已阅读5页,还剩7页未读, 继续免费阅读
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
1英文原文IntroductiontoModernControlTheorySeveralfactorsprovidedthestimulusforthedevelopmentofmoderncontroltheory:a.Thenecessaryofdealingwithmorerealisticmodelsofsystem.b.Theshiftinemphasistowardsoptimalcontrolandoptimalsystemdesign.c.Thecontinuingdevelopmentsindigitalcomputertechnology.d.Theshortcomingofpreviousapproaches.e.Recognitionoftheapplicabilityofwell-knownmethodsinotherfieldsofknowledge.Thetransitionfromsimpleapproximatemodels,whichareeasytoworkwith,tomorerealisticmodels,producestwoeffects.First,alargenumberofvariablesmustbeincludedinthemodels.Second,amorerealisticmodelismorelikelytocontainnonlinearitiesandtime-varyingparameters.Previouslyignoredaspectsofthesystem,suchasinteractionswithfeedbackthroughtheenvironment,aremorelikelytobeincluded.Withanadvancingtechnologicalsociety,thereisatrendtowardsmoreambitiousgoals.Thisalsomeansdealingwithcomplexsystemwithalargenumberofinteractingcomponents.Theneedforgreateraccuracyandefficiencyhaschangertheemphasisoncontrolsystemperformance.Theclassicalspecificationsintermsofpercentovershoot,settingtime,bandwidth,etc.haveinmanycasesgivenwaytooptimalcriteriasuchasminimumenergy,minimumcost,andminimumtimeoperation.Optimizationofthesecriteriamakesitevenmoredifficulttoavoiddealingwithunpleasantnonlinearities.Optimalcontroltheoryoftendictatesthatnonlineartime-varyingcontrollawsareused,evenifthebasicsystemislinearandtime-invariant.Thecontinuingadvancesincomputertechnologyhavehadthreeprincipaleffectsonthecontrolsfield.Oneoftheserelatestothegiganticsupercomputers.Thesizeand2theclassoftheproblemsthatcannowbemodeled,analyzed,andcontrolledareconsiderablylargethantheywerewhenthefirsteditionofthisbookwaswritten.ThesecondimpactofthecomputertechnologyhastosowiththeproliferationandwideavailabilityofthemicrocomputersinhomesandItheworkplace,classicalcontroltheorywasdominatedbygraphicalmethodsbecauseatthetimethatwastheonlywaytosolvecertainproblems,Noweverycontroldesignerhaseasyaccesstopowerfulcomputerpackagesforsystemsanalysisanddesign.Theoldgraphicalmethodshavenotyetdisappeared,buthavebeenautomated.Theysurvivebecauseoftheinsightandintuitionthattheycanprovide,somedifferenttechniquesareoftenbettersuitedtoacomputer.Althoughacomputercanbeusedtocarryouttheclassicaltransform-inversetransformmethods,itisusedusuallymoreefficientforacomputertointegratedifferentialequationsdirectly.Thethirdmajorimpactofthecomputersisthattheyarenowsocommonlyusedasjustanothercomponentinthecontrolsystems.Thismeansthatthediscrete-timeanddigitalsystemcontrolnowdeservesmuchmoreattentionthanitdidinthepast.Moderncontroltheoryiswellsuitedtotheabovetrendsbecauseitstime-domaintechniquesanditsmathematicallanguage(matrices,linearvectorspaces,etc.)areidealwhendealingwithacomputer.Computersareamajorreasonfortheexistenceofstatevariablemethods.Mostclassicalcontroltechniquesweredevelopedforlinearconstantcoefficientsystemswithoneinputandoneoutput(perhapsafewinputsandoutputs).ThelanguageofclassicaltechniquesistheLaplaceorZ-transformandtransferfunctions.Whennonlinearitiesadtimevariationsarepresent,theverybasisfortheseclassicaltechniquesisremoved.Somesuccessfultechniquessuchasphase-planemethods,describingfunctions,andotheradhocmethods,havebeendevelopedtoalleviantthisshortcoming.However,thegreatestsuccesshasbeenlimitedtolow-ordersystems.Thestatevariableapproachofmoderncontroltheoryprovidesauniformandpowerfulmethodofrepresentingsystemsofarbitraryorder,linearornonlinear,withtime-varyingorconstantcoefficient.Itprovidesanidealformulationforcomputerimplementation3andisresponsibleformuchoftheprogressinoptimizationtheory.Moderncontroltheoryisarecentdevelopmentinthefieldofcontrol.Therefore,thenameisjustifiedatleastasadescriptivetitle.However,thefoundationsofmoderncontroltheoryaretobefoundinotherwell-establishedfields.RepresentingasystemintermsofstatevariablesisequivalenttotheapproachofHamiltonianmechanics,usinggeneralizedcoordinatesandgeneralizedmoment.Theadvantagesofthisapproachhavebeenwell-knownIclassicalphysicsformanyyears.Theadvantagesofusingmatriceswhendealingwithsimultaneousequationsofvariouskindshavelongbeenappreciatedinappliedmathematics.Thefieldoflinearalgebraalsocontributesheavilytomoderncontroltheory.Thisisduetotheconcisenotation,thegeneralityoftheresults,andtheeconomyofthoughtthatlinearalgebraprovides.MechanismofSurfaceFinishProductionTherearebasicallyfivemechanismswhichcontributetotheproductionofasurfacewhichhavebeenmachined.Thereare:(1)Thebasicgeometryofthecuttingprocess.In,forexample,singlepointturningthetoolwilladvanceaconstantdistanceaxiallyperrevolutionoftheworkpieceandtheresultantsurfacewillhaveonit,whenviewedperpendicularlytothedirectionoftoolfeedmotion,aseriesofcuspswhichwillhaveabasicformwhichreplicatestheshapeofthetoolincut.(2)Theefficiencyofthecuttingoperation.Ithasalreadybeenmentionedthatcuttingwithunstablebuilt-up-edgeswillproduceasurfacewhichcontainshardbuilt-up-edgefragmentswhichwillresultinadegradationofthesurfacefinish.Itcanalsobedemonstratedthatcuttingunderadverseconditionssuchasapplywhenusinglargefeedssmallrakeanglesandlowcuttingspeeds,besidesproducingconditionswhichcontinuousshearoccurringintheshearzone,tearingtakesplace,discontinuouschipsofuneventhicknessareproduced,andtheresultantsurfaceispoor.Thissituationisparticularlynoticeablewhenmachiningveryductilematerialssuchascopperandaluminum.4(3)Thestabilityofthemachinetool.Undersomecombinationsofcuttingconditions:workpiecesize,methodofclamping,andcuttingtoolrigidityrelativetothemachinetoolstructure,instabilitycanbesetupinthetoolwhichcausesittovibrate.Undersomeconditionsthevibrationwillbuiltupandunlesscuttingisstoppedconsiderabledamagetoboththecuttingtoolandworkpiecemayoccur.Thisphenomenonisknownaschatterandinaxialturningischaracterizedbylongpitchhelicalbandsontheworkpiecesurfaceandshortpitchundulationsonthetransientmachinedsurface.(4)Theeffectivenessofremovingswarf.Indiscontinuouschipproductionmachining,suchasmillingorturningofbrittlematerials,itisexpectedthatthechip(swarf)willleavethecuttingzoneeitherundergravityorwiththeassistanceofajetofcuttingfluidandthattheywillnotinfluencethecutsurfaceinanyway.However,whencontinuouschipproductionisevident,unlessstepsatetakentocontroltheswarfitislikelythatitwillimpingeonthecutsurfaceandmarkit.Inevitably,thismarkingbesidealookingunattractive,oftenresultsinapoorersurfacefinishing,(5)Theeffectiveclearanceangleonthecuttingtool.Forcertaingeometriesofminorcuttingedgereliefandclearanceanglesitispossibletocutonthemajorcuttingedgeandburnishontheminorcuttingedge.Thiscanprodu
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 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,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 2023年12月湖北省潜江市政务服务和大数据管理局公开选调公务员和事业单位工作人员笔试近6年高频考题难、易错点荟萃答案带详解附后
- 2023年12月深圳市罗湖区教育系统公办幼儿园公开招聘28名教研员2笔试近6年高频考题难、易错点荟萃答案带详解附后
- 2023年12月浙江金华兰溪市未成年人心理辅导中心专职人员招考聘用笔试近6年高频考题难、易错点荟萃答案带详解附后
- 2023年12月江西都市城际公交有限公司公开招聘8人(鄱阳驾驶员)笔试近6年高频考题难、易错点荟萃答案带详解附后
- 2023年12月广西柳州市钢一中学赴南宁参加2024届广西综合性高校毕业生就业双选会笔试近6年高频考题难、易错点荟萃答案带详解附后
- 2023年12月广西农工党北海市委会1人笔试近6年高频考题难、易错点荟萃答案带详解附后
- 公司员工周工作总结计划2
- 2023年12月广东东莞市电子商贸学校招考聘用编外工作人员笔试近6年高频考题难、易错点荟萃答案带详解附后
- 移动实习报告
- 实训报告万能模板幼师
- 冷藏车保温箱冰排使用记录
- 《水产品加工学》课程教学大纲
- 二年级下册美术课件-第18课 听听画画(5)-湘美版
- DeepStructureofCulture文化的深层结构
- GB∕T 799-2020 地脚螺栓-行业标准
- 第三次全国国土调查数据库建设报告
- 体验式班会课的设计与实施课件
- VMAX存储运维操作手册
- 田径活动记录第一学期记录
- 中考论述题常用观点及示例
- DB32∕T 3586-2019 自助洗车场建设管理规范
评论
0/150
提交评论