崇群 段
上海理工大学 医疗器械与食品学院(上海 200093),
School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, P.R.China
新伟 李
上海理工大学 医疗器械与食品学院(上海 200093),
School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, P.R.China
秉泽 何
上海理工大学 医疗器械与食品学院(上海 200093),
School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, P.R.China
志鹏 邓
上海理工大学 医疗器械与食品学院(上海 200093),
School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, P.R.China
洪流 喻
上海理工大学 医疗器械与食品学院(上海 200093),
School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, P.R.China
上海康复器械工程技术研究中心(上海 200093),
Shanghai Engineering Research Center of Assistive Device, Shanghai 200093, P.R.China
民政部神经功能信息与康复工程重点实验室(上海 200093),
Key Laboratory of Neural-functional Information and Rehabilitation Engineering of the Ministry of Civil Affairs, Shanghai 200093, P.R.China
上海理工大学 医疗器械与食品学院(上海 200093),
School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, P.R.China
上海康复器械工程技术研究中心(上海 200093),
Shanghai Engineering Research Center of Assistive Device, Shanghai 200093, P.R.China
民政部神经功能信息与康复工程重点实验室(上海 200093),
Key Laboratory of Neural-functional Information and Rehabilitation Engineering of the Ministry of Civil Affairs, Shanghai 200093, P.R.China
Corresponding author.
喻洪流,Email:
moc.liamtoh@89lhy
式中
BC
=
σ
1
NJ
,
CD
=
σ
2
CN
。该部分的优化目标是使最大积分尺寸
S
小于或等于接受腔
(矢状面宽度)的一半。根据 RCM 机构尺寸要求和不动点位置,优化函数受以下约束条件约束:
本文利用 MATLAB GA 工具箱进行优化,
列出了优化中使用的参数。
表 2
Parameters of genetic algorithm
遗传算法的参数
遗传算法的参数
|
数值
|
Population size
|
311
|
Nr
of Elite
|
3
|
Nr
of Near Searches
pr
Elite
|
4
|
Mutation Rate
|
0.5
|
Mutation Gain
|
0.1
|
Evolution Iterations
|
200
|
2. 模型和仿真
2.1. 整体方案
下肢假肢由髋离断假肢、膝关节假肢和足部假肢组成。本文中髋离断假肢的设计是在理想化膝关节假肢和足部假肢基础上开展的,主要由 RCM 机构、并联驱动器、站立支撑板、扭矩传感器等组成,其转动范围是 −17° 旋转到 95°,包括从 −15° 到 75° 的摆动相位和 90° 的坐姿状态,
是以式(1)收敛到最小值为目标,经过 200 次迭代优化得到的详细设计参数。控制方面:首先通过 VICON 设备采集健康人体下肢步态运动学信息并通过多层前馈网络(back propagation neural network,BP 神经网络)建立穿戴髋关节假肢患者健康侧和假肢侧的运动学映射关系;使用九轴姿态传感器采集人体健康侧下肢关节运动学参数(角速度、角加速度等)并进行数据预处理提取步态特征,之后由 BP 神经网络建立健康侧-假肢侧的运动学映射关系生成假肢侧运动的参考步态相位,结合建立的下肢假肢动力学模型通过比例积分微分控制(proportional integral derivative control,PID 控制)调节两个直线驱动器运动。据研究表明,髋关节运动中的最大力矩值产生在单腿支撑期,此时下肢各关节的高刚度特性实现对人体的支撑,在髋关节屈曲伸展阶段,关节力矩在
25 Nm 之间。针对此分析,再结合截肢者偏弱的运动能力等情况,在利用支撑板等结构保证支撑性要求的基础上,选用 M3508 无刷电机,配合滚珠丝杠和 2 mm 线径弹簧为关节提供力矩,重量大约在 1 200 g,总功率在 100 W 左右。
为设计方案的三维模型图。
表 3
Design results based on genetic algorithm optimization
基于遗传算法优化的设计结果
假肢参数
|
数值
|
|
311 mm
|
|
0.1 mm
|
|
200 mm
|
2.2. 髋离断假肢运动仿真分析
使用 SolidWorks 软件建立简化的髋离断假肢样机模型,将模型保存为 Parasolid 格式的文件并导入 ADAMS 软件中,对模型的各个零件自定义材料属性;添加固定副、转动副等约束,把原本与接受腔固定的零件与大地固定,在驱动连杆作用的转动副位置添加驱动使得虚拟样机满足所需的运动方式。简化髋离断假肢模型如
所示。仿真首先进行驱动设置,使其按照预设的轨迹方式运动
[
17
]
。由于假肢控制原理是镜像健康侧下肢的运动参数,控制目标是实现假肢关节运动与截肢者健康侧关节运动变化的最大程度对称,故依据前述实验所得的人体行走运动中的髋关节力矩变化曲线作为虚拟样机输入 STEP 函数驱动的依据,如
所示,然后把虚拟样机关节运动副上的 Motion 函数改成 STEP 函数,
为函数参数,最后完成虚拟样机运动仿真。
表 4
STEP function value
STEP 函数表
序号
|
参数
|
1
|
Step(time,0,0,3.6,0.43)
|
2
|
Step(time,3.6,0,15.8,0.12)
|
3
|
Step(time,15.8,0,27.7,−0.04)
|
4
|
Step(time,27.7,0,42.7,−0.37)
|
5
|
Step(time,42.7,0,48.7,−0.38)
|
6
|
Step(time,48.7,0,62.7,−0.18)
|
7
|
Step(time,62.7,0,74.7,−0.03)
|
8
|
Step(time,74.7,0,86.4,0.21)
|
9
|
Step(time,86.4,0,100,0.30)
|
3. 结果和讨论
在 ADAMS 中设置仿真时间及仿真步长进行仿真,进入 ADAMS/Postprocessor 模块,仿真完成后得到一个步态周期内髋关节角度变化数据,经 MATLAB 处理得到仿真输出和健康下肢的髋关节角度-力矩变化曲线和不同速度下的髋关节角度变化曲线,见
。
4. 结论
针对传统髋离断假肢两大问题:转动中心与健康侧髋关节大转子位置不对称,从而导致穿戴者行走步态畸形,以及纯机械被动式设计消耗能量较大,本文设计了一种基于 RCM 机构的动力髋离断假肢。利用遗传算法优化整体结构尺寸,配合设计了仿生并联弹性驱动器为假肢提供助力,在建立的 SolidWorks、ADAMS 虚拟样机联合仿真,初步验证了该设计的可行性。结果显示,与传统假肢相比,所设计的基于 RCM 的假肢能够提高行走步态的对称性,对于改善穿戴者行走步态具有积极作用。
致谢:我们诚挚地感激河南孙有志、上海云耀蛟和上海假肢厂有限公司吕永兵,在研究中孙有志先生和云耀蛟先生让我们了解到髋离断截肢者的行走习惯和假肢穿戴反馈等,吕永兵总经理在假肢的结构设计和对线等调整方面提供了宝贵的建议。
利益冲突声明:本文全体作者均声明不存在利益冲突。
Funding Statement
国家自然科学基金(61473193)
Funding Statement
The National Natural Science Foundation of China
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Articles from
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi = Journal of Biomedical Engineering
are provided here courtesy of
West China Hospital of Sichuan University