機(jī)械設(shè)計制造和自動化畢業(yè)設(shè)計外文翻譯

..英文原文名ADVANCEDWEIGHINGTECHNOLOGY中文譯名現(xiàn)代稱重技術(shù)..現(xiàn)代稱重技術(shù)第一章秤的功能與結(jié)構(gòu)1.1基本結(jié)構(gòu)和稱重原理兩種不同類型的機(jī)械秤示于圖1.1。那么,秤的基本結(jié)構(gòu)和稱重原理方面的共同特征是什么呢？對于圖1.1<a>所示的天平或杠桿秤,放在載荷盤上的被測物體的質(zhì)量,與放在砝碼盤上的砝碼的質(zhì)量是利用它們的自重對支點的力矩,通過計量杠桿進(jìn)行比較的。這也可以看作是對物體載荷產(chǎn)生的作用力與砝碼自重產(chǎn)生的反作用力進(jìn)行比較,而且兩者同時作用在計量杠桿上。對于圖1.1<b>所示彈簧秤,由彈簧伸長而產(chǎn)生的恢復(fù)力,應(yīng)被視為反作用力或抗力。綜上所述,我們認(rèn)識到通?？梢园殉臃纸獬扇齻€功能部分,即載荷接受部分或受載器,力比較部分、反力部分。載荷接受部分〔例如載荷盤等,它作為秤的一部分用于接受載荷,并將載荷產(chǎn)生的力施加到力比較部分上。反力部分〔例如,帶砝碼的砝碼盤或彈簧等,它作為秤的一部分產(chǎn)生反作用力,并將其施加到力比較部分上。力比較部分〔例如計量杠桿等,它作為秤的一部分接受以上兩種力。<a>天平或者杠桿秤<b>彈簧秤圖1.1機(jī)械秤的兩種類型當(dāng)我們檢查任何一種機(jī)械秤時,會注意到它們通常都具有以上結(jié)構(gòu)。所以,我們可以認(rèn)為這種結(jié)構(gòu)式秤的基本結(jié)構(gòu)。此外,測量是以物體質(zhì)量產(chǎn)生的作用力與反力部分產(chǎn)生的反作用力之間的平衡為基礎(chǔ)的。所以,我們可以認(rèn)為秤的稱重原理是利用了力的平衡?，F(xiàn)代科技的發(fā)展,使我們在質(zhì)量測量方面不僅能夠利用力的靜平衡,而且還可以利用力的動平衡。載荷傳遞杠桿應(yīng)該包括在載荷接受部分之中。對于料斗秤中稱重傳感器直接支撐料斗的情形,可以認(rèn)為它屬于力比較部分被省略的一種特例。對于天平或杠桿秤,其測得值可以從反力部分上的砝碼變化中獲得。對于彈簧秤,其測得值可以從反力部分的彈簧伸長變化中獲得。一般來說,機(jī)械秤的測得值可以從反力部分產(chǎn)生的某些量值變化中獲得。1.2電秤和電子稱系統(tǒng)的構(gòu)成機(jī)械秤是指包括顯示功能在內(nèi)的所有功能都能通過機(jī)械手段實現(xiàn)的一種秤,而電秤和電子稱具有一個能將反力部分產(chǎn)生的變化轉(zhuǎn)換成電量的傳感器,還具有一個能處理電量信號以獲得測量值的信號處理裝置。所以,電秤和電子稱的特征在于有傳感器和信號處理裝置。圖1.2說明了電秤和電子稱的基本系統(tǒng)構(gòu)成。傳感器將轉(zhuǎn)化了的電信號,輸送給由3種基本電路組成的信號處理裝置,它們是輸入電路、數(shù)據(jù)處理電路、輸出電路。輸入電路上有例如濾波器、放大器、A/D轉(zhuǎn)換電路等,它們將傳感器的輸出信號變換成更適用于數(shù)據(jù)處理的信號。數(shù)據(jù)處理電路通過處理其輸入信號,來獲取測得值以及與測量有關(guān)的必須值。輸出電路則是傳輸處理好的測量結(jié)果的電路。圖1.2電秤和電子稱基本系統(tǒng)框圖按照反力部分是否承受了反作用力,可以將傳感器如圖1.3所示劃分為兩類,即非反力型傳感器和反力型傳感器。圖1.3秤用傳感器按是否承受反力所作的分類1.3工業(yè)秤的功能及其系統(tǒng)構(gòu)成1.3.1功能特征和分類工業(yè)秤主要用于工業(yè)稱重,它們具有以下特征：對載荷接受部分的加載或卸載時自動進(jìn)行的。用物體自重W確定物體質(zhì)量值M的過程是自動進(jìn)行的。這種秤的系統(tǒng)框圖示于圖1.4。此外大多數(shù)工業(yè)秤還有以下一個特征,即具有質(zhì)量值的控制功能。典型工業(yè)秤的名稱和功能列于表1.1。表1.1工業(yè)秤的名稱及其功能圖1.4工業(yè)自動秤的系統(tǒng)框圖1.3.2控制的目的若注意觀察一下加到載荷接受部分上的物體的質(zhì)量流動狀態(tài),及其與經(jīng)過測量后的物體的質(zhì)量流動狀態(tài)之間的差異,我們可以得知表1.1中所說的質(zhì)量值控制的目的就是為了控制質(zhì)量流動的狀態(tài)。從這個觀點出發(fā),料斗秤或包裝秤的控制目的,就是為了獲得一種斷續(xù)流動狀態(tài),而每次斷續(xù)流動的量都是預(yù)定的。聯(lián)合〔分選組合秤的控制目的也屬于這種類型。檢重秤的目的,是為了按照預(yù)定質(zhì)量等級獲得離散的流量動狀態(tài)。至于喂料的控制,則是為了獲得一個預(yù)定質(zhì)量的流動狀態(tài),或者獲得一個總量與預(yù)定值相同的流量東狀態(tài)。1.3.3系統(tǒng)的結(jié)構(gòu)一個控制系統(tǒng)通常包括被控對象、檢測部分、調(diào)節(jié)部分或控制器,以及操作部分。在工業(yè)稱重系統(tǒng)中,被控對象包括供料裝置、分配裝置、排放裝置、而被控變量就是被測質(zhì)量。圖1.4所示的系統(tǒng)相當(dāng)于一個檢測部分,而各種執(zhí)行器則用于操作部分。圖1.5顯示了從系統(tǒng)構(gòu)成觀點對工業(yè)稱重系統(tǒng)的分類情況。圖1.5〔a所示為料斗秤或包裝秤的系統(tǒng)構(gòu)成圖。被控對象是供料裝置,其典型實例為螺旋喂料器。此時操作部分是驅(qū)動喂料器的一個變速電機(jī)。稱量斗相當(dāng)于載荷接受部分。目標(biāo)值用符號R表示,操作變量用符號C表示。符號m和m＇分別代表質(zhì)量流動的狀態(tài)；用不同的符號意指兩種狀態(tài)有所不同。圖1.5〔b所示為一臺喂料秤的系統(tǒng)構(gòu)成圖,它的典型實例是一臺變速的皮帶喂料秤,載荷接受部分皮帶稱重段和稱重托輪組成。被控對象時皮帶喂料器或供料裝置,而操作部分是變速點擊,被檢測質(zhì)量的總量用符號Q表示。選擇Q或其對時間的導(dǎo)數(shù)Q＇為被控變量,為了得到Q值,就需要測量皮帶的運行速度v。圖1.5〔c所示為一臺檢重秤的系統(tǒng)構(gòu)成圖。被控對象是分配裝置,而皮帶輸送機(jī)通常被用作載荷接受部分。圖1.5〔d所示為一臺聯(lián)合〔分選組合秤的系統(tǒng)構(gòu)成圖,通常以一些小的稱量斗作為載荷接受部分,并且每個斗都裝有一個用執(zhí)行器控制的閥門。這些閥門就是被控對象,而執(zhí)行器即為控制元件操作部分。對于圖1.5〔a和1.5〔b中所示的秤,由于在測量質(zhì)量的同時必須控制質(zhì)量的流動狀態(tài),所以應(yīng)采用反饋控制。另一方面,對于圖1.5〔c和〔d中所示的秤,由于對質(zhì)量流動狀態(tài)的控制是在測量質(zhì)量之后進(jìn)行的,所以基本上是進(jìn)行順序控制?！瞐料斗秤的系統(tǒng)框圖〔b喂料秤的系統(tǒng)框圖〔c檢重秤的系統(tǒng)框圖〔d聯(lián)合秤〔分選組合秤的系統(tǒng)框圖圖1.5工業(yè)稱重系統(tǒng)的構(gòu)成框圖秤的靜力學(xué)2.1杠桿的靜力學(xué)2.1.1杠桿的分類通常把具有交點軸,載荷軸和力軸的直杠桿稱為基本杠桿。每個軸的位置分別被稱為支點、重點和力點。支點就是杠桿的支承點,杠桿可以圍繞它轉(zhuǎn)動。重點和力點分別是載荷和力的作用點。按照以上3個點的分布,可以把基本的杠桿分為3種類型,即第一類杠桿,第二類杠桿和第三類杠桿。在圖2.1所示的分類圖中,F是支點,A是重點,B是力點,它們作用在同一直線上。第一類杠桿〔b第二類杠桿〔c第三類杠桿圖2.1杠桿的分類按照聯(lián)接杠桿的數(shù)量可以將杠桿〔系稱為單一杠桿或復(fù)合杠桿〔系。單一杠桿是獨立的,例如天平的橫梁,而復(fù)合杠桿則是由相關(guān)聯(lián)的杠桿組合而成的一個杠桿系。支點、重點和力點的數(shù)量,在一個杠桿上并不限于一個。例如對于圖2.2所示的杠桿,我們可以看作是一個雙聯(lián)杠桿,它有兩個支點和兩個重點。包含這種雙聯(lián)杠桿的一個符合杠桿系,見圖2.3所示。圖2.2雙聯(lián)杠桿圖2.3復(fù)合杠桿系

2.1.2單一杠桿在實際應(yīng)用中,杠桿在載荷作用下保持其靜平衡位置的情況有兩種：第一,總是與空載下杠桿的平衡位置相一致〔第一種情況；第二,平衡位置隨載荷而變化〔第二種情況。當(dāng)我們研究以上兩種情況下的靜平衡條件時,我們將杠桿設(shè)想為一個剛體。靜平衡條件,單一杠桿保持平衡的必要和充分條件是Σ〔諸力=0和Σ〔諸力矩=0〔2.1為了研究單一杠桿在第一種情況和第二種情況下的靜平衡條件,我們將上述充分必要條件應(yīng)用于那些支點、力點和重點不在同一直線上的杠桿。假設(shè)當(dāng)載荷為零時,杠桿在初始力的作用下保持靜平衡,如圖2.4所示。W0作用于A點,P0作用于B點,R0作用于F點,G作用于C點〔重心。再假設(shè)當(dāng)施加載荷W和反力P時,杠桿仍保持在相同的位置上。那么,靜平衡條件在加載前后即為W0+P0+G+R0=0W0a+P0b+Gc=0〔2.2并且〔W0+W>+<P0+P>+G+<R0+R>=0<W0+W>a+<P0+P>b+Gc=0〔2.3式中,R是作用于F點的力的增量。在圖2.4中,我們必須考慮力的符號和作用點。向下的力為正,而向上的力為負(fù),以支點為原點,當(dāng)力的作用點位于重點一方時為正,而位于力點一方時為負(fù)。所以,逆時針方向的力矩為正,順時針的力矩為負(fù)。圖2.4單一杠桿的靜平衡條件ADVANCEDWEIGHINGTECHNOLOGYCHAPTER1FUNCTIONSANDSTRUCTURESOFSCALES1.1BASICSTRUCTUREANDWEIGHINGPRINCIPLETwodifferenttypesofthemechanicalscaleareillustratedinFig.1.1.Whatarethecommonfeaturestothescalesinbasicstructureandweighingprinciple?<a>Balance<b>SpringscaleFigure1.1MechanicalscaleInthebalanceorleverscaleillustratedinFig.1.1<a>,themassoftheobjecttobemeasuredandlocatedattheloadplateiscomparedwiththemassoftheweightstobelocatesattheweightplateasthemomentsduetotheirgravityaroundthefulcrumbymeansoftheweighbeam.Thiscanbeconsideredacomparisonoftheforceduetotheloadofobjectwithcounterforceduetotheweights,bothactingontheweighbeam.AsforthespringscaleillustratedinFig.1.1<b>,therestoringforceduetotheelongationofspringisconsideredthecounterforceorresistant.Theaboveconsiderationleadsustotherecognitionthatthosescalescanbedividedintothreefunctionalelementsincommon,whicharetheloadreceivingelementorloadreceptor,theforcecomparingelementandthecounterforeelement.Theloadreceivingelement,suchadaloadplate,isaportionofthescalewhichreceivesanobjecttobemeasuredandappliestheforcecausedbythemassoftheobjecttotheforcecomparingelement.Thecounterforceelement,suchasaweightplatewithweightsoraspring,isaportionofthescalewhichdevelopsacounterforce,applyingittotheforcecomparingelement.Theforcecomparingelement,suchasaweighbeam,isaportionofthescaletowhichtheabovetwoforcesareapplied.Whenexamininganytypesofthemechanicalscale,wenoticetheyhavetheabovestructureincommon.Then,thestructurecanberegardedasthebasicstructureofscales.Furthermore,themeasurementisbasedontheequilibriumintheforceduetothemassofanobjectandthecounterforcedevelopedinacounterforceelement.Therefore,theapplicationoftheequilibriuminforcescanberegardedastheweighingprincipleofscales.Themoderntechnologicaldevelopmentenablesustoapplynotonlythestaticequilibriumbutalsothedynamicequilibriuminforcesformassmeasurement.Theloadtransmittingleversshouldbeincludedintheloadreceivingelement.Forthehopperscalewhosehopperisdirectlysupportedbyloadcclls,weshouldregarditasacasethattheforcecomparingelementisomitted.Inthebalanceorleverscale,themeasuredvaluecanbeobtainedfromtheweightchangeinthecounterforceelement.Inthespringscalethemeasuredvaluecanbeobtainedfromtheelongationchangeofthespringasacounterforceelement.Generally,themeasuredvalueinthemechanicalscalecanbeobtainedbyusingsomequantitychangesdevelopedinthecounterforceelement.1.2SYSTEMCONFIGURATIONOFELECTRICALANDELECTRONICSCALESAmechanicalscaleisascaleinwhichallfunctionsincludingdisplayfunctionarerealizedbymechanicalmeans.Onthehand,anelectricalandelectricalscaleisascalewithatransducerwhichinvertsthechangedevelopedinthecounterforeelementtoanelectricalquantityandwithasignalprocessingdevicewhichprocessesthesignalofthatelectricalquantitytoobtainthemeasuredvalue.Therefore,theelectricalandelectronicscalearecharacterizedbythetransducersandsignalprocessingdevices.Figure1.2showsthebasicsystemconfigurationoftheelectricalandelectronicscale.Theelectricalsignalconvertedwiththetransducerissenttothesignalprocessingdevicecomposingofthreefunctionalcircuits,whichareinputcircuit,dataprocessingcircuit,andoutputcircuit.Theinputcircuitfunctionalcircuits,whichareinputcircuit,dataprocessingcircuit,andoutputcircuit.Theinputcircuitisassociatedwiththecircuits,suchasfiltering,amplifyingandA/Dconvertingcircuits,whichmanipulatetheoutputsignalfromthetransducerintoamoreusablesignalfordataprocessing.Thedataprocessingcircuitisacircuitwhichprocessestheinputsignaltoobtainthemeasuredvalueandthenecessaryvaluesrelatedtothemeasurement.Theoutputcircuitisacircuitwhichsendouttheprocessedresults.Figure1.2basicsystemconfigurationoftheelectricalandelectronicscaleAccordingtowhetherornottheyundertakethecounterforcesascounterforceelements,thetransducersareclassifiedintotwotypeswhicharethenoncounterforce-typeandthecounterforce-typetransducer,asshowninFig.1.3.Figure1.3Classificationoftransducers1.3FUNCTIONSANDSYSTEMCONFIGURATIONSOFTHESCALESFORINDUSTRIALUES1.3.1FunctionalCharacteristicsandClassificationThescalesmainlyusedforindustrialweighinghacethefollowingfeatures:1>Theloadingonandunloadingfromtheloadreceivingelementareautomatic.2>thedeterminationprocessofthemassvalueMoftheobjectbyusingitsweightWisautomatic.ThesystemconfigurationofsuchscalesisshowninFig.1.4.Inaddition,mostofthescaleshavethefollowingfeature:3>Thescalehasafunctionofmasscontrol.ThenameandfunctionofrepresentativescalesforindustrialusearetabulatedinTable1.1Table1.1IndustrialscalesandtheirfunctionsFigure1.4Systemconfigurationofthescaleforindustrialuse1.3.2ControlPurposePayingattentiontothedifferenceofthemassflowoftheobjectbeingfedontotheloadreceivingelementandthemassflowoftheobjectafterthemeasurement,wecouldsaythepurposeofthemasscontrolwrittenintable1.1ismassflowcontroloftheobject.Fromthispointofview,thecontrolpurposeofthehopperscaleortheweighpackeristoattainanintermittentfloweachamountofwhichispre-determined.Theassociative<selectivecombination>weigherisalsoregardedasthistypeofcontrol.Thecontrolpurposeofthecheckweigheristoattainthedivergingflowsaccordingtothepre-determinedgradesinmass.Asfortheweighfeeder,thepurposeistoattainaflowofpre-determinedflowrateinmassortoattainaflowthetotalamountofwhichcoincideswiththepre-determinedvalue.1.3.3SystemConfigurationsGenerally,acontrolsystemiscomposedofacontrolledobject,detectingmeans,controllingmeansorcontrollerandcontrolelement.Intheindustrialweighingsystems,thecontrolledobjectsincludethefeedingdevices,distributingdevices,anddischargingdevices,andmassisthecontrolledvariable.ThesystemshowninFig.1.4correspondstothedetectingmeans,andvariouskindsofactuatorsareusedasthecontrolelement.Figure1.5showstheclassification,fromtheviewpointofthesystemconfiguration,oftheindustrialweighingsystems.ThesystemconfigurationofahopperscaleoraweighpackerisshowninFig.1.5<a>.Thecontrolledobjectisafeedingdevice,whosetypicalexampleisascrewfeeder.Thecontrolelementisavariablespeedmotordrivingthefeederinthecase.ThehoppercorrespondstotheloadreceivingelementThedesiredvalueisdenotedbythesymbolRandthemanipulatedvariablethesymbolC.Thesymbolsmandm＇representrespectivelythestatesofmassflowandthedifferencesinsymbolmeanthedifferencesbetweenthetwostates.Figure1.5<b>showsthesystemconfigurationofaweighfeeder,thetypicalexampleofwhichisavariablespeedbelt-feeder.Theloadreceivingelementiscomposedofaportionofthebeltandtheweighroller<s>.Thecontrolledobjectisthebelt-feederandthecontrolelementisthevariablespeedmotor.ThetotalamountofthedetectedmassisdenotedbythesymbolQ.EitherQoritsderivativeQ＇ischosenasthecontrolledvariableandthemeasurementofthebeltspeedVisneededforobtainingthevalueQ.Figure1.5<c>showsthesystemconfigurationofacheckweigher.Thecontrolledobjectisthedistributingdeviceandthebeltconveyerisnormallyadoptedastheloadreceivingelement.Figure1.5<d>showsthesystemconfigurationofanassociative<selectivecombination>weigher.Normally,smallhoppersareusedfortheloadreceivingelements,eachofwhichisequippedwithagatecontrolledbyanactuator.Thegatesarecontrolledobjectsandtheactuatorsarethecontrolelements.ForthescalesshowninFigs.1.5<a>and1.5<b>,feedbackcontrolisadoptedsincethemassflowcontrolhastobecarriedoutwhilemeasuringthemass.Ontheotherhand,forthescalesshowninFigs.1.5<c>and1.5<d>,themassflowcontrolisfundamentallysequentialcontrolsincethecontroliscarriedoutafterthemeasurementofthemass.<a>Hopperscaleorweighpacker<b>Weighfeeder<c>Checkweigher<d>AssociativeweigherFigure1.5IndustrialscaleswithmasscontrolCHAPTER2STATICEOFSCALES2.1STATICEOFLEVERS2.11ClassificationofLeversAstraightlevernormallyhasafulcrumpivot,loadpivot,andpowerpivot,whichisreferredtoasthefundamentallever.Eachpositionofthepivotsisreferredrespectivelytoasfulcrumpoint,theloadpoint,andthepowerpoint.Thefulcrumpointisapointatwhichaleverissupportedandaboutwhichitisvibrationable.Theloadandpowerpointsarepointsatwhichaloadandcounterbalancingforceareapplied,respectively.Fundamentalleversareclassifiedintothreetypesaccordingtothearrangementoftheabovethreepoints;thefirst-orderlever,thesecond-order-lever,andthethird-order-lever.ThedetailisshowninFig.2.1inwhichpointFisthefulcrumpoint,pointAtheloadpoint,andpointBthepowerpoint,beinginastraightline.First-orderlever<b>Second-orderlever<c>Third-orderleverFigure2.1ClassificationofleversThelever<system>iscalledthesingleleverorthecompoundlever<system>accordingtothenumberofconnectedlevers.Thesingleleverisaleverusedindependently,suchasaweighbeamofbalance,andthecompoundleverisaleversystemcomposedofconnectedlevers.Eachnumberofthefulcrumpoint,loadpoint,andpowerpointisnotlimitedtoonepointforonelever.Forexample,TheleverillustratedinFig.2.2,whichmayberegardedasatwo-unitedlever,hastwofulcrumpointandtwoloadpoints.AcompoundleversystemincludingsuchleversisshowninFig.2.3.Figure2.2Atwo-unitedleverFigure2.3Compoundleversystem2.12SingleleversInpracticalapplication,therearetwocasesastothepositionofaleverinstaticequilibriumunderloading;thecasethatthepositionisalwaysidenticalwiththepositionunderazeroload<Case1>,andthecasethatthepositionvariesastheload<Case2>.Weexaminethestat