Development of Biomimetic Prosthetic Hand

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The purpose of this study was to develop a biomimetic prosthetic hand controlled by electromyogram. This hand mimicked dynamic properties of human neuromuscular control system and had a supplementary sensory feedback system.We developed a portable control system of the biomimetic hand. This system consisted of processing units of EMG signals, a digital servo system of DC motor and two sets of battery. A new type of flexible glove for the biomimetic hand was developed. This rubber glove was made of highly deproteinized natural rubber with low deformation resistance and did not disturb a motion of the prosthetic hand to a large extent.We developed two types of supplementary sensory feedback systems, which transmitted information of the force applied to the finger of the prosthesis to its user with vibotactile stimuli. In one system, optimum frequency (250Hz) of vibration was utilized. At this frequency, the amplitude of stimuli that the user could sense was smallest. Other system utilized infrasonic vibrotactile stimuli. Utility of these systems were shown by the experiment where a normal subject was grasping soft objects with the prosthetic hand.We developed a simulator of myoelectric hand with which amputees could try to operate the myoelectric hand and to decide appropriate parameters of the control system. In this simulator, the motion of the prosthetic hand and posture of user's upper extremity were displayd with real-time 3D computer graphics. Myoelectric control experiments showed that the user was able to control finger-angles of prosthetic hand and to grasp the object virtually with this simulator.