自动化专业英语论文(附译文)(华北电力大学)

分数:___________任课教师签字：___________华北电力大学本科生结课作业学年学期：2011-2012学年第二学期课程名称：专业外语阅读(自动化)学生姓名：学号：提交时间：2012年6月19日TheMajorComponentAssemblyLineofanAircraftEveryBoeingcommercialisairplaneiscustomizedforaspecificcustomer.ManufacturingprocessesofsomemajorcomponentaredesirabletofollowtheFMSconceptinacustomizedmanufacturingenvironment.Inthecasestudythatfollows,awingassemblyprocessisexaminedbymeansofdiscretesimulationmodeling.Therearemorethanthirtycomplexprocessesappliedtomorethanfifteenmachineclassesinthisexample.Mostprocessesrequireadifferentnumberoflaborentitiesfromvariouslaborclasses.Theoverallpaceofthewholesystemisdesiredtobeavariablethatimpactstheprocesstimeofallrelatedprocesses,aswellasthenumberofassignedlaborers.ThemodularapproachtoMCMsystemdesignnotonlybenefitstheoverallperformanceofflexibleMCMsystem,butalsoenhancessimulation-modelingexercises.Discreteeventsimulationtechnologyinthisstudyemploysthesameplatformconceptasinmodelinghighlyflexibleandrapidreconfigurableproductionlines.suchmodelingmethodsreflectmanufacturingprocessesaccordingtotheevery-changingcustomizeddemands.Manyfundamentalmanufacturingprocessparameters,suchaslayoutreconfigurations,andresourcere-allocations,canbederivedaheadoftimefromthesimulationmodels.Ahigh-levelprocessflowofthissimulationmodelisshownbelowinFigure5-4-1,wheresourcel1generatesincomingpartsaccordingtothesystemtakttimewithoptionalstatisticaldistributions.BufferSreceivesincomingpartsviatheonlycraneresourceinthesystem.ThepartwillthenbeliftedbythecranetothemachineBwheremultipleprocesseswillbeperformedbymultipleresources.ThepartthencontinuestomovefromthemachineBtothemachineP,theendoftheprocessline.Multipleprocessesareassignedthroughoutthislineoneachmachine.AnadditionalprocessisneededinthemiddleofthelinewherethepartwillbetransferredtothebufferAfollowedbyacoupleofexternalprocesses.Afterwards,bufferAreceivesthepartandcallsfortheoverheadcranetotransferthepartbacktobufferTwherethepartwillcontinuethroughtherestoftheprocess.Attheendoftheline,thepartgoesfromthemachinePtothebufferAthentothesink,whichisthefinaldestinationofallpartsinthesimulationmodel.Twodifferentpart-carryingplatformsareinvolvedinthesystem.The“highspeed”dollytransferspartstoandfrombufferA.The“lowspeed”dollycarriesonepartatatimefrommachineBallthewaytomachineP.additionalcomponentsareintroducedtothesystemfromsource2and3atdifferentstagesofthisprocessline.Resourceclasstypesinthismodelconsistoflabor,machine,andAutomaticGuidedVehicle(AGV)elements.Themachineclassstandsaloneforeachmachine,whilethelaborandAGVclassesaremanagedbytheirrespectivecontrollers.Thosethirtyplusprocessesthatarestand-aloneobjectscanbeassignedtomultiplemachines.Thus,eachmachinehasfromtwotosixassignedprocesses.Processesrunatalltimesinanendlessdo-loopaspartofthenatureoflogicanditsassignedtimedurationonthemachinewhereitresides.Afterthelastprocesssequenceofthelastmachineclasshasbeenexecuted,thepartistransferredtothesinkclasswhereitwillbelogicallydestroyedandremovedfromthemodelingsystem.AShopDataFilecontainingresource,layout,andprocessinformationofanassemblylineisusedtogenerateBatchControlLanguage(BCL)file,accordingtotheprocessdiscussedinthenextparagraph.ThisBCLfilecanthenbedirectlyexecutedinQUEST.TheaircraftmajorcomponentassemblylinesimulationiscreatedanddrivenbythisBCLfile.BecausethismodeliscreatedfromanXML-basedShopDataFile,modifyingscenariosofthemodelfilecanbeeasilyaccomplishedbychangingelementattributesofthesourceXMLfile.Asintheexampleshownabove,theBCLspecificcommends,suchasCREATEPARTCLASS,aremanagedintheXMLstylesheet.Simulationmodelobjectrelatedinformation,suchasthepartcolorandnameofthepartclass“Part737RHwing”areoriginatedfromtheShopDataFile.AcompletenewBCLisfilegeneratedperflexiblemanufacturingscenario.ThisBCLfilethenexecutesandgeneratesacustomizedQUESTsimulationmodelforitsmatchingconceptualFMSenvironment.Theapproachofthissimulationmodelingsuccessfullymanagesaflexiblecustomizedmanufacturingsysteminaflexiblymodulatedandcustomizedfashion.Foreachcomplicatedcustomizedscenario,itiscomprehensivethattraditionalmanualmodelingmodificationwilltakemuchlongereffortthanthistechnique.AscomparedtoalternativeapproachestothisMCMapplication,benefitofthisinnovativemethodologyisevidentinthefollowingpoints:●Customizable●Easeofdeployment●PortabilityoftheXML-baseshopdatafile●PopularityoftheXMLlanguage●Scalable●ReusableofthemodulatedseedmodelfileAdditionaldetailedverificationbetweensimulationmodelsandflexibleMCMexercisesontheshopfloorremaintobefullyperformedoncethisconceptualprocessdevelopmentturnsintoreality.Nevertheless,approachesandmethodologiespresentedinthisworkillustrateunparalleledadvantagesinoperatingflexibleandcustomizedmanufacturingsystems.Figure5-4-1ThesimulationmodelprocesssequenceReadingMaterialComparisonofSchedulingPoliciesSeveralverysimpleschedulingpolicieshavebeentestedonthesimulationmodel.Thisistheeasiestwaytousesimulationandimplementingthemwouldneedonlyminoradaptationoftheproductiontoolssinceinthecurrentstateofthesystemtheymainlyrepresentchangesintheoperator’sbehavior.Itisthe