An Electric Cosmetic Prosthetic Hand with Vibrotactile Sense

Prosthetic hands are developed to replace lost hands. However, it has been hard to ensure the same level grasping and manipulating objects as human hands and the cosmetic appearance is also important. In a previous work, Rehand II: an electric and cosmetic prosthetic hand was developed. Its function is limited to simple object grasping, but it has the cosmetic appearance and is relatively light. This paper aimed to improve Rehand II by introducing tactile sense. Tactile sense is available to detect physical contact, recognize physical attributes of objects such as their softness and texture, and ensure delicate operation while handling the objects. Additionally, tactile sense is relevant to build the body recognition. We focused on vibrotactile sense from the aspects of a wide receptive field, contribution to contact detection and various frequency information involved. A simple electric and cosmetic prosthetic hand with vibrotactile sense was developed by improving Rehand II with polyvinylidene difluoride film sensors for detecting skin-propagated vibrations and soft vibrators for the feedback. The sensors were embedded at the thumb, index finger, and back of the hand of the prosthetic hand. First, recognition tests involving tapped part were conducted. Then, recognition and realistic rating tests involving operations were conducted. Results showed high recognition of tapped parts and operations and the good realistic.