动力大腿假肢楼梯步态规划与控制

GAIT PLANNING AND CONTROL OF STAIR WALKING WITH A POWERED TRANSFEMORAL PROSTHESIS

肖文涛

11849013

硕士

机械工程领域工程

付成龙

2020-06-03

2020-07-20

哈尔滨工业大学

深圳

动力大腿假肢可以弥补传统被动假肢因膝、踝关节缺少动力元件，而无法帮助大腿截肢者在上楼过程中完成身体抬升，以及在下楼过程中的提供稳定支撑的问题。但现有动力假肢楼梯步态控制策略还停留在较底的关节层面，即通过模仿人体关节的力矩输出特性，从而达到助力的效果，并未从整体的角度考虑动力假肢和残肢对人体的综合作用。针对以上问题，本文结合足式机器人控制技术，提出一种基于虚拟模型的步态控制方法，从下肢整体的角度出发，用以帮助截肢者获得更好的楼梯行走体验。论文的主要工作和成果有：（1）以压力中心和质心为基点，构建了人体下肢虚拟模型。根据健康人楼梯行走实验中所采集的下肢生物力学信息，分析了人体上下楼过程中支撑期的质心功率、虚拟腿沿腿力FN、摆动角度α以及足部水平夹角θf等数据的变化规律，为动力假肢楼梯虚拟模型控制器的设计提供了生物力学基础。（2）结合第一代动力假肢的缺陷以及集成化等新的需求，设计了第二代动力大腿假肢，为楼梯虚拟模型控制器的实施提供了稳定的平台。放弃踝关节基于串联弹性驱动器的设计方案，改用高功率密度力矩电机加小减速比减速器的搭配，降低了控制难度，增大了响应带宽。为增加信号稳定性和丰富度，足底压力改用六维力传感器进行采集，不再使用电阻式应变片。处理器采用意法半导体生产的STM32F427IIH6，弃用NI Compact RIO 9093模块，从而减小了控制系统的体积，实现了第二代假肢硬件平台的集成。（3）根据健康人楼梯行走实验中所获的下肢生物力学数据，设计了基于有限状态机的楼梯虚拟模型控制器。通过确定压力中心和质心的替代点，将虚拟模型应用于假肢侧，并设计虚拟腿阻抗控制器用于调节虚拟腿力的输出。根据沿腿力与腿长关系FN-LN曲线的斜率大小，即虚拟腿的刚度，进行楼梯步态支撑期的相位划分，并对各段曲线进行线性拟合，得到简化的FN-LN曲线。然后利用摆动角与步态周期之间良好的线性关系将其作为控制假肢相位切换的参考量，最终完成楼梯虚拟模型控制器的有限状态机设计。 （4）通过设计动力假肢、被动假肢和健康人的楼梯行走对比实验，测试了楼梯虚拟模型控制器的助力效果。根据实验采集的人体下肢运动学、动力学数据，分析了动力假肢对于步态对称性的影响，以及虚拟模型控制器对沿腿力FN的调节结果，初步证明了控制器的有效性。

Powered transfemoral prosthesis have more advantages than passive prosthesis when stair walking. Due to lack of energy input, passive prosthesis can not help the transfemoral amputees to lift the body during stairs ascent, and provide stable support during stairs descent. But, the current stair gait control strategy of powered prosthesis still stays at the joint level, that is, to achieve the effect of assistance by imitating the torque output characteristics of human joints, without considering the comprehensive effect of powered prosthesis and residual limb on human body from the overall perspective. In order to solve the above problems, this paper proposes a control method based on virtual model, which can help amputees get better stair walking experience from the perspective of the whole lower limbs. The main work and achievements of this paper are as follows:(1) A virtual model of human lower limbs was constructed based on the center of pressure and the center of mass. According to the biomechanical data of the lower limbs collected in the stair walking experiment of the healthy people, this paper analyzes the data change rules of the center of mass power, the stiffness characteristics of the virtual leg, the swing angle α, the horizontal angle θ of the foot during the support period of the human body going up and down the stairs, which provides the biomechanical basis for the design of the virtual model controller of the powered prosthesis stair.(2) The second generation of powered transfemoral prosthesis is designed, which provides a stable platform for the implementation of virtual model controller of stairs. This prosthesis combined the defects of the first generation of powered prosthesis and the needs of integration. Instead of the design of ankle joint based on SEA, the high power density torque motor with small reduction ratio reducer is used to reduce the control difficulty and increase the response bandwidth. In order to increase the stability and richness of the signal, the foot pressure is collected by six dimensional force sensor instead of the resistance strain gauge. The integration of the second generation of prosthetic hardware platform is realized by suing the embedded system based on STM32F427IIH6 framework instead of NI Compact RIO 9093 unit.(3) A virtual model controller of stair based on finite state machine is designed according to the biomechanical data of lower limbs obtained in the stair walking experiment of healthy people. The virtual model is applied to the prosthetic side by determining the substitution points of pressure center and mass center, and the virtual leg impedance controller is designed to adjust the output of virtual leg force. According to the slope of FN-LN curve along the relationship between leg force and leg length, i.e. the stiffness of virtual leg, the phase division of stair gait support period is carried out, and the linear fitting of each curve is carried out to obtain the simplified FN-LN curve. Then, using the good linear relationship between the swing angle and the gait period as the reference to control the phase switching of the prosthesis, the finite state machine design of the virtual model controller of stairs is completed.(4) A stair walking experiment is designed to test the effect of stair virtual model controller compare with the passive prosthesis and healthy people. According to the kinematic and dynamic data of the human lower limbs collected from the experiment, the influence of the dynamic prosthesis on the gait symmetry and the adjustment result of the force FN are analyzed. The effectiveness of the controller is preliminarily proved.

动力假肢 楼梯 虚拟模型 步态规划 腿部刚度

powered prosthesis stairs virtual model gait planning leg stiffness

中文

联合培养

南方科技大学

肖文涛. 动力大腿假肢楼梯步态规划与控制[D]. 深圳. 哈尔滨工业大学,2020.