DESIGN METHODOLOGY FOR A MULTIFUNCTIONAL HAND PROSTHESIS

The first part of this paper reviews different approaches to define th e motion of the fingers and the thumb in order to obtain prehension. T he last part presents the design of a hand prosthesis based on a new p lane of action for the thumb and on proposed design specifications and functional characteristics. The design methodology consists of two st eps: the morphology design of the hand prosthesis and the 4-bar mechan ism design for each finger. A 3-D computer-aided design (CAD) interact ive program was used as a design tool to obtain the hand morphology. T his CAD technique was also used to check the geometry, the relative mo tions of the fingers, and the possibility of interference for the prop osed model with two prehension patterns (tridigital and lateral). It i s noted that identical flexion angles of the finger joints were obtain ed for these two prehension patterns, the difference being in the incl ination angle of the thumb's plane of flexion. This finding greatly si mplified the design of the internal mechanisms of the fingers. CAD was a powerful tool in the design process of this hand prosthesis and wil l be more and more useful in the future.