PLC物料自动分拣系统毕业设计外文文献翻译模板

资料内容仅供您学习参考，如有不当或者侵权，请联系改正或者删除。外文翻译PLC今天PLC(programmablelogicalcontroller),可编程序逻辑控制器)面临着更为复杂的挑战。当初,它们悄悄地取代了继电器、接触器并时不时见诸于公司主框架的报告。而今,她们已经组成了各种单元、被赋予新的任务、使用新的语言,并面临着与各种新型控制产品竞争。作为每年一度PLC技术最新报道,我们请教了PLC市场销售人员,制作了这个专刊。编程语言高级PLC编程语言已经在有些方面很普及,可是最近高级编程语言已经迅速发展。西门子的总经理兼生产部长指出:”可编程控制在被广泛的应用与于精密操作,除了梯形图逻辑以外的编程语言变得更加实用、有效和强大。例如,用梯形图逻辑写一个三角函数公式是非常困难的。”被接收的语言包括Boolean,控制系统流程图编制,和如公式编制语言Graphtec和与它类似的语言,而且还有增加的重要语言如C语言和BASIC语言。过程控制中的PLCPLC还没有广泛的应用于过程控制中。是否会一直这样下去呢?北美GEFanuc一系列和六系列的生产企划经理KenJeannette说:”我觉得PLC将被用于过程控制可是对于过程控制又不是必须的。”一些厂家十分确定PLC不会广泛用于过程控制。RichRyan经理提到PLC在食品、化学和石油等工业领域越来越多的应用。她认为PLC适合应用于场合有两种,她说:”第一,过程控制系统的型号不适合离散控制系统,刚开始这些产品的价格非常的高。而一个可编程控制器以它的体积小,价格低顺理成章的被应用。第二,你必须把电路和逻辑紧密的结合起来。例如,一组基本的控制器,连续的过程变量紧密的互相联系在一起,以至于用可编程控制器来完成一系列的逻辑胜过没有离散控制器的系统。”Triconex的总裁BillBarkovitz预测:”今后所有的控制器在过程控制系统的业务将引用更多的PLC技术,PLC功能比以往任何时候都要多。”通信和生产自动化协议(MAP)通信对于个人自动单元和自动化产业是很重要的。在过去的几年里,我们听到许多关于生产自动化协议的事情,而且许多公司已经加入大有成功希望的事业。然而,当一个完善的生产自动化协议说明书没有及时出现时许多公司都很失望。LarryKotare说:”现在,生产自动化协议依然是生产中一个发展的对象,一个说明书并不是最终的结果。例如,虽然当新的生产自动化协议MAP3.0版本使用之时以MAP2.1版本为基础的产品将会被汰,可是现在人们依然将产品用于MAP2.1版。由于这些原因,许多PLC厂家紧盯着MAP的最新成果。如欧姆龙公司正在进行一个有关MAP兼容性的项目。可是欧姆龙生产部门总经理FrankNewborn说由于缺少一个固定的标准,欧姆龙的产品并不涉及到MAP。由于个体PLC不可能无论何时广泛的涉及到MAP,生产厂家正在考虑专用网络。根据SalProbanzano的说法,用户担心如果她们广泛的应用生产厂家将会收回MAP,这样将会留下一个不支持通信的交流框架。通用的I/O然而关于PLC的兼容问题不同厂商的仍有顾虑,在另一端连接的I/O问题,更是支离破碎的。除了少数例外,I/O依然是专有技术。然而,还是有那些觉得I/O最终将更普及。GEFanuc希望用它的智能I/O线这么做。各个独立I/O制造商都在向同一方向进发。许多人说,I/O是这样一个高价值项目,PLC制造商将永远希望保持它的专有性。就像KenJannotta说的:”I/O将在硬件销售中不成比例。当然每个PLC供应商将试图保护这一点。”出于这个原因,她说,PLC的制造商将不会开始销售其它厂商的通用I/O。”如果我们开始销售那种产品,那我们还有什么可生产的?”Jannotta说道。随着更多智能I/O出现,SalProvanzano认为在不同的制造商中间这将导致更多的分化。”当I/O变得非常只能,并成为系统的一部分,到底哪个是I/O,哪个是CPU真的很难定义。如果你愿意,CPU也同样能够纳入I/O的系统”。PLC的I/O和个人电脑的连接虽然不同的PLC厂商可能会继续用专有的I/O,但一些厂商使I/O连接到IBMPC这样的兼容设备成为可能。Alle-bradeley和辛辛那提米拉克龙公司已经拥有,并有传言说,GE计划将沿着同样的思路。BillKetelhut,GEFanuc北美的产品规划经理,认为是I/O的普及”我觉得多个主机接口将代替I/O。”她说。朱迪格洛尔,SquareD自动化产业市场经理,将PLC看做是工业电脑。PLC和个人电脑如果IBM7552,行动仪器BC22,和其它计算机出现在工厂,这难道不意味着对PLC的新竞争。”有一些对于更有利于电脑的控制功能。可编程过程控制器被迫适应的这些要求。”RichRyan说。然而,在我们调查的厂商多数不认为”个人电脑入侵”将对她们产生影响。大多数人说,PLC和PC除架构之外,她们一般会做足够的控制。她们认为PC会做PLC的工作紧紧是因为现在PLCI/O模块能跟PC连接。她们相信这只是意味着,PLC和个人电脑将能够共享相同的数据。富瑞恩说:”通用的计算机和可编程控制器内在结构不同,硬件结构有内置到几乎每一个制造商的可编程控制器。如今定制的硬件来运行梯形逻辑,解决机器代码。”她引用的一个根本的区别称呼为”机器状态”富瑞安说:”当你关闭机器,或中断周期,或者跳转到另一个周期,可编程控制器本身记得机器的状态:定时器状态是什么,计数器状态是什么,锁存的状态是什么,但计算机本身不这样做。PLCPLCs(programmablelogicalcontroller)faceevermorecomplexchallengesthesedays.Whereoncetheyquietlyreplacedrelaysandgaveanoccasionalreporttoacorporatemainframe,theyarenowgroupedintocells,givennewjobandnewlanguages,andareforcedtocompeteagainstagrowingarrayofcontrolproducts.Forthisyear'sannualPLCtechnologyupdate,wequeriedPLCmakersonthesetopicsandmore.ProgramminglanguagesHigherlevelPLCprogramminglanguageshavebeenaroundforsometime,butlatelytheirpopularityhasmushrooming."AsRaymondLeveille,vicepresident&generalmanager,SiemensEnergy&Automation.inc;Programmablecontrolsarebeingusedformoreandmoresophisticatedoperations,languagesotherthanladderlogicbecomemorepractical,efficient,andpowerful.Forexample,it'sverydifficulttowriteatrigonometricfunctionusingladderlogic."LanguagesgainingacceptanceincludeBoolean,controlsystemflowcharting,andsuchfunctionchartlanguagesasGraphcetanditsvariation.Andthere'sincreasinginterestinlanguageslikeCandBASIC.PLCsinprocesscontrolThusfar,PLCshavenotbeenusedextensivelyforcontinuousprocesscontrol.Willthiscontinue?"ThefeelingthatI'vegotten,"saysKenJannotta,manger,productplanning,seriesOneandSeriesSixproduct,atGEFanucNorthAmerica,'isthatPLCswillbeusedintheprocessindustrybutnotnecessarilyforprocesscontrol."Severalvendors-obviouslybettingthattheoppositewillhappen-haveintroducedPLCsoptimizedforprocessapplication.RichRyan,manger,commercialmarketing,Allen-bradleyProgrammableControlsDiv.,citesPLCs'sincreasingusesuchindustriesasfood,chemicals,andpetroleum.Ryanfeelstherearetwotypesofapplicationsinwhichthey'reappropriate."one,"hesays,"iswherethesizeoftheprocesscontrolsystemthat'sbeingautomateddoesn'tjustifyDCS[distributedcontrolsystem].Withthestartingpricetagsofchoseproductsbeingrelativelyhigh,aprogrammablecontrollermakessenseforsmall,lowloopcountapplication.Thesecondiswhereyouhavetointegratetheloopcloselywiththesequentiallogical.Batchcontrollersareprimeexample,wherethesequenceandmaintainingtheprocessvariableareintertwinedsocloselythatthebenefitsofhavingaprogrammablecontrollertodothesequentiallogicaloutweighssomeofthedisadvantagesofnothavingadistributedcontrolsystem."BillBarkovitz,presidentofTriconex,predictsthat"allfuturecontrollersthatcomeoutintheprocesscontrolsystembusinesswillembracealotofmorePLCtechnologyandalotmorePLCfunctionalitythantheyeverdidbefore."CommunicationsandMAPCommunicationsarevitaltoanindividualautomationcellandtobeautomatedfactoryasawhole.We'veheardalotaboutMAPinthelastfewyears,andalotofcompanieshavejumpedonthebandwagon.Many,however,weredisappointedwhenafully-definedandcompletedMAPspecificationdidn'tappearimmediately.SaysLarryKomarek:"Rightnow,MAPisstillamovingtargetforthemanufacturers,aspecificationthatisnotfinal.Presently,forexample.peopleareintroducingproductstomeettheMAP2.1standard.Yet2.1-basedproductswillbeobsoletewhenthenewstandardforMAP3.0isintroduced."Becauseofthis,manyPLCvendorsareholdingoffonfullMAPimplementations.Omron,forexample,hasanongoingMAP-compatibilityprogram;butFrankNewburn,vicepresidentofOmron'sIndustrialDivision,reportsthatbecauseofthelackofafirmdefinition,Omron'sPLCsdon'tyettalktoMAP.Sinceit'sunlikelythatanindividualPLCwouldtalktobroadMAPanyway,makersareconcentratingonproprietarynetworks.AccordingtoSalProvanzano,usersfearthatiftheydogetonboardandvendorswithdrawfromMAP,they'llbetheonesleftholdingacommunicationsstructurethat'snotsupported.UniversalI/OWhilethereareconcernsaboutthelackofcompatiblecommunicationsbetweenPLCsfromdifferentvendors,theconnectionattheotherend-theI/O-isevenmorefragmented.Withrareexceptions,I/Oisstillproprietary.YettherearethosewhofeelthatI/Owilleventuallybecomemoreuniversal.GEFanucishopingtodothatwithitsGeniussmartI/Oline.TheindependentI/Omakersarepullinginthesamedirection.ManysaythatI/Oissuchahigh-valueitemthatPLCmakerswillalwayswanttokeepitproprietary.AsKenJannotta,says:"TheI/Oisgoingtobeadisproportionateamountofthehardwaresale.CertainlyeachPLCvendorisgoingtotrytoprotectthat."Forthatreason,hesays,PLCmakerswon'tbeginsellinguniversalI/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,won'tthismeannewcompetitionforPLCs?RichRyan:"Therearesomecontrolfunctionsthatarebetterjobsforcomputers.Programmablecontrollershavebeenforcedtofitintothoseapplications."Yet,themajorityofvendorswesurveyeddon'tlik