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Frontiers of Information Technology & Electronic Engineering

ISSN 2095-9184 (print), ISSN 2095-9230 (online)

Fall preventive gait trajectory planning of a lower limb rehabilitation exoskeleton based on capture point theory

Abstract: We study the balance problem caused by forward leaning of the wearer’s upper body during rehabilitation training with a lower limb rehabilitation exoskeleton. The instantaneous capture point is obtained by modeling the human-exoskeleton system and using the capture point theory. By comparing the stability region with instantaneous capture points of different gait phases, the balancing characteristics of different gait phases and changes to the equilibrium state in the gait process are analyzed. Based on a model of the human-exoskeleton system and the condition of balance of different phases, a trajectory correction strategy is proposed for the instability of the human-exoskeleton system caused by forward leaning of the wearer’s upper body. Finally, the reliability of the trajectory correction strategy is verified by carrying out experiments on the Zhejiang University Lower Extremity Exoskeleton. The proposed trajectory correction strategy can respond to forward leaning of the upper body in a timely manner. Additionally, in the process of the center of gravity transferred from a double-support phase to a single-support phase, the ratio of gait cycle to zero moment point transfer is reduced correspondingly, and the gait stability is improved.

Key words: Lower extremity exoskeleton, Capture point, Gait phase]>

Chinese Summary  <25> 基于捕获点理论的下肢步行康复外骨骼防跌倒步态规划

摘要:研究了在下肢康复外骨骼康复训练过程中穿戴者上半身向前倾斜导致的平衡问题。通过对人体-外骨骼系统建模并使用捕获点理论获取瞬时捕获点,将稳定区域与不同步态相的瞬时捕获点比较,分析不同步态相的平衡特性以及步态过程中平衡状态的变化。基于人体骨骼系统的模型和不同阶段的平衡条件,针对穿戴者上半身前倾导致人体骨骼系统的不稳定性,提出一种轨迹校正策略。最后,在浙江大学下肢外骨骼上实验,验证轨迹校正策略的可靠性。所提轨迹校正策略可及时响应上半身前倾,同时在重心从双支撑相转移到单支撑相的过程中,步态周期与零力矩点传递的比值相应减小,步态稳定性提高。

关键词组:下肢机器人;捕获点;步态相位;人机系统平衡


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DOI:

10.1631/FITEE.1800777

CLC number:

TP242

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On-line Access:

2019-11-11

Received:

2018-12-13

Revision Accepted:

2019-07-08

Crosschecked:

2019-10-10

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