Abstract
For a leg amputee, the first step of rehabilitation is to be fitted with a prosthesis. Present leg pros-theses are too simple to fulfill various demands of a wearer such as changing walking speed, walking up and down stairs, and so on. One of the courses of research undertaken by many laboratories in this field is to make an intelligent prosthesis. The aim of this paper is to describe the development of an intelligent passive above-knee prosthesis that can automatically adapt dynamic parameters to various walking situations. This prosthesis is intended to achieve an optimal knee flexion movement controlled by the suitable valve adjustment of a pneumatic cylinder unit with a microcomputer system. The unit is attached across the artificial knee joint. To provide the basic behavior of the prosthesis with the unit, a mathematical model has been built for the unit and the prosthetic system. In addition, thigh and shank angular displacements of various walking situations of sound gait have been measured. Mathematical calculations were made to determine the suitable valve adjustment to simulate the sound knee flexion movement at various walking speeds and walking downstairs with a pros-thetic gait. It was proved that the dynamic valve opening and closing during the swing phase provides suitable control. Prosthesis evaluation was fabricated. A portable one-board-microcomputer system was employed as a control system and CO_2 gas from a portable gas cylinder was used as a power source of valve movement. These two and gas regulators were backpacked. A miniature electro-magnetic valve and a diaphragm cylinder were attached within a pros-thesis so that an intact computer-controlled pros-thesis was achieved. Two A/K amputees were fitted with this pros-thesis and underwent examination walks. They succeeded in changing speed when walking. It was proved that the valve adjustment should vary according to the wearer. It is also suggested that, the iterative calculation should be done to seek the optimum valve adjustment. The first valve adjustment is calculated with the input of thigh angular displacement of sound gait, but the second and following ones are calculated with the input of that of prosthetic gait. It is expected to be possible to obtain the optimum valve adjustment by repeating this procedure. This paper proposes one of the possibilities for the coming generation of A/K prostheses.
