Design of a Passive Gait-based Ankle-foot Exoskeleton with Self-adaptive Capability

Xiangyang Wang,Bojian Qu,Haibo Qu,Sheng Guo,Majun Song

doi:10.1186/s10033-020-00465-z

Abstract

Propulsion during push-off is the key to realizing human locomotion. Humans have evolved a way of walking with high energy utilization, but it can be further improved. Drawing inspiration from the muscle-tendon unit, a passive spring-actuated ankle-foot exoskeleton is designed to assist with human walking and to lengthen walking duration by mechanically enhancing walking efficiency. Detection of the gait events is realized using a smart clutch, which is designed to detect the contact states between the shoe sole and the ground, and automatically switch its working state. The engagement of a suspended spring behind the human calf muscles is hence controlled and is in synchrony with gait. The device is completely passive and contains no external power source. Energy is stored and returned passively using the clutch. In our walking trials, the soleus electromyography activity is reduced by as much as 72.2% when the proposed ankle-foot exoskeleton is worn on the human body. The influence of the exoskeleton on walking habits is also studied. The results show the potential use of the exoskeleton in humans’ daily life.

Highlights

Legs are important for locomotive ability, and enable us to move and travel in our daily life
The device is intended to address the problem of time-delay, and perform the function of automatic state-switching based on mechanical identification of the current gait stages
With the help of the motion capture system, we examined the potential influence of the passive ankle-foot exoskeleton (PAFE) on human walking habits

Summary

Introduction

Legs are important for locomotive ability, and enable us to move and travel in our daily life. Enduring walking and lower energy costs can significantly expand the range of human activities. In some rough terrains, walking is the only option because wheeled vehicles are unable to transport people. Improved walking economy is beneficial to everyone. The walking behavior of humans is well-tuned under natural selection [1], there is still room for improvement, especially when exoskeleton devices are developed and enter into service. Since half of the required mechanical power output is generated by the ankle during push-off [2], the ankle-foot exoskeleton has been extensively studied over the past two decades. Many powered and unpowered devices have been proposed to assist in the push-off process, reducing the energy cost to the human body [3].

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Conclusion