单片机的超声波测距系统的研究与设计毕业论文外文文献翻译及原文Word文件下载.docx
- 文档编号:17869446
- 上传时间:2022-12-11
- 格式:DOCX
- 页数:28
- 大小:725.23KB
单片机的超声波测距系统的研究与设计毕业论文外文文献翻译及原文Word文件下载.docx
《单片机的超声波测距系统的研究与设计毕业论文外文文献翻译及原文Word文件下载.docx》由会员分享,可在线阅读,更多相关《单片机的超声波测距系统的研究与设计毕业论文外文文献翻译及原文Word文件下载.docx(28页珍藏版)》请在冰豆网上搜索。
文献、资料来源:
文献、资料发表(出版)日期:
院(部):
专业:
班级:
姓名:
学号:
指导教师:
翻译日期:
2017.02.14
附录
附录A
外文翻译
theequivalentdcvalue.Intheanalysisofelectroniccircuitstobeconsideredinalatercourse,bothdcandacsourcesofvoltagewillbeappliedtothesamenetwork.Itwillthenbenecessarytoknowordeterminethedc(oraveragevalue)andaccomponentsofthevoltageorcurrentinvariouspartsofthesystem.
EXAMPLE13.13DeterminetheaveragevalueofthewaveformsofFig.13.37.
FIG.13.37
Example13.13.
Solutions:
a.Byinspection,theareaabovetheaxisequalstheareabelowoveronecycle,resultinginanaveragevalueofzerovolts.
b.UsingEq.(13.26):
asshowninFig.13.38.
Inreality,thewaveformofFig.13.37(b)issimplythesquarewaveofFig.13.37(a)withadcshiftof4V;
thatisv2_=v1+4V
EXAMPLE13.14Findtheaveragevaluesofthefollowingwaveformsoveronefullcycle:
a.Fig.13.39.
b.Fig.13.40.
Wefoundtheareasunderthecurvesintheprecedingexamplebyusingasimplegeometricformula.Ifweshouldencounterasinewaveoranyotherunusualshape,however,wemustfindtheareabysomeothermeans.Wecanobtainagoodapproximationoftheareabyattemptingtoreproducetheoriginalwaveshapeusinganumberofsmallrectanglesorotherfamiliarshapes,theareaofwhichwealreadyknowthroughsimplegeometricformulas.Forexample,
theareaofthepositive(ornegative)pulseofasinewaveis2Am.
Approximatingthiswaveformbytwotriangles(Fig.13.43),weobtain(usingarea_1/2base_heightfortheareaofatriangle)aroughideaoftheactualarea:
Acloserapproximationmightbearectanglewithtwosimilartriangles(Fig.13.44):
whichiscertainlyclosetotheactualarea.Ifaninfinitenumberofformswereused,anexactanswerof2Amcouldbeobtained.Forirregularwaveforms,thismethodcanbeespeciallyusefulifdatasuchastheaveragevaluearedesired.Theprocedureofcalculusthatgivestheexactsolution2Amisknownasintegration.Integrationispresentedhereonlytomakethemethodrecognizabletothereader;
itisnotnecessarytobeproficientinitsusetocontinuewiththistext.Itisausefulmathematicaltool,however,andshouldbelearned.Findingtheareaunderthepositivepulseofasinewaveusingintegration,wehave
where∫isthesignofintegration,0andparethelimitsofintegration,Amsinaisthefunctiontobeintegrated,anddaindicatesthatweareintegratingwithrespecttoa.Integrating,weobtain
Sinceweknowtheareaunderthepositive(ornegative)pulse,wecaneasilydeterminetheaveragevalueofthepositive(ornegative)regionofasinewavepulsebyapplyingEq.(13.26):
_
ForthewaveformofFig.13.45,
EXAMPLE13.15DeterminetheaveragevalueofthesinusoidalwaveformofFig.13.46.
Solution:
Byinspectionitisfairlyobviousthat
theaveragevalueofapuresinusoidalwaveformoveronefullcycleis
zero.
EXAMPLE13.16DeterminetheaveragevalueofthewaveformofFig.13.47.
Thepeak-to-peakvalueofthesinusoidalfunctionis16mV+2mV_=18mV.Thepeakamplitudeofthesinusoidalwaveformis,therefore,18mV/2_=9mV.Countingdown9mVfrom2mV(or9mVupfrom-16mV)resultsinanaverageordclevelof-7mV,asnotedbythedashedlineofFig.13.47.
EXAMPLE13.17DeterminetheaveragevalueofthewaveformofFig.13.48.
EXAMPLE13.18ForthewaveformofFig.13.49,determinewhethertheaveragevalueispositiveornegative,anddetermineitsapproximatevalue.
Fromtheappearanceofthewaveform,theaveragevalueispositiveandinthevicinityof2mV.Occasionally,judgmentsofthistypewillhavetobemade.
Instrumentation
Thedcleveloraveragevalueofanywaveformcanbefoundusingadigitalmultimeter(DMM)oranoscilloscope.Forpurelydccircuits,simplysettheDMMondc,andreadthevoltageorcurrentlevels.Oscilloscopesarelimitedtovoltagelevelsusingthesequenceofstepslistedbelow:
1.FirstchooseGNDfromtheDC-GND-ACoptionlistassociatedwitheachverticalchannel.TheGNDoptionblocksanysignaltowhichtheoscilloscopeprobemaybeconnectedfromenteringtheoscilloscopeandrespondswithjustahorizontalline.Settheresultinglineinthemiddleoftheverticalaxisonthehorizontalaxis,asshowninFig.13.50(a).
2.Applytheoscilloscopeprobetothevoltagetobemeasured(ifnotalreadyconnected),andswitchtotheDCoption.Ifadcvoltageispresent,thehorizontallinewillshiftupordown,asdemonstratedinFig.13.50(b).Multiplyingtheshiftbytheverticalsensitivitywillresultinthedcvoltage.Anupwardshiftisapositivevoltage(higherpotentialattheredorpositiveleadoftheoscilloscope),whileadownwardshiftisanegativevoltage(lowerpotentialattheredorpositiveleadoftheoscilloscope).Ingeneral,
1.UsingtheGNDoption,resetthehorizontallinetothemiddleofthescreen.
2.SwitchtoAC(alldccomponentsofthesignaltowhichtheprobeisconnectedwillbeblockedfromenteringtheoscilloscope—onlythealternating,orchanging,componentswillbedisplayed).
Notethelocationofsomedefinitivepointonthewaveform,suchasthebottomofthehalf-waverectifiedwaveformofFig.13.51(a);
thatis,noteitspositionontheverticalscale.Forthefuture,wheneveryouusetheACoption,keepinmindthatthecomputerwilldistributethewaveformaboveandbelowthehorizontalaxissuchthattheaveragevalueiszero;
thatis,theareaabovetheaxiswillequaltheareabelow.
3.ThenswitchtoDC(topermitboththedcandtheaccomponentsofthewaveformtoentertheoscilloscope),andnotetheshiftinthechosenlevelofpart2,asshowninFig.13.51(b).Equation
(13.29)canthenbeusedtodeterminethedcoraveragevalueofthewaveform.ForthewaveformofFig.13.51(b),theaveragevalueisabout
TheprocedureoutlinedabovecanbeappliedtoanyalternatingwaveformsuchastheoneinFig.13.49.InsomecasestheaveragevaluemayrequiremovingthestartingpositionofthewaveformundertheACoptiontoadifferentregionofthescreenorchoosingahighervoltagescale.DMMscanreadtheaverageordclevelofanywaveformbysimplychoosingtheappropriatescale.
13.7EFFECTIVE(rms)VALUES
Thissectionwillbegintorelatedcandacquantitieswithrespecttothepowerdeliveredtoaload.Itwillhelpusdeterminetheamplitudeofasinusoidalaccurrentrequiredtodeliverthesamepowerasaparticulardccurrent.Thequestionfrequentlyarises,Howisitpossibleforasinusoidalacquantitytodeliveranetpowerif,overafullcycle,thenetcurrentinanyonedirectioniszero(averagevalue_0)?
Itwouldalmostappearthatthepowerdeliveredduringthepositiveportionofthesinusoidalwaveformiswithdrawnduringthenegativeportion,andsincethetwoareequalinmagnitude,thenetpowerdeliverediszero.However,understandthatirrespectiveofdirection,currentofanymagnitudethrougharesistorwilldeliverpowertothatresistor.Inotherwords,duringthepositiveornegativeportionsofasinusoidalaccurrent,powerisbeingdeliveredateach
instantoftimetotheresistor.Thepowerdeliveredateachinstantwill,ofcourse,varywiththemagnitudeofthesinusoidalaccurrent,buttherewillbeanetflowduringeitherthepositiveorthenegativepulseswithanetflowoverthefullcycle.Thenetpowerflowwillequaltwicethatdeliveredbyeitherthepositiveorthenegativeregionsofsinusoidalquantity.AfixedrelationshipbetweenacanddcvoltagesandcurrentscanbederivedfromtheexperimentalsetupshowninFig.13.52.Aresistorinawaterbathisconnectedbyswitchestoadcandanacsupply.Ifswitch1isclosed,adccurrentI,determinedbytheresistanceRandbatteryvoltageE,willbeestablishedthroughtheresistorR.Thetemperaturereachedbythewaterisdeterminedbythedcpowerdissipatedintheformofheatbytheresistor.
Ifswitch2isclosedandswitch1leftopen,theaccurrentthroughtheresistorwillhaveapeakvalueofIm.Thetemperaturereachedbythewaterisnowdeterminedbytheacpowerdissipatedintheformofheatbytheresistor.Theacinputisvarieduntilthetemperatureisthesameasthatreachedwiththedcinput.Whenthisisaccomplished,theaverageelectricalpowerdeliveredtotheresistorRbytheacsourceisthesameasthatdeliveredbythedcsource.Thepowerdeliveredbytheacsupplyatanyinstantoftimeis
Theaveragepowerdeliveredbytheacsourceisjustthefirstterm,sincetheaveragevalueofacosinewaveiszeroeventhoughthewavemayhavetwicethefrequencyoftheoriginalinputcurrentwaveform.Equatingtheaveragepowerdeliveredbytheacgeneratortothatdeliveredbythedcsource,
which,inwords,statesthat
theequivalentdcvalueofasinusoidalcurrentorvoltageis1/2_or0.707ofitsmaximumvalue.
Theequivalentdcvalueiscalledtheeffectivevalueofthesinusoidalquantity.
Insummary,
Asasimplenumericalexample,itwouldrequireanaccurrentwithapeakvalueof2_(10)_14.14AtodeliverthesamepowertotheresistorinFig.13.52asadccurrentof10A.Theeffectivevalueofanyquantityplottedasafunctionoftimecanbefoundbyusingthefollowingequationderivedfromtheexperimentjustdescribed:
which,inwords,statesthattofindtheeffectivevalue,thefunctioni(t)mustfirstbesquared.Afteri(t)issquared,theareaunderthecurveisfoundbyintegration.ItisthendividedbyT,thelengthofthecycleort
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 单片机 超声波 测距 系统 研究 设计 毕业论文 外文 文献 翻译 原文