wireless structural healthwireless structural health...

Wireless Structural HealthWireless Structural Health Monitoring Systems

Presentation to: Czech Technical UniversityCzech Technical University

Prague, Czech Republic

21 July 2008

St A P id tSteven Arms, PresidentMicroStrain, Inc.

swarms@microstrain [email protected]

© MicroStrain, Inc. 2008, all rights reserved

MicroStrain’sMicroStrain’s Smart Smart SensorsSensorswww microstrain com/customer docs htm

DisplacementDisplacement OrientationOrientation WirelessWireless

www.microstrain.com/customer-docs.htm

DVRTDVRT®® 3DM3DM--GX1GX1®® GG--LinkLink®, ®, VV--LinkLink®, ®,

SGSG LinkLink TCTC LinkLink

Robotic Robotic systemssystems

Unmanned Unmanned systemssystems

SGSG--LinkLink®, ®, TCTC--LinkLink® ®

Machine Monitoringsystemssystems systemssystems Monitoring

© microstrain, inc. 2008

MicroStrain:MicroStrain:where we beganwhere we began

•• First arthroscopic First arthroscopic implantation of strain implantation of strain gauge in live humangauge in live humangauge in live human gauge in live human ACLACL

•• Collaboration with Collaboration with Drs. R. Johnson & Drs. R. Johnson & B. B. BeynnonBeynnon, et al. , et al. 19861986


Ligament Strain Measurement

• Arthroscopically implanted• Arthroscopically implanted

• Suture-less attachment

Beynnon et al. J Bone Joint Surg 1992

Beynnon et al. Amer J Sports Med 1996

Fleming et al. Amer J Sports Med 2000Fleming et al. Amer J Sports Med 2000

Sensing Sensing the Futurethe Futurethe Futurethe Future

Wireless sensors, in the billions, will become Wireless sensors, in the billions, will become deeply embedded within structures &deeply embedded within structures &deeply embedded within structures & deeply embedded within structures & machines. machines.

Sensed information will be automatically Sensed information will be automatically compressed & forwarded for conditioncompressed & forwarded for conditioncompressed & forwarded for condition compressed & forwarded for condition based maintenance.based maintenance.


The Economist April 28th – May 4th

2007“We’re wearing out…plan to replace us soon”

2007

Problem:Problem:Problem:Problem:

Wh ill l billi fWh ill l billi fWho will replace billions of Who will replace billions of dead batteries?dead batteries?dead batteries?dead batteries?


Solution:Solution:

MicroStrain’s MicroStrain’s

•• H t & t f th i tH t & t f th i t

MicroStrain sVibration Harvester

MicroStrain sSolar Harvester

•• Harvest & store energy from the environment Harvest & store energy from the environment •• Use power management to balance the energy Use power management to balance the energy

“checkbook”“checkbook”checkbookcheckbook•• Use embedded processors to compress data, Use embedded processors to compress data,

classify operations, estimate fatigue lifeclassify operations, estimate fatigue lifey p , gy p , g


Market: Market: Wireless sensor revenues, $18M in Wireless sensor revenues, $18M in

2004, projected to $700M by 2008 (Frost & Sullivan)2004, projected to $700M by 2008 (Frost & Sullivan)

Partners:Partners:

•• NAVAIR/NAVSEANAVAIR/NAVSEA•• Lockheed MartinLockheed Martin•• Northrop GrummanNorthrop Grumman•• CaterpillarCaterpillar•• Bell HelicopterBell HelicopterBell HelicopterBell Helicopter•• SikorskySikorsky


SHIELD SHIELD -- NIST ATP Joint NIST ATP Joint VVVentureVenture

StructuralStructural HealthHealth IntegratedIntegrated ElectronicElectronic LifeLife DeterminationDetermination SystemSystemStructuralStructural HealthHealth IntegratedIntegrated ElectronicElectronic LifeLife DeterminationDetermination SystemSystem

•• CAT chose CAT chose MicroStrain forMicroStrain forMicroStrain for MicroStrain for wireless strain and wireless strain and vertical gyro vertical gyro expertiseexpertiseexpertiseexpertise

•• Wireless sensor Wireless sensor networks give the networks give the machine a “nervousmachine a “nervousmachine a nervous machine a nervous system”system”

•• System estimates System estimates loads & predicts loads & predicts

Mar 2004 to Oct 2006Total project budget: $ 8.9 M, ATP Cost Share: $ 4.4M

ppfailures onfailures on--boardboard


CivilCivil StructuresStructures

A li tiApplications

Bridge Monitoring ProjectsBridge Monitoring ProjectsBridge Monitoring ProjectsBridge Monitoring Projects

•• Ben Franklin Ben Franklin •• GoldstarGoldstar•• GoldstarGoldstar

Ben Franklin Bridge (BFB)Ben Franklin Bridge (BFB)g ( )g ( )Strain Sensor LocationsStrain Sensor Locations

Location 2Location 1

TypicalTypical Strain Data @ BFB LocationStrain Data @ BFB Location 22Typical Typical Strain Data @ BFB Location Strain Data @ BFB Location 22

407’ Train Speed= 407’ / 12s= 23.1 mph

Strain = 30x10-6

Stress= E x Strain= 870 psi= 870 psi

Solar powered wireless GSolar powered wireless G--Link ® seismic Link ® seismic ppsensors on Corinth Bridge, Greecesensors on Corinth Bridge, Greece

SHM of Historic, Fragile, & SHM of Historic, Fragile, & Priceless StructurePriceless StructurePriceless StructurePriceless Structure

© Microstrain, In© Microstrain, In

Problem Statement:Problem Statement:Problem Statement:Problem Statement:

•• Protect theProtect the•• Protect the Protect the Liberty Bell Liberty Bell during moveduring move

•• Batteries must Batteries must last ~12 hourslast ~12 hours

•• Continuous, high Continuous, high speed dataspeed dataspeed data speed data transmission transmission from multiple from multiple sensor nodessensor nodessensor nodes sensor nodes requiredrequired

© Microstrain, Inc© Microstrain, Inc

MicroMicro displacement sensorsdisplacement sensorsMicroMicro--displacement sensorsdisplacement sensors

k hcrack shear

crack iopening

Medical Applicationspp

Remotely Powered & Interrogated Remotely Powered & Interrogated T t l K R l tT t l K R l tTotal Knee ReplacementTotal Knee ReplacementJohnson & Johnson, Scripps Inst., NK Biotek,Johnson & Johnson, Scripps Inst., NK Biotek,MicroStrain, Inc.MicroStrain, Inc.

First First implantable smart total implantable smart total knee knee replacement, collaboration with replacement, collaboration with Scripps Scripps I i d J&JI i d J&J 20042004Institute and J&JInstitute and J&J, 2004, 2004


3 87.69.8

3.8

18.0

-3.0

First implantable growth plate microFirst implantable growth plate micro--displacement sensor, collaboration with U. displacement sensor, collaboration with U. Wisconsin, 2003 (Wisconsin, 2003 (WilsmanWilsman et al)et al)

Bone Elongation Occurs During Bone Elongation Occurs During RecumbencyRecumbency and Not Duringand Not DuringRecumbencyRecumbency and Not During and Not During

Standing/AmbulationStanding/Ambulation

Aircraft Applicationspp

Structural Test & Model ValidationStructural Test & Model Validation

•• Requires thousands of strain gaugesRequires thousands of strain gauges•• Wiring adds labor cost reduces reliabilityWiring adds labor cost reduces reliability•• Wiring adds labor cost, reduces reliabilityWiring adds labor cost, reduces reliability•• Wire weight is significant Wire weight is significant -- 5000 pounds5000 pounds


The case forThe case forThe case for The case for monitoringmonitoring

•• Boeing F/ABoeing F/A--18 18 designed for 6,000 flight hours designed for 6,000 flight hours

•• Existing hardwired multiExisting hardwired multi--channel monitoring channel monitoring allows F/Aallows F/A--18 to reach 13,000 flight hours18 to reach 13,000 flight hours

•• New aircraft req’d to achieve the additional New aircraft req’d to achieve the additional flightflight--hours would cost ~$11Bhours would cost ~$11B


Aging Fleet Monitoring NeedsAging Fleet Monitoring NeedsAging Fleet Monitoring NeedsAging Fleet Monitoring NeedsLockheed P-3 & Boeing F-15 & : grounded due to unforeseen

structural failures

•• Improved condition based maintenance Improved condition based maintenance –– service/replace service/replace components when neededcomponents when neededcomponents when needed.components when needed.

•• Track loading history of fatigue sensitive components and critical Track loading history of fatigue sensitive components and critical structuresstructuresstructures.structures.

•• When an unexpected failure occurs, have the capacity to rapidly When an unexpected failure occurs, have the capacity to rapidly it th t d t t fl t i ftit th t d t t fl t i ftmonitor those components and structures on fleet aircraft.monitor those components and structures on fleet aircraft.


Load TrackingLoad TrackingLoad Tracking Load Tracking on Helicopterson Helicopters

•• Direct load monitoring of helicopter Direct load monitoring of helicopter rotating structural components could rotating structural components could provide enhanced condition based provide enhanced condition based

i t & i d fli ht ii t & i d fli ht imaintenance & improved flight regime maintenance & improved flight regime recognitionrecognition..

© microstrain, inc. 2008Patents pending

MicroStrain’s proposed helicopter structural MicroStrain’s proposed helicopter structural monitoring system (patent pending)monitoring system (patent pending)


Pitch Link w/ Energy Harvesting, Sensing, Data Pitch Link w/ Energy Harvesting, Sensing, Data Storage, & Wireless CommunicationsStorage, & Wireless CommunicationsStorage, & Wireless CommunicationsStorage, & Wireless CommunicationsMicroStrain, Inc. patents pendingMicroStrain, Inc. patents pending

RF antenna

Circuit board module, microprocessor, and

electrochemical batteryelectrochemical battery

Piezoresistive strain gauge

Electrical insulation, EMI shielding,

& protective covering(shown transparent for(shown transparent for

illustration purposes)

Piezoelectric energy harvesting elements

Sikorsky H-60 Blackhawk© microstrain, inc. 2008

Bell Bell M412M412

•• MicroStrain piggyMicroStrain piggy--backed on Bell’s planned flight testsbacked on Bell’s planned flight tests•• Wired (via slip rings) data could be collected Wired (via slip rings) data could be collected

i lt l ith i l d ti lt l ith i l d tsimultaneously with wireless datasimultaneously with wireless data


MethodsMethodsMethodsMethods

Wireless Pitch Link StrainWireless Pitch Link StrainWireless Pitch Link StrainWireless Pitch Link Strain& Load Sensing Nodes& Load Sensing Nodes

Fractal antennaFractal antenna

© microstrain, inc. 2008Patents Pending

Time Initialization & SynchronizationTime Initialization & Synchronizationyy(patents pending)(patents pending)

•• Pitch link has independent precision Pitch link has independent precision nanonano--power real time power real time clock (RTC) with clock (RTC) with +/+/--3 3 ppmppm time time referencereference

•• RTC time is synchronized at beginning of flight test to RTC time is synchronized at beginning of flight test to hardwired instrumentation GPS time hardwired instrumentation GPS time referencereference

•• Synch beacon sent once Synch beacon sent once -- at start of test only at start of test only -- provided ~5 ms provided ~5 ms timing accuracy over 2 hours subjected totiming accuracy over 2 hours subjected to --40 to +85 C40 to +85 Ctiming accuracy over 2 hours, subjected to timing accuracy over 2 hours, subjected to 40 to +85 C40 to +85 C

•• Synch beacon every 20 minutes will achieve subSynch beacon every 20 minutes will achieve sub--millisecond millisecond timing accuracy when temperatures may be extremetiming accuracy when temperatures may be extremetiming accuracy when temperatures may be extremetiming accuracy when temperatures may be extreme


MicroStrain’s embedded firmware MicroStrain’s embedded firmware optimized for strain gaugesoptimized for strain gauges

•• Wireless offset adjust Wireless offset adjust •• Wireless gain adjustWireless gain adjust•• Wireless control of sample ratesWireless control of sample ratese ess co t o o sa p e atese ess co t o o sa p e ates•• Wireless shunt cal Wireless shunt cal –– bits to bits to microstrainmicrostrain•• LowLow tempco’stempco’s::•• Low Low tempco stempco s: :

offset: offset: --.007%/C , span: .007%/C , span: ..015%/015%/C C •• Mux’dMux’d pulsed & regulated bridge excitationpulsed & regulated bridge excitation•• Mux dMux d, pulsed & regulated bridge excitation, pulsed & regulated bridge excitation


Energy consumption:Energy consumption:Energy consumption:Energy consumption:

work to balance thework to balance thework to balance the work to balance the “energy checkbook”“energy checkbook”gygy


Powering down between Powering down between ggsamples greatly reduces samples greatly reduces power consumptionpower consumptionpower consumptionpower consumption


Embedded routines allowEmbedded routines allowEmbedded routines allowEmbedded routines allowmicroelectronics tomicroelectronics to

adapt to adapt to th t f il blth t f il blthe amount of available the amount of available

energyenergyenergy energy


Pitch Link Operating Modes:Pitch Link Operating Modes:Pitch Link Operating Modes:Pitch Link Operating Modes:

M d 1 R l Ti T i iM d 1 R l Ti T i i D t l d tD t l d t•• Mode 1: Real Time Transmission: Mode 1: Real Time Transmission: Data logged at Data logged at specified rate, after 100 specified rate, after 100 samples, system transmits. samples, system transmits. Consumption @ Consumption @ 32 samples/sec: ~250 32 samples/sec: ~250 uwattsuwatts..

•• Mode 2: Real Time Transmission Mode 2: Real Time Transmission w/ Energy w/ Energy Awareness:Awareness: DataData logged at specified rate after 100logged at specified rate after 100Awareness: Awareness: Data Data logged at specified rate, after 100 logged at specified rate, after 100 samples, samples, system checks stored system checks stored energy, energy, transmits transmits if if possible. possible. Consumption @ 32 samples/sec: ~250 Consumption @ 32 samples/sec: ~250 uWuW drops as conditions dictatedrops as conditions dictateuWuW, drops as conditions dictate., drops as conditions dictate.


Pitch Link Operating Modes (con’t):Pitch Link Operating Modes (con’t):Pitch Link Operating Modes (con t):Pitch Link Operating Modes (con t):•• Mode 3: Real Time Data Logging: Mode 3: Real Time Data Logging: Data logged to memory Data logged to memory

f d l d t th d f t tf d l d t th d f t t C ti @ 32C ti @ 32for download at the end of test. for download at the end of test. Consumption @ 32 Consumption @ 32 samples/sec: ~100 samples/sec: ~100 uwattsuwatts

•• Mode 4: Data Transmission When Stored Energy Sufficient: Mode 4: Data Transmission When Stored Energy Sufficient: When output capacitor voltage crosses threshold, When output capacitor voltage crosses threshold, nanonano--amp comparator turns circuit on & predetermined amount amp comparator turns circuit on & predetermined amount of data are transmitted This differs from Mode 2 asof data are transmitted This differs from Mode 2 asof data are transmitted. This differs from Mode 2 as of data are transmitted. This differs from Mode 2 as system consumes no power until sufficient energy has system consumes no power until sufficient energy has been stored. been stored. Consumption varies with available energy, Consumption varies with available energy, timekeeper draws 9 microwattstimekeeper draws 9 microwattstimekeeper draws 9 microwatts.timekeeper draws 9 microwatts.


Harvesting gEnergygy

Harvesting Strain EnergyHarvesting Strain Energyg gyg gy

•• Macro Fiber Composite, P2 type Macro Fiber Composite, P2 type p , ypp , yp(Smart Material Corp., Sarasota, (Smart Material Corp., Sarasota, FL)FL)

•• Ongoing PZT fatigue testing: OK Ongoing PZT fatigue testing: OK after 10 billion cycles after 10 billion cycles ( 9 t 30 H )( 9 t 30 H )(>9 years at 30 Hz)(>9 years at 30 Hz)

•• 4 point bending fixture delivers4 point bending fixture delivers4 point bending fixture delivers 4 point bending fixture delivers uniform strain field to PZTuniform strain field to PZT

•• PZT p t h e 3” 1”PZT p t h e 3” 1”•• PZT patch area: 3” x 1” PZT patch area: 3” x 1” © microstrain, inc. 2008

Tuned vibration harvesterTuned vibration harvesterTuned vibration harvesterTuned vibration harvester

Enclosure

Vibrating Structure

xz

EnclosurePZT Elements

Cantilever Beam SpringBaseProof Mass


FEAFEA modelpredicts resonant frequency&&strain levels

Actual FEA

Resonant Frequency (Hz)

81 80.8

Strain on PZT 220 250Strain on PZT elements (µε)

220 250


MicroStrain’s wireless pitch link pfor Bell M412 (patent pending)

Electronics Module: 8.2 gr

PZT total weight: 4.3 gr/patch x g g /p12 patches = 52 gr

Cold shrink weight: 7 gr/inch x 8 inches = 56 gr7 gr/inch x 8 inches = 56 gr(Bell chose clamps w/ counter-balance)


M412 Pitch Link, 5 Hz sine input M412 Pitch Link, 5 Hz sine input PZT t t l dPZT t t l dPZT power output vs. load PZT power output vs. load

(measured at output storage cap)(measured at output storage cap)


Energy generation with Energy generation with replicated dynamic loadsreplicated dynamic loads

•• Max load (VNE dive test): Max load (VNE dive test): 34 34 uWuW/patch * 12 patches = 408 /patch * 12 patches = 408 uWuWcan log data at 128 Hzcan log data at 128 Hzgg

•• Low load (Straight & level flight): Low load (Straight & level flight): 2525 uWuW/patch * 12 patches = 300/patch * 12 patches = 300 uWuW25 25 uWuW/patch * 12 patches = 300 /patch * 12 patches = 300 uWuWcan log data at 90 Hzcan log data at 90 Hz

l d d dl d d d•• Replicated dynamic input generated ~40% more power Replicated dynamic input generated ~40% more power than sine input than sine input

•• Aircraft was not fully loaded due to budget constraintsAircraft was not fully loaded due to budget constraints© microstrain, inc. 2008

Measuring Strain:Measuring Strain:Measuring Strain:Measuring Strain:

Wireless vs. Wireless vs. Hard WiredHard Wired

Lockheed Martin Aerospace (LMA)Lockheed Martin Aerospace (LMA)F/AF/A 22 T ti F22 T ti FF/AF/A--22 Testing Frame22 Testing Frame


Lockheed Martin Aerospace Lockheed Martin Aerospace Acc ac TestsAcc ac TestsAccuracy Tests: Accuracy Tests: Hard Wired vs. Wireless StrainHard Wired vs. Wireless Strain(Baldwin Precision Calibrator used for strain input)(Baldwin Precision Calibrator used for strain input)

•• HBM MGCpl sHBM MGCpl s Wireless vs. Hard-Wired Correlation y = 1 0002x + 1 1267•• HBM MGCplus HBM MGCplus ®®

vs. MicroStrain vs. MicroStrain VV--Link Link ®®

•• Each systemEach system

Wireless vs. Hard Wired Correlation y = 1.0002x + 1.1267R2 = 1

6000

7000

8000

stra

in)

•• Each system Each system provided bridge provided bridge excitation excitation

•• R^2=1R^2=13000

4000

5000

ss V

-Lin

k (m

icro

s

•• R^2=1R^2=1•• Max wireless Max wireless

error: 2.5 error: 2.5 ustrainustrain

0

1000

2000

0 1000 2000 3000 4000 5000 6000 7000 8000

Wire

les

ustrain ustrain Hard-wired HBM MGCplus (microstrain)


Wired vs. Wireless Gauge Comparison on

S O 8 C l dDSTO F-18 Center Barrel Test Bed

• Two wireless SG-Links sampled at 10 Hz

• DSTO wired system collectedsystem collected data at peaks

• Time synchronized at beginning and end of test


DSTO F-18 Center Barrel Test Bed


DSTO F-18 Center Barrel Test Bed

(mic

rost

rain

)(


(microstrain)

Flight TestFlight TestFlight Test Flight Test ResultsResults

Bell M412 Flight TestBell M412 Flight TestBell M412 Flight TestBell M412 Flight Test


Flight Test ResultsFlight Test ResultsFlight Test ResultsFlight Test Results

•• Energy harvesting wireless pitch link was Energy harvesting wireless pitch link was installed on a Bell Model 412 experimental installed on a Bell Model 412 experimental

t ft & fli ht t t d t B ll’ X X f ilitit ft & fli ht t t d t B ll’ X X f ilitirotorcraft & flight tested at Bell’s XworX facilities rotorcraft & flight tested at Bell’s XworX facilities (Fort Worth, Texas) in Feb 2007.(Fort Worth, Texas) in Feb 2007.

•• Tests included ground and inTests included ground and in--flight EMI flight EMI evaluations rotor track and balance verificationevaluations rotor track and balance verificationevaluations, rotor track and balance verification, evaluations, rotor track and balance verification, & data collection during scripted flight.& data collection during scripted flight.


Bell M412 FlightBell M412 Flight Test Results (Test Results (con’tcon’t):):Bell M412 Flight Bell M412 Flight Test Results (Test Results (con tcon t):):

ll d l l b d hll d l l b d h•• Data were collected wirelessly on board the Data were collected wirelessly on board the aircraft with no indication of data lossaircraft with no indication of data loss

•• Data were also collected Data were also collected external to the aircraft external to the aircraft during ground operations at various locationsduring ground operations at various locationsduring ground operations at various locations during ground operations at various locations around the aircraft around the aircraft (up to 50 ft away)(up to 50 ft away)


Bell M412 Wired Bell M412 Wired vs. Wireless vs. Wireless Pitch Link Flight Test DataPitch Link Flight Test DataPitch Link Flight Test DataPitch Link Flight Test Data

Wireless PitchLink LoadsVNE dive test Flight Record #36

64 Hz wireless sensor sample rate - 500 Hz slip ring sample rate

1

1.5

0.5

aliz

ed)

-0.5

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Out

put (

Nor

ma

-1

500 Hz Slip Ring64 Hz Wireless

-1.5

Time


MicroStrainMicroStrain, Inc. High Sample Rate Bench Test:, Inc. High Sample Rate Bench Test:hardhard--wiredwired reference bridge vs. wireless pitch linkreference bridge vs. wireless pitch linkhardhard wired wired reference bridge vs. wireless pitch linkreference bridge vs. wireless pitch link

(two separate & distinct strain gauge bridges bonded to a single steel plate in 4(two separate & distinct strain gauge bridges bonded to a single steel plate in 4--pt bending)pt bending)

ostr

ain

)St

rain

(m

icro


ConclusionsConclusions

•• An energy harvesting wireless pitch link loadAn energy harvesting wireless pitch link load

ConclusionsConclusions

•• An energy harvesting wireless pitch link load An energy harvesting wireless pitch link load sensor Bell 412 has been developed, bench sensor Bell 412 has been developed, bench tested, & flight testedtested, & flight tested

•• Under extremely low usage levels, the amount Under extremely low usage levels, the amount f t d d th t ff t d d th t fof energy generated exceeds the amount of of energy generated exceeds the amount of

energy consumedenergy consumed

•• This enables an onThis enables an on--board wireless load sensor board wireless load sensor to operate perpetually without battery to operate perpetually without battery p p p y yp p p y ymaintenance. maintenance.


References:References:•• M.J. Hamel et al., Energy Harvesting for Wireless Sensor Operation and Data M.J. Hamel et al., Energy Harvesting for Wireless Sensor Operation and Data

Transmission, Transmission, US Patent Appl. Publ. US 2004/0078662A1, filed March US Patent Appl. Publ. US 2004/0078662A1, filed March 20032003

D L Ch hill l S i E H i f Wi l S N k• D.L. Churchill et al., Strain Energy Harvesting for Wireless Sensor Networks, Smart Structures and Materials, SPIE, vol. 5005, pp. 319–327, 2003

•• S.W. Arms et al., Shaft Mounted Energy Harvesting System for Wireless S.W. Arms et al., Shaft Mounted Energy Harvesting System for Wireless dd l bll bl

g gg gSensor Operation and Data Transmission, Sensor Operation and Data Transmission, US Patent Appl. Publ. US US Patent Appl. Publ. US 2005/0017602A1, filed Jan 2004 2005/0017602A1, filed Jan 2004

• S.W. Arms et al., Wireless Strain Measurement Systems for Aircraft TestWireless Strain Measurement Systems for Aircraft Test, , yy ,Aerospace Test Expo, Anaheim, CA, Nov 2006

• S.W. Arms et al., Energy Harvesting Wireless Sensors for Helicopter Damage Tracking, American Helicopter Society Annual Forum, Phoenix, AZ, May 2006g, p y , , , y

•• S.W. Arms, C.P. Townsend, D.L. Churchill, M. S.W. Arms, C.P. Townsend, D.L. Churchill, M. AugustinAugustin, , D.YearyD.Yeary, P. Darden, , P. Darden, N. Phan, N. Phan, Tracking Pitch Link Dynamic Loads with Energy Harvesting Wireless Tracking Pitch Link Dynamic Loads with Energy Harvesting Wireless SS AHS 63 d A l F Vi i i B h VA M 2007AHS 63 d A l F Vi i i B h VA M 2007Sensors, Sensors, AHS 63nd Annual Forum, Virginia Beach, VA, May 2007AHS 63nd Annual Forum, Virginia Beach, VA, May 2007

Acknowledgements:Acknowledgements:Acknowledgements:Acknowledgements:

NAVAIR SBIR PH II NAVAIR SBIR PH II ONR BAAONR BAAONR BAA ONR BAA

DSTODSTOBell HelicopterBell HelicopterBell HelicopterBell Helicopter

Sikorsky HelicopterSikorsky HelicopterLockheed MartinLockheed MartinLockheed MartinLockheed Martin

Thank You!Thank You!

wireless structural healthwireless structural health...

Documents