Collaborative Research: Integrating Optimal Function and Compliant Mechanisms for Ubiquitous Lower-Limb Powered Prostheses

大多数的假肢都是被动的。它们可以消散和储存机械能量，但不能产生正净能量。缺乏发电限制了需要使用者逆重力移动的运动，如上楼或从坐着过渡到站着。这种动力不足可能会导致身体负荷不均，这可能会增加慢性背痛的可能性，并增加行走的努力。主动假体有可能克服这些根本性的挑战。然而，商业上可获得的电动假体比非电动假体更重、更嘈杂、更昂贵，而且通常更难获得。该项目的总体目标是将现有的刚性假体部件重新想象为柔顺机构，以减少动力假体的质量、能源消耗、可听噪音和部件数量。肌肉利用肌腱(与肌肉串联)和韧带(与肌肉平行)的弹性，有效地将力量从肌肉转移到关节。该项目将对如何将弹性元件与电动马达并行设计为工程韧带提供新的理解，以使动力假体更具吸引力和可达性。柔顺机构的性能和行为取决于三个基本因素：1)材料特性，2)几何形状，3)载荷-挠度响应。这个项目将开发新的知识来设计与电机并联的柔顺机构的负载-偏转响应和几何形状，以减少电机扭矩。这种减速意味着更轻、更节能、更安静的假肢，因为它需要更低的减速比、更少的齿轮啮合、更轻的电机和更少的散热。圣母大学和杨百翰大学的这一合作项目将建立两个科学贡献：1)稳健的凸形优化框架，用于设计平行弹簧的负载-偏转响应，确保在多个运动活动中尽管存在参数不确定性(例如，用户质量、行走速度)时电机扭矩降低；以及2)具有最佳负载-偏转曲线的柔顺机构设计框架，以重新设计现有的刚性部件，并在不折衷机械复杂性或额外部件的情况下实现并行顺应的好处。这些创新的应用将产生与开源兼容的脚踝，在线提供开源设计，补充现有的NSF资助的开源腿。研究团队将与非营利性组织2英尺假体和当地截肢者支持团体合作，将假肢使用者、制造商和临床医生的反馈纳入新的设计。这项研究的成果将包括组织一次会议研讨会，在可穿戴机器人研究生级别的课堂上增加新内容，以及为对STEM教育感兴趣的当地中学生提供为期3周的暑期计划。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The majority of lower-limb prostheses are passive. They can dissipate and store mechanical power but cannot generate positive net power. The lack of power generation limits movements that require the user to move against gravity, such as going upstairs or transitioning from sitting to standing. This lack of power may induce uneven loads in the body, which can increase the likelihood of chronic back pain and increase the effort to walk. Active prostheses have the potential to overcome these fundamental challenges. However, commercially available powered prostheses are heavier, noisier, more expensive, and generally less accessible than unpowered versions. The overall goal of this project is to reimagine existing rigid prosthetic components as compliant mechanisms that reduce mass, energy consumption, audible noise, and part count of powered prostheses. Muscles take advantage of the elasticity of tendons (in series with the muscle) and ligaments (in parallel with the muscle) to efficiently transfer power from the muscle to the joints. This project will provide a new understanding of how to engineer elastic components in parallel with electric motors as engineered ligaments to make powered prostheses more attractive and accessible.The performance and behavior of compliant mechanisms depend on three fundamental factors: 1) material properties, 2) geometry, and 3) load-deflection response. This project will develop new knowledge to design the load-deflection response and geometry of compliant mechanisms that connect in parallel with electric motors to reduce motor torque. This reduction implies lighter, more energy-efficient, and quieter prostheses, as it requires lower reduction ratios, fewer gears meshing, lighter motors, and less heat dissipation. This collaborative project between the University of Notre Dame and Brigham Young University will establish two scientific contributions: 1) a robust convex optimization framework to design the load-deflection response of a parallel spring that guarantees motor torque reduction in multiple locomotion activities despite parametric uncertainty (e.g., user mass, walking speed); and 2) a design framework for compliant mechanisms with optimal load-deflection profiles to reimagine existing rigid components and implement the benefits of parallel compliance without a tradeoff in terms of mechanical complexity or extra components. The application of these innovations will result in an Open-Source Compliant Ankle, with open-source designs available online that complement the existing NSF-funded Open-Source Leg. The research team will collaborate with non-profit organization 2ft Prosthetics and local Amputee Support Groups to incorporate the feedback from prosthetic users, manufacturers, and clinicians into new designs. The outcomes of this research will include the organization of a conference workshop, new content in a graduate-level class on Wearable Robotics, and a 3-week summer program for local middle schoolers interested in STEM education.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.