Assessment of Human Dynamic Gait Stability With a Lower Extremity Assistive Device
Assessment of Human Dynamic Gait Stability With a Lower Extremity Assistive Device
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DOI：
10.1109/tnsre.2020.2970207
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发表时间：
2020-03-01
影响因子：
4.9
通讯作者：
Zhang, Wenlong
中科院分区：
文献类型：
--
作者：
Chinimilli, Prudhvi Tej;Sorkhabadi, Seyed Mostafa;Zhang, Wenlong
本文重点关注通过动力系统理论推导出的指标评估步态稳定性，以了解单侧机器人辅助对人类步行模式的影响。一个电动辅助机器人被应用到右膝关节提供站立支持。考虑了与全局稳定性（最大Floquet乘数，最大FM），局部稳定性（短期和长期发散指数，$\lambda _{\text {s}}$和$\lambda _{\text {l}}$）和可变性（中位数绝对偏差，MAD）相关的度量。这些指标是针对双侧髋关节、膝关节和踝关节角度得出的。此外，还评估了生物力学指标，即最小稳定性边缘。实验进行了11个健康的参与者与不同的机器人控制器。最大FM和$\lambda _{\text {s}}$产生统计上显著的结果，表明由于肢体间协调，与正常行走条件相比，在右膝辅助条件下，无辅助（左腿）腿更稳定。此外，MAD和$\lambda _{\text {l}}$表明，辅助期间步行模式的变异性和混乱秩序低于正常步行。所提出的控制策略（自动阻抗调谐，AIT）提高了本地和轨道步态稳定性相比，现有的控制器，如有限状态机（FSM）。本文提出的动态步态稳定性的评估提供了见解，进一步改善辅助机器人的控制策略，以帮助用户达到改善步态稳定性，同时保持适当的可变性。
This paper focuses on assessing gait stability by metrics derived from dynamical systems theory to understand the influence of unilateral robot assistance on the human walking pattern. A motorized assistive robot is applied to the right knee joint to provide stance support. The metrics related to global stability (the maximum Floquet multiplier, max FM), local stability (short-term and long-term divergence exponents, $\lambda _{\text {s}}$ and $\lambda _{\text {l}}$ ), and variability (median absolute deviation, MAD) are considered. These metrics are derived for bilateral hip, knee, and ankle joint angles. Additionally, a biomechanical metric, the minimum margin of stability is assessed. Experiments are conducted on 11 healthy participants with different robot controllers. The max FM and $\lambda _{\text {s}}$ yield statistically significant results, showing that the unassisted (left) leg is more stable in right knee assistance conditions when compared to the normal walking condition due to inter-limb coordination. Moreover, MAD and $\lambda _{\text {l}}$ show that the variability and chaotic order of walking pattern during assistance are lower than those of normal walking. The proposed control strategy (automatic impedance tuning, AIT) improves local and orbital gait stability compared to existing controllers such as finite-state machine (FSM). The assessment of dynamic gait stability presented in this paper provides insights for further improving control strategies of assistive robots to help a user reach improved gait stability while maintaining appropriate variability.