Ryuhei Okuno

Biomimetic EMG-prosthesis-hand

The purpose of this study is to develop a myoelectric prosthetic hand that simulates fundamental dynamic properties of the neuromuscular control system of human hand. In particular, this prosthetic hand mimics the property that both muscle viscoelasticity and gain of the stretch reflex vary linearly with the activity of muscle. 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 rectified and smoothed EMG signals. The prosthetic 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. Usefulness of the developed prosthetic hand was shown in myoelectric control experiments with an amputated subject. Both the finger-angle and the stiffness of the hand were voluntarily controlled with EMG signals and soft objects were grasped smoothly.

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.

Simulator of a Myoelectrically Controlled Prosthetic Hand with Graphical Display of Upper Limb and Hand Posture

Three types of prosthetic hand are currently available: cosmetic, body-powered, and myoelectric (Laschi et al., 2000). Cosmetic prostheses are passive, and designed to look like the natural hand, with solely an aesthetic purpose. Body-powered prostheses are pow‐ ered and controlled by body movements, generally of the shoulder or of the back. Myoelectric hands are electrically powered and controlled by electromyographic (EMG) signals; i.e., small electric potentials produced by contracting muscles. Myoelectric hands are typically controlled in switched or simple proportional mode, according to the amplitude of the EMG signals (Stein and Walley, 1983; Nader, 1990; Sears and Shaper‐ man, 1991; Bergman et al., 1992; Kyberd and Chappell, 1994). The switched control is the simplest one, as it consists of only two states: on or off. Although much progress has been made in myoelectric hands, their motor functions are still not comparable with those of a natural hand, partly because they have been designed to provide only the most basic functions of a natural hand, such as grasping and holding.

Development of myoelectric hand end effector with voluntarily controlled compliance

The purpose of this study was to develop an end effector of a myoelectric prosthetic hand that simulates fundamental dynamic properties of the neuromuscular control system of the human hand. Both finger angle and compliance of the end effector could be controlled voluntarily by surface EMG signals. This was composed of a one-degree-of-freedom mechanical hand with three fingers, a microprocessor based DC motor position control system and a force feedback unit.