一种人体步态轨迹测量方法

为研究人体的步态运动规律,采用基于拉线传感器检测系统和人体关节角度测量装置,对人在不同路况下行走时踝关节运动轨迹和下肢关节角度进行了测量,根据人体下肢刚体模型和数据融合方法对测量结果进行了分析和处理,得到了人在上楼梯、平地行走和下楼梯时的步态轨迹和3种路况下的支撑相;上楼梯时的支撑相最大,平地行走次之,下楼梯最小.测量结果为了解人体运动规律和康复治疗提供了依据.     

蹲起时助力外骨骼驱动及人机耦合作用驱动补偿

针对由于关节驱动特性不明而造成助力外骨骼蹲起不顺畅的问题,为增强人机交互性及助力外骨骼蹲起可靠性,对蹲起时助力外骨骼的关节驱动及人机耦合作用下的关节驱动补偿进行了研究.通过人体数据采集实验及非线性数据拟合,得到各关节运动学方程.建立了蹲起时的人机耦合动力学模型,研究了关节驱动特征,发现膝关节的驱动特征及其波动性远大于踝关节和髋关节;膝关节驱动力矩与角加速度耦合性强;只在蹲起前半段,系统重心迁移对膝关节驱动有较大影响.根据关节驱动特征的研究结果,膝关节采用双作用线性液压缸进行驱动,与此同时人机耦合作用力可以补偿踝关节部分驱动力矩及髋关节全部驱动力矩.     

基于物理疗法轮椅式下肢康复训练系统设计

针对目前下肢康复训练设备适配性差和康复训练效果不佳的现状,并结合居家日常康复的使用要求,提出一种基于传统物理康复训练关节运动轨迹的轮椅式下肢康复训练机构。详细分析了物理疗法中下肢髋-膝关节康复训练运动规律和特点,并对一个周期内不同治疗阶段进行了系统化分析;利用该规律对可实现关节运动特征的机构构型进行尺寸综合与分析,并基于该构型研制一款轮椅式下肢康复训练系统。该款下肢康复训练系统可以实现髋关节训练运动角度为:91.37°～126.51°,膝关节训练运动角度为:89.11°～135.35°。基于该构型的实验样机可以实现物理疗法所规划的运动轨迹,实际可以实现髋关节运动角度为91°～128°,膝关节运动角度为:90°～131°。该下肢康复训练系统可以模拟康复治疗的师物理治疗时的操作手法,辅助患者进行下肢康复训练,为患者提供稳定可靠的物理治疗,具有积极的社会意义和临床价值。     

考虑跖趾关节运动的踏板式步行康复机器人运动规划

基于人正常步行时足部的运动特征,提出了一种利用机械约束即能实现步行时踝关节和跖趾关节运动姿态模拟的踏板式步行康复机器人,帮助老年人及偏瘫患者进行步行康复训练.通过分析步行时跖趾关节的背屈过程,对前踏板的运动姿态进行规划,并以此确定了约束导轨的轨迹.按照人正常平地步行过程对步行训练时双侧踏板的运动时序进行了规划,并根据步行时的时相分布关系规划了双侧曲柄的转速.利用MATLAB软件建立步行康复机器人的运动学仿真模型,验证了运动规划的可行性,说明该步行康复机器人可以模拟正常人步行时的步态及踝关节和跖趾关节的运动姿态,能够满足步行康复训练的要求.     

双足机器人动态步态规划

针对目前仿人机器人动态步行在样机上实现较少的情况,将多项式插值方法运用于机器人踝关节轨迹规划,结合已知髋关节运动轨迹,利用几何约束的方法求取膝关节运动轨迹,得到完整步态周期内各关节运动规律,最终实现NAO机器人的动态步行。实验结果证实了基于多项式插值的几何约束规划方法是可行且有效的。     

两足步行机器人步态轨迹优化设计的可行方法

步态规划是预先设计出整个步行过程中各关节运动的时间函数,这样一组时间函数的优化设计,求解十分困难。在此我们将其转化为参数优化问题。即给出机器人机构某一特殊点在步行过程中的移动轨迹,以此来描述整个步行运动。然后将该点运动过程离散化,找出每一时刻各关节对应的角度,使其满足一定的限制条件,并达到某一指标条件下的最优。     

基于ADAMS的人体膝关节运动力学研究

在对人体结构进行研究的基础上,分析膝关节的运动学和动力学特性.应用人体生物力学软件LifeMOD创建人体模型,创新性地对膝关节施以轴套力约束,并在ADAMS中进行动力学仿真分析,得到人体膝关节的作用力和作用力矩曲线,验证膝关节轴套力模型的准确性和实用性,为双足步行机器人、人工假肢和康复训练机器人的研究提供理论基础.     

局部阴影下光伏阵列呈多波峰特性的MPPT算法研究

带有旁路二极管的光伏组件在局部阴影的遮蔽下,其输出的P-U特性是由多个局部峰值构成的非线性曲线,使传统的单峰MPPT算法无法准确跟踪最大功率点。通过建立并分析局部阴影下光伏组件的数学模型可避免陷入局部峰值。在传统电导增量法寻找峰值的基础上,应用聚拢峰值扫描判别法,分别从短路电流和开路电压处向中间聚拢扫描峰值并比较大小,直到找出真正的最大功率点。仿真结果表明,该算法在局部阴影下不会陷于局部峰值,能够快速跟踪最大功率点,明显提高了系统的光电转换效率。     

考虑载体运动下光伏组件输出特性研究

为了获取载体运动状态下光伏组件输出特性,利用光伏电池单体五参数模型及光照强度之间耦合关系,并通过建立光伏组件运动姿态信息与光照入射角耦合关系,构建了运动载体下光伏组件输出特性模型。最后,在Matlab/Simulink仿真平台中搭建了仿真实验系统验证了方法的有效性。结果表明,载体的运动姿态会明显影响光伏组件的电压电流特性,且在输入姿态角变化为振幅为0.34、周期为1s的正弦波时,光伏组件最大功率点波动了11.86%。     

下肢外骨骼液压控制系统仿真与性能试验

研究下肢外骨骼携行助力系统控制问题,利用液压阀控制机理,建立了液压位置控制回路,用PID与超前校正网络相结合的方法进行频域设计,通过对液压控制系统性能试验,对不同负载和不同油源压力以及不同运动模式下液压缸流量和压力进行仿真。仿真结果表明,组合控制方法能够对人正常行走时,膝关节角位移可满足人机协调运动要求。试验结果表明,下肢外骨骼携行助力系统采用阀控液压控制能够满足负载30kg低速平地行走、上下楼梯等动作要求。     

Ramps or stairs: the choice using physiological and biomechanic criteria

A study using eight subjects compared the O₂ consumption, heart rate and maximum knee joint angles when climbing stairs or ramps ranging in slope from 10° to 30°. It was found that the physiological cost of stairs is always less than a ramp of equal slope and that stairs with a 6 in riser were usually better than those with a 4 in riser. The values of the flexion at the knee joint were compared with a theoretical analysis by Shinno and found to differ considerably.     

Design of a quadruped walking vehicle for dynamic walking and stair climbing

This paper discusses the design of a quadruped walking vehicle for walking dynamically at high speed and climbing ordinary stairs (30-40°). To realize these requests, new mechanisms are introduced, which are (1) a prismatic joint leg that does not interfere with the steps of a staircase and which performs a cylindrical coordinate motion with good energy efficiency, (2) an articulated body structure having a node that copes with a steep staircase, (3) a dual mode transmission system which can swing a leg with high speed and can generate a large supporting force, and (4) a non-linear type foot force sensor having a wide dynamic range. The effectiveness of these considerations is verified by walking experiments using the trial-manufactured TITAN VI.     

利用多源信息和极限学习机的人体运动意图识别

快速准确的步态识别是实现智能假肢灵活控制的基础与前提,步态(平地行走、上下楼梯和上下坡)的有效识别是关键.为了克服由单一信息源无法辨识复杂多步态的难题,搭建人体步态多源运动信息系统获取髋关节角度信号、加速度信号和足底压力信号,利用足底压力信号将人体步态划分为4个片段,并根据人体步态的特点确定了4个片段下髋关节角度、髋关节加速度信号的特征值,采用核主成分分析(KPCA)对原始特征的组合进行融合,得到信息互补的特征值,最后利用极限学习机(ELM)进行识别,实验结果表明该方法对平地行走、上楼、下楼、上坡、下坡5种步态的平均识别率达到96.78％,平均识别时间0.52 s,明显高于BP、支持向量机(SVM)等方法.     

Effect of seat thickness on peak femoral vein velocity

IntroductionThis study aimed to investigate the effects of different seat thicknesses on lower limb momentum and lower limb blood flow in a narrow enclosed space simulating public places.MethodsWe enrolled 15 female volunteers. We measured the maximum venous blood flow velocity (peak velocity [PV]) of the superficial femoral vein, the range of knee joint movements, and the number of knee joint movements while the subjects sat on the thicker- or thinner-tip seat for 140 min.ResultsThere was a difference in the change rate of PV after 140 min of sitting: thinner-tip seat groups: 22.3% (−31.1 − −13.5%); thinner-tip seat groups: 6.9% (−16.5 − 2.8%) (P < 0.001). There was a significant difference in the range of knee joint motion between the two seats: thicker-tip seat: 24.5° (19.9°–29.1°); thinner-tip seat: 36.6° (29.1°–44.1°) (P = 0.01). There was a significant positive correlation between the change rates of PV and the knee joint range of motion (r = 0.41, P = 0.03).ConclusionsOur findings suggest that a seat structure that does not restrict lower limb movement may help inhibit reductions in lower limb blood flow when sitting for long periods.     

Development of an underactuated exoskeleton for effective walking and load-carrying assist

This study proposed and developed an underactuated exoskeleton to support external load-carrying and partial assist for leg motion with level walking and ascending of slopes and stairs, which require positive energy generation. A strategy for active and passive joint combination are implemented on the underactuated exoskeleton, along with a quasi-passive mechanism to assist with vertical weight support and gait propulsion while minimizing hindrance to the wearer’s free motion. Further, muscle circumference sensors are directly matched with the active joint system, and insole sensors are applied to efficiently detect the wearer’s motion intension. Through experiments with the developed exoskeleton system, the considered performances were verified by analyzing the electromyography data from the rectus fremoris and gastrocnemius muscles while walking and ascending stairs. The developed underactuated exoskeleton can assist healthy people’s load-carrying and facilitate efficient ascension by utilizing the structural body weight support, leg swing, and lifting motion assist through motorized knee joints only. This kind of active joint minimization approach could be particularly helpful in field applications that require independent power sources such as batteries.     

Gait modification and optimization using neural network–genetic algorithm approach: Application to knee rehabilitation

Gait modification strategies play an important role in the overall success of total knee arthroplasty. There are a number of studies based on multi-body dynamic (MBD) analysis that have minimized knee adduction moment to offload knee joint. Reducing the knee adduction moment, without consideration of the actual contact pressure, has its own limitations. Moreover, MBD-based framework that mainly relies on iterative trial-and-error analysis, is fairly time consuming. This study embedded a time-delay neural network (TDNN) in a genetic algorithm (GA) as a cost effective computational framework to minimize contact pressure. Multi-body dynamic and finite element analyses were performed to calculate gait kinematics/kinetics and the resultant contact pressure for a number of experimental gait trials. A TDNN was trained to learn the nonlinear relation between gait parameters (inputs) and contact pressures (output). The trained network was then served as a real-time cost function in a GA-based global optimization to calculate contact pressure associated with each potential gait pattern. Two optimization problems were solved: first, knee flexion angle was bounded within the normal patterns and second, knee flexion angle was allowed to be increased beyond the normal walking. Designed gait patterns were evaluated through multi-body dynamic and finite element analyses.The TDNN-GA resulted in realistic gait patterns, compared to literature, which could effectively reduce contact pressure at the medial tibiofemoral knee joint. The first optimized gait pattern reduced the knee contact pressure by up to 21% through modifying the adjacent joint kinematics whilst knee flexion was preserved within normal walking. The second optimized gait pattern achieved a more effective pressure reduction (25%) through a slight increase in the knee flexion at the cost of considerable increase in the ankle joint forces. The proposed approach is a cost-effective computational technique that can be used to design a variety of rehabilitation strategies for different joint replacement with multiple objectives.     

Peak activation of lower limb musculature during high flexion kneeling and transitional movements

Few studies have measured lower limb muscle activation during high knee flexion or investigated the effects of occupational safety footwear. Therefore, our understanding of injury and disease mechanisms, such as knee osteoarthritis, is limited for these high-risk postures. Peak activation was assessed in eight bilateral lower limb muscles for twelve male participants, while shod or barefoot. Transitions between standing and kneeling had peak quadriceps and tibialis anterior (TA) activations above 50% MVC. Static kneeling and simulated tasks performed when kneeling had peak TA activity above 15% MVC but below 10% MVC for remaining muscles. In three cases, peak muscle activity was significantly higher (mean 8.9% MVC) when shod. However, net compressive knee joint forces may not be significantly increased when shod. EMG should be used as a modelling input when estimating joint contact forces for these postures, considering the activation levels in the hamstrings and quadriceps muscles during transitions.

Practitioner Summary: Kneeling transitional movements are used in activities of daily living and work but are linked to increased knee osteoarthritis risk. We found peak EMG activity of some lower limb muscles to be over 70% MVC during transitions and minimal influence of wearing safety footwear.     

Toward lower limbs movement restoration with input-output feedback linearization and model predictive control through functional electrical stimulation

Functional electrical stimulation (FES) is used to excite paralyzed muscles that are no longer controlled by patients with spinal cord injuries (SCI). Appropriate stimulation patterns are chosen to stimulate intact muscles, in order to extend their overall performance, postponing thus the muscular fatigue during the daily activities such as standing, standing up, sitting down and walking. This paper presents the modeling and the control of a knee joint actuated by the quadriceps muscles. Appropriate stimulation patterns are computed as a function of the desired lower-limb knee joint movements. Parameters of the biomechanical model are identified based on experimental kinematic data. Model predictive control (MPC) is applied to the input-output feedback linearized (IOFL) system. IOFL allows linearization by inverting the system dynamics through a nonlinear feedback transformation. The described control approach is validated through different simulation scenarios for knee flexion-extension. Internal dynamics stability is mathematically proved and performances are compared to those produced by classical pole placements method. The controller has shown satisfactory results in terms of regulation, stability and robustness with respect to external disturbances.     

On-site observations of physical work demands of train conductors and service electricians in the Netherlands

The objective of the present study was to assess the exposure to physical work demands of train conductors and service electricians at a railway company in the Netherlands. On-site observations were performed using the Task Recording and Analysis on Computer observation system to identify the mean duration and frequency of tasks, activities and body postures. In total, 36 train conductors and 41 service electricians were observed for a net working day of 7 h. Results showed that train conductors and service electricians climbed a flight of stairs on average 249 and 258 times, respectively, and that service electricians worked above shoulder height for 65 min on average. In both jobs, guidelines were exceeded, e.g. duration of standing, the number of times climbing a flight of stairs, kneeling and squatting or working in awkward postures, which are risk factors for developing musculoskeletal complaints. Suggestions are made concerning how to reduce these risk factors.

Statement of Relevance: Understanding physical work demands is essential for recognising risk factors for musculoskeletal disorders. Since train conductors and service electricians in the Netherlands reported work-related complaints, on-site observations were performed to determine the duration and frequency of physical work demands. Risk factors were identified in both professions, providing insights concerning preventative measures.     

The effects of a simulated occupational kneeling exposure on squat mechanics and knee joint load during gait

Occupational kneeling is associated with an increased risk for tibiofemoral knee osteoarthritis. Forces on the knee in the kneeling posture, as well as the greater incidence of meniscus tears among workers, likely contribute to the increased risk. We hypothesise that an additional mechanism may contribute – altered neuromuscular control due to prolonged high knee flexion. Forty participants (20 male, 20 female) completed an evaluation of gait and squatting before, immediately following, and 30 min following a 30 min simulated occupational kneeling exposure. An increase in the peak external knee adduction moment and a delay in vastus medialis activation onset during walking were observed post-kneeling, as well as increased frontal plane knee motion during squatting. This was the first investigation to find changes in high flexion transitions as a result of kneeling. Greater frontal plane knee motion may increase the risk for meniscal tears, and subsequently, knee osteoarthritis.

Practitioner Summary: A 30 min simulated occupational kneeling exposure resulted in small but significant gait changes. The greatest effect was on frontal plane knee movement during squatting, which is especially relevant to occupations requiring frequent kneeling/squatting. This increased motion may indicate an increased risk of injury, which supports a link to knee osteoarthritis.