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Steve CollinsAssociate ProfessorMechanical EngineeringStanford University
Designing exoskeletons and prosthetic limbs
that enhance human performance
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins [email protected] 2/34
First: A difficult design problem.
Then: Tools that help.
Finally: Energy-efficient embodiments.
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins [email protected] 3/34
Goal: Restore and enhance mobility
[Daily Herald (2013)] [Duncan et al. (2007)] [V. Lockett (2016)] [UNICEF (2016)]
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[Yagn (1890); Seireg (1971); Zoss et al. (2006) ; van Dijk et al. (2011)]
Challenge: Improving performance is hard
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Best results: Modest improvements
[MIT] [Harvard] [Ghent] [NCSU/CMU]
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Problem: What should the device do?Intuition (only) inspiresPresent models don’t predict
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Solutions:
Universal Device EmulatorsExperiments on humans, fast.
Human-in-the-Loop OptimizationDiscover, individualize and co-adapt.
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins [email protected] 8/34
prosthesis
motor
Emulators: Fast, cheap and in control
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins [email protected] 9/34
…
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End effectors: Easy to get good performance
[Caputo & Collins (2014) JBME; Collins et al. (2015) ICRA; Witte et al. (2017) ICORR]
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HLO: Discover. Customize. Adapt.
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Big idea: Human-In-the-Loop Optimization
[Zhang et al. (2017) Science]
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Specific method: Minimize metabolic rate
[Zhang et al. (2017) Science]
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Application: Ankle torque pattern
[Zhang et al. (2017) Science]
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Application: Exoskeleton on one ankle
[Zhang et al. (2017) Science]
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Metabolic cost: Exceptionally large reduction
[Zhang et al. (2017) Science]
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Optimized settings: Substantial variation
[Zhang et al. (2017) Science]
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Static comparison: Suggests three contributors
[Zhang et al. (2017) Science]
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Static comparison: Facilitating motor learning
[Jackson & Collins (2015) J. Appl. Physiol.; Zhang et al. (2017) Science]
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19.3%reduced
*
[Jackson & Collins (2015) J. Appl. Physiol.; Zhang et al. (2017) Science]
Static comparison: Facilitating motor learning
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Video here
[Zhang et al. in press]
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Single-subject studies: Test generality
[Zhang et al. (2017) Science]
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[Zhang et al. (2017) Science]
Single-subject studies: Test generality
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Implications: Great tools for design.
Future work: Faster learning + optimization
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Questions?
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Going mobile: Efficient assistive robotics
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Bioinspiration: Ankle catapult mechanism
Ultrasound imaging: Calf muscles nearly static
[Ishikawa et. al. (2005) J Appl Physiol][Farris et. al. (2013) J Appl Physiol]
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Device: Unpowered ankle exoskeleton
[Collins et al. (2015) Nature]
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Results: Reduced force more efficient walking
[Collins et al. (2015) Nature]
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Limitation: Controllability
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Actuator design: Electroadhesive clutch
[Diller et al. (2016) ICRA]
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Results: Electroadhesive clutch characteristics
One clutch pair:Peak force: 200 NMass: 1.5 gPower used: 0.3 mWApplied Voltage: 300 VSwitching time: 0.01 s
Demonstration system:Mass: 26 gEfficiency: 95%Fatigue life: > 2,000,000
[Diller et al. (2016) ICRA]
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Future work: Energy-recycling actuators
High-bandwidth, discretely-variable force control
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Thank you:
Sponsors:
PieterFiers
RachelJackson
KatherinePoggensee
KirbyWitte
JuanjuanZhang
ChristopherAtkeson
StuartDiller
GregSawicki