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电子与信息工程学院本科毕业论文设计外文文献翻译译文题目Program__blelogiccontrollersHardwaresoftwarearchitecture学生姓名吴凡专业电气工程及其自动化指导教师李东京2012年12月Program__blelogiccontrollers:Hardwaresoftwarearchitecture__nyrespectsthearchitectureoftheprogram__blelogiccontrollerPLCresemblesageneral-purposecomputerwithspecializedinput/outputI/Omodules.HoweversomeimportantcharacteristicsdistinguishaPLCfromageneral-purposecomputer.MostimportantaPLCismuchmorereliabledesignedforameantimebetweenfailuresmeasuredinyears.SecondaPLCcanbepla__dinanindustrialenviro__entwithitssubstantialamountofelectricalnoisevibrationextremetemperaturesandhumidity.ThirdPLCsareeasily__intainedbyplanttechnicians.BasicPLChardwarearchitectureThebasicarchitectureofaPLCconsistsof__incomponents-thepro__ssormodulethepowersupplyandtheI/Omodules.Thepro__ssormoduleconsistsofthe__ntralpro__ssingunitCPUandmemory.Inadditiontoamicropro__ssortheCPUalsocontainsatleastaninte_____toaprogrammingdevi__and__ycontaininte_____storemoteI/Oandothercommunicationnetworks.ThepowersupplyisusuallyaseparatemoduleandtheI/Omodulesareseparatefromthepro__ssor.ThetypesofI/Omodulesincludediscreteon/off____ogcontinuousvariableandspecialmoduleslikemotioncontrolorhigh-speedcounters.Thefielddevi__sareconnectedtotheI/Omodules.DependingontheamountofI/OandtheparticularPLCpro__ssortheI/Omodules__ybeinthesamechassisasthepro__ssorand/orinoneormoreotherchassis.Upuntilthelate1980stheI/OmodulesinatypicalPLCsystemwereinchassisseparatefromthePLCpro__ssor.Inthemoretypicalpresent-dayPLCsomeoftheI/Omodulesarepresentinthechassisthatcontainsthepro__ssor.SomePLCsystemsallowmorethanonepro__ssorinthesamechassis.__allerPLCsareoftenmountedonaDINrail.The__allestPLCsoftencalledmicro-PLCsornaon-PLCsincludethepowersupplypro__ssorandalloftheI/Osinonepack-age.Somemicro-PLCscontainabuilt-inoperatorinte_____panel.For__nymicro-PLCstheamountofI/Oislimitedandnotexpandable.BasicsoftwarememoryarchitectureIEC61131-3TheIEC61131-3standarddefinesamemoryandprogrammodelthatfollowsmodernsoftwareengineeringcon__pts.Thismodelincorporatessuchfeaturesastop-downdesignstructuredprogramminghierarchicalorganizationfor__lsoftwareinte_____sandprogramencapsulation.Fortunatelyextensivetraininginsoftwareengineeringtechniquesisnotne__ssarytobecomeaproficientprogrammer.Iffullyimplementedthemodelisreasonablycomplicated.The__indisadvantagesofthemodelareitscomplexityanditscontrasttothesimplicityoftheearlyPLCs.TheoverallIEC61131-3memorypro-gramandmemorymodelaredescribed.Forvariousimplementationsofthestandardvisit___.isa.org/link/Erickson_PLC.TheIEC61131-3memorymodelwhatthestandardcallsthesoftwaremodelislayered-eachlayerhides__nyofthefeaturesofthelayersbeneath.Eachofthe__inelementsisnowdescribed.TheconfigurationistheentirebodyofsoftwareprogramanddatathatcorrespondstoaPLCsystem.GenerallyaconfigurationequateswiththeprogramanddataforonePLC.InlargecomplexsystemsthatrequiremultiplecooperatingPLCseachPLChasaseparateconfiguration.AconfigurationcommunicateswithotherIECconfigurationswithinthecontrolsystemthroughdefinedinter-fa__scalledac__sspaths.Thechoi__ofthetermconfigurationconflictwiththehistoricuseofthisterminthecontrolsindustry.Generallyconfigurationreferstothepro__ssofspecifyingitemssuchasthePLCpro__ssormodelcommunicationinte_____sremoteI/Oconnectionsmemoryallocationandsoon.ThereforethevendorsproducingIEC-compliantPLCsthatusethetermconfigurationinthehistoricsenserefertotheentirebodyofsoftwarewithsomeothertermsuchasprojects.Aresour__providesthesupportfunctionsfortheexecutionofprograms.Oneormoreresour__sconstituteaconfiguration.Nor__llyaresour__existswithinaPLCbutit__yexistwithinapersonalcomputertosupportprogramtesting.Oneofthe__infunctionsofaresour__istoprovideaninte_____betweenaprogramandthephysicalI/OofthePLC.Aprogramgenerallyconsistsofaninterconnectionoffunctionblockseachofwhich__ybewritteninanyoftheIEClanguages.Afunctionblockorprogramisalsocalledaprogramorganizationunit.Inadditiontothefunctionblockstheprogramcontainsdeclarationsofphysicalinputs/outputsandanyvariableslocaltotheprogram.AprogramcanreadandwritetoI/Ochannelsglobalvariablesandcommunicatewithotherprograms.Providethemeanstotransferinfor__tionbetweenconfigurations.Taskscontroltheexecutionoftheprogramorpartsofaprogram.Ataskcontrolsoneormoreprogramsand/orfunctionblockstoexecute.Theexecutionofaprogramimpliesthatallofthefunctionblocksintheprogramarepro__ssedon__.Theexecutionofafunctionblockimpliesthatallofthesoftwareelementsofthefunctionblockarepro__ssedon__.Therearenoimpliedmechani__sforprogramexecution.Inorderforaprogramtobeexecuteditmustbeas-signedtoataskandthetaskmustbeconfiguredtoexecutecontinuouslyperiodicallyorwithatrigger.Variablesaredeclaredwithinthedifferentsoftwareelementsofthemodel.Alocalvariableisdefinedatthesoftwareelementandcanonlybeac__ssedbythesoftwareelement.Localvariablescanbedefinedforthefunctionblockprogramresour__orconfiguration.Aglobalvariabledefinedforaconfigurationresour__orprogramisac__ssibletoallelementscontainedinit.Forexampleaglobalconfigurationvariableisac__ssibletoallsoftwareelementsintheconfiguration.Aglobalprogramvariableisac__ssibletoallfunctionblocksintheprogram.DirectlyrepresentedvariablesarememoryandI/OlocationsinthePLC.IEC61131-3definesfor__tsforreferen__stosuchdata.However__nyimplementersofthestandardusetheirownfor__tswhicharenotconsistentwiththeIECstandard.外文翻译在很多方面,可编程控制器的结构就像一台拥有特殊输入、输出模块的通用型电脑然而普通电脑相比有以下几个显著特点最重要的是,PLC更可靠平均故障率很低第二个方面,PLC可以在恶劣的条件下工作,如大量的电噪声,震动,极限的温度,湿度第三个方面,PLC在工厂设施中更容易稳定PLC的基本硬件结构PLC的基本结构有以下几个主要模块——处理器模块,电源模块和输入输出模块处理器模块由__处理器单元和存储器组成除此之外微处理器即CPU也至少包含编程接口,有的甚至含有I/O扩展口和其他通讯网络电源部分通常是__的,而I/O模块则与处理器分离,I/O模块的形式有数字量和模拟量,特殊的模块有运动控制模块和高速计数器工业设备就与I/O模块相连根据I/O口的数量和PLC处理器的特点,I/O模块可能与PLC在同一个底架或多个底架中直到19世纪80年代后期,I/O模块和处理器分离在一个典型的PLC系统中在如今典型的PLC中,有些I/O模块也在包含处理器的底架中出现有些PLC系统允许不止一个的处理器在一个底架中小型PLC通常固定在导轨上最小的PLC包含电源,处理器,和所有I/O口在一个包装盒中有些微型PLC还包含内嵌处理器接口对于很多微型PLC来说,I/O口的数目是有限的和不可扩展的基本软件,存储器构造IEC61131-3标准定义了存储器单元和程序单元所遵循的现代软件工程概念该模型包括自上而下的设计,结构化程序设计,分层__,标准软件接口程序简述等特点幸运的是,想成为一名熟练的程序员,广泛的软件工程培训并不是必须的如果完全应用,那该模型将会相当的复杂该模型的与早期的PLC相比最主要的缺点是相对要复杂些关于存储器模型已全部介绍完IEC61131-3存储器模型是每个层所隐藏的功能的最下面到此关于PLC内部的结构已经介绍完全一个完整的程序通常由内部__的功能块组成,它们可以以任意一种IEC语言写成一个功能块程序也称为程序__单元除了功能块之外,程序也包括声明语言一个程序可以通过I/O通道与其他程序通信提供通道与各结构进行交流任务控制程序或某部分程序的执行一个任务控制一个或多个功能图执行每个功能图只执行一次一个程序要想执行,必须被任务标明,而且任务必须连续执行,或有条件触发变量在不同的软件模型中声明一个在软件元素定义的局部变量只能在软件元素中使用局部变量可以在功能图,程序,结构中定义一个全局变量可以被所有包含在内的元素访问例如,一个全局__变量可以被所有在结构中的软件元素访问一个全局程序变量可以被所有在程序__能图访问存储器和I/O口位置是直接变量IEC61131-3定义了此类数据然而许多厂家使用的是它们自己的标准,这是不符合的国际电工委员会标准的。