Center of mass kinematic reconstruction during steady-state walking using optimized template models.

Template models, such as the Bipedal Spring-Loaded Inverted Pendulum and the Virtual Pivot Point, have been widely used as low-dimensional representations of the complex dynamics in legged locomotion. Despite their ability to qualitatively match human walking characteristics like M-shaped ground rea...

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Main Authors: David J Kelly, Patrick M Wensing
Format: Article
Language:English
Published: Public Library of Science (PLoS) 2024-01-01
Series:PLoS ONE
Online Access:https://doi.org/10.1371/journal.pone.0313156
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author David J Kelly
Patrick M Wensing
author_facet David J Kelly
Patrick M Wensing
author_sort David J Kelly
collection DOAJ
description Template models, such as the Bipedal Spring-Loaded Inverted Pendulum and the Virtual Pivot Point, have been widely used as low-dimensional representations of the complex dynamics in legged locomotion. Despite their ability to qualitatively match human walking characteristics like M-shaped ground reaction force (GRF) profiles, they often exhibit discrepancies when compared to experimental data, notably in overestimating vertical center of mass (CoM) displacement and underestimating gait event timings (touchdown/ liftoff). This paper hypothesizes that the constant leg stiffness of these models explains the majority of these discrepancies. The study systematically investigates the impact of stiffness variations on the fidelity of model fittings to human data, where an optimization framework is employed to identify optimal leg stiffness trajectories. The study also quantifies the effects of stiffness variations on salient characteristics of human walking (GRF profiles and gait event timing). The optimization framework was applied to 24 subjects walking at 40% to 145% preferred walking speed (PWS). The findings reveal that despite only modifying ground forces in one direction, variable leg stiffness models exhibited a >80% reduction in CoM error across both the B-SLIP and VPP models, while also improving prediction of human GRF profiles. However, the accuracy of gait event timing did not consistently show improvement across all conditions. The resulting stiffness profiles mimic walking characteristics of ankle push-off during double support and reduced CoM vaulting during single support.
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spelling doaj-art-1029ef1984b6421e86fcda21b627fce02024-11-09T05:31:53ZengPublic Library of Science (PLoS)PLoS ONE1932-62032024-01-011911e031315610.1371/journal.pone.0313156Center of mass kinematic reconstruction during steady-state walking using optimized template models.David J KellyPatrick M WensingTemplate models, such as the Bipedal Spring-Loaded Inverted Pendulum and the Virtual Pivot Point, have been widely used as low-dimensional representations of the complex dynamics in legged locomotion. Despite their ability to qualitatively match human walking characteristics like M-shaped ground reaction force (GRF) profiles, they often exhibit discrepancies when compared to experimental data, notably in overestimating vertical center of mass (CoM) displacement and underestimating gait event timings (touchdown/ liftoff). This paper hypothesizes that the constant leg stiffness of these models explains the majority of these discrepancies. The study systematically investigates the impact of stiffness variations on the fidelity of model fittings to human data, where an optimization framework is employed to identify optimal leg stiffness trajectories. The study also quantifies the effects of stiffness variations on salient characteristics of human walking (GRF profiles and gait event timing). The optimization framework was applied to 24 subjects walking at 40% to 145% preferred walking speed (PWS). The findings reveal that despite only modifying ground forces in one direction, variable leg stiffness models exhibited a >80% reduction in CoM error across both the B-SLIP and VPP models, while also improving prediction of human GRF profiles. However, the accuracy of gait event timing did not consistently show improvement across all conditions. The resulting stiffness profiles mimic walking characteristics of ankle push-off during double support and reduced CoM vaulting during single support.https://doi.org/10.1371/journal.pone.0313156
spellingShingle David J Kelly
Patrick M Wensing
Center of mass kinematic reconstruction during steady-state walking using optimized template models.
PLoS ONE
title Center of mass kinematic reconstruction during steady-state walking using optimized template models.
title_full Center of mass kinematic reconstruction during steady-state walking using optimized template models.
title_fullStr Center of mass kinematic reconstruction during steady-state walking using optimized template models.
title_full_unstemmed Center of mass kinematic reconstruction during steady-state walking using optimized template models.
title_short Center of mass kinematic reconstruction during steady-state walking using optimized template models.
title_sort center of mass kinematic reconstruction during steady state walking using optimized template models
url https://doi.org/10.1371/journal.pone.0313156
work_keys_str_mv AT davidjkelly centerofmasskinematicreconstructionduringsteadystatewalkingusingoptimizedtemplatemodels
AT patrickmwensing centerofmasskinematicreconstructionduringsteadystatewalkingusingoptimizedtemplatemodels