Abstract:

BACKGROUND: Traditional lower limb prosthesis with hydraulic or pneumatic dampers only can be adjusted to a fixed damper. For a changing cadence, the traditional prosthesis with limited operating range cannot follow the sound leg. Intelligent prosthesis can adjust the knee moment to achieve a near-normal gait. Affordable intelligent lower limb prostheses can significantly improve the life quality of native amputees.
OBJECTIVE: To develop a practical lower limb intelligent prosthesis which can follow the walking speed of sound leg.
METHODS: Four-bar linkage with a fixed pneumatic cylinder was adopted as the mechanism of the prosthesis joint. The electronic goniometer measured the prosthesis knee angle to acquire the walking speed. To obtain a displacement of the conical valve corresponding to current speed, a knowledge base was established by ILC (Iterative Learning Control) algorithm. 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: Results indicate that potentiometer employed as local sensor can measure the walking speed, and distinguish stance phase and swing phase. Maximum knee joint angle of prosthesis varies in a limited range within 13 degree at different walking speeds. Intelligent lower limb prosthesis can identify the walking speed and follow the cadence of sound leg, which lays a experimental base for a practical product.