自动化专业-外文文献-英文文献-外文翻译-plc方面.pdf

该【自动化专业-外文文献-英文文献-外文翻译-plc方面 】是由【青山代下】上传分享，文档一共【10】页，该文档可以免费在线阅读，需要了解更多关于【自动化专业-外文文献-英文文献-外文翻译-plc方面 】的内容，可以使用淘豆网的站内搜索功能，选择自己适合的文档，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此文档到您的设备，方便您编辑和打印。、外文原文(复印件)Thesingle-puteristheculminationofbothputerandtheintegratedcircuitarguablythetowmostsignificantinventionsofthe20thcentury[1].Thesetowtypesofarchitecturearefoundinsingle—chipputer。Someemploythesplitprogram/datamemoryoftheHarvardarchitecture,-5A—1,othersfollowthephilosophy,eneral—putersandmicroprocessors,ofmakingnologicaldistinctionbetweenprogramanddatamemoryasinthePrincetonarchitecture,showninFig。3-5A-—puterisputerintoasingledevice,asshowninFig3—5A—3。memoryInput&—5A-1AHarvardtypememoryInput&-5A——5A—(RAM).RAMisforthestorageofworkingvariablesanddatausedduringprogramexecution。Thesizeofthismemoryvarieswithdevicetypebutithasthesamecharacteristicwidth(4,8,16bitsetc。)astheprocessor,Specialfunctionregisters,;itisunnecessarytomakedistinctionbetweenRAMandprocessorregisterasisdoneinthecaseofamicroprocessorsystemsinceRAMandregistersarenotusuallyphysicallyseparatedinaputer。)。TheCPUismuchlikethatofanymicroprocessor。putersandmicrocontrollersinvolvethehandlingofbinary—codeddecimal(BCD)data(fornumericaldisplays,forexample),,settingandresettingindividualbitsofmemoryorI/—statedevicessuchasswitches,thermostats,solid-staterelays,valves,motor,。Parallelinputandoutputschemesputer;,forexample,fluorescentdisplays,—chipmemoryandI/,essiveenhancementsetoobigforon-。municationwithterminalmonmeansofprovidingalinkusingasmallnumberoflines。(startandstop)(S)ART(Universal(synchronous)asynchronousreceiver/transmitter)relievingtheprocessor(andtheapplicationsprogrammer)ofthislow—level,time-consuming,detail。tismerelynecessarytoselectedabaud-rateandpossiblyotheroptions(numberofstopbits,parity,etc.)andload(orreadfrom)theserialtransmitter(orreceiver)buffer。Serializationofthedataintheappropriateformatisthenhandledythehardwarecircuit。—。,whichotherwisewoundbenecessaryifcontinuouspreciselytimedinterruptswererequired(asinaclock,forexample)。Sometimesassociatedwithtimerisaneventcounter。Withthisfacilitythereisusuallyaspecialinputpin,。Theclockcircuitryofmostponents。Ifmaximumperformanceisrequired,-costtimingcomponentsorcanbedrivenfromanexternalsource。Thislatterarrangementisusefulisexternalsynchronizationoftheputerisrequired。WORDSANDTERMSculminationn。顶点spiltadj。。保证albeitconj。虽然customadj。-backadj。背负式的socketn。插座B:PLC[1]PLCs(programmablelogicalcontroller)plexchallengesthesedays。Whereoncetheyquietlyreplacedrelaysasionalreporttoacorporatemainframe,theyarenowgroupedintocells,givennewjobandnewlanguages,andarepeteagainstagrowingarrayofcontrolproducts。Forthisyear’sannualPLCtechnologyupdate,wequeriedPLCmakersonthesetopicsandmore。HigherlevelPLCprogramminglanguageshavebeenaroundforsometime,butlatelytheirpopularityhasmushrooming.”AsRaymondLeveille,vicepresident&generalmanager,SiemensEnergy&Automation。inc;Programmablecontrolsarebeingusedformoreandmoresophisticatedoperations,languagesotherthanladderemorepractical,efficient,,it'sverydifficulttowriteatrigonometricfunctionusingladderlogic.”eptanceincludeBoolean,controlsystemflowcharting,andsuchfunctionchartlanguagesasGraphcetanditsvariation。Andthere’sincreasinginterestinlanguageslikeCandBASIC。PLCsinprocesscontrolThusfar,?”ThefeelingthatI'vegotten,”saysKenJannotta,manger,productplanning,seriesOneandSeriesSixproduct,orthAmerica,'isthatPLCswillbeusedintheprocessindustrybutnotnecessarilyforprocesscontrol。Severalvendors-obviouslybettingthattheoppositewillhappen-,mercialmarketing,Allen-bradleyProgrammableControlsDiv.,citesPLCs’sincreasingusesuchindustriesasfood,chemicals,andpetroleum。Ryanfeelstherearetwotypesofapplicationsinwhichthey’reappropriate。one,”hesays,”iswherethesizeoftheprocesscontrolsystemthat'sbeingautomateddoesn'tjustifyDCS[distributedcontrolsystem].Withthestartingpricetagsofchoseproductsbeingrelativelyhigh,aprogrammablecontrollermakessenseforsmall,。Batchcontrollersareprimeexample,wherethesequenceandmaintainingtheprocessvariableareintertwinedsocloselythatthebenefitsofhavingaprogrammablecontrollertodothesequentiallogicaloutweighssomeofthedisadvantagesofnothavingadistributedcontrolsystem。BillBarkovitz,presidentofTriconex,predictsthat”alleoutintheprocesscontrolsystembusinesswillembracealotofmorePLCtechnologyandalotmorePLCfunctionalitythantheyeverdidbefore。”CommunicationsandMAPommunicationsarevitaltoanindividualautomationcellandtobeautomatedfactoryasawhole。We’veheardalotaboutMAPinthelastfewyears,panieshavejumpedonthebandwagon.[2]Many,however,weredisappointedwhenafully-pletedMAPspecificationdidn’:Rightnow,MAPisstillamovingtargetforthemanufacturers,aspecificationthatisnotfinal。Presently,。-basedproductswillbeobsoletewhenthenewstandardforMAP3。0isintroducBecauseofthis,manyPLCvendorsareholdingoffonfullMAPimplementations。Omron,forexample,hasanongoingMAP—compatibilityprogram;[3]butFrankNewburn,vicepresidentofOmron’sIndustrialDivision,reportsthatbecauseofthelackofafirmdefinition,Omron’sPLCsdon’tyettalktoMAP。Sinceit’sunlikelythatanindividualPLCwouldtalktobroadMAPanyway,,usersfearthatiftheydogetonboardandvendorswithdrawfromMAP,they’llbetheonesleftholdingacommunicationsstructurethat'snotsupported。patiblecommunicationsbetweenPLCsfromdifferentvendors,theconnectionattheotherend—theI/O—,I/。GEFanucishopingtodothatwithitsGeniussmartI/。ManysaythatI/Oissuchahigh—,says:”TheI/。”Forthatreason,hesays,PLCmakerswon'tbeginsellinguniversalI/Osystemfromothervendor.”ifwestartsellingthatkindofproduct,saysjannotta,whatdowemanufacture?WithmoreintelligentI/Oappearing,SalProvanzanofeelsthiswillleadtomoredifferentiationamongI/Ofromdifferentmakers。”WheretheI/espartofthesystem,hesays,”itreallyishardtodefinewhichistheI/,ifyouwill,isequallyintegratedintothesystemastheI/O。”ConnectingPLCI/OtoPCsWhiledifferentPLCsprobablywillcontinuetouseproprietaryI/O,severalvendorsmakeitpossibletoconnect5theirI/—bradeley,Could,andCincinnatiMilacronalreadyhave,andrumorhasitthatGEisplanningsomethingalongthesesamelines。[4]BillKetelhut,manageoforthAmerica,seesthissortofthingasalternativetouniversalI/Ithinkthetrend,insteadoftowarduniversalI/O,willbemultiplehostinterface,”,directorofmarking,SquareDAutomationProducts,ViewsitasanotherindicationthatPLCsare,andhavebeenforsometime,,theActionInstrumentsBC22,andothercomputersareappearingonthefactoryfloor,won’tthismeannewcompetitionforPLCs?RichRyan:”Therearesomecontrolfunctionsputers。Programmablecontrollershavebeenforcedtofitintothoseapplicatioet,themajorityofvendorswesurveyeddon’tlikethePCinvasion”willposeaproblemforthem。’tfeelthatPCswilltakejobsfromPLCsjustbecausePLCI/OmodulescannowbeconnectedtoPCs;,”saysRichRyan,”andaprogrammablecontroller。Therearehardwareconstructsbuiltintoalmosteverymanufacture':Whenyoushutthemachineoff,orinterruptthecycle,oryoujumptoanotherspotinthecycle,programmablecontrollersinherentlyrememberthestateofthemachine:whatthetimerswere,whatthecounterswere,whatthestatesofallthelatchesputersdon’tinherentlydothat。”。。厂商tagn。。兼容的2、外文资料翻译译文片机是电脑和集成电路发展的巅峰,,如图3—5A—1,依据同样的原理广泛的适用于一般目的的电脑和微电脑,一些厂家在程序内存和数据内存之间不区分的像Princeton特性,展示如图3-5A—2。只读存贮器(ROM).ROM是通常的永久性的,非应用程序的易失性存储器。不少微机和单片机用于大批量应用,因此,经济的设备制造要求的程序存储器的内容是在制造期间永久性的刻录在芯片中,这意味着严谨的方法,因为修改ROM代码不能制造之后发展。这一发展过程可能涉及仿真,(或拟使用)/O和外部修改这些设备的电路。小内存装置的应用是非常普遍的在永久性内存的制造中[2];但仍然可以在我节省大量成本I/O和其它芯片相比,,可在与’形式变种背驮式’EPROM(可擦除可编程只读存储器)插座或存储器,,,他们提供的单芯片器件的优势,在以下方面的板载I/O等,在灵活的用户可编程带来的便利。随机存取存储器(RAM)。,但具有相同的特征宽度(4,8,16比特等),如栈指针或定时器寄存器,,它是不必要的区分内存和处理器之间的区别在通常不物理上分开的微机中。中央处理单元(CPU).CPU是很象微型电子计算机和微控制器的任何微电脑。许多微电脑和微控制器涉及到二进制编码(十进制处理(BCD)的数据为例)数字显示,因而,常常可以发现该CPU是很适合处理这种类型的数据。对设施良好与否进行的测试,设置和重置单个位的内存或I/O控制器的应用程序,,如开关,恒温器,固态继电器,阀门,电机等并行输入/,在不同的微机,在大多数设立一个机制,至少选择让其中一些引脚输出,一些引脚输如是非常灵活的。这可能适用于所有或端口。有些I/O线直接连接到适当的设备,例如,荧光显示器,也可以提供足够的电流,,其他组件将作为系统总线配置为允许片外存储器和I/O扩展。这个设施是潜在有用的一个产品系列的发展,因为连续增强可能成为太上存储器,这是不可取的,不是建立在现有的软件基础上的。串行输入/输出。(启动和停止)的信息。这可以作为一个硬件设施或U(拧)艺术(通用执行(同步)异步接收器/发送器)减轻处理器(和应用程序)的这种低层次的确费时。它也只需要选择一个波特率及其他可能的选择(停止位,奇偶校验等)和负载号码(或读取),串行发送器(或接收)的缓冲器。进行适当的格式的数据串行处理,然后由硬件电路完成。定时/计数器设施。许多应用的单片机需要对过去的真实时间准确的评价。这可以由每个程序中的执行时间分支认真评估,但除最简单的程序外,,能独立计算精确的时间增量,。计时器然后减少此值产生中断或设置标记时,。这将缓解重新加载计数器和评估所用的时间,。这个设备通常有一个特殊的输入引脚,可直接驱动计数器。定时元件。,必须使用晶体以确保最大时钟频率接近,但不会超出。许多时钟电路,还具有电阻和低电容工作成本定时元件,也可以从