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Learning to walk with an adaptive gain proportional myoelectric controller for a robotic ankle exoskeleton

Overview of attention for article published in Journal of NeuroEngineering and Rehabilitation, November 2015
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Title
Learning to walk with an adaptive gain proportional myoelectric controller for a robotic ankle exoskeleton
Published in
Journal of NeuroEngineering and Rehabilitation, November 2015
DOI 10.1186/s12984-015-0086-5
Pubmed ID
Authors

Jeffrey R. Koller, Daniel A. Jacobs, Daniel P. Ferris, C. David Remy

Abstract

Robotic ankle exoskeletons can provide assistance to users and reduce metabolic power during walking. Our research group has investigated the use of proportional myoelectric control for controlling robotic ankle exoskeletons. Previously, these controllers have relied on a constant gain to map user's muscle activity to actuation control signals. A constant gain may act as a constraint on the user, so we designed a controller that dynamically adapts the gain to the user's myoelectric amplitude. We hypothesized that an adaptive gain proportional myoelectric controller would reduce metabolic energy expenditure compared to walking with the ankle exoskeleton unpowered because users could choose their preferred control gain. We tested eight healthy subjects walking with the adaptive gain proportional myoelectric controller with bilateral ankle exoskeletons. The adaptive gain was updated each stride such that on average the user's peak muscle activity was mapped to maximal power output of the exoskeleton. All subjects participated in three identical training sessions where they walked on a treadmill for 50 minutes (30 minutes of which the exoskeleton was powered) at 1.2 ms(-1). We calculated and analyzed metabolic energy consumption, muscle recruitment, inverse kinematics, inverse dynamics, and exoskeleton mechanics. Using our controller, subjects achieved a metabolic reduction similar to that seen in previous work in about a third of the training time. The resulting controller gain was lower than that seen in previous work (β=1.50±0.14 versus a constant β=2). The adapted gain allowed users more total ankle joint power than that of unassisted walking, increasing ankle power in exchange for a decrease in hip power. Our findings indicate that humans prefer to walk with greater ankle mechanical power output than their unassisted gait when provided with an ankle exoskeleton using an adaptive controller. This suggests that robotic assistance from an exoskeleton can allow humans to adopt gait patterns different from their normal choices for locomotion. In our specific experiment, subjects increased ankle power and decreased hip power to walk with a reduction in metabolic cost. Future exoskeleton devices that rely on proportional myolectric control are likely to demonstrate improved performance by including an adaptive gain.

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Mendeley readers

Mendeley readers

The data shown below were compiled from readership statistics for 249 Mendeley readers of this research output. Click here to see the associated Mendeley record.

Geographical breakdown

Country Count As %
Germany 2 <1%
United States 1 <1%
Belgium 1 <1%
Unknown 245 98%

Demographic breakdown

Readers by professional status Count As %
Student > Ph. D. Student 62 25%
Student > Master 33 13%
Researcher 22 9%
Professor > Associate Professor 20 8%
Student > Bachelor 19 8%
Other 41 16%
Unknown 52 21%
Readers by discipline Count As %
Engineering 124 50%
Medicine and Dentistry 14 6%
Sports and Recreations 14 6%
Neuroscience 7 3%
Computer Science 5 2%
Other 22 9%
Unknown 63 25%
Attention Score in Context

Attention Score in Context

This research output has an Altmetric Attention Score of 1. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 06 November 2015.
All research outputs
#20,295,501
of 22,832,057 outputs
Outputs from Journal of NeuroEngineering and Rehabilitation
#1,137
of 1,279 outputs
Outputs of similar age
#239,103
of 285,322 outputs
Outputs of similar age from Journal of NeuroEngineering and Rehabilitation
#16
of 18 outputs
Altmetric has tracked 22,832,057 research outputs across all sources so far. This one is in the 1st percentile – i.e., 1% of other outputs scored the same or lower than it.
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We're also able to compare this research output to 18 others from the same source and published within six weeks on either side of this one. This one is in the 1st percentile – i.e., 1% of its contemporaries scored the same or lower than it.