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中英文翻译英语原文APPLICATIONOFDIGITALTECHNIQUESINULTRASONICSENSOR1INTRODUCTIONITISNECESSARYFORANUMBEROFAPPLICATIONSTOPERFORMDISTANCEMEASUREMENTSULTRASONICSENSORSAREASTATEOFTHEARTCHOICETOEFFECTIVELYSOLVETHISPROBLEMINDIFFERENTENGINEERINGFIELDS,SUCHASMEDICALIMAGING,ROBOTNAVIGATION,FLOWVELOCITY,FLUIDLEVELMEASUREMENTANDSOONALTHOUGHDIFFERENTKINDSOFMEASURINGSYSTEMSANDSENSORSHAVEBEENUSEDFORTHESPECIFICAPPLICATIONSRESPECTIVELY,THEREAREPROBLEMSRELATEDTOECHODETECTIONINEVERYCASEATTENUATIONANDBEAMSPREADING,PRESENCEOFNOISEANDINTERFERENCE,SENSITIVITYTOTEMPERATUREANDHUMIDITY,POORRESOLUTIONINMANYAPPLICATIONS,THETIMEELAPSEDBETWEENTHESTIMULUSULTRASONICWAVEANDITSECHOISTAKENASTHEBASISOFTHEMEASUREMENT,THATIS,THEMAINOPERATINGPRINCIPLEISTHEESTIMATIONOFTHETIMEOFFLIGHTTOF,THETRANSMITTINGULTRASONICTRANSDUCERTRANSMITSANULTRASONICPULSE,THEPULSEPROPAGATESTHROUGHTHETRANSMISSIONMEDIUMAIR,WATER,ETCANDISECHOEDBYASUITABLEREFLECTORTHEECHOPULSEISRECEIVEDBYTHERECEIVINGTRANSDUCER,WHICHMAYBETHESAMETRANSMITTINGTRANSDUCERSOTHEDISTANCEFROMTHETRANSMITTERTOTHEREFLECTORCANBEESTIMATEDINDIRECTLYBYTHEFORMULA1WHEREVISTHEPROPAGATIONVELOCITYOFTHEULTRASONICWAVEINTHEMEDIUMANOTHERPRINCIPLEISTHEPHASESHIFTMETHODHERE,THETRANSMITTERGENERATESACONTINUOUSWAVE,WHOISREFLECTEDBYANOBJECT,ANDWHOSEECHOISDETECTEDBYASEPARATERECEIVERBYCOMPUTINGTHEPHASESHIFTBETWEENTHETRANSMITTEDANDTHERECEIVEDCONTINUOUSWAVE,THEDISTANCEISEVALUATEDTOWITHINAWAVELENGTHPULSEECHOANDCONTINUOUSWAVETECHNIQUESAREWIDELYKNOWNASTHEREPRESENTSOFTHETWOMEASURINGPRINCIPLESCONTINUOUSWAVETECHNIQUEISMOREACCURATE,BUTMOREEXPENSIVEDUETOCOMPLEXHARDWAREUSEDTOMEASURETHEPHASEANDDUETOTHEDIFFICULTYINDETERMININGTHENUMBEROFINTEGERWAVELENGTHSASARESULT,THEPULSEECHOTECHNIQUEISOFTENUSEDINCOMMERCIALSYSTEMSFORINDUSTRIALAPPLICATIONTHEREFORE,THISPAPERPUTSANEMPHASISONTHEPULSEECHOTECHNIQUEFROMTHEFORMULA1,WEHAVECONCLUDEDTHATTHOSEFACTORSAFFECTINGVANDTFARETHESOURCESOFTHEDISTANCEMEASUREMENTUNCERTAINTYTHEVARIATIONOFVDOESNTONLYDEPENDONTHERELATIVEHUMIDITYANDTEMPERATURE,BUTALSOONSOMECHEMICALANDPHYSICALPARAMETERSOFTHEFLUIDFORTHESEEFFECTS,DIFFERENTTECHNIQUESHAVEBEENDEVELOPEDSUCCESSFULLYTOCOMPENSATETHEMSATISFACTORILY,SOTHECRITICALPOINTOFTHEWHOLEMEASUREMENTPROCEDUREISTHETOFESTIMATIONMANYMETHODSHAVEBEENPROPOSEDTOIMPROVETHETOFMEASUREMENTACCURACYSOMEREQUIRECOMPLICATED,NOTFLEXIBLEANDVERYEXPENSIVEHARDWARETOMAKETHETOFMEASUREMENTHIGHERACCURACYHOWEVER,OTHERSUSESOPHISTICATEDDIGITALTECHNIQUES,THATIS,DIGITALSIGNALPROCESSINGSOFTWARETODOTHESAMETHINGFROMTHEVIEWPOINTOFTHEENGINEERINGAPPLICATION,ITISNOTONLYPOSSIBLE,BUTALSOFEASIBLETOIMPROVETOFESTIMATIONUSINGDIGITALTECHNIQUESINTHISPAPER,FIRSTLY,THEBASICTHEORIESOFTHESEDIGITALTECHNIQUESAREPRESENTED,INCLUDINGSOMEMATHEMATICALFORMULATHEN,THEAPPLICATIONSOFTHESEDIGITALTECHNIQUESFORTHEULTRASONICDISTANCEMEASUREMENTISDESCRIBEDFINALLY,AOBJECTIVEASSESSMENTOFTHEMETHODSTHROUGHANALYZINGBOTHTHESYSTEMATICANDRANDOMERRORSISGIVEN2SIGNALMODELANDITSBUILDINGASFORTHEPULSEECHOMETHOD,INTHEMOSTENGINEERINGAPPLICATIONS,REQUIREONLYONETRANSDUCERASBOTHTHETRANSMITTERANDRECEIVERTHATISITOFFERSASIMPLEANDLOWCOSTSOLUTIONBUTATTHESAMETIME,ITMAYRESULTINLOWACCURACYOWINGTOTHEERROROFTHETOFESTIMATIONHOWTOIMPROVEITSACCURACYBUTNOTUSECOMPLEX,EXPENSIVEADDITIONALHARDWAREINFACT,THISPROBLEMCANBESOLVEDBYUSINGCHEAPSOFTWARESIGNALPROCESSINGTHEREFORE,THEKEYOFTHISPROBLEMISOFCOURSE,THETOFESTIMATIONTOSOLVETHISPROBLEM,ITISNECESSARYTOSETUPASUITABLEMATHEMATICALMODELOFTHETRANSMITTEDULTRASONICPULSE2WHEREAS,FSANDΨSARETHESIGNALAMPLITUDE,FREQUENCYANDPHASERESPECTIVELY,WHILEMANDNARETHEPARAMETERSOFTHECHARACTERSOFULTRASONICTRANSDUCERITSELFFORTHEACTUALTRANSDUCER,BOTHM0ANDU0ISANABSOLUTEFACTATTHESAMETIME,ASUITABLEMATHEMATICALMODELOFTHEREFLECTEDULTRASONICPULSEMUSTBECONSIDEREDTOBEWRITTENASFOLLOWSETARTTFTETTSLUCOS2XFSTTFΨR3WHEREAR,ΨRARETHEAMPLITUDEANDTHEPHASEOFTHEREFLECTEDECHOSIGNALTFISTHETOFTOPERFORMTOFMEASUREMENT,WEMUSTCONSIDERTHEMODELOFTHEWHOLEULTRASONICSIGNAL,INCLUDINGBOTHTHETRANSMITTEDANDTHEREFLECTEDPULSE,WHICHCANBEREPRESENTEDBYTHEEQUATION（4）WHERE0TAND0FARETHESAMPLINGPERIODSFORTHETIMEANDFREQUENCYDOMAINRESPECTIVELY,ANDKN,AREINTEGERSAFTERSTFTHASMAPPEDAONEDIMENSIONALSIGNALOFTIMEXT,ONTOATWODIMENSIONALFUNCTIONOFTIMEANDFREQUENCY,FTX,WHATWEDONEXTISTHEENVELOPEEXTRACTIONTHEFIRSTSTEPISTOCHOOSEASUITABLEFREQUENCYSFWHENUSINGTHEFREQUENCYSF,S/NISTHEMAXIMUMANDTHEINTERFERENCEISTHEMINIMUM,WHICHALWAYSBETHERESONANTFREQUENCYOFTHESENSORTHESECONDSTEPISTOFINDOUTTHEMAGITUDEFUNCTIONOFTHESTFTATTHEFREQUENCYSFOFTHESIGNALXT,THATISTHEENVELOPEWENEED3CORRELATIONMETHODANDTOFESTIMATIONAFTERRECOVERINGTHEENVELOPEFROMTHEDISTORTEDANDNOISYNONSTATIONARYSIGNALTHENEXTWORKISTOCOMPLETETHETOFESTIMATIONSEVERALTECHNIQUESCANBEUSEDTOACCOMPLISHTHETASKOFTHETOFESTIMATIONTHETRADITIONALAPPROACHUSEDINTHEMOSTULTRASONICSENSORSISTHETHRESHOLDMETHODATHRESHOLDLEVELISSETTLED,ANDTHETOFISCONSIDEREDTOBEMEASUREDWHENTHETHRESHOLDISFIRSTEXCEEDEDBYTHESIGNALORITSENVELOPEALTHOUGHITHASPROVEDTOBESIMPLEANDCHEAP,THISTECHNIQUEMAYSUFFERFROMPOORRESOLUTION,PARTICULARLYTHEECHOPULSEHASBEENGREATLYATTENUATEDTHECORRELATIONTECHNIQUEISAKINDOFMORESOPHISTICATEDTECHNIQUEFORAPPLICATIONSREQUIRINGHIGHACCURACY,WHICHBASESTHETOFESTIMATIONONTHESEARCHOFTHERELATIVEMAXIMUMINTHECROSSCORRELATIONFUNCTIONBETWEENTHETRANSMITTEDSIGNALANDTHEECHOSIGNALACCORDINGTOTHEINDEXOFTHEMAXIMUMVALUEOFTHECORRELATIONFUNCTION,THETIMEDELAYBETWEENTHETWOSIGNALSISOBTAINEDTHECORRELATIONFUNCTIONISDEFINEDAS5WHENTHEVALUEOFHTCISTHEMAXIMUM,THETOFISHT6CONSIDERINGTHEPROCEDUREOFTHESAMPLINGDATA,ACTUALLY,THEFTESTIMATIONCANBEEXPRESSEDINTHEFORM7WHEREHISTHEINTEGERPARTOF50/TTF,ANDΛISAREALNUMBERINTHEINTERVAL50,50,ASUITABLEMEASUREMENTALGORITHMMUSTBEUSEDTOEVALUATEEXACTLYTHEREALNUMBERΛITISPOSSIBLETOESTIMATIONTHEFRACTIONNUMBERΛTHROUGHASUITABLEINTERPOLATIONTECHNIQUETHESECONDORDERAPPROXIMATEINTERPOLATIONDETERMINESTHEPARAMETERΛAS8THEEQUATION1CANBEEXPRESSEDAS94SIMULATIONANDERRORANALYSISINORDERTOVALIDATETHEPROPOSEDMETHOD,AREALISTICSIMULATIONMUSTBESETUPTOMIRRORTHECHARACTERSOFANACTUALULTRASONICSENSORASSUMINGASAMPLINGFREQUENCYMF8MHZ,ANULTRASONICSENSORFREQUENCYFS550KHZ,ANULTRASONICWAVESPEEDINTHEMEDIUMSMV/1390,THEDISTANCERESOLUTIONIS,ACCORDINGTOTHEEQUATION1,0087MMTHEERRORANALYSISCANBEIMPLEMENTEDONTHECOMPUTERSIMULATIONS41SYSTEMATICCOMPONENTOFERRORSINTOFESTIMATIONTHEFINITESAMPLINGFREQUENCYDURINGTHEPROCEDUREOFTHEA/DCONVERSIONMAKETHETOFESTIMATIONINACCURATE,THATIS,THETIMERESOLUTIONERROROFSYSTEMISAERRORSOURCEFORTHETOFESTIMATIONTHISISASYSTEMATICERROR,WHICHCANBETHOUGHTASAFUNCTIONOFTHETIMERESOLUTIONFROMTHEEQUATION5,THISIDEALRESOLUTIONERRORCANBEWRITTENAS10THATCORRESPONDSTOAMAXIMUMDISTANCEERROREQUALTOMM0430WHENTHETOFISAMULTIPLEOFTHESAMPLINGPERIODΛ,THEERRORWILLBEZEROACCORDINGTOTHEEQUATION6,THERESULTOBTAINEDBYCOMPUTERSIMULATIONSCONFIRMTHATTHEINTERPOLATIONMETHODMAKETHETIMERESOLUTIONERRORTOAMINIMUMVALUEASARESULT,THESYSTEMATICERRORINDISTANCEMEASUREMENTCANBEWRITTENASFOLLOWS1142RANDOMCOMPONENTOFERRORSINTOFESTIMATIONINTHEPRACTICALAPPLICATIONS,THEEXISTENCEOFNOISEISACAUSEOFTOFINACCURACYWECANASSUMETHATTHENOISEISAWHITENOISEFROMTHEVIEWPOINTOFENERGY,LOWSNRLEADSTOHIGHNOISEINTENSITYFORTHECORRELATIONMETHOD,ITISLESSSENSITIVETONOISEDUETOTHEINHERENTCANCELLATIONOFZEROMEANRANDOMEFFECTSITSELF5CONCLUSIONSTHEUSEOFDEDICATEDDIGITALTECHNIQUESPROVEDTOBEESSENTIALFORULTRASONICSENSORSASUITABLEMEASUREMENTPROCEDUREHAVEBEENSETUPALLOWINGTHEPERFORMANCEOFTHEPROPOSEDTECHNIQUESWITHREGARDTOENVELOPEEXTRACTION,THESTFTISAGOODCHOICETHESTFTFILTEROUTTHENOISE,ANDRECOVERTHEOPTIMIZEDENVELOPE,THECORRELATIONMETHODISBETTERTHANTHETHRESHOLDMETHODDUETOBETTERPERFORMANCEBOTHINTERMSOFSYSTEMATICERRORTIMERESOLUTIONANDINTERMSOFRANDOMERRORNOISEFORECHODETECTIONACKNOWLEDGMENTS
