Advance Rehabilitation Technology
William DurfeeDepartment of Mechanical Engineering
University of MinnesotaMinneapolis, USA
Including a few case studies
• Stimulated Muscles = Power • Brace = Trajectory guidance • Brake = Control, stability
HUMAN/MACHINE DESIGN LABDepartment of Mechanical Engineering
University of Minnesota(www.me.umn.edu/labs/hmd/)
Fu
x,vT
X
�
�
PE Force-Velocity
CE Force-Velocity
Fscale
IRC
CE Force-Length
Activation Dynamics (2nd order)
PE Force-Length
u
V
X
V
X
Force
Passive Element
Active Element
Muscle mechanics
Smart orthotics + electrical stimulation for gait restorationHaptic interfaces for virtual product
prototyping, smart knobs for cars
Rehabilitation engineering-Tele-rehabilitation-Stroke rehab-Driving simulators
Human assist machines-Compact power sources-Powered exoskeletons-Natural control
Medical device design-Evaluation of surgical tools
Rehabilitation Engineering
The application of engineering principles to treatment, services and devices related to people with disabilities
Disability
“A physical or mental impairment that substantially limits one or more major life activities.”
Americans with Disabilities Act, 1990
20-49 million in U.S.
6.5% of GDP
12.6% of population
MEDICAL MODEL
StrokeSCIMS
Muscular Dystrophy
ArthritisAmputationAlzheimer’s
Medical Condition Cognitive•Sensory/Motor integration•Memory•Reasoning
Physical
Motor
Sensory
•Speech•Balance•Gait•Coordination•Grip•Arm
•Sight•Sound
Impairment
SOCIALMODEL
PERSON
ABILITYENVIRONMENT
Therapeutic Technology
Any equipment that treats an impairment
www.empi.com
www.donjoy.com
Assistive Technology
Any equipment that increases ability or function
USER TASK
AT DEVICE
1
2
Person
Motor
Sensory
Cmd & Control
Hearing Sight
MobilityGrip
Arm•Wheelchair•Surgery•FES•Prosthesis•Orthosis
•Hearing aid•Cochlear implant•Signing
•Reading machine•Refreshable Braille•Glasses•Mobility
•ECU•Computer•Communic.•Robot•Speech•Driving
bionics.ossur.de
www.abledata.com
www.abledata.com
www.dekaresearch.com
www.ric.org
www.technologyreview.com
Photos from Paraplegia News and Sports ‘n Spokes
IT'S MORE THAN THE TECHNOLOGY
30-50% of AT devices are abandoned
HOT TECHNOLOGIES• Stroke rehabilitation
– Rehab robots– Constraint Induced Movement Therapy– Game therapies
• Prosthetics– War injuries– Diabetics
• Activity monitoring– Alzheimer's
• Brain-computer interfaces• Wheelchair technology• Retinal implants• Cochlear implants
Stroke
• 5.8 million (2.6% of population)• 780,000 new per year• Third leading cause of death
–150,000 per year
• #1 cause of adult disability
American Stroke Association
Rehab Treatment Robots
MIT Manus
Prosthetics
• DARPA Revolutionizing Prosthetics– 2005 –2009 (?)– $30.4 million– Johns Hopkins APL prime
contractor– Arm design, control, HMI
www.darpa.mil
Deka Arm
Manchester Union Leader IEEE Spectrum
Brain-computer interface
Braingate cortical implant system
EEG based, Bin He, UMN
iBOT Mobility, Independence Technology (Johnson & Johnson)
ibotnow.com
Retinal Implant
Argus II Retinal Implant System, University of Southern California artificialretina.energy.gov
TELEREHABILITATION
"Telerehabilitation is the clinical application of consultative, preventative, diagnostic, and therapeutic services via two-way interactive telecommunication technology."
American Association of Occupational Therapists Position Paper on Telerehabilitation
7 hrs
Why tele?
• Clients in rural locations• Clients in urban locations, but have
transportation challenges–No car–Poor public transportation
• Eliminates transportation time
HOME-BASED STROKE
REHABILITATION
Collaborators: James Carey, Samantha Weinstein, Ela Bhatt, Ashima NagpalFunding: NIDRR, H133G020145
Post-Stroke Rehab
• Constraint-Induced Movement Therapy
• Robot Therapy
• Virtual Reality
• Wii
• Motion Biofeedback Therapy
Goal: Create new brain pathways to compensate for injured tissue
Use the afflicted limb while concentratingW. J. Chu et. al, Stroke, 2002; D. M. Feeney and J. C. Baron, Stroke, 1986; R. A. Schmidt and T. D. Lee, Motor control and learning: A behavioral emphasis, 1999; C. J. Winstein, P. S. Pohl, and R. Lewthwaite, Res Q Ex Sport, 1994; J. R. Carey, E. Bhatt, and A. Nagpal, " Exercise and Sport Science Review, vol. 33, pp. 24-31, 2005.
NJIT-RAVR
CIMT
Mary Free Bed Rehab Hospital
MIT-MANUS
Problem To Be Solved
Can a tracking-training system developed for the clinic1 be deployed in the home?
1Carey et al, Brain, 2002
Home-Based, Clinician-Directed Therapy
• At home• Patient in control• No transportation needed
Limitations• No therapeutic touch• Cannot recognize clinical
subtleties• Cognitive, physical abilities
of patients
Tracking Task
Joint motion controls vertical motion
Many trials
Vary the Waveform
Frequency (Hz) 0.2, 0.4, 0.8
Amplitude (% ROM) 0-50, 30-70, 50-100, 0-125
Duration (s) 5,10,15,20
Vary the Posture
And the direction…
FeedbackTracking
Provide Directions and Feedback
Study #1: Finger & WristCarey et al, Neurorehabil Neural Repair, 2007; Durfee et al, J Medical Devices, 2010
Study Details
• 24 subjects with chronic stroke• 2 to 305 mi. from UMN, one at 1,057 mi.• 180 trials/day x 10 days = 1800 trials
Pre & Post Assessment1. Box and Block2. Jebsen Taylor Hand Function3. Finger range of motion4. Finger tracking accuracy5. fMRI (cortical activation intensity and
location)
Tracking and Move GroupsCarey et al, Neurorehabil Neural Repair, 2007
Lesion
NeurorahabNeural Repair, 21:216, 2007
PRE
POST
Key Results• Improved on functional tests• Improved in tracking accuracy and finger
ROM (track group)• Cortical activity shift towards lesioned side• Tracking and move group had similar
results• High tolerance for technology, could self-
install system and don/doff sensors
Conclusion: Tracking training at home is feasible and effective.
Study #2: Ankle
Technology Architecture
BUTTON
ROTARY POT LPF, 10 HZ ADC, 16-BITMICROCONTROLLER
PC
USB CELLULAR MODEM
INTERNET VIA CELL PHONE NETWORK
USBWEBCAM W/ MIC
PC
INTERNET
USBWEBCAMW/MIC
CLINIC STATION
HOME STATION
USBWIRE
INTERFACE BOX
At the Patient’s Home
1-Button Operation
Tele Session, Example 1
Tele Session, Example 2
Careful Design is Critical• Easy to use
–1 button operation–Simple setup…by the patient–Therapist controls tele
• Donning/doffing sensor• Works anywhere
–Cellular modem for internet
• Anticipate events–Failure effects analysis
6060
Protocol (n=20)
PRE-TEST POST-TEST
TREATMENT(TRACKING)
CONTROL(MOVING)
Ankle tracking accuracyBrain reorganization (fMRI)Gait analysis (kinematics)Walking speed
Ankle tracking accuracyBrain reorganization (fMRI)Gait analysis (kinematics)Walking speed TRACK GROUP
20 days at home3600 tracking trials180 trials/dayTeleconsult 3X/wk
Gait Analysis
• Minimum toe clearance• Functional range of motion
Results, One Subject
Post-Test
25°
20°
15°
10°
5°
0°
-5°
-10°
-15°
-20°
Dorsi flexion
Plantar flexion
Sagi
ttal A
nkle
Ang
le (d
egre
es)
Pre-Test
Normal
Post-Test
25°
20°
15°
10°
5°
0°
-5°
-10°
-15°
-20°
Dorsi flexion
Plantar flexion
Sagi
ttal A
nkle
Ang
le (d
egre
es)
Pre-Test
Normal
Cortical Activation (1004)
Stroke on L side
Preliminary Assessment of Home-Based Stroke Rehab
• Favorable subject reaction• Measurable rehab outcomes• Requires tech support• Technology changing quickly• Optimal rehab paradigms not known• Cost ???
Remember to focus on patient needs
Practical Applications of Muscle Stimulation
MUSCLE!
MUSCLE
• 40% of body weight• 640 move you• Work in pairs, can only push• Eye muscles move 100,000
times/day• Gluteus maximus is largest• Sartorius is longest
REANIMATING PARALYZED
MUSCLE
Brain
Spinal Cord
Limb
Stimulator
Liberson foot-drop system, 1961
Heel switch triggered peroneal n. stimulationCorrection of foot-drop following strokeStarted field of FESSeveral commercial and research embodiments
Medtronic implanted foot-drop system
Upper Limb FES
• Grasp restoration• Forearm and hand muscle stimulation• Rudimentary grip facilitates independence
NeuroControl FreeHand
Cleveland FES Center
Cleveland FES Center
FEXTERNAL
CONTROL STIMULATORInputs
Measurements
• Improve health through weight bearing• Brief standing: social and functional• Limited ambulation in vicinity of wheelchair• No balance, no change in neuro function
LOWER LIMB FES: Standing and Gait
asimo.honda.com
IS IT LIKE A BIPED ROBOT?
WHAT MAKES FES DIFFERENT?
• Not enough muscles • Not enough sensors• Muscle force too low• Muscle fatigues• Spasticity• Difficult to control with
precision• No control over rest of body• Command channel• Muscles are not electric
motors• Size/weight constraints • Reliability
Muscle stimulation
provides power
Brakes for locking and
control
Orthosis provides guidance
and support
CBO in operation
• Stimulate quadriceps for stance control– High force, high
energy (relatively)• Stimulate reflex for
stepping motion– Erratic– Habituates
• CBO controls swing, locks during stance
• Orthosis a mounting platform for sensors
Cleveland FES Center
ENERGY STORING BRACE
Energy Storing Orthosis
(a) (b)
Take in ambient (atmospheric) air as knee flexes
Release ambient (atmospheric pressure) air as hip flexes
Compress air and force into accumulator as knee extends
(c)
Discharge pressurized air to drive hip extension
Energy budget• ~30 nM over 60 deg
of motion• 31.4 J per extension• Extract 14 J per
cycle
Hausdorff and Durfee, Med Biol Eng Comp, 1991. 29:269-280.
How Much Energy Can Be Extracted From the Quads?
Celotta, MS Thesis, 2006
N = 10 non-impaired subjects70 deg liftStim fixed for 50 Nm at 90 degEnergy = gravity lift + brake
PASSIVE LIFTCONTROLLED TRAJECTORY
STIM for 2.0 s1. rest for 3.0 s, 40% duty cycle2. rest for 8.0 s, 20% duty cycle
Normal gait, quads on 35%
15-18 J Minimum Over All Subjects
Limitations: (1) Non-impaired subjects, (2) 50 Nm target torque
ADAMS dynamic model
J. Biomechanical Engineering, 127(6):1014-1019, 2005.
Bench prototype
Leg: accurate length, inertia, COM
Gas springs: Arvin Motion Control
Cylinders: 7/8”bore, 2.5” stroke,
BimbaValve: solenoid, 2-
position, Mead
Accumulator: teflon tube, 1/16”
bore x 18”
ISSUES IN POWERED
EXOSKELETONS
General Electric Hardiman
Sarcos Raytheon XOS Exoskeleton popsci.com
LIFESUIT, theyshallwalk.org
Cyberdyne, HAL-5
ReWalk, Argo Medical Technologies
www.argomedtec.com
Ironman, 2008
Challenges• Power
supply• Actuators• Packaging• Control
The Power Supply
Power Supply
ENERGYSOURCE
ENERGYCONVERSION
USEFULPOWER
Battery Conditioning
Hydrogen Fuel Cell
Hydrocarbon Fuel IC Engine
www.hardingenergy.com
Battery Metrics
DC Motor + Battery
• 285 lb total • 66 lb battery• 20 min life
Energy Density
0.2 0.6
20
0
5
10
15
20
25M
J/K
g
NiMh Lith Ion Methanol
Power Density
160250
1453
0
500
1000
1500W
/Kg
NiMh Batteries
electrochemicalreaction
Electrical PowerDC servo Mechanical Power Output
~ 145-260 kJ/kg (servo motor)(290 kJ/kg) %100≈η %90%50 −≈η
Batteries / DC Motors
83HC(46,350 kJ/kg)
internalcombustion PE
(hot)
adiabaticexpansion
KE
adiabaticcompression PE
(cold)
adiabaticexpansion Mech. Power Output
(pneumatic actuator)~1,500 kJ/kg (desired)
(goal) %24.3≈η
IC Engine Compressor
Energy Transduction
Source: Prof. Eric Barth, Vanderbilt University
POWERED ANKLE ORTHOSIS
Georgia Institute of TechnologyMilwaukee School of Engineering
North Carolina A&T State UniversityPurdue University
University of Illinois, Urbana-ChampaignUniversity of Minnesota
Vanderbilt University
www.ccefp.org
A National Science Foundation Engineering Research Center
Vision: Transform fluid power by making it more compact, more efficient and more effective
Goals:1) Dramatically improve the efficiency of existing FP systems2) FP enabled passenger cars with better fuel economy and cost
structure 3) New to the world human scaled FP devices that can do useful work4) Make all of the above ubiquitous
Test Beds
Excavator Hydraulic Hybrid Vehicle
Rescue Robot Wearable Fluid Power
Portable Fluid Power Exists
The Baggage
19" x 18" x 20", 87 lbs
Why the Ankle?
• Cyclic motion• Known dynamic profiles• Reasonable angle, torque power range• Stringent packaging constraints
Ankle Dynamics
-10
-5
0
5
10
15
20
0 50 100
Gait Cycle (%)
Ang
le (d
eg)
-100
1020304050607080
0 20 40 60 80 100
Gait Cycle (%)
Torq
ue (N
-m)
85 Kg person walking, source: Winters: Biomechanics of Human motion
Ankle Power, 85 Kg Person Walking
-50
0
50
100
150
200
0 20 40 60 80 100
Gait Cycle (%)
Pow
er (W
)
Peak ~200 W
Average ~13 W
85 Kg person walking, source: Winters: Biomechanics of Human motion
With David Kittelson, Lei Tian, Department of Mechanical Engineering, University of Minnesota; and Eric Barth, Department of Mechanical Engineering, Vanderbilt University
Miniature HCCI Free-Piston Engine-Compressor
• Develop engine-compressor to provide about 10 W of compressed air
• Applications: ankle orthosis, human assist tools• Advantage over competition (projected)
– More compact than battery + motor– Easier to manufacture than micro turbine
Homogeneous Charge Compression Ignition
Image from New Scientist, Jan, 2006
Engine CAD Model
Next Steps
• Determine fuel• Dynamic model
–Optimize combustion, bounce, compression chambers
–Optimize stroke/bore
• Thermodynamic model–Predict efficiencies
• Construct & bench test prototype
FUTURE MICRO FPAC + 1 KPSI ACCUMULATOR
CONCLUDING REMARKS
And a few other projects
Replacing muscle
Power (W/lb)
0
50
100
150
200
250
Muscle--peak Muscle--sustained
Electric motor Automobileengine
Vogel (2001), "Prime Mover"(Aircraft engine, piston: 700; Aircraft engine, turbine: 2500)
Muscle metrics• Uni-direction, short stroke (5-20%)• Pull force: 30 lbs/sq. in.• 90 W/lb peak
– 180 lb athlete w/ 72 lb of muscle does 370 W sustained = 5 W/lb
• 25% efficient• Compliant, back-drivable• Extensive infrastructure• Fatigues• Clean• Cool• Quiet
Vogel (2001), "Prime Mover"
!
Competition is $19 Piece of Plastic
Thanks!