Therapeutic Robotics Neville Hogan Sun Jae Professor of Mechanical Engineering Professor of Brain and Cognitive Sciences Massachusetts Institute of Technology Disclosure: Neville Hogan is part owner of Interactive Motion Technologies, Inc. which manufactures human-interactive technologies under license to MIT. Newman Laboratory for Biomechanics and Human Rehabilitation
29
Embed
CONTROL-RELEVANT MODELS FOR BIO-MIMETIC MATERIALS€¦ · Buerger, S.P. and Hogan, N. Complementary Stability and Loop-Shaping for Improved Human-Robot Interaction. IEEE Transactions
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Therapeutic Robotics
Neville Hogan
Sun Jae Professor of Mechanical EngineeringProfessor of Brain and Cognitive Sciences
Massachusetts Institute of Technology
Disclosure: Neville Hogan is part owner of Interactive Motion Technologies, Inc. which manufactures human-interactive technologies under license to MIT.
Newman Laboratory for Biomechanics and Human Rehabilitation
Contact Robotics
Robot apprentices/helpers
Robot big brothers/bodyguards
Robot dance partners
Robot nurses
Robot therapists
...and many more
My enduring interest: controlling physical interaction
Physical contact can make control extraordinarily difficult……but affords powerful new task strategies
Ultimate goal: Close physical cooperation
between machines & humans
Image courtesy of Prof. Kazuhiro Kosuge
Robotic Therapy
More than twice the benefit of conventional therapy alone
Fewer side effects (joint pain)
Contact and interaction are essential
Meta-Analysis Demonstrates Reliable Benefits
Kwakkel et al. (2008) “Effects of Robot-assisted therapy on upper limb recovery after stroke: A Systematic Review,”
Neurorehabilitation and Neural Repair
22(2):111-121.
Most Effective Therapy Requires Variable Impedance
Hydraulic, geared electromagnetic: high intrinsic impedance
Compressed-gas: limited by low-
frequency “parasitic”
dynamics
Feather-light touch at forces up to and beyond body weight
High force density (force/mass ratio)
Low output (driving-point) mechanical impedance
The Appeal of Force Feedback
Equation of motion:
Force feedback controller:
Resulting equation of motion:
Increasing Gf
reduces apparent inertia, friction
eaf FFxxFxm ),(
efa FGF
ef
f
f
FG
xxFGxm
1
),(1
SNAG—Coupled Instability
Performance Comparison
Best-Practice Prior Art
New Optimized Controller
Buerger, S.P. and Hogan, N. Complementary Stability and Loop-Shaping for Improved Human-Robot Interaction. IEEE Transactions on Robotics 2007 23:232-244
Goal: feather-light touch at high force
Controller instability has plagued prior approaches
Progress: new force-control strategy
Low impedance without instability
US & foreign patent applications 2006
Achieved PerformancePerformance best tested by “feel”
Static/Coulomb friction:less than 0.3 N (66x reduction)
Inertia reduction:1.75 kg with Kdc
=2000 (3.4x reduction)
1.2 kg with Kdc=3000 (5x reduction)
Performance and stability are significantly enhanced
—despite differences between model and robot.
Robotic Lifting Therapy
45 year-old right-
handed male, suffered stroke on 5/2000
Left subcortical infarct involving basal ganglia & internal capsule
Complete right hemiplegia before robotic therapy
Robotic Locomotion Therapy: Mobile Overground Prototype
Mobile robot follows patient
Overground or can “park”
at a treadmill
Platform for therapy robot modules
Body weight support (continuously variable)
Interact with pelvis to challenge and/or treat balance, weight shifting …
... and more
Main design challenge:
Variable impedance actuators
Compressible Fluids
Piston & cylinder with ideal gas, isothermal conditions
Adiabatic similar
Force varies inversely with x
Stiffness varies inversely with x2
But…
Stiffness is proportional to mass of gas, m
Abrupt stiffness change requires excessive mass flow rate
e.g. virtual wall contact is limited by choked flow
Electro-Hydraulics
High working pressure
excellent force/mass ratio
Flapper valves
Roa too small insufficient control Pa ≈
Ps
Rlb increases as Rla decreases
Low output Z requires both Rlband Rla low excessive leakage
High intrinsic output mechanical impedance
Jet-pipe valves similar
Hybrid Hydraulic Actuator
A hybrid (compromise) solution
Electro-mechanical motor
Mounted on robot base where weight is less problematic, even advantageous
SupportNational Institutes of HealthNational Science FoundationNational Institute for Disability and
Rehabilitation ResearchVeteran’s AdministrationNational Defense Sciences Education GrantSamsung FellowshipBurke Medical Research InstituteLangeloth FoundationGloria Blake Memorial FundEric P. & Evelyn E. Newman Fund