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Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: A simulation study

Assistive exoskeletons can reduce the metabolic cost of walking, and recent advances in exoskeleton device design and control have resulted in large metabolic savings. Most exoskeleton devices provide assistance at either the ankle or hip. Exoskeletons that assist multiple joints have the potential...

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Autores principales: Bianco, Nicholas A., Franks, Patrick W., Hicks, Jennifer L., Delp, Scott L.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8730392/
https://www.ncbi.nlm.nih.gov/pubmed/34986191
http://dx.doi.org/10.1371/journal.pone.0261318
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author Bianco, Nicholas A.
Franks, Patrick W.
Hicks, Jennifer L.
Delp, Scott L.
author_facet Bianco, Nicholas A.
Franks, Patrick W.
Hicks, Jennifer L.
Delp, Scott L.
author_sort Bianco, Nicholas A.
collection PubMed
description Assistive exoskeletons can reduce the metabolic cost of walking, and recent advances in exoskeleton device design and control have resulted in large metabolic savings. Most exoskeleton devices provide assistance at either the ankle or hip. Exoskeletons that assist multiple joints have the potential to provide greater metabolic savings, but can require many actuators and complicated controllers, making it difficult to design effective assistance. Coupled assistance, when two or more joints are assisted using one actuator or control signal, could reduce control dimensionality while retaining metabolic benefits. However, it is unknown which combinations of assisted joints are most promising and if there are negative consequences associated with coupled assistance. Since designing assistance with human experiments is expensive and time-consuming, we used musculoskeletal simulation to evaluate metabolic savings from multi-joint assistance and identify promising joint combinations. We generated 2D muscle-driven simulations of walking while simultaneously optimizing control strategies for simulated lower-limb exoskeleton assistive devices to minimize metabolic cost. Each device provided assistance either at a single joint or at multiple joints using massless, ideal actuators. To assess if control could be simplified for multi-joint exoskeletons, we simulated different control strategies in which the torque provided at each joint was either controlled independently or coupled between joints. We compared the predicted optimal torque profiles and changes in muscle and total metabolic power consumption across the single joint and multi-joint assistance strategies. We found multi-joint devices–whether independent or coupled–provided 50% greater metabolic savings than single joint devices. The coupled multi-joint devices were able to achieve most of the metabolic savings produced by independently-controlled multi-joint devices. Our results indicate that device designers could simplify multi-joint exoskeleton designs by reducing the number of torque control parameters through coupling, while still maintaining large reductions in metabolic cost.
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spelling pubmed-87303922022-01-06 Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: A simulation study Bianco, Nicholas A. Franks, Patrick W. Hicks, Jennifer L. Delp, Scott L. PLoS One Research Article Assistive exoskeletons can reduce the metabolic cost of walking, and recent advances in exoskeleton device design and control have resulted in large metabolic savings. Most exoskeleton devices provide assistance at either the ankle or hip. Exoskeletons that assist multiple joints have the potential to provide greater metabolic savings, but can require many actuators and complicated controllers, making it difficult to design effective assistance. Coupled assistance, when two or more joints are assisted using one actuator or control signal, could reduce control dimensionality while retaining metabolic benefits. However, it is unknown which combinations of assisted joints are most promising and if there are negative consequences associated with coupled assistance. Since designing assistance with human experiments is expensive and time-consuming, we used musculoskeletal simulation to evaluate metabolic savings from multi-joint assistance and identify promising joint combinations. We generated 2D muscle-driven simulations of walking while simultaneously optimizing control strategies for simulated lower-limb exoskeleton assistive devices to minimize metabolic cost. Each device provided assistance either at a single joint or at multiple joints using massless, ideal actuators. To assess if control could be simplified for multi-joint exoskeletons, we simulated different control strategies in which the torque provided at each joint was either controlled independently or coupled between joints. We compared the predicted optimal torque profiles and changes in muscle and total metabolic power consumption across the single joint and multi-joint assistance strategies. We found multi-joint devices–whether independent or coupled–provided 50% greater metabolic savings than single joint devices. The coupled multi-joint devices were able to achieve most of the metabolic savings produced by independently-controlled multi-joint devices. Our results indicate that device designers could simplify multi-joint exoskeleton designs by reducing the number of torque control parameters through coupling, while still maintaining large reductions in metabolic cost. Public Library of Science 2022-01-05 /pmc/articles/PMC8730392/ /pubmed/34986191 http://dx.doi.org/10.1371/journal.pone.0261318 Text en © 2022 Bianco et al https://creativecommons.org/licenses/by/4.0/This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Bianco, Nicholas A.
Franks, Patrick W.
Hicks, Jennifer L.
Delp, Scott L.
Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: A simulation study
title Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: A simulation study
title_full Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: A simulation study
title_fullStr Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: A simulation study
title_full_unstemmed Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: A simulation study
title_short Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: A simulation study
title_sort coupled exoskeleton assistance simplifies control and maintains metabolic benefits: a simulation study
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8730392/
https://www.ncbi.nlm.nih.gov/pubmed/34986191
http://dx.doi.org/10.1371/journal.pone.0261318
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