Abstract
In recent years, there has been great interest in the possibility of using artificial limbs as an extension of the human body as well as replacement of lost limbs. In this paper, we develop a sixth finger system as an extension of the human body. We then investigate how an extra robotic thumb, that works as a sixth finger and gives somatosensory feedback to the user, modifies the body schema, and also affecting the self-perception of existing limbs. The sixth robotic finger is controlled with the thumb of the opposite hand, and contact information is conveyed via electrostimulation to the tip of the thumb controlling the movement. We conducted reaching task experiments with and without visual information to evaluate the level of embodiment of the sixth robotic finger and the modification of the self-perception of the finger controlling the system. The experimental results indicate that not only the sixth finger is incorporated into the body schema of the user, but also the body schema of the controlling finger is modified; ability of the brain to adapt to different scenarios and geometries of the body is also implied.
Highlights
Artificial limbs had been used for long time as prostheses, and it has been studied how much are these artificial limbs embodied to the users self-perception of the body [1]
We presented a sixth finger system composed of an extra robotic thumb attached to the left hand, that simulates a second thumb in that hand and has a force sensor in its tip; a thumb motion capture, that attaches to the right hand, and captures the movements and position of the tip of the thumb in that hand, to mirror its movements into the extra robotic thumb
We showed the performance of this sixth finger device with somatosensory feedback measured via a pointing task by comparing two groups of subjects; the subjects of the first group were allowed to see the sixth finger device during the test, and the subjects of second group were not allowed to see the sixth finger device during the test
Summary
Artificial limbs had been used for long time as prostheses, and it has been studied how much are these artificial limbs embodied to the users self-perception of the body [1]. It has been shown that an increase in embodiment improves the performance and comfortability of these artificial limbs [2]. Great interest has arisen on the possible use of artificial limbs not just as replacement of lost limbs, and as an extension of the human body. Some research groups have studied the use of artificial limbs as extra limbs, and their possible applications [3, 4]. Extra limbs offer the possibility to increase workspace, dexterity, strength and reduce fatigue of the user [5]. Extra limbs require new control strategies because extra limbs perform actions that the users have not experienced. Control strategies of extra limbs proposed previously can be divided into two approaches.
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