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bioRxiv · 10.1101/2020.03.24.005389

From a biological template model to gait assistance with an exosuit

Firouzi, V.·Davoodi, A.·Bahrami, F.·Ahmad Sharbafi, M.
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Abstract

By invention of soft wearable assistive devices, known as exosuits, a new aspect in assisting unimpaired subjects is introduced. In this study, we designed and developed an exosuit with compliant biarticular thigh actuators, called BAExo. Unlike common method of using rigid actuators in exosuits, the BAExo is made of serial elastic actuators (SEA) resembling artificial muscles (AM). This bioinsipred design is complemented by the novel control concept of using the ground reaction force to adjust these AMs stiffness in the stance phase. By locking the motors in the swing phase the SEAs will be simplified to passive biarticular springs, which is sufficient for leg swinging. The key concept in our design and control approach is synthesizing human locomotion to develop assistive device, instead of copying the outputs of human motor control. Analysing human walking assistance using an experiment-based OpenSim model demonstrates the advantages of the proposed design and control of BAExo, regarding metabolic cost reduction and efficiency of the system. In addition, pilot experiments with the recently developed BAExo hardware support the applicability of the introduced method. Author summaryAging and mobility of elderly people are of crucial concern in developed countries. The U.S. Census Bureau reports that by the middle of the 21st century, about 80 million Americans will be 65 or older. According to the groups research, medical costs resulting from falls by the elderly are expected to approach $32.4 billion by 2020. Therefore, assistance of elderly people and making the assistive devices more intelligent is a need in near future. However, this is not the only application of assistive devices. Exosuits, as soft wearable robots, introduced a new aspect in assisting a large range of population, even healthy young people. We introduce a novel design and control method for a new exosuit. As the research in the field of wearable assistive devices is growing in recent years and its application in daily life becomes more evident for the society, such studies with a unique view in design and control could have a significant impact. Our proposed biologically inspired approach could be potentially applied to other exosuits.

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Firouzi, V., Davoodi, A., Bahrami, F., Ahmad Sharbafi, M.. 2020-03-24. From a biological template model to gait assistance with an exosuit. https://doi.org/10.1101/2020.03.24.005389

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