外文翻译WIM系统中以光纤为基础的动态压力传感装置.docx
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外文翻译WIM系统中以光纤为基础的动态压力传感装置.docx
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外文翻译WIM系统中以光纤为基础的动态压力传感装置
附件外文翻译
Opticfiber-baseddynamicpressuresensorforWIMsystem
ShenfangYuana,
FahardAnsarib,XiaohuiLiuaandYangZhaob
aTheAeronauticalKeyLaboratoryforSmartMaterialsandStructures,NanjingUniversityofAeronauticsandAstronautics,29YuDaoStreet,Nanjing210016,China
bDepartmentofCivilandMaterialsEngineering,UniversityofIllinoisatChicago,Illinois,IL60607,USA
Received16August2004;
accepted10November2004.
Availableonline15December2004.
Abstract
Anopticfiber-baseddynamicpressuresensorisdescribedheretomeasureweight-in-motionofvehicles.Intheresearchreportedherein,aMichelsoninterferometerwithspeciallydesignedhardwareandsoftwareweredevelopedandexperimentallysubjectedtodynamiccompressiveloadsofdifferentmagnitudes,andloadingrates.Experimentsshowedthatbothoutputfringenumberandfringeperiodcouldbeusedtoindicatethedynamicload.Acalibrationtechniquehasbeenputforwardtocalibratethesensor.Boththedynamicweightandstaticweightofthevehiclepassedcanbeobtained.Thefindingsthatresultedfromthesestudiesdevelopedanunderstandingforthebehaviorofinterferometersensorunderdynamiccompressivestatesofstressandarefundamentaltotheapplicationoffiberopticsensorsforthemonitoringoftruckvehicleweightswhileinmotion.
Keywords:
Opticfibersensor;Dynamicpressure;Weight-in-motion;Hardwareandsoftware
ArticleOutline
1.Introduction
2.Thesensordesign
2.1.Sensorsetup
2.2.Sensorprinciple
3.Experimentalproceduresandresults
3.1.Experimentalsetup
3.2.Experimentaldata
3.3.Repeatabilityofthesensor
3.4.Calibrationofthesensor
3.4.1.Calibrationofthestaticweight
3.4.2.Calibrationofthedynamicweight
4.Conclusion
References
Vitae
1.Introduction
Theneedtoweighvehiclesinmotion,appliedespeciallytotrafficcontrol,hasgrownsubstantiallyinthepastdecades.Severaltechniquesforweightingvehiclesin-motionarenowusedincludingpiezoelectriccables,capacitivemats,hydraulicandbending-plateloadcells[1].Hydraulicandbending-plateloadcellsofferhighaccuracy(1–5%)anddynamicrange,yetsufferfromhighinstallationcostsandsizeconstraints.Thepiezoelectricandcapacitivemattechniquesaresubstantiallylowerincost,yetarelessaccurate(5–15%)anddonotfunctionproperlyatspeedslowerthan20 km/h[2]and[3].Tooffertherequiredaccuracyatreducedinstallationandmaintenancecosts,opticfiber-basedWIMsensorsarenowbeingdevelopedtoimprove,complementorevenreplacetheonescurrentlyinuse.
Basedontheeffectofpolarizationcouplingbetweentwoorthogonallypolarizedeigenmodesofpolarization-maintainingfiber,Ansarietal.reportonusinghighlybirefringencepolarization-maintaining(HiBi)fiberfordynamicmeasurementofpressurewithpracticalramificationstothedeterminationofweigh-in-motionoftrucks[3].NavarreteandBernabeureportamultiplefiber-opticinterferometerconsistingofaMach-ZehnderinterferometerconfigurationwithoneofitsarmsreplacedbyanotherMach-Zehnderinterferometer[4].CosentinoandGrossmandevelopedadynamicsensorusingthemicrobendtheorytotestweight-in-motion[5].
ThepresentworkdescribesthedevelopmentofadynamicpressuresensorbasedontheMichelsoninterferometer,whichhassimplestructure,iscosteffectiveandcanpotentiallyofferthehighaccuracyrequiredformanyapplications.SpecialhardwareandsystemsoftwarebasedonLabviewWINDOWS/CVIaredesignedtoimplementthesensorfunctions,suchaseliminatingenvironmentalnoise,self-triggeringofthetestprocedureandthefringenumberandfringeperiodsimultaneouscount.Responsesofthedynamicsensorarestudiedwhensubjectedtodynamiccompressiveloadswithdifferentmagnitudesandloadingrates.Datacalibrationmethodisalsoresearchedtocalibratethesensor.
2.Thesensordesign
2.1.Sensorsetup
Fig.1illustratesschematicallytheproposeddynamicpressuresensorsystem.Single-modeopticalfiberisusedasasensingelementtoformaMichelsoninterferometer.Theoptoelectronicscomponentsoftheinterferometerconsistofalaseroperatingatwavelengthof1550 nm,alaserisolatorandaphotodiode.Thesensorismadeofcommunicationgradeopticalfiber(CorningSMF28).Theoutputsignalfromthedetector-amplifierisfirstfedtoaspecialhardwarecircuitsincludingatwo-orderhighpassfilter,azero-pointdetectioncircuitandaSchmittTriggercircuit.Thehardwarecircuitsaredesignedtoimplementthefollowingfunctions:
(1)self-diagnosethearrivaltimeofthevehicletoself-triggerthemeasurementprocess;
(2)providefunctiontoeliminatethelowfrequencydisturbances,suchastemperatureinfluencesandslowchangesoftheelement'sperformances;(3)providefunctiontoreducethenoisetoafrequencybandsimilartotheusefulfringeoutputoftheMichelsoninterferometer.Onepossiblesourceofthisnoiseiscausedbyvehiclespassinginanear-bylane.SincetheoutputoftheMichelsoninterferometerunderpressureisfringewhichcanbeconsideredashighfrequencysignalcomparingtothenoisecausedbytemperaturechanges,laseranddiodeperformancechangeandotherlowfrequencyenvironmentalinfluences,atwo-orderhighpassfilterwasadoptedtoeliminatethoselowfrequencycomponents.Azero-pointdetectioncircuitisdesignedtochangethesine-formfringetopulsesignalforthecounterinthecomputerdataacquisitionsystemtocountthefringenumberandmeasurethefringeperiod.Theself-triggerfunctionisaccomplishedbytheSchmittcircuit.ThethresholdvoltageoftheSchmittcircuitissetaccordingtoexperimentstodistinguishtherealfringesignalcausedbyvehiclesandthepseudofringesignalcausedbysmallvibrationinthetestenvironment.Inpracticalapplication,thiscouldbecausedbythepassingvehiclesinadjoininglanes.SystemsoftwarebasedonLabviewWindows/CVIisdesignedtosetmeasurementparameters,controlthetestprocedureanddisplayresults.
Full-sizeimage(14K)
Fig.1. Dynamicfiberopticpressuresensorsetup.
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2.2.Sensorprinciple
OnearmoftheMichelsoninterferometerissubjectedtoadistributingdynamicloadLd(t).Thegeneralizedstress–opticrelationshipbetweentheopticalpathchangeΔlandthestrain
inducedoverthegaugelengthcanbederivedasEq.
(1)[6]:
(1)
and
(2)
whereP11andP12arethePockelsconstant;lthelength(gaugelength)oftheopticalfiberwithinthepressurefield;tx,tyandtzcorrespondtothemechanicalandgeometricalpropertyoftheopticalfiberandthehostmaterial-epoxy.
Bymeasuringthedeformationofthefiber,thestraininthehostmaterialcanbemeasured.Thestrainislinearlyproportionaltotheexternalappliedpressurep.ConsiderαasaconstantofproportionalitybetweenthepressureandthechangeinlengthofthefiberΔl,then
(3)
and
(4)
Thus,theoutputfringenumberoftheMichelsoninterferometeris
(5)
whereNfistheoutputfringenumber;λthewavelengthofthelaserlight.
ThefringeperiodcanbededucedbyEq.(6):
(6)
whereTfisthefringeperiod;ttheloadingtime,approximatelyequaltothedurationtimeoftheopticfiberfringe.
3.Experimentalproceduresandresults
3.1.Experimentalsetup
TheexperimentalsetupisshowninFig.2.Asteelchamberisdesignedtocontaintheopticalfiber.Theopticfiberissandwichedbetweentwo1 cmthickstiffrubberpadsandgluedtooneofthetwopieces.Rubberpadsarenecessaryfortheprotectionoffiberfromdamage.Thecross-sectionalareaoftheloadingsurfaceforthesteelchamberis247.1 mm × 24 mm.Thegaugelengthoftheopticalfiberpressuresensoris247.1 mm.Aclosed-loopmaterialstestingsystem(MTS)isusedfortheapplicationofpressure.Rampfunctionloadwithdifferentloadingratesandmagnitudesarechosenasdynamicloadstosimulatetheweightloadscausedbymovingvehiclesonroad.
Full-sizeimage(45K)
Fig.2. Experimentalsetup.
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Fig.3showsatypicalloadingprofileandfringeoutputoftheinterferometerduringthedurationoftheappliedrampfunctionload.Ascanbeseen,thenumberoffringesatleftcornerofFig.3issogreatthatitishardtodistinguisheachfringe.Thus,anotherfigureontherightisused.Thefigureistheenlargementofthecircledareatoshowclearlythefringes.Becauseofthepolarizationeffect,theamplitudesoffringesslightlyvary.Butwillnotinfluencethefringecountandperiod,thusneglectedinthispaper.Intheexperiment,thepressureloadisappliedtothechamberat7.5 MPaincrementsuptothemaximumpressurelevelof30 MPa,correspondingtoloadincrementsfrom44.5 kNtoamaximumof178 kN.Theloadingtimeisappliedstartingfrom1to6 swithanincrementof1 s.
Full-sizeimage(46K)
Fig.3. Typicalloadingprocedureandfiberopticsensoroutputwaveform.
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3.2.Experimentaldata
Fig.4showstheexperimentalresultsofthefringenumberandfringeperiodreadoutsofthesensoroutputunderdifferentloads.Lineswithdifferentsignsrepresentrelationsbetweenthesensor'soutputsandthemaximumamplitudesoftheloadunderdifferentloadingrates.
Full-sizeimage(33K)
Fig.4. Theexperimentalresults:
thefringenumbersandfringeperiodsvs.loads.
ViewWithinArticle
Thefringenumberhasalinearrelationshipwiththestaticload,whilethefringeperiodhasanon-linearone.Notethat,therelationshipdiffersunderdifferentloadingrates,sincewithincreasingloadingrate,thesamemaximumamplitudeloadwillturnouttoabiggerdynamicload,w
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- 外文 翻译 WIM 系统 光纤 基础 动态 压力 传感 装置