Development of an internally powered functional prosthetic hand with a voluntary closing system and thumb flexion and radial abduction-based on normal human grasping action

The purpose of the paper was to introduce an internally powered functional prosthetic hand with a voluntary closing function, which was developed by using robot manipulator technology. From electromyographic and three dimensional analyses of human grasping movements, we found that, if the wrist joint is fixed and the thumb moves in a diagonal direction, the compensation of lifting the shoulder and elbow joints decreases. The experimental results demonstrate that the thumb movements of flexion and radial abduction play an important kinematic role in human grasping movements. Machinery for an internally powered functional prosthetic hand that can drive four fingers with two joints by a single cable is proposed. Tendon transmission in the machinery is useful for the hand to drive the finger joints. We suggest the following results; (1) the hand we developed has passive compliance, (2) and can grasp objects with a cross section of different diameters.