英要………………2第一言電動(dòng)自行車(chē)的意義及發(fā)展?fàn)?自行車(chē)的歷史背影及意 電動(dòng)自行車(chē)的優(yōu)點(diǎn) 電動(dòng)自行車(chē)的發(fā)展前 第二章控制器系統(tǒng)的分 智能控制器的系統(tǒng)框圖 系統(tǒng)主要硬件介紹 無(wú)刷直流電 MC14585B和 系統(tǒng)具體實(shí)現(xiàn)方法 無(wú)刷直流電的調(diào)速 測(cè)速電 速度預(yù)置與顯 電機(jī)驅(qū)動(dòng)電 無(wú)刷直流電及控制器的保護(hù) 第三章系統(tǒng)軟件設(shè) 第四章結(jié)束 參考文 附錄 場(chǎng)，電動(dòng)自行車(chē)產(chǎn)業(yè)有著非常廣闊的應(yīng)用前景，因此發(fā)展電動(dòng)自控制器的設(shè)計(jì)方案。該系統(tǒng)包括控制方案、速度測(cè)量和顯示方案、剎車(chē)控制方案和電路保護(hù)方案等。本設(shè)計(jì)主要是以單片機(jī)為，特別：電動(dòng)自行車(chē)；智能控制；脈沖寬度調(diào)制；單片機(jī)；電機(jī)保Electricbicycleforportableandflexible,energy-savingenvironmentalprotection,moderateinpriceandarewidelyusedinpeople,anidealvehicleforthepeopleinthetravel.Atthesametime,Chinahasahugemarketofbicycle,electricbicycleindustryhasaverypplicationprospectsinChina,andsothedevelopmentofelectricbicyclehasagoodsocialsignificanceThispaperintroducesadesignprogramofinligentcontroloftheelectronicbicyclewhichisbasedonthesinglechipcomputersystem.ItisderivedbynobrushDCmotor.Thissystemintroducesspeedcontrolproject,speedmeasureanddisplayproject,brakecontrolproject,electrocircuitprotectionproject.Thisdesignisbasedonthesinglechipcomputer,itsspecialtiesadoptcombininghardwarewithsoftwareforimprovingcredibilityandsecurity.：electricbicycle；inligentcontrol；;singlechipcomputer;electrocircuitprotection第一 引車(chē)人太多不想擠摩托車(chē)太路段又禁駛而電動(dòng)自行車(chē)是最適合他們的產(chǎn)品。國(guó)各大城市的市場(chǎng)需求，有高達(dá)76%的市民有將電動(dòng)自行車(chē)作為代步交通工具的電動(dòng)自行車(chē)的意義及發(fā)展?fàn)?、無(wú)污染：電動(dòng)自行車(chē)是以蓄電池發(fā)出的電能作為驅(qū)動(dòng)能源，以電作為動(dòng)力，2、噪音、振動(dòng)?。弘妱?dòng)自行車(chē)是由電驅(qū)動(dòng)的，電在運(yùn)行中產(chǎn)生的噪音比較320公里，行駛安全：摩托車(chē)、燃油助動(dòng)車(chē)的速度快，在機(jī)動(dòng)車(chē)上行駛，事故率較高；而電動(dòng)自行車(chē)，國(guó)家強(qiáng)制性規(guī)定（GB17761-1999）其速度20Km/h430%70%以上。5、結(jié)構(gòu)簡(jiǎn)單、輕便，易、維修：電動(dòng)自行車(chē)一般是有蓄電池、控制板、電機(jī)和車(chē)身組成；蓄電池用的是免的，電機(jī)的故障率較低，基本上不要，控制行車(chē)代替?zhèn)鹘y(tǒng)自行車(chē)將是一個(gè)的市場(chǎng)需求趨勢(shì)。超過(guò)了100家，預(yù)計(jì)今年電動(dòng)自行車(chē)產(chǎn)量可達(dá)200到250萬(wàn)輛，到2010年產(chǎn)400車(chē)中廣泛使用的鉛酸電池不長(zhǎng)，造成的二次污染比較嚴(yán)重，鉛的毒性較大，所以對(duì)其污染問(wèn)題我們決不能掉以輕心。據(jù)有關(guān)資料顯示，我國(guó)每年大約有5000萬(wàn)支廢加之廢電池回收再生技術(shù)，甚至有亂棄廢電池等行為，直接導(dǎo)致了環(huán)境污染。電電第二章基本設(shè)計(jì)思本設(shè)計(jì)的基本思想是以89C51為器件，從而控制電動(dòng)自行車(chē)的行駛。以AT89C51為所組成的閉環(huán)控制系統(tǒng),能夠?qū)崿F(xiàn)速度顯示,速度控制，采用改變電制信號(hào)進(jìn)行調(diào)速的場(chǎng)合,比較便于實(shí)現(xiàn)而且調(diào)整性能良好的是脈沖寬度調(diào)制()技2－1產(chǎn)產(chǎn)生電電電路保顯顯示模模調(diào)速模模調(diào)速模系統(tǒng)主要硬件介無(wú)刷直流電無(wú)刷直流電是隨著電子技術(shù)的迅速發(fā)展而發(fā)展起來(lái)的一種新型直流電。它是現(xiàn)代科學(xué)技術(shù)和軍事裝備中重要的機(jī)電元件之一無(wú)刷直流電是以法拉第的無(wú)刷直流電的最大特點(diǎn)就是沒(méi)有換向器和電刷組成的機(jī)械接觸機(jī)構(gòu)另外，無(wú)刷直流電是由電本體（帶有電樞繞組的定子和永磁轉(zhuǎn)子、轉(zhuǎn)子位置32-2

圖2-2無(wú)刷直流電的方框原理無(wú)刷直流電是在有刷直流電的基礎(chǔ)上發(fā)展起來(lái)的就它們發(fā)生的電得在某一磁極下導(dǎo)體中的電流方向始終保持不變這就是無(wú)刷直流電的無(wú)接觸式圖2-3無(wú)刷直流電換向線(xiàn)三．無(wú)刷直流電的運(yùn)行特UEIacpracp

（2-式 U——電源電壓（伏；（安；racp⊿U——功率晶體管飽和管壓降（伏2⊿UEKe

（2-rnIUU（2-rn快起動(dòng)，并能帶負(fù)載直接起動(dòng)。隨著轉(zhuǎn)子的加速，反電勢(shì)E增加，電磁轉(zhuǎn)矩降低，加2-4AT89C51是由Atmel公司生產(chǎn)的高性能八位單片機(jī)，它具有功能強(qiáng)、體積一.AT89C51AT89C51是一種低損耗、高性能、CMOS八位微處理器，片內(nèi)有4k字節(jié)的可重復(fù)編程、快速擦除快速寫(xiě)入程序的器，能重復(fù)寫(xiě)入/擦除1000次，數(shù)據(jù)保存時(shí)間為十年。它與MCS-51系列單片機(jī)在指令系統(tǒng)和引腳上完全兼容，不僅可完全代替二.AT89C51AT89C51單片機(jī)為40引腳見(jiàn)圖2-5。其40個(gè)引腳中有2個(gè)專(zhuān)門(mén)用于主電源的引腳，2個(gè)外接晶體的引腳，4個(gè)控制或與其他電源復(fù)用的引腳，以及32條輸入輸I/O圖2-5AT89C51管腳MC14585B一MC14585B是一個(gè)16腳的4位比較器，它有8個(gè)比較輸入端Comparing表 MC14585B的真值 二CD4040B是一個(gè)16腳的12位計(jì)數(shù)器，可作分頻器使用使用，也可制作電子每進(jìn)1位上升1ｍV，電路二進(jìn)制位0～11位以電阻最小。如第11位50ｋΩ、第系統(tǒng)具體實(shí)現(xiàn)方圖2-8是以AT89C51單片機(jī)為的系統(tǒng)電路原理圖。其中，P0.0-P0.3口分別作為電過(guò)流、過(guò)熱、電池欠壓和剎車(chē)信號(hào)的輸，P0.4-P0.7口分別作為電輸；P3.3口作為信號(hào)輸出口；P3.4和P3.5口作為速度給定口；ALE口作為 9999過(guò)過(guò)過(guò)過(guò)欠剎過(guò)過(guò)流欠壓剎車(chē)2-8無(wú)刷直流電的調(diào)便于實(shí)現(xiàn)而且調(diào)整性能良好的是脈沖寬度調(diào)制()技術(shù)。由于定寬調(diào)頻法和調(diào)寬的脈沖信號(hào)的高電平寬度變化,控制電機(jī)在一個(gè)脈沖周期內(nèi)的通斷比例,從而實(shí)現(xiàn)響系統(tǒng)其它功能的實(shí)現(xiàn)以及系統(tǒng)的可靠性。在本設(shè)計(jì)中采用三片通用數(shù)字產(chǎn)生波的頻率太高時(shí),對(duì)直流電機(jī)驅(qū)動(dòng)的功率管要求太高,太低時(shí)產(chǎn)生電磁噪聲較大。經(jīng)綜合分析,本系統(tǒng)采用兩片4位數(shù)值比較器4585和一片12位串行計(jì)數(shù)器4040組成了信號(hào)發(fā)生電路兩片比較器的A組接4040計(jì)數(shù)輸出Q1～Q8端,B組接單片微機(jī)的P1端口改變P1端口的輸出值,可使信號(hào)的占空比產(chǎn)生變化,進(jìn)行調(diào)速控制。時(shí),ALE脈沖的頻率為2M，經(jīng)Q1～Q8的256分頻,產(chǎn)生的波形的頻率為7.8kHz,適計(jì)數(shù)器4040每來(lái)1個(gè)脈沖,其輸出Q1～Q8加1,當(dāng)計(jì)數(shù)值小于或等于單片機(jī)P1端口輸出值X時(shí),U2的(A>B)輸出端保持為低電平,當(dāng)計(jì)數(shù)值大于X時(shí)U2的(A>B)輸出端低電平,這樣,在U2的(A>B)端得到的信號(hào),其占空比為(255-X/255)×100%,改變X值可改變信號(hào)的占空比,進(jìn)行直流電機(jī)的轉(zhuǎn)速控制，如圖3-6。由于單片機(jī)上電復(fù)位時(shí)P1端口輸出全“1”,4585的B組與P1P0端口輸出X按一定規(guī)律減少,降速時(shí)按一定規(guī)律增大。 AD6個(gè)端口作它用，并有利于剎車(chē)后無(wú)刷直流電的斷電處理。如圖2-9所示為波產(chǎn)生電路：L7L7Z5A2(A>B)IN(A<B)IN12345678+51614B3 12(A11B010A09B1 Z6Z5Z4Z3Q312345678+516151413Q8NetLabel1211 10 9Q1 P17MC14585CD4040L3 Z3 8+51615A314B313(A12(A<B)OUT11B010A09B19RD PSENMC14585 圖2-9產(chǎn)生電待測(cè)信號(hào)經(jīng)預(yù)處理電路后加至單片機(jī)的P3.2（INT0）引腳可為單片機(jī)測(cè)量信號(hào)周期提供有效的輸入信號(hào)。單片機(jī)通過(guò)檢測(cè)P3.2引腳電平來(lái)決定是否啟動(dòng)測(cè)量周期程序。當(dāng)該引腳為高電平時(shí)系統(tǒng)處于等待狀態(tài)，要一直到該引腳出現(xiàn)低電平時(shí)才開(kāi) 首先將零賦給TH0、TL0兩個(gè)寄存器，以將定時(shí)器T0的運(yùn)行控制位TR0置位，同時(shí)也將ET0置位以允許定時(shí)器T0中斷。然后再判斷P3.2引腳是否還當(dāng)其不是低電平時(shí)再等待。一旦出現(xiàn)低電平，則立即復(fù)位TR0以終止定時(shí)器，以結(jié)束測(cè)周期程序。測(cè)周期過(guò)程中可能會(huì)發(fā)生定時(shí)器T0的中斷，每發(fā)生一次中斷則將R0寄存器加一，因此R0實(shí)際上是周期值的高字節(jié)。測(cè)出的周期值在R0、TH0、TL0μｓ，因此在相除轉(zhuǎn)換時(shí)應(yīng)將被除數(shù)擴(kuò)大

2-80-6HzP3.2,預(yù)置速度由按鍵S5、S6輸入,進(jìn)控制,單片機(jī)P3.4，P3.5別接升速按鈕S5和降速按鈕S6。當(dāng)S5鍵按下時(shí),將送到P1口的數(shù)據(jù)N減1以增大號(hào)的占空比;當(dāng)S6按下時(shí),將N加1以減少信號(hào)的占空比。2-10AT89C51P2.0～P2.7a～gdpLEDLEDP2P211000000，0。LED（即要顯示的段碼的控制）P2LEDP3PNP b a162-10圖2-11是利用開(kāi)關(guān)管對(duì)直流電進(jìn)行調(diào)速控制的原理圖。在圖中，當(dāng)開(kāi)關(guān)管MOSFET的柵極輸入高電平時(shí)，開(kāi)關(guān)管導(dǎo)通，直流電電樞繞組兩端有電壓Vs。當(dāng)開(kāi)關(guān)管柵極輸入變?yōu)榈碗娖街?，開(kāi)關(guān)管截止，電電樞電壓兩端電壓0V。電樞電流通過(guò)續(xù)流二極管續(xù)流，即當(dāng)脈沖信號(hào)處于高電平時(shí)，使開(kāi)關(guān)閉合，MOSFET-圖2-11 由2-11圖可知：電 Uton

s

ton

為占空比。改變?chǔ)眩?Us無(wú)刷直流電及控制器的保2-12R4R4R5R6R7vR5R3R3R1R5R3R5R5R3R3R3R3R31 37 36 35 34 33 32 voice312 21 22 23 24 25 26 27 28 116RD PSEN2805圖2- 保護(hù)電護(hù)來(lái)實(shí)現(xiàn)），信號(hào),單片機(jī)將進(jìn)入保護(hù)方式，令單片機(jī)輸出的信號(hào)變?yōu)榱忝}寬，使電機(jī)失電P0.0P0.1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)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)程序，繼續(xù)正常工作。如圖所P0.2剎車(chē)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(chē)信號(hào)后,立即使單片機(jī)輸出的信號(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(chē)本身的制動(dòng)系統(tǒng),使自行車(chē)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(chē)信號(hào)后,系P0.3四、指P0.4-P0.7口和過(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)出聲提醒90152-12。第三章開(kāi)YP3.4是否為NYP3.5是否為NYP0.0是否為NP0.1是否為YNP0.2是否為YNP0.3是否為開(kāi)YP3.4是否為NYP3.5是否為NYP0.0是否為NP0.1是否為YNP0.2是否為YNP0.3是否為YN指示剎車(chē)操操欠壓操加速操操初始結(jié)過(guò)熱操過(guò)流操圖3- 程序主進(jìn)入欠壓保護(hù)就立即進(jìn)入保護(hù)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)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)加速控制也采用實(shí)時(shí)響應(yīng)，一旦檢測(cè)到加速或信號(hào)，單片機(jī)就相應(yīng)改變X的值，以達(dá)到加速或的效果。另外，為了便于騎車(chē)人調(diào)速，系統(tǒng)的加速或的幅度和騎車(chē)人按加速或按鈕的時(shí)間成正比，按得越長(zhǎng)，改變的速度值就越大，只要按著加速或按鈕，系統(tǒng)就一直執(zhí)行加速或程序，直到速度達(dá)到最大值或零。剎車(chē)控制也采用實(shí)時(shí)響應(yīng)，一檢轉(zhuǎn)/分，并與車(chē)輪整合在一起，不經(jīng)過(guò)變速，無(wú)刷直流電轉(zhuǎn)子的轉(zhuǎn)速就是車(chē)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15YNYNR3值賦重啟定定時(shí)中間，從而算出車(chē)子的行進(jìn)YNYNR3值賦重啟定定時(shí)中圖3- 中斷程序第四 結(jié)束機(jī)AT89C51將各硬件部分有機(jī)地組合起來(lái)，使系統(tǒng)、有效地檢測(cè)到各種控制然后加以吸收利用，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)充的專(zhuān)業(yè)知識(shí)，并且加強(qiáng)了PRO 感謝這次畢業(yè)設(shè)計(jì)。同時(shí)在這里，我要感謝導(dǎo)師老師和畢業(yè)設(shè)計(jì)過(guò)程中所有給誠(chéng)幫助的老師和同學(xué)。[1],,電動(dòng)自行車(chē)智能控制器研制[J],桂林工學(xué)院學(xué)報(bào)408[2]坤，，。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)。19989[3]。怎樣保護(hù)電[M],中國(guó)農(nóng)業(yè)機(jī)械。1984年6月[4],,,崔海大,施民生。無(wú)刷直流電[M],科學(xué)。1982年1[5],,高振東。直流電機(jī)閉環(huán)調(diào)速系統(tǒng)[J]，青島大學(xué)學(xué)報(bào)。[6],,。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[7]楊素行。模擬電子技術(shù)基礎(chǔ)簡(jiǎn)明[M],高等教育.1998年10月，[8],陳非凡,,施涌潮.基于單片機(jī)的無(wú)刷直流電控制系統(tǒng)設(shè)計(jì)[J]機(jī)械工業(yè)，[9]，電的單片機(jī)控制，航空航天大學(xué)[10]，，。MCS-51單片機(jī)原理及接術(shù)[11]。8051單片機(jī)實(shí)踐與應(yīng)用[M]，ComputerAidedGoodengineeringdesignisnecessarytoguaranteetatapartormechanismfunctionscorrectlyandlastsforareasonablylongtime.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)isatermwhi eansmanythingstomanypeople.Tosome,itmeanscomputer-aideddraftingordrawing.Toothers,itmeanscompute-aidedysis.Andtostillothers,itsuggeststotallyautomateddesignwheretheengineerneedspecifyonlythefunctionofapartandthecomputerarrivesatasatisfactoryorevenoptimaldesign.CADisalloftheabove,aimingmostlyforthefastdescriptionthroughtechniquesinartificialin ligence.CAD,however,stillexistssepara yineachofthestagesmentioned.ProbablythemostcommonandsimplestCADsystemsarelimitedtoautomateddraftingcapabilities.MoreadvancedsystemscanperformysesandhelpguidetheengineertotheequationsnecessarytodeterminetheeffectivenessoftheBecauseoftheavailabilityofawidevarietyofCADsystemswithdifferentcharacteristicsdbydifferentvendors,propercommunicationandexchangeofdatabetweenthesesystemshave easignificantproblem.TheneedforasingleneutralformatforbettercompatibilityispresentlyfilledlargelybytheInitialGraphicsExchangeSpecificaton(IGES).Vendorsneedonlyprovidetranslatorsfortheirownsystemstopreprocessthedataintotheneutralformatintotheirsystem.IGESisusedfortranslationintwodirections(intooroutofasystem)andisalsousedwidelyfortranslationof3-Dlineandsurfacedata.Amorerecentdevelopmentisasolid-model-basedstandardcalledProductDataExchangeSpecification(PDES),whichisbasedonIGES.AlthoughIGESisadequatefromostrequirement,PDEShaslessmemorysize,requireslesstimeforexecution,andislesserrorprone.Becauseoftheexistenceofvariousstandardsinothercountriesaswell,itisexpectedthatinthenearfuturethesestandardswillculminateinaninternationalstandard,calledtheStandardfortheExchangeofProductModelData(STEP).HardwareandHardwarevariesagreatdealbetweenCADsystems.MainframeshavelongbeenusedforCADsystems.TherapidincreasesinprocessingspeedshavemademicroandputersviableCADstations.Networksgenerallyareusedsothatdesignscanbestoredcentrallyanddatacanbesharedamongdesigners.Manyinputdevicesareused.CommonI/Odevicesincludekeyboard,mouse,trackball,digitizingpad,joystick,keypad,andlightpens.Outputdevicesaretypicallyscreen,plotter,printer,andharddrivesanddisksforstorage.ThereisawidevarietyofCADsoftwareavailableformainframesengineeringstationsand puters.Thepackagesvarytosomedegreeininformationintheformofdrawingexchangefiles.Thesefilescanbeimportedintoothersoftwaretoassistinprogrammingthemachinetool.ElementsofCADThedesignprocessinaCADsystemconsistsoffourstages,asdescribedbelow.Geometricmodeling.Ingeometricmodeling,aphysicalobjectoranyofitspartsdescribedmathematicallyorytically.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)Designysisandoptimization.Afterthedesign’sgeometricfeatureshavemayconsistofyzingstresses,strains,deflection,vibrations.Thisphasetemperaturedistribution,ortolerance.Varioussophisticatedsoftwarepackagescapableofcomputingthesetiesaccurayandrapidlyareavailable.Designreviewandevaluation.Animportantdesignstageisreviewandevaluationtocheckforanyinterferencebetweenvariouscomponentsinordertoavoiddifficultiesduringassemblyoruseofthepart,andwhethermovingmembers,suchaslinkages,aregoingtooperateasintended.Softwareisnowavailablewithanimationcapabilitiestoidentifypotentialwithmovingmembersandotherdynamicsituations.Duringthedesignreviewandevaluationstage,thepartispreciselydimensionedandtolerance,asrequiredformanufacturingit.ationanddrafting.Aftertheprecedingstageshavebeencompleted,thedesignisreproducedbyautomateddraftingmachinesfor ationandreference.Detailandworkingdrawingsarealsodevelopedandprinted.TheCADsystemiscapableofdevelodraftingsectionalviewsofthepart,scalingthedrawings,andtransformationtopresentvariousviewofthepart.InCADsystems,muchofthedesignprocesswasformerlycarriedoutonworkstationconnectedtoamainframecomputer,butthetrendhaschangedrapidlytopowerful,high-performance,andmuchlessexpensivestand-alonedesktop32-bitUnixworkstation;64-bitprocessorswithevenbetterperformancearealso ingavailable.TheDesignBeforedelvingintoCAD,itisimportanttounderstandthedesignprocessitself.Computertechniquesarenomorevaluablethanthetheoryonwhichtheyarebased.Afterashortdiscussionofdesigningeneral,wewillexplorehowthecomputercanhelpwitheachofthedesignstages.ShigleydefinesthedesignprocessasaniterativeprocedureconsistingofsixRecognitionofDefinitionofysisandThefirststep,recognitionofneed,arisesfromanidentifiedproblem.Suppose,forexample,thatanew,moreefficientjetengineisrequiredbecauseofafuelshortage.Step2,definitionoftheproblemismorespecific.Definingthespecificsofthejetengineinvolvesknowingthethrust,horsepower,allowableweight,etc.Someofthesespecificationsareconstraints;I.e.,theyarerequirementsthatmustbemetforthedesigntobefeasible.Thejetengineweightlimitmaybeoneconstraintontheavailableliftoftheplanewings.Aumweight,then,wouldbeaconstraint.Constraintsareusuallyexpressedasaumorminimumvalueorrageofvalues.Otherspecification,however,aretermedcriteria,i.e.,measuresofthegoodnessorqualityofthedesign.Criteriaareusedtomeasureadesignandcomparedesignsagainstoneanother,asoccursduringtheoptimizationstage.Onecriterionofthejetenginemaybegallonsoffuelburnedperhourorperoftravel.Criteriahavenoumorminimumlimitsonvalues.Asatisfactorydesignisoneinwhichalltheconstraintsaremet.Thisbestdesign,Iadditiontomeetingtheconstraints,willhavethebestcombinationofcriteriavalues.Selectionofconstraintsandcriteriaisanintegralpartofstep2,definitionoftheproblem.Followingdefinitionoftheproblem,thenextthreesteps(synthesis,ysis/optimization,andevaluation)areiterative.Synthesisandysisareperformedinconjunctionwithoneanother.Severaltypesofproblemscanariseduringthedesignprocess.Synthesisrequiresdeterminingtheotakestheformofengineeringdrawingsincludinggeometry,tolerances,materialtypes,andcomponentparnumbers.ysismayrangefromasimpleestheticevaluationtothesolutionofasetofcomplexdifferentialequationswhichdescribetheperformanceofthepartorassembly.Theresultsofysescanbeexpressedintabularorgraphicalform.Itisthejobofthedesignertoevaluatetheysisdataandtoperformanyredesign.Evaluationsalsoatypeofysis,butusuallyrequiresanexpensiveprototypeandracksofinstrumentation.Thedesignprocesscanbeverycostlyandinvolvemanypeople.Designcostmaybelowed,however,byreducingthenumberofpeopleandtheprototyprocessitself.TheysisisthecornerstoneofCAD.Theresultsgeneratedbyysismodulesareusedbytheengineertodeterminethefeasibilityofadesignortooptimizeorredesigntheobject.Fundamentaltoysisisdevelopedtoaccuraypredicttheperformancebasedonthedesignvariablevalues.Typically,sophisticatedysisprogramsaretheperformancemodelsofthedesign.Theuserdoesnotneedtoformulateequationswhichdescribetheperformanceorfunctionality.Whattheusermustnsteadistomodeltheobjectgeometryinanappropriateformat.Usuallytieengineerwhoisdesigningacommonlyyzedpartorassemblycanpurchaseysissoftwaretoevaluatethedesign.Itisonlyinthecaseofanunusualdesignorperformancerequirement,whereoff-the-shelfsoftwareisnotavailable,thattheengineermustformulateauniquemodel.Inthiscase,theengineerwillusuallyderiveamathematicalmodelintheformofequationsusinghelawsofphysicsandwriteaprogramtoreadthedesigndescriptionandcalculateteperformanceparameters.Thesecommonlyavailableysismodulesreadthedesigndescriptionandgenerateperformanceresulttheformofnumbers,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.Thecomputerallowsdesignstobeviewedandtestedbeforetheactualpartismanufactured.Thepartcanbetestedmakesureitfitswithanymatingpars.CADsystemcancheckforinterferenceofparts,whichcansavealotofwastedmachininganddevelopmenttime.CADsystemscanstress-testparttoseeiftheywillmeetthestrengthrequirementsoftheapplication.ThegraphicsabilitiesofCADsystemalsoallow3-Dviewingofpartfromanyangle.IntegratedTheemphasisofthechapterisintegratedCAD/CAM.Theintegrationaspectisplishedwhenthedesignandysismodulesareunitedintoonepackage.Thedesigngeometryenteredbythedesignercanbeusedbytheysisprogramsandbythemanufacturing,inspection,inventory,andotheraspectsoftheproductliftcycle.Themanifestationofintegratingsoftwareisrecognizedwhentheusercansitdownatacomputerterminal,designapart,viewitonthescreen,yzeitfordesignrequirements,andhittheproverbialmanufacturingbuttonthekeyboardtohavethepartmanufactured,inspected,andVariousstagesofintegrationdoexist,butnoneisascompleteastheexamplejustmentioned.Integrationimpliesautomation.AutomationimpliesthatthehardwareandsoftwarecancreateaCADdatabaseanduseittoyzeandmanufacturetheparttotallyautomatically,withlittleornohumanintervention.Thequestionastowh