在自動化過程中的可編程序邏輯控制器

畢業(yè)設(shè)計外文資料翻譯題目在自動化過程中的可編程序邏輯控制器學(xué) 院 機(jī)電與車輛工程學(xué)院 專 業(yè) 機(jī)械設(shè)計制造及其自動化 班級 學(xué)生 學(xué)號 指導(dǎo)教師 二0一四年三月一日4thInternationalDAAAMConference"INDUSTRIALENGINEERING-INNOVATIONASCOMPETITIVEEDGEFORSME"29-30thApril2004,Tallinn,EstoniaPROGRAMMABLELOGICCONTROLLERSINPROCESSAUTOMATIONAhtiMikkor,LembitRoosimolderDepartmentofProductDevelopment,InstituteofMachinery,

TallinnTechnicalUniversity,Ehitajatetee5,19086Tallinn,Estonia

ahti.mikkor@Abstract:Nowadays,controlproblemsaresolvedusingoperatingcomponentsfromawidevarietyoftechnologies:electronics,hydraulics,pneumaticsandmechanics.Functio-nality,reliabilityandpriceofthecontrolledsystemaredeter-minedbythequalityofthesolutionmade.Thepaperconcentratesonpracticaluseofprogrammablelogiccontrollers(PLC)thatisbasedonthefiveyearsprojectdevelopmentexperienceinthisarea.Successfulsolutionsandproblemsareunderfocus.Specifichardware,controllerprogrammingproblems,data/signalsexchangeandhumanmachineinterfacesareconsidered.Asaresultthemethodforselectingprogrammablecontrollersaccordingtospecificneedsisdeveloped.Practicalsuggestions,possiblehazardsandwarningsareproposedthatcouldhelptoavoidmistakes.Keywords:programmablecontrollers,PLC,automation,automationsystems,processautomation.INTRODUCTIONModernmachineryconsistsofbothmechanicalandelectronicparts.Overallfunctionalityisdeterminedby"balance"betweenthesecomponents.Initialplanningandsolutionselectionplayscriticalroleinfinalresult.Incontrolmethodstheselectionhastobemadebetweenrelay-basedcircuits,specialdevices,programmablelogiccontrollers(PLC)andnewdevelopmentelectronics.ThisarticleisconcentratedonPLC-sandexperiencethathascollectedover5-yearpracticalworkwithPLC-s.Strongandweaksides,positiveandnegativepracticesarediscussed.Suggestionsweathertouseprogrammablecontrollersornothavebeenformedtohelpdecisionmaking.ThemostimportantdecisioninplanningPLC-basedsystemisselectingprocessortype.Mistakesmeanextracostsformodificationsorevenneedforcompletelynewdevices.Themostcommonerrorisoverestimatingprogrammingpossibilitiesofsmall-sizedprocessors.ThereareseveralmethodsforselectingPLC.UnfortunatelymostofthemfocusonelectricalsideofPLC-sandmaximumcountofsignalsallowed.Theydon’tinvolveanalysistodeterminepossiblespecialneedsforuserprogramorcommunications.Basedonseveralexistingmethods,practicalexperienceandfuturetrendsanewmethodforselectingPLCwasdeveloped.AhtiMikkorhasgainedhisexperiencebytakingpartinmorethan15big-scaleautomationprojects.TheseprojectsincludedevelopmentofpowerconsumptionmonitoringsysteminASKundaNordicCementfactory,renewingtestingrigforflowmeters,buildingAhtmepowerplantturbinesafetysystems,watertreatmentplantsintownsRakvereandPolva,wastewatertreatmentplantintownJogevaanddevelopmentofmonitoringsystemforcentralheatingnetworkinTartu.PROSANDCONSINUSINGPROGRAMMABLELOGICCONTROLLERSPositiveargumentsThemainadvantagethatprogrammablecontrollersprovideisflexibility(Jack,2003).Behaviourofthesystemcanbeeasilychangedviaprogramwithoutanyotheralterations.Specialdevicesforexamplemakeanychangesincontrolalgorithmveryhardtoimplement.FlexibilitymakesPLC-swellsuitableforfrequentlychangedapplications,forexampleinrobotics.InPLC-stherelationsbetweeninputsandoutputsaredeterminedbyuserprogram.Byusingadvancedprogrammingtechnologiesitismucheasiertoimplementcomplexcontrolalgorithmsthaninanyhard-wiredsolutions.ItmakesPLC-sverycompetitiveforcomplextasks,forexampleincontrollingchemicalprocesses.SpecialmodulesallowvastamountofdifferentsignalstobeconnectedtothePLCsystem.UseofPLC-sshouldbeconsideredinapplicationsthatrequiresome“specialinputoroutputsignals.Typicalexamplewouldbepositioningusingreferencedatafromhigh-speedinput.TypicallyPCvisualizationsoftwarepackagesaremadeforPLC-s.SomespecialdeviceshavealsoPCsoftwarepackages.WiderangeofcommunicationoptionsbetweenPLC-smakesitpossibletogatherallinformationfromfielddevicesintoonecentralcontrolpoint.CommunicationlinesbetweenPLC-sallowusinginformationcollectedfromotherpartsofthesysteminlocalprocesscontrol.Moderncommunicationtechnologiesenableremotediagnosticsandconfiguration(Jack,2003).Thesetwosignificantlyreduceoverallmaintenancecostsofthesystem.NegativeargumentsProgrammablecontrollersarenotequippedwithenoughmemorytostorebigamountsofdata.AlthoughfuturetrendsshowgrowthinPLCmemorysizes,specialdevices(recorders)arestillbettersuitedforstandalonedataloggingapplications.FornetworkedsolutionsthereispossibilitytousevisualizationsoftwarepackagestogetherwithPLC-stoarchivecollecteddatainanydatabaseformatnecessary.If~-2-loggeddataamountsaresmallortherearealsocontrolfunctionsincluded,it’sreasonabletostillusePLC-s.Aboutvisualizationsoftwarepackagesit’sgoodtoknowthatinstandardversionsmostofthemdonotsupportofflinerecordingsothataftercommunicationbreakdownitisnotpossibletoacquiredatabackwardsfromPLC.ModerncommunicationoptionsforPLC-sincludestandardprotocolsforexampleEthernet.Itistemptingtouseexistingofficenetworksalsoasdatacarrierforautomationsystemcommunications.Timehasshownthatitisbetterpracticetokeepthesetwoseparatedifthereisaneedforconstantonlinecommunication.Hardlytraceabletemporalnetworkoverloadscancauseproblemsalsoinautomationsystemcommunications.AllPLC-sneedbeprogrammed.Allprogrammingworksincluderiskforaccidentalerrorsincontrolalgorithm.Specialdevicesarewelltestedandgenerallyfreeofthiskindofproblems.Ifavailable,it’seconomicallythoughtfultousespecialdevices.Safetyapplicationsthatrequirehighestdegreeofreliabilityshouldcontainsimplestdevicesandcircuitspossible.Thereisarulethateverynewlinkinchaindecreasesoverallreliability.Insmallapplicationsit’softencostsavingtouserelay-basedcircuitsinsteadofPLC-s.Progressinprocessautomationsystemsisaimingatsocalledcompleteautomatiowhenallthehumanhastodoistoentertheparametersoftheproductwantedandeverythingelseiscarriedoutbymachines(Rosin,2000).Althoughthedestinationliesfarahead,trendsindicatemovementinthatdirection.Firstly,systemsbecomemoreandmorestandardized.Bigmanufacturersorganizetheirproductsintofamilies.Theaimistoreduceamountofknowledgeneededforconfigurationandmaintenanceworksofdifferentdevicesfromsamecompany.It’salsoimportantthatthiswaybuiltapplicationsareeasilyexpandable.Secondly,importanceofcommunicationisrising(Hughes,2000).Therearemanyreasons,someofmoreessentialsare:Bettercollaborationofdifferentpartsofthesystem.Cuttingcostsoncabling.Lesscablingresultsfallinfaultprobability,butalsoincreasesseverityofonesthatoccur.Sensorsandactuatorscanbeatlongerdistancesfromtheprocessormodulethanifusingconventionalmethods.Increasedscalabilityofthesystems.Newdevicescanbeaddedatminimalcosts.Atsomecasesitisbettertomakearchitectureofmanysmallindependentmodulesandnetworkthem.Thissolutionenablessystemtokeepworkingalthoughsomepartshavefailed.Communicationnetworkseasefaultdiagnosticsandprovideremotemanagementpossibilities.Centraloperatingstationscanbeformedrelativelyeasy.?Possibilitytoconnectdevicesformdifferentmanufacturers(OPCFoundation,2003).ThirdimportanttendencyisspreadinguseofsocalledsoftwarecontrollersorSoftPLC-s(SiemensAG,2003).ThesearePCsoftware-basedsolutionsthatrelatewithfielddevicesviacommunicationnetworks.Thereisnoneedforprocessormodule,resourcesofPCareused.SomeSoftPLC-sarestillformedasprocessorcardsforPC.Reliablecommunicationnetworksareessential.SoftPLC-sarewellsuitedfordataacquisitionapplicationsbecauseofdatastoragepossibilitiesofPC-s.Fourthly,combo-devices(figure2)thatcontainbothoperatorpanelandmediumsizeprocessormodulegainpopularity(SiemensAG,2002).Inthissolutionpossibilityofdisturbancesislowandreuseofsomecomponentsmakewholepackagecheaper.Fifthly,processorsoftwaretakesoverpropertiesfromPCsoftware.Datacollectedfromproductioncanbeeasilytransferredintoofficeapplications(SiemensAG,2000).REFERENCESHughes,T.A.ProgrammableControllers,ThirdEdition.ISA-TheInstrumentation,Systems,andAutomationSociety,2000,334p.Jack,H.AutomatingManufacturingSystemswithPLC-s,828p.,Available:/~jackh/books/plcs/pdf/plcbook4_2.pdf,Accessed:3.10.2003LOGO!Manual.SiemensAG,2003,312p.OPCFoundationhomepage:/,Accessed:9.11.2003Rosin,A.ProgrammableControllersSimaticS7.Tallinn,TTU,2000,120p.[MasterThesis]-inEstonian.Berger,H.AutomatingwithSIMATIC.SiemensAG,2003,214p.SIMATICProgrammingwithSTEP7V5.2:Manual.SiemensAG,2002,610p.SIMATICS7-200ProgrammableControllerSystemManual.SiemensAG,2003,474p.SIMATICHMIWinCCConfigurationManual.Volume1,2,3.SiemensAG2000,468p.574thInternationalDAAAMConference"INDUSTRIALENGINEERING-NNOVATIONASCOMPETITIVEEDGEFORSME"29-30thApril2004,Tallinn,EstoniaAhtiMikkor,LembitRoosimolderDepartmentofProductDevelopment,InstituteofMachinery,

TallinnTechnicalUniversity,Ehitajatetee5,19086Tallinn,Estonia

ahti.mikkor@摘要現(xiàn)在，控制問題解決了使用操作各種各樣的技術(shù)：電子，液壓，氣動和機(jī)械。功能、可靠性和控制系統(tǒng)的價格是由方案的質(zhì)量來決定的。本文主要介紹的可編程邏輯控制器是基于五年項(xiàng)目開發(fā)經(jīng)驗(yàn)得來的。成功的解決方案和問題正是關(guān)注的焦點(diǎn)。特定的硬件，控制器編程問題，數(shù)據(jù)/信號改變和人機(jī)界面，也會被考慮到。作為一個結(jié)果，選擇方法根據(jù)具體的需求可編程控制器的設(shè)計與開發(fā)。實(shí)用的建議,提出了可能的危害和警告或許有助于避免犯錯誤。關(guān)鍵詞可編程控制器PLC自動化自動化系統(tǒng)過程自動化1簡介現(xiàn)代機(jī)械包括機(jī)械和電子兩部分。整體功能是由各組件的平衡共同決定的。最初的計劃和解決方案的選擇對最終結(jié)果起至關(guān)重要的作用。在基于繼電器電路、特殊裝置可編程邏輯控制器(PLC)和新的發(fā)展電子產(chǎn)品等控制方法之間做出選擇。這篇文章集中在PLC-s和手機(jī)了5年以上用PLC-s實(shí)際工作的經(jīng)驗(yàn)。對強(qiáng)、弱邊，正面和負(fù)面的實(shí)踐進(jìn)行了探討。建議使用可編程控制器而不是已經(jīng)形成來幫助決策。在規(guī)劃的最重要的決定是基于PLC系統(tǒng)選擇處理器類型。修正的錯誤就是額外的費(fèi)用甚至需要全新的裝置。最常見的錯誤是過高估計了編程的可能性和小型處理器。有幾種方法為選擇可編程序控制器(PLC)。不幸的是,他們中的大多數(shù)集中在電氣的方面PLC-s計數(shù)信號和最大允許的信號。他們不涉及可能的特殊需求的分析來確定為用戶程序或通訊。基于現(xiàn)有的幾個方法、實(shí)踐經(jīng)驗(yàn)和未來的發(fā)展趨勢,提供了一種新的方法選擇可編程序控制器(PLC)出現(xiàn)了。MikkorAhti通過參加超過15個大型自動化工程取得了他的經(jīng)驗(yàn)。這些項(xiàng)目包括發(fā)展電力消費(fèi)市場的不斷監(jiān)測系統(tǒng)在北歐水泥廠、更新測試試驗(yàn)臺為流量計、建筑Ahtme比作汽輪機(jī)安全系統(tǒng)、水處理設(shè)備，在波瓦拉克維里城鎮(zhèn)污水處理裝置和在塔爾圖中央供暖網(wǎng)絡(luò)監(jiān)控系統(tǒng)的發(fā)展。2使用可編程控制器的優(yōu)點(diǎn)和缺點(diǎn)2.1積極的爭論可編程控制器提供的主要優(yōu)勢是其靈活性。這是由于系統(tǒng)可以通過程序輕易的改變而不是其他任何選擇。特殊裝置為例做任何變化在控制算法很難實(shí)施。靈活性使PLC-s很適合頻繁改變應(yīng)用程序，例如在機(jī)器人學(xué)。在PLC-s輸入和輸出之間的關(guān)系是由用戶程序。通過采用先進(jìn)的編程技術(shù)，它是比任何天生的解決方案都非常容易實(shí)現(xiàn)復(fù)雜的控制算法。它使PLC-s非常激烈復(fù)雜的任務(wù)，例如在控制化學(xué)反應(yīng)過程。特殊模塊允許大量的不同信號連接到PLC控制系統(tǒng)。使用中應(yīng)考慮的PLC-s應(yīng)用程序需要一些“特別”的輸入或輸出信號。典型的例子就是定位以參考數(shù)據(jù)，從高速輸入。典型的PC可視化軟件是PLC-s,也有一些特殊裝置PC套裝軟體。在PLC-s之間有廣泛的通訊選擇使人們有可能從現(xiàn)場設(shè)備到一個中央控制的觀點(diǎn)收集所有的信息?，F(xiàn)代通信技術(shù)能夠使遠(yuǎn)程診斷和配置(杰克,2003)。這兩個顯著地降低系統(tǒng)的整體維護(hù)成本。2.2消極的爭論可編程控制器沒有足夠的內(nèi)存來存儲大量的數(shù)據(jù)。盡管未來趨勢顯示PLC內(nèi)存的增長，但是特殊裝置可編程序控制器(PLC)里記憶體的大小(錄音機(jī))仍然更好地適用于獨(dú)立的應(yīng)用程序。對于網(wǎng)絡(luò)解決方案有可能使用可視化軟件一起，以達(dá)到預(yù)期PLC-s所收集的數(shù)據(jù)在任何數(shù)據(jù)庫格式是很必要的。如果記錄的數(shù)據(jù)量是小的或也有控制功能包括，可以合理的PLC-s仍在使用。關(guān)于可視化軟件令人改性的是，在標(biāo)準(zhǔn)版本下，大多數(shù)不支持離線的記錄,在溝通是白的情況下不肯能獲得從PLC返回的數(shù)據(jù)?，F(xiàn)代通信選項(xiàng)包括標(biāo)準(zhǔn)協(xié)議PLC-s,例如以太網(wǎng)。人們傾向于使用現(xiàn)有的辦公室網(wǎng)絡(luò)也為數(shù)據(jù)載體，自動化系統(tǒng)的通信。時間已經(jīng)表明它是更好的方法把這些兩相分離的不斷的進(jìn)行網(wǎng)絡(luò)交流。在自動化系統(tǒng)的通信中，幾乎有可追溯性的顳網(wǎng)絡(luò)超負(fù)荷會導(dǎo)致一些問題。所有PLC-s都需要被編程。所有的編程程序在風(fēng)險控制中包含偶然誤差。特殊裝置，通常能夠很好的檢測