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电子水平仪英文文献
学士学位论文英文翻译部分
题目:
电子水平仪设计
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哈尔滨工业大学教务处制
StudyonaNewHighAccuracyDual-axisElectronicLevel
Abstract
Thestudyandthedevelopmentofanewdual-axis,highaccuracyandlowcostelec-troniclevelhavebeenintroduced.Inthispaper,theideaoftheoveralldesignisdescribed,andthede-terminationforthemainmechanicalandelectronicparameters,includingtheoveralltesting,hasbeendiscussedindetail.Baseduponthepracticalcharacteristicandthespecificationsoftheinstrument,itwillbewidelyusedinthefieldofmachinetool,automobile,airplaneandshippingmanufactures.
KeyWords:
Electroniclevel;Platespring;LVDT;Tiltmeasurement
1Introduction
Thenewdual-axiselectronicleveliscalledtiltsensortoo.Itisauniquetiltmeasuringsystemcapableofsimultaneouslyrecordingthedegreeanddirectionoftiltwithhighaccuracyupto1arc-sec.withinarangeof400arc-sec.,upto3arc-sec.withinarangeof800arc-sec.Ithasareadingresolutionupto0.1arc-sec.
TheworkingprincipleoftheinstrumentisshowninFig.1.Itiscomposedofthreeparts.Onepartisthecombinationofthesupportframeandthebase.Anotherpartisstationarywork-piece5fixedonthetopofsup-portframe.Thethirdpartistheswingwork-piece2.Thework-pieces5and2areconnectedbyapairofdoubleplatesprings3.Duringmeasurementifthesurfacewhichtheinstrumentissetonistilt,thewholestructureoftheinstrumentwilltilttoo.Buttheswingwork-piece2willmovebackalongthereversedirectiontothetiltbythegravity.Therefore,thecoilandthecoreoftheLVDT(linearvariabledifferentialtransformer)willhaverelativedisplacement,andtherelativedisplacementwillbeconvertedtoanalogvoltageoutput.Thepairofplatespringsareguidewaytokeeptheswingwork-piece2moving.
Fig.1Thestructureoftheelectroniclevel.
Becauseofthesimplestructureoftheinstrument,itisworkingwithoutwearandtear,alsonocrossinfluenceuponthefunctionorprecision.Itissuitableforwidefieldofapplicationinqualityassuranceandengineering,twoexamplesaregivenasfollows.compensatethetiltofameasuredequipmentcanbereached.Thepurposeofusinganotherheadoftheinstrumentisthesameasinaboveexample.
1.1Checkingtheflatnessofmeasuringtables
TheapplicationprocessisshowninFig.2(a).Oneheadoftheinstrumentissetonastandardtriangularbase.Duringmeasurement,thetriangularbaseismovedagainstarulerstepbystep.Everystepisjustequaltoasidelengthofthetriangle.Twodimensionaltiltdataarepickedupineverystepbyacomputer.Theanotherheadoftheinstrumentissetonacornerofthemeasuredtabletomonitorthedeformationofthewholetable.Usuallythemicro-deformationofthewholetableiscausedbytheweightofthetestinginstrumentwithcontinuousmoving.
Fig.2ApplicationExamples.
1.2Monitoringthelevelorcompensatingthetiltofameasuringequipmentautomatically
ThisapplicationprocessisshowninFig.2(b).Oneheadoftheinstrumentisseton
theslidestageofameasuredinstrumentoramachinetool.Anotherheadoftheinstrumentissetonthebaseofthemeasuredequipment.Duringtheslidestagemoving,twodimensionalerrorsoftheguideway,pitchandrollerrors,arepickedupautomaticallybyacomputer.Therefore,tomonitorthelevelortocompensatethetiltofameasuredequipmentcanbereached.Thepurposeofusinganotherheadoftheinstrumentisthesameasinaboveexample.
2Theprincipleofoperation
Duringmeasurement,theinstrumentissetuponasurfacetobemeasuredandisadjustedtothezeroindicationwiththreescrews8.Ifthesurfaceistiltedasmallangle角度tothehorizontal,thentheswingpartwillbearaforceFandaforcecoupleM.WiththemultipleinfluenceofFandM,adeflectionYofthedoubleplatespringswillbegeneratedasshowninFig.3.Itcanbeexpressedbytheformula
(1):
Fig.3Theworkingsituationoftheplatesprings.
Here:
Eistheelasticmodulusofthespring,Iisthemomentofinertia.Also
(bisthewidth,histhethicknessofthesprings)isknown.BecausethetiltangleHis
onlywithin800arc-sec.,F=P×sinθcanbewrittenasF=P×θ.Therefore,theformula
(1)becomesto
Upontheformula
(2),obviouslythedeflectionofthespringsislinearwiththetiltangleθ.
Supposetheabsolutezerooftheinstrumentisjustindicatingtheglobelevel,thenthecenterofthecorewillcoincidewiththecenterofthecoilofaLVDT.Whenatiltθofthesurfacetakeplace,thetwocentersofthecoreandthecoilwillmoverelativelyfollowingtheswingpart.Thelargerofthetiltθwillleadtothelongerofthedistanceofthetwocenters.ThemechanicaldisplacementwillbeconvertedtoabipolardcvoltagebyLVDTanditssubsystemAD598chip.
3Designofthemainsystem
Duringdesign,theimportantfactoristocontrolanddecreasethehysteresisofthe
spring.Inordertoreachthisrequirement,twoprinciplesshouldbeobeyed:
First,thematerialofthespringshouldpossesssmallerhysteresis,sowehavechosenakindofspringmadeofNi-Ti-Alseriesalloythatisbetterforthisrequirement.Second,duringwork,themaximumdeflectionYshouldbesmallerthanthemaximumelasticdisplacementofthespringabout4~5times.Themaximumelasticdisplacementofthespringδmaxis:
Hereσistheelasticlimitofthespring.
Also,consideringthewholesizeoftheinstrument,wesetthelengthLofthespringtobe60mm,widthb=25mm,andthicknessh=0.15mm.Accordingtotheformulae
(2)and(3),wesetthemaximumdeflectionofhespringYtobe0.2mm,withinthemaximumworkingrangeθ=800arc-sec.
Basedontherequirementsoftherangeand0.1arc-sec.resolution,wecangettherequirementsforchoosingLVDT.MiniaturetypeofLVDT,MHRseries(010MHR),ischosen.ItsspecificationsarelistedinTable1.
Table1
ThecircuitforconjunctionwithLVDTtoconverttransducermechanicalpositiontoa
bipolarvoltagewithahighdegreeofaccuracyandrepeatabilityisshowninFig.4.WechooseanintegratedcircuitchipAD598.TheAD598containsalowdistortionsinewaveoscillatortodrivetheLVDTprimary.TheLVDTsecondaryoutputconsistsoftwosinewavesthatdrivetheAD598directly.TheAD598operatesuponthetwosignals,dividingtheirdifferencebytheirsum,producingascaledbipolardcoutput.Forafull-scaledisplacementofY=0.2mm,thevoltageoutputoftheAD598iscomputedbyformula(4):
WhereS=126mV/(V#mm)isLVDTsensitivity,Vout=4Visthefullrangeoutputvoltage,dismeasuringrange,hereVA+VB=2.7V.Basedontheformula(4),wegetthevalueR2=280k
Theoutputdcvoltageisthenconnectedtoa16bitsA/Dconverter9015.ThefullscaleoutputfromAD598is4Vanalog.Sothe800arc-sec.isrespectedwithabout25600bitsdigit.Inordertogetstablereading,theconvertedbitsaredividedby4.Therefore,8bitisequalto1arc-sec.
Fig.4AD598fordualsupplyoperation.
Fig.5Calibrationandoveralltesting.
4Calibrationandoveralltest
ThecalibrationisshowninFig.5.Thedual-axiselectroniclevelissetonameasuringfixture4whichhasbeentested.Whenthefixtureisworking,thereisabout0.1~0.2arc-sec.ofrollmovementaroundthebeamdirectionoftheHPinterferometer.Thetargetofdoubleretroreflectorsissetonthefixturetoo.TheHPinterferomreterandpartoftheanglesystemarefixedonastagewithfixture4together.First,theinstrumentiscalibratedagainstHPlaserwiththenumberofbits.Aftercalibration,theequivalentvaluesbetweenbitsandtiltanglesareknown.Therefore,theread-outoftheinstrumentcanbeexpressedbyanglevalue.WeusethesameapparatusasshowninFig.5todotheoveralltesting.Duringtestingthetopplateofthefixtureisupanddowntomakedifferentanglesthroughturningascrew.Thetestingdataarelistedin
table2.
Table2givesoutthetestingdataforpositivedirectionandpositivereturndirectionofXaxisoftheelectroniclevel.ThereareasetofdataforminusdirectionandtherearetwosetsofdataforYaxisoftheelectroniclevel.AllothertestingresultsarethesameasthedatashowninTable2.Basedonthetestingdata,wecansaythatthemaximumuncertaintyoftheinstrumentwithin300arc-sec.isbetterthan1arc-sec.
5Conclusion
Thenewdual-axiselectroniclevelhasasimplemechanicalstructure,buthighaccuracyandfeasibleforusingandadjustment.Thisachievementisowetothecompactmechanicalbody,afewintegratedcircuitchipwithonlyseveralelectronicexternalpassivecomponentsengagedinthework,alsoowetothequalityoftheplatespring,thebetterlinearityoftheLVDT,thesatisfactorystabilityoftheAD598circuitry.Duetothedual-axisfunctionplusdoublesetscanbeconnectedtogethertodoameasuringproject,thenewelectroniclevelcanensureameasuringprocessmorereliableandmorereasonable.Soitisveryusefulandveryeasyforthewideapplicationsinthefieldofindustry.
References
1WangBaoguang,MaoYunying.Studyonthestructuredesignofahighaccuracy3Dprobe.JournalofTianjinUniversity,1993,
(1):
76~84
2ChenLincai.Designofprecisioninstrument.1sted.Beijing:
MechanicalIndustryExpress,1991,
3Signalconditioningcomponents&subsystem.Handbook,ANALOGDEVICES:
13~23
4Linear&angulardisplacementtransducers.Hand-book,CompanyLucasSchaevitz
一种高精度的新型双坐标电子水平仪的研究
摘要
介绍一种新型的高精度、双坐标、低成本电子水平仪的研究与开发。
论述了其总体设计思想,并对机械、电子等主要参数的确定方法及精度检定等进行了深入的讨论。
通过对仪器的实用性和精度指标的分析,表明该仪器在机床、汽车、飞机和轮船等制造领域有着广泛的应用前景。
关键词:
电子水平仪片簧线性差动式变压器(LVDT)倾斜角度测量
1引言
型的双轴电子水平倾角传感器。
这是一个独特的倾斜测量系统能够同时记