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Design Case Studies in Rehabilitation Engineering William Durfee Department of Mechanical Engineering University of Minnesota Minneapolis, USA And a few other projects
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Page 1: Design Case Studies in Rehabilitation Engineeringwkdurfee/presentations/rehab-eng-case-studies.… · Design Case Studies in Rehabilitation Engineering William Durfee Department of

Design Case Studies in Rehabilitation Engineering

William DurfeeDepartment of Mechanical Engineering

University of MinnesotaMinneapolis, USA

And a few other projects

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BRIDGE

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• 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

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www.dmdconf.org

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Rehabilitation Engineering

The application of engineering principles to treatment, services and devices related to people with disabilities

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20-49 million in U.S.

6.5% of GDP

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Therapeutic Technology

Any equipment that treats an impairment

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www.empi.com

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www.donjoy.com

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Assistive Technology

Any equipment that increases ability or function

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bionics.ossur.de

www.abledata.com

www.abledata.com

www.dekaresearch.com

www.ric.org

www.technologyreview.com

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Photos from Paraplegia News and Sports ‘n Spokes

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MEDICAL VIEW

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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

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PERSON VIEW

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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

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USER TASK

AT DEVICE

1

2

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IT'S MORE THAN THE TECHNOLOGY

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30-50% of AT devices are abandoned

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TELEREHABILITATION

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"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

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7 hrs

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Why tele?

• Clients in rural locations• Clients in urban locations, but have

transportation challenges–No car–Poor public transportation

• Eliminates transportation time

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TRAINING RECOVERY OF

HAND FUNCTION FOLLOWING STROKE

Collaborators: James Carey, Samantha Weinstein, Ela Bhatt, Ashima NagpalFunding: NIDRR, H133G020145

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MOVEMENT

CONCENTRATION

LEARNING

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Tracking task

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HOME-BASED TRACKING

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USABILITY

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FeedbackTracking

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CLINICAL TRIAL24 Subjects

2 to 305 miles from the U

One at 1,057 miles

180 trials/day x 10 days = 1800 trials

Pre-post function and fMRI

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Task Variants

5, 10, 15, 20 secDuration

0-50%, 30-70%, 50-100%, 0-125% of

active range Amplitude

0.2, 0.4, 0.8 HzFrequency

Hand Position: Pronated, Mid, SupinatedJoint: Finger, WristHand: Ipsi, ContraVisual feedback: On, Off

Wave parameters

Wave shapes

100 combinations selected

Page 38: Design Case Studies in Rehabilitation Engineeringwkdurfee/presentations/rehab-eng-case-studies.… · Design Case Studies in Rehabilitation Engineering William Durfee Department of

Pre-Post Evaluations

• Box and Block• Jebsen Taylor Hand Function• Finger Range of Motion• Finger Tracking Performance• fMRI (cortical activation intensity and

location)

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A. Box and Block, B. Jebsen Taylor, C. Finger ROM, D. AI score

Neurorahab Neural Rep, 21:216, 2007

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Lesionon right

PRE

POST

Neu

rora

hab

Neu

ral Rep

, 21:2

16,

2007

Page 42: Design Case Studies in Rehabilitation Engineeringwkdurfee/presentations/rehab-eng-case-studies.… · Design Case Studies in Rehabilitation Engineering William Durfee Department of

Key Results

• Improved in tracking accuracy and finger ROM

• Improved on functional tests• Cortical activity shift towards lesioned side• Subjects had high tolerance for

technology, could self-install system and don/doff sensors

• Tracking and move group had similar results

Conclusion: Tracking training at home is feasible and effective.

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NEXT STEPS

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Practical Applications of Muscle Stimulation

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• Bladder stimulation (incontinence)• Deep brain stimulation (movement

disorders)• Visual prostheses (artificial retina, cortical

stim)• Auditory prostheses (cochlear implant)• Pain suppression (TENS)• Pacemakers• Limb control (paralysis)

E-STIM APPLICATIONS

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www.biotronik.de

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Earl Bakken, University of Minnesota, Medtronic and the

portable pacemaker

medtronic.com and Bakken Museum

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The Stimulator

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Brain

Spinal Cord

Limb

Stimulator

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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

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Upper Limb FES

Grasp restorationForearm and hand muscle stimulationRudimentary grip facilitates independence

NeuroControl FreeHand

Cleveland FES Center

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Cleveland FES Center

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FES-AIDED GAIT

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FEXTERNAL

CONTROL STIMULATORInputs

Measurements

FEXTERNAL

• Improve health through weight bearing• Brief standing: social and functional• Limited ambulation in vicinity of wheelchair• No balance, no change in neuro function

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Cleveland FES CenterCLEVELAND FES CENTER

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PROBLEMS WITH FES-AIDED GAIT

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•Not enough muscles•Not enough sensors•Low muscle forces•Muscle fatigues•No control over upper body•Muscles not electric motors•Size/weight/cosmesis

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Requires precise, stable control for repeatable steps

Muscles are nonlinear,

time-varying

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Need to walk reasonable distances

Muscles fatigue rapidly

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STIMULATION PLUS SMART ORTHOTICS

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Muscle stimulation

provides power

Brakes for locking and

control

Orthosis provides guidance

and support

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INCREASED SPEED, DISTANCE

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Without CBO With CBO

Gait Speed

0.09

0.12

Spee

d (m

/s)

0

10

20

30

40

50

60

Without CBO With CBO

Gait Distance

25

50

Dis

tanc

e (m

)

IEEE Trans Rehab Eng, 4(1):13, 1996, IEEE Trans Rehab Neural Eng, 2003

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BETTER REPEATABILITY

0

20

40

60

80

100

120

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

20

40

60

80

100

120

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Time (sec)

With CBO

Time (sec)

Without CBO

Kne

e an

gle

(deg

)

Kne

e an

gle

(deg

)

IEEE Trans Rehab Eng, 4(1):13, 1996, IEEE Trans Rehab Neural Eng, 2003

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NEXT GENERATION

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Prostheses/Orthoses Complexities

• Intimately coupled with body• High forces• Power transmission

Prosthesis (Gk: “prostitheni”, to add)Orthosis (Gk: “orthos”, straight)

• Fitting– Spread the load– Zero shear– Maintain blood flow

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I.D. Magazine May 1998

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Hip belt

Placeholders for brakes

Knee brace

Prismatic joint

Ab/adductionhinge

Medial hinge

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ENERGY STORING BRACE

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Energy Budget• ~30 nM over 60 deg

of motion• 31.4 J per extension• Extract 14 J per cycle

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J. Biomechanical Engineering, 127(6):1014-1019, 2005.

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ADAMS dynamic model

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Gas springs

Cylinders

Accumulator

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Non-invasive diagnostics of muscle activity

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Mechanical and electrical properties provide window into muscle excitation contractionSmart stimulation, smart system id can isolate subsystemsFor differential diagnosesGo beyond, “This muscle is weak, let’s biopsy.”

MUSCULOSKELETAL SYSTEMSTIM

u(t)

FORCE/MOTION

y(t)

Page 83: Design Case Studies in Rehabilitation Engineeringwkdurfee/presentations/rehab-eng-case-studies.… · Design Case Studies in Rehabilitation Engineering William Durfee Department of

Model OverviewStimulation in, joint angle out. Muscle acts on skeletal system to product measurable joint motion. Model must account for muscle dynamics, joint geometry and limb dynamics.

MUSCULOSKELETALSYSTEMSTIM

u(t)

FORCE/MOTION

y(t)

MT GEOM

GEOM-1

u(t)

LDθ(t)τ(t)f(t)

x(t)

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MUSCLES

Force = f(neural input, length, velocity, time, ...)

F

Activation

F

Velocity Time

FF

Length

Page 86: Design Case Studies in Rehabilitation Engineeringwkdurfee/presentations/rehab-eng-case-studies.… · Design Case Studies in Rehabilitation Engineering William Durfee Department of

a(t)LM(t)

VM(t)

CE

SE

PE

muscle

tendon

FM(t)=FT(t)=f(t)

passive

Page 87: Design Case Studies in Rehabilitation Engineeringwkdurfee/presentations/rehab-eng-case-studies.… · Design Case Studies in Rehabilitation Engineering William Durfee Department of

WHAT'S WRONG WITH THE MUSCLE MODEL

Invariant F-A, F-L, F-V (no change with activation)Invariant twitch dynamics (uniform fiber types)Time-invariant (no fatigue)

CEKSE

XCEXSE

XMT

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Skeletal muscle, isometric twitch

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MODELING ISOMETRIC MUSCLE

Staticnonlinearity

Lineardynamic system

Hammerstein model

stim force

Identify LDS with impulse responseDurfee & Palmer, IEEE TBME, 1994

Identify SL by deconvolutionDurfee & MacLean, IEEE TBME, 1989

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020406080

100120140

0 100 200 300 400

Time (mS)

Torq

ue

2)( ask+

SINGLET

BEST FIT

Linear system fit to singlet

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Muscle Force-Velocity

FORCE

VELOCITYSHORTENINGLENGTHENING

LINEAR FIT

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MODEL OK FOR ISOLATED MUSCLE

0

5

10

15

20

25

30

35

0 4 8 12 16

Forc

e (N

)

Time (s)

IEEE Trans. Biomed. Eng., 41(3):205, 1994)

Experiment

Model

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Using a nonlinear muscle behavior for

a diagnostic

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0

50

100

150

200

250

300

350

400

450

500

0 50 100 150 200 250 300 350 400

Time (ms)

Torq

ue

Single pulse twitch

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0

50

100

150

200

250

300

350

400

450

500

0 50 100 150 200 250 300 350 400

Time (ms)

Torq

ue

Double pulse twitch, if ideal linear system

y 2y

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0

50

100

150

200

250

300

350

400

450

500

0 50 100 150 200 250 300 350 400

Time (ms)

Torq

ue

Double pulse twitch, real

3.2 y

Page 98: Design Case Studies in Rehabilitation Engineeringwkdurfee/presentations/rehab-eng-case-studies.… · Design Case Studies in Rehabilitation Engineering William Durfee Department of

Experiments

F-L, F-V, contraction dynamics, doublet propertiesBuild database for several muscles in non-impaired subjects

Nash Avery Search for Hope Fund via the Paul and Sheila Wellstone Muscular Dystrophy Center, University of Minnesota.

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Force vs. Acceleration

-15-10-505

1015

-2 -1 0 1 2

Acceleration (g)

Forc

e (lb

-f)

Estimating limb inertia, simple clinical tool

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POWEREDHUMAN-ASSIST

TOOLS

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Engineering Research Center for Compact & Efficient Fluid Power

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•Compact power sources•Natural interface and control

•Portable and/or wearable

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BENCHMARKING ACTUATORS

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And a few other projects

MUSCLE!

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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

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Muscle metrics

• Short-stroke, linear actuator– 5-20% shortening stroke

• Pull force: 30 lbs/sq. in.• 90 W/lb

– 180 lb athlete w/ 72 lb of muscle puts out 370 W sustained 5 W/lb for human muscle for continuous use

• 25% efficient• Compliant, back-drivable• Fatigues• Clean• Quiet !

Vogel (2001), "Prime Mover"Vogel (2001), "Prime Mover"

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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)

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Miniature free-piston air-compressor

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FUTURE MICRO FPAC + 1KPSI TANK

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