会员注册 | 登录 | 微信快捷登录 支付宝快捷登录 QQ登录 微博登录 | 帮助中心 人人文库renrendoc.com美如初恋!
站内搜索 百度文库

热门搜索: 直缝焊接机 矿井提升机 循环球式转向器图纸 机器人手爪发展史 管道机器人dwg 动平衡试验台设计

   首页 人人文库网 > 资源分类 > DOC文档下载

外文翻译--数字控制.doc

  • 资源星级:
  • 资源大小:106.00KB   全文页数:23页
  • 资源格式: DOC        下载权限:注册会员/VIP会员
您还没有登陆,请先登录。登陆后即可下载此文档。
  合作网站登录: 微信快捷登录 支付宝快捷登录   QQ登录   微博登录
友情提示
2:本站资源不支持迅雷下载,请使用浏览器直接下载(不支持QQ浏览器)
3:本站资源下载后的文档和图纸-无水印,预览文档经过压缩,下载后原文更清晰   

外文翻译--数字控制.doc

1附录Ⅰ外文文献NumericalControlOneofthemostfundamentalconceptsintheareaofadvancedmanufacturingtechnologiesisnumericalcontrol.ControllingamachinetoolusingapunchedtapeorstoredprogramisknownasnumericalcontrolNC.NChasbeendefinedbytheElectronicIndustriesAssociationEIAasasysteminwhichactionsarecontrolledbythedirectinsertionofnumericaldadaatsomepoint.thesystemmustautomaticallyinterpretatleastsomeportionofthisdata.thenumericaldatarequiredtoproduceapartisknownasapartprogram..AnumericalcontrolmachinetoolsystemcontainsamachinecontrolunitMCUandthemachinetoolitself.TheMCUisfurtherdividedintotwoelementsthedataprocessingunitDPUandthecontrolloopsunitCLU.TheDPUprocessesthecodeddatafromthetapeorothermediaandpassesinformationonthepotionsofeachaxis,requireddirectionofmotion,feedrate,andauxiliaryfunctioncontrolsignalstotheCLU.TheCLUoperatesthedrivemechanismsofthemachine,receivesfeedbacksignalsconcerningtheactualpositionandvelocityofeachoftheaxes,andsignalsthecompletionofoperation.TheDPUsequentiallyreadsthedata.WheneachlinehascompletedexecutionasnotedbytheCLU,antherlineofdataisread.Adataprocessingunitsconsistsofsomeorallofthefollowingparts1Datainputdevicesuchasapapertapereader,magnetictapereader,RS232Cport,etc2Datareadingcircuitsandparitycheckinglogic3Decodingcircuitsfordistributingdataamongthecontrolledaxes4Aninterpolator,whichsuppliesmachinemotioncommandsbetweendatapointsfortoolmotionAcontrolloopsunit,ontheotherhandconsistsofthefollowing1Positioncontrolloopsforalltheaxesofmotion,whereeachaxishasaseparatecontrolloop2Velocitycontrolloops,wherefeedcontrolisrequired3Decelerationandbacklashtakeupcircuits4Auxiliaryfunctionscontrol,suchascoolanton/off,gearchange,spindleon/offcontrol2GeometricandkinematicdataaretypicallyfedfromtheDPUtotheCLU.TheCLUthengovernsthephysicalsystembasedonthedatafromtheDPU.Numericalcontrolwasdevelopedtoovercomethelimitationofhumanoperators,andithasdoneso.Numericalcontrolmachinesaremoreaccuratethanmanuallyoperatedmachines,theycanproducepartsmoreuniformly,theyarefaster,andthelongruntoolingcostsarelower.ThedevelopmentofNCledtothedevelopmentofseveralotherinnovationsinmanufacturingtechnologyElectricdischargemachiningLasercuttingElectronbeamweldingNumericalcontrolhasalsomademachinetoolsmoreversatilethantheirmanuallyoperatedpredecessors.AnNCmachinetoolcanautomaticallyproduceawidevarietyofparts,eachinvolvinganassortmentofwidelyvariedandcomplexmachiningprocesses.Numericalcontrolhasallowedmanufacturerstoundertaketheproductionofproductsthatwouldnothavebeenfeasiblefromaneconomicperspectiveusingmanuallycontrolledmachinetoolsandprocesses.HistoricalDevelopmentofNCLikesomanyadvancedtechnologies,NCwasborninthelaboratoriesoftheMassachusettsInstituteofTechnology.TheconceptofNCwasdevelopedintheearly1950swithfundingprovidedbytheU.S.AirForce.Initsearlieststages,NCmachineswereabletomakestraightcutsefficientlyandeffectively.However,curvedpathswereaproblembecausethemachinetoolhadtobeprogrammedtoundertakeaseriesofhorizontalandverticalstepstoproduceacurve.Theshorterthestraightlinesmakingupthesteps,thesmootheristhecurve.EachlinesegmentinthestepsshowninthecloseupinFig.2.17hadtobecalculated.ThiswasacumbersomeapproachthathadtobeovercomeifNCwastodevelopfurther.Thisproblemledtothedevelopmentin1959oftheAutomaticallyProgrammedToolsAPTlanguage.ThisisaspecialprogramminglanguageforNCthatusesstatementssimilartoEnglishlanguagetodefinethepartgeometry,describethecuttingtoolconfiguration,andspecifythenecessarymotions.ThedevelopmentoftheAPTlanguagewasamajorstepforwardinthedevelopmentofNCtechnology.TheoriginalNCsystemswerevastlydifferentfromthoseusedtoday.Themachineshadhardwiredlogiccircuits.Theinstructionalprogramswerewrittenonpunchedpaper,whichwaslatertobereplacedbymagneticplastic3tape.Atapereaderwasusedtointerprettheinstructionswrittenonthetapeforthemachine.Together,allofthisrepresentedagiantstepforwardinthecontrolofmachinetools.However,therewereanumberofproblemswithNCatthispointinitsdevelopment.Amajorproblemwasthefragilityofthepunchedpapertapemedium.Itwascommonforthepapercontainingtheprogrammedinstructionstobreakortearduringamachiningprocess.Thisproblemwasexacerbatedbythefactthateachsuccessivetimeapartwasproducedonamachinetool,thepapertapecarryingtheprogrammedinstructionshadtobererunthroughthereader.Ifitwasnecessarytoproduce100copiesofagivenpart,itwasalsonecessarytorunthepapertapethroughthereader100separatetimes.Fragilepapertapessimplycouldnotwithstandtherigorsofashotfloorenvironmentandthiskindofrepeateduse.Thisledtothedevelopmentofaspecialmagneticplastictape.Whereasthepapertapecarriedtheprogrammedinstructionsasaseriesofholespunchedinthetape,theplastictapecarriedtheinstructionsasaseriesofmagneticdots.Theplastictapewasmuchstrongerthanthepapertape,whichsolvedtheproblemoffrequenttearingandbreakage.However,itstilllefttwootherproblems.Themostimportantofthosewasthatitwasdifficultorimpossibletochangetheinstructionsenteredonthetape.Tomakeeventhemostminoradjustmentsinaprogramofinstructions,itwasnecessarytointerruptmachiningoperationsandmakeanewtape.Itwasalsostillnecessarytorunthetapethroughthereaderasmanytimesastherewerepartstobeproduced.Fortunately,computertechnologybecamearealityandsoonsolvedtheproblemofNCassociatedwithpunchedpaperandplastictape.1AdventofDirectNumericalControlThedevelopmentofaconceptknownasdirectnumericalcontrolDNCsolvedthepaperandplastictapeproblemsassociatedwithnumericalcontrolbysimplyeliminatingtapeasthemediumforcarryingtheprogrammedinstructions.Indirectnumericalcontrol,machinetoolsaretied,viaadatatransmissionlink,toahostcomputerFig2.18.Programsforoperatingthemachinetoolsarestoredinthehostcomputerandfedtothemachinetoolasneededviathedatatransmissionlinkage.Directnumericalcontrolrepresentedamajorstepforwardoverpunchedtapeandplastictape.However,itissubjecttothesamelimitationsasalltechnologiesthatdependonahostcomputer,themachinetoolsalsoexperiencedowntime.Thisproblemledtothedevelopmentofcomputernumericalcontrol.42AdventofComputerNumericalControlThedevelopmentofthemicroprocessorallowedforthedevelopmentofprogrammablelogiccontrollersPLCsandmicrocomputer.ThesetwotechnologiesallowedforthedevelopmentofcomputernumericalcontrolCNC.WithCNC,eachmachinetoolhasaPLCoramicrocomputerthatservesthepurpose.Thisallowsprogramstobeinputandstoredateachindividualmachinetool.Italsoallowsprogramstobedevelopedofflineanddownloadedattheindividualmachinetool.CNCsolvedtheproblemsassociatedwithdowntimeofthehostcomputer,butitintroducedanotherproblemknownasdatamanagement.Thisisaproblemallworksettingsdependentonmicrocomputershave.Thesameprogrammightbeloadedontendifferentmicrocomputerswithnocommunicationamongthem.Thisproblemistheprocessofbeingsolvedbylocalareanetworksthatconnectmicrocomputersforbetterdatamanagement.Theproblemofdatamanagementledtothedevelopmentofdistributednumericalcontrol.3AdventofDistributedNumericalControlDistributednumericalcontrolalsocalledDNCtakesadvantageofthebestaspectsofdirectnumericalcontrolandcomputernumericalcontrol.WithdistributednumericalcontroltherearebothhostcomputersandlocalcomputersattheindividualmachinetoolsFig2.19.Thisallowstheprogramstobestoredinthehostcomputersand,thereby,bettermanaged.However,italsoallowsthemtobedownloadedtolocalmicrocomputersorPLCs.ItalsoallowsforlocalinputandinteractionthroughmicrocomputersorPLCsatthemachinelevels.NCMachineComponentsTherearefourcomponentsinanyNCmachineTheactualNCtoolThemachinecontrolunitMCUThecommunicationinterfacebetweentheNCmachineandtheMCUAvarietyofaccessoriesforperformingspecificjobsontheNCmachineTheactualNCmachinemaybeamillingmachine,lathe,drill,oranyothertypeofmachinetool..TheMCUisthecontrolunitthatholdstheprogramsthatinstructtheNCmachine.TheMCUalsohasvariousdevicesavailableforoperatorinput.InformationcontainedintheMCUiscarriedtotheactivatorsontheNCmachinethroughthecommunicationinterface.TheseactivatorsreceivetheelectronicsignalsfromtheMCUand

注意事项

本文(外文翻译--数字控制.doc)为本站会员(英文资料库)主动上传,人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知人人文库网([email protected]),我们立即给予删除!

温馨提示:如果因为网速或其他原因下载失败请重新下载,重复下载不扣分。

copyright@ 2015-2017 人人文库网网站版权所有
苏ICP备12009002号-5