基于PLC物料自動(dòng)分揀系統(tǒng)的畢業(yè)設(shè)計(jì)

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畢業(yè)設(shè)計(jì)（論文）外文文獻(xiàn)翻譯外文翻譯PLC今天PLC(programmablelogicalcontroller)，可編程序邏輯控制器)面臨著更為復(fù)雜的挑戰(zhàn)。當(dāng)初，它們悄悄地取代了繼電器、接觸器并時(shí)不時(shí)見(jiàn)諸于公司主框架的報(bào)告。而今，他們已經(jīng)組成了各種單元、被賦予新的任務(wù)、使用新的語(yǔ)言，并面臨著與各種新型控制產(chǎn)品競(jìng)爭(zhēng)。作為每年一度PLC技術(shù)最新報(bào)道，我們請(qǐng)教了PLC市場(chǎng)銷(xiāo)售人員，制作了這個(gè)專(zhuān)刊。編程語(yǔ)言高級(jí)PLC編程語(yǔ)言已經(jīng)在有些方面很普及，但是最近高級(jí)編程語(yǔ)言已經(jīng)迅速發(fā)展。西門(mén)子的總經(jīng)理兼生產(chǎn)部長(zhǎng)指出：“可編程控制在被廣泛的應(yīng)用與于精密操作，除了梯形圖邏輯以外的編程語(yǔ)言變得更加實(shí)用、有效和強(qiáng)大。例如，用梯形圖邏輯寫(xiě)一個(gè)三角函數(shù)公式是非常困難的?！北唤邮盏恼Z(yǔ)言包括Boolean,控制系統(tǒng)流程圖編制，和如公式編制語(yǔ)言Graphtec和與它類(lèi)似的語(yǔ)言，并且還有增加的重要語(yǔ)言如C語(yǔ)言和BASIC語(yǔ)言。過(guò)程控制中的PLCPLC還沒(méi)有廣泛的應(yīng)用于過(guò)程控制中。是否會(huì)一直這樣下去呢？北美GEFanuc一系列和六系列的生產(chǎn)企劃經(jīng)理KenJeannette說(shuō)：“我覺(jué)得PLC將被用于過(guò)程控制但是對(duì)于過(guò)程控制又不是必須的?！币恍S(chǎng)家十分確定PLC不會(huì)廣泛用于過(guò)程控制。RichRyan經(jīng)理提到PLC在食品、化學(xué)和石油等工業(yè)領(lǐng)域越來(lái)越多的應(yīng)用。他認(rèn)為PLC適合應(yīng)用于場(chǎng)合有兩種，他說(shuō)：“第一，過(guò)程控制系統(tǒng)的型號(hào)不適合離散控制系統(tǒng)，剛開(kāi)始這些產(chǎn)品的價(jià)格非常的高。而一個(gè)可編程控制器以它的體積小，價(jià)格低順理成章的被應(yīng)用。第二，你必須把電路和邏輯緊密的結(jié)合起來(lái)。例如，一組基本的控制器，連續(xù)的過(guò)程變量緊密的互相聯(lián)系在一起，以至于用可編程控制器來(lái)完成一系列的邏輯勝過(guò)沒(méi)有離散控制器的系統(tǒng)?！盩riconex的總裁BillBarkovitz預(yù)測(cè):“今后所有的控制器在過(guò)程控制系統(tǒng)的業(yè)務(wù)將引用更多的PLC技術(shù)，PLC功能比以往任何時(shí)候都要多?！蓖ㄐ藕蜕a(chǎn)自動(dòng)化協(xié)議（MAP）通信對(duì)于個(gè)人自動(dòng)單元和自動(dòng)化產(chǎn)業(yè)是很重要的。在過(guò)去的幾年里，我們聽(tīng)到許多關(guān)于生產(chǎn)自動(dòng)化協(xié)議的事情，并且許多公司已經(jīng)加入大有成功希望的事業(yè)。然而，當(dāng)一個(gè)完善的生產(chǎn)自動(dòng)化協(xié)議說(shuō)明書(shū)沒(méi)有及時(shí)出現(xiàn)時(shí)許多公司都很失望。LarryKotare說(shuō):”現(xiàn)在，生產(chǎn)自動(dòng)化協(xié)議仍然是生產(chǎn)中一個(gè)發(fā)展的對(duì)象，一個(gè)說(shuō)明書(shū)并不是最終的結(jié)果。例如，雖然當(dāng)新的生產(chǎn)自動(dòng)化協(xié)議MAP3.0版本使用之時(shí)以MAP2.1版本為基礎(chǔ)的產(chǎn)品將會(huì)被汰，但是現(xiàn)在人們?nèi)匀粚a(chǎn)品用于MAP2.1版。由于這些原因，許多PLC廠(chǎng)家緊盯著MAP的最新成果。如歐姆龍公司正在進(jìn)行一個(gè)有關(guān)MAP兼容性的項(xiàng)目。但是歐姆龍生產(chǎn)部門(mén)總經(jīng)理FrankNewborn說(shuō)由于缺少一個(gè)固定的標(biāo)準(zhǔn)，歐姆龍的產(chǎn)品并不涉及到MAP。由于個(gè)體PLC不可能無(wú)論何時(shí)廣泛的涉及到MAP，生產(chǎn)廠(chǎng)家正在考慮專(zhuān)用網(wǎng)絡(luò)。根據(jù)SalProbanzano的說(shuō)法，用戶(hù)擔(dān)心如果他們廣泛的應(yīng)用生產(chǎn)廠(chǎng)家將會(huì)收回MAP，這樣將會(huì)留下一個(gè)不支持通信的交流框架。通用的I/O然而關(guān)于PLC的兼容問(wèn)題不同廠(chǎng)商的仍有顧慮，在另一端連接的I/O問(wèn)題，更是支離破碎的。除了少數(shù)例外，I/O仍然是專(zhuān)有技術(shù)。然而，還是有那些覺(jué)得I/O最終將更普及。GEFanuc希望用它的智能I/O線(xiàn)這么做。各個(gè)獨(dú)立I/O制造商都在向同一方向進(jìn)發(fā)。許多人說(shuō)，I/O是這樣一個(gè)高價(jià)值項(xiàng)目，PLC制造商將永遠(yuǎn)希望保持它的專(zhuān)有性。就像KenJannotta說(shuō)的：“I/O將在硬件銷(xiāo)售中不成比例。當(dāng)然每個(gè)PLC供應(yīng)商將試圖保護(hù)這一點(diǎn)?！背鲇谶@個(gè)原因，他說(shuō)，PLC的制造商將不會(huì)開(kāi)始銷(xiāo)售其他廠(chǎng)商的通用I/O?！叭绻覀冮_(kāi)始銷(xiāo)售那種產(chǎn)品，那我們還有什么可生產(chǎn)的？”Jannotta說(shuō)道。隨著更多智能I/O出現(xiàn)，SalProvanzano認(rèn)為在不同的制造商中間這將導(dǎo)致更多的分化?！爱?dāng)I/O變得非常只能，并成為系統(tǒng)的一部分，到底哪個(gè)是I/O,哪個(gè)是CPU真的很難定義。如果你愿意，CPU也同樣可以納入I/O的系統(tǒng)”。PLC的I/O和個(gè)人電腦的連接雖然不同的PLC廠(chǎng)商可能會(huì)繼續(xù)用專(zhuān)有的I/O，但一些廠(chǎng)商使I/O連接到IBMPC這樣的兼容設(shè)備成為可能。Alle-bradeley和辛辛那提米拉克龍公司已經(jīng)擁有，并有傳言說(shuō)，GE計(jì)劃將沿著同樣的思路。BillKetelhut,GEFanuc北美的產(chǎn)品規(guī)劃經(jīng)理，認(rèn)為是I/O的普及“我覺(jué)得多個(gè)主機(jī)接口將代替I/O?！彼f(shuō)。朱迪格洛爾，SquareD自動(dòng)化產(chǎn)業(yè)市場(chǎng)經(jīng)理，將PLC看做是工業(yè)電腦。PLC和個(gè)人電腦如果IBM7552，行動(dòng)儀器BC22，和其他計(jì)算機(jī)出現(xiàn)在工廠(chǎng)，這難道不意味著對(duì)PLC的新競(jìng)爭(zhēng)?！坝幸恍?duì)于更有利于電腦的控制功能。可編程程序控制器被迫適應(yīng)的這些要求?！盧ichRyan說(shuō)。然而，在我們調(diào)查的廠(chǎng)商多數(shù)不認(rèn)為“個(gè)人電腦入侵”將對(duì)他們產(chǎn)生影響。大多數(shù)人說(shuō)，PLC和PC除架構(gòu)之外，他們通常會(huì)做足夠的控制。他們認(rèn)為PC會(huì)做PLC的工作緊緊是因?yàn)楝F(xiàn)在PLCI/O模塊能跟PC連接。他們相信這只是意味著，PLC和個(gè)人電腦將能夠共享相同的數(shù)據(jù)。富瑞恩說(shuō)：“通用的計(jì)算機(jī)和可編程控制器內(nèi)在結(jié)構(gòu)不同，硬件結(jié)構(gòu)有內(nèi)置到幾乎每一個(gè)制造商的可編程控制器。如今定制的硬件來(lái)運(yùn)行梯形邏輯，解決機(jī)器代碼。”他引用的一個(gè)根本的區(qū)別稱(chēng)呼為“機(jī)器狀態(tài)”富瑞安說(shuō)：“當(dāng)你關(guān)閉機(jī)器，或中斷周期，或者跳轉(zhuǎn)到另一個(gè)周期，可編程控制器本身記得機(jī)器的狀態(tài)：定時(shí)器狀態(tài)是什么，計(jì)數(shù)器狀態(tài)是什么，鎖存的狀態(tài)是什么,但計(jì)算機(jī)本身不這樣做。PLCPLCs (programmable logical controller) face ever more complex challengesthesedays.Whereoncetheyquietlyreplacedrelaysandgaveanoccasionalreporttoacorporatemainframe,theyarenowgroupedintocells,givennewjobandnewlanguages,andareforcedtocompeteagainstagrowingarrayofcontrolproducts.ForthisyearsannualPLCtechnologyupdate,wequeriedPLCmakersonthesetopicsandmore.ProgramminglanguagesHigherlevelPLCprogramminglanguageshavebeenaroundforsometime,butlatelytheirpopularityhasmushrooming.AsRaymondLeveille,vicepresident&generalmanager,SiemensEnergy&Automation.inc;Programmablecontrolsarebeingusedformoreandmoresophisticatedoperations,languagesotherthanladderlogicbecomemorepractical,efficient,andpowerful.Forexample,itsverydifficulttowriteatrigonometricfunctionusingladderlogic.LanguagesgainingacceptanceincludeBoolean,controlsystemflowcharting,andsuchfunctionchartlanguagesasGraphcetanditsvariation.AndtheresincreasinginterestinlanguageslikeCandBASIC.PLCsinprocesscontrolThusfar,PLCshavenotbeenusedextensivelyforcontinuousprocesscontrol.Willthiscontinue?ThefeelingthatIvegotten,saysKenJannotta,manger,productplanning,seriesOneandSeriesSixproduct,atGEFanucNorthAmerica,isthatPLCswillbeusedintheprocessindustrybutnotnecessarilyforprocesscontrol.Severalvendors-obviouslybettingthattheoppositewillhappen-haveintroducedPLCsoptimizedforprocessapplication.RichRyan,manger,commercialmarketing,Allen-bradleyProgrammableControlsDiv.,citesPLCssincreasingusesuchindustriesasfood,chemicals,andpetroleum.Ryanfeelstherearetwotypesofapplicationsinwhichtheyreappropriate.one,hesays,iswherethesizeoftheprocesscontrolsystemthatsbeingautomateddoesntjustifyDCSdistributedcontrolsystem.Withthestartingpricetagsofchoseproductsbeingrelativelyhigh,aprogrammablecontrollermakessenseforsmall,lowloopcountapplication.Thesecondiswhereyouhavetointegratetheloopcloselywiththesequentiallogical.Batchcontrollersareprimeexample,wherethesequenceandmaintainingtheprocessvariableareintertwinedsocloselythatthebenefitsofhavingaprogrammablecontrollertodothesequentiallogicaloutweighssomeofthedisadvantagesofnothavingadistributedcontrolsystem.BillBarkovitz,presidentofTriconex,predictsthatallfuturecontrollersthatcomeoutintheprocesscontrolsystembusinesswillembracealotofmorePLCtechnologyandalotmorePLCfunctionalitythantheyeverdidbefore.CommunicationsandMAPCommunicationsarevitaltoanindividualautomationcellandtobeautomatedfactoryasawhole.WeveheardalotaboutMAPinthelastfewyears,andalotofcompanieshavejumpedonthebandwagon.Many,however,weredisappointedwhenafully-definedandcompletedMAPspecificationdidntappearimmediately.SaysLarryKomarek:Rightnow,MAPisstillamovingtargetforthemanufacturers,aspecificationthatisnotfinal.Presently,forexample.peopleareintroducingproductstomeettheMAP2.1standard.Yet2.1-basedproductswillbeobsoletewhenthenewstandardforMAP3.0isintroduced.Becauseofthis,manyPLCvendorsareholdingoffonfullMAPimplementations.Omron,forexample,hasanongoingMAP-compatibilityprogram;butFrankNewburn,vicepresidentofOmronsIndustrialDivision,reportsthatbecauseofthelackofafirmdefinition,OmronsPLCsdontyettalktoMAP.SinceitsunlikelythatanindividualPLCwouldtalktobroadMAPanyway,makersareconcentratingonproprietarynetworks.AccordingtoSalProvanzano,usersfearthatiftheydogetonboardandvendorswithdrawfromMAP,theyllbetheonesleftholdingacommunicationsstructurethatsnotsupported.UniversalI/OWhilethereareconcernsaboutthelackofcompatiblecommunicationsbetweenPLCsfromdifferentvendors,theconnectionattheotherend-theI/O-isevenmorefragmented.Withrareexceptions,I/Oisstillproprietary.YettherearethosewhofeelthatI/Owilleventuallybecomemoreuniversal.GEFanucishopingtodothatwithitsGeniussmartI/Oline.TheindependentI/Omakersarepullinginthesamedirection.ManysaythatI/Oissuchahigh-valueitemthatPLCmakerswillalwayswantto keepitproprietary.AsKenJannotta,says:TheI/Oisgoingtobeadisproportionateamountofthehardwaresale.CertainlyeachPLCvendorisgoingtotrytoprotectthat.Forthatreason,hesays,PLCmakerswontbeginsellinguniversalI/Osystemfromothervendor.ifwestartsellingthatkindofproduct,saysjannotta,whatdowemanufacture?WithmoreintelligentI/Oappearing,SalProvanzanofeelsthiswillleadtomoredifferentiationamongI/Ofromdifferentmakers.WheretheI/Obecomesextremelyintelligentandbecomespartofthesystem,hesays,itreallyishardtodefinewhichistheI/OandwhichisCPU.ItreallyCPU,ifyouwill,isequallyintegratedintothesystemastheI/O.ConnectingPLCI/OtoPCsWhiledifferentPLCsprobablywillcontinuetouseproprietaryI/O,severalvendorsmakeitpossibletoconnect5theirI/OtoIBMPC-compatibleequipment.Alle-bradeley,Could,andCincinnatiMilacronalreadyhave,andrumorhasitthatGEisplanningsomethingalongthesesamelines.BillKetelhut,manageofproductplanningatGEFanucNorthAmerica,seesthissortofthingasalternativetouniversalI/O.Ithinkthetrend,insteadoftowarduniversalI/O,willbemultiplehostinterface,hesays.JodieGlore,directorofmarking,SquareDAutomationProducts,ViewsitasanotherindicationthatPLCsare,andhavebeenforsometime,industrialcomputers.PLCsandPCsIftheIBM7552,theActionInstrumentsBC22,andothercomputersareappearingonthefactoryfloor,wontthismeannewcompetitionforPLCs?RichRyan:Therearesomecontrolfunctionsthatarebetterjobsforcomputers.Programmablecontrollershavebeenforcedtofitintothoseapplications.Yet,themajorityofvendorswesurveyeddontlikethePCinvasionwillposeaproblemforthem.MostsaidthatPLCsandPCsareenoughapartinarchitecturethattheywillusuallydothecontrol.TheydontfeelthatPCswilltakejobsfromPLCsjustbecausePLCI/OmodulescannowbeconnectedtoPCs;theybelievethissimplymeansthatPLCsandPCswillbeabletosharethesamedata.Thereareinherentarchitecturaldifferencesbetweenageneralpurposecomputer,saysRichRyan,andaprogrammablecontroller.Therearehardwareconstructsbuiltintoalmosteverymanufacturesprogrammablecontrollertodaythatcustomizethehardwaretorunladderlogicandtosolvemachinecode.Onefundamentaldifferencehecitesiscalledstateofthemachine.Ryan:Whenyoushutthemachineoff,orinterruptthecycle,oryoujumptoanotherspotinthecycle,programmablecontrollersinherentlyrememberthestateofthemachine:whatthetimerswere,whatthecounterswere,whatthestatesofallthelatcheswere.Computersdontinherentlydothat.7