Optimized hip–knee–ankle exoskeleton assistance at a range of walking speeds
Abstract Background Autonomous exoskeletons will need to be useful at a variety of walking speeds, but it is unclear how optimal hip–knee–ankle exoskeleton assistance should change with speed. Biological joint moments tend to increase with speed, and in some cases, optimized ankle exoskeleton torque...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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BMC
2021-10-01
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| Series: | Journal of NeuroEngineering and Rehabilitation |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s12984-021-00943-y |
| _version_ | 1818651734465052672 |
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| author | Gwendolyn M. Bryan Patrick W. Franks Seungmoon Song Alexandra S. Voloshina Ricardo Reyes Meghan P. O’Donovan Karen N. Gregorczyk Steven H. Collins |
| author_facet | Gwendolyn M. Bryan Patrick W. Franks Seungmoon Song Alexandra S. Voloshina Ricardo Reyes Meghan P. O’Donovan Karen N. Gregorczyk Steven H. Collins |
| author_sort | Gwendolyn M. Bryan |
| collection | DOAJ |
| description | Abstract Background Autonomous exoskeletons will need to be useful at a variety of walking speeds, but it is unclear how optimal hip–knee–ankle exoskeleton assistance should change with speed. Biological joint moments tend to increase with speed, and in some cases, optimized ankle exoskeleton torques follow a similar trend. Ideal hip–knee–ankle exoskeleton torque may also increase with speed. The purpose of this study was to characterize the relationship between walking speed, optimal hip–knee–ankle exoskeleton assistance, and the benefits to metabolic energy cost. Methods We optimized hip–knee–ankle exoskeleton assistance to reduce metabolic cost for three able-bodied participants walking at 1.0 m/s, 1.25 m/s and 1.5 m/s. We measured metabolic cost, muscle activity, exoskeleton assistance and kinematics. We performed Friedman’s tests to analyze trends across walking speeds and paired t-tests to determine if changes from the unassisted conditions to the assisted conditions were significant. Results Exoskeleton assistance reduced the metabolic cost of walking compared to wearing the exoskeleton with no torque applied by 26%, 47% and 50% at 1.0, 1.25 and 1.5 m/s, respectively. For all three participants, optimized exoskeleton ankle torque was the smallest for slow walking, while hip and knee torque changed slightly with speed in ways that varied across participants. Total applied positive power increased with speed for all three participants, largely due to increased joint velocities, which consistently increased with speed. Conclusions Exoskeleton assistance is effective at a range of speeds and is most effective at medium and fast walking speeds. Exoskeleton assistance was less effective for slow walking, which may explain the limited success in reducing metabolic cost for patient populations through exoskeleton assistance. Exoskeleton designers may have more success when targeting activities and groups with faster walking speeds. Speed-related changes in optimized exoskeleton assistance varied by participant, indicating either the benefit of participant-specific tuning or that a wide variety of torque profiles are similarly effective. |
| first_indexed | 2024-12-17T02:10:49Z |
| format | Article |
| id | doaj.art-bf1685b705ae4506b118349c8fd55a97 |
| institution | Directory Open Access Journal |
| issn | 1743-0003 |
| language | English |
| last_indexed | 2024-12-17T02:10:49Z |
| publishDate | 2021-10-01 |
| publisher | BMC |
| record_format | Article |
| series | Journal of NeuroEngineering and Rehabilitation |
| spelling | doaj.art-bf1685b705ae4506b118349c8fd55a972022-12-21T22:07:34ZengBMCJournal of NeuroEngineering and Rehabilitation1743-00032021-10-0118111210.1186/s12984-021-00943-yOptimized hip–knee–ankle exoskeleton assistance at a range of walking speedsGwendolyn M. Bryan0Patrick W. Franks1Seungmoon Song2Alexandra S. Voloshina3Ricardo Reyes4Meghan P. O’Donovan5Karen N. Gregorczyk6Steven H. Collins7Department of Mechanical Engineering, Stanford UniversityDepartment of Mechanical Engineering, Stanford UniversityDepartment of Mechanical Engineering, Stanford UniversityMechanical and Aerospace Engineering, University of CaliforniaDepartment of Mechanical Engineering, Stanford UniversityU.S. Army Natick Soldier Research, Development and Engineering CenterU.S. Army Natick Soldier Research, Development and Engineering CenterDepartment of Mechanical Engineering, Stanford UniversityAbstract Background Autonomous exoskeletons will need to be useful at a variety of walking speeds, but it is unclear how optimal hip–knee–ankle exoskeleton assistance should change with speed. Biological joint moments tend to increase with speed, and in some cases, optimized ankle exoskeleton torques follow a similar trend. Ideal hip–knee–ankle exoskeleton torque may also increase with speed. The purpose of this study was to characterize the relationship between walking speed, optimal hip–knee–ankle exoskeleton assistance, and the benefits to metabolic energy cost. Methods We optimized hip–knee–ankle exoskeleton assistance to reduce metabolic cost for three able-bodied participants walking at 1.0 m/s, 1.25 m/s and 1.5 m/s. We measured metabolic cost, muscle activity, exoskeleton assistance and kinematics. We performed Friedman’s tests to analyze trends across walking speeds and paired t-tests to determine if changes from the unassisted conditions to the assisted conditions were significant. Results Exoskeleton assistance reduced the metabolic cost of walking compared to wearing the exoskeleton with no torque applied by 26%, 47% and 50% at 1.0, 1.25 and 1.5 m/s, respectively. For all three participants, optimized exoskeleton ankle torque was the smallest for slow walking, while hip and knee torque changed slightly with speed in ways that varied across participants. Total applied positive power increased with speed for all three participants, largely due to increased joint velocities, which consistently increased with speed. Conclusions Exoskeleton assistance is effective at a range of speeds and is most effective at medium and fast walking speeds. Exoskeleton assistance was less effective for slow walking, which may explain the limited success in reducing metabolic cost for patient populations through exoskeleton assistance. Exoskeleton designers may have more success when targeting activities and groups with faster walking speeds. Speed-related changes in optimized exoskeleton assistance varied by participant, indicating either the benefit of participant-specific tuning or that a wide variety of torque profiles are similarly effective.https://doi.org/10.1186/s12984-021-00943-yExoskeletonAugmentationWalking speedHuman-in-the-loop optimization |
| spellingShingle | Gwendolyn M. Bryan Patrick W. Franks Seungmoon Song Alexandra S. Voloshina Ricardo Reyes Meghan P. O’Donovan Karen N. Gregorczyk Steven H. Collins Optimized hip–knee–ankle exoskeleton assistance at a range of walking speeds Journal of NeuroEngineering and Rehabilitation Exoskeleton Augmentation Walking speed Human-in-the-loop optimization |
| title | Optimized hip–knee–ankle exoskeleton assistance at a range of walking speeds |
| title_full | Optimized hip–knee–ankle exoskeleton assistance at a range of walking speeds |
| title_fullStr | Optimized hip–knee–ankle exoskeleton assistance at a range of walking speeds |
| title_full_unstemmed | Optimized hip–knee–ankle exoskeleton assistance at a range of walking speeds |
| title_short | Optimized hip–knee–ankle exoskeleton assistance at a range of walking speeds |
| title_sort | optimized hip knee ankle exoskeleton assistance at a range of walking speeds |
| topic | Exoskeleton Augmentation Walking speed Human-in-the-loop optimization |
| url | https://doi.org/10.1186/s12984-021-00943-y |
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