基于AT89S52单片机的超声波测距设计的外文翻译Word文档下载推荐.docx

基于AT89S52单片机的超声波测距设计的外文翻译Word文档下载推荐.docx

《基于AT89S52单片机的超声波测距设计的外文翻译Word文档下载推荐.docx》由会员分享，可在线阅读，更多相关《基于AT89S52单片机的超声波测距设计的外文翻译Word文档下载推荐.docx（10页珍藏版）》请在冰豆网上搜索。

Lobo,IanJ.

A.BACKGROUNDOFTHEINVENTION

Thisinventionrelatestoapparatusforthemeasurementofdistanceand,moreparticularly,tosuchapparatuswhichtransmitsultrasonicwavesbetweentwopoints.

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

Whenthemediumbetweenthetwopointswhosespacingisbeingmeasuredisair,thesoundvelocityisdependentuponthetemperatureandhumidityoftheair.Itisthereforeafurtherobjectofthe,presentinventiontoprovideapparatusofthetypedescribedwhichisindependentoftemperatureandhumidityvariations.

B.SUMMARYOFTHEINVENTION

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

C.DETAILEDDESCRIPTION

A.principleofultrasonicdistancemeasurement

1,theprincipleofpiezoelectricultrasonicgenerator

Piezoelectricultrasonicgeneratoristheuseofpiezoelectriccrystalresonatorstowork.Ultrasonicgenerator,theinternalstructureasshowninFigure1,ithastwopiezoelectricchipandaresonanceplate.Whenit'

stwopluspulsesignal,thefrequencyequaltotheintrinsicpiezoelectricoscillationfrequencychip,thechipwillhappenpiezoelectricresonance,andpromotethedevelopmentofplatevibrationresonance,ultrasoundisgenerated.Conversely,ifthetwoarenotinter-electrodevoltage,whentheboardreceivedultrasonicresonance,itwillbeforvibrationsuppressionofpiezoelectricchip,themechanicalenergyisconvertedtoelectricalsignals,thenitbecomestheultrasonicreceiver.

Thetraditionalwaytodeterminethemomentoftheecho'

sarrivalisbasedonthresholdingthereceivedsignalwithafixedreference.Thethresholdischosenwellabovethenoiselevel,whereasthemomentofarrivalofanechoisdefinedasthefirstmomenttheechosignalsurpassesthatthreshold.Theintensityofanechoreflectingfromanobjectstronglydependsontheobject'

snature,sizeanddistancefromthesensor.Further,thetimeintervalfromtheecho'

sstartingpointtothemomentwhenitsurpassesthethresholdchangeswiththeintensityoftheecho.Asaconsequence,aconsiderableerrormayoccurEventwoechoeswithdifferentintensitiesarrivingexactlyatthesametimewillsurpassthethresholdatdifferentmoments.Thestrongeronewillsurpassthethresholdearlierthantheweaker,soitwillbeconsideredasbelongingtoanearerobject.

2,theprincipleofultrasonicdistancemeasurement

Ultrasonictransmitterinadirectiontolaunchultrasound,inthemomenttolaunchthebeginningoftimeatthesametime,thespreadofultrasoundintheair,obstaclesonhiswaytoreturnimmediately,theultrasonicreflectedwavereceivedbythereceiverimmediatelystoptheclock.Ultrasoundintheairasthepropagationvelocityof340m/s,accordingtothetimerrecordsthetimet,wecancalculatethedistancebetweenthelaunchdistancebarrier（s）,thatis:

s=340t/2

B.UltrasonicRangingSystemfortheSecondCircuitDesign

Systemischaracterizedbysingle-chipmicrocomputertocontroltheuseofultrasonictransmitterandultrasonicreceiversincethelaunchfromtimetotime,single-chipselectionof8751,economic-to-use,andthechiphas4KofROM,tofacilitateprogramming.CircuitschematicdiagramshowninFigure2.Drawonlythefrontrangeofthecircuitwiringdiagram,leftandrightinfrontofRangingRangingcircuitsandthesamecircuit,itisomitted.

1,40kHzultrasonicpulsegeneratedwiththelaunch

RangingsystemusingtheultrasonicsensorofpiezoelectricceramicsensorsUCM40,itsoperatingvoltageofthepulsesignalis40kHz,whichbythesingle-chipimplementationofthefollowingprocedurestogenerate.

puzel:

mov14h,#12h;

ultrasonicfiringcontinued200ms

here:

cplp1.0;

output40kHzsquarewave

nop;

djnz14h,here;

ret

Ranginginfrontofsingle-chipterminationcircuitP1.0inputport,singlechipimplementationoftheaboveprocedure,theP1.0portina40kHzpulseoutputsignal,afteramplificationtransistorT,thedrivetolaunchthefirstultrasonicUCM40T,issued40kHzultrasonicpulse,andthecontinuedlaunchof200ms.Rangingtherightandtheleftsideofthecircuit,respectively,theninputportP1.1andP1.2,theworkingprincipleandcircuitinfrontofthesamelocation.

2,receptionandprocessingofultrasonic

UsedtoreceivethefirstlaunchofthefirstpairUCM40R,theultrasonicpulsemodulationsignalintoanalternatingvoltage,theop-ampamplificationIC1AandafterpolarizationIC1BtoIC2.IC2islockedloopwithaudiodecoderchipLM567,internalvoltage-controlledoscillatorcenterfrequencyoff0=1/1.1R8C3,capacitorC4determinetheirtargetbandwidth.R8-conditioninginthelaunchofthecarrierfrequencyontheLM567inputsignalisgreaterthan25mV,theoutputfromthehighjump8feetintoalow-level,asinterruptrequestsignalstothesingle-chipprocessing.

Ranginginfrontofsingle-chipterminationcircuitoutputportINT0interruptthehighestpriority,rightorleftlocationoftheoutputcircuitwithoutputgateIC3AaccessINT1portsingle-chip,whilesingle-chipP1.3andP1.4receivedinputIC3A,interruptedbytheprocesstoidentifythesourceofinquirytodealwith,interruptprioritylevelforthefirstleftrightafter.Partofthesourcecodeisasfollows:

receive1:

pushpsw

pushacc

clrex1;

relatedexternalinterrupt1

jnbp1.1,right;

P1.1pinto0,rangingfromrighttointerruptserviceroutinecircuit

jnbp1.2,left;

P1.2pinto0,totheleftrangingcircuitinterruptserviceroutine

return:

SETBEX1;

openexternalinterrupt1

popacc

poppsw

reti

right:

...;

rightlocationentrancecircuitinterruptserviceroutine

AjmpReturn

left:

leftRangingentrancecircuitinterruptserviceroutine

3,thecalculationofultrasonicpropagationtime

Whenyoustartfiringatthesametimestartthesingle-chipcircuitrywithinthetimerT0,theuseoftimercountingfunctionrecordsthetimeandthelaunchofultrasonicreflectedwavereceivedtime.Whenyoureceivetheultrasonicreflectedwave,thereceivercircuitoutputsanegativejumpintheendofINT0orINT1interruptrequestgeneratesasignal,single-chipmicrocomputerinresponsetoexternalinterruptrequest,theimplementationoftheexternalinterruptservicesubroutine,readthetimedifference,calculatingthedistance.Someofitssourcecodeisasfollows:

RECEIVE0:

PUSHPSW

PUSHACC

CLREX0;

relatedexternalinterrupt0

MOVR7,TH0;

readthetimevalue

MOVR6,TL0

CLRC

MOVA,R6

SUBBA,#0BBH;

calculatethetimedifference

MOV31H,A;

storageresults

MOVA,R7

SUBBA,#3CH

MOV30H,A

SETBEX0;

openexternalinterrupt0

POPACC

POPPSW

RETI

Foraflattarget,adistancemeasurementconsistsoftwophases:

acoarsemeasurementand.afinemeasurement:

Step1:

Transmissionofonepulsetraintoproduceasimpleultrasonicwave.

Step2:

Changingthegainofbothechoamplifiersaccordingtoequation,untiltheechoisdetected.

Step3:

Detectionoftheamplitudesandzero-crossingtimesofbothechoes.

Step4:

Settingthe