土豆挖掘機(jī)的設(shè)計(jì)-馬鈴薯收獲機(jī)【三維SW】
土豆挖掘機(jī)的設(shè)計(jì)-馬鈴薯收獲機(jī)【三維SW】,三維SW,土豆,挖掘機(jī),設(shè)計(jì),馬鈴薯,收獲,三維,SW
本科畢業(yè)設(shè)計(jì)(論文)
題目：土豆挖掘機(jī)的設(shè)計(jì)
院 系： 機(jī)械工程學(xué)院
專 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化
學(xué) 號：
姓 名：
指導(dǎo)教師：
2016年4月
摘要
土豆作為人們的主要食品之一，具有豐富的營養(yǎng)價(jià)值，人們在日常生活中，人們都會(huì)圍繞土豆來做出各種不同的菜肴，例如炒菜，燉湯等等。而通過刀具切削土豆片會(huì)很麻煩，如果有能夠?qū)ν炼惯M(jìn)行自動(dòng)挖掘的機(jī)械，那樣在一定程度上會(huì)大大提高挖掘效率和質(zhì)量。
該土豆挖掘機(jī)主要由機(jī)架、連接桿、擺臂、連接件、曲柄、抖動(dòng)輪、挖掘鏟、定位軸、地輪等等零部件組成。動(dòng)力是通過拖拉機(jī)帶動(dòng)該土豆挖掘機(jī)在農(nóng)田里面進(jìn)行自動(dòng)挖掘作業(yè)。該機(jī)效率高，產(chǎn)能好，適合批量挖掘土豆的場所。
關(guān)鍵詞：土豆挖掘機(jī)；機(jī)架；挖掘鏟；產(chǎn)能
I
Abstract
potatoes as one of the main food of the people, with rich nutritional value, people in daily life, people will around the potato to make a variety of dishes, such as cooking, soup, and so on. And through the cutting tool cutting potato chips will be very troublesome, if there is to be able to peel the skin of the machine, then to a certain extent, will greatly improve the efficiency and quality of the peel.
The potato peeler is through artificial potatoes into potato peeling machine barrel inside, at the bottom of the motor through the transmission gear to drive the transmission shaft to rotate, so as to drive the rotating body rotation, rotation body spot welding can be through the potatoes with a rotating body surface friction and skin small metal grinding, potatoes and with the rotary body to rotate together, and the inner wall of the cylinder body welding scraping knife, that comes with the rotation of the rotating body, the inside of the barrel body of potatoes has been constantly and the surface of a rotating body of small metal grinding blade and the inner wall of the barrel body scraping knife friction to the skin effect
Key words:Potato peeling machine,cutting tool,rotating body, peeling
II
目 錄
摘要 I
Abstract II
1緒論 1
1.1 課題的來源與研究的目的和意義 1
1.2 本課題研究的內(nèi)容 2
1.3 國內(nèi)外發(fā)展現(xiàn)狀 2
2土豆挖掘機(jī)總體結(jié)構(gòu)的設(shè)計(jì) 4
2.1 土豆挖掘機(jī)的總體方案圖 4
2.2 土豆挖掘機(jī)的工作原理 4
2.3 機(jī)械傳動(dòng)部分的設(shè)計(jì)計(jì)算 5
2.3.1V帶傳動(dòng)的設(shè)計(jì)計(jì)算 7
2.3.2軸承的設(shè)計(jì)計(jì)算 8
2.3.3軸的設(shè)計(jì) 8
3各主要零部件強(qiáng)度的校核 10
3.1機(jī)架強(qiáng)度的校核與計(jì)算 11
3.2轉(zhuǎn)軸強(qiáng)度的校核計(jì)算 12
3.3軸承強(qiáng)度的校核計(jì)算 14
4土豆挖掘機(jī)中主要零件的三維建模 15
4.1機(jī)架的三維建模 17
4.2挖掘鏟的三維建模 18
4.3擺臂的三維建模 20
4.4土豆挖掘機(jī)的三維建模 22
結(jié) 論 23
致 謝 24
參考文獻(xiàn) 25
III
1 緒論
1.1 課題的來源與研究的目的和意義
在英國，土豆挖掘設(shè)備等產(chǎn)業(yè)越來越多地將工場設(shè)在河邊，利用人工來對土豆進(jìn)行挖掘。在這樣的生產(chǎn)需要下，19世紀(jì)初出現(xiàn)了新型的土豆挖掘機(jī)，1965年，德國人費(fèi)倫斯發(fā)明了半自動(dòng)的土豆挖掘機(jī)，降低了人工的浪費(fèi)。1981年費(fèi)倫斯又創(chuàng)制出提供回轉(zhuǎn)動(dòng)力的土豆挖掘機(jī)，擴(kuò)大了土豆挖掘機(jī)的應(yīng)用范圍。土豆挖掘機(jī)的發(fā)明和發(fā)展，使土豆等類似食品的加工行業(yè)和工業(yè)生產(chǎn)都得以機(jī)械動(dòng)力化。土豆挖掘機(jī)幾乎是20世紀(jì)唯一的加工土豆的機(jī)械。
當(dāng)今社會(huì)，無論從挖掘數(shù)量、質(zhì)量、經(jīng)濟(jì)效益等各方面來衡量，此次設(shè)計(jì)的新型土豆挖掘機(jī)，它已經(jīng)遠(yuǎn)遠(yuǎn)超越了以往的傳統(tǒng)的土豆挖掘機(jī)，并成為各國爭相發(fā)展的行業(yè)。1986年江蘇的永趕公司實(shí)現(xiàn)了土豆挖掘機(jī)的創(chuàng)新設(shè)計(jì)，并通過打入亞洲以及南美市場，取得了不錯(cuò)的成績。從20世紀(jì)起，新型的土豆挖掘機(jī)不斷誕生，進(jìn)入20世紀(jì)，出現(xiàn)各種實(shí)驗(yàn)應(yīng)力分析方法，人們已能夠通過機(jī)電的有機(jī)結(jié)合設(shè)計(jì)出智能化的土豆挖掘機(jī)，相信在不久的將來，改機(jī)電一體化智能產(chǎn)品，將會(huì)得到越來越廣闊的應(yīng)用。土豆作為人們的日常的食品，是人們的生活的需要。為了實(shí)現(xiàn)土豆的自動(dòng)化挖掘，從而來代替?zhèn)鹘y(tǒng)的人工削皮來提供勞工效率，適應(yīng)現(xiàn)代化機(jī)械工業(yè)高速發(fā)展的需要，所以在機(jī)械設(shè)備中它們的挖掘設(shè)備的生產(chǎn)也有著嚴(yán)格的要求。傳統(tǒng)的土豆在沒有自動(dòng)挖掘設(shè)備而需要人工挖掘的情況下，挖掘效率低下，勞動(dòng)強(qiáng)度大，所以設(shè)計(jì)一個(gè)專用的土豆挖掘勢在必行。
通過對實(shí)際的生產(chǎn)設(shè)備進(jìn)行考察，從而提出了新型土豆挖掘機(jī)的結(jié)構(gòu)組成、工作原理，擬定了土豆挖掘機(jī)總的指導(dǎo)思想，得出了該新式土豆挖掘機(jī)的優(yōu)點(diǎn)是高效，經(jīng)濟(jì)且易維修的結(jié)論。
根據(jù)結(jié)合自身所學(xué)和本次所選課題的難易度，覺得無論是在知識層面還是在軟件的運(yùn)用技能上面，該課題很適合我，加之本課題來源于當(dāng)今社會(huì)機(jī)械工業(yè)土豆挖掘設(shè)備的創(chuàng)新和更新?lián)Q代基礎(chǔ)之上，通過設(shè)計(jì)出土豆挖掘機(jī)，從而來滿足當(dāng)今社會(huì)土豆挖掘設(shè)備不足的缺陷。
1.2 本課題研究的內(nèi)容
土豆作為人們的日常食物的一種，經(jīng)常出現(xiàn)在人們的餐桌上面。本次設(shè)計(jì)的土豆挖掘機(jī)主要是針對日常生活中見到的土豆來進(jìn)行的，由于該土豆挖掘機(jī)的挖掘鏟采用焊接的形式，其形狀采用鏟形，所以它的強(qiáng)度和結(jié)構(gòu)設(shè)計(jì)合理，并且能夠滿足對指定區(qū)域的土豆挖掘干凈的條件。
本次設(shè)計(jì)主要針對土豆挖掘機(jī)進(jìn)行設(shè)計(jì)，從土豆挖掘機(jī)的整體方案出發(fā)，然后具體細(xì)化出具體內(nèi)部結(jié)構(gòu)，其具體內(nèi)部結(jié)構(gòu)主要包括以下幾個(gè)方面：
1、到圖書館里查閱大量相關(guān)知識的資料，搜集出各類土豆挖掘機(jī)的原理及結(jié)構(gòu)，挑選相關(guān)內(nèi)容記錄并學(xué)習(xí)。
2、分析土豆挖掘機(jī)的結(jié)構(gòu)與參數(shù)
3、確定設(shè)計(jì)總體方案
4、確定具體設(shè)計(jì)方案（包括挖掘機(jī)構(gòu)的設(shè)計(jì)，V帶傳動(dòng)的設(shè)計(jì)，電機(jī)，軸承等的選型設(shè)計(jì)等等）
5、土豆挖掘機(jī)的三維圖的繪制、CAD裝配圖、零件圖的繪制。
6、說明書的整理
1.3 國內(nèi)外發(fā)展現(xiàn)狀
我們在2002來自于王健的以前的資料，他數(shù)十年的廢寢忘食建造了一個(gè)簡單的土豆挖掘機(jī)機(jī)構(gòu)，開純機(jī)械時(shí)代。王健更設(shè)計(jì)出多功能復(fù)合土豆挖掘機(jī)，在這之后，臺(tái)灣教授顏洪森以傳動(dòng)的土豆挖掘機(jī)為基礎(chǔ)，開發(fā)了一系列的土豆挖掘機(jī)，如四連桿式，六連桿式等等土豆挖掘機(jī)，查建中和其他人一起以凸輪機(jī)構(gòu)為對象，共同鉆研考慮怎樣改良按壓力引發(fā)的角度以及零部件的分理?？傊?，傳統(tǒng)的對象加上科學(xué)的分析和先進(jìn)的理論，使得土豆挖掘機(jī)在國內(nèi)的研究范圍和深度得到了極大的豐富和發(fā)展。
何人最先取得此項(xiàng)專利已無可知曉，只了解到外國科學(xué)家在十九世紀(jì)末建造出了一部類似于土豆挖掘機(jī)的機(jī)械，整體部分是用齒輪以及連接桿件機(jī)構(gòu)組裝，但是卻沒有做出實(shí)物來加以佐證.20世紀(jì)初又有人運(yùn)用齒輪以及連接桿件體系制造出類似的土豆挖掘機(jī)，然而相關(guān)資料中并沒有找到對這個(gè)作品的介紹，所以那個(gè)時(shí)候有關(guān)土豆挖掘機(jī)的研究還僅能思組成以及運(yùn)動(dòng)起來的規(guī)律。同期，又有兩位發(fā)明家麥吉以及弗蘭科創(chuàng)作了首部徹底用計(jì)算機(jī)操縱的土豆挖掘機(jī)。接下來幾年有關(guān)此機(jī)器的設(shè)計(jì)被充分的融入了運(yùn)行操縱理論。1979年席羅思在行進(jìn)土豆挖掘機(jī)里加入了操縱水平行走的儀器，同樣在腿上加入了保持和校對偏向的裝置。20世紀(jì)末布朗、羅布特以及莎普恩斯研究了加入了液壓部件和直流電機(jī)的相應(yīng)土豆挖掘機(jī)。這都意味著人類對機(jī)械體系的認(rèn)識已從簡單的考慮邁入了整體操縱、計(jì)算機(jī)和高新科技的相互融匯貫通的康莊大道。
從廣闊的視野、各種各樣的活動(dòng)，還有和學(xué)術(shù)報(bào)告、規(guī)范標(biāo)準(zhǔn)以及另外別的角度的的詳細(xì)內(nèi)容，我們得到了包含定位、性質(zhì)以及應(yīng)用土豆挖掘機(jī)的大環(huán)境。土豆挖掘機(jī)已發(fā)展到注重提高生產(chǎn)效率，成品質(zhì)量穩(wěn)定性。最近，超多的市場已經(jīng)建立了土豆挖掘機(jī)的商業(yè)用途，像土豆挖掘機(jī)，它的應(yīng)用已經(jīng)滲透到家庭家居生活等。出色的土豆挖掘機(jī)技術(shù)不僅實(shí)現(xiàn)創(chuàng)建一個(gè)新的市場，也為提高人們的生活水品做出了非常重要的貢獻(xiàn)。在一個(gè)國家或地區(qū)有土豆挖掘機(jī)具有普遍偏向的方式。今后，會(huì)更加流行正在蓬勃發(fā)展的土豆挖掘機(jī)。OMG國標(biāo)早就認(rèn)可中介范例，ISO資質(zhì)也授與了能減少勞動(dòng)力的土豆挖掘機(jī)。即使在大規(guī)模對土豆進(jìn)行挖掘的活動(dòng)，這是越來越多的土豆挖掘機(jī)的使用。根據(jù)土豆挖掘機(jī)技術(shù)應(yīng)用在通訊，家電，汽車，醫(yī)療設(shè)備和其他，土豆挖掘機(jī)已被廣泛認(rèn)可。它是一種動(dòng)力，看來像它會(huì)導(dǎo)致一個(gè)新的行業(yè)。土豆挖掘機(jī)研發(fā)情況固然都在被上述所整理，然而這些仍然是顯示出要把土豆挖掘機(jī)推向消費(fèi)者。歐美等發(fā)達(dá)國家成立有相應(yīng)計(jì)劃，本國也需求更好的戰(zhàn)略，方能維持積極地有力發(fā)展。新服務(wù)土豆挖掘機(jī)對于市場具有應(yīng)用性很強(qiáng)的領(lǐng)域，比如孜孜不倦的創(chuàng)新產(chǎn)品、醫(yī)療項(xiàng)目、相關(guān)福利以及防不勝防的自然性或人為性災(zāi)難。在另一方面，雖然產(chǎn)自日本的工業(yè)土豆挖掘機(jī)依然是行業(yè)里最好的，但其他國家都在奮起直追。在關(guān)于實(shí)際使用中，美國提出了很多觀點(diǎn)。在美國有建立國家計(jì)劃項(xiàng)目，歐洲也是，如Horizon2020，我們的國家也需要更好的政策，才能保持健康的發(fā)展前景。傳統(tǒng)的土豆挖掘機(jī)產(chǎn)品圖片如下圖1,2所示：
圖1
圖2
2 土豆挖掘機(jī)總體結(jié)構(gòu)的設(shè)計(jì)
2.1 土豆挖掘機(jī)的總體方案圖
土豆挖掘機(jī)屬于食品加工設(shè)備的一種，通常市面上用到的都是焊接框架式的，因?yàn)楹附涌蚣苁降耐炼雇诰驒C(jī)結(jié)構(gòu)強(qiáng)度足夠，其形狀很容易輕松地就將土豆從地里挖掘出來。該土豆挖掘機(jī)主要由機(jī)架、連接桿、擺臂、連接件、曲柄、抖動(dòng)輪、挖掘鏟、定位軸、地輪等等零部件組成。動(dòng)力是通過拖拉機(jī)帶動(dòng)該土豆挖掘機(jī)在農(nóng)田里面進(jìn)行自動(dòng)挖掘作業(yè)。該機(jī)效率高，產(chǎn)能好，適合批量挖掘土豆的場所。 其總體方案圖如下圖1-1所示：
1-1 土豆挖掘機(jī)總體方案圖
2.2 土豆挖掘機(jī)的工作原理
該土豆挖掘機(jī)主要由機(jī)架、連接桿、擺臂、連接件、曲柄、抖動(dòng)輪、挖掘鏟、定位軸、地輪等等零部件組成。動(dòng)力是通過拖拉機(jī)帶動(dòng)該土豆挖掘機(jī)在農(nóng)田里面進(jìn)行自動(dòng)挖掘作業(yè)。該機(jī)效率高，產(chǎn)能好，適合批量挖掘土豆的場所。
2.3 機(jī)械傳動(dòng)部分的設(shè)計(jì)計(jì)算
2.3.1 V帶傳動(dòng)的設(shè)計(jì)計(jì)算
（1）設(shè)計(jì)功率
＝1.2
P－傳遞的功率
（2）選定帶型
根據(jù)和選取普通V帶C型，－小帶輪轉(zhuǎn)速，為1350r/min
（3）傳動(dòng)比
1.76 ＝＝
（4）小帶輪基準(zhǔn)直徑（mm）
由B1表8－1－12和表8－1－14選定
＝100mm>＝75r/min
（5）大帶輪基準(zhǔn)直徑（mm）
由B3表8－7得=150mm
（6）帶速驗(yàn)算
（7）初定軸間距（mm）
（8）所需帶的基準(zhǔn)長度（mm）
＝
＝650mm
帶型選擇為A－900
（9）實(shí)際軸間距
（10）小帶輪包角
=
=
（11）單根V帶的基本額定功率
根據(jù)系統(tǒng)工況，我們可以取=0.37kw
（12）時(shí)單根V帶型額定功率增量
根據(jù)系統(tǒng)工礦，在這里我們?nèi)?0.15kw
（13）V帶的根數(shù)Z
Z =
－小帶輪包角修正系數(shù)取0.96
－帶長修正系數(shù)查取0.87
（14） 單根V帶的預(yù)緊力
=
=134（N）
m－V帶每米長的質(zhì)量（kg/m）查B1表8－1－24，取0.1k/gm
（15）作用在軸上的力
－考慮新帶初預(yù)緊力為正常預(yù)緊力的1.5倍
（16）帶輪的結(jié)構(gòu)和尺寸
帶輪是傳動(dòng)系統(tǒng)的傳動(dòng)組件之一，需要有足夠的剛度和強(qiáng)度才能滿足要求。根據(jù)系統(tǒng)的需求，我們可以選擇鑄鐵作為帶輪的材料，因?yàn)殍T鐵的強(qiáng)度和剛度方面度能夠滿足系統(tǒng)的需求。
帶輪的材料為HT200，查B1表8－1－10得基準(zhǔn)寬度制V帶輪輪槽尺寸，根據(jù)帶輪的基準(zhǔn)直徑查B1。
2.3.2軸承的設(shè)計(jì)計(jì)算
已知軸承預(yù)計(jì)壽命20×365×8=58400小時(shí)；
(1）已知nⅡ=458.2r/min?兩軸承徑向反力：FR1=FR2=500.2N；
初先兩軸承為深溝球軸承6208型。
根據(jù)課本P265（11-12）得軸承內(nèi)部軸向力FS=0.63FR則FS1=FS2=0.63FR1=315.1N；
(2)∵FS1+Fa=FS2Fa=0? 故任意取一端為壓緊端，現(xiàn)取1端為壓緊端
FA1=FS1=315.1N???FA2=FS2=315.1N；
(3)計(jì)算當(dāng)量載荷
P1、P2根據(jù)課本P263表（11-9）取f?P=1.5;根據(jù)課本P262（11-6）式得
P1=fp(x1FR1+y1FA1)=1.5×(1×500.2+0)=750.3N；?
P2=fp(x2FR1+y2FA2)=1.5×(1×500.2+0)=750.3N；?
(4)軸承壽命計(jì)算
∵P1=P2故取P=750.3N；?
∵深溝球軸承 ε=3；
2.3.3軸的設(shè)計(jì)
軸作為機(jī)器的一個(gè)關(guān)鍵組成部分，其為各類傳動(dòng)部件的安裝，傳動(dòng)的扭矩和旋轉(zhuǎn)運(yùn)動(dòng)圍繞軸進(jìn)行，而且經(jīng)過軸承和機(jī)架連接。為了滿足定位軸上的緊固件和容易加工和裝配的軸類零件和拆卸，通常軸設(shè)計(jì)成階梯軸。軸系的零件是由軸和它上邊的零部件構(gòu)成一個(gè)裝配體系，研究軸的過程中不僅要研究軸體自己的數(shù)據(jù)，還要將系統(tǒng)里的全部零部件融合在一起。
因?yàn)橛糜谡駝?dòng)的傳遞的軸體不僅要傳送扭矩，還得經(jīng)受住彎矩，是以本人研究的階梯性軸是轉(zhuǎn)動(dòng)軸。因?yàn)榇_定了小帶輪的參數(shù)，相應(yīng)的大帶輪隨之確定。接下來的工作就是計(jì)算軸體的直徑了。軸體的研究需要憑借扭轉(zhuǎn)強(qiáng)度來調(diào)整彎曲的強(qiáng)度，因?yàn)榭捎米鬏S的原料比較多，所以必須得明確軸的應(yīng)用環(huán)境，還有規(guī)定諸如剛度，強(qiáng)度以及別的機(jī)構(gòu)機(jī)能?？梢允褂脽崽幚磉@種方法，當(dāng)然也要琢磨怎樣使加工簡單并且花費(fèi)較少，用研究計(jì)算所得的數(shù)據(jù)以確定軸體的用料，故采取45號鋼當(dāng)成軸體的原料，它需要40MPa的切應(yīng)力。然后需要做正火或者調(diào)質(zhì)處理來確保它的力學(xué)性能。
由前知：卷筒上傳遞的功率是12.9kw，轉(zhuǎn)速n=3.9m/min，選用鋼，為保證其機(jī)械性能，應(yīng)進(jìn)行調(diào)試處理。
軸徑的初步估算
估算公式：
d≥A0 式中A0是與材料有關(guān)的系數(shù)，查[1]P表15-3 得A0=108
d≥A0=108×=15.76 圓整，取d=16mm
由于此軸是固定心軸，受力情況并不嚴(yán)重。因此，接上式估算的軸徑可作為軸的最大直徑。參考現(xiàn)有同類產(chǎn)品，取最小軸徑d=15mm。
（1）確定軸上零件的布置方式。為使結(jié)構(gòu)緊湊，并考慮具體的工藝性和強(qiáng)度要求，將大齒輪與卷筒一側(cè)對稱地安裝在軸頸處。即大齒輪在卷筒右側(cè)，通過鍵與卷筒固聯(lián)在一起。軸承兩端裝有軸承蓋，內(nèi)有檔油板和密封圈。軸承蓋用螺釘M1220與卷筒固定在一起。
（2）根據(jù)工藝和強(qiáng)度要求把軸制成階梯形，這樣可以使軸上零件定位可靠并且拆裝方便。
3 各主要零部件強(qiáng)度的校核
3.1機(jī)架強(qiáng)度的校核與計(jì)算
機(jī)架的選擇根據(jù)整個(gè)系統(tǒng)的總重量來定，方管機(jī)架受力分析得出，由分析得出底架在平衡狀態(tài)下只受地面對其的支撐力和在其表面上物體所給的壓力。見下圖：
即物料和底架上面的所有零部件等等給的壓力為G=20000N（10000Kg）+(1000X20N)=30000N;
根據(jù)方管承載力計(jì)算公式：
M=Pac/L
（僅用于截面)
f=M/W≤材料的許用應(yīng)力（彈性抗拉強(qiáng)度/安全系數(shù)）。
M=Pac/L=11960xL，本次設(shè)計(jì)初定L為1200mm
則M=13456N.M
，初定方管為40x40x5。計(jì)算W得出
折算后位270Mpa
查的普通碳素結(jié)構(gòu)鋼Q235A的抗拉強(qiáng)度為375~500Mpa，由于270Mpa遠(yuǎn)遠(yuǎn)小于375Mpa，所以初定方管滿足要求。
3.2轉(zhuǎn)軸強(qiáng)度的校核計(jì)算
受力分析：卷筒部件的大齒輪和卷筒未與軸直接接觸，但其上的力通過軸承傳遞到了主軸上。因此，主軸所受軸承的力與卷筒所受軸承的力大小相等方向相反。另外，主軸兩端還受兩個(gè)支承架的支承力。若考慮重力的作用，主軸還受卷筒部件的重壓作用。
軸的空間受力圖：
O
X
y
z
圖3-2 軸的空間受力圖
由前知：R =392N，R=24500N；R=31642N，R35874N，估計(jì)卷筒重量約為154公斤，則G=1509N。將軸上作用力分解為水平面受力圖和垂直面受力圖，求出水平面上和垂直面上的支承點(diǎn)反作用力，并畫出彎矩圖：
支反力：
根據(jù)平衡方程R+R=R+G+R
R．64+G．236+R．408=R．472
解得，R=5383.8N，R=28159.2N
彎矩圖：
圖3-3 彎矩圖
YX面受力圖：
支反力：
根據(jù)平衡方程 R′+R′=R′+R′
R′．64+R′．408=R′．472
解得，R′=26042.2N， R′=34331.8N
彎矩圖：
圖3-4 彎矩圖
合成彎矩圖M=
圖3-5 合成彎矩圖
對照結(jié)構(gòu)圖，分析合成彎矩圖，可知主軸較危險(xiǎn)的三個(gè)部面分別是：中間軸頸110的右端面Ⅰ，右端面軸承的中間部面Ⅱ，右端軸頸的左端面Ⅲ。（主軸結(jié)構(gòu)圖）。
這三個(gè)合成彎矩分別是：
M=
=
=2669644
M=2841782.4
M=
=
=1243279.8
因?yàn)棰?、Ⅱ處的截面直徑相同，M＞ M，只需驗(yàn)算M就行了。
直徑校核：
心軸的截面尺寸是根據(jù)彎曲強(qiáng)度來計(jì)算。其危險(xiǎn)截面的尺寸可按下式確定。
d=
式中，M——最大彎矩
[]——許用彎曲應(yīng)力
——對于實(shí)心軸=0，對于空心軸=，d：軸內(nèi)徑，d：軸外徑，對于卷筒主軸，查[Ⅰ]P，45鋼，=355MP。取安全系數(shù)n=2.0，則[]===177.5 MP。主軸是實(shí)心軸，=0。
∴d≥。
則d===53.18mm＜75mm
d===54.29mm＜85mm
由以上計(jì)算可以看出，主軸強(qiáng)度足夠。
3.3軸承強(qiáng)度的校核計(jì)算
3.3.1滾動(dòng)軸承的選擇
滾動(dòng)軸承為雙列圓錐滾子軸承350324B，由文獻(xiàn)[2]表得KN，KN，，。
3.3.2壽命驗(yàn)算
軸承所受支反力合力
N （4.1）
對于雙列圓錐滾子軸承，派生軸向力互相抵消。
，N
由文獻(xiàn)[2]表得， ，
N （4.2）
按軸承B的受力大小驗(yàn)算
h （4.3）
h=年
由于拖拉機(jī)減速箱的運(yùn)轉(zhuǎn)平穩(wěn)，必須選擇較大壽命的軸承，軸承能達(dá)到所計(jì)算的壽命。
經(jīng)審核后，此軸承合格。
4 土豆挖掘機(jī)中主要零件的三維建模
4.1機(jī)架的三維建模
4-1 機(jī)架
4.2挖掘鏟的三維建模
4-2 挖掘鏟
4.3擺臂的三維建模
4-3 主動(dòng)齒輪
4.4土豆挖掘機(jī)的三維建模
4-4 土豆挖掘機(jī)
結(jié) 論
到如今，畢業(yè)設(shè)計(jì)總算接近尾聲了，通過這次對于土豆挖掘機(jī)的設(shè)計(jì)，使我們充分把握的設(shè)計(jì)方法和步驟，不僅復(fù)習(xí)所學(xué)的知識，而且還獲得新的經(jīng)驗(yàn)與啟示，讓我收益頗多。特別是針對機(jī)械的機(jī)構(gòu)設(shè)計(jì)這部分，我感觸最深。對于次次設(shè)計(jì)的土豆挖掘機(jī)，主要的傳動(dòng)的機(jī)構(gòu)是齒輪傳動(dòng)，針對這個(gè)機(jī)構(gòu)的設(shè)計(jì)，我花費(fèi)了較多時(shí)間和精力，通過查找相關(guān)的齒輪傳動(dòng)的設(shè)計(jì)資料以及土豆挖掘機(jī)的相關(guān)問題來確定齒輪的模數(shù)和齒數(shù)，以及齒輪的內(nèi)孔的設(shè)計(jì)，直到最后齒輪的強(qiáng)度校核部分。經(jīng)過這個(gè)過程的學(xué)習(xí)和設(shè)計(jì)，讓我印象尤為深刻。
在以后的工作中，我相信我還會(huì)遇到很多類似的問題，但是有了這次的學(xué)習(xí)和設(shè)計(jì)經(jīng)歷，我想我已經(jīng)初步具備了設(shè)計(jì)一個(gè)機(jī)械設(shè)備的能力，我已經(jīng)做好了準(zhǔn)備，在以后的工作中，邊工作邊學(xué)習(xí)，爭取在工作中提高，在工作中學(xué)習(xí)，爭取做一個(gè)對于社會(huì)，對家庭有用的人。
通過本次設(shè)計(jì),讓我學(xué)習(xí)到了許多知識，特別是對傳動(dòng)機(jī)構(gòu)的應(yīng)用方面，是我收獲最大的地方。本次的設(shè)計(jì)的傳動(dòng)機(jī)構(gòu)包含了齒輪傳動(dòng)機(jī)構(gòu)這一最典型的機(jī)構(gòu)，通過查找與它相關(guān)的設(shè)計(jì)資料，到計(jì)算帶動(dòng)筒體轉(zhuǎn)動(dòng)所需要在輸出扭矩從而對齒輪機(jī)構(gòu)進(jìn)行設(shè)計(jì)，包括傳動(dòng)帶輪的選型，例如帶型，帶寬的確定以及之后的軸承強(qiáng)度校核部分的設(shè)計(jì)，都花費(fèi)了我好多精力。同時(shí)，也讓我學(xué)到了好多知識。
在相關(guān)的實(shí)際問題的討論中，我的導(dǎo)師總是孜孜不倦的引導(dǎo)著我，幫助著我。每周一次的進(jìn)度檢查和問題討論，促使我在正確的道路上大步前進(jìn)，不僅工作的按時(shí)保質(zhì)保量的完成得到了保證，我本人的研究能力，工作的態(tài)度也得到了充分的鍛煉和提高。這些寶貴的品質(zhì)影響著我，毫無疑問，它們對我以后的工作，學(xué)習(xí)，生活都會(huì)起到深遠(yuǎn)而長久的良好影響。也能為人生打下一個(gè)夯實(shí)地基礎(chǔ)！
在具體的研究設(shè)計(jì)過程中，同學(xué)們也在平日的學(xué)習(xí)與生活中提供了無私與周到的幫助，充分用他們的工作熱情感染著我，鼓勵(lì)著我，讓我少走了很多彎路，再次一并致謝！另外也感謝我的父母，朋友和同學(xué)們的幫助。在做設(shè)計(jì)感覺受挫，枯燥與迷茫時(shí)，是他們在悉心的為我釋放壓力，鼓勵(lì)我不要?dú)怵H，勇敢面對。每周一次和父母的通話，與朋友和同學(xué)的長談后都使我精神放松，斗志倍增，以飽滿的熱情重新投入到工作中去，感謝他們，正是他們的不懈支持和充分理解才能使我順利完成畢業(yè)設(shè)計(jì)。
最后，感謝學(xué)校各位領(lǐng)導(dǎo)與老師給了我在濱海學(xué)院學(xué)習(xí)生活四年以及參加這次畢業(yè)設(shè)計(jì)的寶貴的鍛煉機(jī)會(huì)，它使我深刻認(rèn)識到在知識的汪洋大海面前我是多么無知和微不足道。這是一個(gè)最好的時(shí)代，也是尊重知識，充分學(xué)習(xí)知識，掌握知識的時(shí)代。只有持續(xù)的不間斷地學(xué)習(xí)，才不會(huì)在激烈的競爭中落后于別人，也才能用自己的真才實(shí)學(xué)為社會(huì)做出自己應(yīng)有的貢獻(xiàn)。知識是無止境的，無價(jià)的，我愿在求真的道路上下而求索！
致 謝
時(shí)間過得很快，論文總算完成了，我的心里感到特別高興和激動(dòng)，在這里，我打心里向我的導(dǎo)師和同學(xué)們表示衷心的感謝！因?yàn)橛辛死蠋煹恼佌伣虒?dǎo)，才讓我學(xué)到了很多知識和做人的道理，由衷地感謝我親愛的老師，您不僅在學(xué)術(shù)上對我精心指導(dǎo)，在生活上面也給予我無微不至的關(guān)懷支持和理解，在我的生命中給予的靈感，所以我才能順利地完成大學(xué)階段的學(xué)業(yè)，也學(xué)到了很多有用的知識，同時(shí)我的生活中的也有了一個(gè)明確的目標(biāo)。知道想要什么，不再是過去的那個(gè)愛玩的我了。導(dǎo)師嚴(yán)謹(jǐn)?shù)闹螌W(xué)態(tài)度，創(chuàng)新的學(xué)術(shù)風(fēng)格，認(rèn)真負(fù)責(zé)，無私奉獻(xiàn)，寬容豁達(dá)的教學(xué)態(tài)度都是我們應(yīng)該學(xué)習(xí)和提倡的。通過近半年的設(shè)計(jì)計(jì)算，查找各類土豆挖掘機(jī)的相關(guān)資料，論文終于完成了，我感到非常興奮和高興。雖然它是不完美的，是不是最好的，但在我心中，它是我最珍惜的，因?yàn)槲沂窃趺聪氲?，這是我付出的汗水獲得的成果，是我在大學(xué)四年的知識和反映。四年的學(xué)習(xí)和生活，不僅豐富了我的知識，而且鍛煉了我的個(gè)人能力，更重要的是來自老師和同學(xué)的潛移默化讓我學(xué)到很多有用的知識，在這里，謝謝老師以及所有關(guān)心我和幫助我的人，謝謝大家。
參考文獻(xiàn)
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[2]何發(fā)昌著，邵遠(yuǎn)編著.土豆挖掘機(jī)的原理.北京：高等教育出版社，1996：77-80
[3]張利平著. 實(shí)用技術(shù)速查手冊. 北京：化學(xué)工業(yè)出版社，2006.12：15-18
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Effectiveness assessment of agricultural machinery based on fuzzy sets theoryRajko Miodragovic a, Milo Tanasijevic b, Zoran Mileusnic a, Predrag Jovanc ic baUniversity of Belgrade, Faculty of Agriculture, SerbiabUniversity of Belgrade, Faculty of Mining and Geology, Serbiaa r t i c l ei n f oKeywords:Agricultural machineryEffectivenessFuzzy setMaxmin compositiona b s t r a c tThe quality of service of agricultural machinery represents one of the basic factors for successful agricul-tural production. In this sense, there is a clear need for defining the exact indicator of the quality of thesemachines, according to which it could be possible to determine which machine is optimal for differentworking conditions. The concept of effectiveness represents one of synthesis indicators of the qualityof service of the technical systems. In this paper the effectiveness is defined using the fuzzy set theory,and reliability, maintainability and functionality are used as influence indicators of the effectiveness.In that sense the model for assessing the effectiveness of tractor as a typical representative of agromachinery has been formed. The model is based on integration of linguistic description of the above men-tioned influence indicators using fuzzy set theory and maxmin composition. The model was tested onthe example of three tractors of the same category, which are exploited in climatic and soil conditionsin the wider Belgrade (Serbia) area. Even if the conditions in this experiment were approximately equal,the difference of the achieved effects was attained and very significant, compared to other operationparameters.? 2012 Elsevier Ltd. All rights reserved.1. IntroductionRapid expansion of global demands for agricultural products hascaused much greater development of agricultural technique, apro-pos machines and equipments. It is widely recognized that contem-porary agricultural systems demand careful and detailed planningand control of all relevant biological, technical, technological andother processes. An accurate and reliable predicting of the final out-come for each specified operation, as well as for the complete cropproductionprocess,isofspecialimportance.Demandshaveintensi-fied the introduction of sophisticated experimental, mathematical,statistical, mechanical and other methods in agricultural sciencesduring the last few decades. Besides the demands described above,anadequatetechnicalsystemhastosatisfythecriteriaofproductiv-ity, imposed by the conditions of desired crop production. In mostcases, the capacity of tractor-machinery systems on farms in Serbiais much over the optimal level (Nikolic , 2005), increasing the costsof crop production.Nowadays, the existing mathematical optimiza-tion methods, supported by the high-performance computers, canefficiently resolve the optimization problems (Dette & Weber,1990; Duffy et al., 1994; Mileusnic , 2007; etc.). The formation ofan optimal technical system in order to produce cheaper food,highly impacted reliability of tractors, its maintainability, and thefunctionality of the system.With the beginning of systems sciences development, practicallyafter the II World War, in appropriate engineering and scientific liter-ature a series of concepts have been defined, with the idea to describeessential characteristics of technical systems from the point of theirquality of service. Reliability as the indicator of technical systembehaviors in operation, and maintainability as the indicator of techni-cal system behaviors during the period of failures can be stated as themost recognizable concepts. These two concepts and their implemen-tations had the most progressive development. The concept of effec-tiveness was defined later in attempt to describe simultaneouslytechnicalsystemsbehaviorsinoperationandinperiodsoffailure.Thisconceptconsideredreliabilityandavailabilityperformances,aswellasfunctionalityofproposedtechnicalsystemdesign(Papic&Milovanovic,2007). In other words, the effectiveness of a technical system can bearticulatedasprobabilitythatatechnicalsystemwillbeputinfunc-tionsuccessfullyand performrequiredcriterionfunctionwithinthelimits of allowed discrepancies for given time period and given sur-rounding conditions. Although in the same spirit, some authors havedefined effectiveness somewhat differently. In (Ebramhimipour &Suzuki, 2006) effectiveness was defined as overall indicator whichcontains efficiency, reliability and availability. These two citeddefinitionsinclude parallelconcerningofreliabilityandavailability,althoughavailabilityincludesreliabilityandmaintainability(Ivezic ,Tanasijevic ,&Ignjatovic ,2008).Thereforeitcanbeagreeduponthatthe effectivenessis influenced by reliability, maintainability and func-tionality. Reliability is defined as characteristic of a system to contin-uouslykeepoperatingabilitywithinthelimitsofalloweddiscrepancies0957-4174/$ - see front matter ? 2012 Elsevier Ltd. All rights reserved.doi:10.1016/j.eswa.2012.02.013Corresponding author.E-mail address: tanrgf.bg.ac.rs (M. Tanasijevic ).Expert Systems with Applications 39 (2012) 89408946Contents lists available at SciVerse ScienceDirectExpert Systems with Applicationsjournal homepage: the calendar period of time; maintainability as capacity of thesystemforpreventionandfindingfailuresanddamages,forrenewingoperating ability and functionality through technical attending andrepairs; and functionality as the degree of fulfilling the functionalrequirements, namely the adjustment to environment, or more pre-cisely to the conditions in which the system operates.In the case of monitoring reliability and maintainability it iscommon to monitor the time picture of state (Fig. 1) according towhich the functions of reliability and maintainability can be deter-mined, as well as the mean time in operation and the mean time infailure.The main problem that occurs in forming the time picture ofstate is data monitoring and recording. In real conditions the ma-chines should be connected to information system which wouldprecisely record each failure, duration and procedure of repair. Thisis usually expensive and improvised monitoring of the machineperformance, namely of its shut downs, is imprecise. Moreover,statistical data processing provided by the time picture of the staterequires that all machines work under equal conditions, which isdifficult to achieve. As for the functionality of the technical system,there is no common way for its measuring and quantification. Thisis the reason why in this paper, in order to assess the effectiveness,expertise judgments of the employed in the working process of theanalyzedmachineswillbeused.Applicationofexpertisejudgments has been largely used in literature, primarily for dataprocessing and the assessment of the technical systems in termsof: risk (Li & Liao, 2007), safety (Wang 2000; Wang, Yang, & Sen,1995) or dependability (Ivezic et al., 2008; Tanasijevic, Ivezic,Ignjatovic, & Polovina, 2011). Expertise judgment is naturally givenin linguistic form. Thereby, as the logical mathematical andconceptual model for processing the expertise judgments, namelyfor calculating with linguistic descriptions, the fuzzy set theorywas used (Klir & Yuan, 1995; Zadeh, 1996). Application of fuzzysets today represents one of the most frequently used tools forsolving the problems in various areas of optimization (Huang,Gu, & Du, 2006) andidentification (Chan, 1996) regardingengineering problems. Cai (1996) presents the overview of variousapplication aspects of fuzzy methodology in systemfailureengineering, which is a problem close to effectiveness assessment.Application of fuzzy logic theory and experts systems (Liao,2011; Liebowitz, 1988) in general is also used for solving theoptimizations problems from area of agro machinery. In article(Rohani, Abbaspour-Fard, & Abdolahpour, 2011) on the base ofneural networks application, failures on tractors were predicted.In article (Ye, Yu, & Zhao, 2010) fuzzy mathematics, reliabilitytheory and multi-objective optimization technology were appliedto design tractors final transmission. Predictability of machinedowntimes and reliability, significantly depends on its effective-ness of technical systems.The idea of this paper is to establish the model for effectivenessdetermination according to fuzzy sets theory utilization. Therebythe fuzzy sets were used to analyze reliability, maintainabilityand functionality performances (partial indicators of effectiveness)as well as for their integration into effectiveness. In this way effec-tive model for the quality assessment of the technical systems intheir working conditions is obtained. The model can be used as cri-teria for decision making related to any procedure in purchasing,operation or maintenance of the system, for prediction of repairand maintenance costs. Quality and functionality of the proposedmodel is shown in effectiveness determination of agriculturalmachinery, precisely tractors.2. Effectiveness performance assessment based on fuzzy setstheoryMathematical and conceptual model of effectiveness assess-ment is practically summarized in two steps: fuzzy propositionof effectiveness partial indicators; and fuzzy composition of men-tioned indicators into one synthesized. Fuzzy proposition is pro-cedure for representing the statement that includes linguisticvariables based on available information about considered techni-cal system. In that sense it is necessary to define the names of lin-guistic variables that represent different grades of effectiveness ofconsidered technical system and define the fuzzy sets that describethe mentioned variables. Composition is a model that providesstructure of indicators influences to the effectiveness performance.2.1. Fuzzy model of problem solvingThe first step in the creation of fuzzy model for effectiveness (E)assessment is defining linguistic variables related to itself and toreliability (R), maintainability (M) and functionality (F). Regardingnumber of linguistic variables, it can be found that seven is themaximal number of rationally recognizable expressions that hu-man can simultaneously identify (Wang et al., 1995). However,for identification of considered characteristics even the smallernumber of variables can be useful because flexibility of fuzzy setsto include transition phenomena as experts judgments commonlyis (Ivezic et al., 2008). According to the above, five linguistic vari-ables for representing effectiveness performances are included:poor, adequate, average, good and excellent. Form of these linguis-tic variables is given as appropriate triangular fuzzy sets (Klir &Yuan, 1995), and they are presented in Fig. 2.In Fig. 2, j = 1,.,5 practically represents measurement units ofeffectiveness.Thereby, partial indicators of effectiveness: R, M and F, pre-sented as membership functionl:lR l1R;.;l5R;lM l1M;.;l5M;lF l1F;.;l5F1In the next step, maxmin composition is performed on them. Maxmin composition, also called pessimistic, is often used in fuzzy alge-bra as a synthesis model (Ivezic et al., 2008; Tanasijevic et al., 2011;Wang et al., 1995; Wang 2000). The idea is to make overall assess-ment (E) equal to the partial virtual representative assessment. Thisassessment is identified as the best possible one between the worstpartial grades expected (R, M or F).It can be concluded that all elements of (R, M and F) that makethe E have equal influence on E, so that maxmin composition willbe used, which in parallel way treats the partial ones onto theFig. 1. Time picture of state, t time spent in operation,s time in failure, h time of planned shut down due to preventive maintenance.R. Miodragovic et al./Expert Systems with Applications 39 (2012) 894089468941synthetic indicator. In literature (Ivezic et al., 2008; Wang et al.,1995) maxmin compositions which by using operators ANDand OR provide an advantage to certain elements over the othersin the process of synthesis, are also used.Precisely, if we look at three partial indicators, namely theirmembership function (1), it is possible to make C = j3= 53combina-tions of their membership functions. Each of these combinationsrepresents one possible synthesis effectiveness assessment (E).E lj1;.;5R;lj1;.;5M;.;lj1;2;.5Fhi;for all c 1 to C2If we take into account only values iflj1;.;5R;M;F 0, we get combina-tions that are named outcomes (o = 1 to O, where O # C).Further, for each outcome its values are calculated (Xc). Theoutcome which would suit the combination c, it would be calcu-lated following the equations:XcPR;M;Ejhic33Finally, all of these outcomes are treated with maxmin composi-tion, as follows:(i) For each outcome search for the MINimum value oflR,M,Finvector Ec(2). The minimum which would suit the combina-tion o, it would be calculated following the equations:MIN0 minflj1;.;5R;lj1;.;5M.;lj1;.;5Fg;for all o 1 to O4(ii) Outcomes are grouped according to their valuesXc(3),namely the size of j.(iii) Find the MAXimum between previously identified mini-mums (i) for each group (ii) of outcomes. The maximumwhich would suit value of j, would be calculated followingthe equations:MAXj maxfMINog; for every j5E assessment of technical system is obtained in the form:lE MAXj1;.;MAXj5 l1E;.;l5E6This expression (6) is necessary to map back to the E fuzzy sets(Fig. 2). Best-fit (Wang et al., 1995), method is used for transforma-tion of E description (6) to form that defines grade of membershipto fuzzy sets: poor, adequate, average, good and excellent. This pro-cedure is recognized as identification. Best-fit method uses distance(d) between E obtained by maxmin composition (6) and each ofthe E expressions (according to Fig. 2), to represent the degree towhich E is confirmed to each of fuzzy sets of effectiveness (Fig. 2).diEj;Hi ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiX5j1ljE ?ljHj2vuut;j 1;.;5;Hi fexcellent;goodaverage;adequate;poorg7where is (according to Fig. 2):lexc.= (0,0,0,0.25,1);lgood= (0,0,0.25,1,0.25);laver.= (0,0.25,1,0.25,0);ladeq.= (0.25,1,0.25,0,0);lpoor= (1,0.25,0,0,0).The closerlE(6) is to the ith linguistic variable, the smaller diis.Distance diis equal to zero, iflE(6) is just the same as the ithexpression in terms of the membership functions. In such a case,E should not be evaluated to other expressions at all, due to theexclusiveness of these expressions.Suppose dimin(i = 1,.,5) is the smallest among the obtaineddistances for Ejand leta1,.,a5represent the reciprocals of the rel-ative distances (which is calculated as the ratio between corres-ponding distance di(7) and the mentioned values dimin). Then,aican be defined as follows:ai1di=dimin;i 1;.;58If di= 0 it follows thatai= 1 and the others are equal to zero. Then,aican be normalized by:biajP5m1aim;i 1;.;5X5i1bi 19Each birepresents the extent to which E belongs to the ith defined Eexpressions. It can be noted that if Eicompletely belongs to the ithexpression then biis equal to 1 and the others are equal to 0. Thus bjcould be viewed as a degree of confidence that Eibelongs to the ith Eexpressions. Final expression for E performance at the level of tech-nical system, have been obtained in the form (10)Eifbi1;poor;bi2;adequate;bi3;good;bi4;average;bi5;excellentg103. An illustrative exampleAs an illustrative example of evaluation of agriculture machin-ery effectiveness, the comparative analysis of three tractors A1B2,and C2is given in this article.In tractor A a 7.146 l engine LO4V TCD 2013 is installed. Thanksto the reserves of torque from 35%, the tractor is able to meet allthe requirements expected in the worst performing farming oper-ations in agriculture. Total tractor mass is 16,000 kg. According toOECD (CODE II) report maximum power measured at the PTO shaftis243 kWat2200 rpmwithspecificfuelconsumptionof198 g/kW h (ECE-R24). Maximum engine torque is 1482 Nm at en-gine regime of 1450 rpm. Transmission gear is vario continioustransmision. Linkage mechanism is a Category II/III with liftingforce of 11,800 daN.In tractors B2and C28.134 l engine 6081HRW37 JD is installed,with reserve torque of 40%, and this tractor was able to meet all therequirements expected in the worst performance of the farmingoperations in agriculture. Total tractor weight is 14,000 kg. Accord-ing to OECD (CODE II) report maximum power measured at thePTO shaft is 217 kW at 2002 rpm with specific fuel consumptionof 193 g/kW h (ECE-R24). Maximum torque is 1320 Nm at enginerevs of 1400 rpm. Transmission is AutoPower. Linkage mechanismis a Category II/III with lifting force of 10,790 daN.Both models have electronically controlled tractor engine andfuel supply system that meets the regulations on emissions.From the submitted technical characteristics of the tractor A, Band C it is seen that all three tractors are fully functional forFig. 2. Effectiveness fuzzy sets.1Tractor Fendt Vario 936.2Tractor John Deere 8520.8942R. Miodragovic et al./Expert Systems with Applications 39 (2012) 89408946performing difficult operations for different technologies of agri-cultural production. Tractors B and C have the same technical char-acteristics, and practice is the same type and model, except thatthe tractor B entered into operation in May 2007, a tractor C in June2007. A tractor on the experimental farm, which is the technicaldocumentation for the base model, comes into operation in July2009. The main task of maintaining agricultural techniques is toprovide functionality and reliability of machines. Maintenance ofall three tractors is done by machine shop owned by the user up-grade option.Ten engineers (analysts) working on maintenance and opera-tion of tractors were interviewed. Their evaluation of R, D and Fare given in Table 1.First, the effectiveness of tractor A is calculated. It can be seenthat the reliability was assessed as excellent by six out of ten ana-lysts (6/10 = 0.6), as average by three (0.3) and as good by one(0.1). In this way the assessment R is obtained in the form (11):R 0:6=exc; 0:3=good; 0:1=aver; 0=adeq; 0=poor11In the same way the assessments for M and F are obtained:M 0:4=exc; 0:4=good; 0:2=aver; 0=adeq; 0=poorF 0:5=exc; 0:5=good; 0=aver; 0=adeq; 0=poorIn the next step, these assessments are mapped on fuzzy sets (Fig. 1)in order to obtain assessment in the form (1). For example, Reliabil-ity in this example is determined as (11), where it is to linguisticvariable excellent joined weight 0.6. Thereby, fuzzy set excellentis defined as: Rexc= (1/0, 2/0, 3/0, 4/0.25, 5/1.0) (according toFig. 1). In this way the specific values of fuzzy set excellentRexc0.6= (1/(0 ? 0.6),2/(0 ? 0.6),3/(0 ? 0.6),4/(0.25 ? 0.6),5/(1.0 ? 0.6) are obtained. The remaining four linguistic variablesare treated in the same way. In the end for each j = 1,.,5 specificmembership functions (last row, Table 2) are added into the finalfuzzy form (1) of tractor A reliability:lRA 0;0:025;0:175;0:475;0:675In the same way, based on the questionnaire (Table 1) values formaintainability and functionality are obtained:lMA 0;0:05;0:3;0:55;0:5;lFA 0;0;0:125;0:625;0:62512These fuzzificated assessments (11) and (12) are necessary to syn-thesize into assessment of effectiveness, using maxmin logics. Inthis case it is possible to make C = 53= 125 combinations, out ofwhich the 48 outcomes. First outcome would be for combination2-2-3: E2-2-3= 0.025,0.05,0.125, where isX2-2-3= (2 + 2 + 3)/3 = 2(rounded as integer). Smallest value among the membership func-tions of this outcome is 0.025. Other outcomes and correspondingvalues ofXcare shown in Table 3. All these outcomes can begrouped around sizesX= 2, 3, 4 and 5.For example, for outcomeX= 5 it can be written:E4?5?5 0:475;0:5;0:625?;E5?4?5 0:675;0:55;0:625?;E5?5?4 0:675;0:5;0:625?;E5?5?5 0:675;0:5;0:625?Further, for each of them, minimum between membership functionis sought:Table 1Results of questionnaire.AnalystLinguistic variablesTractor ATractor BTractor CExcellentGoodAverageAdequatePoorExcellentGoodAverageAdequate
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