Design and control of electromyogram prosthetic hand with high grasping force

This paper presents the design concept of a novel electromyogram prosthetic hand, which adopts a grasping strategy consisting of thumb opposition with high grasping force and finger extension with non-backdrivability. This grasping strategy contributes to mass saving and high grasping force. Each finger has 1 degree of freedom (DOF) for flexion/extension, and the thumb has 2 DOF for opposition and flexion/extension. The design includes a passive extension mechanism to keep contact with the grasped object and a passive flexion mechanism to avoid collision between the fingers and the environment. The prosthetic hand also has 2 DOF for wrist motion. All motors and control circuitry are installed in the hand frame. The outside aspect and the size are similar to those of a woman´s hand. The hand´s mass including artificial skin is 336 g, and the grasping force is 20 N and above. These specifications have been set based on a survey of electric prosthetic hands administered to users and medical experts. The experimental results of hand control measured by a surface electromyogram from an able-bodied subject are also presented.