畢業(yè)設(shè)計(jì)(論文)-電動(dòng)自行車智能控制器的設(shè)計(jì)與制作

)式中為占空比。改變?chǔ)?，即可改變其平均電壓?.3.5無(wú)刷直流電動(dòng)機(jī)及控制器的保護(hù)如圖2-12所示：圖2-12保護(hù)電路一、電機(jī)過(guò)流和過(guò)熱保護(hù)電機(jī)過(guò)流保護(hù)和過(guò)熱保護(hù)（電機(jī)的過(guò)載保護(hù)和小電流過(guò)載保護(hù)也可以通過(guò)過(guò)熱保護(hù)來(lái)實(shí)現(xiàn)），由單片機(jī)循環(huán)檢測(cè)電機(jī)電流樣值信號(hào)和電機(jī)過(guò)熱信號(hào),檢測(cè)到任何一種信號(hào),單片機(jī)將進(jìn)入保護(hù)方式，令單片機(jī)輸出的PWM信號(hào)變?yōu)榱忝}寬，使電機(jī)失電，同時(shí)借助于自行車本身的制動(dòng)系統(tǒng)，使自行車停止前進(jìn)。如圖所示，此兩種信號(hào)由P0.0和P0.1提供。二、蓄電池欠壓保護(hù)系統(tǒng)軟件設(shè)計(jì)時(shí),當(dāng)出現(xiàn)欠壓信號(hào)時(shí)，并不是馬上就切斷主回路，而是在一定時(shí)間內(nèi)連續(xù)檢測(cè)欠壓信號(hào)，如果欠壓信號(hào)保持兩秒鐘，系統(tǒng)將進(jìn)入欠壓保護(hù)報(bào)警程序，如果欠壓信號(hào)持續(xù)不到兩秒鐘，系統(tǒng)就不進(jìn)入保護(hù)報(bào)警程序，繼續(xù)正常工作。如圖所示，此種信號(hào)從單片機(jī)的P0.2口輸入。三、剎車控制剎車控制也采用實(shí)時(shí)響應(yīng)方式,當(dāng)系統(tǒng)檢測(cè)到剎車信號(hào)后,立即使單片機(jī)輸出的PWM信號(hào)變?yōu)榱忝}寬,使電子開(kāi)關(guān)斷開(kāi),電機(jī)失電。同時(shí)借助于自行車本身的制動(dòng)系統(tǒng),使自行車停止前進(jìn)。這時(shí)單片機(jī)系統(tǒng)應(yīng)處于等待狀態(tài),剎車信號(hào)消失后,系統(tǒng)恢復(fù)工作，此時(shí)PWM信號(hào)為零脈寬，騎車人需進(jìn)行加速才能繼續(xù)前進(jìn)。這樣做的好處是，可以防止自行車在剎車信號(hào)消失后急速前沖，給騎車人帶來(lái)不安全因素。如圖所示，此信號(hào)從單片機(jī)的P0.3口輸入。四、報(bào)警指示報(bào)警指示電路由四個(gè)發(fā)光二極管和一個(gè)蜂鳴器構(gòu)成，由單片機(jī)的P0.4-P0.7口和P3.3口控制，四個(gè)發(fā)光二極管分別表示電動(dòng)機(jī)過(guò)熱、過(guò)流、蓄電池欠壓和剎車，當(dāng)電動(dòng)機(jī)過(guò)熱、過(guò)流或蓄電池欠壓時(shí)，相應(yīng)的發(fā)光二極管就被點(diǎn)亮，同時(shí)發(fā)出報(bào)警聲提醒騎車人，而當(dāng)剎車信號(hào)出現(xiàn)時(shí)，相應(yīng)的二極管點(diǎn)亮，但不發(fā)出報(bào)警聲。為了方便單片機(jī)控制，發(fā)光二極管正極接+5V電源，負(fù)極通過(guò)限流電阻與單片機(jī)相連，驅(qū)動(dòng)蜂鳴器的三極管采用9015，其電路如圖2-12。第三章系統(tǒng)軟件設(shè)計(jì)基于AT89C51單片機(jī)的需要，本設(shè)計(jì)用匯編語(yǔ)言進(jìn)行編程。由于給直流電動(dòng)機(jī)調(diào)速用的PWM信號(hào)由外電路產(chǎn)生，大大減小了程序的復(fù)雜程度，其程序流程如圖3-1。圖3-1程序主流程圖在本系統(tǒng)控制中，欠壓保護(hù)采用多點(diǎn)檢測(cè)，當(dāng)出現(xiàn)欠壓信號(hào)時(shí)，并不是馬上就切斷主回路，而是在一定時(shí)間內(nèi)連續(xù)檢測(cè)欠壓信號(hào)，如果欠壓信號(hào)保持兩秒鐘，系統(tǒng)將進(jìn)入欠壓保護(hù)報(bào)警程序，如果欠壓信號(hào)持續(xù)不到兩秒鐘，系統(tǒng)就不進(jìn)入保護(hù)報(bào)警程序，繼續(xù)正常工作。過(guò)流、過(guò)熱保護(hù)都采用實(shí)時(shí)響應(yīng)，一旦檢測(cè)到過(guò)流或過(guò)熱保護(hù)，系統(tǒng)就立即進(jìn)入保護(hù)報(bào)警程序。在上述保護(hù)方案中,電流保護(hù)和蓄電池欠壓保護(hù)采用非恢復(fù)性保護(hù),一旦進(jìn)入保護(hù)狀態(tài),就必須等排除故障、重新啟動(dòng)單片機(jī)系統(tǒng)后,才能恢復(fù)工作。而過(guò)熱保護(hù)采用可恢復(fù)性保護(hù),在軟件保護(hù)過(guò)程中,若電動(dòng)機(jī)溫度下降到保護(hù)值以下時(shí),應(yīng)撤消保護(hù),系統(tǒng)恢復(fù)正常工作狀態(tài)。加速、減速控制也采用實(shí)時(shí)響應(yīng)，一旦檢測(cè)到加速或減速信號(hào)，單片機(jī)就相應(yīng)改變X的值，以達(dá)到加速或減速的效果。另外，為了便于騎車人調(diào)速，系統(tǒng)的加速或減速的幅度和騎車人按加速或減速按鈕的時(shí)間成正比，按得越長(zhǎng)，改變的速度值就越大，只要按著加速或減速按鈕，系統(tǒng)就一直執(zhí)行加速或減速程序，直到速度達(dá)到最大值或零。剎車控制也采用實(shí)時(shí)響應(yīng)，一檢測(cè)到剎車信號(hào)，剎車燈亮，并將速度調(diào)到零。因?yàn)槟壳拔覈?guó)在電動(dòng)自行車中采用的無(wú)刷直流電動(dòng)機(jī)都是低轉(zhuǎn)速的，一般為200轉(zhuǎn)/分，并與車輪整合在一起，不經(jīng)過(guò)變速，無(wú)刷直流電動(dòng)機(jī)轉(zhuǎn)子的轉(zhuǎn)速就是車輪的轉(zhuǎn)速，而采用12M晶振的單片機(jī)系統(tǒng)定時(shí)器的最長(zhǎng)定時(shí)只有60多毫秒，在這么短的時(shí)間里，車輪不可能轉(zhuǎn)一周，因此測(cè)速只能采用周期法，即多次中斷定時(shí)，每次中斷設(shè)為15毫秒，測(cè)出車輪轉(zhuǎn)一周所需的中斷次數(shù)，就可以得到車輪每轉(zhuǎn)一周所需的時(shí)間，從而算出車子的行進(jìn)速度，在本程序中暫時(shí)將車輪的周長(zhǎng)定為1米，中斷程序流程圖見(jiàn)圖3-2。圖3-2中斷程序流程圖第四章結(jié)束語(yǔ)電動(dòng)自行車控制器的性能在很大程度上決定了電動(dòng)自行車的整車性能。通過(guò)單片機(jī)AT89C51將各硬件部分有機(jī)地組合起來(lái)，使系統(tǒng)能及時(shí)、有效地檢測(cè)到各種控制信號(hào)并將轉(zhuǎn)換后的信號(hào)反饋給各控制部件，實(shí)現(xiàn)了軟硬件的完美組合。此控制器具有節(jié)能、工作可靠等特點(diǎn)，基本符合了人們對(duì)電動(dòng)自行車控制器的要求。經(jīng)過(guò)這次畢業(yè)設(shè)計(jì)，我覺(jué)得自己學(xué)到了不少東西。學(xué)會(huì)了更好地查閱資料和利用工具書(shū)。當(dāng)在設(shè)計(jì)過(guò)程中需要用一些不曾學(xué)過(guò)的東西時(shí)，就要去有針對(duì)性地查找資料，然后加以吸收利用，以提高自己的應(yīng)用能力，而且還能增長(zhǎng)自己見(jiàn)識(shí)，補(bǔ)充最新的專業(yè)知識(shí)，并且加強(qiáng)了PROTEL軟件的應(yīng)用設(shè)計(jì)，最主要的是，使我對(duì)編程有了一定的提高，我是最怕編程的，因?yàn)樵谝郧皩W(xué)習(xí)中，編程就是我最大的弱點(diǎn)，所以真的很感謝這次畢業(yè)設(shè)計(jì)。同時(shí)在這里，我要感謝我的導(dǎo)師石炳存老師和畢業(yè)設(shè)計(jì)過(guò)程中所有給我真誠(chéng)幫助的老師和同學(xué)。參考文獻(xiàn)：[1]沈卓群,劉電霆,蔣存波。電動(dòng)自行車智能控制器研制[J],桂林工學(xué)院學(xué)報(bào)。2002，4(22):406～408。[2]張毅坤，陳善久，裘雪紅。單片微型計(jì)算機(jī)原理及應(yīng)用[M]，西安電子科技大學(xué)出版社。1998年9月。[3]邵富春。怎樣保護(hù)電動(dòng)機(jī)[M],中國(guó)農(nóng)業(yè)機(jī)械出版社。1984年6月.[4]葉金虎,徐思海,張頡明,崔海大,施民生。無(wú)刷直流電動(dòng)機(jī)[M],科學(xué)出版社。1982年1月[5]邱丹,王東,高振東。直流電機(jī)PWM閉環(huán)調(diào)速系統(tǒng)[J]，青島大學(xué)學(xué)報(bào)。2000，1(15):10～12.[6]韓志榮,黃鄉(xiāng)生,李躍忠。AT89C51單片機(jī)在直流電機(jī)閉環(huán)調(diào)速系統(tǒng)中的應(yīng)用[J],華東地質(zhì)學(xué)院學(xué)報(bào).2002,1(15):70～74。[7]楊素行。模擬電子技術(shù)基礎(chǔ)簡(jiǎn)明教程[M],高等教育出版社.1998年10月.[8]盧靜,陳非凡,張高飛,施涌潮.基于單片機(jī)的無(wú)刷直流電動(dòng)機(jī)控制系統(tǒng)設(shè)計(jì)[J]，北京機(jī)械工業(yè)學(xué)院學(xué)報(bào)。2002,4(17):44～49.[9]王曉明，電動(dòng)機(jī)的單片機(jī)控制，北京航空航天大學(xué)出版社.2002[10]馬家辰，孫玉德，張穎。MCS-51單片機(jī)原理及接口技術(shù)。[11]吳金戌。8051單片機(jī)實(shí)踐與應(yīng)用[M]，清華大學(xué)出版社。ComputerAidedDesignGoodengineeringdesignisnecessarytoguaranteetatapartormechanismfunctionscorrectlyandlastsforareasonablylongtime.Functionalconsiderationsduringdesigninvolve,amongotherthings,weight,strength,thermalproperties,kinematics,anddynamics.Theperformanceofadesigncanbeevaluatedbycomparingitsperformancemeasurementswiththerequiredspecifications.Asimportantassatisfactoryperformanceis,thereareotherareaspartshouldbedesignedeconomically.Thisimpliesthatthefinishedpartshouldbedesignedasclosetothespecificationsaspossible.Ifthefunctionofasupportingmemberofastructurerequiresthemembertowithstand10,000psiofcompressivestress,thendesigningthemembertowithstand30,000psiisunnecessaryandwillprobablybemoreexpensivethantherequireddesign.Engineeringdesign,thereforeshouldaddressfunctionalityandeconomics,Functionalityisdeterminedbyapart’sgeometry,materialproperties,andenvironment.Theeconomicfactorsincludematerials,processingcosts,andmarketingdetails.Asmuchas70%oftheproductioncostsofamanufacturedpartaredeterminedduringtheengineeringdesignprocess.Thismeansthatbythetimetheparthasleftthedesigner’shandsthelargemajorityofitsproductioncostshavebeenestablished.Theyaredefinedimplicitlybythematerials,dimensions,tolerances,surfacefinishes,andotherparameterswhichdetermineprocessingcosts.Therefore,only30%ofthepart’scostissubjecttomoney-savingeffortsduringthemanufacturingplanningstage.This70/30ratioemphasizestheimportantofthedesigncanbeamajorhelpinassuringproperfunctionandreasonableproductioncosts.Computer-aideddesign(CAD)isatermwhichmeansmanythingstomanypeople.Tosome,itmeanscomputer-aideddraftingordrawing.Toothers,itmeanscompute-aidedanalysis.Andtostillothers,itsuggeststotallyautomateddesignwheretheengineerneedspecifyonlythefunctionofapartandthecomputerarrivesatasatisfactoryorevenoptimaldesign.CADisalloftheabove,aimingmostlyforthefastdescriptionthroughtechniquesinartificialintelligence.CAD,however,stillexistsseparatelyineachofthestagesmentioned.ProbablythemostcommonandsimplestCADsystemsarelimitedtoautomateddraftingcapabilities.Moreadvancedsystemscanperformanalysesandevenhelpguidetheengineertotheequationsnecessarytodeterminetheeffectivenessofthedesign.BecauseoftheavailabilityofawidevarietyofCADsystemswithdifferentcharacteristicssuppliedbydifferentvendors,propercommunicationandexchangeofdatabetweenthesesystemshavebecomeasignificantproblem.TheneedforasingleneutralformatforbettercompatibilityispresentlyfilledlargelybytheInitialGraphicsExchangeSpecificaton(IGES).Vendorsneedonlyprovidetranslatorsfortheirownsystemstopreprocessthedataintotheneutralformatintotheirsystem.IGESisusedfortranslationintwodirections(intooroutofasystem)andisalsousedwidelyfortranslationof3-Dlineandsurfacedata.Amorerecentdevelopmentisasolid-model-basedstandardcalledProductDataExchangeSpecification(PDES),whichisbasedonIGES.AlthoughIGESisadequatefromostrequirement,PDEShaslessmemorysize,requireslesstimeforexecution,andislesserrorprone.Becauseoftheexistenceofvariousstandardsinothercountriesaswell,itisexpectedthatinthenearfuturethesestandardswillculminateinaninternationalstandard,calledtheStandardfortheExchangeofProductModelData(STEP).HardwareandSoftwareHardwarevariesagreatdealbetweenCADsystems.MainframeshavelongbeenusedforCADsystems.TherapidincreasesinprocessingspeedshavemademicroandminicomputersviableCADstations.Networksgenerallyareusedsothatdesignscanbestoredcentrallyanddatacanbesharedamongdesigners.Manyinputdevicesareused.CommonI/Odevicesincludekeyboard,mouse,trackball,digitizingpad,joystick,keypad,andlightpens.Outputdevicesaretypicallyscreen,plotter,printer,andharddrivesanddisksforstorage.ThereisawidevarietyofCADsoftwareavailableformainframesengineeringstationsandmicrocomputers.Thepackagesvarytosomedegreeininformationintheformofdrawingexchangefiles.Thesefilescanbeimportedintoothersoftwaretoassistinprogrammingthemachinetool.ElementsofCADSystemsThedesignprocessinaCADsystemconsistsoffourstages,asdescribedbelow.Geometricmodeling.Ingeometricmodeling,aphysicalobjectoranyofitspartsisdescribedmathematicallyoranalytically.Thedesignerfirstconstructsageometricmodelbygivingcommandsthatcreateormodifylines,surfaces,solids,dimensions,andtextthattogetherareandaccurateandcompletetwo-orthree-dimensionalrepresentationoftheobject.Themodelscanbepresentedinthreedifferentways.Inthelinerepresentation(wire-frame;Figure10.ld),alledgesarevisibleassolidlines.Thisimagecanbeambiguous,particularlyforcomplexshapes.However,variouscolorsaregenerallyusedfordifferentpartoftheobject,thusmakingtheobjecteasiervisualize.Inthesurfacemodel,allvisiblesurfaceareshowninthemodel,andinthesolidmodel,allsurfacesareshown,butthedatadescribetheinteriorvolume(Figure10.1e,f)Designanalysisandoptimization.Afterthedesign’sgeometricfeatureshavemayconsistofanalyzingstresses,strains,deflection,vibrations.Thisphasetemperaturedistribution,ortolerance.Varioussophisticatedsoftwarepackagescapableofcomputingthesequantitiesaccuratelyandrapidlyareavailable.Designreviewandevaluation.Animportantdesignstageisreviewandevaluationtocheckforanyinterferencebetweenvariouscomponentsinordertoavoiddifficultiesduringassemblyoruseofthepart,andwhethermovingmembers,suchaslinkages,aregoingtooperateasintended.Softwareisnowavailablewithanimationcapabilitiestoidentifypotentialwithmovingmembersandotherdynamicsituations.Duringthedesignreviewandevaluationstage,thepartispreciselydimensionedandtolerance,asrequiredformanufacturingit.Documentationanddrafting.Aftertheprecedingstageshavebeencompleted,thedesignisreproducedbyautomateddraftingmachinesfordocumentationandreference.Detailandworkingdrawingsarealsodevelopedandprinted.TheCADsystemiscapableofdevelopingdraftingsectionalviewsofthepart,scalingthedrawings,andperformingtransformationtopresentvariousviewofthepart.InCADsystems,muchofthedesignprocesswasformerlycarriedoutonworkstationconnectedtoamainframecomputer,butthetrendhaschangedrapidlytopowerful,high-performance,andmuchlessexpensivestand-alonedesktop32-bitUnixworkstation;64-bitprocessorswithevenbetterperformancearealsobecomingavailable.TheDesignProcessBeforedelvingintoCAD,itisimportanttounderstandthedesignprocessitself.Computertechniquesarenomorevaluablethanthetheoryonwhichtheyarebased.Afterashortdiscussionofdesigningeneral,wewillexplorehowthecomputercanhelpwitheachofthedesignstages.Shigleydefinesthedesignprocessasaniterativeprocedureconsistingofsixphase:RecognitionofneedDefinitionofproblemSynthesisAnalysisandoptimizationEvaluationPresentationThefirststep,recognitionofneed,arisesfromanidentifiedproblem.Suppose,forexample,thatanew,moreefficientjetengineisrequiredbecauseofafuelshortage.Step2,definitionoftheproblemismorespecific.Definingthespecificsofthejetengineinvolvesknowingthethrust,horsepower,allowableweight,etc.Someofthesespecificationsareconstraints;I.e.,theyarerequirementsthatmustbemetforthedesigntobefeasible.Thejetengineweightlimitmaybeoneconstraintontheavailableliftoftheplanewings.Amaximumweight,then,wouldbeaconstraint.Constraintsareusuallyexpressedasamaximumorminimumvalueorrageofvalues.Otherspecification,however,aretermedcriteria,i.e.,measuresofthegoodnessorqualityofthedesign.Criteriaareusedtomeasureadesignandcomparedesignsagainstoneanother,asoccursduringtheoptimizationstage.Onecriterionofthejetenginemaybegallonsoffuelburnedperhourorpermileoftravel.Criteriahavenomaximumorminimumlimitsonvalues.Asatisfactorydesignisoneinwhichalltheconstraintsaremet.Thisbestdesign,Iadditiontomeetingtheconstraints,willhavethebestcombinationofcriteriavalues.Selectionofconstraintsandcriteriaisanintegralpartofstep2,definitionoftheproblem.Followingdefinitionoftheproblem,thenextthreesteps(synthesis,analysis/optimization,andevaluation)areiterative.Synthesisandanalysisareperformedinconjunctionwithoneanother.Severaltypesofproblemscanariseduringthedesignprocess.Synthesisrequiresdeterminingtheotakestheformofengineeringdrawingsincludinggeometry,tolerances,materialtypes,andcomponentparnumbers.Analysismayrangefromasimpleestheticevaluationtothesolutionofasetofcomplexdifferentialequationswhichdescribetheperformanceofthepartorassembly.Theresultsofanalysescanbeexpressedintabularorgraphicalform.Itisthejobofthedesignertoevaluatetheanalysisdataandtoperformanyredesign.Evaluationsalsoatypeofanalysis,butusuallyrequiresanexpensiveprototypeandracksofinstrumentation.Thedesignprocesscanbeverycostlyandinvolvemanypeople.Designcostmaybelowed,however,byreducingthenumberofpeopleandtheprototypingprocessitself.AnalysisTheanalysisisthecornerstoneofCAD.Theresultsgeneratedbyanalysismodulesareusedbytheengineertodeterminethefeasibilityofadesignortooptimizeorredesigntheobject.Fundamentaltoanalysisisdevelopedtoaccuratelypredicttheperformancebasedonthedesignvariablevalues.Typically,sophisticatedanalysisprogramsaretheperformancemodelsofthedesign.Theuserdoesnotneedtoformulateequationswhichdescribetheperformanceorfunctionality.Whattheusermustdoinsteadistomodeltheobjectgeometryinanappropriateformat.Usuallytieengineerwhoisdesigningacommonlyanalyzedpartorassemblycanpurchaseanalysissoftwaretoevaluatethedesign.Itisonlyinthecaseofanunusualdesignorperformancerequirement,whereoff-the-shelfsoftwareisnotavailable,thattheengineermustformulateauniquemodel.Inthiscase,theengineerwillusuallyderiveamathematicalmodelintheformofequationsusinghelawsofphysicsandwriteaprogramtoreadthedesigndescriptionandcalculateteperformanceparameters.Thesecommonlyavailableanalysismodulesreadthedesigndescriptionandgenerateperformanceresultintheformofnumbers,graphs,charts,etc.AnExampleofUsingCADCAD,normallyusedinengineeringdepartments,hasdrasticallychangedthesedepartments.Drawingusedtobemadeonpaperwithpencilorpenanddrawinginstruments.Theywerethencopied,andthecopiesweresenttothefloorforproduction.Theoriginalswerestoredinlargedrawers.Evenasmallenterprisecouldhavethousandsoflargeblueprintsonfile.Ifchangeswerenecessary,theengineerwouldgettheoriginaloutofthefiledrawer,maketheneedforallofthephysicalstorageofprints.Thecomputeralsoallowedforrapidandeasyprintmodifications.Theengineerordesignerfirstdrawsthepartonthescreenthispartdrawingistheactualpartgeometry.Thesizesandlocationareallcorrectsothattheinformationcanbeusedlatertocreateaprogramtomachinethepart.Theengineerordesignerfirstdrawsthepartonthescreen.Thispartdrawingistheactualpartgeometry.Thesizesandlocationsareallcorrectsothattheinformationcanbeusedlatertocreateaprogramtomachinethepart.Thedesignermustworkcloselywiththemanufacturingpeopletoestablishsomestandardsfordesign.CADallowsdifferentlayers(orlevels)tobecreated.Thisallowsthedesignertoputdifferentpotionsofthepartgeometryondifferentlayers.Forexample,imagineasimplepartthathasa1/2-inchslotmilledinitandfourholesdrilledthroughit.Thedesignerwouldputtheslotononelayerofthedrawingandtheholesonanotherlayer.Thiswillallowothersoftwaretotakethepartgeometryformeachlayerandassigndifferenttoolstoit.Thinkofdifferentlayersasdifferentmachiningoperationthatwouldhavedifferenttoolassignedtothem.Layersareliketransparency.Ifweputallofthetotaltransparenciesontopofeachother,weseethetotalpart.Butwecanstilltakeanyonetransparencyandisolatesomeofthepartgeometry.TheCADsystemwillprinttheblueprintsoitappearsthereisonlyonelayer,orindividuallayerscanbeprinted.Thedesigneralsodimensionsthepart.Thisisquiteautomatic.Thedesignerchooseswherehe/shewantsdimensionsplacedandthecomputerplacestheactualdimensions.Dimensionswouldbeonadifferentlayerthanpartgeometry.Thecomputerallowsdesignstobeviewedandtestedbeforetheactualpartisevenmanufactured.Thepartcanbetestedmakesureitfitswithanymatingpars.CADsystemcancheckforinterferenceofparts,whichcansavealotofwastedmachininganddevelopmenttime.CADsystemscanstress-testparttoseeiftheywillmeetthestrengthrequirementsoftheapplication.ThegraphicsabilitiesofCADsystemalsoallow3-Dviewingofpartfromanyangle.IntegratedCADTheemphasisofthechapterisintegratedCAD/CAM.Theintegrationaspectisaccomplishedwhenthedesignandanalysismodulesareunitedintoonepackage.Thedesigngeometryenteredbythedesignercanbeusedbytheanalysisprogramsandbythemanufacturing,inspection,inventory,andotheraspectsoftheproductliftcycle.Themanifestationofintegratingsoftwareisrecognizedwhentheusercansitdownatacomputerterminal,designapart,viewitonthescreen,analyzeitfordesignrequirements,andhittheproverbialmanufacturingbuttonthekeyboardtohavethepartautomaticallymanufactured,inspected,anddelivered.Variousstagesofintegrationdoexist,butnoneisascompleteastheexamplejustmentioned.Integrationimpliesautomation.AutomationimpliesthatthehardwareandsoftwarecancreateaCADdatabaseanduseittoanalyzeandmanufacturetheparttotallyautomatically,withlittleornohumanintervention.Thequestionastowhetherhumaninterventionisadvisableisstillopen.Certainlyhumanintelligenceisvaluableindevelopingadesigningeometryandfunctionality,recognizingcertainpatternsandshortcomingsofproducts,andformulatingmanufacturingplans.Ithasbeensuggestedthatartificialintelligence(AI)techniquescansubstituteformuchofthehumandesign/manufacturinginput.AIresearchhashadsuccessintheareasofpatternrecognition,planning,naturallanguageunderstanding,roboticcontrol,faultdiagnosis,andotherapplications.ThemostwellrecognizeareaofAIisthedevelopmentofexpertsystem.Expertsystemssimulatehumanexpertisebystoringaknowledgebaseofdataaboutaspecificdomain.ThearchitectureofanexpertsystemisshowninFigure10.2.Theknowledgebasecontainsknowledgeaboutaspecificproblemdomainandfactsstatingtheproblem.Theinferenceengineistheprogramcontrolwhichsearchestefactsabouttheproblemtosatisfytheknowledgebaseadabovetheproblem計(jì)算機(jī)輔助設(shè)計(jì)一個(gè)好的機(jī)械設(shè)計(jì)產(chǎn)品必須保證產(chǎn)品的部分或全部功能在產(chǎn)品壽命中能夠正確有效地實(shí)現(xiàn)。在設(shè)計(jì)中產(chǎn)品功能的研究包括：重力、強(qiáng)度、熱、溫度特性、運(yùn)動(dòng)學(xué)和動(dòng)力學(xué)。評(píng)價(jià)設(shè)計(jì)的好壞與否可以通過(guò)比較產(chǎn)品的實(shí)際性能與設(shè)計(jì)要求的差距來(lái)衡量。設(shè)計(jì)除了功能達(dá)到設(shè)計(jì)要求之外，其它方面的實(shí)際同樣也十分重要。比如說(shuō)經(jīng)濟(jì)性方面的要求。這就是說(shuō)最終的產(chǎn)品要近可能地接近設(shè)計(jì)要求。如果要求支撐設(shè)計(jì)能承受1000N/min的能力，然而設(shè)計(jì)成能承受2000N/min，則沒(méi)有必要也不經(jīng)濟(jì)。因此機(jī)械設(shè)計(jì)必須處理好產(chǎn)品的功能與其經(jīng)濟(jì)性之間的矛盾。產(chǎn)品的性能受零部件的結(jié)構(gòu)、材料屬性和人機(jī)環(huán)境的影響；產(chǎn)品的經(jīng)濟(jì)性則和材料的成本以及市場(chǎng)因素有關(guān)。在機(jī)械設(shè)計(jì)過(guò)程中70%的制造成本已經(jīng)決定了。這就是說(shuō)設(shè)計(jì)者把產(chǎn)品交給制造之前，絕大部分主要的成本已經(jīng)決定。比如：材料尺寸、公差、表賣弄粗糙度及過(guò)程成本的其它參數(shù)。因此，在加工過(guò)程中，我們?cè)谥圃爝^(guò)程中再努力也只能減少%30的花費(fèi)。這個(gè)比例說(shuō)明設(shè)計(jì)過(guò)程起著置關(guān)重要的作用。我們應(yīng)該清楚計(jì)算機(jī)能夠幫上很大的忙。計(jì)算機(jī)輔助設(shè)計(jì)對(duì)不同的人意味著不同的意思。對(duì)一些人來(lái)說(shuō)，它意味著計(jì)算機(jī)輔助繪圖和草繪，對(duì)另外一些人來(lái)說(shuō)，他則意味著完全自動(dòng)化設(shè)計(jì)，設(shè)計(jì)者只要規(guī)定設(shè)計(jì)的功能，則計(jì)算機(jī)能設(shè)計(jì)出滿足要求的產(chǎn)品，甚至經(jīng)過(guò)優(yōu)化的設(shè)計(jì)。以上則是計(jì)算機(jī)輔助設(shè)計(jì)。他的目標(biāo)就是通過(guò)人類的智慧實(shí)現(xiàn)后面敘述的一種情形。計(jì)算機(jī)輔助設(shè)計(jì)仍停留在計(jì)算機(jī)輔助繪圖階段。大多數(shù)簡(jiǎn)單的CAD只能進(jìn)行自動(dòng)草繪功能。更高級(jí)的系統(tǒng)呢功能進(jìn)行分析引導(dǎo)工程師得到必須平衡的關(guān)系。因?yàn)椴煌馁u主提供具有不同特點(diǎn)的計(jì)算機(jī)輔助設(shè)計(jì)系統(tǒng)，這些系統(tǒng)之間具有各自不同的數(shù)據(jù)標(biāo)準(zhǔn)。他們之間的交流和數(shù)據(jù)轉(zhuǎn)化變得非常有意義。IGES在不同系統(tǒng)之間數(shù)據(jù)格式轉(zhuǎn)換中扮演了中間者的角色。不同軟件廠商只要提供與IGES格式相互轉(zhuǎn)換的模塊系統(tǒng)，各種計(jì)算機(jī)輔助設(shè)計(jì)軟件能導(dǎo)入和導(dǎo)出IGES格式的文件，同時(shí)這種格式的文件在3D圖形轉(zhuǎn)換種也有根廣泛的應(yīng)用。目前一種基于IGES格式的實(shí)體建模技術(shù)的數(shù)據(jù)格式（PDES）也得到很大的發(fā)展。這種格式的文件占用系統(tǒng)空間小、速度快、可靠性高。由于國(guó)外也有各種不同的標(biāo)準(zhǔn)存在，預(yù)計(jì)不久這些標(biāo)準(zhǔn)將導(dǎo)致一個(gè)國(guó)際標(biāo)準(zhǔn)規(guī)格，叫產(chǎn)品模型數(shù)據(jù)(STEP)的交換的標(biāo)準(zhǔn)。硬件和軟件硬件在計(jì)算機(jī)輔助設(shè)計(jì)系統(tǒng)之間存在很大的差別。服務(wù)器早就用于計(jì)算機(jī)輔助設(shè)計(jì)系統(tǒng)。處理速度迅速增加的微型和小型計(jì)算機(jī)也可以進(jìn)行的計(jì)算機(jī)輔助設(shè)計(jì)系統(tǒng)的運(yùn)行。網(wǎng)絡(luò)一般被使用以便設(shè)計(jì)可以被中心儲(chǔ)存，數(shù)據(jù)可以被分給設(shè)計(jì)者。很多輸入裝置使用的非常廣泛。普通I/O設(shè)備包括：鍵盤(pán)，鼠標(biāo)，跟蹤球，數(shù)子化儀，控制桿，輔助鍵盤(pán)和光筆數(shù)字化儀。典型的輸出裝置通常是屏幕，繪圖儀，打印機(jī)、移動(dòng)硬盤(pán)和軟盤(pán)。有多種計(jì)算機(jī)輔助設(shè)計(jì)軟件提供給工作站和微型計(jì)算機(jī)。數(shù)據(jù)包在某種程度上以繪圖信息形式的交換文件變化。這些文件可以被輸入到其他軟件中幫助可編程的機(jī)床。計(jì)算機(jī)輔助設(shè)計(jì)系統(tǒng)的要素計(jì)算機(jī)輔助設(shè)計(jì)系統(tǒng)的設(shè)計(jì)過(guò)程由四級(jí)組成，如下描述。幾何學(xué)模型化。在幾何學(xué)模型化過(guò)程中，將一個(gè)物體或者它的任何部分進(jìn)行分析后用數(shù)字描述。首先設(shè)計(jì)者給出命令建立或者修改能夠完成二維或三維的線條、表面、實(shí)體、尺寸和正文構(gòu)造幾何學(xué)模型。幾何學(xué)模型可以用三種不同的方式呈現(xiàn)。如下圖(線框內(nèi)；圖10.ld)，全部邊緣都象固體的線一樣可見(jiàn)。這幅圖像可能是含糊的，特別是復(fù)雜的形狀。不過(guò)，各種各樣的顏色一般用于物體的不同的部分，因此使物體更容易想象。在表面模型里，全部可見(jiàn)的表面被用模型顯示，并且在實(shí)體模型里，全部表面被顯示，但是內(nèi)部以數(shù)據(jù)的形式描述(數(shù)字10.1e，f)設(shè)計(jì)分析和最優(yōu)化。設(shè)計(jì)幾何學(xué)特征有可能由分析壓力、疲勞、撓度、振動(dòng)組成。這階段溫度分布或者容忍。各種各樣復(fù)雜軟件包能計(jì)算出質(zhì)量的準(zhǔn)確并且快速的變化。設(shè)計(jì)評(píng)論和評(píng)估。設(shè)計(jì)過(guò)程忠一個(gè)重要的設(shè)計(jì)階段是檢查在各種各樣的組成部分之間是否存在任何干涉，是否有自由度，例如將要作為運(yùn)動(dòng)構(gòu)件的連桿。計(jì)算機(jī)軟件能利用動(dòng)畫(huà)模擬運(yùn)動(dòng)的構(gòu)件及其它運(yùn)動(dòng)狀態(tài)。在設(shè)計(jì)過(guò)程的評(píng)論和評(píng)估階段，零件已經(jīng)具有制造需要的準(zhǔn)確尺寸和公差。文檔編制和草繪。在那些先前階段完成之后，那些設(shè)計(jì)被自動(dòng)化草繪儀復(fù)制作為文檔編制和參考用，細(xì)節(jié)和圖紙也被沖印。計(jì)算機(jī)輔助設(shè)計(jì)系統(tǒng)能繪制零件的剖視圖、局部視圖，并且能提取零件的各種各樣的視圖。以前