外文翻譯---汽車的轉(zhuǎn)向控制

1、<p><b>　　翻譯論文</b></p><p><b>　　汽車的轉(zhuǎn)向控制</b></p><p>　　全文：版權(quán)所有1995年美國機械工程師學(xué)會</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。這個系統(tǒng)能夠在40毫秒內(nèi)實現(xiàn)從制動開始到制動恢復(fù)的過程，這個時間是人的反應(yīng)時

2、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，來實現(xiàn)準(zhǔn)確的行車路線。這個系統(tǒng)已被應(yīng)用于奔馳S600汽車了。</p><p>　　穩(wěn)定的機械自動系統(tǒng)能夠在制動時發(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)節(jié)系統(tǒng)。汽車安全系統(tǒng)的連續(xù)升級，已經(jīng)

3、產(chǎn)生了一種為保護汽車所有者安全的設(shè)計模式。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>　　利用計算機和一系列傳感器，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微小的偏差 ，系統(tǒng)會在瞬間糾正發(fā)動機扭矩或者

4、應(yīng)用汽車左右制動。過程的標(biāo)準(zhǔn)反應(yīng)時間是40毫秒----人的平均反應(yīng)時間的七分之一。</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：“一個穩(wěn)定的控制系統(tǒng)能夠‘感覺到”駕駛員想要運動的方向，通過控制轉(zhuǎn)向角度，油門踏板的位置，制動板的狀態(tài)來確定汽車實際運動路線的偏航比率(汽車偏離方向軸的角度)和橫向加速度”。項目負(fù)責(zé)人阿明·馬勒領(lǐng)導(dǎo)著范桑特的工作小組和奔馳汽車公司的工程

5、師發(fā)明了第一個完全有效的穩(wěn)定調(diào)節(jié)系統(tǒng)，該系統(tǒng)由發(fā)動機扭矩控制系統(tǒng)，制動系統(tǒng)，牽引控制系統(tǒng)組成以實現(xiàn)理想與現(xiàn)實運動之間的最小差距。</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)用這項新技術(shù)避免。這項新系統(tǒng)的額外費用主要用于一系列目前汽車日益普遍應(yīng)用的制動/牽引控制鎖組件。</p&

6、gt;<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)進行評估，例如極強的側(cè)風(fēng)。然后他們在瑞典的安杰普勞附

7、近的后娜瓦安湖的冰面上進行性能測試。工作通常是在公路上進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用的V8發(fā)動機上的，也可以選擇價格為2400美元的應(yīng)用于六缸發(fā)動機汽車的系統(tǒng)。后者的系統(tǒng)中差不多有1650美元是用于牽引控制系統(tǒng)

8、，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，事實上那已經(jīng)實現(xiàn)了，不同的是兩者的費用不同”，美國國際電信公司駐歐洲空對地導(dǎo)彈控制工程負(fù)責(zé)人約翰尼斯·格雷得說

9、。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)運用的車輪速度傳感器同牽引控制系統(tǒng)和標(biāo)準(zhǔn)ABS防抱死系統(tǒng)一

10、樣能夠識別外部情況，使車輛更容易實現(xiàn)曲線行駛和轉(zhuǎn)彎。為了檢測出車輛轉(zhuǎn)彎時潛在的危險，DSC系統(tǒng)檢測的是兩前輪在轉(zhuǎn)彎時的速度差，DSC系統(tǒng)添加了一個更高級的角度傳感器利用現(xiàn)有的一個車輛速度，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，汽車的穩(wěn)定調(diào)節(jié)單元運用一個基于計算機系統(tǒng)的傳感

11、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)的合理擴展。但是ABS系統(tǒng)的作用發(fā)生在制動時車輪轉(zhuǎn)向?qū)⒈绘i死時，

12、牽引控制是預(yù)防加速時的車輪滑動，穩(wěn)定系統(tǒng)是當(dāng)汽車自由轉(zhuǎn)向時能獨立于駕駛員作出操作。依靠不同的駕駛狀況系統(tǒng)可以使每個車輪制動或者迅速使四個輪轉(zhuǎn)速適合于發(fā)動機的扭矩，從而使車輛穩(wěn)定和減少由于制動失控帶來的危險。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)所遠遠不能達到的。</p><p>　　三種主動的安全系統(tǒng)的作用時刻是一致的，那就是

13、一個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€或者更多輪上，車輛就會失穩(wěn)，尤其是車輛沿曲線行駛時。駕駛員感覺到的“搖擺”起初是轉(zhuǎn)彎或者與車的軸線形成一個紡錘形時。一個獨

14、立的傳感器必須能夠識別這個“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)生來回擺動)。當(dāng)車輛在轉(zhuǎn)向時如果發(fā)生不足轉(zhuǎn)向和過度轉(zhuǎn)向運動時，穩(wěn)定調(diào)節(jié)系統(tǒng)能夠通過后輪進行內(nèi)部制動(針

15、對曲線)糾正錯誤。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行操作。在干燥的路面偏離角度不能夠超過10度，而在積雪路面上極限偏離角度為

16、4度。</p><p>　　多數(shù)司機沒有從制動中恢復(fù)的經(jīng)驗。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，駕駛員通常會很緊張以至于做出錯誤的反應(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各個車輪的活動，從而使車輛恢復(fù)到穩(wěn)定行駛軌道。</p><p>　　對于穩(wěn)定調(diào)節(jié)系統(tǒng)界面的可操作性是很重

17、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)識別駕駛員想達到的(理想路線)和車輛實際行駛路線(實際路線)的不同，目前的汽車需要一套高效的

18、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由兩個48兆的ROM組成的傳統(tǒng)實驗電路板。范桑特說：“48KB的內(nèi)存容量是大量用以完成設(shè)計任務(wù)的‘智能’的代表”。他在SAE中指出。ABS防抱死系統(tǒng)是獨立的，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軟件容量的一半。</p><p>　　除了ABS防抱死系統(tǒng)和牽

19、引控制系統(tǒng)所具有的關(guān)系傳感器外，VDC/ESP運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的加速，搖擺或者剎車的信息。系統(tǒng)通過管理員獲得所需的通常的路面信息。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(因為制車壓力來源于駕駛員)。</p><p>　　確定車輛實際的行駛路線是一項非常復(fù)雜的工作。

20、通過必須的縱向滑動車輪速度傳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)料的運動分析是必須的，所以系統(tǒng)必須再拓展兩個額外的傳感器---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)電機把彈簧的直線運動轉(zhuǎn)變成電信號來實現(xiàn)對彈簧機構(gòu)的控制。這種傳感器必須很靈敏，它的控制角為

21、±1.4g。</p><p><b>　　偏航比率回轉(zhuǎn)儀</b></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

22、公司提供)，另一種是用于照相機的價值160美元。由SAE報得知博施公司采取一種圓柱形設(shè)計方案以實現(xiàn)低成本下的高性能。這種傳感器需要一項更大的投資以應(yīng)對汽車所處的極端環(huán)境狀態(tài)。同時偏航比率回轉(zhuǎn)儀的價格必須降低，這樣才能充分應(yīng)用與汽車。</p><p>　　偏航比率回轉(zhuǎn)儀有一個復(fù)雜的內(nèi)部結(jié)構(gòu)，其內(nèi)部是有一個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

23、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。在每一對傳感器之間，振顫節(jié)點繞著汽車的垂直軸作細微的運動。這時如果沒有偏航輸入，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)運動(科里奧利加速度)。這個輕微的位移就會成為汽車偏航比率的度量標(biāo)準(zhǔn)。</p><p>　　許多司機都相互宣傳他們的車

24、輛在光滑轉(zhuǎn)彎處，車尾部將要被甩出去的時候，新系統(tǒng)會把車輛“推”回到正確的軌跡上方面的經(jīng)驗。 </p><p>　　許多觀察員指出，穩(wěn)定調(diào)節(jié)系統(tǒng)可能會使司機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)(遠遠超過了雷

25、達掃描儀類似的系統(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)全面性能穩(wěn)步提高的時候，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>　　Spin control for cars</p><p>　　Stability control systems are the latest in a st

26、ring of technologies focusing on improved diriving 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 average hum

27、an. 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>　　Aut

28、omatic 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, antilock

29、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 drivers rec

30、over 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 directiona

31、l 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 slightest diffe

32、rence 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 control system

33、 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 its vert

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

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

36、tics 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 new systems are on t

37、he 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 thi

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

39、, 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 </p><p>　　Stability contr

40、ol 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 wi

41、th 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 alone

42、 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. "ASM

43、S 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 Automotive&#

44、39;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 the

45、 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 engi

46、neering 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 stabil

47、ity 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 anti-

48、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 the t

49、wo 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 stability c

50、ontrol 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 sen

51、sor 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 Automot

52、ive 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 accelera

53、ting, 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 behind th

54、e 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, locking it

55、s 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 the

56、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 aro

57、und 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 i</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 course

59、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 of th

60、e 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 yaw

61、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 reco

62、vering 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 recov

63、ering 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 driver is

64、 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 sensors,

65、 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、<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. Thus,

67、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 course) a

68、nd 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 cont

69、rol 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" requir

70、ed 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 capacity. &

71、lt;/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 whether t

72、he 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 LED an

73、d 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 provided fo

74、r 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 the s

75、ystem 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 operates

76、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 1.4

77、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 speed at

78、 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 wide

79、ly 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 smal

80、l 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 arran

81、ged 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 ends

83、 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, be n

84、ecessary 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 reported

85、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 safety

86、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 physica