第1章緒 第2章懸架系統(tǒng)方案設(shè) 第3章懸架系統(tǒng)參數(shù)設(shè)計(jì)及計(jì) 第4章懸架系統(tǒng)建模與仿真分 ADAMS/Car模塊總 中英文翻 1緒運(yùn)動(dòng)是發(fā)展至今已有100多年的歷史，早在1894年，在法國(guó)黎舉辦了世界第一次運(yùn)動(dòng)，當(dāng)時(shí)僅有16輛汽車參加了比賽。比賽中基本沒談到運(yùn)動(dòng)，不得不說的就是F1。作為世界頂級(jí)水平的比賽，F(xiàn)11， （FIA國(guó)際汽聯(lián)舉辦了第一次世界錦標(biāo)賽，60多年來吸引了數(shù)百萬觀眾現(xiàn)場(chǎng)觀戰(zhàn)，電視觀眾更是接近500億人次，由此可見，人們對(duì)運(yùn)動(dòng)高速刺激的喜愛，進(jìn)而促進(jìn)了對(duì)上的汽車前沿技術(shù)的研究。近些年來，一項(xiàng)由汽車工程學(xué)會(huì)（SoietyfoEnginering,SE)主辦的比（FrmulaSEFS)逐漸興起它是一項(xiàng)由大學(xué)生參與設(shè)計(jì)的比賽由學(xué)生組成設(shè)計(jì)團(tuán)隊(duì)將會(huì)全程完成在美、德、日等國(guó)家每年都有舉辦比賽，2006年的南臺(tái)科技大學(xué)FSE車隊(duì)赴參加比賽2007年湖南大學(xué)FSE車隊(duì)參加了的比賽時(shí)隔三年，在我國(guó)國(guó)內(nèi)首次也開展了此項(xiàng)比賽即學(xué)生方程式比賽這使得賽車運(yùn)動(dòng)更貼近學(xué)生的生活。所有參賽隊(duì)伍成員需要在大約8到12個(gè)月定規(guī)則并順利完成各項(xiàng)測(cè)試項(xiàng)目的在整個(gè)設(shè)計(jì)過程中隊(duì)員們可以獲得穩(wěn)定性有著直接的關(guān)系懸架的設(shè)計(jì)影響著汽車的整車性能對(duì)于同。只有擁有自主研發(fā)能力，才能在市場(chǎng)中立足作為汽車尖端科技體現(xiàn)，同樣需要獲得業(yè)內(nèi)的足夠重視。自2004年在舉辦國(guó)際汽聯(lián)一級(jí)方程式世界錦標(biāo)賽，F(xiàn)1進(jìn)入中國(guó)已有十余年，但始終沒有中國(guó)車隊(duì)加入F1運(yùn)動(dòng)，究其原因，F(xiàn)1要求的底盤必須由車隊(duì)自主研發(fā)。中國(guó)在。。本文主要介紹了小型懸架系統(tǒng)的選型設(shè)計(jì)過程和過程不同于一般汽車考慮到實(shí)際運(yùn)動(dòng)過程以及各參數(shù)對(duì)汽車性能影響對(duì)賽。來越深入。1956年，線性二自由度懸架的數(shù)學(xué)模型首先被賽格爾創(chuàng)建，引起架動(dòng)力學(xué)發(fā)展一段時(shí)間后，在1970年前后，和的技術(shù)人員分別構(gòu)建整車穩(wěn)定性的影響[4]。配合著理論上的研究深入，輔助分析計(jì)算方法也逐2060年代末的福特汽車公司在開發(fā)輕型車的工程中利用ADAMS技術(shù)對(duì)在方面，近年來在FSAE比賽中，國(guó)外各高校設(shè)計(jì)懸架時(shí)有著自己獨(dú)特的設(shè)計(jì)方案與方法。2002年，勞倫斯科技大學(xué)車隊(duì)采用拉式不等長(zhǎng)雙橫臂懸架，使整車重心有所降低，對(duì)車架內(nèi)部空間充分利用。把的持久、安全可作為懸架設(shè)計(jì)重點(diǎn)通過多種計(jì)算機(jī)輔助軟件完成了對(duì)懸架各部件的設(shè)計(jì)并對(duì)各部件在不同的負(fù)載條件下所受的最大應(yīng)力和進(jìn)行了有限2005年澳大利亞南昆士蘭大學(xué)的懸架設(shè)計(jì)過程在文獻(xiàn)[6]中有所表述，2005年巴西圣保羅大學(xué)前后懸架均選用推式不等長(zhǎng)雙橫臂懸架員首先選擇滿足比賽要求的輪胎，然后設(shè)計(jì)與輪胎相符合的懸架。用CAD軟后調(diào)整懸架幾何形狀改變彈簧的剛度以及選擇合適的阻尼器改善性[7]2008年，希臘亞里士多德大學(xué)前后懸架均選用推式不等長(zhǎng)雙橫臂懸。80年代。在之后的研究中，最具代表性的是工程院郭孔輝所著的《汽車動(dòng)力學(xué)，書中從側(cè)向力、縱向力轉(zhuǎn)向的角度對(duì)汽車懸架做出了系統(tǒng)的分析[9]。1997我國(guó)首個(gè)汽車動(dòng)態(tài)模擬建立利用它可以完成人-車-環(huán)境形成的封閉系90年代也先后在各報(bào)文章述了橡膠元件的基本性能，著重分析了獨(dú)立懸架中橡膠元件對(duì)汽車穩(wěn)定性的和平順性的影響并提出了處理運(yùn)動(dòng)學(xué)問題的思路和方法[10]員的采用ms軟件對(duì)整車系統(tǒng)分析，通過系統(tǒng)仿真預(yù)測(cè)整車的性能并給予優(yōu)化改善有效的縮短了產(chǎn)品的開發(fā)周期張?jiān)絊[1][12]S/r/抬頭性能、懸架剛度和側(cè)傾角剛度得到明顯改善。仿真分析結(jié)果與理論計(jì)算結(jié)果對(duì)比表明，該方法可以準(zhǔn)確地計(jì)算懸架的多種性能參數(shù)。。在國(guó)內(nèi)的方面湖南大學(xué)劉美燕通過ADAMS軟件建立了湖南大學(xué)的真測(cè)試已建立整車模型的穩(wěn)定性然后比較其優(yōu)化前后變化[13]西北工業(yè)大學(xué)趙寧在的文章中通過ADAMS構(gòu)造出微型多功能車的懸架模型，其穩(wěn)定性有了很大的提高[14]。華南理工大學(xué)吳健瑜利用ADAMS分別對(duì)華南理工車隊(duì)前后懸架實(shí)行建模仿真和多目標(biāo)優(yōu)化而且對(duì)懸架主要零嫚對(duì)前后懸架進(jìn)行車輪上下跳動(dòng)仿真并以上下橫臂與車架鉸接點(diǎn)為設(shè)計(jì)1.1湖南大學(xué)易車車隊(duì)本文的主要研究對(duì)象是小型的懸架系統(tǒng)，在閱讀眾多文獻(xiàn)的基礎(chǔ)上，總結(jié)出一種對(duì)小型懸架系統(tǒng)科學(xué)合理的設(shè)計(jì)方法并利用ADAMS/Car模1.12想的運(yùn)動(dòng)特性，保證汽車的穩(wěn)定性，使汽車獲得高速行駛能力[17]。直接沖擊以性元件產(chǎn)生過大變形橫向穩(wěn)定器則是減少汽車轉(zhuǎn)彎行駛時(shí)懸架的分類方式有許多種，鑒于懸架一般為不等長(zhǎng)雙橫臂獨(dú)立懸架，常見的懸架形式及特產(chǎn)成本，所以絕大多數(shù)都安裝雙橫臂獨(dú)立懸架，例如，常見的F1和FSAE等。2.2優(yōu)點(diǎn)：相比于推式懸架，減振器和搖臂連接方式不變，但整置較低，重心下降，一定程度上提高了穩(wěn)定性；除此之外，由圖可見，拉桿、上下器在內(nèi)部使重心降低的同時(shí)，使得調(diào)節(jié)阻尼變得。無推拉桿不等長(zhǎng)雙橫臂懸架，如圖2.32.3小，使懸架的行程變短，對(duì)平順性和穩(wěn)定性有影響。對(duì)于汽車的懸架的設(shè)計(jì)要求如下保證汽車具有良好的穩(wěn)定性的同時(shí)，還需要保證具有足夠的強(qiáng)度和。2.42.4比賽中對(duì)的輪輞有一定的要求，F(xiàn)SAE中要求輪輞直徑不得小于都有很大影響。一般的F1車隊(duì)都由專門的合作公司或旗下專業(yè)部門去研圖2.5設(shè)計(jì)輪輞三維模型比賽對(duì)于的軸距同樣有要求，F(xiàn)SAE中要求軸距不得小于1525不利于1600mm。輪距的確定則是由計(jì)算（2-1）獲得選 式中：B為輪距，mmL為軸距，mmk為系數(shù)，對(duì)于取值范圍為0.656~2.6。參數(shù)名稱/長(zhǎng)度寬度高度軸距前輪輪距后輪輪距質(zhì)量表2.6初定部分技術(shù)參立柱的作用是連接的轉(zhuǎn)向制動(dòng)和懸架系統(tǒng)而對(duì)于后輪有驅(qū)動(dòng)裝置，2.6為本圖2.6前后懸架立柱三維模（3.2.3）圖2.7懸架減振器模導(dǎo)向機(jī)構(gòu)在運(yùn)動(dòng)過程中，應(yīng)該對(duì)的行進(jìn)軌跡有一定的導(dǎo)向作用。設(shè)計(jì)中上橫臂長(zhǎng)度為下橫臂長(zhǎng)度的0.78倍，可以使車輪跳動(dòng)時(shí)輪距的變化量2.8所示。 a前懸架上橫臂 b前懸架下橫臂圖2.8 圖2.9懸架搖臂模型圖2.10所示為懸架推桿的三維模型，推桿的作用就是傳遞下橫臂的圖2.10懸架推桿模型2.112.12所示。圖

圖 ，大體設(shè)計(jì)方案的部分技術(shù)參數(shù)以及各個(gè)零部件的設(shè)計(jì)模型為第三章設(shè)，3首先確定的主要總體參數(shù)，如整車質(zhì)量、輪距、軸距等初步選擇的前后偏頻參照按初設(shè)參數(shù)計(jì)算懸架剛度，此時(shí)為沒有安裝橫向穩(wěn)定桿時(shí)的3.13.1表3.1FSAE車輪定位參數(shù)取值范 3.23.2--3-1懸架正視幾何是指從汽車橫向垂直平面來研究懸架的幾何關(guān)系，如圖

3.3右。常見的傳動(dòng)比范圍是0.6-0.8，滿足設(shè)計(jì)要求。IC對(duì)輪距變化的影響。轉(zhuǎn)動(dòng)瞬心在地面3.4所

3.4側(cè)視圖的轉(zhuǎn)動(dòng)瞬心IC影響軸距的變化。對(duì)前懸架或后懸架，當(dāng)轉(zhuǎn)動(dòng)瞬心懸間幾圖3.5懸間幾 通過選定懸架偏頻來逐步計(jì)算懸架各種剛度，包括乘適剛度(懸架等效剛部分的內(nèi)容可知，偏頻和懸架的軟硬、汽車的操穩(wěn)性和平3.6偏頻國(guó)內(nèi)外FSAE的前后偏頻一般在2.4~4.0Hz中選取，且前高后低。此fF2.8Hz，fR整車質(zhì)量(68kg)m：303kg；簧上質(zhì)量估算值msm：235kg1.6m；前輪距tF：1.25m；后輪距tR：1.22ma：0.9m；0.28m18.6mm42.1mm

0.5bmsm/l

（3-msmlrmsmrr

（3-乘適剛度是指輪胎接地點(diǎn)相對(duì)車架或車身單位垂直位移時(shí)所受到的垂向力。

（3- 4

（3-車輪中心剛度是指車輪中心相對(duì)于車架或車身單位垂直位移時(shí)所受到的垂向力。

=150000N/m

TKT

（3-

TKT

(3-(t2)K KF rF180(KlFKrFKlFKrF

(3-(t2)K KR lRrR180(KlRKrRKlRKrR

(3-1gmgH KF

3039.80.295-1.73/g243238

(3-式中，假設(shè)以V=50km/h行駛在賽事規(guī)定的半徑為R=9m的最小彎道，則yAV2/(Rg)(50/3.6)2/(99.8）y

（3-WF

KFKFKR

bZRF)l

2.2303

0.71.8610-(3-

WR

KFKR

aZRR)l

2.2303

0.94.2110-(3-

假設(shè)前后懸架行程均為Z30mmKRFWF/Z777/0.0325909N/KRRWR/Z863/0.0328783N/ 2

(3-(3-fF

(3- 2 11

(3-fF3.6Hz,fR再次計(jì)算上述(3-7)到(-16)，可知：KRF9N/KR3N/mKF8N/m

KF427NmKR463Nm

0.93/前軸橫向載荷轉(zhuǎn)移：WF后軸橫向載荷轉(zhuǎn)移：WRZFZR由于側(cè)傾增益值0.93°/g低于低負(fù)升力的側(cè)傾增益取值范圍8°/g，因此此總的側(cè)傾角剛度為427Nm/已滿足設(shè)計(jì)要求，也就是說不 MR2313180.758217994N/ MR2356180.758220465N/ ZSF2ZF/MR20.028/0.758ZSR2ZR/MR20.0313/0.758

(3-(3-(3-(3-

msmlfgMR58

(3-sr

.09

(3-（5，8，在此選C,C,C,C,

(3-8FC,K8FC,K

(3-88381.8 8FC,K

(3-8491 式中：[8491 fddf=4mmdr=5mm。ffDf

64

(3- DC,d65 nf

Gdf8C,3

8.31044863

(3-n 8C,3

8.3104863

(3-式中G為切變模量，彈簧材料為碳鋼，G=83×103N1.5-2倍，本文最終選取工

17nr18彈簧的剛度計(jì)算和行程計(jì)算 懸架選擇合適的彈簧型號(hào)及減振器減振器阻尼系數(shù)計(jì)算如下式中，msf

（3-r相對(duì)阻尼系數(shù)s取得大一點(diǎn)。在進(jìn)行設(shè)計(jì)時(shí)，先選取r與s的平均值。沒0.25~0.35值應(yīng)該取小些。行駛路面環(huán)境較差的汽車，值應(yīng)該取較大些，一般取=0.3，sF4msmlffF43.140.351.43.6692Ns/SF4smsmlffF43.140.651.43.61385Ns/R4msmlrfR43.140.366.13.3828Ns/SR4SmsmlrfR43.140.666.13.31655Ns/數(shù)值的計(jì)算 懸架選擇合適的阻尼器型號(hào)提供依據(jù)本章主要是對(duì)懸架的重要參數(shù)進(jìn)行了進(jìn)一步的設(shè)計(jì)計(jì)算，首先介紹了F1懸架參數(shù)設(shè)計(jì)的設(shè)計(jì)流程，為后面的計(jì)算作指導(dǎo)。其次解釋懸架幾何4ADAMS/CarADAMS/CarADAMS/Car模塊是由MCSAudi,BMW,Renault、Volvo等公司聯(lián)同時(shí)輸出可以反映穩(wěn)定性乘坐舒適性制動(dòng)性以及安全性等性能的參數(shù)。interfaceADAMS/Car模塊可以幫助工程師們工作更加快速精確，然后集中精力去特性進(jìn)而指導(dǎo)設(shè)計(jì)的改造；相比于物理樣機(jī)的試驗(yàn)，ADAMS/Car的評(píng)價(jià)改進(jìn)影響等外界因素耽擱時(shí)間；相比于真實(shí)試驗(yàn)，虛擬試驗(yàn)不存在任何。ADAMS/CarADAMS/Car模塊一般的建模流程是設(shè)計(jì)人員在模板“temtebuilder"下構(gòu)建所需模板，或者對(duì)已有的模建立模板是仿真分析中的關(guān)鍵步驟，建立過程主要有以下幾步把它們定義為整合零件“generalpart"。attaent"定義參數(shù)變量“parametervariable"。對(duì)于不同的子系統(tǒng)模板，需要定ADAMS/Car模塊下的建模過程便已完成。懸架的評(píng)價(jià)指標(biāo)一般以下幾點(diǎn)在建立懸架運(yùn)動(dòng)學(xué)仿真模型時(shí)采用的坐標(biāo)系是以前懸架左右車輪中心連軸，向后為正;汽車橫向?yàn)閅軸，向右為正;汽車垂向?yàn)閆軸，向上為正。FSAE前懸架是推式不等長(zhǎng)雙橫臂獨(dú)立懸架，上下控制臂均為A型。4-1為雙橫臂獨(dú)立懸架的結(jié)構(gòu)示意圖，懸架具有左右側(cè)對(duì)稱性。AB點(diǎn)為下控制臂前、后鉸鏈，DE點(diǎn)為上控制臂前、后鉸鏈，CF點(diǎn)為下、上控制臂與轉(zhuǎn)向節(jié)鉸鏈，G為推桿與下控制臂鉸鏈，H為推桿與搖臂鉸鏈，I為搖臂與減振器鉸鏈，J為搖臂與車架鉸鏈，L為減振器上體與車架鉸鏈，M為轉(zhuǎn)向節(jié)臂與轉(zhuǎn)向橫拉桿鉸鏈，N為橫拉桿斷開點(diǎn)，0為車輪中心。1一車架；2一減振器；3一搖臂；4一上控制臂；5一下控制臂；67一轉(zhuǎn)向節(jié)總成；8一轉(zhuǎn)向橫拉桿；9由于FSAE的懸架結(jié)構(gòu)和普通轎車有些區(qū)別，所以不能直接調(diào)2、3章懸架參數(shù)設(shè)計(jì)得到的硬點(diǎn)坐標(biāo)和相關(guān)參數(shù)，創(chuàng)建前懸架的運(yùn)動(dòng)學(xué)仿真4.2所示。3章此的側(cè)傾增益為0.93g/°，故此時(shí)仿真的情況為受到約為2g橫 過多轉(zhuǎn)向特性故對(duì)于穩(wěn)定性要求較高的車輛而言尤其是車速較高的轎車和，一般采用負(fù)的外傾角。車輪外傾角變化對(duì)轉(zhuǎn)向、穩(wěn)定性的影響1°以內(nèi)。4.5由圖可以看出，此靜平衡位置時(shí)車輪外傾角即為設(shè)計(jì)值-1°，車身側(cè)變化了1.58°，對(duì)而言，外傾角變化范圍較大，可以進(jìn)行優(yōu)化。汽車完成轉(zhuǎn)向后，迫使汽車轉(zhuǎn)向的外力，前輪軸軸荷的作用下，主銷內(nèi)傾角變化對(duì)轉(zhuǎn)向穩(wěn)定性的影響4.6靜平衡位置時(shí)主銷內(nèi)傾角為設(shè)計(jì)值7.519.13mm7.58.35°;18.70mm時(shí)，6.77對(duì)而言，內(nèi)傾角變化范圍稍大，可以進(jìn)行優(yōu)化。主銷后傾角的存在可使轉(zhuǎn)向軸線與路面的交會(huì)點(diǎn)位于輪胎接地點(diǎn)的前方，力以后，側(cè)向反作用力就可以幫助車輪自動(dòng)回正決于主銷后傾角軸線的延長(zhǎng)線與輪胎和地面實(shí)際接觸點(diǎn)的距離以及行車的速在選用主銷后傾角時(shí)，要依據(jù)車輛的具體行駛狀況而設(shè)定，過大會(huì)使轉(zhuǎn)向時(shí)外側(cè)車輪的外傾角向負(fù)方向變化。如果是無助力轉(zhuǎn)向情況，一般選取不300°—33°—10移，產(chǎn)生一種力矩，所以后傾角可減少，甚至為負(fù)值，即主銷前傾。一般希望在懸架壓縮時(shí)主銷后傾角增大，拉伸時(shí)減小，用以造成制動(dòng)時(shí)因主銷后傾角變大而在控制臂支架上產(chǎn)生防止制動(dòng)前俯的力矩。主銷后傾角對(duì)轉(zhuǎn)向、穩(wěn)定性的影響32.98742.9829，變化十分小，符合設(shè)計(jì)要求。車輪前束角對(duì)轉(zhuǎn)向、穩(wěn)定性的影響4.8所示。靜平衡位置時(shí)前1前束角從-1°往正值方向變化到-0.92°;車輪下跳18.70mm時(shí)，前束角從-1°，對(duì)于，側(cè)傾中心在地面之上時(shí)，轉(zhuǎn)彎時(shí)懸架壓縮引起外側(cè)車輪的正輪胎傾角增益，使其接地性降低。如果側(cè)傾中心位于地面之下。則轉(zhuǎn)彎時(shí)，輪胎側(cè)向力對(duì)側(cè)傾中心的力矩使懸架相對(duì)于底盤上升。所以設(shè)計(jì)時(shí)，要，4.9靜態(tài)時(shí)側(cè)傾中心高度為設(shè)計(jì)值42.55mm，車身側(cè)傾過程中，車輪上跳19.13mm42.886mm42.9mm;時(shí)，側(cè)傾中心高度從42.55增加到42.895mm。側(cè)傾中心高度總變化量為0.009mm變化一方面影響汽車的直行穩(wěn)定性以及汽車的穩(wěn)定性;另一方面，由于輪胎的橫向滑移，導(dǎo)致輪胎的磨損，降低了輪胎的特性及使用。為獲得良好近，能有效控制輪距變化。轎車的輪距變化應(yīng)在-5/50mm—5/50mm之內(nèi)。4.101260.45mm1259.70mm—1260.45mm，變化量0.75mm，說明前輪側(cè)滑量較小，不需要進(jìn)行優(yōu)化。ADAMS/Car模塊建模仿真，并分析參數(shù)變化。首ADAMS/Car指標(biāo)，為之后的仿真分析奠定基礎(chǔ)。在本章中創(chuàng)建了前懸架的模型，并結(jié)本文主要對(duì)小型懸架進(jìn)行初步設(shè)計(jì)及仿真分析。選擇懸架的結(jié)構(gòu)形式ADAMS/Car由于時(shí)間條件的限制本文中只是介紹了懸架的設(shè)計(jì)及仿真過程，對(duì)于懸架完整過程還有欠缺。下一步應(yīng)進(jìn)一步完成以下過程：ADAMS/Insight模塊優(yōu)化，利用多目標(biāo)優(yōu)化分析方法對(duì)懸架進(jìn)行優(yōu)化設(shè)計(jì)，進(jìn)而使懸架獲得致，默化，使我不僅接受了全新的思想觀念，樹立了明確的學(xué)術(shù)目標(biāo)了基本，[2][德]H-P威魯麥特.車輛動(dòng)力學(xué)：模擬及其方法（第1版）.理工大學(xué)[4]M.米奇克.汽車動(dòng)力學(xué)第二版[M].：人民交通，1997BadihA.Jawad,JasonBaumann.DesignofFormulaSAESuspension[J].MotorsportsEngineeringConferenceandExhibition,SAEInternational,CristinaElenaPopa.SteeringSystemandSuspensionDesignfor2005FormulaSAE-ARacerCar[D].BachelorPaperofUniversityofSouthernQueensland,2005Polega,B.D,JawadB.ADesignofFSAESuspensionWashingtonDC,SAE[8]AMihailidis,ZSamaras,INerantzis,GFontaras,andGKaraoglanidis.TheDesignofaFormulaStudentRaceCar[J].IMechEVol.223PartD:J.AutoEngineering[9].汽車動(dòng)力學(xué)[M].吉林：吉林科學(xué)技術(shù)[10]]陳新，林逸，王煥明等.彈性元件對(duì)懸架性能的影響[J].汽車技術(shù)，1996(5):11-[11]今.汽車多體動(dòng)力學(xué)及計(jì)算機(jī)仿真[M].吉林：吉林科學(xué)技術(shù)[12]ADAMS_CAR[J].學(xué)報(bào)(工學(xué)版)，2004,34(4):554-[13].FSAE懸架仿真分析及穩(wěn)定性虛擬試驗(yàn)[D].長(zhǎng)沙：湖南[14]?？毠x.微型多功能車雙橫臂獨(dú)立懸架優(yōu)化設(shè)計(jì)[J].計(jì)算[15].大學(xué)生方程式懸架設(shè)計(jì)及優(yōu)化研究[D].廣州：華南理工大李嫚.FSAE懸架的優(yōu)化設(shè)計(jì)及分析[D].哈爾濱：哈爾濱工業(yè)大學(xué)車王望予.汽車設(shè)計(jì)[M].：機(jī)械工業(yè)陳家瑞.汽車構(gòu)造(下冊(cè))[M].：人民交通，1995[19]MSC.ADAMSUserManual,2007與制造，2004(2):115116——RaceCarVehicleDynamics(17.5-17.5FrontManytypesoffrontsuspensionshavebeenusedovertheyears.Theyincludevariousbeamtypeaxleswithsteeringviakingpinsateachendoftheaxle,theparalleltrailingarmtypesuchastheVW,theMorganslidingpillartype,andtheChevroletDubonnet.Inrecenthistory,passengercardesignshavecomedowntobasicallytwotypes:theMacPhersonStrutandtheSLA(Short-Long-Arm).Thischapterwilldealonlywiththelasttwomentionedasthesemakeupthemajorityoffrontsuspensionsthatwillbeencountered.Theothertypessufferfromeitherhighbendingloads,poorgeometry,highfriction,oracombinationoftheseproblems.Thebestwaytodiscusseachtypeistogothroughthedesignprocessstepbystep.Foreachstepadecisionhastobemadethatisoftenacompromise.Bydiscussingthesedecisions,hopefullyafeelingforthelimitationsofthedesignwilldevelop.FrontSuspensionDesignIssues-Thefirsttaskindesigningafrontsuspensionofanytypeistoestablishthepackagingparametersthatarefixed,orabsoluycannotbechangedforwhateverreason(seeFigure17.17).Theseshouldbelistedsothattheyarenotoverlooked.Thenexttaskistopackagethewheel,tire,brakes,andbearings.Thisisdoneincarposition,sothetrackwidthhastobeknown.Ifitisnotyetestablished,itshouldbemadeaswideaspractical.Thissoundsevasive,buttherearetrade-offsineverything,eventhingsassimpleaschoosingthetrackwidth.Forexample,whatdotherulesallow?Whatisthepredominantracetracktypeonwhichthecarwillrun?Istopspeed,thuslowfrontalareaimportant?Areslow-speedtightstreetcircuitsofconcern?Alltheseissuescanaffectthedecisiononthebasictrackwidth!Tiresizeandrimdiameterandwidthmustbesettled.Thespecificwheelmanufacturerneedstobeknownandacrosssectionofthewheelisdesirableforoptimizingtheuseofthatwheel.Tiresizesareusuallylimitedbythesanctioningbodyrules.Ingeneral,useallthetiretheywillletyougetawaywith.Anotherpointistoalwaysdesignforthelatestsizesbeingdevelopedbythers;thisguaranteesthatthelatestcompoundsandconstructionswillfityourcar.Remember,thetireisthesinglemostimportantchassiscomponentonthecar.Thewheeloffsetisworkedoutinconjunctionwithfittingthebrakecalipertocleartheinsidesurfaceofthewheel.Oncethecaliperislocated,thisautomaticallylocatesthebrakerotor.Withtherotorlocationcomestheabsolutefarthestoutboardlocationforthelowerballjoint.Wheelbearingsneedtobelookedatsoon,asideallytheyshouldbelocatedsuchthatthetirecenterisbetweenthetworowsofballsorrollers(tominimizeloadsonthebearings).Nowthatthelowerballjointcrossearboundary(lalposition)hasbeenset,theheightofthelowerballjointcomesnext.Inproductionearsitmustbeabovea5-in.washrackclearancerequirement,butonracecarsitshouldbemadeaslowaspossibleforstructuralreasons.Usuallythereisnorulebutsomepracticalconsiderationssuchasdeflatedtiregroundclearancemightbeinorder.Ifitistotallyinsidethewheelallithastodoisclearthewheelandthebrakerotorunderalltravelandloadconditions.Thedecisionaboutthekingpinangleinthefrontviewisthenextorderofbusiness,Theissueshere escrubradius,spindlelength,andkingpinangle,Theyareinterrelatedlinkageratiosforthespring,shock,andstabilizerbarascloseto1:1aspossiblewillprovidemoredirectloadpathsthusimprovingsystemstiffnesswhileprovidingalighteroveralldesign.FrontSuspensionDesignIssues——TheShort-LongArm(SLA)suspensionisthechoiceofdesignerswithoutquestionforitsabilitytomeetdesiredperformanceobjectiveswithminimumcompromise.Thedesignstartswiththebasicpackageasdescribedabove.Thedetailsofthetrackwidth,thewheelsize,thetire,thebrakes,etc.,bringaboutthelocationavailableforthelowerballjoint.Theupperballjointislocatedeitherviakingpinanglerequirementsorbyscrubradiusrequirements.ThereisalittlemoredomwiththeSLAthatisnotavailabletothestrutdesignandthatisthechoiceofashockknuckleoratallknuckle.Theshortknucklemeanstheupperballjointislocatedbasicallywithinthediameterofthewheel.Withhighoffsetandlarge-diameterwheelsthekingpinanglecanbekeptsmall(whileachievingsmallspindlelengthsandscrubradius)bytuckingtheupperballjointintothewheel.Toreducetheloadsonthecontrolarmsandothersuspensioncomponents,itisdesirabletohavealongkingpinlength,thatis,separatetheupperandlowerballjointsasmuchaspossible.Dependingondetailsoftheinstallation,theshortknucklemayyieldlessthanoptimumkingpinlength.Theotheralternativeisthetallknuckledesigntheballjointsnaturallyhaveaverylargespanandthusreducereactionloads.Thisoptionalsoallowsreasonablekingpinangleswhileachievingdesiredspindlelengthandscrubradius.Anotheradvantageforthetallknuckleisthatbuilderrorswillresultinsmallergeometryerrorsthanwithshortknuckledesigns.Somenegativestothetallknuckle,ofcourse,aretheaddedstructuralrequirementsoftheknuckle,andthelimitationofneverchangingtiresizeorwidthwithoutwideningthetrackandincreasingspindlelengthandscrubradiusafterthedesignisWiththeupperandlowerballjointlocationsestablished,thetierodouterpointshouldalsobesetpertherequirementsestablishedinChapter19onsteeringgeometry.FrontViewThefrontviewgeometrycannowstart.Thefrontviewswingarminstantcenterisuniquelydeterminedbythedesiredrollcenterheightandrollcamber(seeFigure17.18).Thedesiredrollcambersetsthefrontviewswingarmlength(locationoflineA-A)asfollows:fvsa=(t/2)/(1-rollcamber) t=trackwidthRollcamber=wheelcamberangle/chassisrollangle(withbothmeasuredrelativetotheStepA-Establishfrontviewswingarmlength(lineA-StepB-EstablishrollcenterlocationandprojectfromgroundcontactpointthroughRC

A-A,establishingStepC-ProjectlinesfromouterballjointstoStepD-ChoosecontrolarmlengthstogetinnerpivotLocationsStepE-ConnecttierodouterpivottoICStepF-EstablishtierodThefrontviewinstantcenterheightissetbyprojectingalinefromthetirecentercontactpatchthroughthedesiredrollcenterheight.Theinstantcentermustlieonthisline.Nowwecanprojectlinesfrombothballjointstotheinstantcenter.These ethecenterlinesoftheupperandlowercontrolarmnesasprojectedintotheverticalnethroughthewheelcenter.Packagingrequirementswillestablishthelengthofthelowercontrolaimbutitshouldbemadeaslongaspossible.Thelengthoftheuppercontrolarminrelationtothelowerarmadjuststheshapeofthecambercurve.Iftheyarethesamelengththecamberversuswheeltravelcurvewillbeastraightline.Iftheupperislongerthanthelower,thecurvewillbeconvexwithitscurvaturetowardpositivecamber.Iftheupperisshorterthanthelower,thecurvewillbeconcavetowardnegativecamber.Astheupperismadeprogressivelyshorter,thecurvatureincreases.Theidealcurvehasprogressivenegativecamberinbumpwithmuchlesscamberchangeindroop.SomedesignerstrytogetthecambertogopositiveindroopandprogressivelynegativeinTofinishthefrontviewgeometry,thetierodandracklocationshouldberoughedin.Thisisdonebyprojectingalinethroughthetierodouterpoint(establishedinChapter19onsteering)andthefrontviewinstantcenter.Thecorrecttierodlengthisthenestablishedforalinearridetoecurve,Thislengthwillbemodifiedafterthesideviewgeometryiscompleted,butngitnowisagoodideatohelpnarealisticracklocation.SideViewThesideviewgeometrycomesnextinthisdesignprocess,Rememberthatwhenwearedealingwiththe"sideviewgeometry"wearelookingatthesideofthecarbutthepointofinterestthatwearecreating,i.e.,the"instantcenter"isintheneofthewheel.Thedesiredinstantcenterisestablishedfirst.Thisisaresultofcalculatingthedesiredantifeatures,theminimumsideviewswingarmlengththatisacceptable,andwhetherthewheelpathmustberecedinginbumpornot.Figure17.19isagraphicillustrationofhowthisisdone.Sometimesthedesiredparameterswill .Forexample,withfront-wheeldrive,anti-liftandarecedingwheelinbumpare patible.Anothercommoncompromiseoccurswhenahighvalueofanti-diveisdesiredalongwithalargeamountofwheelrecessioninbump.Thisusuallyyieldsasideviewswingarmlengththatistooshorttobepractical.Sothefactorsthatarecontrolledbythesideviewinstantcenterlocationhavetobecarefullyassessedbeforethefinalpointischosen.Oncetheinstantcentersareestablished,howdoesthedesignerguaranteethatthegeometrywillactuallyprovidethecorrectfrontviewandsideviewinstantcenters?Thisisthenextsubjectinthedesignprocess.SLAControlArmInnerPivotAxisTworulesofdescriptivegeometryareusedtocoordinatethefrontviewandsideview.Theyare1)threepointsdetermineane,and2)theintersectionoftwonesformsastraightline.FortheSLAandothersuspensionsthelayoutprocedureswillbegiven.ProjectiontechniquesofdescriptivegeometryareusedtodeterminetheA-framenessuchthattheirintersectionformsthedesiredinstantaxis.Nofurthertheoryofdescriptivegeometryisgivenhere.Thefrontviewupperandlowercontrolarmsthathavebeendevelopedsofararereallyonlyalineinthetransverseneofthewheelatthisstageofthe-design.Wehavenotdeterminedtheactualpositionsforthefrontandrearinnerpivotsofthesearms.Wedoknowthatwhateverwedointhesideview,wedonotwanttolosewhatwedevelopedinthefrontview.Thenextstepthenistoextendthe-controlarmlinesinthefrontviewoutboarduntiltheyintersectthelongitudinalneofthewheel.Lookingnowinthesideview,straightlinesaredrawnfromthesenewcontrolarmextensionpointstothepredeterminedsideviewinstantcenter,Intomaintainaccuracy.Infrontview,theuppercontrolarminnerpivotispoint#l,theupperballjointispoint#2,andtheextensionintothelongitudinalneispoint#3.Forthelowercontrolarmthecorrespondingpointsare#11,#12,and#13.Thesesixpointsaretransferredtothesideview.Twolinesinthesideviewfromthesideviewinstantcentershouldbeextendedthroughandbeyondpoints#3and#13.NextwechooseanarbitrarypointinthesideviewonthelinebetweentheICandpoint#3thatisafewinchesaheadofpoint#3andnumberitpoint料，Repeatthisprocedureforthelowerarmcreatingpoint#14.Nextweprojectthesepointsintothefrontviewsothatboththesideviewandthefrontviewcontainpoints#1through#4and#llthrough#14.Tomaintainthedesiredgeometryallupperarmpoints(#1through#4)mustbeinasinglene,andalllowerarmpoints(#11through#14)mustbeinasinglene.Aslongaswealwaysprojectstraightlinesthroughtwopointsinaneandestablishnewpointsontheselines,thenewpointswillremaininthene.Nextweprojectalinefrompoint料throughpointThisisdoneinbothviewsandthelineisextendedinthefrontviewatleastasfarinboardaspoint#1.Repeatforthelowerarmusingpoint#14through#12inboardatleastpoint#11.Foralmostallsuspensiondesignsitisacceptableandevendesirabletohavetheinnerpivotsofthecontrolarmsparalleltothecenterlineofthecar.Thereforethenextstepwillbetodrawaverticallinethroughpoint#1inthefrontview;thislineisthefrontprojectionoftheuppercontrolarm{uca)axis.Identifypoint#5onthisverticallineastheextensionofalinefrompoints#4throughpoint#2.Repeatforthelowercontrolarm(lca)viaaverticallinethroughpoint#11,findingpoint#15from#14through#12.Nextprojectpoints#5and#15intothebetween#15and#11(showndashedinthesideview).Thecontrolarminnerpivotsmustlieontheselines.Theycanbespreadwiderornarrowerthanthepointsbuttheymustfallonthelines.ReferringbacktoFigure17.6wecannowredrawitasFigure17.21toshowthattheucaandlcadefinetwonesthatintersectandformtheinstantaxisforthesuspension.Itislefttothereadertoextendtheconstructiontoincludethedesiredcaster(sideview)angleofthesteering(kingpin)axis.Thedesignisnowcompleteexceptforfine-tuningthetierodtoobtainalinearride-toeplot(ridesteer).FrontSuspensionDesign——MacPhersonAMacPhersonstrutsuspensioncanbethoughtofasaspecialcaseofanSLA,Insteadofanuppercontrolarmthereisastrut,and,asdescribedinthefirstsectiononkinematics,thestrutisaslideroraninfiniylonguppercontrolarm.Thislongupperarmyieldsacambercurvethatlosesratherthangainsnegativecamberinbump,Thisisoneofthemajorcompromisesofthestrut-typesuspension,especiallyforperformanceapplications.TocontinuewiththedesignprocesswestartaswedidwiththeSLAinestablishingthewheelandtiresizesandlocations,thebrakecaliperandrotor,andfinallythelowerballjointcrosscarlimitandheightlimits(refertoFigure17.22).Theupperstruttobodymountingpointisthenextitemestablished.Itisthepointaboutwhichthestrutcanrotateinalldirections,butisfixedfromtranslatinginanydirection.Onpassengercarsthisisnormallyarubberisolatormount.Onraceearsitisusuallyamonoball(spherical)typemounting.Theupperstrutmountingpointliesonthekingpinaxisbydefinition.Wechooseakingpinanglepertheearlierdiscussion,Itsposition,heightwise,isafunctionoftheparticularstrutthatisbeingused,whetherthespringismountedonthestrutornot,andhowmuchwheeltravelistobeallowed.Animportantpointtomakeisthattheaxisofthestrutisnotnecessarilycowiththekingpinaxis!Thekingpinisthesteeringaxiswhilethestrutstrokingaxisdictatesothersuspensionparameterstobediscussednext.Alowercontrolarmlineisestablishedbycingtheballjointasonepointinthefrontviewandaimingtheotherpointatthedesiredinstantcenter.Thelengthofthearmisestablishedbyotherpackagingconstraints,butingeneralitisbestifitislong.Nextthestrutorientationinthefrontviewisadjustedsothatitscenterlineis90°toalinefromtheinstantcentertotheupperstrutbodymountingpoint.Dependingonthehardwareusedandthepackagingconstraintsthismaybeveryeasy,butoftenthereisan patibilityofcomponentlocationsanddesiredgeometry.Youwillfindthatonlycertainrealisticcombinationsofrollcenterheightsandswingarmslengthswillfit.Thismeansthatoftenastrut-typesuspensionhascompromisedgeometrybecauseitisastrut!ThesteeringtierodouterpointischosenforreasonsaffectingAckermannandothersteeringgeometryissues.Oncethisisestablishedtheinnerpointheightislocatedsuchthatalinefromtheouterpointthroughtheinnerpointpassesthroughthefrontviewinstartcenter.Thelengthofthetierodisthenchosentogivealinearride-toecurve.(SeeChapter19onsteering)Withthefrontviewcompletedwemovetothesideview.Againthefirstthingthatmustbeestablishedistheparametersthatareaffectedbythesideviewinstantcenterlocation.Fromthefirstpartofthischapterweknowthesearetheanti-dive,anti-lift,casterchange,andwheelpath.Theestablishmentoftheseparametersuniquelydefinesthelengthandheightoftheinstantcenter:UsingthesameprocedureasdescribedfortheSLA,thelowercontrolarmneisprojectedintothelongitudinalwheelnegivingalineinthesideviewthatextendsthroughthedesiredinstantcenter.Nextalinefromtheinstantcentertothestrutbodymountingpointisdrawn.Thestrutisnowadjustedsothatane900tothestrutaxisintersectsthewheelne,formingalinethroughtheinstantcenter.SeeFigure17.22forafurtherexnationofthisOnefeaturethatmakesstrutshardtodesignisthatyoualwayshavetoworkwithane90°tothestrutslideraxisinbothviews.Becauseofthis,whenyoutilttheaxisinoneviewitchangesthetiltintheotherview.Sowhenyouhavedonethefrontviewandthengonetothesideviewyoumustgobacktothefrontviewagainbecauseitisnolongercorrect.Thesestepsarerepeatedafewtimesbeforethefinalsolutionisconfirmed.Evenwithacomputerprogramtohelp,youstillneedtocheckbothviewsandrecheckthemafteranyminoradjustmenttothestrutaxis.Whentheinstantaxisisfinallyestablishedthebumpsteercanbefinalized.Thetierodpointchosenearlierwhilefirstworkinginthefrontviewwastoestablishinitialpotentiallocationsfortherackwithrespecttotheoverallpackage.Thebumpsteerisbestdonebyacomputerprogram.ThetheoryofhowtogetproperbumpsteeriscoveredinChapter19.Afewotherpointsthatshouldbecheckedduringthedesignprocessarestruttraveltowheeltravelratio,springtowheeltravelratio,andspringcenterlineaxislocationtominimizestrutbendingloads.Ifthespringactsonthelowercontrolarm,thestrutbendingmomentwillbeequaltotheverticalloadonthewheeltimesthehorizontaldistancefromthelowerballjointtothewheelcenter.Whenthespringismountedonthestrut,thecenterlineofthespringisprojecteddownwardtointersectwiththelowercontrolarmaxis.Ifthisintersectionoccursinlinewiththewheelcentertherewillbenobendingloadsinthestrut(seeFigure17.23).Thisshouldbecheckedinboththefrontviewandthesideview.Astheintersectiondeviatesfromidealthebendingloadsgrow.BendingloadscreatefrictionandfrictionisanabsoluteenemyofsuspensionfunctionRef.169discussestheproblemofstrutbendingloads(andresultantfriction)andtheproblem-ofpackagingthespringatthecorrectangle(Figure17.23)whenwidetiresareused.Thereferencediscussesanovelspringusedinanumberofnewproductioncarsinitslengthstate,theaxisofthis"sideloadspring"isbent(orcurved)inthefrontview.Whenthisspringiscompressed,thespring isoffsetfromthespringaxis;thisisequivalenttotiltingthespringbutreducesthespring/tireclearanceproblem.Springsofthissortintroducesomenewproblemsforthesuspensiontuner.First,theymustbeinstalledcorrectly(intopviewrotation)ortheoffsetwillbeinthewrongdirection-specialspringperchesmustbeused.Second;ifspringsarechangedonacaroriginallyfittedwithsideloadsprings,therecementspringsshouldbeofthesametypetoavoidexcessivestrutfriction.Alternatively,smallercoildiametercanbeandthespringperchmove