Development of biomimetic prosthetic hand controlled by electromyogram

The purpose of this study was to develop a new type of myoelectrically-controlled biomimetic prosthetic hand (biomimetic Kobe Hand) which had almost the same dynamics as those of the neuromuscular control system of finger muscles, in particular, including mechanical properties of the muscle and of the stretch reflex. One of the characteristic features of the neuromuscular control system in man was a decrease in the compliance around the joint with increasing activities of the muscle. The Kobe hand consisted of a processing unit of surface EMG signals, a digital servo system of DC motor and a mechanical hand of one-degree-of-freedom with three fingers. Those nonlinear properties of the neuromuscular control system were realized by using a position control system of the finger movement, force feedback and variable gain which was modulated by amplitude of IEMGs (rectified and smoothed electromyograms). EMG signals picked up from a pair of antagonistic muscles of the forearm were used as control signals. Usefulness of the biomimetic Kobe hand was showed by executing myoelectric control experiments with both healthy and amputated subjects.