超声波测距仪毕业论文外文文献翻译及原文.docx

超声波测距仪毕业论文外文文献翻译及原文.docx

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毕业设计（论文）外文文献翻译

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翻译日期：

2017.02.14

英文文献翻译

Ultrasonicdistancemeter

超声波测距仪

文献来源：

UnitedStatesPatent5442592

作者：

Lobo,IanJ.（罗保.伊恩j.）

Ultrasonicdistancemeter

Abstract:

Anultrasonicdistancemetercancelsouttheeffectsoftemperatureandhumidityvariationsbyincludingameasuringunitandareferenceunit.Ineachoftheunits,arepetitiveseriesofpulsesisgenerated,eachhavingarepetitionratedirectlyrelatedtotherespectivedistancebetweenanelectroacoustictransmitterandanelectroacousticreceiver.Thepulsetrainsareprovidedtorespectivecounters,andtheratioofthecounteroutputsisutilizedtodeterminethedistancebeingmeasured.

一、 BACKGROUNDOFTHEINVENTION

Thisinventionrelatestoapparatusforthemeasurementofdistanceand,moreparticularly,tosuchapparatuswhichtransmitsultrasonicwavesbetweentwopoints.

Precisionmachinetoolsmustbecalibrated.Inthepast,thishasbeenaccomplishedutilizingmechanicaldevicessuchascalipers,micrometers,andthelike.However,theuseofsuchdevicesdoesnotreadilylenditselftoautomationtechniques.Itisknownthatthedistancebetweentwopointscanbedeterminedbymeasuringthepropagationtimeofawavetravellingbetweenthosetwopoints.Onesuchtypeofwaveisanultrasonic,oracoustic,wave.Whenanultrasonicwavetravelsbetweentwopoints,thedistancebetweenthetwopointscanbemeasuredbymultiplyingthetransittimeofthewavebythewavevelocityinthemediumseparatingthetwopoints.Itisthereforeanobjectofthepresentinventiontoprovideapparatusutilizingultrasonicwavestoaccuratelymeasurethedistancebetweentwopoints.

Whenthemediumbetweenthetwopointswhosespacingisbeingmeasuredisair,thesoundvelocityisdependentuponthetemperatureandhumidityoftheair.Itisthereforeafurtherobjectofthe,presentinventiontoprovideapparatusofthetypedescribedwhichisindependentoftemperatureandhumidityvariations.

二、 SUMMARYOFTHEINVENTION

Theforegoingandadditionalobjectsareattainedinaccordancewiththeprinciplesofthisinventionbyprovidingdistancemeasuringapparatuswhichincludesareferenceunitandameasuringunit.Thereferenceandmeasuringunitsarethesameandeachincludesanelectroacoustictransmitterandanelectroacousticreceiver.Thespacingbetweenthetransmitterandthereceiverofthereferenceunitisafixedreferencedistance,whereasthespacingbetweenthetransmitterandreceiverofthemeasuringunitisthedistancetobemeasured.Ineachoftheunits,thetransmitterandreceiverarecoupledbyafeedbackloopwhichcausesthetransmittertogenerateanacousticpulsewhichisreceivedbythereceiverandconvertedintoanelectricalpulsewhichisthenfedbacktothetransmitter,sothatarepetitiveseriesofpulsesresults.Therepetitionrateofthepulsesisinverselyrelatedtothedistancebetweenthetransmitterandthereceiver.Ineachoftheunits,thepulsesareprovidedtoacounter.Sincethereferencedistanceisknown,theratioofthecounteroutputsisutilizedtodeterminethedesireddistancetobemeasured.Sincebothcountsareidenticallyinfluencedbytemperatureandhumidityvariations,bytakingtheratioofthecounts,theresultantmeasurementbecomesinsensitivetosuchvariations.

三、DETAILEDDESCRIPTION

Referringnowtothedrawing,thereisshownameasuringunit10andareferenceunit12,bothcoupledtoautilizationmeans14.Themeasuringunit10includesanelectroacoustictransmitter16andanelectroacousticreceiver18.Thetransmitter16includespiezoelectricmaterial20sandwichedbetweenapairofelectrodes22and24.Likewise,thereceiver18includespiezoelectricmaterial26sandwichedbetweenapairofelectrodes28and30.Asisknown,byapplyinganelectricfieldacrosstheelectrodes22and24,stressisinducedinthepiezoelectricmaterial20.Ifthefieldvaries,suchasbytheapplicationofanelectricalpulse,anacousticwave32isgenerated.Asisfurtherknown,whenanacousticwaveimpingesuponthereceiver18,thisinducesstressinthepiezoelectricmaterial26whichcausesanelectricalsignaltobegeneratedacrosstheelectrodes28and30.Althoughpiezoelectrictransducershavebeenillustrated,otherelectroacousticdevicesmaybeutilized,suchas,forexample,electrostatic,electretorelectromagnetictypes.

Asshown,theelectrodes28and30ofthereceiver18arecoupledtotheinputofanamplifier34,whoseoutputiscoupledtotheinputofadetector36.Thedetector36isarrangedtoprovideasignaltothepulseformer38whentheoutputfromtheamplifier34exceedsapredeterminedlevel.Thepulseformer38thengeneratesatriggerpulsewhichisprovidedtothepulsegenerator40.Inordertoenhancethesensitivityofthesystem,thetransducers16and18areresonantlyexcited.Thereisaccordinglyprovidedacontinuouswaveoscillator42whichprovidesacontinuousoscillatingsignalatafixedfrequency,preferablytheresonantfrequencyofthetransducers16and18.Thisoscillatingsignalisprovidedtothemodulator44.Toeffectivelyexcitethetransmitter16,itispreferabletoprovideseveralcyclesoftheresonantfrequencysignal,ratherthanasinglepulseorsinglecycle.Accordingly,thepulsegenerator40isarranged,inresponsetotheapplicationtheretoofatriggerpulse,toprovideacontrolpulsetothemodulator44havingatimedurationequalthetimedurationofapredeterminednumberofcyclesoftheoscillatingsignalfromtheoscillator42.Thiscontrolpulsecausesthemodulator44topassa"burst"ofcyclestoexcitethetransmitter16.

Whenelectricpowerisappliedtothedescribedcircuitry,thereissufficientnoiseattheinputtotheamplifier34thatitsoutputtriggersthepulsegenerator40tocauseaburstofoscillatingcyclestobeprovidedacrosstheelectrodes22and24ofthetransmitter16.Thetransmitter16accordinglygeneratesanacousticwave32whichimpingesuponthereceiver18.Thereceiver18thengeneratesanelectricalpulsewhichisappliedtotheinputoftheamplifier34,whichagaincausestriggeringofthepulsegenerator40.Thiscyclerepeatsitselfsothatarepetitiveseriesoftriggerpulsesresultsattheoutputofthepulseformer38.Thispulsetrainisappliedtothecounter46,aswellastothepulsegenerator40.

Thetransmitter16andthereceiver18arespacedapartbythedistance"D"whichitisdesiredtomeasure.Thepropagationtime"t"foranacousticwave32travellingbetweenthetransmitter16andthereceiver18isgivenby:

t=D/VswhereVsisthevelocityofsoundintheairbetweenthetransmitter16andthereceiver18.Thecounter46measurestherepetitionrateofthetriggerpulses,whichisequalto1/t.Therefore,therepetitionrateisequaltoVs/D.Thevelocityofsoundinairisafunctionofthetemperatureandhumidityoftheair,asfollows:

##EQU1##whereTisthetemperature,pisthepartialpressureofthewatervapor,Histhebarometricpressure,rwandraaretheratioofconstantpressurespecificheattoconstantvolumespecificheatforwatervaporanddryair,respectively.Thus,althoughtherepetitionrateofthetriggerpulsesismeasuredveryaccuratelybythecounter46,thesoundvelocityisinfluencedbytemperatureandhumiditysothatthemeasureddistanceDcannotbedeterminedaccurately.

Inaccordancewiththeprinciplesofthisinvention,areferenceunit12isprovided.Thereferenceunit12isofthesameconstructionasthemeasuringunit10andthereforeincludesanelectroacoustictransmitter50whichincludespiezoelectricmaterial52sandwichedbetweenapairofelectrodes54and56,andanelectroacousticreceiver58whichincludespiezoelectricmaterial60sandwichedbetweenapairofelectrodes62and64.Again,transducersotherthanthepiezoelectrictypecanbeutilized.Thetransmitter50andthereceiver58arespacedapartaknownandfixedreferencedistancenDRTheelectrodes62and64arecoupledtotheinputoftheamplifier66,whoseoutputiscoupledtotheinputofthedetector68.Theoutputofthedetector68iscoupledtothepulseformer70whichgeneratestriggerpulses.Thetriggerpulsesareappliedtothepulsegenerator72whichcontrolsthemodulator74topassburstsfromthecontinuouswaveoscillator76tothetransmitter50.Thetriggerpulsesfromthepulseformer70arealsoappliedtothecounter78.

Preferably,allofthetransducers16,18,50and58havethesameresonantfrequency.Therefore,theoscillators42and76bothoperateatthatfrequencyandthepulsegenerators40and72provideequalwidthoutputpulses.

Inusage,themeasuringunit10andthereferenceunit12areincloseproximitysothatthesoundvelocityinbothoftheunitsisthesame.Althoughtherepetitionratesofthepulsesinthemeasuringunit10andthereferenceunit12areeachtemperatureandhumiditydependent,itcanbeshownthatthedistanceDtobemeasuredisrelatedtothereferencedistanceDRasfollows:

iD=DR（1/tR）/（l/t）wheretRisthepropagationtimeoverthedistanceDRinthereferenceunit12.Thisrelationshipisindependentofbothtemperatureandhumidity.

Thus,theoutputsofthecounters46and78areprovidedasinputstothemicroprocessor90intheutilizationmeans14.Themicroprocessor90isappropriatelyprogrammedtoprovideanoutputwhichisproportionaltotheratiooftheoutputsofthecounters46and78,whichinturnareproportionaltotherepetitionratesoftherespectivetriggerpulsetrainsofthemeasuringunit10andthereferenceunit12.Asdescribed,thisratioisindependentoftemperatureandhum