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标准文档外文翻译院（系）专业班级姓名学号指导教师年月日标准文档Programmabledesignedforelectro-pneumaticsystemscontrollerJohnF.WakerlyThisprojectdealswiththestudyofelectro-pneumaticsystemsandtheprogrammablecontrollerthatprovidesaneffectiveandeasywaytocontrolthesequenceofthepneumaticactuatorsmovementandthestatesofpneumaticsystem.Theprojectofaspecificcontrollerforpneumaticapplicationsjointhestudyofautomationdesignandthecontrolprocessingofpneumaticsystemswiththeelectronicdesignbasedonmicrocontrollerstoimplementtheresourcesofthecontroller.1.IntroductionTheautomationsystemsthatuseelectro-pneumatictechnologyareformedmainlybythreekindsofelements:actuatorsormotors,sensorsorbuttonsandcontrolelementslikevalves.Nowadays,mostofthecontrolelementsusedtoexecutethelogicofthesystemweresubstitutedbytheProgrammableLogicController(PLC).Sensorsandswitchesarepluggedasinputsandthedirectcontrolvalvesfortheactuatorsarepluggedasoutputs.Aninternalprogramexecutesallthelogicnecessarytothesequenceofthemovements,simulatesothercomponentslikecounter,timerandcontrolthestatusofthesystem.WiththeuseofthePLC,theprojectwinsagility,becauseitispossibletocreateandsimulatethesystemasmanytimesasneeded.Therefore,timecanbesaved,riskofmistakesreducedandcomplexitycanbeincreasedusingthesameelements.AconventionalPLC,thatispossibletofindonthemarketfrommanycompanies,offersmanyresourcestocontrolnotonlypneumaticsystems,butallkindsofsystemthatuseselectricalcomponents.ThePLCcanbeveryversatileandrobusttobeappliedinmanykindsofapplicationintheindustryorevensecuritysystemandautomationofbuildings.标准文档Becauseofthosecharacteristics,insomeapplicationsthePLCofferstomuchresourcesthatarenotevenusedtocontrolthesystem,electro-pneumaticsystemisoneofthiskindofapplication.TheuseofPLC,especiallyforsmallsizesystems,canbeveryexpensivefortheautomationproject.Analternativeinthiscaseistocreateaspecificcontrollerthatcanoffertheexactlysizeandresourcesthattheprojectneeds[3,4].Thiscanbemadeusingmicrocontrollersasthebaseofthiscontroller.Thecontroller,basedonmicrocontroller,canbeveryspecificandadaptedtoonlyonekindofmachineoritcanworkasagenericcontrollerthatcanbeprogrammedasausualPLCandworkwithlogicthatcanbechanged.Allthesecharacteristicsdependonwhatisneededandhowmuchexperiencethedesignerhaswithdevelopinganelectroniccircuitandfirmwareformicrocontroller.Butthemainadvantageofdesignthecontrollerwiththemicrocontrolleristhatthedesignerhasthetotalknowledgeofhiscontroller,whichmakesitpossibletocontrolthesizeofthecontroller,changethecomplexityandtheapplicationofit.Itmeansthattheprojectgetsmoreindependencefromothercompanies,butatthesametimetheresponsibilityofthecontrolofthesystemstaysatthedesignerhands2.Electro-pneumaticsystemOnautomationsystemonecanfindthreebasiccomponentsmentionedbefore,plusalogiccircuitthatcontrolsthesystem.Anadequatetechniqueisneededtoprojectthelogiccircuitandintegrateallthenecessarycomponentstoexecutethesequenceofmovementsproperly.Forasimpledirectsequenceofmovementanintuitivemethodcanbeused[1,5],butforindirectormorecomplexsequencestheintuitioncangenerateaverycomplicatedcircuitandsignalmistakes.Itisnecessarytouseanothermethodthatcansavetimeoftheproject,make标准文档acleancircuit,caneliminateoccasionalsignaloverlappingandredundantcircuits.Thepresentedmethodiscalledstep-by-steporalgorithmic[1,5],itisvalidforpneumaticandelectro-pneumaticsystemsanditwasusedasabaseinthiswork.Themethodconsistsofdesigningthesystemsbasedonstandardcircuitsmadeforeachchangeonthestateoftheactuators,thesechangesarecalledsteps.标准文档Thefirstpartistodesignthosekindsofstandardcircuitsforeachstep,thenexttaskistolinkthestandardcircuitsandthelastpartistoconnectthecontrolelementsthatreceivesignalsfromsensors,switchesandthepreviousmovements,andgivetheairorelectricitytothesupplylinesofeachstep.InFigs.1and2thestandardcircuitsaredrawnforpneumaticandelectro-pneumaticsystem[8].Itispossibletoseetherelationswiththepreviousandthenextsteps.3.ThemethodappliedinsidethecontrollerTheresultofthemethodpresentedbeforeisasequenceofmovementsoftheactuatorthatiswelldefinedbysteps.Itmeansthateachchangeonthepositionoftheactuatorsisanewstateofthesystemandthetransitionbetweenstatesiscalledstep.Thestandardcircuitdescribedbeforehelpsthedesignertodefinethestatesofthesystemsandtodefinetheconditiontoeachchangebetweenthestates.Intheendofthedesign,thesystemisdefinedbyasequence标准文档thatneverchancesandstatesthathavetheinputsandtheoutputswelldefined.Theinputsaretheconditionforthetransitionandtheoutputsaretheresultofthetransition.Alltheconfigurationofthosestepsstaysinsideofthemicrocontrollerandisexecutedthesamewayitwasdesigned.Thesequencesofstringsareprogrammedinsidethecontrollerwith5bytes;eachstringhastheconfigurationofonestepoftheprocess.Therearetwobytesfortheinputs,onebytefortheoutputsandtwomorefortheotherconfigurationsandauxiliaryfunctionsofthestep.Afterprogramming,thissequenceofstringsissavedinsideofanon-volatilememoryofthemicrocontroller,sotheycanbereadandexecuted.ThecontrollertaskisnottoworkinthesamewayasaconventionalPLC,butthepurposeofitistobeanexampleofaversatilecontrollerthatisde