designing exoskeletons and prosthetic limbs that enhance
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Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 1/34
Steve CollinsAssociate ProfessorMechanical EngineeringStanford University
Designing exoskeletons and prosthetic limbs
that enhance human performance
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 2/34
First: A difficult design problem.
Then: Tools that help.
Finally: Energy-efficient embodiments.
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 3/34
Goal: Restore and enhance mobility
[Daily Herald (2013)] [Duncan et al. (2007)] [V. Lockett (2016)] [UNICEF (2016)]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 4/34
[Yagn (1890); Seireg (1971); Zoss et al. (2006) ; van Dijk et al. (2011)]
Challenge: Improving performance is hard
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 5/34
Best results: Modest improvements
[MIT] [Harvard] [Ghent] [NCSU/CMU]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 6/34
Problem: What should the device do?Intuition (only) inspiresPresent models don’t predict
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 7/34
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 stevecollins@stanford.edu 8/34
prosthesis
motor
Emulators: Fast, cheap and in control
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 9/34
…
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 10/34
End effectors: Easy to get good performance
[Caputo & Collins (2014) JBME; Collins et al. (2015) ICRA; Witte et al. (2017) ICORR]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 11/34
HLO: Discover. Customize. Adapt.
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 12/34
Big idea: Human-In-the-Loop Optimization
[Zhang et al. (2017) Science]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 13/34
Specific method: Minimize metabolic rate
[Zhang et al. (2017) Science]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 14/34
Application: Ankle torque pattern
[Zhang et al. (2017) Science]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 15/34
Application: Exoskeleton on one ankle
[Zhang et al. (2017) Science]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 16/34
Metabolic cost: Exceptionally large reduction
[Zhang et al. (2017) Science]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 17/34
Optimized settings: Substantial variation
[Zhang et al. (2017) Science]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 18/34
Static comparison: Suggests three contributors
[Zhang et al. (2017) Science]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 19/34
Static comparison: Facilitating motor learning
[Jackson & Collins (2015) J. Appl. Physiol.; Zhang et al. (2017) Science]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 20/34
19.3%reduced
*
[Jackson & Collins (2015) J. Appl. Physiol.; Zhang et al. (2017) Science]
Static comparison: Facilitating motor learning
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 21/34
Video here
[Zhang et al. in press]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 22/34
Single-subject studies: Test generality
[Zhang et al. (2017) Science]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 23/34
[Zhang et al. (2017) Science]
Single-subject studies: Test generality
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 24/34
Implications: Great tools for design.
Future work: Faster learning + optimization
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 25/34
Questions?
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 26/34
Going mobile: Efficient assistive robotics
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 27/34
Bioinspiration: Ankle catapult mechanism
Ultrasound imaging: Calf muscles nearly static
[Ishikawa et. al. (2005) J Appl Physiol][Farris et. al. (2013) J Appl Physiol]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 28/34
Device: Unpowered ankle exoskeleton
[Collins et al. (2015) Nature]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 29/34
Results: Reduced force more efficient walking
[Collins et al. (2015) Nature]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 30/34
Limitation: Controllability
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 31/34
Actuator design: Electroadhesive clutch
[Diller et al. (2016) ICRA]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 32/34
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]
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 33/34
Future work: Energy-recycling actuators
High-bandwidth, discretely-variable force control
Steve Collins Stanford University biomechatronics.cit.cmu.edu @StevenHCollins stevecollins@stanford.edu 34/34
Thank you:
Sponsors:
PieterFiers
RachelJackson
KatherinePoggensee
KirbyWitte
JuanjuanZhang
ChristopherAtkeson
StuartDiller
GregSawicki
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