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浙江大学学报(工学版)
Journal of ZheJiang University (Engineering Science)  2024, Vol. 58 Issue (4): 772-778    DOI: 10.3785/j.issn.1008-973X.2024.04.012
    
Ankle flexible exoskeleton based on force feedback admittance control
Dong CHEN(),Weida LI*(),Hongmiao ZHANG,Juan LI
1. School of Mechanical and Electric Engineering, Jiangsu Provincial Key Laboratory of Advanced Robotics, Soochow University, Suzhou 215021, China
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Abstract  

In response to the need for ankle rehabilitation training, a lightweight, easy-to-wear flexible ankle exoskeleton robot was designed using modular drive units and Bowden cables through analysis of ankle joint mechanics. The robot can provide assistance for ankle plantarflexion/dorsiflexion and inversion/eversion movements. Position control and torque control are used for flexible exoskeleton during the dorsiflexion and plantarflexion stages, respectively. Position control is mainly based on traditional proportional integral derivative(PID), while torque control uses force as a feedback signal to establish an admittance model between the interaction force difference and the Bowden cable core displacement compensation. The admittance parameters are dynamically adjusted through the Sigmoid deformation function to meet the requirements of assistive torque output and human-machine interaction compliance. Experimental data showed that the position tracking error was stable within 0.46 cm, and the force output error was stable within ?1.5-1.5 N, meeting the needs of human rehabilitation training.

Key words： ankle joint      rehabilitation training      flexible exoskeleton      force feedback      admittance control     
Received: 13 April 2023      Published: 27 March 2024
CLC:  TP 242  
Corresponding Authors: Weida LI     E-mail: mini1624365292@outlook.com;hit_liweida@163.com
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Dong CHEN
Weida LI
Hongmiao ZHANG
Juan LI
Cite this article:

Dong CHEN,Weida LI,Hongmiao ZHANG,Juan LI. Ankle flexible exoskeleton based on force feedback admittance control. Journal of ZheJiang University (Engineering Science), 2024, 58(4): 772-778.

URL:

https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2024.04.012     OR     https://www.zjujournals.com/eng/Y2024/V58/I4/772


基于力反馈导纳控制的踝关节柔性外骨骼

针对踝关节康复训练的需求，分析踝关节的运动机理，运用模块化驱动单元与鲍登线，设计轻量化、易穿戴的柔性踝关节外骨骼机器人，实现踝关节跖屈/背屈、内/外翻的运动辅助. 柔性外骨骼在背屈和跖屈阶段分别采用位置控制和力矩控制. 位置控制以传统PID为主；力矩控制以力为反馈信号，建立交互力差值与鲍登线内芯位移补偿之间的导纳模型. 通过Sigmoid变形函数实现导纳参数的动态调控，满足辅助力矩输出和人机交互柔顺性的需求. 实验结果表明，位置跟踪误差不超过0.46 cm，力输出误差为?1.5~1.5 N，能够满足人体康复训练的需求.


关键词： 踝关节,  康复训练,  柔性外骨骼,  力反馈,  导纳控制 
Fig.1 Basic movement types of human ankle joint
Fig.2 Human joint torque analysis
Fig.3 Aid mechanism for plantar flexion movement
Fig.4 Aid mechanism for valgus and dorsiflexion movement
Fig.5 Composition of rope drive unit
Fig.6 Overall display of exoskeleton prototype
Fig.7 Diagram of robot coordinate system and kinematic analysis
Fig.8 Diagram of Bowden cable tension and displacement model
Fig.9 Bowdoen cable output force and displacement curves
Fig.10 Bowden cable offset compensation
Fig.11 Admittance control block diagram based on force feedback
Fig.12 Adaptive curve of admittance parameter
Fig.13 Treadmill walking experiment
Fig.14 Curve of core displacement over time
Fig.15 Force variation curve during plantar flexion
Fig.16 Core displacement curve during back
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