Somatosensory feedback improves operability of extra robotic thumb controlled by vestigial muscles

Abstract

One of the challenging problems of the conventional robotic prosthesis or wearable systems is their difficulty in the coordination of multiple degrees of freedom. Newly acquired body representation of the wearable robotic extremities could be helpful for a user to control the device as if they were a part of a user's body. In our previous research, we proposed posterior auricular muscles (PA muscles) for control of the Extra Robotic Thumb (ERT) which we developed. PA muscle is one of vestigial muscles which do not have any body representation, while a daily used muscle has already had a certain body representation related with its functionality. However, it is hard for a user to recognize a posture of the ERT because a user cannot get afferent information such as somatosensory of the ERT. In this paper, to improve an operability of the ERT when controlling by PA muscles, joint angle of the ERT is presented to the back of the left hand by two vibrators to provide somatosensory feedback. Through experiments, a user can control the ERT more smoothly when the vibrators display joint angle of the robotic finger.