Liu Yuyao, Sun Ronglei, Zou Kaijie, Li Ying, Xu Peng
Institute of Medical Equipment Science and Engineering, Huazhong University of Science and Technology, Wuhan, China.
State Key Laboratory of Intelligent Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, China.
Front Bioeng Biotechnol. 2024 Aug 5;12:1429605. doi: 10.3389/fbioe.2024.1429605. eCollection 2024.
The ankle-foot exoskeleton has been demonstrated to help users resist anterior perturbation in the horizontal pelvis plane. However, its effects on perturbations in other directions remain unclear. This paper focuses on how the ankle-foot exoskeleton helps people resist perturbations coming from forward directions within the fan-shaped region in the pelvis horizontal plane. Firstly, we proposed and validated a hypothesis that the human torque ratio of inversion to plantar flexion torque would change with the perturbation directions of anterior (dir0) and 45° deviating from anterior to left (dir45). Subsequently, based on the regulation demand, we developed an ankle-foot exoskeleton that can adjust the torque ratio delivered to the human body by controlling the forces on two cross-arranged cables. Finally, we evaluated and compared the assistance performance of three powered assistive modes (NM, medBD, and latBD) with the unpowered one (UN) by setting different force pairs in two cables. The results showed that, with the assistance, the margin of stability was increased and the standard deviations of ankle-foot segmental movements were decreased. Meanwhile, the biological inversion torque has a significant difference among the three assistive modes. Compared to the UN, the latBD was shown to reduce the biological inversion torque by 15.8 and 13.7 in response to the dir0 and dir45 perturbations, respectively, while the reductions for the NM and medBD were smaller. It was also observed that the torque ratios, generated by the human and the exoskeleton in latBD mode, differed by about 0.1 under dir0 and 0.08 under dir45, while the physiologically similarity of the exoskeleton torque ratio in NM and medBD modes were smaller. Based on the above results, we found that the more physiologically similar the exoskeleton torque ratio, the better the assistive performance. The findings demonstrated that the torque-ratio-adjustable exoskeleton could support human resistance to perturbations coming from forward directions within a fan-shaped region in the pelvis horizontal plane and indicated that the exoskeleton's torque ratio should be carefully modulated to match the ratio of the human under various environmental conditions for better assistive performance.
踝关节-足部外骨骼已被证明有助于使用者在骨盆水平平面内抵抗向前的扰动。然而，其对其他方向扰动的影响仍不清楚。本文重点研究踝关节-足部外骨骼如何帮助人们抵抗来自骨盆水平平面扇形区域内向前方向的扰动。首先，我们提出并验证了一个假设，即人体内翻扭矩与跖屈扭矩的比值会随着向前（dir0）以及从前向左偏离45°（dir45）的扰动方向而变化。随后，根据调节需求，我们开发了一种踝关节-足部外骨骼，它可以通过控制两根交叉布置的缆绳上的力来调节传递给人体的扭矩比值。最后，我们通过在两根缆绳上设置不同的力对，评估并比较了三种动力辅助模式（NM、medBD和latBD）与无动力模式（UN）的辅助性能。结果表明，在辅助作用下，稳定性裕度增加，踝关节-足部节段运动的标准差减小。同时，三种辅助模式下的生物内翻扭矩存在显著差异。与UN相比，latBD在应对dir0和dir45扰动时，生物内翻扭矩分别降低了15.8和13.7，而NM和medBD的降低幅度较小。还观察到，在latBD模式下，人体和外骨骼产生的扭矩比值在dir0时相差约0.1，在dir45时相差0.08，而在NM和medBD模式下，外骨骼扭矩比值的生理相似性较小。基于上述结果，我们发现外骨骼扭矩比值在生理上越相似，辅助性能越好。研究结果表明，扭矩比值可调的外骨骼能够支持人体抵抗来自骨盆水平平面扇形区域内向前方向的扰动，并表明应仔细调节外骨骼的扭矩比值，以使其在各种环境条件下与人体的比值相匹配，从而获得更好的辅助性能。
