Team Members:Team Members:

Brant Kochsiek BSACBrant Kochsiek BSAC

Steve Pauls Team LeaderSteve Pauls Team Leader

Tim Rand CommunicatorTim Rand Communicator

Brian SchwartzBrian Schwartz BWIGBWIG

Client:Client:

David Beebe, Ph. DDavid Beebe, Ph. D

Biomedical EngineeringBiomedical Engineering

Advisor:Advisor:

Naomi Chesler, Ph. DNaomi Chesler, Ph. D

Biomedical EngineeringBiomedical Engineering

AbstractAbstract

Many running injuries are caused by continued use Many running injuries are caused by continued use of improper or worn running shoes. The increase in of improper or worn running shoes. The increase in incidence of injury can be directly correlated to the incidence of injury can be directly correlated to the degradation of the materials used in shoe sole degradation of the materials used in shoe sole construction. The degree to which a shoe sole construction. The degree to which a shoe sole degrades is directly related to the changing degrades is directly related to the changing elasticity of the material. Two different methods are elasticity of the material. Two different methods are proposed to measure elasticity in a shoe sole. proposed to measure elasticity in a shoe sole. Strain gauges and Flexi-Force piezoelectric force Strain gauges and Flexi-Force piezoelectric force sensor devices have been added to an integrated sensor devices have been added to an integrated circuit that will indirectly measure shoe sole circuit that will indirectly measure shoe sole elasticity. Once calibrated, each circuit will have a elasticity. Once calibrated, each circuit will have a diode that lights when a shoe sole is worn past its diode that lights when a shoe sole is worn past its useful life.useful life.

Problem MotivationProblem MotivationRunning shoes last Running shoes last 300-500 miles 300-500 miles

Worn shoes do not Worn shoes do not always appear wornalways appear worn

Incidence of injury Incidence of injury increases with worn increases with worn shoesshoes

http://members.cox.net/gumpisms/hanks1.jpg

Client RequirementsClient Requirements

Design a device that:Design a device that:– Measures shoe sole elasticityMeasures shoe sole elasticity– Fits ergonomically into the shoe soleFits ergonomically into the shoe sole– Is lightweight and small so as to not hinder Is lightweight and small so as to not hinder

performanceperformance– Operable for the life of a running shoe (300-Operable for the life of a running shoe (300-

500 miles)500 miles)– Has a clear indicator so the runner will know Has a clear indicator so the runner will know

when the shoe is sufficiently wornwhen the shoe is sufficiently worn

Shoe MaterialsShoe Materials

Ethylene Vinyl Acetate (EVA)Ethylene Vinyl Acetate (EVA)

Polyurethane (PU)Polyurethane (PU)

Outsole

Midsole

Upper

Footbridge

http://www.dummies.com/WileyCDA/DummiesArticle/id-450,subcat-SPORTS.html

Nominal Running StyleNominal Running Style

• Heel strike

• Inward pronation (rolling action of the foot)

• Ball of foot strike

• Forefoot push off

http://www.dummies.com/WileyCDA/DummiesArticle/id-450,subcat-SPORTS.html

Pressure Distribution while RunningPressure Distribution while Running

Maximum pressures in the midsole occur beneath the heel, the middle to inner portion of the forefoot, and the big toe.

http://www.uni-essen.de/~qpd800/index.html

Comparator/LEDComparator/LED

Differential AmplifierDifferential Amplifier

Drive CircuitDrive Circuit

Voltage regulatorVoltage regulator

Force Sensor CircuitForce Sensor Circuit

FlexiForce® SensorsFlexiForce® Sensors

Comparison of forces Comparison of forces from top to bottomfrom top to bottom

http://www.tekscan.com/flexiforce/flexiforce.html

http://www.btinternet.com/~bury_rd/cheatah.jpg

Strain Gauge CircuitStrain Gauge Circuit

Comparator/LEDComparator/LED

Differential AmplifierDifferential Amplifier

Strain GaugeStrain Gauge

Strain GaugeStrain GaugeConstant Poisson’s Constant Poisson’s Ratio (Ratio (v)v), ,

Stress-Strain (Stress-Strain (δδ--εε)) for for Elasticity (E)Elasticity (E)

http://www.btinternet.com/~bury_rd/cheatah.jpg

www.sensorland.com/ HowPage002.html

Variable Force Variable Force SensorsSensors

Strain GaugeStrain Gauge

CostCost 33 44

Measurement Measurement accuracyaccuracy

55 33

DurabilityDurability 33 33

Circuit Circuit integrationintegration

22 33

SizeSize 33 33

PerformancePerformance ?? ??

TotalTotal 1616 1616

1 = Worst 5 = Best

AdvantageAdvantage DisadvantageDisadvantage

FlexiForce®FlexiForce®

Force Force comparisoncomparison

-Paper thin-Paper thin

-Allows for fine -Allows for fine adjustmentsadjustments

-More precise-More precise

-Complicated -Complicated constructionconstruction

-Complex -Complex comparative comparative circuitcircuit

-More expensive-More expensive

Strain Gauge Strain Gauge MeasurementMeasurement

-Cost-Cost

-Simple circuit-Simple circuit

-Simple -Simple constructionconstruction

-More of an -More of an indirect indirect measurementmeasurement

-More bulky-More bulky

Preliminary TestingPreliminary TestingSensor response Test

0

1

2

3

4

5

6

0 200 400 600 800 1000

Load (lbs)

Vo

lta

ge

(V

)

Tested

Projected

Current StandingCurrent Standing

Preliminary tests showed flaws in our Preliminary tests showed flaws in our circuit and sensor set upcircuit and sensor set up

Circuit is being reworked and future testing Circuit is being reworked and future testing will soon followwill soon follow

Research into exact placement of sensors Research into exact placement of sensors in shoe sole is ongoingin shoe sole is ongoing

Testing ProcedureTesting Procedure

Apply static loads to sensors imbedded in Apply static loads to sensors imbedded in silicone polymersilicone polymer

Loads applied in sets of 4000 which Loads applied in sets of 4000 which correlates to about a 6 mile runcorrelates to about a 6 mile run

Following each set:Following each set:– Elasticity of material will be measuredElasticity of material will be measured– Output of circuit will be read from multimeterOutput of circuit will be read from multimeter– Output vs. elasticity will be plottedOutput vs. elasticity will be plotted

MTS Servohydraulic MachineMTS Servohydraulic Machine

We plan to use an older version of this We plan to use an older version of this machine found in the Materials Testing machine found in the Materials Testing Lab in Engineering HallLab in Engineering Hall

http://www.mts.com/menusystem.asp?DataSource=0&NodeID=1483

Future WorkFuture WorkMold strain gauge into silicon moldMold strain gauge into silicon moldTest both prototypes to simulate 500 miles of Test both prototypes to simulate 500 miles of running wearrunning wearDetermine the correlation between the output of Determine the correlation between the output of each device and elasticityeach device and elasticityDetermine shoe sole wear threshold valueDetermine shoe sole wear threshold valueIntegrate chosen device and corresponding Integrate chosen device and corresponding circuit into a shoe sole for testingcircuit into a shoe sole for testingResearch and go through necessary human Research and go through necessary human subject testing proceduressubject testing proceduresUndergo human testing of the prototype shoeUndergo human testing of the prototype shoePossible patent applicationPossible patent application

ReferencesReferences““1000 Hz High-Cycle Fatigue Testing Systems.” 1000 Hz High-Cycle Fatigue Testing Systems.” MTS Inc. MTS Inc. Accessed 4/28/04 URL: Accessed 4/28/04 URL: http://www.mts.com/menusystem.asp?DataSource=0&NodeID=1483http://www.mts.com/menusystem.asp?DataSource=0&NodeID=1483““Anatomy of a Running Shoe.” Anatomy of a Running Shoe.” American Running AssociationAmerican Running Association. .

Accessed: 04/26/04 URL: Accessed: 04/26/04 URL: http://http://www.americanrunning.org/displayindustryarticle.comwww.americanrunning.org/displayindustryarticle.com..

““Biomechanics Laboratory.” Accessed: 04/24/04 URL: Biomechanics Laboratory.” Accessed: 04/24/04 URL: http://www.uni-essen.de/~qpd800/index.html.http://www.uni-essen.de/~qpd800/index.html. ““BTopenworld”. Accessed: 04/24/04 URL: BTopenworld”. Accessed: 04/24/04 URL:

http://www.btinternet.com/~bury_rd/cheatah.jpg.“FlexiForce Force Sensors.” Tekscan. Accessed: 04/25/04 URL:

http://www.tekscan.com/flexiforce/flexiforce.html.“Forrest Gump Pictures.” Cox Members High Speed Internet. Accessed 02/26/04 URL: http://members.cox.net/gumpisms/hanks1.jpgHennig, E. M., & Milani, T. L. 1995. In-shoe Pressure Distribution for

Running in Various Types of Footwear. Human Kinetics Publishers Inc., New York.

Mills, N., & Verdejo, R. 2002. Performance of EVA Foam in Running Shoes. Blackwell Inc., UK, Birmingham.

“Runner’s World.” Runners World. Accessed:04/27/04 URL: http://www.runnersworld.com/.“Running Shoes.” ePodiatry. Accessed: 04/26/04 URL:

http://www.epodiatry.com/running-shoes.htm,

Special ThanksSpecial Thanks

Professor David BeebeProfessor David BeebeProfessor Naomi CheslerProfessor Naomi Chesler

Amelia CosgroveAmelia CosgroveJohn W. DregerJohn W. Dreger

Ivar MeyvantssonIvar Meyvantsson Professor Tim OsswaldProfessor Tim Osswald

Professor Mitch TylerProfessor Mitch TylerPaul VictoreyPaul Victorey

Professor John WebsterProfessor John Webster