外文翻译--应用于电气系统的可编程序控制器 英文版.pdf

Programmablecontrollerdesignedforelectro-pneumaticsystemsCheded,LAl-Mulla,MaanArchiveofAppliedMechanics74(2005)489-508Springer-Verlag2005DOI10.1007/s00419-004-0363-4DepartmentofMechanicalEngineering,SolidMechanics,TechnicalUniversityofAustraliaelectro-pneumaticcontrolelectricalThisprojectdealswiththestudyofelectro-pneumaticsystemsandtheprogrammablecontrollerthatprovidesaneffectiveandeasywaytocontrolthesequenceofthepneumaticactuatorsmovementandthestatesofpneumaticsystem.Theprojectofaspecificcontrollerforpneumaticapplicationsjointhestudyofautomationdesignandthecontrolprocessingofpneumaticsystemswiththeelectronicdesignbasedonmicrocontrollerstoimplementtheresourcesofthecontroller.1.IntroductionTheautomationsystemsthatusetechnologyareformedmainlybythreekindsofelements:actuatorsormotors,sensorsorbuttonsandcontrolelementslikevalves.Nowadays,mostofthecontrolelementsusedtoexecutethelogicofthesystemweresubstitutedbytheProgrammableLogicController(PLC).Sensorsandswitchesarepluggedasinputsandthedirectcontrolvalvesfortheactuatorsarepluggedasoutputs.Aninternalprogramexecutesallthelogicnecessarytothesequenceofthemovements,simulatesothercomponentslikecounter,timerandcontrolthestatusofthesystem.WiththeuseofthePLC,theprojectwinsagility,becauseitispossibletocreateandsimulatethesystemasmanytimesasneeded.Therefore,timecanbesaved,riskofmistakesreducedandcomplexitycanbeincreasedusingthesameelements.AconventionalPLC,thatispossibletofindonthemarketfrommanycompanies,offersmanyresourcestonotonlypneumaticsystems,butallkindsofsystemthatusescomponents.ThePLCcanbeveryversatileandrobusttobeappliedinmanykindsofapplicationintheindustryorevensecuritysystemandautomationofbuildings.Becauseofthosecharacteristics,insomeapplicationsthePLCofferstomuchresourcesthatarenotevenusedtocontrolthesystem,electro-pneumaticsystemisoneofthiskindofapplication.TheuseofPLC,especiallyforsmallsizesystems,canbeveryexpensivefortheautomationproject.Analternativeinthiscaseistocreateaspecificcontrollerthatcanoffertheexactlysizeandresourcesthattheprojectneeds3,4.Thiscanbemadeusingmicrocontrollersasthebaseofthiscontroller.Thecontroller,basedonmicrocontroller,canbeveryspecificandadaptedtoonlyonekindofmachineoritcanworkasagenericcontrollerthatcanbeprogrammedasausualPLCandworkwithlogicthatcanbechanged.Allthesecharacteristicsdependonwhatisneededandhowmuchexperiencethedesignerhaswithdevelopinganelectroniccircuitandfirmwareformicrocontroller.Butthemainadvantageofdesignthecontrollerwiththemicrocontrolleristhatthedesignerhasthetotalknowledgeofhiscontroller,whichmakesitpossibletocontrolthesizeofthecontroller,changethecomplexityandtheapplicationofit.Itmeansthattheprojectgetsmoreindependencefromothercompanies,butatthesametimetheresponsibilityofthecontrolofthesystemstaysatthedesignerhands2.Electro-pneumaticsystemOnautomationsystemonecanfindthreebasiccomponentsmentionedbefore,plusalogiccircuitthatcontrolsthesystem.Anadequatetechniqueisneededtoprojectthelogiccircuitandintegrateallthenecessarycomponentstoexecutethesequenceofmovementsproperly.Forasimpledirectsequenceofmovementanintuitivemethodcanbeused1,5,butforindirectormorecomplexsequencestheintuitioncangenerateaverycomplicatedcircuitandsignalmistakes.Itisnecessarytouseanothermethodthatcansavetimeoftheproject,makeacleancircuit,caneliminateoccasionalsignaloverlappingandredundantcircuits.Thepresentedmethodiscalledstep-by-steporalgorithmic1,5,itisvalidforpneumaticandelectro-pneumaticsystemsanditwasusedasabaseinthiswork.Themethodconsistsofdesigningthesystemsbasedonstandardcircuitsmadeforeachchangeonthestateoftheactuators,thesechangesarecalledsteps.Thefirstpartistodesignthosekindsofstandardcircuitsforeachstep,thenexttaskistolinkthestandardcircuitsandthelastpartistoconnectthecontrolelementsthatreceivesignalsfromsensors,switchesandthepreviousmovements,andgivetheairorelectricitytothesupplylinesofeachstep.InFigs.1and2thestandardcircuitsaredrawnforpneumaticandelectro-pneumaticsystem8.Itispossibletoseetherelationswiththepreviousandthenextsteps.3.ThemethodappliedinsidethecontrollerTheresultofthemethodpresentedbeforeisasequenceofmovementsoftheactuatorthatiswelldefinedbysteps.Itmeansthateachchangeonthepositionoftheactuatorsisanewstateofthesystemandthetransitionbetweenstatesiscalledstep.Thestandardcircuitdescribedbeforehelpsthedesignertodefinethestatesofthesystemsandtodefinetheconditiontoeachchangebetweenthestates.Intheendofthedesign,thesystemisdefinedbyasequencethatneverchancesandstatesthathavetheinputsandtheoutputswelldefined.Theinputsaretheconditionforthetransitionandtheoutputsaretheresultofthetransition.Alltheconfigurationofthosestepsstaysinsideofthemicrocontrollerandisexecutedthesamewayitwasdesigned.Thesequencesofstringsareprogrammedinsidethecontro