CAD技術(shù)在液壓系統(tǒng)機械中的應(yīng)用外文文獻翻譯/中英文翻譯/外文翻譯

中國地質(zhì)大學(xué)長城學(xué)院  本科畢業(yè)設(shè)計外文資料翻譯  系     別：       工程技術(shù)系         專     業(yè)：  機械設(shè)計制造及其自動化  姓     名：         楊鵬飛           學(xué)     號：        05211528         2015年   3  月   15 日 1 CAD 技術(shù)在液壓系統(tǒng)機械中的應(yīng)用  產(chǎn)品發(fā)展的主要目標(biāo)是在一個短的時間的設(shè)計過程中，獲得低價格的產(chǎn)品和最終產(chǎn)品的最佳表現(xiàn)。根據(jù)這些目標(biāo)，產(chǎn)品設(shè)計必須使用一些先進的 CAD - CAM， CAE 軟件模塊 和互聯(lián)網(wǎng)的在線三維部分目錄（或多或少標(biāo)準(zhǔn)目錄）。通過使用不同的 CAD - CAM， CAE 軟件的一些模塊得到的好處是可以用低價格（這是沒有必要所有的軟件，只有一些特定的模塊，這些軟件（具體到工程領(lǐng)域）獲得最好表現(xiàn)的模塊。三維互聯(lián)網(wǎng)上的在線目錄提供的優(yōu)勢是很容易找到有關(guān)機械元件的有用信息（如價格，技術(shù)特點，三維模型等），對于相關(guān)產(chǎn)品的研發(fā)起到很大的推動作用，例如，液壓系統(tǒng)，旋轉(zhuǎn)樓梯等。  關(guān)鍵詞： CAD/CAM 技術(shù)，轉(zhuǎn)臺，液壓系統(tǒng)，齒輪傳動。  一、緒論  現(xiàn)在，業(yè)內(nèi)的高度競爭促使產(chǎn)生新的，更好，更便宜的產(chǎn)品。汽車制 造商已經(jīng)處理了客戶日益增長的需求。他們必須不斷提高產(chǎn)品的構(gòu)思方法，以現(xiàn)代化的組織結(jié)構(gòu)，以創(chuàng)造一個流暢的鏈接，而沒有研究，設(shè)計，制備，制造，商業(yè)化和工作產(chǎn)品的生命之間的限制。要成為一個更加具有國際競爭力公司，他須有產(chǎn)品的多樣性與不斷變化，該公司必須現(xiàn)代化，提高生產(chǎn)系統(tǒng)的靈活性。該公司發(fā)現(xiàn)，一種產(chǎn)品的交互設(shè)計是最有效的工具，用于分析評價結(jié)束。因此，互聯(lián)網(wǎng)數(shù)據(jù)基礎(chǔ)和的 CAD - CAM - CAE 軟件的使用也帶來視覺的幾何數(shù)據(jù)基礎(chǔ)和工業(yè)設(shè)計。工藝和產(chǎn)品開發(fā)使用計算機和網(wǎng)絡(luò)環(huán)境可以獲得大量成本和時間的節(jié)約。在市場上 有許多的 CAD - CAM， CAE 軟件為工程設(shè)計人員提供設(shè)計一個三維虛擬空間的很多具體的工具。  二、運用多種 CAD - CAM 的 CAE 技術(shù)軟件包  這些類型的軟件都代表一個非常有用的工具在產(chǎn)品開發(fā)設(shè)計過程中的作用。人們通過使用它可以創(chuàng)建一個三維虛擬產(chǎn)品，從模擬的角度分解成許多點，以改善其特性（非技術(shù)性的或技術(shù)性的）。這些軟件更好的應(yīng)用于航空，汽車，機械等行業(yè)。今天單一的 CAD - CAM，CAE 軟件在工程領(lǐng)域的表現(xiàn)有些不能涵蓋整個工業(yè)的高場演出。這些軟件的另一個主要缺點是一個完整版本的價格非常高。通常的價格是 起價幾千歐元。  對于大多數(shù)的 CAD - CAM， CAE 軟件有三個優(yōu)勢： 1 - 軟件的是結(jié)構(gòu)化模塊，即使在同一地區(qū)（例如：在 CATIA 機械設(shè)計中：部分設(shè)計 ;優(yōu)勢鈑金設(shè)計，模具設(shè)計，管道設(shè)計和曲面設(shè)計等） ;我們可以只買一些具體的一攬子關(guān)于電腦輔助設(shè)計，計算機輔助制造，計算 2 機輔助工程的部分 ; 3 - 所有這些軟件均容許以節(jié)省許多公共文件格式   例如（ date：二維的drawings，三維固體一步的 dxf ， IGES 等）。這些類型的文件可以打開幾乎所有在某些特定條件下的 CAD - CAM， CAE 軟件  對于一個復(fù)雜的 產(chǎn)品（例如：在汽車行業(yè)），其中需要許多復(fù)雜曲面造型。單一的 CAD - CAM， CAE 軟件是不夠的。在這種情況下，解決方法是使用不同的 CAD - CAM， CAE 軟件中一些表現(xiàn)突出的具體模塊。  三、在產(chǎn)品開發(fā)中利用網(wǎng)絡(luò)設(shè)施。  如今互聯(lián)網(wǎng)的發(fā)展提供了通過電子郵件傳播最新的浪潮，文件傳輸，遠(yuǎn)程登錄訪問，交易應(yīng)用，等等。  互聯(lián)網(wǎng)的最流行的部分原是萬維網(wǎng)，原因是在那里任何人都可以訪問同一個按鈕單擊超文本網(wǎng)頁。互聯(lián)網(wǎng)的普及，推出了眾多的社會和倫理問題。最近，互聯(lián)網(wǎng)已經(jīng)被批評為未經(jīng)審查的信息，但其教育價值一直被人們所公認(rèn)的 稱贊。在工程領(lǐng)域的互聯(lián)網(wǎng)被用來傳播信息和公司的廣告。今天，所有的大公司都在互聯(lián)網(wǎng)上提供了許多他們產(chǎn)品的信息。在機械工程領(lǐng)域的大多數(shù)公司也提供有關(guān)產(chǎn)品（許多有技術(shù)特點的免費文件，免費二維圖紙和三維模型免費目錄），價格，演算技術(shù)軟件（例如：軸承斯凱孚等）。  在互聯(lián)網(wǎng)上存在著許多擁有專用產(chǎn)品開發(fā)水平的網(wǎng)站。從圖 6（螺絲，軸承，滑輪小學(xué)部分標(biāo)準(zhǔn)目錄開始，皮帶，齒輪等）和完成復(fù)雜的產(chǎn)品（如工業(yè)機器人  - 圖 7）互聯(lián)網(wǎng)是一個在設(shè)計過程中所有的同類產(chǎn)品的有用工具。  互聯(lián)網(wǎng)的缺點是不斷增加的信息的多樣性和傳播途徑。最大的問 題是如何找到這個虛擬空間有用信息。  1.在互聯(lián)網(wǎng)上查找有用的三維目錄  今天互聯(lián)網(wǎng)上的信息的結(jié)構(gòu)分為網(wǎng)頁。幾乎所有的公司都在世界上的網(wǎng)頁，以提供更多有關(guān)其產(chǎn)品的信息。  有三種方式搜索： 1，尋找到一些具體的工程領(lǐng)域的公司。如果公司的名稱，通常被稱www.（ company） .com！（例如： SKF 有 ）。如果不是，一個簡單的方法是使用搜索網(wǎng)站如谷歌（ 搜索網(wǎng)站）和關(guān)鍵字的公司名稱 ; 2，找一些具有相似產(chǎn)品的公司他們會有相關(guān)公司的連接，還能使用關(guān)鍵字搜索網(wǎng)站谷歌和類似產(chǎn) 品公司技術(shù)言語形容的產(chǎn)品。例如找到軸承公司可以使用：如“軸承”關(guān)鍵字，“球軸承”等 ; 3，尋找某些特定產(chǎn)品（標(biāo)準(zhǔn)或不）為特定的工程領(lǐng)域，建議使用專用的門戶網(wǎng)站。門戶網(wǎng)站是其中包含的信息，并為特定領(lǐng)域網(wǎng)站的鏈接。   3 對在工程領(lǐng)域的互聯(lián)網(wǎng)公司在介紹他們的產(chǎn)品目錄結(jié)構(gòu)。有兩種類型的網(wǎng)站目錄。  一個是在著名的格式 PDF（便攜式文檔格式）。為了找到這是推薦使用的搜索類型目錄，經(jīng)過特定的關(guān)鍵字，首字母縮寫“ PDF 格式”。它的優(yōu)點是使用的 PDF 目錄，所有有關(guān)的產(chǎn)品所需的資料，為單文件，它可以打印提交。  另一種是交互式的在線 目錄有一些類似的優(yōu)勢： 1，查找所有的產(chǎn)品（包括 PDF 格式的信息）， 2，在線演算軟件， 3，產(chǎn)品可直接到 CAD - CAM 的實施 - CAE 軟件。為了找到這種類型的目錄，建議用“三維目錄關(guān)鍵詞在網(wǎng)上與關(guān)鍵字相結(jié)合的技術(shù)”。例如在網(wǎng)上找到一個齒輪目錄三維它可用于搜索下一個字符串使用：“齒輪三維目錄上線”。  2.使用三維零件目錄  在圖 9 給出了一個三維齒輪目錄搜索結(jié)果的屏幕捕獲。用紅色箭頭標(biāo)記為可能的三維互聯(lián)網(wǎng)地址目錄。在紅色矩形標(biāo)志著交互式目錄地址圖 10 介紹。在圖 10 給出了它提供免費的3D 和 2D 技術(shù)產(chǎn)品目錄門戶。由 于它是提出了一個例子目錄威爾在齒輪設(shè)計中使用的數(shù)字 5所列。選擇在這個目錄有一個威爾指定所有必要的參數(shù)： 1.直徑 ; 2.齒數(shù) ; 3.Material; 4.齒形風(fēng)格 ; 5 質(zhì)量等級  6.壓力角度 ; 7.孔尺寸 ; 8.齒寬 ; 9.齒間距 ; 在圖 11的技術(shù)特點中提出了選擇齒輪的所有特征在此目錄（可通過 https： / /sdp - ）所有選定的特點、價格；進入相關(guān)的 CAD - CAM - CAE 系統(tǒng)均是可直接執(zhí)行的文件格式。  它的三維模型被選中了 step 格式（用于固體組件的格式）。建成后的 CAD 軟件實現(xiàn)幾個小的修改，是基于堅實的威爾與齒輪按設(shè)計要求。它建了一個關(guān)鍵的鍵槽和一個圓形孔（基于方便建模的原因）。對于減速器，只有部分相關(guān)與箱體和主軸設(shè)計。在圖 14 A 的標(biāo)記目錄（齒輪，螺絲，軸承，鍵與） b 圖是在 CATIA V5 的設(shè)計的基本要素。  小結(jié)  本文中標(biāo)準(zhǔn)建模和分級建模概念被確定為 RMTs 建模方法的主要特點。 RMTs 的模塊化結(jié)構(gòu)使這種建模方法很有益處，因為這些模型包含了所有可重構(gòu)的重要特征 5：  1模塊化：（子）組件建模模塊化  2可集成：該模塊可以通過其連接端口與其他模塊集成  3定制：詳細(xì)程度包括了模型 模塊都可為單個組件進行定制  4可重構(gòu)性：模型可以很容易地從一個配置轉(zhuǎn)換到另一個  5診斷性：可方便地進行模塊的模型驗證  本文介紹的方法可以將建模任務(wù)分為兩個步驟：（ 1）開發(fā)組件模型；（ 2）裝配配置模型。 4 雖然第一步仍然需要大量的建模知識，第二步更系統(tǒng)，甚至將來要實現(xiàn)自動化。此外，兩個步驟各有側(cè)重：第一步的重點是組件內(nèi)動態(tài)，而第二個步驟重點是組件之間的動態(tài)。相對于伺服軸建?，F(xiàn)有的方法，各個不同的 RMTs 配置都是一個潛在的新建模問題，本文提出的方法允許配置模式更快的發(fā)展。配置可以使用庫中的模型模塊快速組裝，假若 如此，使用在給定配置的所有組件在模庫中都有對應(yīng)的模塊。因此，一個完善的模型庫對這一方法的有效性是必不可少的。  對機床的機械部件三維多體建模方法推動了機械領(lǐng)域的模塊化。因此，機床滑動模型可用于任何配置，例如在一個滑臺移動有更多約束的環(huán)境下而不需要特別的滑臺模型。以多體的方法，開發(fā)通用組件模型可以沒有組件接口的先驗知識。然而三維多體方法的一個缺點是通用模型可能比某一實際配置的需求更復(fù)雜。例如，在給定的配置中一個組件可能只是被限制在一個平面運動中，在這種情況下，三維模型就過復(fù)雜了。該模型應(yīng)該簡化，否則模型中不必要 的復(fù)雜性降低了模型的計算效率。擬議的模塊化建模方法將從集成模型降階算法中受益。這將是今后工作的重點。 由于銑削加工切削用量及切削得力很大，同時又是多刃斷續(xù)切削，加工時很容易產(chǎn)生振動，因此設(shè)計銑床夾具時應(yīng)注意：夾緊力的大小必須調(diào)整合適，夾緊力設(shè)置過小，工件可能在加工過程中移動而破壞夾具定位，不僅嚴(yán)重影響質(zhì)量，還可能造成事故；夾緊力過大，不但會使工件和夾具本身產(chǎn)生變形，其加工質(zhì)量也不高；夾具的安裝要準(zhǔn)確可靠，即安裝及加工時要正確使用定向鍵、對刀裝置；夾具要有足夠的剛度和穩(wěn)定性，設(shè)計結(jié)構(gòu)要合理。車床夾具一般都是在懸 臂狀態(tài)下工作，為保證加工過程的穩(wěn)定性；夾具結(jié)構(gòu)應(yīng)力求簡單緊湊，輕便且安全，懸伸長度盡量小，使重心設(shè)計靠近主軸前支承。為保證安全 , 夾具體應(yīng)制成圓形，加具體上的各元件不允許伸出夾具體直徑之外；夾具的結(jié)構(gòu)還應(yīng)便于工件的安裝、測量和切屑的順利排出和清理。  目前，該機構(gòu)被認(rèn)為是剛性，這并不總是很接近。為了能夠研究結(jié)構(gòu)動力學(xué)的影響，柔性的機構(gòu)模式也應(yīng)開發(fā)并添加到模庫內(nèi)。  最后，值得注意的是商業(yè)可用軟件包如 ADAMS,、 DADS、  EASY5、  Dymola 等也可用于 RMTs 建模的目的。然而，采取統(tǒng)一強大的鍵合圖提供 的功能，并簡化未來的模式使其更易于實施，那么鍵合圖就被選為建模語言。  通過使用不同的 CAD - CAM - CAE 技術(shù)性能為基礎(chǔ)的軟件系統(tǒng)，不同的模塊，優(yōu)化工藝設(shè)計，可從技術(shù)角度來選擇，無需額外費用。無需為了一個單一的 CAD - CAM， CAE 系統(tǒng)模塊買一些沒有更好模塊的軟件花費更高的費用。  通過使用在線互動目錄的設(shè)計過程會更加簡單。通過對相關(guān)的所有技術(shù)和非技術(shù)的數(shù)據(jù) 5 元素使用，設(shè)計人員可以很容易做出產(chǎn)品成本推估（從各個要素的角度的）。  利用的 CAD - CAM， CAE 軟件和互聯(lián)網(wǎng)設(shè)施的產(chǎn)品開發(fā)的主要 優(yōu)勢是耗費時間很短，可以致力于設(shè)計過程。這種方法提高約 70-80。  參考：  1康斯坦丁伊斯帕斯，米龍，克里斯蒂娜莫霍拉，多雷爾安尼亞，研究有關(guān)的機械系統(tǒng)的綜合概念，第一屆國際計算機及解決方案在制造工程會議科姆（ 04），布拉索夫， 2004 2吉奧內(nèi)亞第一部分，安尼亞第四部分  - “計算機的管理使用計算機輔助設(shè)計的虛擬原型”，關(guān)于制造系統(tǒng) ICMaS 國際會議論文集，作者  愛氪迪曼  羅曼， 2002 年的布加勒斯特   6 Application of CAD technology in the construction machinery The main goals to the product development are to obtain a short time of design process, a low price and best performances of the final product. According to these goals, the product design must use some modules of advanced CAD-CAM-CAE software and the internet on-line 3D catalogs for some parts (more or less standard). The advantage obtained by using some modules from different CAD-CAM-CAE software is to use the most perform ant parts of these software (specific to the engineering fields) at a low price (it isnt necessary all the software, only some specific modules). The internet 3D on-line catalogs offer the advantage to find very easy useful information about mechanical elements (prices, technical characteristics, 3D models, etc). Key words:  CAD-CAM swivel table slighter tower machine 1.INTRODUCTION Now, in the industry exists a high competition to produce new, better and cheaper products. The manufactures have to deal with the increasing demands of the customers. They have to improve continuously the conception methods of the products, to modernize the organization structure in order to create a fluent link, without limits, between studies, design, preparation, manufacturing, commercialization and working life of the products. To become more competitive into a world with diversity of products, with continuous changes,  the  companies  must  modernize  and  increase  the  flexibility  of  the  production systems. The companies find out that the interactive design of a product is the most efficiently tool  for  analysis  end  evaluation.  So  the  use  of  internet  data  base  and  CAD-CAM-CAE software creates visual data base and industrial geometry design. Process and product development using computers and internet environment allow a substantially costs and time economy. On the market there is a lot of CAD-CAM-CAE software which offer specific tools for engineering design into a tri dimensional virtual space. 2.USING MULTIPLE CAD-CAM-CAE SOFTWARE PACKAGES These kinds of software are representing a very useful tool in products development design process. By using them it can be created a 3D virtual product, simulate from many point of view 1, in order to improve its characteristics (technical or non technical).Some of these softwares have better performances for some engineering fields as aeronautics, automotives, mechanical etc. Today single CAD-CAM-CAE software cannot cover the entire industrial field for high performances. Another major disadvantage of that softwares is very high prices for a full version. Usual the prices are starting from several thousands of EUR. There are 3 advantages for the most CAD-CAM-CAE softwares: 1 - the softwares are structured in modules, even in the same area (for example: in CATIA in mechanical design are: part design; sheet metal design, mold design, wiser frame and surfaces design etc);it can be bought only some specific package regarding computer aided design, computer aided manufacturing or computer aided engineering; 3 - all these software allow to save date in some commune file format (for example: dxf for 2D drawings, step for 3D solids; iges for3D surfaces etc). These types of files can be opened by almost all CAD-CAM-CAE software in some specific condition. For a complex product (ex. in automotive industry) which need complex surfaces for  7 modeling a single CAD-CAM-CAE software isnt sufficient. In this case the solution is to use some high preferment specific modules from different CAD-CAM-CAE software. 3.USING INTERNET FACILITIES IN PRODUCT DEVELOPMENT. The growth of the Internet today offers the newest wave of communication through electronic mail, file transfer, telnet access, transaction applications, and much, much more. The most popular part of the Internet is the World Wide Web, where anyone can access hypertext pages with the click of a button. The popularity of the Internet has launched many social and ethical issues. Recently, the Internet has been criticized for its uncensored information, but has been praised for its educational value. In engineering field the internet is used for information dissemination and company advertising. Today all the big company offers many information about their products directly on the internet. In the mechanical engineering fields the most companies offer free catalogs about products (free documentation about technical characteristics, free 2D drawings and 3D models), prices, calculus technical software (ex: bearings SKF) etc. On the internet exists dedicated sites for all level of product development? Starting from standard catalogs for elementary parts fig.6 (screws, bearings, pulleys, belts, gears etc) and finished with complex products (like industrial robots fig.7) the internet is a useful tool in design process for all kind of products. The disadvantage of the internet is the increasing diversity of information and the way of dissemination. The big problem is how to find utile information in this virtual space on internet. 1. Finding useful 3D catalogs on internet Today on internet the information is structured into web pages. Almost all the companies in the world have web pages in order to offer more information about their products. There are 3 ways to search: 1 , to find a company into some specific engineering fields. If the name of company is known usually the site is www。（ names） .com (ex: SKF has  ).  If is not, an easy way is to use a searching site as google ( ) and as keywords the company name; 2 , to find some companies witch have similar products it is recommended to use searching site as google and keywords technical words witch describe the product. For example to find bearing companies it can be use: keywords like “bearings”; “ball bearings” etc.; 3 , to find  some specific products (standard or not) for a specific engineering field it is recommended to use dedicated portals. A portal is a site which contains information and links to specific sites for a domain. On internet in the engineering fields the companies presents their products structured in catalogs. There are two types of catalogs on web. One is in well-known format PDF (portable document format). To find catalog of this type it is recommended for searching to use, after specific keywords, the acronym “PDF”. The advantage using a PDF catalogs is that all the needed information about a product is presented into single file, which can be printed.  The other is interactive on-line catalogs which have some advantages like: 1- to find all information for a product (including in PDF format), 2- on-line calculus software, 3 -the product can be directly implemented into CAD-CAM-CAE software. To find such types of catalogs it is recommended to use keywords as “3D catalogs on-line” in combination with technical keyword. For example to find a gears catalog 3D on line it can be use for searching the next string: “gears 3D catalogs on-line”.  8 2.Using 3D component catalogs In figure 9 is presented a screen capture for the results of 3D gears catalog search. With red arrow is marked possible internet address for 3D catalogs. In red rectangle is marked the address for interactive catalog presented in figure 10. In figure 10 is presented a portal for technical products which offers free 3D and 2D catalogs. As example it is presented a catalog wheal used in design of gear presented in figure 5. For selecting a wheal in this catalog it has to specify all the necessary parameter: 1.Diametral Pitch; 2.No. Of Teeth; 3.Material; 4.Hub Style; 5.Quality Class; 6.Pressure Angle Degree; 7.Bore Size; 8.Face Width; 9.Pitch Dia; In figure 11 is presented all the characteristics available in this catalog (https:/sdp- ) for selected wheal as technical characteristics; prices; available file formats for direct implementation into CAD-CAM-CAE systems. For 3D model it was selected a step format (used for solid component). After implementation into CAD software a few minor modifications were made on the solid wheal according with the gears design requirements. It was made a key pocket and a circular pocket (for constructive reason). For a speed reducer only a few parts were designed as shells and spindles. In figure 14 with A are marked catalogs elements (wheals, screws, bearings, keys) With B are marked elements designed in Catia V5. CONCLUSION This article standard modeling and hierarchical modeling concepts are identified as the main characteristic of RMTs modeling method.RMTs modular structure makes the modeling method is very good, because the model contains all the important features of reconfigurable 5. 1. The modular (sub) modular component modeling. 2. Can be integrated, the module can be integrated through its connection with other modules. 3. Custom: detail including the model module can be customized for individual components. 4. The reconfigurable sex: model can easily transfer from one configuration to another 5. Diagnostic: can easily model validation module This paper introduces the method of modeling tasks can be divided into two steps: (1) the development of component model;(2) assembly configuration model. Although the first step is still need a lot of knowledge modeling, the second step is more system, even in the future to realize automation. In addition, a focus of two steps: the first step is the focus of the dynamic components, and the second step is focused on the dynamic between components. Compared with the existing servo axis modeling method, different RMTs configuration is a potential new modeling problem, the proposed approach allows configuration mode, faster development. Configuration can use the model in the library module assembly quickly, if so, to use in a given configuration of all components in the model library has a corresponding module. Therefore, a perfect model library is indispensable to the effectiveness of this method. Mechanical components of machine tool 3 d multi-body modeling method promoted in the field of mechanical modularity. Therefore, machine tool slide model can be used in any configuration, for example, in a slider move more constraint conditions without the need for special sliding table model. With multi-body method, develop common component model can do not have prior knowledge of component interface. However a disadvantage of the three-dimensional multi-body method is a generic model might be more complicated than an actual configuration requirement. For example, in a given configuration of a component may be  9 confined to a plane, in this case, the 3 d model is too complex. The model should be simplified, otherwise unnecessary complexity in the model reduces the computation efficiency of the model. The proposed modular modeling method will benefit from the integration model order reduction algorithms. This will be the focus of future work. Due to milling cutting dosage and cutting strength is very big, is also more intermittent cutting blade, processing is easy to cause vibration, so the design of milling machine fixture should be paid attention to: the size of the clamping force must be adjusted, appropriate clamping force set is too small, could move in the machining process and work piece fixture positioning, not only seriously affect the quality, can also cause accidents; Clamping force is too large, not only can make the work piece deformation and jig itself, its processing quality is not high; Fixture to be accurate and reliable installation, the installation and processing to correctly use the directional keys, device on the edge of the sword; Should have enough stiffness and stability, jig design structure to be reasonable. Lathe fixture are generally work under cantilever state, in order to ensure the stability of machining process; Fixture should strive to simple and compact structure, lightweight, safe, overhanging length is small, as far as possible to design close to the main shaft bearing before. Concrete should be made to ensure safety,