Force-directed design of a voluntary closing hand prosthesis

This paper presents the design of a body-powered voluntary closing prosthet ic hand. It is argued that the movement of the fingers before establishing a grip is much less relevant for good control of the object held than the d istribution of forces once the object has been contacted. Based on this not ion, the configurations of forces on the fingers and the force transmission through the whole mechanism were taken as a point of departure for the des ign, rather than movement characteristics. For a good distribution of pinch ing forces on the object and a natural behavior, the prosthesis is made ada ptive and flexible. To achieve good force feedback, the disturbing influenc es of the cosmetic glove are strongly reduced by a compensation mechanism. To further improve the transmission of forces, friction is reduced by furni shing the whole mechanism with rolling links. This force-directed design ap proach has led to a simple mechanism with low operating force and good feed back of the pinching force.