Auricularis muscles based control interface for robotic extra thumb

Abstract

In this paper we present a prototype interface to control an extra robotic thumb using surface electromyograph signals (sEMG) from Auricularis muscles located around the ear. This system is to be used to evaluate the ability of the brain to adapt to a change of body architecture, in this case by adding supernumerary limbs. Proprioceptive feedback is given via several different channels. The extra robotic thumb is a 3-degrees of freedom robotic thumb attached to the palm of the left hand. The user can control the position of the fingertip by contracting auricularis muscles around the ear. Auricularis muscles, as facial muscles, does not have muscle spindle, so they lack deep sensation feedback, in order to compensate this we use a head mounted display device to relay position information in the periphery of the visual area of the user. The extra robotic thumb also has a force sensor in the fingertip, and we feedback this information as electrical stimulation signal proportional to the contact force. We apply this signal to the palm of the hand where the thumb is attached. The extra robotic thumb is located in a position where it is possible for it to reach and touch the tips of the other fingers on same hand, which allows it to grasp and hold objects. We also present a proof of concept experiment where the user is asked to use the extra robotic thumb to reach specific fingers without being able to look directly at it, guiding it only by head mounted display device and electrical stimulation feedback.