Wang Wei, Ding Jianquan, Wang Yi, Liu Yicheng, Zhang Juanjuan, Liu Jingtai
Institute of Robotics and Automatic Information System, College of Artificial Intelligence, Nankai University, Tianjin 300350, P. R. China.
Tianjin Key Laboratory of Intelligent Robotics, Tianjin 300350, P. R. China.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2022 Feb 25;39(1):75-83. doi: 10.7507/1001-5515.202107040.
Lower limb ankle exoskeletons have been used to improve walking efficiency and assist the elderly and patients with motor dysfunction in daily activities or rehabilitation training, while the assistance patterns may influence the wearer's lower limb muscle activities and coordination patterns. In this paper, we aim to evaluate the effects of different ankle exoskeleton assistance patterns on wearer's lower limb muscle activities and coordination patterns. A tethered ankle exoskeleton with nine assistance patterns that combined with differenet actuation timing values and torque magnitude levels was used to assist human walking. Lower limb muscle surface electromyography signals were collected from 7 participants walking on a treadmill at a speed of 1.25 m/s. Results showed that the soleus muscle activities were significantly reduced during assisted walking. In one assistance pattern with peak time in 49% of stride and peak torque at 0.7 N·m/kg, the soleus muscle activity was decreased by (38.5 ± 10.8)%. Compared with actuation timing, the assistance torque magnitude had a more significant influence on soleus muscle activity. In all assistance patterns, the eight lower limb muscle activities could be decomposed to five basic muscle synergies. The muscle synergies changed little under assistance with appropriate actuation timing and torque magnitude. Besides, co-contraction indexs of soleus and tibialis anterior, rectus femoris and semitendinosus under exoskeleton assistance were higher than normal walking. Our results are expected to help to understand how healthy wearers adjust their neuromuscular control mechanisms to adapt to different exoskeleton assistance patterns, and provide reference to select appropriate assistance to improve walking efficiency.
下肢踝关节外骨骼已被用于提高步行效率，并在日常活动或康复训练中辅助老年人及运动功能障碍患者，而辅助模式可能会影响穿戴者的下肢肌肉活动和协调模式。在本文中，我们旨在评估不同踝关节外骨骼辅助模式对穿戴者下肢肌肉活动和协调模式的影响。使用了一种具有九种辅助模式的系留式踝关节外骨骼，这些模式结合了不同的驱动时机值和扭矩大小水平来辅助人体行走。从7名参与者以1.25 m/s的速度在跑步机上行走时采集下肢肌肉表面肌电信号。结果表明，在辅助行走过程中比目鱼肌的活动显著减少。在一种峰值时间为步幅的49%且峰值扭矩为0.7 N·m/kg的辅助模式下，比目鱼肌的活动降低了(38.5 ± 10.8)%。与驱动时机相比，辅助扭矩大小对比目鱼肌活动的影响更为显著。在所有辅助模式下，八个下肢肌肉活动可分解为五种基本肌肉协同作用。在适当的驱动时机和扭矩大小的辅助下，肌肉协同作用变化不大。此外，外骨骼辅助下比目鱼肌与胫骨前肌、股直肌与半腱肌的共同收缩指数高于正常行走。我们的研究结果有望有助于理解健康穿戴者如何调整其神经肌肉控制机制以适应不同的外骨骼辅助模式，并为选择合适的辅助方式以提高步行效率提供参考。
