Wang Yichen, Perez Jose A Montes, Gregg Robert D, Thomas Gray C
IEEE Int Conf Rehabil Robot. 2025 May;2025:648-655. doi: 10.1109/ICORR66766.2025.11062962.
Assistive lower-body exoskeletons aim to improve quality of life for broad populations including older adults and people in physically exhausting manual jobs. By applying torque to augment human motion with backdrivable actuators, these devices can reduce human joint effort without restricting volitional motion. However, these backdrivable actuators are coupled by mechanical interfaces to soft tissues of the human body that together introduce resonator dynamics that can delay or diminish the torque assistance. Low interface stiffness and uncompensated dynamics can cause inefficient power delivery to the user, alter their perceived assistance and comfort, and destabilize feedback controllers. We hypothesize that the low stiffness in lateral strap interfaces, like those in the opensource M-BLUE exoskeleton, can be improved by mechanical redesign. Building on the open-source M-BLUE exoskeleton, this paper introduces an alternative interface design that loads the leg through anterior and posterior pads (normal loading) and straps, in which the pads provide extension assistance and the straps provide flexion assistance. We compare the interface dynamics of lateral and normal loading interfaces on N = 10 human subjects using both quasi-static spring measurements and frequency response methods, finding the new design to be 85.7% stiffer $(p<0.01)$ for a range of leg poses and in both flexion and extension loading.
下肢辅助外骨骼旨在改善包括老年人和从事体力消耗大的体力工作的人群在内的广大人群的生活质量。通过应用扭矩，利用可回驱致动器增强人体运动，这些设备可以减少人体关节的用力，同时又不限制自主运动。然而，这些可回驱致动器通过机械接口与人体软组织相连，这共同引入了谐振器动力学，可能会延迟或减弱扭矩辅助。低接口刚度和未补偿的动力学可能导致向用户传递功率效率低下，改变他们所感受到的辅助和舒适度，并使反馈控制器不稳定。我们假设，像开源M-BLUE外骨骼中的横向绑带接口那样的低刚度，可以通过机械重新设计来改善。基于开源M-BLUE外骨骼，本文介绍了一种替代接口设计，该设计通过前后护垫（垂直加载）和绑带来加载腿部，其中护垫提供伸展辅助，绑带提供屈曲辅助。我们使用准静态弹簧测量和频率响应方法，比较了N = 10名人类受试者上横向加载接口和垂直加载接口的接口动力学，发现在一系列腿部姿势以及屈曲和伸展加载中，新设计的刚度提高了85.7%（p<0.01）。
