Abstract:

BACKGROUND: Traditional lower limp prosthesis only allows single walking speed which cannot change with the gait, so the pace is also fixed single and cannot adapt to different speeds. The adaptability of traditional prosthesis is poor.
OBJECTIVE: To achieve the gait following of the prosthesis by fuzzy control methods.
METHODS: Four-bar linkage with a fixed pneumatic cylinder was adopted as the mechanism of the prosthesis joint. A fuzzy control rule was proposed to control the valve opening base on the changes of the gait cycle. The prosthesis leg swing speed was regulated by a needle valve whose orifice opening was adjusted by a permanent magnet linear step motor.
RESULTS AND CONCLUSION: While the speed was changed, the knee angle of prosthesis also slightly changed. Maximum value did not exceed 80°. Prosthetic gait change was less than 11°. Amputees could adapt to different walking speeds. The gait changes between the two legs were basically the same and the symmetry index was more than 90%. The experiments showed that the gait cycle can control the needle valve to achieve the adjustment of pace. The control method for walking speed adjustment is feasible.