专科毕业设计.docx
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专科毕业设计.docx
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专科毕业设计
前言
随着电子信息技术的高速发展,单片机语言已进入了社会大力发展阶段,单片机之所以如此发展快,是因为它具有集成度高.功能强.结构简单.易于掌握.应有活.可靠性高.价格低廉等特点,被广泛用于工业控制,家用电器,通信设备,信息处理,尖锐武器等各个领域。
传感器技术也得到了高速发展,同样也用于各个科技与生活中。
而传感器原理大多是通过感知来获取信息,从而我们还须通过一定的技术来转换传感器输送来的信息,通过处理我们才能得到我们想要的结果。
本次设计的科目就是通过我们所学的专业知识的一个总结,利用单片机技术和传感器技术的融合,在通过其它技术的连接,比如:
EDA.PLC.ADC.双桥电路等专业知识的连接应用,才能的到我们设计的结果。
而且在设计中我们用了很多,单片机技术,比如:
硬件系统.软件系统.汇编语言.程序编辑.单片机C51.C52。
设计的结果是通过一个双温测控系统把所需要的数据测出在转入一个转换器,在通过很多程序编程来的到我们想要的结果。
摘要:
单片机和传感器的技术发展带动了科技与社会的进步。
同时单片机和传感器共同应用可以完成人们所需要的科技,如我们可完成一个双路温控测控系统,同时也可以更深刻的了解所学专业知识的重要性和广泛性。
也可以更前面的来学习和应用专业知识。
关键词:
单片机(singlechip)
温控传感器(TemperatureSensor)
转换器(converetr)
温控传感器
Abstract:
rollerandsensortechnologydriventechnologicaldevelopmentandsocialprogress.Microcontrollerandsensorapplicationsalsocancompletetogetherthetechnologythatpeopleneed,ifwecancompleteadualtemperaturecontrolsystem,butalsoamoreprofoundunderstandingoftheimportanceofprofessionalknowledgeandextensive.Canalsolearnmoreinfrontofandapplicationofprofessionalknowledge.
Antistop:
singlechip
TemperatureSensor
Converter
Temperaturesensor
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SingleLoopTemperatureControllers
Asinglelooptemperaturecontrollerisaninstrumentthattakesthesignalfromasensor,comparesittoasetpointsignal,andadjuststheoutputtotheheatingdevicetomaintain,ascloseaspossible,equilibriumbetweenthemeasuredtemperatureandthesetpointtemperature.Thekeyphrasehereis"ascloseaspossible".Thereareseveraltypesofcontrolmethodsusedtoaccomplishthis.Wewillattempttobrieflyexplainthemostcommon.
On-OffControl
Selectionoftherighttemperaturecontrollerfortheapplicationdependsonthedegreeofcontrolrequiredbytheapplication.Thesimplestofapplicationsmayonlyrequirewhatiscalled"On-Off"control.On-Offcontroloperatesmuchinthesamemannerasthethermostatonourhomeheatingsystems.Inotherwords,theoutputofthecontrolleriseither100%onor100%off.ThesensitivityoftheOn-Offcontrol(sometimescalled"hysteresis"or"dead-band")isdesignedintothecontrolactionbetweenthepointsatwhichthecontroloutputswitchesfrom"off"to"on".Thisdesignedinhysteresispreventstheoutputfromswitchingfromofftoontoorapidly.Ifthehysteresisissettoo"narrow",rapidswitchingwilloccurandoftenresultinwhatisknownasoutput"chattering".This"chattering"canresultinpoorlifetimeofoutputrelaysandheatingcomponents.Therefore,thehysteresisshouldbesetsothatthereissufficienttimedelaybetweenthe"on"and"off"modesoftheoutputs.Duetothehysteresisneededintheoutputoftheon-offcontroller,therewillalwaysbeacertain"undershoot"and"overshoot"inthecontrolaction.Theamountofundershootandovershootisdependentuponthecharacteristicsoftheentirethermalsystemofaparticularapplication.(Figure13A..)
TimeProportioning
ProcessesrequiringalittlemoreprecisecontrolthanOn-OffcontrolusuallyrequirewhatiscalledTimeProportioning.Atimeproportioningcontroloperatesmuchthesamewayasanon-offcontrolwhiletheprocesstemperatureisoutsideofwhatiscalledtheproportionalband.Theproportionalbandisthatareaaroundthesetpointinwhichtimeproportioningcontroltakesplaces.Whentheprocesstemperatureenterstheproportionalband(approachingsetpoint)thecycletimebetweentimeonandtimeoffbeginstovary.Atthelowendoftheproportionalband,theontimeismuchgreaterthantheofftime.Astheprocessgetsclosertothesetpoint,theontimedecreasesandtheofftimeincreases.Thischangestheeffectivepowertotheheatingloadandcausesa"throttlingback"inthespeedatwhichthetemperatureoftheprocessisincreased.Thisactioncontinuesuntilastabilizationtakesplacesomewherebelowthesetpoint.Atthispoint,controlisachieved.Thedifferenceinthecontrolpointandtheactualsetpointiscalled"droop".(Figure13B.)
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Integralor"ResetAction"
Ifthe"droop"inthetimeproportioningformofcontrolcannotbetoleratedintheprocess,theIntegralfunctionofcontrolmustbeadded.Theintegralfunctionfoundin"automaticreset"controllersusesamathematicalalgorithmtocalculatetheamountofdroopandthenadjuststheoutputto"reset"thecontrolresulttosetpoint.Thisisusuallydonebyautomaticallyshiftingtheproportionbandslightlytocompensateforthedroop.
Automaticresetactioncanonlytakeplacewithintheproportionalband.Shouldautomaticresetbeappliedoutsidetheproportionalband,theresultwouldbeaconditionofextremeovershootofthesetpoint.Theprocessofeliminatingtheautomaticresetoutsideoftheproportionalbandiscalled"anti-resetwindup"andistypicallyastandardfeatureofcontrolsthatincludetheautomaticresetor"integrating"function.Onmanycontrolsthatdonotoffer"automatic"reset.Thisfunctionisaccomplishedmanuallybyapotentiometeradjustmentthatmanuallyshiftstheproportionalband.(Figure14Aand14B)
Derivative(AutomaticRate)
Temperatureovershootiswhentheprocess,duringitscycling,exceedssetpoint.Overshootcanbesmallandinsignificantorlargeenoughtocausemajorproblemswiththeprocess.Inallthetypesofcontroldiscussedsofar,overshootoccurs.Overshootcanbedamaginginmanyprocessesandthereforemustbeavoided.
Thederivativefunction(alsocalled"automaticrate")canbeusedincontrolsystemstoprevent
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overshoot.Thederivativefunctionanticipateshowquicklythesetpointwillbereached.Itdoesthisbymeasuringtherateofchangeofprocesstemperatureandthenbyforcingthecontrolintoaproportioningactionatafasterratetherebyslowingdowntherateofprocesstemperaturechange.Thisactionallowstheprocesstemperatureto"glide"intothesetpointandtherebypreventalargedegreeofovershootonstart-upandwhensystemchangessuchaslargeloadchangesortheopeningofafurnacedoor,etc.takesplace.
Typically,themostpreciseofprocesscontrolapplicationswillrequireacontrolthathasproportional,automaticreset,andautomaticratefunctions.ThistypeofcontrolisknowasPID(Proportional,Integral,Derivative).(Figure14C)
ControlSystemTuning
On-OffControl:
TuninganOn-Offcontrolsystemisusuallyaccomplishedbyonesimplemanualadjustment.Thisadjustmentbasicallycontrolstheswitchinghysteresisbyadjustingthepointsatwhichthecontrolturnsonandturnsoff.
Proportional(P),ProportionalplusIntegral(PI),andProportionalplusIntegralplusDerivative(PID).
ThereareseveralmethodsforthepropertuningofP,PI,andPIDcontrols.Mostmethodsrequireaconsiderableamountoftrialanderroraswellasatechnicianendowedwithalotofpatience!
Thefollowingisoneofthosemethods.
Thefirststepisthetuningoftheproportionalband.IfthecontrollercontainsIntegralandDerivativeadjustments,tunethemtozerobeforeadjustingtheproportionalband.Theproportionalbandadjustmentselectstheresponsespeed(sometimescalledgain)aproportionalcontrollerrequirestoachievestabilityinthesystem.Theproportionalbandmustbewiderindegreesthanthenormaloscillationsofthesystembutnottoowidesoastodampenthesystemresponse.Startoutwiththenarrowestsettingfortheproportionalband.Ifthereareoscillations,slowlyincreasetheproportionalbandinsmallincrementsallowingthesystemtosettleoutforafewminutesaftereachstepadjustmentuntilthepointatwhichtheoffsetdroopbeginstoincrease.Atthispointtheprocessvariableshouldbeinastateofequilibriumatsomepointunderthesetpoint.
ThenextstepistotunetheIntegralorresetaction.Ifthecontrollerhasamanualresetadjustment,simplyadjusttheresetuntiltheprocessdroopiseliminated.Theproblemwithmanualresetadjustmentsisthatoncethesetpointischangedtoavalueotherthantheoriginal,the
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droopwillprobablyreturnandtheresetwillonceagainneedtobeadjusted.
Ifthecontrolhasautomaticreset,theresetadjustmentadjuststheautoresettimeconstant(repeatsperminute).Theinitialsettingshouldbeatthelowestnumberofrepeatsperminutestoallowforequilibriuminthesystem.Inotherwords,adjusttheautoresetinsmallsteps,allowingthesystemtosettleaftereachstep,untilminoroscillationsbegintooccur.Thenbackoffontheadjustmenttothepointatwheretheoscillationsstopandtheequilibriumisreestablished.Thesystemwillthenautomaticallyadjustforoffseterrors(droop).
ThelastcontrolparametertoadjustistheRateorDerivativefunction.Alwaysadjustthisfunctionlast.Always!
ThereasonIamsoemphaticonthispointisthatiftherateadjustmentisturnedonbeforetheresetadjustmentismade,theresetwillbepulledoutofadjustmentwhentherateadjustmentisturnedon.Thenyoujusthavetostartyourtuningprocedureover!
Thefunctionoftherateadjustmentistoreduceasmuchaspossibleanyovershoot.Therateadjustmentisatimebasedadjustmentmeasuredinminuteswhichistunedtoworkwiththeoverallsystemresponsetime.Theinitialrateadjustmentshouldbetheminimumnumberofminutespossible.Increasetheadjustmentinverysmallincrements.Aftereachadjustmentletitsettleoutafewminutes.Thenincreasethesetpointamoderateamount.Watchthecontrolactionasthesetpointisreached.Ifanovershootoccurs,increasetherateadjustmentanothersmallamountandrepeattheprocedureuntiltheovershootiseliminated.Sometimesthesystemwillbecome"sluggish"andneverreachsetpointatall.Ifthisoccurs,decreasetherateadjustmentuntiltheprocessreachessetpoint.Theremaystillbeaslightovershootb
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