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Hybrid oscillator-based no-delay hip exoskeleton control for free walking assistance

Wei Yang (Ningbo Research Institute, Zhejiang University, Ningbo, China and School of Mechanical Engineering, Zhejiang University, Hangzhou, China)
Linghui Xu (School of Mechanical Engineering, Zhejiang University, Hangzhou, China and Ningbo Research Institute, Zhejiang University, Ningbo, China)
Linfan Yu (Ningbo Research Institute, Zhejiang University, Ningbo, China)
Yuting Chen (School of Mechanical Engineering, Yanshan University, Qinhuangdao, China and Ningbo Research Institute, Zhejiang University, Ningbo, China)
Zehao Yan (Ningbo Research Institute, Zhejiang University, Ningbo, China)
Canjun Yang (School of Mechanical Engineering, Zhejiang University, Hangzhou, China and Ningbo Research Institute, Zhejiang University, Ningbo, China)

Industrial Robot

ISSN: 0143-991x

Article publication date: 27 July 2021

Issue publication date: 16 November 2021

232

Abstract

Purpose

Walking-aid exoskeletons can assist and protect effectively the group with lower limb muscle strength decline, workers, first responders and military personnel. However, there is almost no united control strategy that can effectively assist daily walking. This paper aims to propose a hybrid oscillators’ (HOs) model to adapt to irregular gait (IG) patterns (frequent alternation between walking and standing or rapid changing of walking speed, etc.) and generate compliant and no-delay assistive torque.

Design/methodology/approach

The proposed algorithm, HOs, combines adaptive oscillators (AOs) with phase oscillator through switching assistive mode depending on whether or not the AOs' predicting error of hip joint degree is exceeded our expectation. HOs can compensate for delay by predicting gait phase when in AOs mode. Several treadmill and free walking experiments are designed to test the adaptability and effectiveness of HOs model under IG.

Findings

The experimental results show that the assistive strategy based on the HOs is effective under IG patterns, and delay is compensated totally under quasiperiodic gait conditions where a smoother human–robot interaction (HRI) force and the reduction of HRI force peak are observed. Delay compensation is found very effective at improving the performance of the assistive exoskeleton.

Originality/value

A novel algorithm is proposed to improve the adaptability of a walking assist hip exoskeleton in daily walking as well as generate compliant, no-delay assistive torque when converging.

Keywords

Acknowledgements

This research is supported by National Natural Science Foundation of China (Grant No. 51805469), Zhejiang Basic Public Welfare Research Plan (Grant No. LY21E050020) and Ningbo Science and Technology Innovation 2025 Project (Grant No. 2020Z022).

Citation

Yang, W., Xu, L., Yu, L., Chen, Y., Yan, Z. and Yang, C. (2021), "Hybrid oscillator-based no-delay hip exoskeleton control for free walking assistance", Industrial Robot, Vol. 48 No. 6, pp. 906-914. https://doi.org/10.1108/IR-02-2021-0038

Publisher

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Emerald Publishing Limited

Copyright © 2021, Emerald Publishing Limited

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