Design Case Studies in Rehabilitation...

transcript

Design Case Studies in Rehabilitation Engineering

William DurfeeDepartment of Mechanical Engineering

University of MinnesotaMinneapolis, USA

And a few other projects

BRIDGE

• 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/)

PE Force-Velocity

CE Force-Velocity

Fscale

CE Force-Length

Activation Dynamics (2nd order)

PE Force-Length

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

www.dmdconf.org

Rehabilitation Engineering

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

20-49 million in U.S.

6.5% of GDP

Therapeutic Technology

Any equipment that treats an impairment

www.empi.com

www.donjoy.com

Assistive Technology

Any equipment that increases ability or function

bionics.ossur.de

www.abledata.com

www.dekaresearch.com

www.ric.org

www.technologyreview.com

Photos from Paraplegia News and Sports ‘n Spokes

MEDICAL VIEW

StrokeSCIMS

Muscular Dystrophy

ArthritisAmputationAlzheimer’s

Medical Condition Cognitive•Sensory/Motor integration•Memory•Reasoning

Physical

Sensory

•Speech•Balance•Gait•Coordination•Grip•Arm

•Sight•Sound

Impairment

PERSON VIEW

Person

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

USER TASK

AT DEVICE

IT'S MORE THAN THE TECHNOLOGY

30-50% of AT devices are abandoned

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

Why tele?

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

transportation challenges–No car–Poor public transportation

• Eliminates transportation time

TRAINING RECOVERY OF

HAND FUNCTION FOLLOWING STROKE

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

MOVEMENT

CONCENTRATION

LEARNING

Tracking task

HOME-BASED TRACKING

USABILITY

FeedbackTracking

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

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

Pre-Post Evaluations

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

location)

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

Neurorahab Neural Rep, 21:216, 2007

Lesionon right

ral Rep

, 21:2

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.

NEXT STEPS

Practical Applications of Muscle Stimulation

• 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

www.biotronik.de

Earl Bakken, University of Minnesota, Medtronic and the

portable pacemaker

medtronic.com and Bakken Museum

The Stimulator

Spinal Cord

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 restorationForearm and hand muscle stimulationRudimentary grip facilitates independence

NeuroControl FreeHand

Cleveland FES Center

FES-AIDED GAIT

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

Cleveland FES CenterCLEVELAND FES CENTER

PROBLEMS WITH FES-AIDED GAIT

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

Requires precise, stable control for repeatable steps

Muscles are nonlinear,

time-varying

Need to walk reasonable distances

Muscles fatigue rapidly

STIMULATION PLUS SMART ORTHOTICS

Muscle stimulation

provides power

Brakes for locking and

control

Orthosis provides guidance

and support

INCREASED SPEED, DISTANCE

Without CBO With CBO

Gait Speed

Without CBO With CBO

Gait Distance

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

BETTER REPEATABILITY

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

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

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

NEXT GENERATION

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

I.D. Magazine May 1998

Hip belt

Placeholders for brakes

Knee brace

Prismatic joint

Ab/adductionhinge

Medial hinge

ENERGY STORING BRACE

Energy Budget• ~30 nM over 60 deg

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

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

ADAMS dynamic model

Gas springs

Cylinders

Accumulator

Non-invasive diagnostics of muscle activity

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

FORCE/MOTION

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

FORCE/MOTION

MT GEOM

GEOM-1

LDθ(t)τ(t)f(t)

MUSCLES

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

Activation

Velocity Time

Length

a(t)LM(t)

muscle

tendon

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

passive

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)

XCEXSE

Skeletal muscle, isometric twitch

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

020406080

100120140

0 100 200 300 400

Time (mS)

2)( ask+

SINGLET

BEST FIT

Linear system fit to singlet

Muscle Force-Velocity

VELOCITYSHORTENINGLENGTHENING

LINEAR FIT

MODEL OK FOR ISOLATED MUSCLE

0 4 8 12 16

Time (s)

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

Experiment

Using a nonlinear muscle behavior for

a diagnostic

0 50 100 150 200 250 300 350 400

Time (ms)

Single pulse twitch

0 50 100 150 200 250 300 350 400

Time (ms)

Double pulse twitch, if ideal linear system

0 50 100 150 200 250 300 350 400

Time (ms)

Double pulse twitch, real

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.

Force vs. Acceleration

-15-10-505

-2 -1 0 1 2

Acceleration (g)

Estimating limb inertia, simple clinical tool

POWEREDHUMAN-ASSIST

Engineering Research Center for Compact & Efficient Fluid Power

•Compact power sources•Natural interface and control

•Portable and/or wearable

BENCHMARKING ACTUATORS

And a few other projects

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

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"

Power (W/lb)

Muscle--peak Muscle--sustained

Electric motor Automobileengine

Vogel (2001), "Prime Mover"(Aircraft engine, piston: 700; Aircraft engine, turbine: 2500)

Miniature free-piston air-compressor

FUTURE MICRO FPAC + 1KPSI TANK

Design Case Studies in Rehabilitation...

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