Design and Experimental Verification of a Quasi-Passive Variable Stiffness Ankle Exoskeleton for Human Walking Assistance
Jinlu Wang, Qingcong Wu, Yiqi Zou, Yanghui Zhu, Hongtao Wang, Hongtao Wu
Abstract
Exoskeleton robots are an effective method for enhancing human walking ability. This paper introduces a quasi-passive variable stiffness ankle exoskeleton, which absorbs negative work produced during ankle dorsiflexion in the stance phase of the gait cycle and releases energy to assist plantar flexion during push-off. Compared to powered exoskeletons, this design does not require high-power actuators but instead relies on a clutch and elastic component to mimic the interaction between muscles and tendons for assistance. Compared to passive exoskeletons, the designed clutch can adapt to different users. Compared to fixed-stiffness exoskeletons, the novel variable stiffness energy storage mechanism passively adjusts stiffness to mimic the biomechanical properties of the ankle joint. The proposed exoskeleton identifies gait phases based on a control strategy using foot force sensors. This strategy controls the exoskeleton's energy recovery and release by determining the gait cycle phase and changing the clutch state. Finally, a level-ground walking experiment was conducted with six healthy participants. Results showed that wearing the exoskeleton reduced the root mean square (RMS) change rate of soleus EMG activity by 7.25% and decreased the net metabolic rate during walking by 3.6%.
BibTeX
@inproceedings{ral2025_designandexperim,
title = {Design and Experimental Verification of a Quasi-Passive Variable Stiffness Ankle Exoskeleton for Human Walking Assistance},
author = {Jinlu Wang and Qingcong Wu and Yiqi Zou and Yanghui Zhu and Hongtao Wang and Hongtao Wu},
booktitle = {RA-L 2025},
year = {2025}
}