機(jī)電一體化設(shè)計(jì)外文翻譯--特種車輛制動系統(tǒng)改進(jìn)設(shè)計(jì)

1、<p><b>　　畢業(yè)論文（設(shè)計(jì)）</b></p><p><b>　　外文翻譯</b></p><p>　　題 目： 特種車輛制動系統(tǒng)改進(jìn)設(shè)計(jì) </p><p>　　控制系統(tǒng)穩(wěn)定性是針對提高駕駛安全性提出的一系列措施中最新的一個(gè)。這個(gè)系統(tǒng)能夠在40毫秒內(nèi)實(shí)現(xiàn)從制動開始到

2、制動恢復(fù)的過程，這個(gè)時(shí)間是人的反應(yīng)時(shí)間得七倍。他們通過調(diào)整汽車扭矩或者通過應(yīng)用汽車左側(cè)或右側(cè)制動，如果需要甚至兩者兼用，來實(shí)現(xiàn)準(zhǔn)確的行車路線。這個(gè)系統(tǒng)已被應(yīng)用于奔馳S600汽車了。</p><p>　　穩(wěn)定的機(jī)械自動系統(tǒng)能夠在制動時(shí)發(fā)現(xiàn)肇端，并且在駕駛?cè)藛T發(fā)現(xiàn)能夠反應(yīng)以前實(shí)現(xiàn)車輛的減速。</p><p>　　安全玻璃，安全帶，撞擊緩沖區(qū)，安全氣囊，ABS系統(tǒng)，牽引力控制系統(tǒng)還有現(xiàn)在的穩(wěn)定調(diào)

3、節(jié)系統(tǒng)。汽車安全系統(tǒng)的連續(xù)升級，已經(jīng)產(chǎn)生了一種為保護(hù)汽車所有者安全的設(shè)計(jì)模式。穩(wěn)定調(diào)節(jié)系統(tǒng)幫助駕駛員從不可控制的曲線制動中解脫出來，從而避免了汽車的擺動滑行和交通事故。</p><p>　　利用計(jì)算機(jī)和一系列傳感器，穩(wěn)定調(diào)節(jié)系統(tǒng)能夠檢測到制動輪的打滑并且比人更快的恢復(fù)對汽車的方向控制。系統(tǒng)每百萬分之一秒作出一次快速捕捉，以及斷斷汽車是否在按照駕駛員的路線行駛。如果檢測到汽車行駛路線和駕駛員駕駛路線存在一個(gè)微小的偏

4、差 ，系統(tǒng)會在瞬間糾正發(fā)動機(jī)扭矩或者應(yīng)用汽車左右制動。過程的標(biāo)準(zhǔn)反應(yīng)時(shí)間是40毫秒----人的平均反應(yīng)時(shí)間的七分之一。</p><p>　　羅伯特博世工程系統(tǒng)負(fù)責(zé)人安東·范·桑特解釋說：“一個(gè)穩(wěn)定的控制系統(tǒng)能夠‘感覺到”駕駛員想要運(yùn)動的方向，通過控制轉(zhuǎn)向角度，油門踏板的位置，制動板的狀態(tài)來確定汽車實(shí)際運(yùn)動路線的偏航比率（汽車偏離方向軸的角度）和橫向加速度”。項(xiàng)目負(fù)責(zé)人阿明·馬勒領(lǐng)導(dǎo)著

5、范桑特的工作小組和奔馳汽車公司的工程師發(fā)明了第一個(gè)完全有效的穩(wěn)定調(diào)節(jié)系統(tǒng)，該系統(tǒng)由發(fā)動機(jī)扭矩控制系統(tǒng)，制動系統(tǒng)，牽引控制系統(tǒng)組成以實(shí)現(xiàn)理想與現(xiàn)實(shí)運(yùn)動之間的最小差距。</p><p>　　汽車安全專家相信穩(wěn)定調(diào)節(jié)系統(tǒng)能夠減少交通事故的發(fā)生，至少是在傷亡嚴(yán)重的事故方面。安全統(tǒng)計(jì)表明，多數(shù)的單車撞擊事故傷亡（占傷亡事故發(fā)生的4%），事故能夠通過應(yīng)用這項(xiàng)新技術(shù)避免。這項(xiàng)新系統(tǒng)的額外費(fèi)用主要用于一系列目前汽車日益普遍應(yīng)用的

6、制動/牽引控制鎖組件。</p><p>　　穩(wěn)定調(diào)節(jié)系統(tǒng)技術(shù)首次應(yīng)用于歐洲的奔馳S600汽車，是由德國斯圖加特市的羅伯特博世公司和奔馳公司在過去幾年共同研制的。該系統(tǒng)在博世公司被稱為汽車動力控制（VDC），而默西迪稱它為穩(wěn)定電控系統(tǒng)（ESP），作用就是在任何狀況下維持車輛的穩(wěn)定性。博世公司開發(fā)了這項(xiàng)系統(tǒng)，奔馳公司把它應(yīng)用于車輛。工程師默西迪絲在柏林應(yīng)用戴姆勒奔馳汽車虛擬駕駛模擬器在極限情況下對系統(tǒng)進(jìn)行評估，例如極

7、強(qiáng)的側(cè)風(fēng)。然后他們在瑞典的安杰普勞附近的后娜瓦安湖的冰面上進(jìn)行性能測試。工作通常是在公路上進(jìn)行以適用于公共汽車和大卡車，例如避免的折合問題。</p><p>　　穩(wěn)定調(diào)節(jié)系統(tǒng)將在1995年中應(yīng)用于歐洲S系列產(chǎn)品上，隨后會在1996年進(jìn)入美國市場（1995年11月產(chǎn)品）。用戶可以選擇750美元的系統(tǒng)，就像應(yīng)用于默西迪絲的試驗(yàn)用的V8發(fā)動機(jī)上的，也可以選擇價(jià)格為2400美元的應(yīng)用于六缸發(fā)動機(jī)汽車的系統(tǒng)。后者的系統(tǒng)中差

8、不多有1650美元是用于牽引控制系統(tǒng)，該系統(tǒng)是穩(wěn)定性系統(tǒng)的先決條件。</p><p>　　并不是只有博世公司一家在開發(fā)這樣的安全系統(tǒng)，美國密歇根州的ITT（美國國際電信公司）汽車公司的奧伯恩·希爾，在1995年1月底特律北美國際汽車展覽會上展示了了?悇管理系統(tǒng)（ASMS），“車輛控制器應(yīng)該像空對地導(dǎo)彈的控制器那樣，比較而言，事實(shí)上那已經(jīng)實(shí)現(xiàn)了，不同的是兩者的費(fèi)用不同”，美國國際電信公司駐歐洲空對地導(dǎo)彈控

9、制工程負(fù)責(zé)人約翰尼斯·格雷得說。北美ITT公司“汽車制動和底盤工程”主管湯姆·麥茲指出，在未來十年美國國際電信公司的系統(tǒng)要首先出現(xiàn)在車輛上。很多工程師正在六輛特殊制造的精密車輛模型上調(diào)試這種系統(tǒng)。</p><p>　　一個(gè)比較簡單和較低效率的博世的穩(wěn)定調(diào)節(jié)系統(tǒng)也在1995年出現(xiàn)在慕尼黑寶馬公司的AG系列750iL和850Ci V-12兩款車上。寶馬公司的穩(wěn)定調(diào)節(jié)系統(tǒng)（DSC）運(yùn)用的車輪速度傳感

10、器同牽引控制系統(tǒng)和標(biāo)準(zhǔn)ABS防抱死系統(tǒng)一樣能夠識別外部情況，使車輛更容易實(shí)現(xiàn)曲線行駛和轉(zhuǎn)彎。為了檢測出車輛轉(zhuǎn)彎時(shí)潛在的危險(xiǎn)，DSC系統(tǒng)檢測的是兩前輪在轉(zhuǎn)彎時(shí)的速度差，DSC系統(tǒng)添加了一個(gè)更高級的角度傳感器利用現(xiàn)有的一個(gè)車輛速度，并且引入了它自身帶有的關(guān)于完全抱死系統(tǒng)，牽引控制系統(tǒng)，穩(wěn)定調(diào)節(jié)系統(tǒng)軟件控制原理。</p><p>　　新的博世和ITT自動穩(wěn)定調(diào)節(jié)系統(tǒng)得益于航空工業(yè)高級技術(shù)的發(fā)展，就像超音速發(fā)動機(jī)，汽車的

11、穩(wěn)定調(diào)節(jié)單元運(yùn)用一個(gè)基于計(jì)算機(jī)系統(tǒng)的傳感器來調(diào)和人與系統(tǒng)之間的，還有輪胎與地面之間差異。另外，系統(tǒng)采用了用于導(dǎo)彈制導(dǎo)系統(tǒng)的回旋傳感器。</p><p>　　優(yōu)于ABS防抱死系統(tǒng)和牽引控制系統(tǒng)之處</p><p>　　根據(jù)范·桑特和博世公司的瑞娜·伊哈德，杰瑞·帕夫在《汽車工程師》雜志所提到的，穩(wěn)定調(diào)節(jié)系統(tǒng)是ABS防抱死系統(tǒng)和牽引控制系統(tǒng)的合理擴(kuò)展。但是ABS系

12、統(tǒng)的作用發(fā)生在制動時(shí)車輪轉(zhuǎn)向?qū)⒈绘i死時(shí)，牽引控制是預(yù)防加速時(shí)的車輪滑動，穩(wěn)定系統(tǒng)是當(dāng)汽車自由轉(zhuǎn)向時(shí)能獨(dú)立于駕駛員作出操作。依靠不同的駕駛狀況系統(tǒng)可以使每個(gè)車輪制動或者迅速使四個(gè)輪轉(zhuǎn)速適合于發(fā)動機(jī)的扭矩，從而使車輛穩(wěn)定和減少由于制動失控帶來的危險(xiǎn)。新系統(tǒng)不僅僅控制完全制動還可以作用與部分制動，行車路線，加速度，車輪與發(fā)動機(jī)動作的滯后等，這些是ABS防抱死系統(tǒng)和牽引控制系統(tǒng)所遠(yuǎn)遠(yuǎn)不能達(dá)到的。</p><p>　　三種

13、主動的安全系統(tǒng)的作用時(shí)刻是一致的，那就是一個(gè)車輪被鎖死或者車輪漸漸失去方向穩(wěn)定性或者車輪使得行駛更加困難。如果一輛車必須在較低摩擦系數(shù)的路面制動，必須避免車輪抱死以保持行駛穩(wěn)定性和可駕駛性。</p><p>　　ABS防抱死系統(tǒng)和牽引控制系統(tǒng)能夠預(yù)防側(cè)滑，而穩(wěn)定性系統(tǒng)采取減少側(cè)面受力的穩(wěn)定措施。如果行駛車輛的側(cè)力不再適當(dāng)?shù)姆峙湓谝粋€(gè)或者更多輪上，車輛就會失穩(wěn)，尤其是車輛沿曲線行駛時(shí)。駕駛員感覺到的“搖擺”起初是轉(zhuǎn)

14、彎或者與車的軸線形成一個(gè)紡錘形時(shí)。一個(gè)獨(dú)立的傳感器必須能夠識別這個(gè)“紡錘”，而 ABS防抱死系統(tǒng)和牽引控制系統(tǒng)通過車輪的轉(zhuǎn)速不能檢測車輛的橫向運(yùn)動。</p><p><b>　　轉(zhuǎn)向操作</b></p><p>　　新系統(tǒng)通過對微小的汽車不足轉(zhuǎn)向（當(dāng)車輛對于方向盤操作反應(yīng)遲緩）和方向盤的“過敏”反應(yīng)（后輪發(fā)生來回?cái)[動）。當(dāng)車輛在轉(zhuǎn)向時(shí)如果發(fā)生不足轉(zhuǎn)向和過度轉(zhuǎn)向運(yùn)動時(shí)，

15、穩(wěn)定調(diào)節(jié)系統(tǒng)能夠通過后輪進(jìn)行內(nèi)部制動（針對曲線）糾正錯(cuò)誤。這種情況是駕駛員不能感覺類似于ABS防抱死系統(tǒng)接近于抱死極限，而使車輛不失去控制。穩(wěn)定調(diào)節(jié)系統(tǒng)能夠通過發(fā)動機(jī)降速或者單輪制動來減小推動力。</p><p>　　博世公司的研究員解釋說：“側(cè)面偏離角度表明此時(shí)車輛的偏航靈敏性，并反映為轉(zhuǎn)向角度，轉(zhuǎn)向角度隨著車輛偏離角度的增大而減小。一旦偏離角度超過某一限度，駕駛員就很難重新進(jìn)行操作。在干燥的路面偏離角度不能夠

16、超過10度，而在積雪路面上極限偏離角度為4度。</p><p>　　多數(shù)司機(jī)沒有從制動中恢復(fù)的經(jīng)驗(yàn)。他們不知道輪胎和地面之間的摩擦系數(shù)，更不知道他們的車的側(cè)緣穩(wěn)定邊界。當(dāng)極限被沖破時(shí)，駕駛員通常會很緊張以至于做出錯(cuò)誤的反應(yīng)。ITT的格雷柏解釋說：“過度轉(zhuǎn)向引起車輛擺尾，使汽車更快的失控。ASMS傳感器能夠快速的檢測到制動開始時(shí)各個(gè)車輪的活動，從而使車輛恢復(fù)到穩(wěn)定行駛軌道。</p><p>

17、　　對于穩(wěn)定調(diào)節(jié)系統(tǒng)界面的可操作性是很重要的，這樣可以預(yù)示帶有穩(wěn)定系統(tǒng)的駕駛和普通駕駛給人的感覺沒有什么區(qū)別。</p><p>　　穩(wěn)定系統(tǒng)最大的優(yōu)點(diǎn)在于速度，它不僅可以對制動作出快速反應(yīng)，還可以對車輛狀況（例如車重變化，輪胎磨損），路面質(zhì)量作出快速反應(yīng)統(tǒng)就能夠通過改變側(cè)面受力平橫處理，達(dá)到最好的駕駛穩(wěn)定性。</p><p>　　穩(wěn)定系統(tǒng)識別駕駛員想達(dá)到的（理想路線）和車輛實(shí)際行駛路線（實(shí)

18、際路線）的不同，目前的汽車需要一套高效的傳感器和一臺高效處理信息的處理器。</p><p>　　博世公司的VDC/ESP電子控制單元是一個(gè)由兩個(gè)48兆的ROM組成的傳統(tǒng)實(shí)驗(yàn)電路板。范桑特說：“48KB的內(nèi)存容量是大量用以完成設(shè)計(jì)任務(wù)的‘智能’的代表”。他在SAE中指出。ABS防抱死系統(tǒng)是獨(dú)立的，只提供四分之一的這樣的容量，而ABS和牽引控制系統(tǒng)組合在一起的容量只有這個(gè)軟件容量的一半。</p><

19、;p>　　除了ABS防抱死系統(tǒng)和牽引控制系統(tǒng)所具有的關(guān)系傳感器外，VDC/ESP運(yùn)用了偏航比率傳感器，橫向加速度傳感器，轉(zhuǎn)向角傳感器，制動壓力傳感器來獲取汽車方向盤上的傳感器由一組安裝在方向盤上的發(fā)光二極管和光敏二極管上組成。一只硅壓力傳感器通過控制前輪剎車內(nèi)壓力油的壓力控制制動壓力（因?yàn)橹栖噳毫碓从隈{駛員）。</p><p>　　確定車輛實(shí)際的行駛路線是一項(xiàng)非常復(fù)雜的工作。通過必須的縱向滑動車輪速度傳

20、感器提供給反向制動或者牽引控制系統(tǒng)的車輪轉(zhuǎn)速信號，以對可能發(fā)生的動作作出精確的分析，無論如何側(cè)向難預(yù)料的運(yùn)動分析是必須的，所以系統(tǒng)必須再拓展兩個(gè)額外的傳感器---偏航比率傳感器和側(cè)向加速度傳感器。</p><p>　　橫向加速度表檢測沿曲線行駛時(shí)所帶來的受力狀況。這種類似的傳感器通過一臺直線霍爾發(fā)電機(jī)把彈簧的直線運(yùn)動轉(zhuǎn)變成電信號來實(shí)現(xiàn)對彈簧機(jī)構(gòu)的控制。這種傳感器必須很靈敏，它的控制角為±1.4g。<

21、;/p><p>　　最新的穩(wěn)定調(diào)節(jié)系統(tǒng)的核心在于類似于陀螺儀的偏航比率回轉(zhuǎn)儀。傳感器測量車輛對豎直軸的旋轉(zhuǎn)。這個(gè)測量原理來源于航空工業(yè)，并且被博施公司大規(guī)模的應(yīng)用于汽車工業(yè)。現(xiàn)有的回轉(zhuǎn)儀市場提供兩種選擇，一種是應(yīng)用與航空航天業(yè)的價(jià)值6000美元（由位于英國羅徹斯特的美國通用電器公司航空股份有限公司提供），另一種是用于照相機(jī)的價(jià)值160美元。由SAE報(bào)得知博施公司采取一種圓柱形設(shè)計(jì)方案以實(shí)現(xiàn)低成本下的高性能。這種傳感器

22、需要一項(xiàng)更大的投資以應(yīng)對汽車所處的極端環(huán)境狀態(tài)。同時(shí)偏航比率回轉(zhuǎn)儀的價(jià)格必須降低，這樣才能充分應(yīng)用與汽車。</p><p>　　偏航比率回轉(zhuǎn)儀有一個(gè)復(fù)雜的內(nèi)部結(jié)構(gòu)，其內(nèi)部是有一個(gè)很小的圓柱形鋼管伺服測量元件。圓柱的薄壁上有壓電元件能夠在15千赫茲的頻率下震動。四對這樣的感應(yīng)器安放在圓柱體的周圍，一對元件的位置與另一對的位置相對。其中的一對通過應(yīng)用正弦電壓引起柱體在其固有頻率下產(chǎn)生共振，并將振動傳送給變頻器。在每一

23、對傳感器之間，振顫節(jié)點(diǎn)繞著汽車的垂直軸作細(xì)微的運(yùn)動。這時(shí)如果沒有偏航輸入，震動曲線就是一條穩(wěn)定的曲線。如果有信號輸入，節(jié)點(diǎn)的位置和曲線的波谷就會在相對的防線繞著圓筒壁做旋轉(zhuǎn)運(yùn)動（科里奧利加速度）。這個(gè)輕微的位移就會成為汽車偏航比率的度量標(biāo)準(zhǔn)。</p><p>　　許多司機(jī)都相互宣傳他們的車輛在光滑轉(zhuǎn)彎處，車尾部將要被甩出去的時(shí)候，新系統(tǒng)會把車輛“推”回到正確的軌跡上方面的經(jīng)驗(yàn)。 </p><p

24、>　　許多觀察員指出，穩(wěn)定調(diào)節(jié)系統(tǒng)可能會使司機(jī)在較低摩擦力的路面上過分自信，盡管他們占少數(shù)?；蛟S需要指導(dǎo)司機(jī)怎樣來恰當(dāng)?shù)氖褂密囕v穩(wěn)定調(diào)節(jié)系統(tǒng)。就像當(dāng)初讓司機(jī)學(xué)習(xí)不能向防抱死制動系統(tǒng)里泵油一樣。</p><p>　　雖然只介紹了很少的關(guān)于為未來汽車研制的新一代主動安全系統(tǒng)（遠(yuǎn)遠(yuǎn)超過了雷達(dá)掃描儀類似的系統(tǒng)），但避免交通事故仍然是汽車安全工程的主題。美國國際電信公司負(fù)責(zé)人指出“當(dāng)穩(wěn)定調(diào)節(jié)技術(shù)伴隨著汽車結(jié)構(gòu)全面性能

25、穩(wěn)步提高的時(shí)候，多數(shù)可避免的事故將不再發(fā)生了”。新一代的安全系統(tǒng)也會起到同樣的效果。</p><p>　　本文摘自： 《Automobile Application Engineering》 </p><p>　　Spin control for cars</p><p>　　Stability control systems are the lates

26、t in a string of technologies focusing on improved dirving safety. Such systems detect the initial phases of a skid and restore directional control in 40 milliseconds, seven times faster than the reaction time of the ave

27、rage human. They correct vehicle paths by adjusting engine torque or applying the left- or-right-side brakes, or both, as needed. The technology has already been applied to the Mercedes-Benz S600 coupe.</p><p&

28、gt;　　Automatic stability systems can detect the onset of a skid and bring a fishtailing vehicle back on course even before its driver can react. </p><p>　　Safety glass, seat belts, crumple zones, air bags, a

29、ntilock brakes, traction control, and now stability control. The continuing progression of safety systems for cars has yielded yet another device designed to keep occupants from injury. Stability control systems help dri

30、vers recover from uncontrolled skids in curves, thus avoiding spinouts and accidents. </p><p>　　Using computers and an array of sensors, a stability control system detects the onset of a skid and restores di

31、rectional control more quickly than a human driver can. Every microsecond, the system takes a "snapshot," calculating whether a car is going exactly in the direction it is being steered. If there is the slighte

32、st difference between where the driver is steering and where the vehicle is going, the system corrects its path in a split-second by adjusting engine torque and/or applying the ca</p><p>　　A stability contro

33、l system senses the driver's desired motion from the steering angle, the accelerator pedal position, and the brake pressure while determining the vehicle's actual motion from the yaw rate (vehicle rotation about

34、its vertical axis) and lateral acceleration, explained Anton project leader of the Robert Bosch engineering team. Van group and a team of engineers from Mercedes-Benz, led by project manager Armin Muller, developed the

35、first fully effective stability control system, wh</p><p>　　Automotive safety experts believe that stability control systems will reduce the number of accidents, or at least the severity of damage. Safety st

36、atistics say that most of the deadly accidents in which a single car spins out (accounting for four percent of all deadly collisions) could be avoided using the new technology. The additional cost of the ne systems are o

37、n the order of the increasingly popular antilock brake/traction control units now available for cars. </p><p>　　The debut of stability control technology took place in Europe on the Mercedes-Benz S600 coupe

38、this spring. Developed jointly during the past few years by Rober Bosch GmbH and Mercedes-Benz AG, both of Stuttgart, Germany, Vehicle Dynamics Control (VDC). in Bosch terminology, or the Electronic Stability Program (ES

39、P), as Mercedes calls it, maintains vehicle stability in most driving situations. Bosch developed the system, and Mercedes-Benz integrated it into the vehicle. Mercedes engineers used t</p><p>　　Stability co

40、ntrol systems will first appear in mid-1995 on some European S-Class models and will reach the U.S. market during the 1996 model year (November 1995 introduction). It will be available as a $750 option on Mercedes models

41、 with V8 engines, and the following year it will be a $2400 option on six-cylinder $1650 of the latter price is for the traction control system, a prerequisite for stability control.</p><p>　　Bosch is not al

42、one in developing such a safety system. ITT Automotive of Auburn Hills, Mich., introduced its Automotive Stability Management System (ASMS) in January at the 1995 North American International Auto Show in Detroit. "

43、ASMS is a quantum leap in the evolution of antilock brake systems, combining the best attributes of ABS and traction control into a total vehicle dynamics management system," said Timothy D. Leuliette, ITT Automotiv

44、e's president and chief executive officer. </p><p>　　"ASMS monitors what the vehicle controls indicate should be happening, compares that to what is actually happening, then works to compensate for

45、the difference," said Johannes Graber, ASMS program manager at ITT Automotive Europe. ITT's system should begin appearing on vehicles worldwide near the end of the decade, according to Tom Mathues, director of e

46、ngineering of Brake & Chassis Systems at ITT Automotive North America. Company engineers are now adapting the system to specific car models from</p><p>　　A less-sophisticated and less-effective Bosch sta

47、bility control system already appears on the 1995 750iL and 850Ci V-12 models from Munich-based BMW AG. The BMW Dynamic Stability Control (DSC) system uses the same wheel-speed sensors as traction control and standard an

48、ti-lock brake (ABS) systems to recognize conditions that can destabilize a vehicle in curves and corners. To detect such potentially dangerous cornering situations, DSC measures differences in rotational speed between th

49、e two front</p><p>　　The new Bosch and ITT Automotive stability control systems benefit from advanced technology developed for the aerospace industry. Just as in a supersonic fighter, the automotive stabilit

50、y control units use a sensor-based computer system to mediate between the human controller and the environment - in this case, the interface between tire and road. In addition, the system is built around a gyroscopelike

51、sensor design used for missile guidance. </p><p>　　BEYOND ABS AND TRACTION CONTROL </p><p>　　Stability control is the logical extension of ABS and traction control, according to a Society of Aut

52、omotive Engineers paper written by van Zanten and Bosch colleagues Rainer Erhardt and Georg Pfaff. Whereas ABS intervenes when wheel lock is imminent during braking, and traction control prevents wheel slippage when acce

53、lerating, stability control operates independently of the driver's actions even when the car is free-rolling. Depending on the particular driving situation, the system may activat</p><p>　　The idea behin

54、d the three active safety systems is the same: One wheel locking or slipping significantly decreases directional stability or makes steering a vehicle more difficult. If a car must brake on a low-friction surface, lockin

55、g its wheels should be avoided to maintain stability and steerability. </p><p>　　Whereas ABS and traction control prevent undesired longitudinal slip, stability control reduces loss of lateral stability. If

56、the lateral forces of a moving vehicle are no longer adequate at one or more wheels, the vehicle may lose stability, particularly in curves. What the drive "fishtailing" is primarily a turning or spinning

57、around the vehicle's axis. A separate sensor must recognize this spinning, because unlike ABS and traction control, a car's lateral movement cannot be calculated from it</p><p>　　SPIN HANDLERS </p

58、><p>　　The new systems measure any tendency toward understeer (when a car responds slowly to steering changes), or over-steer (when the rear wheels try to swing around). If a car understeers and swerves off cou

59、rse when driven in a curve, the stability control system will correct the error by braking the inner (with respect to the curve) rear wheel. This enables the driver, as in the case of ABS, to approach the locking limit o

60、f the road-tire interface without losing control of the vehicle. The stabilit</p><p>　　The influence of side slip angle on maneuverability, the Bosch researchers explained, shows that the sensitivity of the

61、yaw moment on the vehicle, with respect to changes in the steering angle, decreases rapidly as the slip angle of the vehicle increases. Once the slip angle grows beyond a certain limit, the driver has a much harder time

62、recovering by steering. On dry surfaces, maneuverability is lost at slip-angle values larger than approximately 10 degrees, and on packed snow at approximately </p><p>　　Most drivers have little experience r

63、ecovering from skids. They aren't aware of the coefficient of friction between the tires and the road and have no idea of their vehicle's lateral stability margin. When the limit of adhesion is reached, the drive

64、r is usually caught by surprise and very often reacts in the wrong way, steering too much. Oversteering, ITT's Graber explained, causes the car to fishtail, throwing the vehicle even further out of control. ASMS sens

65、ors, he said, can quickly detect th</p><p>　　It is important that stability control systems be user-friendly at the limit of adhesion - that is, to act predictably in a way similar to normal driving. </p&

66、gt;<p>　　The biggest advantage of stability control is its speed - it can respond immediately not only to skids but also to shifting vehicle conditions (such as changes in weight or tire wear) and road quality. Th

67、us, the systems achieve optimum driving stability by changing the lateral stabilizing forces. </p><p>　　For a stability control system to recognize the difference between what the driver wants (desired cours

68、e) and the actual movement of the vehicle (actual course), current cars require an efficient set of sensors and a greater computer capacity for processing information. </p><p>　　The Bosch VDC/ESP electronic

69、control unit contains a conventional circuit board with two partly redundant microcontrollers using 48 kilobytes of ROM each. The 48-kB memory capacity is representative of the large amount of "intelligence" re

70、quired to perform the design task, van Zanten said. ABS alone, he wrote in the SAE paper, would require one-quarter of this capacity, while ABS and traction control together require only one half of this software capacit

71、y. </p><p>　　In addition to ABS and traction control systems and related sensors, VDC/ESP uses sensors for yaw rate, lateral acceleration, steering angle, and braking pressure as well as information on wheth

72、er the car is accelerating, freely rolling, or braking. It obtains the necessary information on the current load condition of the engine from the engine controller. The steering-wheel angle sensor is based on a set of LE

73、D and photodiodes mounted in the steering wheel. A silicon-micromachine pressure senso</p><p>　　Determining the actual course of the vehicle is a more complicated task. Wheel speed signals, which are provide

74、d for antilock brakes/traction control by inductive wheel speed sensors, are required to derive longitudinal slip. For an exact analysis of possible movement, however, variables describing lateral motion are needed, so t

75、he system must be expanded with two additional sensors - yaw rate sensors and lateral acceleration sensors. </p><p>　　A lateral accelerometer monitors the forces occurring in curves. This analog sensor opera

76、tes according to a damped spring-mass mechanism, by which a linear Hall generator transforms the spring displacement into an electrical signal. The sensor must be very sensitive, with an operating range of plus or minus

77、1.4 g. </p><p>　　YAW RATE GYRO </p><p>　　At the heart of the latest stability control system type is the yaw rate sensor, which is similar in function to a gyroscope. The sensor measures the spe

78、ed at which the car rotates about its vertical axis. This measuring principle originated in the aviation industry and was further developed by Bosch for large-scale vehicle production. The existing gyro market offers two

79、 widely different categories of devices: $6000 units for aerospace and navigation systems (supplied by firms such as GEC Marcon</p><p>　　The yaw rate sensor has a complex internal structure centered around a

80、 small hollow steel cylinder that serves as the measuring element. The thin wall of the cylinder is excited with piezoelectric elements that vibrate at a frequency of 15 kilohertz. Four pairs of these piezo elements are

81、arranged on the circumference of the cylinder, with paired elements positioned opposite each other. One of these pairs brings the open cylinder into resonance vibration by applying a sinusoidal voltage at its n</p>

82、<p>　　Several drivers who have had hands-on experience with the new systems in slippery cornering conditions speak of their cars being suddenly nudged back onto the right track just before it seems that their back

83、 ends might break away. </p><p>　　Some observers warn that stability controls might lure some drivers into overconfidence in low-friction driving situations, though they are in the minority. It may, however,

84、 be necessary to instruct drivers as to how to use the new capability properly. Recall that drivers had to learn not to "pump" antilock brake systems. </p><p>　　Although little detail has been repo

85、rted regarding next-generation active safety systems for future cars (beyond various types of costly radar proximity scanners and other similar systems), it is clear that accident-avoidance is the theme for automotive sa

86、fety engineers. "The most survivable accident is the one that never happens," said ITT's Graber. "Stability control technology dovetails nicely with the tremendous strides that have been made to the ph