超声波测距外文文献加中文翻译毕业设计

1、PlPlIF.2附录A英文原文ULTASONICRANGINGINAIRG.E.RudashevskiandA.A.GorbatovUDC534,321.9:531.71.083.7Oneofthemostimportantproblemsininstrumentationtechnologyistheremote,contactlessmeasurementofdistancesintheorderof0.2to10minair.Suchaproblemoccurs,forinstance,whenmeasuringtherelativethreedimensionalpositionofs

2、eparatemachinemembersorstructuralunits.Interestingpossibilitiesforitssolutionareopenedupbyutilizingultrasonicvibrationsasaninformationcarrier.Thephysicalpropertiesofair,inwhichthemeasurementsaremade,permitvibrationstobeemployedatfrequenciesupto500kHzfordistancesupto0.5mbetweenamemberandthetransducer

3、,orupto60kHzwhenrangingonobstacleslocatedatdistancesupto10m.Theproblemofmeasuringdistancesinairissomewhatdifferentfromotherproblemsinthea-pplicationofultrasound.Althoughthepossibilityofusingacousticrangingforthispurposehasbeenknownforalongtime,andatfirstglanceappearsverysimple,neverthelessattheprese

4、nttimethereareonlyasmallnumberofdevelopmentsusingthismethodthataresuitableforpracticalpurposes.Themaindifficultyhereisinprovidingareliableacousticthree-dimensionalcontactwiththetestobjectduringseverechangesintheairscharacteristic.Practicallyallacousticarrangementspresentlyknownforcheckingdistancesus

5、eamethodofmeasuringthepropagationtimeforcertaininformationsamplesfromtheradiatortothereflectingmemberandback.Theunmodulatedacoustic(ultrasonic)vibrationsradiatedbyatransducerarenotinthemselvesasourceofinformation.Inordertotransmitsomeinformationalcommunicationthatcanthenbeselectedatthereceivingendaf

6、terreflectionfromthetestmember,theradiatedvibrationsmustbemodulated.Inthiscasetheultrasonicvibrationsarethecarrieroftheinformationwhichliesinthemodulationsignal,i.e.,theyarethemeansforestablishingthespatialcontactbetweenthemeasuringinstrumentandtheobjectbeingmeasured.Thisconclusion,however,doesnotme

7、anthattheanalysisandselectionofparametersforthecarriervibrationsisofminorimportance.Onthecontrary,thefrequencyofthecarriervibrationsislinkedinaveryclosemannerwiththecodingmethodfortheinformationalcommunication,withthepassbandofthereceivingandradiatingelementsintheapparatus,withthespatialcharacterist

8、icsoftheultrasoniccommunicationchannel,andwiththemeasuringaccuracy.Letusdwellonthequestionsofgeneralimportanceforultrasonicranginginair,namely:onthechoiceofacarrierfrequencyandtheamountofacousticpowerreceived.Ananalysisshowsthatwithconicaldirectivitydiagramsfortheradiatorandreceiver,andassumingthatt

9、hedistancebetweenradiatorandreceiverissubstantiallysmallerthanthedistancetotheobstacle,theamountofacousticpowerarrivingatthereceivingareaPrforthecaseofreflectionfromanidealplanesurfacelocatedatrightanglestotheacousticaxisofthetransducercomesto=Pe=Pe-4卩lrad-1+4LtgadwherePradistheamountofacousticpower

10、radiated,Bistheabsorptioncoefficientforaplanewaveinthemedium,Listhedistancebetweentheelectroacoustictransducerandthetestme-mber,disthediameteroftheradiator(receiver),assumingtheyareequal,andcistheangleofthedirectivitydiagramfortheelectroacoustictransducerintheradiator.4翻iirGIDEz?Hz4翻iirGIDEz?Hz0*才垃0

11、*才垃川L,niFl号aBothinEq.(l)andbelow,theabsorptioncoefficientisdependentontheamplitudeandnotontheintensityasinsomeworks1,andthereforewethinkitnecessarytostressthisdifference.Inthevariousproblemsofsoundrangingonthetestmembersofmachinesandstructures,therelationshipbetweenthesignalattenuationsduetotheabsor

12、ptionofaplanewaveandduetothegeometricalpropertiesofthesoundbeamare,asarule,quitedifferent.Itmustbepointedoutthatthechoiceofthegeometricalparametersforthebeaminspecificpracticalcasesisdictatedbytheshapeofthereflectingsurfaceanditsspatialdistortionrelativetosomeaverageposition.Letusconsiderinmoredetai

13、ltherelationshipbetweenthegeometricandthepowerparametersofacousticbeamsforthemostcommoncasesofrangingonplaneandcylindricalstructuralmembers.ItiswellknownthatthedirectionalcharacteristicWofacircularpistonvibratinginaninfinitebaffleisafunctionoftheratioofthepistonsdiametertothewavelengthd/九asfoundfrom

14、thefollowingexpression:(nd.“sin丿兀d.“sinwhereJIisaBesselfunctionofthefirstorderandaistheanglebetweenanormaltothepistonandalineprojectedfromthecenterofthepistontothepointofobservation(radiation).FromEq.(2)itisreadilyfoundthatatwo-to-onereductioninthesensitivityofaradiatorwithrespecttosoundpressurewill

15、occurattheangle.0.76九(3=arcsin(30.5dForanglesaarcsinwhereaisthevalueoftheangleforthedirectivitydiagram,Ymaxisthemaximumdisplacementofthecylinderscenterfromtheacousticaxis,andLministheminimumdistancefromthecenteroftheelectroacoustictransducertothereflectingsurfacemeasuredalongthestraightlineconnectin

16、gthecenterofthememberwiththecenterofthetransducer.Itisclearthatwhenmeasuringdistance,therunningtimeoftheinformationsignaliscontrolledbythelengthofthepathinadirectionnormaltothecylinderssurface,orinotherwords,themeasuredistanceisalwaystheshortestone.Thisstatementiscorrectforallcasesofspecularreflecti

17、onofthevibrationsfromthetestsurface.ThesimultaneoussolutionofEqs.(2)and(8)whenW=0.5leadstothefollowingexpression:X(RL(9)d0.76min(9)ym/sec,andontheasstunptionthatLIntheparticularcasewherethesoundramnaxgingtakesplaceinairhavingc=330m/sec,andontheasstunptionthatLminR,thenecessarydiameterofaunidirection

18、alpistonradiatordcanbefoundfromthefomula25R(10)fy(10)maxwheredisincmandfisinkHz.CurvesareshowninFig.2fordeterminingthenecessarydiameteroftheradiatorasafunctionoftheratioofthecylindersradiustothemaximumdisplacementfromtheaxisforfourradiationfrequencies.Alsoshowninthisfigureisthedirectivitydiagramangl

19、easafunctionofRandYrnaxforfourratiosofminimumdistancetoradius.Theultrasonicabsorptioninairisthesecondfactorindeterminingtheresolutionofultrasonicrangingdevicesandtheirrangeofaction.TheresultsofphysicalTTTinvestigationsconcerningthemeasurementofultrasonicvibrationsairaregivenin1-3.Upuntilnowtherehasb

20、eennounambiguousexplanationofthediscrepancybetweenthetheoreticalandexpe-rimentalabsorptionresultsforultrasonicvibrationsinair.Thus,forfrequenciesintheorderof50to60kHzatatemperatureof+25oCandarelativehumidityof37%theenergyabsorptioncoefficientforaplanewaveisabout2.5dB/mwhilethetheoreticalvalueis0.3dB

21、/m.TheabsorptioncoefficientBasafunctionoffrequencyforatemperatureof+25oCandahumidityof37%accordingtothedatain2canbedescribedbyTable1.Theabsorptioncoefficientdependsontherelativehumidity.Thus,forfrequenciesintheorderof10to20kHzthehighestvalueoftheabsorptioncoefficientoccursat20%humidity3,andat40%humi

22、ditytheabsorptionisreducedbyabouttwotoone.Forfrequenciesintheorderof60kHzthemaximumabsorptionoccursat30.7ohumidity,droppingwhenitisincreasedto98%orloweredto10%byafactorofapproximatelyfourtoone.Theairtemperaturealsohasanappreciableeffectontheultrasonicabsorption1.Whenthetemperatureofthemediumisincrea

23、sedfrom+10to+30,theabsorptionforfrequenciesbetween30and50kHzincreasesbyaboutthreetoone.Takingallthefactorsnotedaboveintoaccountwearriveatthefollowingapproximatevaluesfortheabsorptioncoefficient:atafrequencyof60kHz/3min=0.15m-1andmax=0.5-1;atafrequencyof200kHz/min=0.6m-1andB=2m-1.maxTherelationshipsu

24、nderconsiderationareshowngraphicallyinFig.3.Intheupperpartofthediagramcurvesofg=f(L)areplottedforfivevaluesofthetotalangleintheradiatorsdirectivitydiagram,where13LC11)radiatorsdirectivitydiagram,where13LC11)Thevaluesfortheminimumminandrnaxil-nummaxtransmittancecoefficientswereobtainedintheabsenceofa

25、erosolsandrain.Theirdifferenceistheresultofthepossiblevariationsintemperatureovertherangefrom-30to+50andinrelativehmnidityovertherangefrom10to98%.Theoverallvalueofthetransmittanceisobtainedbymultiplyingthevaluesofgand0forgivenvaluesofL,f,andd.LITERATURECITEDL.Bergman,UltrasonicsRussiantranslation,Iz

26、d.Inostr.Lit.,Moscow(1957).V.A.Krasilnikov,SonicandUltrasonicWavesinRussian,Fizmatgiz,Moscow(1960).M.MokhtarandE.Richardson,ProceedingsoftheRoyalSociety,184(1945).附录B中文翻译在空气中超声测距G.E.RudashevskiandA.A.GorbatovUDC534,321.9:531.71.083.7在仪器技术中远程是最重要的一个问题。在空气中，从0.2米至10米非接触式测量距离时，涉及到了这个问题，例如，在测量时个别机件或结构单位

27、的相对三维位置。有趣的是，是利用超声振动作为信息运输工具，开启了解决办法的可能性.在空气这个自然道具中，进行测量的是雇用成员和传感器之间距离0.5米的时候，允许振动频率高达500千赫，或当与障碍物之间修正距离延伸达10米时候，振动频率高达60千赫兹。应用超声波在空气中测量距离不同于其他的问题。虽然能否利用声波修正测距的可行性已经研究了很长一段时间，乍一看似乎很简单，但是目前只有为数不多的新发明使用这种适合实际目的方法，主要困难是在有严重特有变化的空气中提供一个可靠试验对象去接触三维声波。几乎所有的目前已知用来校验距离使用的，都是为了某些来自用来反射成员和后面的散热器信息样本，测量传播时间解决声

28、音的办法。该未解调的声（超声）振动由传感器辐射的，本身并不是一个信息来源.在接收端，来自测试会员反射后，为了传递一些情报信息，因而被选定后，辐射振动一定会被调制。在这种情况下，超声波振动是在于调制信号的信息的承运人，即他们就是在测量仪器和测量稳定的对象之间建立了空间三维接触的手段。这一结论，但是，并不意味着分析和选择的参数承运人振动重要性小.正相反，承运人振动频率与信息沟通编码方法，与接收通频带和仪器中的辐射元素，与超声波空间特有的沟通渠道，以及测量精度是具有非常密切的联系方式。让我们谈具有普遍意义的空气中超声波测距问题，即：载波频率和的被普遍认为标准的声音数额的选择。1）标准的声音数额的选择

29、。1）在Prad辐射声功率，B是平面波在介质中吸收系数为，L是声电传感器和测试箱之间的距离，D是散热器（接收）的直径，C是的电声换能器的散热器方向性图的角度。在均衡器（1）及以下，和作品1一样，吸收系数依赖于振幅和而不是强度，因此，我们认为有必要强调这种差异。5fff*!0?min消川Mis)4矿卩刃5fff*!0?min消川Mis)4矿卩刃T7maxUHmnf.-Cm芒矿卜iff*iii(&?Mlz疋十$液kg)图3在声音的各种问题上，包括成员测试设备和结构的关系，由于信号衰减吸收的平面和适当的几何性质的声束是，作为一项规则，一定是相差甚远的需要指出的是，选择的实际情况中光束具体的几何参数，

30、是基于形状的反射面和空间的一些失真相对平均排布。让我们考虑一下更详细的几何关系和声束的动力参数这个最常见包括平面和圆柱结构的成员情况。众所周知，定向特性瓦的一个圆形活塞振动无限挡板是一个活塞比例函数d/九为下列表达式基础：2J（加sin、W=，:丿“sin从均衡器（2）中很容易发现，在减少两到一个敏感性散热器方面声压级角度将会引起注意。0.76九=arcsin(3)0.5d表1fOkHz10203040506080100150200300500卩0dB/m1.522.63.54691640对角可以简化为a2O.Eq.(3)4)0.764)OL0.5fd其中c是中期声速，F是辐

31、射震动的频率它遵循均衡器(4)，当辐射到空中，其中c=300米/秒，在0.5级的压力面，散热器为采取的轴的直径用于指定角度的方向性图上是必要的5)5)dOf其中d是厘米，khz是千赫，a是度角。在图1中显示的曲线图是均衡器(5)中6个角度散热器的方向性图。事实上，直径的“超声波降解标本”现场控制的两个变量，即：直径的散热器和发散角的声音束.一般情况下，最小直径的“超声波降解标本”在现场飞机表面处理，通常倾向于散热器的轴心。D,6cL(6)minfL是测试表面最小的距离。对应的散热器直径L是测试表面最小的距离。对应的散热器直径1.5cLd，7)(7)作为从均衡器(6)及(7)，“声振”现场最小直径，最高要求散热器直径距离不得少于2.自然的，以短距离的障碍的大小，“声振“表面的更少。其中d是厘米，khz的在千赫，a是度角让我们考虑在半径为R的中声波测距的情况。问题是在X和Y中坐标轴上衡量从声电传感器的到圆柱形物体侧表面的距离缸其各种可能的位移沿X和Y轴，散热器的方向性图角度a的必要性在这种情况下被用词组的形式表示出来。oarcsinymax(8)R+Lmin在这里是a的价值角度的方向性图，ymax是声学轴中心最大位移气瓶，Lminmax是从中央电传感器的反射面测量沿直线连接的中心与中心会员的传感器之间最短距离很显然，当测量距离，在信息信号“运行”时，对于在圆柱体表面来说