot motions, conveying the robot state through the cartesian position (kinematic method) allows to achieve hugely better (d=4.278) performance than using joint torques (dynamic approach) or non-informative feedback.