【正文】 ，將使壽命下降和摩擦力矩加大，通常，滾珠絲桿在出廠時，就已經(jīng)由制造商調好預加載荷，并且預加載荷往往與絲桿副的額定動載荷有一定的比例關系。②結構緊湊，工作可靠，調整方便，但準確性差，且易于松動，適用于剛度要求不高或隨時調節(jié)預緊的傳動。(1)絲杠的變形量主要指絲杠在運動時所受的拉伸和壓縮變形量，其在變形量中占的比重較大，并按以下公式計算：其中a為絲杠兩端支承之間的距離，單位mm；E為絲杠材料的彈性模量鋼的E=MPa，S為絲杠底徑確定的截面慣性矩（），單位為，而公式中的第二項由于轉矩較小，故可忽略不計。為便于計算取傳動比。為了提高定位精度和工作的平穩(wěn)性，要盡可能減小傳動間隙。由于本設計采用的是二級傳動，則有等效轉動慣量的計算如下：折算到步進電機軸上的等效負載轉動慣量為：式中：分別為為齒輪的轉動慣量；為滾珠絲杠的轉動慣量；為移動部件的質量。（1）快速空載起動時電動機轉軸所承受的負載轉矩：為快速空載起動時折算到電動機轉軸上的最大加速轉矩，計算公式如下：式中為電動機轉軸的角速度，單位，電動機的轉速，單位r/min；為電動機加速所用時間，單位s，~1之間。 步進電機參數(shù)表型號主要技術參數(shù)相數(shù)步距角電壓(V)相電流(A)最大靜轉矩 ()空載起動頻率空載運行頻率分配方式55BF00332731800180003相8拍外形尺寸(mm)重量(kg)轉子轉動慣量()外直徑長度軸直徑55906步進電機性能校核包括最快工作進給速度時電動機輸出轉矩校核、最快空載移動時電動機輸出轉矩校核和起動頻率的校核等?？刂葡到y(tǒng)的控制對象主要包括各種機床，如車床、銑床、磨床等等。8031采用40條引腳的雙列直插式封裝（DIP），引腳和功能分為三個部分。（20腳）：接地。在單片機內部，它是一個反相放大器的輸入端。若采用外部晶體振蕩器時，該引腳接受振蕩器的信號，即把信號直接接至內部時鐘發(fā)生器的輸入端。復位后應使此引腳電平為的低電平，以保證單片機正常工作。即使不訪問外部存貯器，ALE端仍有周期性正脈沖輸出，其頻率為振蕩器頻率的1/6。在從外部程序存儲器指令（或常數(shù)）期間，每個機器周期兩次有效。當端保持低電平時，則不管是否有內部程序存貯器而只訪問外部程序存儲器。P0口（）：為雙向8為三態(tài)I/O口，當作為I/O口使用時，可直接連接外部I/O設備。P2（）：為8位準雙向I/O口，當作為I/O口使用時，可直接連接外部I/O設備。單片機的時鐘產(chǎn)生方式有內部時鐘方式和外部時鐘方式兩種，大多單片機應用系統(tǒng)采用內部時鐘方式。CC2可在20PF100PF之間選擇，一般當外接晶體時典型取值為30PF，外接陶瓷諧振器時典型取值為47PF，取60PF70PF時振蕩器有較高的頻率穩(wěn)定性。它是施密特觸發(fā)輸入，當振蕩器起振后，該引腳上出現(xiàn)兩個機器周期（即24個時鐘周期）以上的高電平，使器件復位，只要RST保持高電平，MCS51便保持復位狀態(tài)。MCS51單片機通常采用上電自動復位和按鈕復位兩種方式。上圖那上電按鈕復位電路只需將一個常開按鈕開關并聯(lián)于上電復位電路，按下開關一定時間就能使RST引腳端為高電平，從而使單片機復位。另外，在單片機內部雖然設置了若干并行I/O接口電路，用來與外圍設備連接。用作程序存貯器的常用的器件是EPROM。根據(jù)應用系統(tǒng)對程序存貯器容量要求的不同，常采用的擴展芯片擴展EPROM2716（2KB8）、2732A（4KB8）、2764A （8KB8）、27128A（16KB8）、27256A（32KB8）和27512（64KB8）等。如果只擴展一片程序存貯器EPROM，故可將片選端CE直接接地。CPU對內部的RAM具有豐富的操作指令。正因為如此，數(shù)據(jù)存貯器與程序存貯器可完全重疊，均為0000HFFFFH，但數(shù)據(jù)存貯器與I/O口與外圍設備是統(tǒng)一編址的，即任何擴展的I/O口以及外圍設備均占用數(shù)據(jù)存貯器地址。單一+5V供電，額定功耗分別為160mW和200mW，典型存取時間均為200ns，均有雙列之插式封裝，管腳分別為24和20線。6264的地址范圍為0000H7FFF。數(shù)據(jù)存貯器6264的地址為0000H7FFFH。常用的MCS51并行I/O接口擴展方法主要有四種：采用可編程的并行接口電路，如8255A；采用可編程的RAM/IO擴展器，如8155；采用TTL或CMOS電路的三態(tài)門、鎖存器，如74LS3774LS3774LS244；利用MCS51的并行擴展并行I/O接口。故8255的A、B、C口及控制口地址分別為FF7CH、FF7DH、FF7EH、FF7FH。8155/8156芯片內包含有256個字節(jié)RAM，2個8位和一個6位的可編程并行I/O口，一個14位定時器/計數(shù)器。在8155的控制邏輯部件中，設置一個控制命令寄存器和一個狀態(tài)標志寄存器。第7位用來設置定時器/計數(shù)器的操作。狀態(tài)標志寄存器的地址與命令寄存器的地址相同，CPU只能讀出，不能寫入。I/O寄存器地址分別為:命令/狀態(tài)字寄存器地址7F00H,PA口地址為7F02H,PB口地址為7F03H,定時器/計數(shù)器低字節(jié)寄存器地址為7F04H,定時器高字節(jié)寄存器地址為7F05H. 8155的擴展電路圖 鍵盤、顯示器接口設計 矩陣式鍵盤接口設計矩陣式鍵盤適用于按鍵較多的場合,它由行線和列線組成,按鍵位于行、4的行、,矩陣鍵盤比獨立鍵盤節(jié)省了很多I/O口.按鍵設置在行、列線分別連接到按鍵開關兩端..行線通過上拉電阻接到+,行線處于高電平狀態(tài),而當有按鍵按下時,則行線電平為低。工作可靠?；亓?，使工具電極沿X軸、Y軸、Z軸回到機械零點。此次設計是我們材料成型與控制工程專業(yè)學生在學完四年課程后進行的一次綜合性的、系統(tǒng)性的、理論聯(lián)系實際的設計活動，也將是整個南華大學第一次看到由我們材控專業(yè)學生設計的論文，我們既激動又高興，最重要的是我們從中獲益匪淺。成功的完成了這次設計，這次的經(jīng)歷為我們以后作為工程技術人員打下了良好的基礎。希望各位老師及同學給予批評指正，將不勝感激！ 設計人：杜經(jīng)綸2010年5月25日附 錄1 Scope of CAD/CAMComputeraided design is the use of puter systems to facilitate the creation, modification, analys, and optimization of a design. In this context the term puter system means a bination of hardware and software. Computeraided manufacturing is the use of a puter system to plan, manage, and control the opemtion of a manufacturing plant. An appreciation of the scope of CAD/CAM can be obtained by considering the stages that must be pleted in the design and manufacture of a product, as illustmted by the product cycle shown in Fig. 5 . 8. The inner loop of this figure inludes the various steps in the product cycle and the outer loop shows some of the functions of CAD/CAM superimposed on the product cycle . Based on market and customer requirements, a product is conceived, which may well be a modification of previous products. This product is then designed in detail, including any required design analysis, and drawings and parts lists are prepared. Subsequently, the various ponents and assemblies are planned for production, which involves the selection of sequences of processes and machine tools and the estimation of cycle times, together with the determination of process parameters, such as feeds and speeds. When the product is in production, scheduling and control of manufacture take place, and the order and timing of each manufacturing step for each ponent and assembly is detemnned to meet an overall manufacturing schedule. The actual manufacturing and control of product quality then takes place according to the schedule and the final products are delivered to the customers. Computerbased procedures have been or are being developed to facilitate each of these stages in the product cycle, and these are shown in the outer loop of Fig. 5 . 8. Computeraided design and drafting techniques have been developed. These allow a geometric model of the product and its ponents to be created in the puter. This model can tlIen be analyzed using specialized software packages, such as those for finite element stress analysis, mechanisms design, and so on. Subsequently, dmwings and parts lists can be produced with puteraided drafting software and plotters. Computeraided processplanning systems, including the prepamtion of NC programs, are available that produce work plans, estimates, and manufacturing instructions automatically from geometric descriptions of the ponents and assemblies.Or scheduling and production control, large amounts of data and numerous relatively simple calculations must be carried out. One example is the determination of order quantities by subtmcting stock levels from forecasts of the number of items required during a particular manufacturing period174。\onably sophisticated ponent) and generating manufacturing plans, preparing paIt programs and producing the pm is possible in days rather than weeks. In general, the tatal en!?ineering aI1d manufacturing time has been markedly using integrated CAD/CAM methodalogies. 2 Computer Aided lVIanufacturing The scientific study of metalcutting and autamatian techniques are pnxlucts af the twentieth century. Two. pianeers of these techniques were Frederick Taylar and Henry Ford. During tl1e early 1900s, the improving U. S. standard af living brought a new high in penlOnal wealth. 3