Optimizing impedance control of an ankle exoskeleton to improve post-stroke walking mechanics and energetics

项目摘要 在美国，700万中风幸存者中约有80%受到轻偏瘫的影响，或 身体一侧的肌肉无力。与正常步态相比，轻偏瘫行走 不对称且缓慢。在踝关节动力输出方面，已记录了高肢体间不对称性， 中风后的步行速度范围在<0.2 m/s和~0.8 m/s之间，而健康成人的步行速度为~1.4 m/s。 中风后步态特征的改变与行走能力的限制有关 包括改变下肢关节的负荷和增加代谢成本。关节载荷的变化是 与继发性疾病相关，包括骨关节炎，下背痛，以及由于活动减少， 心血管疾病此外，代谢成本的增加导致快速疲惫，活动减少， 有限的流动性。旨在减少机械不对称的干预措施可能会降低代谢成本， 使关节负荷正常化，以改善中风后的行走性能。踝关节外骨骼已经成功地 在健康对照组中，步行的代谢成本降低，初步研究表明， 踝关节外骨骼，以恢复踝关节的功能，通过施加踝关节扭矩对瘫痪的肢体。长期目标 这项研究的目的是开发一种机器人踝关节外骨骼，可以改善中风后的行走性能， 为便携式永久助行器铺平道路。然而，用于中风的外骨骼设计受到限制， 关于外骨骼辅助时间和幅度对机械步态的影响的知识差距 对称性、代谢成本和关节接触载荷。理解这种关系至关重要，因为 在错误的时间提供的外骨骼辅助或程度不足的外骨骼辅助可能是无用的，甚至 不利于步态表现。我们将使用实验和计算相结合的方法来研究 以下目标：（1）确定外骨骼辅助的时机和幅度如何影响 中风后行走的机械对称性和代谢能量学（2）确定时间和幅度 影响关节接触力。我们将使用外骨骼模拟器系统， 系统地改变外骨骼辅助参数（即，定时和幅度），同时直接评估用户 代谢、运动学和动力学反应。由于我们无法在体内轻松测量关节接触力， 将应用由实验测量的步态驱动的计算模拟方法， 借助外骨骼辅助行走。这项工作将阐明如何定时和规模的外骨骼 辅助影响中风后行走不对称性、代谢成本和关节接触力。综合起来看， 这些目标提供了新的和必要的信息， 最大限度地减少合并症并恢复中风幸存者的活动能力。

Project Summary Approximately 80% of the 7 million stroke survivors in the United States are affected by hemiparesis, or muscle weakness on one side of the body. When compared to unimpaired gait, hemiparetic walking is both asymmetric and slow. High interlimb asymmetry has been documented in ankle joint power output, and preferred walking speeds following a stroke range between <0.2 m/s and ~0.8 m/s compared to ~1.4 m/s in healthy adults. Alterations in gait characteristics following a stroke are associated with limitations in walking performance including altered loading on lower limb joints and increased metabolic cost. Changes in joint loading are associated with secondary diseases including osteoarthritis, lower-back pain, and due to reduced activity, cardiovascular disease. Additionally, increases in metabolic cost lead to rapid exhaustion, less activity and limited mobility. Interventions designed to reduce mechanical asymmetries may reduce metabolic cost and normalize joint loading for improved walking performance post stroke. Ankle exoskeletons have successfully reduced metabolic cost of walking in healthy controls and preliminary studies have demonstrated the potential of ankle exoskeletons to restore ankle function by applying ankle torque on the paretic limb. The long term goal of this research is to develop a robotic ankle exoskeleton that can improve walking performance post stroke to pave the way for a portable permanent walking aid. However, exoskeleton design for stroke is limited by a knowledge gap regarding the influence of exoskeleton assistance timing and magnitude on mechanical gait symmetry, metabolic cost, and joint contact loading. Understanding this relationship is critical because exoskeleton assistance provided at the wrong time, or of insufficient magnitude could be useless, or even detrimental to gait performance. We will use a combined experimental and computational approach to research the following aims: (1) Determine how the timing and magnitude of exoskeleton assistance influence the mechanical symmetry and metabolic energetics of post-stroke walking (2) Determine how timing and magnitude of exoskeleton assistance influences joint contact forces. We will use an exoskeleton emulator system to systematically vary exoskeleton assistance parameters (i.e. timing and magnitude) while directly evaluating user metabolic, kinematic, and kinetic response. Because we cannot easily measure joint contact forces in vivo, we will apply a computational simulation approach driven by the experimentally measured gait for each participant walking with exoskeleton assistance. This work will elucidate the how timing and magnitude of exoskeleton assistance impacts post-stroke walking asymmetry, metabolic cost and joint contact forces. Taken together, these aims provide new and essential information to enable the development of exoskeletons capable of minimizing comorbidities and restoring mobility to stroke survivors.