外文翻译-基于CAN总线在设计网络中使用远程IO模块

英文原文DESIGNOFPLCNETWORKSUSINGREMOTEI/OMODULEBASEDONCONTROLLERAREANETWORKP.Roengruen,T.Suesut,J!Tipsuwanporn,V.KongratanaandS.KulphanichFacultyofEngineering,KingMongkutsInstituteofTechnologyLadkrabang,BangkokThailandTel(662)-326-7346-7ext102E-mail:ktvittaykmitl.ac.thABSTRACTInthispaper,thedesignofthenetworkssystemthroughCANbusispresented.Todistributethecontrolpointswithalongdistanceanddifferentlocatedfortheapplicationtoon-offelectricalequipmentbytheremoteI/Omodule.ThecontrollingandcommunicationbetweenthePLCandtheremote110modulesareusedbytheCANbusserialcommunication.Inthispaper,theexperimenthasbeensetupthemaximumof32remoteI/Omodules.EachremoteI/OsarelinkedtohostPLCprogrammedforhandlingainterruptrequestfromanyremote110independently.Therefore,thescanningtimeofthecontrollernoteffects.Byusingthistechnique,thecontroller(PLC)canbeefficientlyappliedtotheseveralhundredmeters1.INTRODUCTIONAprogrammablelogiccontrolleriswidelyusedintheindustrialcontrolsystem.Thedevelopmentisproposedtoexpandthecontrolpoints,developtheinstructionsetforeasierprogrammingtomoreintelligence,theinterfacingwiththeothersystem,thecontrollingwithlongdistance.ControllerAreaNetwork(CAN)isawell-knownbustechnologyinindustrialcommunicationsystem.TwoversionsofCANdifferinginthesizeoftheidentifierexistthatconsistofCAN2.0Awithan11-bitidentifierandCAN2.0Bwitha29bitidentifier.ThispaperfocusesofCAN2.0AprovidingasufficientnumberofidentifiersfordesignPLCwithlowcostnetwork.ThecommunicationmediausedatwistedpairwiththeseveralhundredmetersforeachremoteI/Omodules.EachofremoteI/Omodulesconsistsof16-bitdigitalinputand16-bitdigitaloutput,andthemaximumof32remoteI/OmodulescanbelinkedtohostPLCmeanthatthemaximumcontrolpointsareof512points.Theautomaticcontrolsystemsinindustrieshavemanykindsoffielddevice(e.g.sensor,actuators),andmanykindsofprocesscontrol.Thefieldbusconceptneededtocombinethesignalsfrommanykindsoftheprocesscontrolequipmenttobethesamesignalbydigitalcommunication.Thetraditionalcommunicationstandardsknowas4-20mAdc(e.g.transmitter,I/Ptransmitter).Thisstandardprovidesforpoint-to-pointconnection,whichconsistsofallinformationexchangedbetweenfieldandcontroldevicesinbothdirections.Thegreatnumberoffielddevicesbeingusedrequiresalotofcables.Thisistheproblemininstallationandmaintenanceandthedocumentationworkaswell.Thefieldbusconceptisbasicallyadigitalcommunication,whichiscapableofinterconnectionfielddeviceswithcontrolsysteminanyprocesscontrolenvironment.Thefieldbuscommunicationarchitectureinthetermofnodewillbeusedtorefertoafielddevice.Thefieldbusdeviceshavewidevarietiesoffielddevices.Therearesimpledevicessuchasthelimitswitches,relays,single-contactdeviceanddumbactuators,smartsensor,thecomplexdevicessuchastheprogrammablecontrollers,PIDandloopcontrollers,etc.Thefieldbussupervisoristhecentralcontrollerthattakesthetotalresponsibilityforinitializingthebus,establishingwhatdevicesareattachedtoitandmonitoringitsactivities.Inthepast,incompatiblevendor-specificfieldbuswerefrequentlyused.Manyfieldbussystemstodayareopenstandardsystem.Theuserisnolongertiedtoindividualvendorsandisabletoselectthebestandmosteconomicalproductfromawidevarietyofproducts.Today,allleadingmanufacturersofautomationtechnologyofferfieldbusinterfacesfortheirdevices.Thatiswhythefieldbussystemspresentverydynamicallygrowingbranchofscienceanddevelopmentdirectlyappliedinindustry.Thesetechnologiesaredevelopedandadministratedbyuserorganizations(CANinAutomation,OpenDeviceNetVendorAssociation8,FieldbusFoundation1,3,ProfibusInternational2,5etc.).ThepopularityofCANisduetoitseaseofuse,toitsextremelyhighefficiencyandreliabilityandtothelowcostsofCANimplementations.Therefore,inthispaperfocusesontheControllerAreaNetworktodesignthePLCnetwork.2.CONTROLLERAREANETWORKElectronicunitsbegantoequipvehiclesinearly80s.Gradually,theyincreasedtheneedforreal-timecommunicationswithinavehicle.However,addingmorededicatedsignallinessoonbecameimpossiblebecauseofcost,reliabilityandrepairproblems.(Thetotallengthofcablesinsomehigh-endEuropeancarsreleasedinthelate80swasestimatedtobeover2km!)Tofulfillthissharpneedformultiplexedcommunication,the“RobertBoschGmbH”companydesignedtheCANnetwork.Althoughspecificallyconceivedfortheautomotiveindustry,itiswidelyusedinautomationmainlyduetothelowpriceofCANcommunicationsolutions.Fig.1FormatofaCANtelegramCANisabroadcastbus,withpriority-baseaccesstothemediumandnon-destructivecollisionresolution:whentwoormorenodestrysimultaneouslytotransmitamessage,thelowestpriorityframeslosethecontention.But,thehighestprioritymessagesuccessfullydestinationwithoutbeingdestroyedbythecollision.Nodesdonotpossessanaddress,andnoneofthemplayapreponderantroleintheprotocol.Amessagecontainsandidentifier,uniquetothewholesystem,thatservestwopurposes:assigningapriorityforthetransmission(thelowerthenumericalvalue,thegreaterthepriority)and2allowingmessagefilteringuponreception.Data,possiblysegmentedinseveralframes,maybetransmittedperiodically,sporadicallyoron-demand.Aminimal,CANcommunicationprofilehasathree-layeredarchitecture:aphysicallayer,aData-LinkLayer(DLL)andanapplicationlayer.TheDLLisimplantedinanelectroniccomponentcalledaCAN-Controller.TheIS0standards11519-2and11898ondefinethephysicallayerandtheDLL.However,standardproposalshavebeenmadefortheapplicationlayer(CANApplicationLayer,orCAL)orforcompleteprofilesbasedonthetwonormalizedlayers(SmartDistributedSystems,ofSDS,DeviceNet)Duetothemediumaccesstechnique(Priority-basedCarrierSenseMultipleAccess/CollisionDetection),themaximumdataratethatcanbeachievedessentiallydependsonthebuslength.Forexample,themaximumdataratefor30and500meterbusesarerespectively1Mbit/secand100kbit/sec6.TheCANmessageformatthatuses11-bitidentifiers(2.0Aformat);however,anextendedCANformat(2.0Bformat)alsoexitsthatuses29-bitidentifiersinstead.CANcontrollerssupportingtheextendedformatwillingeneralalsoworkwiththestandardformatcommunicationusing11-bitidentifiersalthoughthereverseisnotalwaystrue.SomedevicessupportingpurelythestandardformatwillbeabletotolerateotherdevicestransmittingCANframesusingtheextendedformat(2.0Bpassivedevices)andfunctioncorrectly.Amessageinthestandardformatbeginswiththestartbitorstartofframe(SOF).ThisisfollowedbythearbitrationfieldwhichcontainstheidentifieroftheCANtelegramandisusedtoarbitrateaccesstothebus.AlsopartofthearbitrationfieldistheRTRbit(remotetransmissionrequest)whichindicateswhethertheframeisarequestframe(withoutanydata,thistypeofmessageisusedtotriggeratransmissionbyanothernode)oradataframe.ThecontrolfieldcontainstheIDEbit(identifierextension),whichindicateswhethertheframeisastandardformatframeoranextendedone,ther0bitthatisreservedforfutureextensionsandfouradditionalbitscontainingthelengthofthedatafield(datalengthcode).NextcomesthedatafieldwhichcanbefromzerotoeightbytesinlengthandtheCRCfieldthatcontainsa15-bitcodethatisusedtocheckframeintegrity.Theacknowledge(ACK)fieldcomprisesanACKslotbitandanACKdelimiterbit.TheACKslotistransmittedasarecessivebit(abitwithavalueof1)andreceiversthatretrievethemessagecorrectly(regardlessofwhetherthemessageismeantforthecontrollerornot)overwritethisfieldwithadominantbit(abitwithavalueof0).Thedetectionofthisdominantbitbythetransmittermeansthatthemessagewasacceptedbyatleastonenodeandwasthereforeerror-free.Theendofframefield(EOF)denotesthattheframeterminated.Finally,theintermission(Int)spacerepresentstheminimumnumberofbitperiodsthatneedtoelapsefollowingtheframebeforeanotherstationisallowedtotransmitamessage.Ifnoothertransmissionsfollowtheframethebusremainsinitsbusidlestate.3.NETWORKSYSTEMCONFIGURATIONSThesystemconsistsofthePLCtobeusedasthefieldbussupervisorandtheremoteI/Omoduleasthefieldbusdevice.ThefieldbusdeviceandfieldbussupervisorareconnectedthroughthetwistedpairinformofbustopologybyCANbus.EachremoteI/OmodulehastheunitnumberinordertosettheidentifieronCANprotocol.Theunitnumbercanbesetfromthedipswitches,whichrunfromunit00tounit31thelowestvalueofunitnumberisthehighestprioritysothatusercanselectthepriorityofanydevice.Fig,3showstheconnectingbetweenthePLCandtheremoteI/Omodule.Fig.3.TheconnectingbetweenthePLCandtheremoteI/Omodules4.HARDWAREDESIGNInFig4,showsthePLCthatusedmicroprocessorpartNo.84C117asthecentralProcessingUnit(HostCPU).ThePLCconsistsofopto-isolated24inputsand12output,thesequentialoperationcontrolprogramandthespecialfunction,suchasshiftregister,canbewrittendowntoPLCthroughbuildinkeyboard.ThePLChastheCANcontrollerpartNo.DS80C390(DALLASsemiconductor)9andCANtransceiverchipspartNo.82C251(Philipssemiconductor)inordertocommunicatewiththeremoteI/Omodules.TheprogramminglanguagebeingusedistheLadderDiagraminstruction.Themonitoringfunction,whichusedtoobservethestatusofthePLCoperation,isalsoincluded.TheremoteI/OmoduleusedthesimilarCANcontrollerandCANtransceiver.Theinputoutputportisprotectedfromtheoutsideelectricalsignalbytheopto-isolatorFig.4.Theprogrammablelogiccontroller(PLC).Fig.4Theprogrammablelogiccontroller(PLC)Fig.5ThestructureofPLCandremoteI/Omodules5.OPERATIONOFTHEINSTRUCTIONSTheinstructionusedtheladderdiagramprogramminginordertosendorreceivetheinformationwiththeremoteI/Omodule.TheladderdiagramprogrammingisnamedasRDIistheinstructiontoreaddatafromremoteI/OandWROistheinstructiontowritedatatoremoteI/O.Thisladderinstructioniscontrolledbytheinterruptrequestcontrolrelay.Iftheconditionoftheinterruptrequestcontrolrelayislogical1thenthecontrollerwillcreateandsendblockcommandtoreadorwritedatadependontheprogramrequested.ThereforethecontrollernotnecessarytocommunicatewiththeunconcernedremoteI/Omodule.Inthiscase,thescantimeofthecontrollerisnoteffected.Moreover,addingorremovingoftheremoteI/Omodulecanbedoneindependently.RDIinstruction(FUN70)Fig.6.TheRDIladderinstructionInFig.6,theRDIinstructionisthefunctionnumber70intheladderinstructionofthisPLC.WROinstruction(FUN71)Fig.7.TheWROladderinstructionInFig.7,theWROinstructionisthefunctionnumber71intheladderinstructionofthisPLC.BothinstructionshavetodeterminetheunitnumberoftheremoteI/Omodule,whichrequestedinformation.TheWDisthewordmemoryinthecontrollerashexadecimalcodefor16-bitbinarysystem.ThedatafromtheremoteI/Oshouldhavetemporarystorageareainthewordmemory,whichisdetermined.Therefore,theremoteI/OmemoryisconsideredasthePLCmemory.TherearemanykindsofwordmemoriesinthePLCsuchasInternalRelay(IR),HoldingRelay(HR),andDataMemory(DM),respectively.Fig.8.TheapplicationexampleFig.9.Theladderprogram6.IMPLEMENTATIONInFig.8,ThesystemcanbeappliedtothemultigroupsON-OFFcontrolwithlongdistance(maximumdistance48metersat1Mbpsdatatransmissionrate).Inthisexperimentthe100kbpsdatatransmissionratewith200metersdistanceisused.ThecasestudymodelconsistsofthemainconveyerandsubsconveyerA,B,C,respectively.Theproductsaremovedbythemainconveyerandaredetectedbysensor1,sensor2andsensor3.Iftheproductisidentifiedforarrangingtosub-conveyerA,thecylinder1willmoveouttoturntheproducttothesub-conveyerA.Sotheinterruptcontrolrelaywhichcontroltheoperationofremoteinputnumber00andremoteoutputnumber01willoperatebytheconditionoftimerfor20seconds.Therefore,thecontrollerdosenotnecessarytoupdatedataoftheotherremoteinput/outputmoduleeveryscan-time.TheladderprogrammingthatshowinFig.9.7.CONCLUSIONSThepapershowsthetechniquetodesignthePLCsysteminordertoexpandtheinputandoutputwiththeremoteI/OmodulebasedonCANbus.ThisPLCsystemcanbeusedtocontrolmanydeviceswithlongdistanceassameasthefieldbustechnique.TheinstructionbeingdesignedinthisPLCisveryelasticsandsuitablefortheladderdiagramprogramming.ThePLCcanbeefficientlyappliedtotheON-OFFcontrol.中文翻译基于CAN总线在设计网络中使用远程IO模块摘要在本文中，通过总线介绍了网络系统设计。分布控制点与长距离和不同的应用程序位于电气设备的远程IO模块上下。110个远程IO模块和控制之间的沟通是使用的总线串行通信。在本文的实验中，建立32个最高的远程IO模块，每个远程操作系统与主机编程处理请求都是从110个远程IO模块中独立发出的。因此，扫描时间控制器不影响。通过使用这种技术，该控制器（LC）可以有效地应用到几百米。1.简介可编程控制器已广泛应用于工业控制系统，受关注的发展方面有：扩展控制点数，指令系统能较容易设计更智能的程序，通过其接口可以连接其他系统以实现远距离控制。CAN总线是一种在工业通信中广泛应用的总线技术。依据标识符的大小，CAN总线可分为两种版本，即11位标识符的CAN2.0A和29位标识符的CAN2.0B。本文采用的CAN2.0A对于设计低成本的PLC网络是完全符合标识符要求的。各远程I/O模块之间的传输介质采用几百米长的双绞线，每个远程I/O模块由16位数字输入和16位数字输出组成，主PLC最多有512个控制点，可以有32个远程I/O模块连接到主PLC上。工业中的自动控制系统有许多种类的设备（比如传感器）和过程控制，其间总线传输采用数字通信将各种过程控制设备联系起来。传统的通讯标准以4-20mAdc（例如发射机，I/P发射机）著称。此标准规定以点对点通信，由各区域和控制设备之间相互转换的所有信息组成。大量的现场设备需要很多电缆，在安装和维护的过程中这是个问题，文档处理也很麻烦。现场总线主要是一个数字通信系统，此系统能够在任何控制环境中互联各个现场设备。现场总线通信体系结构常以节点表示现场设备，现场设备种类广泛，较简单的设备有限位开关、继电器、一次接触器、灵敏传感器等，复杂的设备有可编程控制器、PID和循环控制器等。现场总线由中央控制器来控制并负责初始化，以及建立总线下的现场设备并监视它的动态。过去，现场总线的厂商之间存在很多矛盾。如今现场总线系统都是标准开放系统，用户不再依赖某一特定厂商，而是能够从种类繁多的产品当中选择最佳最经济的产品。今天，.所有的自动控制技术厂商都为其设备生产现场总线接口。现场总线系统是科技领域中一个直接在工业中应用的强劲的分支。这些技术依靠用户来发展和支配。（自动控制CAN，开放式设备网络厂商联合会8,现场总线基础1,3等）CAN总线得以普及，是因为它简单易用，有非常高的效率和可靠性且执行成本低。因此，本论文的重点是利用CAN总线来设计PLC网络。2.控制器区域网络早在八十年代初期的时候，电子就开始利用媒介传输。以后，他们就更加需要以媒介来建立实时通信。但因为成本，可靠性和维修问题，不可能增加太多的传输信号线。（到八十年代末期，在一些高端技术的欧洲车上，估计传输电缆的总长将超过2公里！）为了满足多路通讯的强烈需求，“罗伯特博世”股份有限公司设计了CAN网络。虽然最初的的构想为汽车行业服务，但由于CAN通信解决方案价格的低廉性，如今已被广泛的用于自动控制中。图1CAN总线报文的格式CAN总线是一个广播总线，是具有优先权的优先使用的媒介。非破坏性碰撞协议为：当两个或两个以上的节点同时传送一个讯息，具有低优先级的信息失去了争夺。但具有最高优先级的信息能够成功的传输而不被碰撞所破坏。节点不能占有一个地址，它们在协议中不具有优先权。在整个系统中，一个信息包含唯一的一个标识符，即有两个目的：为传输指定一个优先级（数值越低，优先级越高）和接收信息经过2个允许讯息筛选后，可能分割为若干个框架，也可能被定时性的传输，或者被要求进行断断续续的传输。对一个最低限度的CAN来说具有三层体系结构：物理层，数据链路层（DLL）和应用层。数据链路层被植入在一个电子器件中，称为CAN控制器。ISO标准的11519-2和11898定义了物理层和数据链路层。然而，对于应用层来说，最适宜的标准提议或是完整结构是基于这两个层次的规格化（即智能分布式系统）由于媒体传输技术（具有优先级的多路复用/碰撞检测）从本质上依靠数据总线的长度，数据速率可以达到最大值。举例来说，对于30米和500米的总线，数据速率最高可分别为1Mbit/s和100Kbit/s6。CAN的信息格式使用11位标识符（2.0格式）;不过，也可以延长1个格式（2.0B格式），用29位标识符替代。CAN的控制器支持扩展格式，在通常情况下，传输信息用11位标识符的标准格式，但也并非总是如此。对于完全支持标准格式的设备来说，也可能容忍其他装置用扩展格式（2.0b无源器件）传输CAN的帧。在标准格式里，一个信息以起始位或启动帧开始的。紧跟着是中断字段，它包含了CAN电报的标识符，并对是否有权使用总线做出公断。同时RTR位（远程传输的请求）被中断字段所占有，用来表示帧是否帧是一个请求帧（无任何数据，这种类型的信息是由另一个节点触发传输）或一个数据帧。控制字段包含IDE位（标识符扩展部分），用来表明帧是否是一个标准格式的帧或扩展的帧，r0位留做作为将来扩展之用，并增设四位作为数据字段的长度（数据长度代码）。接下来的0到8个字节的数据字段由CRC帧所占有，它包含了一个15位的原代码，用来检查帧的完整性。接受帧（ACK数据）包括一个ACK插槽位和一个ACK定界符位。