Rehand II: Wire-Driven Five-Fingered Electric Prosthetic Hand Utilizing Elasticity of a Cosmetic Glove.

Five-fingered electric prosthetic hands have been commercialized to assist the activities of forearm amputees in their daily life. Since the five-fingered electric prosthetic hands use a complicated mechanism and several actuators, the total weight is 1 kg or more. Although some hands are covered with a dedicated silicon glove, the appearance of them is not realistic compared to a general cosmetic hand. In this paper, we report a wire-driven five-fingered electric prosthetic hand utilizing elasticity of a cosmetic glove termed as Rehand II. The five fingers are flexed by pulling wires with a single servo motor and are extended by the elasticity of the cosmetic glove. In addition, a fitting mechanism in the hand allows the hand to fit the shape of various objects. With this approach, we developed an electric prosthetic hand with a simple grasping function that solves appearance and weight problems in conventional hands. The total weight of the developed hand was 562 g. The results of evaluation tests via Southampton Hand Assessment Procedure (SHAP) and grasping test of daily necessities in which a forearm amputee participated demonstrated that the developed prosthesis exhibited function to manipulate various objects used in daily activities.