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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.
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
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.
•• 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
•• 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
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
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
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
•• 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..
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
•• 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
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: :
Powering down between Powering down between ggsamples greatly reduces samples greatly reduces power consumptionpower consumptionpower consumptionpower consumption
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.
•• 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
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
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
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)
•• 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