基于迭代学习控制智能下肢假肢研制:实现了对健肢步速的跟随

Development of intelligent lower limb prostheses based on iterative learning control:A follow of normal walking speed

背景:传统下肢假肢通过手动方式将气压或者液压膝关节阻尼器调整到一种比较适宜的状态,行走状态改变时膝关节阻尼不能随之改变,假肢跟随性差,步速变化范围小。智能下肢假肢能够根据人体运动信息调整膝关节阻尼力,从而达到更加接近正常步态的效果。开发国内智能下肢假肢对提高国内残疾人生活质量有着重要的现实意义。目的:研制能够实现步速跟随功能的智能下肢假肢。方法:智能下肢假肢机械部分采用带固定式气缸阻尼器的四连杆机构,由四连杆后臂下轴的转动角度得出步行速度,依照迭代学习算法得出的知识库确定该步行速度下的针阀开度,通过永磁式直线步进电机作为执行器驱动针阀来控制缓冲气缸腔室间气道有效截面积来调整假肢摆动速度。结果与结论:实验结果显示,采用电位计作为检测手段不但能够获得步行速度,而且能够区分支撑期和摆动期。在不同速度下,智能下肢假肢膝关节最大摆动角度变化小于13°。提示智能下肢假肢能够识别步行速度,并根据步行速度调整膝关节摆动速度,实现了对健肢步行速度的跟随,为进一步的研究奠定了实验基础。

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.