主动型仿生踝关节假肢的设计

背景：与髋、膝关节假肢设计相对比较成熟的技术相比,踝关节作为人体下肢关节的重要组成部分,也是最为灵活的部分,一直以来研究都比较滞后,相关的假肢踝关节产品未能很好的满足假肢患者的需求。目的：从生物力学、解剖学和生理学角度出发,设计和研制出能在矢状面内做屈伸运动的主动型仿生踝关节假肢装置。方法：根据仿生学原理和人体踝关节在步态行走时的受力特点和生理功能,建立二自由度的主动型仿生踝关节的力学模型,设计假肢踝关节的机械结构与控制系统,其主要部件包括仿生踝关节系统、辅助装置、数据控制系统和数据采集系统。结果与结论：利用研制出的踝关节装置进行系统测试,使用正常人行走时的踝关节角度数据作为输入信号,以步进电机作为动力驱动实现模拟踝关节的运动,通过数据采集系统获得输出的角度数据。测试结果表明仿生踝关节能够跟随输入角度数据运动,实现了仿生踝关节跟随运动的预期目标。     

下肢假肢步态试验机的设计

实验于2008-03在上海理工大学生物力学与康复工程研究所完成。基于仿生学原理,将人体下肢简化为刚体结构,关节简化为单轴结构,设计出一套下肢假肢步态试验装置。整个步态试验机装置系统由模拟腿、动力和传动装置及测控系统组成,主要部件有躯干、大腿、小腿、脚板和髋关节、膝关节、跑步机以及驱动部分。采集健康青年人常速行走的运动步态参数,以其关节角度数据作为输入信号,以步进电机作为动力驱动实现模拟腿的运动,达到正常人行走步态的模拟。结果显示,对模拟后的输出信号进行采集并与输入信号相比,最大相对误差为5.6%,在工程误差允许范围之内。提示下肢假肢步态试验机能基本模拟人的正常步态。     

肌肉再分布技术在智能仿生假肢信号识别中的应用

目的 探讨肌肉再分布技术（MRT）在智能仿生假肢信号识别中的应用价值。 方法 于2016年12月至2017年4月期间采用MRT技术治疗4例肢体远端截肢患者,均为男性,其中上肢截肢患者3例,截肢水平分别位于前臂中远1/3处、腕掌关节和腕中关节;下肢截肢患者1例,截肢水平位于小腿中远1/3处。MRT手术是利用残端肢体内的肌肉、肌腱进行移位,将4~6根肌腱锚定在皮肤不同区域,通过肌肉主动收缩牵拉肌腱,使不同区域皮肤发生明显形变。术后观察项目包括皮肤形变、电容信号数据及并发症情况等。在进行电容信号测量时,嘱患者分别执行抓握、屈腕、伸腕、屈指、伸指,或踝背伸与跖屈、伸趾和屈趾动作,利用电容传感测量系统采集患肢形变信息并进行分析。 结果 4例患者均获随访,共有20处部位接受MRT手术。术后3个月时患者均能主动控制相应肌肉收缩并产生皮肤形变,有效形变率为80%（16/20）。电容信号测量结果分别利用线性判别分析（LDA）和二次判别分析（QDA）两种分类器对各种动作进行识别,发现上肢整体识别准确率分别为97.27%和100%,每种动作各自识别准确率均为100%;下肢整体识别准确率分别为95.32%和100%,每种动作各自识别准确率均为100%。术后有1例患者创面不愈,经多次换药后愈合。 结论 MRT能有效将人体运动意图进行输出,增加了运动信号源的数目及强度,有助于患者更好地控制智能仿生假肢,为人机交互提供了新的途径。     

步态分析在假肢设计中的应用

步态分析是现代假肢仿生设计的重要依据和工具,文章结合智能多轴膝关节设计实例,从设计目标、机构设计和控制系统3个层次介绍了步态分析在假肢设计中的应用。     

具有路况识别功能的智能膝上假肢的研究

目的研究智能假肢具有对不同路况适应性的必要性和实现这种功能的关键技术。方法通过人体在不同路况下步行时的步态分析实验数据和所建立的下肢运动的动力学模型 ,得到膝关节力矩函数 ,在自行研制的智能膝上假肢系统中进行实验验证。提出根据大腿肌电信号特征进行路况辨识的智能假肢方法 ,并对上、下坡时部分肌肉肌电信号进行检测。结果在不同路况下 ,膝关节力矩有较大变化 ;上、下坡时部分肌肉肌电信号有明显不同。结论根据肌电信号特征进行路况辨识是可行的 ,所研究的智能假肢系统能实现对小腿运动规律和踝关节运动轨迹的控制 ,达到比较理想的结果。     

一体化假肢与传统假肢生物力学模型的比较

目的：应用有限元方法分析一体化假肢与传统假肢的应力分布特点，探讨一体化假肢的应力缓冲作用。 方法：基于针对同一膝下截肢者设计的一体化假肢和传统假肢的真实几何构形，分别建立三维有限元模型，同时考虑残肢和接受腔之间的接触作用，选用摩擦系数为0．5。施加Heel Off步态时相的载荷，比较分析一体化假肢和传统假肢模型的应力分布。 结果：①一体化假肢和传统假肢模型中，接受腔的应力分布基本一致，各区域的应力值也较为接近。接受腔和假腿的过渡区域都为高应力区；两个模型在此区域的应力值则差异较大，一体化假肢的最大应力分别为16.1MPa和17．8MPa．而传统假肢则达到23．7MPa和28．6MPa，传统假肢的应力分别高于一体化假肢47．2％和60．7％。高应力区的面积也呈现出传统假肢明显大于一体化假肢的现象，传统假肢的高应力区从前端和后端一直延伸到外侧面。②两个模型软组织表面的应力分布规律基本一致，最大正应力和最大剪应力都出现在正面末端。传统假肢模型中残肢表面的最大正应力和最大剪应力分别为581.2kPa和178.7kPa，一体化假肢模型中残肢表面的最大正应力和最大剪应力分别为416.8kPa和118．3kPa。 结论：一体化假肢的外形美观，且价格低廉，轻便，易于截肢者接受。一体化假肢在接受腔和假腿的过渡区域产生较为明显的应力缓冲作用，也降低了残肢表面的应力，生物力学性能明显优于传统假肢，将成为未来假肢发展的一个重要方向。     

下肢假肢的转动惯量测定装置

下肢假肢转动惯量测定装置原理是依据假肢的质心位置，以及假肢和假肢固定架的摆动周期来测定假肢绕任意轴转动的转动惯量。其中，假肢的质心由专门的质心测定装置测得，而转动周期依靠红外测试装置和计时器在随行夹具经若干周期的摆动后测出摆动周期。实验测量得到转动惯量的相对误差为3．8％，小于工程误差允许的5％。证明该装置测量像假肢这样形状复杂物体的转动惯量便捷、准确，精度能满足使用的要求，是一个兼具测试和研发双重功能的实验平台，这对提升假肢设计水平具有一定的指导意义。     

人工智能假肢

智能假肢能够根据外界条件变化和工作要求,自动调整系统参数,比普通假肢具有更好的仿生性和适应性。上肢假肢的智能主要体现在假手抓持物体时对物体形状和力的自适应控制能力;下肢假肢的智能主要体现在膝关节力矩控制和对外界冲击及时反应等能力。     

一体化假肢与传统假肢生物力学模型的比较

目的:应用有限元方法分析一体化假肢与传统假肢的应力分布特点,探讨一体化假肢的应力缓冲作用。方法:基于针对同一膝下截肢者设计的一体化假肢和传统假肢的真实几何构形,分别建立三维有限元模型,同时考虑残肢和接受腔之间的接触作用,选用摩擦系数为0.5。施加HeelOff步态时相的载荷,比较分析一体化假肢和传统假肢模型的应力分布。结果:①一体化假肢和传统假肢模型中,接受腔的应力分布基本一致,各区域的应力值也较为接近。接受腔和假腿的过渡区域都为高应力区;两个模型在此区域的应力值则差异较大,一体化假肢的最大应力分别为16.1MPa和17.8MPa,而传统假肢则达到23.7MPa和28.6MPa,传统假肢的应力分别高于一体化假肢47.2%和60.7%。高应力区的面积也呈现出传统假肢明显大于一体化假肢的现象,传统假肢的高应力区从前端和后端一直延伸到外侧面。②两个模型软组织表面的应力分布规律基本一致,最大正应力和最大剪应力都出现在正面末端。传统假肢模型中残肢表面的最大正应力和最大剪应力分别为581.2kPa和178.7kPa,一体化假肢模型中残肢表面的最大正应力和最大剪应力分别为416.8kPa和118.3kPa。结论:一体化假肢的外形美观,且价格低廉,轻便,易于截肢者接受。一体化假肢在接受腔和假腿的过渡区域产生较为明显的应力缓冲作用,也降低了残肢表面的应力,生物力学性能明显优于传统假肢,将成为未来假肢发展的一个重要方向。     

基于有限状态机控制的智能假肢踝关节

背景：目前智能假肢只是考虑了膝关节的作用,假肢踝关节只是作为假肢膝关节的辅助工具,无法根据外部环境和步态的变化实现假肢自然的行走。目的：研制出可靠的智能假肢踝关节,有效改善截肢者的步态。方法：在阻尼可变式踝足假肢的基础上,提出了有限状态机的控制方法,对踝足步态进行了详细的划分,在每个步态内制定了相关的控制策略。结果与结论：实验结果表明,基于有限状态机控制的智能假肢踝关节能够有效的跟随健肢侧运动,能够适应不同的步速,为以后膝踝协调运动奠定了一定的实验基础。     

A self-contained, mechanomyography-driven externally powered prosthesis

The measurement of the low-frequency (5-50 Hz) "sounds" or vibrations produced by contracting muscles is termed mechanomyography (MMG). As a control signal for powered prostheses, MMG offers several advantages over conventional myoelectric control, including, nonspecific sensor placement, distal signal measurement, robustness to changing skin impedance, and reduced sensor costs. The objectives of this study were to demonstrate 2-function prosthesis control based on a triplet of distally recorded, normalized root mean square MMG signals and to identify necessary future research toward full clinical implementation of MMG signals in upper-limb externally powered prostheses. A novel self-contained MMG-driven prosthesis for below-elbow amputees was designed, implemented, and preliminarily tested on 2 subjects. This prosthesis was composed of specialized software and hardware modules that emulate a 2-site electromyography sensing system. Although the use of MMG signals for prosthesis control has been shown previously, we report, for the first time, successful control within a self-contained unit in unconstrained environments. Specifically, essential requirements for practical use, such as standardized sensor attachment, basic noise elimination, and miniaturization of the system, have been achieved. Both subjects were able to voluntarily open and close the prosthesis hand with no significant delays from intention to action (approximately 120 ms). Quantitative analyses revealed 88% and 71% control accuracy for subjects 1 and 2, respectively.     

Geometry and mechanics of the human ankle complex and ankle prosthesis design

The main objective of the study was to develop a model of the intact human ankle complex. It was also aimed at designing total ankle replacement which would better reproduce the physiological function of the joint. Passive flexion was analysed in seven lower-leg preparations with a stereophotogrammetric system. The articular surfaces and fibres within the calcaneofibular and tibiocalcaneal ligaments prescribed the changing positions of the axis of rotation. Joint motion included rolling as well as sliding. A computer-based model elucidated the observed kinematics at the intact joint. The experimental evidence and the geometrical model gave the basis for the design of models of replaced ankle in the sagittal plane. A three-component, convex-tibia prosthesis was eventually selected with articular surface shapes compatible with the geometry of the ligaments. It was demonstrated that in intact ankle joint, the geometry of the articular surfaces is strictly related to that of the ligaments and that current prosthesis designs do not restore physiological pattern of ligament tensioning. Careful reconstruction of the ligaments is recommended in any ankle surgery for maintenance of the normal kinematics and mechanics. A proposed novel design based on ligament/shape compatibility may improve total ankle replacement results.     

Acoustic myography as a control signal for an externally powered prosthesis

Contracting skeletal muscle produces sounds that are easily recorded with a standard microphone. The recording of these sounds is known as acoustic myography, or AMG. As a control signal for an externally powered prosthesis, some advantages of AMG over surface EMG are: there is no need for direct skin contact; the AMG signal is unaffected by changes in skin impedence; AMG intensity is high enough to produce a 50 mV output from a standard microphone, requiring less amplification and electrical shielding; the AMG signal is qualitatively less sensitive to placement on the muscle than EMG. Disadvantages, such as the susceptibility of AMG to interference by extraneous environmental noise, are relatively easy to overcome. To demonstrate this, we have constructed a myoacoustically controlled prosthetic hand, whose tristate control via a single microphone (vs differential control) proves its feasibility in the more difficult case. The control circuitry for this device costs less than $50. The existing device utilizes a free-standing hand; a prosthetic shell which will allow comparison of AMG vs EMG control is currently being designed. The two patients who have tried it have learned to open and close the hand reliably after only three minutes of practice. Protocols are being established for functional assessment of AMG control.     

Human-prosthesis coordination: A preliminary study exploring coordination with a powered ankle-foot prosthesis

BackgroundPowered ankle-foot prostheses were developed to replicate the mechanics of the biological ankle by providing positive work during the push-off phase of gait. However, the benefits of powered prostheses on improving overall human gait efficiency (usually quantified by metabolic cost) have not been consistently shown. Here, we have focused on the mechanical work produced at the prosthetic ankle and its interaction with the amputee's movement.MethodsFive unilateral transtibial amputees walked on a treadmill using 1) a powered ankle-foot prosthesis and 2) their daily passive device. We determined the net ankle work and ankle work loops on the prosthesis-side to quantify the efficiency of the human-prosthesis physical interaction. We further studied peak propulsion timing and the posture of the amputee's lower limb and prosthesis as indicators of the human-prosthesis coordination. Comparisons were made between the passive and powered prosthesis conditions for each participant.FindingsThe powered prosthesis did not consistently increase net ankle work compared to each participant's passive device. For participants that lacked efficiency in interacting with the powered prosthesis, we observed 1) early prosthesis-side peak propulsion timing (≥ 4% earlier) and 2) a more vertical residual shank at the time of peak propulsion (> 2° more vertical) indicating that the human's limb movement and the prosthesis control during push-off were not well coordinated.InterpretationResults from this preliminary study highlight the need for future work to systematically quantify the coordination between the human and powered prosthesis and understand how such coordination at the joint level influences overall gait efficiency.     

Novel passive ankle-foot prosthesis mimics able-bodied ankle angles and ground reaction forces

Background: During gait, the human ankle both bends with ease and provides push-off forces that facilitate forward motion. The ankle is crucial for support, stabilization, and adapting to different slopes and terrains. Individuals with lower limb amputation require an ankle-foot prosthesis for basic mobility.Methods: Inspired by the role of the ankle-foot in an able-bodied gait, the 3D printed Compliant and Articulating Prosthetic Ankle (CAPA) foot was designed. It consists of four articulating components connected by torsion springs and produces forces that are dependent on the ankle angle. Using the Computer Assisted Rehabilitation Environment, able-bodied individuals walked wearing a prosthetic simulator with the Solid Ankle Cushioned Heel foot, Renegade® AT, and multiple versions of the CAPA. These versions test compliant vs. stiff, small vs. large rocker radius, and pretension vs. none. We hypothesized that the CAPA would have larger ankle range of motion, push-off forces, and braking forces.Findings: Compared to existing prostheses, the novel prosthesis exhibits greater and significantly different ankle range of motion and sagittal plane ground reaction forces than existing prostheses during gait. Nine out of ten individuals prefer the novel prosthesis to the existing prostheses, and there is a statistically significant difference in difficulty level ratings.Interpretation: By providing a personalizable and passive alternative to existing designs, the CAPA could improve the quality of life for the growing number of individuals living with limb loss in the United States and around the world.     

The effects of static friction and backlash on extended physiological proprioception control of a powered prosthesis

In general, externally powered prostheses do not provide proprioceptive feedback and thus require the user to rely on cognitively expensive visual feedback to effectively control the prosthesis. Applying the concept of extended physiological proprioception (EPP) to externally powered prostheses provides direct feedback to the user's proprioceptive system regarding the position, velocity, and forces applied to the prosthesis. However, electric elbows with EPP controllers developed at the Northwestern University Prosthetics Research Laboratory have exhibited unexplained "jerky" behavior in both clinical fittings and bench-top operation. In addition, the development of limit cycles, a specific type of constant-amplitude oscillation, had been observed in bench-top use of these elbows. Backlash and static friction within the EPP system were found to be primarily responsible for the development of limit cycles. Reducing static friction and backlash improved the system's performance. These results suggest that to most effectively implement EPP, prosthesis manufacturers should design prosthetic components that minimize static friction and backlash.     

踝关节可左右摆动的康复器具设计

背景:下肢康复辅具在下肢功能恢复训练中占有越来越重要的地位。目的:设计了一种新型的踝关节康复器具,达到对髋关节、膝关节、踝关节康复运动的目的。方法:基于三维设计软件Solidworks,设计了一种新型踝关节康复辅具,增加了踝关节左右摆动功能。结果与结论:在国内外踝关节康复器具研究基础上,增加了踝关节左右摆动功能的新型踝关节康复器具,3D运动仿真结果表明方案有效可行。     

踝关节可左右摆动的康复器具设计

背景：下肢康复辅具在下肢功能恢复训练中占有越来越重要的地位。目的：设计了一种新型的踝关节康复器具,达到对髋关节、膝关节、踝关节康复运动的目的。方法：基于三维设计软件Solidworks,设计了一种新型踝关节康复辅具,增加了踝关节左右摆动功能。结果与结论：在国内外踝关节康复器具研究基础上,增加了踝关节左右摆动功能的新型踝关节康复器具,3D运动仿真结果表明方案有效可行。