An EMG Controlled Prosthetic Forearm with Three Degrees of Freedom Using Ultrasonic Motors

We developed an EMG controlled prosthetic forearm with three degrees of freedom actuated by small size ultrasonic motors. Its weight is less than 700g and the size is the same as the adult's forearm. The conventional proosthetic arm using DC motors produces a motion noise. So the reduction of the motion noise was one of the big problems to be soleved. Since our prosthetic forearm uses ultrasonic motors, it produces no motion noise. In addtion, the amputee can control six kinds of motions i.e. pronation and supnation of the forearm, flection and extension of the wrist, and grasping and hand-opening. The interface between the amputee and the prosthetic forearm was designed on the basis of the fact that the amputee still preserves the phantom limb motor map after amputation. It can discriminate the amputee's intended motion among six kinds of motions using the EMG signals from the remained muscles and also produce the command signals to control the prosthetic arm. Consequently, the amputee is able to manipulate the prosthetic arm as he intends and his control load is relieved sharply.