Tucker Michael R, Shirota Camila, Lambercy Olivier, Sulzer James S, Gassert Roger
IEEE Trans Biomed Eng. 2017 Oct;64(10):2331-2343. doi: 10.1109/TBME.2017.2656130. Epub 2017 Jan 20.
An improved understanding of mechanical impedance modulation in human joints would provide insights about the neuromechanics underlying functional movements. Experimental estimation of impedance requires specialized tools with highly reproducible perturbation dynamics and reliable measurement capabilities. This paper presents the design and mechanical characterization of the ETH Knee Perturbator: an actuated exoskeleton for perturbing the knee during gait.
A novel wearable perturbation device was developed based on specific experimental objectives. Bench-top tests validated the device's torque limiting capability and characterized the time delays of the on-board clutch. Further tests demonstrated the device's ability to perform system identification on passive loads with static initial conditions. Finally, the ability of the device to consistently perturb human gait was evaluated through a pilot study on three unimpaired subjects.
The ETH Knee Perturbator is capable of identifying mass-spring systems within 15% accuracy, accounting for over 95% of the variance in the observed torque in 10 out of 16 cases. Five-degree extension and flexion perturbations were executed on human subjects with an onset timing precision of 2.52% of swing phase duration and a rise time of 36.5 ms.
The ETH Knee Perturbator can deliver safe, precisely timed, and controlled perturbations, which is a prerequisite for the estimation of knee joint impedance during gait.
Tools such as this can enhance models of neuromuscular control, which may improve rehabilitative outcomes following impairments affecting gait and advance the design and control of assistive devices.
更好地理解人体关节中的机械阻抗调制，将有助于深入了解功能运动背后的神经力学原理。阻抗的实验估计需要具备高度可重复的扰动动力学和可靠测量能力的专业工具。本文介绍了ETH膝关节扰动器的设计与力学特性：一种在步态过程中对膝关节进行扰动的驱动外骨骼。
基于特定的实验目标开发了一种新型可穿戴扰动装置。台架试验验证了该装置的扭矩限制能力，并对车载离合器的时间延迟进行了表征。进一步的测试证明了该装置在静态初始条件下对被动负载进行系统识别的能力。最后，通过对三名未受损受试者的初步研究，评估了该装置持续扰动人类步态的能力。
ETH膝关节扰动器能够以15%的精度识别质量-弹簧系统，在16个案例中的10个案例中，解释了观察到的扭矩中超过95%的方差。对人体受试者进行了5度的伸展和屈曲扰动，起始时间精度为摆动相持续时间的2.52%，上升时间为36.5毫秒。
ETH膝关节扰动器能够提供安全、定时精确且可控的扰动，这是在步态过程中估计膝关节阻抗的先决条件。
这样的工具可以增强神经肌肉控制模型，这可能会改善影响步态的损伤后的康复效果，并推动辅助设备的设计和控制。
