CAREER: Reverse Engineering Human Leg Mechanics to Transform Control of Robotic Prostheses

使截肢者能够行走的辅助装置的进展，例如，近年来，机器人假肢、矫形器和外骨骼已经相当可观。 然而，现有的系统在包括意外干扰的动态真实世界环境中操作有困难。因此，这个CAREER项目的目标是通过利用人类运动的潜在动力学，即，通过在真实的时间内提供具有改变关节刚度和阻尼特性的相同能力的装置，人类通过肌肉激活在不知不觉中调节关节刚度和阻尼特性。关键的想法是了解神经系统如何在整个行走过程中调节腿部关节的刚度和阻力，并将这些信息用于设计和控制辅助机器人的新的生物灵感蓝图。该项目还将深入了解人体如何对干扰作出反应。该项目的成果将显著改善美国100多万下肢截肢者的生活质量和生产力。在整个项目中，研究和教育的整合将产生广泛的影响，通过1）通过有针对性的活动，展示工程的正式和“制造商”方面，促进STEM和残疾意识的K-12学生，2）实施跨学科机制，在工程专业学生和临床医生之间进行知识转移，和3）赞助和指导学生高级设计项目，通过与临床医生的共同监督直接支持这项研究。首席研究员的长期-长期的研究目标是推进一种变革性的方法来设计和控制辅助机器人，拥抱和利用人类运动的基本动力学。为了实现这一目标，该项目将测量膝关节在行走过程中的机械阻抗，并利用所获得的信息开发新一代生物启发控制系统，使辅助机器人的用户能够在包括意外干扰的动态环境中更自由地移动。 研究将利用主要研究者实验室已经开发或正在开发的辅助设备：用于膝盖的扭矩可控外骨骼和开源机器人腿假体（OSL，根据NSF奖项开发），为膝踝关节提供动力。 研究计划是根据三个目标组织的。 第一个目的是研究使用扭矩可控外骨骼测量膝关节机械阻抗的技术，该技术将在行走期间在健全受试者中进行量化。 方法将在弹簧和质量的被动机械系统中进行验证，在涉及人类受试者之前，阻抗是已知的。可用于确定运动期间膝盖的机械阻抗的数据将从穿戴膝盖外骨骼的人类受试者记录，同时在分裂带跑步机上行走，其中可施加小扰动（例如，增加的斜坡角度）且通过外骨骼测量响应扭矩。 施加扰动，以便在步态周期的每个点获得阻抗快照。 点阻抗将通过将惯性、刚度和阻尼参数拟合到二阶微分方程来量化。 第二个目标是推导出腿的生物激励阻抗控制的控制方程，该控制方程将在用于控制OSL的开源库中实现。目标1下获得的结果将与估计踝关节阻抗的初步工作合成，以推导出统一的控制律，该控制律能够同时调节膝踝关节动力学、运动学和机械阻抗。 控制方程将被转换成软件库，该软件库能够命令OSL并实现膝踝阻抗的实时控制，即，刚度、阻尼和平衡位置参数将作为步态相位的函数而改变，并且因此不倾向于单一速度。 OSL实现所需刚度和阻尼系数的能力将在实验室试验装置中得到确认。 第三个目的是了解基于阻抗的控制系统在膝上截肢者使用OSL的效果，在有/无干扰的截肢过程中进行测试。 受试者将在使用阻抗控制系统和每个人的处方假肢以自选速度在地面行走时进行研究。随后的研究将调查受试者在仪器跑步机上行走时干扰的影响。 将比较各种条件下的动力学，运动学，代谢和稳定性措施，以更好地了解生物启发控制方法如何影响截肢者的活动性，以及这些措施如何与健全的身体力学进行比较。 虽然会有几个干扰，这个项目将集中在理解的影响，步行的倾斜和下降。这个奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的知识价值和更广泛的影响审查标准。

Advances in assistive devices that enable individuals with leg amputations to walk, e.g., robotic prosthesis, orthoses and exoskeletons, have been considerable in recent years. However, existing systems have trouble operating in dynamic, real-world environments that include unexpected disturbances. Thus, the goal of this CAREER project is to address the need for assistive robots that can naturally respond to disturbances by exploiting the underlying dynamics of human locomotion, i.e., by providing the device, in real time, with the same abilities to change joint stiffness and damping properties that humans unknowingly regulate through muscle activations. The key idea is to understand how the nervous system regulates leg joint stiffness and resistance throughout walking, and use this information for a new, bio-inspired blueprint for design and control of assistive robotics. This project will also provide insight into how the human body responds to disturbances. The results from this project will significantly improve quality of life and productivity for over a million lower-limb amputees in the U.S. alone. Throughout the project, the integration of research and education will have broad impact through the 1) promotion of STEM and disability awareness to K-12 students through targeted events that showcase the formal and "maker" sides of engineering, 2) implementation of interdisciplinary mechanisms for knowledge transfer between engineering students and clinicians, and 3) sponsorship and mentoring of student senior design projects that directly support this research through co-oversight with clinicians.The principal investigator's long-term research goal is to advance a transformative approach to the design and control of assistive robots that embrace and exploit the underlying dynamics of human locomotion. Towards this goal, this project will measure the mechanical impedance of the knee joint during walking and use the information obtained to develop a new generation of bio-inspired control systems that will enable users of assistive robots to move more freely in dynamic environments that include unexpected disturbances. Studies will make use of assistive devices already developed or under development in the principal investigator's lab: a torque-controllable exoskeleton for the knee and an Open-Source Robotic Leg prosthesis (OSL, developed under an NSF award) that has powered knee-ankle joints. The Research Plan is organized under three aims. The FIRST AIM is to investigate techniques for measuring knee mechanical impedance using the torque-controllable exoskeleton, which will be quantified in able-bodied subjects during walking. Methodologies will be validated in a passive mechanical system of springs and masses for which impedances are known before involving human subjects. Data that can be used to determine mechanical impedance of the knee during locomotion will be recorded from human subjects wearing the knee exoskeleton while walking on a split-belt treadmill in which small perturbations (e.g. increased ramp angle) can be applied and response torques measured by the exoskeleton. Perturbations will be applied such that a snapshot of impedance can be obtained at each point during the gait cycle. Point impedances will be quantified by fitting inertia, stiffness and damping parameters to a second-order differential equation. The SECOND AIM is to derive governing equations for bio-inspired impedance control of the leg that will be implemented in an open-source library for control of the OSL. The results obtained under Aim 1 will be synthesized with preliminary work estimating the impedance of the ankle to derive a unified control law that enables simultaneous regulation of knee-ankle kinetics, kinematics and mechanical impedance. The governing equations will be translated into a software library that is able to command the OSL and enables real-time control of knee-ankle impedance, i.e., stiffness, damping and equilibrium position parameters will be altered as a function of gait phase and, thus, not predisposed to a single speed. The ability of the OSL to achieve the desired stiffness and dampening coefficients will be validated in a benchtop testing setup. The THIRD AIM is to understand the effect of the impedance-based control system in above-knee amputees using the OSL, tested during ambulation with/without disturbances. Subjects will be studied while ground walking at a self-selected pace with both the impedance-controlled system and each person's prescribed prosthesis. A subsequent study will investigate the effect of disturbances while subjects are walking on an instrumented treadmill. Kinetics, kinematics, metabolics and stability measures across conditions will be compared to better understand how the bio-inspired control approach affects amputee mobility and how these measures compare to able-body mechanics. Though several disturbances will be applied, this project will focus on understanding the effect of walking on inclines and declines.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.