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二 ○ ○ 七 屆 畢 業(yè) 設(shè) 計 中型客車乘客門和行李艙門設(shè)計 學(xué) 院：汽車學(xué)院 專 業(yè)：車輛工程 姓 名：鐘 海 學(xué) 號：2201030219 指導(dǎo)教師：郭應(yīng)時 完成時間：2007.06. 二〇〇七年六月 長安大學(xué)畢業(yè)設(shè)計（論文）開題報告表 課題名稱 中型客車車門總成設(shè)計 課題來源 自己選定 課題類型 造型設(shè)計 指導(dǎo)教師 郭應(yīng)時（老師） 學(xué)生姓名 鐘 海 學(xué) 號 2201030219 專 業(yè) 車輛工程 (內(nèi)容包括：課題的意義，國內(nèi)外發(fā)展狀況，本課題的研究內(nèi)容、方法、手段及預(yù)期成果，任務(wù)完成的階段安排及時間安排，完成任務(wù)所具備的條件因素等。） 一．課題的意義 乘客門是客車的重要組成部分，是乘客上下車的通道，對客車的整體造型也起著重要的協(xié)調(diào)作用?？蛙囃庑问怯绊懣蛙囆阅艿囊粋€重要因素。乘客門是車身外形的一個組成部分，它不僅與客車的動力性、經(jīng)濟性密切相關(guān)，而且直接影響客車外形的美觀與動感。 二．國內(nèi)外發(fā)展狀況　 外擺式乘客門有無軌道移出式車門和有軌道式車門，目前主要使用的是一種無軌道的移出車門，門扇靠回轉(zhuǎn)臂支撐，依靠轉(zhuǎn)軸的轉(zhuǎn)動帶動門扇作近似于平行移動的運動，因而也稱為平移門。它主要由門扇、支臂、 導(dǎo)向拉桿、 鎖止機構(gòu)等組成。 車門門體采用輕質(zhì)鋁合金材料。門體骨架由鋁合金型材經(jīng)氬弧焊組焊而成，門體的內(nèi)外蒙皮采用1.0mm的薄鋁板，使整個門體重量大大減輕。車門采用雙層密封，雙向的，鑲嵌在鋁型材槽中的車門密封條很好的保證了車門的密封。車門開度大，開關(guān)輕便、靈巧、安全，車門關(guān)閉后，門體與整車外觀協(xié)調(diào)，使整車的外表面平整，整車造型更加美觀，既減小了空氣阻力，又防止了高速行駛產(chǎn)生較大的風(fēng)流噪聲。 轉(zhuǎn)軸、轉(zhuǎn)臂、下拉桿與車門體相連接，不但起到支撐門體的作用，還利用四連桿機構(gòu)原理來實現(xiàn)車門的無軌道平移。轉(zhuǎn)軸與轉(zhuǎn)臂均采用優(yōu)質(zhì)鋼管，表面噴塑處理，使之與車內(nèi)飾相協(xié)調(diào)。為了防止裝配誤差影響車門的運動，各傳動桿件的鉸接點均設(shè)計為可調(diào)節(jié)的結(jié)構(gòu)，在安裝中可通過適當?shù)恼{(diào)整，以保證車門運動的準確性。 鎖止機構(gòu)是由裝在門體兩側(cè)的鎖止塊與安裝在前后門框上的鎖止塊組成。當車門完全關(guān)閉后，由門泵轉(zhuǎn)軸帶動車門向上移動，鎖止塊相互鍥合進入鎖止狀態(tài)。 隨著國內(nèi)客車行業(yè)迅速發(fā)展，中、高檔次客車需求的不斷增加，中、高檔豪華客車的開發(fā)成為各客車生產(chǎn)廠家的熱點。為了不斷提高客車的豪華程度，大客車外擺門成為眾多客車生產(chǎn)廠家關(guān)注的重點，豪華型大客車采用外擺門成為一種趨勢。它與折疊式乘客門相比有以下優(yōu)點： 1． 外擺式車門是把車門整體旋轉(zhuǎn)外移，車門開度大，可以開啟到門框?qū)挾?，有效利用門框空間，使踏步寬敞，保證乘客上下車方便。 2． 外擺門采用雙層密封，具有良好的密封性，密封結(jié)構(gòu)簡單。 3． 車門開啟和關(guān)閉的動作柔和，運動平順，且設(shè)有防夾裝置，開關(guān)方便、安全，操縱靈巧。 4． 剛性較好、不易變形下沉，行車時不易產(chǎn)生振動噪聲。 5． 外形與整車協(xié)調(diào)，無凹陷，克服了凹陷于車身內(nèi)的折疊式車門的空氣渦流，改善了客車的空氣動力學(xué)性能，行車時空氣阻力小，風(fēng)噪小，且造型美觀，在客車高速運行時可以提高客車的經(jīng)濟性和功率利用率。 以前國產(chǎn)的大中型及輕型的客車上用得最多的是折疊式乘客門，但這種車門由于其運動特點限制了其門扇的形狀只能是平板形的，而且其轉(zhuǎn)軸必須垂直于地板。因此裝上車身后，必然凹陷于車身內(nèi)，無法與車身外形保持平齊。這樣不僅從造型上顯得不協(xié)調(diào)不美觀，而且在行使時氣流在凹陷處形成漩渦，影響整車的空氣動力性，增加行駛阻力，產(chǎn)生風(fēng)噪。而外擺門克服了這些缺點，它的這些優(yōu)點使得它在各種客車上的應(yīng)用更加廣泛，在客車技術(shù)高速發(fā)展的今天，可以說代表著客車乘客門技術(shù)發(fā)展的一種趨勢。 三．設(shè)計內(nèi)容 依據(jù)底盤總布置方案，在與車身總布置設(shè)計充分協(xié)調(diào)的基礎(chǔ)上，參考國內(nèi)外現(xiàn)有同類車型的造型特征和相關(guān)結(jié)構(gòu)，結(jié)合生產(chǎn)企業(yè)的工藝特點，確定所設(shè)計的車門、行李倉門的主要結(jié)構(gòu)形式和布置方式。 四．設(shè)計方法及手段 使用AutoCAD設(shè)計軟件進行中型客車車門總成及行李倉門造型設(shè)計。 五．預(yù)期成果 在總布置設(shè)計的前提下完成中型客車車門總成造型設(shè)計，并在時間充裕的條件下對車門及行李倉門進行造型設(shè)計，進一步改善門安全性和合理性。 六．任務(wù)完成的階段安排及時間安排 序號 設(shè)計（論文）各階段名稱 日期（教學(xué)周） 1． 調(diào)研，資料收集與整理 4.9-4.20 （6、7） 2． 方案設(shè)計與可行性論證 4.23-5.11 （7-8） 3． 軟件學(xué)習(xí)、造型設(shè)計 5.14-6.15 （11-15） 4． 撰寫畢業(yè)設(shè)計說明書 5.12-5.13 （15） 5． 設(shè)計及論文修改，評審，答辯 6.18-6.22 （16） 七．完成任務(wù)所需要的資料 設(shè)計原始資料：總布置相關(guān)數(shù)據(jù)資料 。 同類型客車的有關(guān)設(shè)計文件。 主要參考資料： 1. 黃天澤主編， 汽車車身結(jié)構(gòu)與設(shè)計， 機械工業(yè)出版社 2. 黃天澤， 大客車車身， 湖南大學(xué)出版社 3. 余志生主編， 汽車理論， 機械工業(yè)出版社 4. 張洪欣主編， 汽車設(shè)計， 機械工業(yè)出版社 5. 陳士俊主編， 產(chǎn)品造型設(shè)計原理與方法，天津大學(xué)出版社 6. 相關(guān)文獻資料和設(shè)計手冊 7. 相關(guān)產(chǎn)品樣本 指導(dǎo)教師意見及建議： 指導(dǎo)教師簽名： 年 月 日 注：1、課題來源分為：國家重點、省部級重點、學(xué)?？蒲?、校外協(xié)作、實驗室建設(shè)和自選項目；課題類型分為：工程設(shè)計、專題研究、文獻綜述、綜合實驗。 2、此表由學(xué)生填寫，交指導(dǎo)教師簽署意見后方可開題。 摘 要 乘客門是客車的重要組成部分，是乘客上下車的通道，對客車的整體造型也起著重要的協(xié)調(diào)作用。隨著我國汽車技術(shù)的發(fā)展，我國汽車廠家已普遍采用了優(yōu)勢突出的外擺式乘客門。外擺式乘客門是一種無軌道的移出車門，門扇靠回轉(zhuǎn)臂支撐，依靠轉(zhuǎn)軸的轉(zhuǎn)動帶動門扇作近似于平行移動的運動，因而也稱為平移門。 本文為中型客車的外擺式乘客門和行李艙門的設(shè)計。分析了外擺式乘客門和行李艙門的結(jié)構(gòu)和工作原理，確定其各部分的尺寸及主要零部件的選型及安裝。討論了國內(nèi)外汽車附件工業(yè)發(fā)展的情況比較。AUTOCAD軟件是當今世界上一種主流的設(shè)計軟件之一。在本設(shè)計中應(yīng)用了AUTOCAD軟件制作乘客門和行李艙門。 關(guān)鍵詞： 外擺門，行李艙門, 安全，AUTOCAD。 Abstract Passenger door is the important department of the coach, is the route way for the passengers. And assort with the whole coach sculpt. With the development of our vehicle technology, the domestic vehicle factory has already adopted the outer turning service door. It has much more predominance. The outer turning service door is the door which has no tram road and parallel move out of the coach, the door was supported by the circumrotate arm. By the rotation of the circumrotate axes, the door is moving close to the parallel move. Thus this door is called translation door. This paper introduces the design of the medium passenger train coach’s outer turning service door and the engine hatch door. Analyzed the structure and operating principles of the outer turning service door and the engine hatch door, determined the size of its parts and major components of the models and installation. Discussed the development of the vehicle annex industry. AUTOCAD software is one of a mainstream in the world of design software. During the design, the AUTOCAD software has been sued to product passenger door and baggage compartment door. KEY WORDS: outer turning service door, baggage compartment door, safe, AUTOCAD。 目 錄 第一章 緒論························································1 1.1 乘客門類型選擇················································1 1.1.1乘客門主要結(jié)構(gòu)形式·········································1 1.1.2 外擺門的優(yōu)點··············································2 1.2 CAD 技術(shù)在汽車開發(fā)中的應(yīng)用····································2 1.2.1CAD技術(shù)的發(fā)展············································2 第二章 國內(nèi)外外發(fā)展情況比較·······································3 2.1客車附件工業(yè)的特點···········································3 2.2 目前國內(nèi)客車車身附件的狀況及與國外發(fā)達國家之間的差距·········3 2.3發(fā)展建議·····················································6 第三章 外擺式乘客門設(shè)計···········································7 3.1 外擺式乘客門的結(jié)構(gòu)···········································7 3.2乘客門泵選型··················································8 3.2.1 門泵主要技術(shù)參數(shù)··········································9 3.2.2 門泵安裝與調(diào)試············································10 3.3運動機構(gòu)設(shè)計及校核···········································10 3.3.1用作圖法確定車門的運動軌跡·······························10 3.3.2運動校核··················································13 3.4 外擺門的密封·················································14 3.4.1幾種典型外擺式乘客門密封結(jié)構(gòu)·····························14 3.4.2改進型密封結(jié)構(gòu)···········································16 3.4.3密封結(jié)構(gòu)選定 ···········································17 3.5 外擺式乘客門的制作···········································18 3.5.1制作工藝·················································18 3.5.2預(yù)裝與調(diào)試················································18 第四章 發(fā)動機艙門設(shè)計·············································18 4.1艙門結(jié)構(gòu)組成·················································18 4.2零部件選型····················································18 4.2.1鎖 具 的 選 擇················································18 4.2.2氣彈簧支撐機構(gòu)·············································20 4.3鉸鏈設(shè)計·····················································21 設(shè)計評價分析····················································23 致 謝··························································24 參考文獻··························································25 ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ 裝 ┊ ┊ ┊ ┊ ┊ 訂 ┊ ┊ ┊ ┊ ┊ 線 ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ 畢業(yè)設(shè)計（論文）報告紙 利用只裝有車輪速度傳感器的制動 防抱死系統(tǒng)做路面情況鑒定 摘要： 制動防抱死系統(tǒng)(ABS),是目前在汽車上得到廣泛使用的設(shè)備。 為了降低制造成本，并利用現(xiàn)有可用的技術(shù)，標準ABS系統(tǒng)僅使用車輪速度傳感器檢測車輪轉(zhuǎn)速,這是不能夠直接獲取控制單元需要的車輪滑移率，但可以利用計算所得的車輪角速度和估計的車速間的關(guān)系來計算參考滑移率。因此，道路摩擦系數(shù),它決定了車輛在緊急剎車時的減速度, 是一個估算汽車速度的重要參數(shù)。本文分析了在不同路面情況下模擬緊急制動時車輪的加速度，并選擇一對特殊的點來確定車輪加速曲線在每個不同的操縱情況下，比如路面情況,制動扭矩和車輪的垂直載荷。它是建立在每個用試點做出的針對不同路面的曲線明顯不同于其他路面。 因此，不同的路面可以用這些點來區(qū)分，這些點反映了他們所代表的路面情況。分析假設(shè)只有車輪速度傳感器是可利用的儀器并且道路附著情況可以在緊急制動的開始初期階段確定。 關(guān)鍵字： 制動防抱死系統(tǒng)(ABS)；路面情況鑒定； 車輪角加速； 輪胎特性 介紹 對制動防抱死系統(tǒng)(ABS)來說，道路附著情況是最重要的因素之一。 標準ABS系統(tǒng)可以在制動時確定道路附著情況，并且確定道路摩擦力是高 (瀝青路面)、或低(雪、冰路面)，然后由控制單元激活相應(yīng)的邏輯控制系統(tǒng)。 只有車輪速度傳感器在標準ABS系統(tǒng)中可以確定路面情況，不需要其他需要傳感器的幫助。 道路情況鑒定是當前汽車控制研究領(lǐng)域的一個熱門主題，但研究人員通常采用額外的除車輪速度傳感器以外的可用的設(shè)備來測量汽車運動及其他國家參數(shù)來持續(xù)監(jiān)測道路狀況。但是標準ABS系統(tǒng)只需要在制動初期階段確定道路狀況，并獲得路面信息，以確定其控制單元的必需操作。 顯然，標準ABS系統(tǒng)不要求太精確的鑒定，因此只需要較少的儀器和費用。但是，這種道路情況鑒定方法并不明確。 本文正是研究在標準ABS系統(tǒng)下的道路情況鑒定方法。 分析的依據(jù)是通過測量車輪角速度所得的車輪角加速度。 因為輪胎與路面在不同路面上的磨擦特性不同，所以,，在不同道路表面上車輪制動時的反應(yīng)也不同，因此車輪制動反應(yīng)研究必須包括路面附著信息。所以我們模擬車輪制動情況，并在車輪加速曲線上選擇兩個典型數(shù)據(jù)作為標準來區(qū)分不同的路面。并討論了測量中的不確定因素的影響。 1建模 四分之一的汽車模型(表1)使用的是Dugoff輪胎模型。輪胎滑動摩擦力的最大值 (即附著系數(shù))對不同的路面是不同的，如干燥瀝青路面0.8-0.9，濕瀝青路面0.5-0.7，積雪路面約0.2%,冰面0.1。此外，當滑移率從零開始增大時，摩擦系數(shù)隨之增加的速度是不同的。特別是在冰雪路面上的摩擦系數(shù)增加速度遠低于在瀝青路面上。在路面摩擦系數(shù)達到最大前控制單元對路面情況作反映之時，這一特點是很重要的。當摩擦系數(shù)接近最大值時，控制單元開始調(diào)節(jié)制動壓力。一般而言,摩擦系數(shù)隨著滑移率增加的速度在瀝青路面上至少是在雪或冰路面上的兩倍。 為了反映此差異，在瀝青路面上的曲線的初始階段的斜率應(yīng)該為雪地路面上的兩倍。如果此差異更大，以此假設(shè)得出的結(jié)果將會更加可信。 圖一 四分之一汽車模型 一階制動模型為： dTp/dt=(Tp-Tb)/ て (1) 其中TP是施加的制動扭矩,Tb是.實際的制動扭矩，て是制動常量。 2結(jié)果和討論 四分之一汽車模型的滿載重量是400公斤。最大的制動扭矩為1000nm，在理論上可以產(chǎn)生足夠的車輛減速度為1g。 在雪地路面上(0.2)，最大的地面制動扭矩是200nm，所以若施加制動扭矩超過200nm，車輪將抱死。在濕瀝青路面上(0.5)，最大的地面制動扭矩是500nm，所以車路將在施加制動扭矩超過500nm時抱死。圖二表示的是在濕瀝青路面(0.5)和雪地路面(0.2)上不同制動扭矩下的車輪減速度曲線。在每種情況下，施加的制動扭矩都高到足以抱死車輪。在任何路面條件下，增加制動扭矩都導(dǎo)致車輪減速度快速增大，并使滑移率增大。 在雪地路面上，當制動扭矩很大時，車輪速度降低比在瀝青路面上更快。因此當?shù)缆飞嫌醒└采w時，該系統(tǒng)可以很容易判斷出。但是，當制動扭矩不是很高但足以引起車輪抱死時，車輪減速的過程就類似于在瀝青面上，控制單元就不能判斷出遇到的是何種路面。這時需要作進一步分析。 ----------------雪地路面 濕瀝青路面 圖二：在瀝青路面和雪地路面上不同制動扭矩下的車輪減速度。 在圖2上的每一條減速度曲線上都可以用兩個點來描述該曲線。第一個是減速度在0.05s時，另一個是減速度達到– 50 rad/s2時。(制動從0時開始) 我們提到的這些是加速度時間曲線確定的標準用這些點做出曲線定義為加速度時間曲線。圖三是最大地面的制動力矩為900,700,500和200時，在瀝青路面(0.9,0.7和0.5)和雪地路面(0.2)上做出的加速時間曲線 。曲線之間沒有相交表明加速度時間曲線確定的標準符合特殊的路面情況或最大的地面制動力矩。 前面的分析是假設(shè)的一輛滿載汽車。如果車輪垂直載荷變化，車輪運動情況也會有所不同,所以會產(chǎn)生不同的加速度時間曲線。 圖四中是半載的車輪在瀝青路面(0.9和0.5)和雪地路面(0.5)上做出的三條加速度時間曲線和滿載時的曲線。他們的最大地面制動力矩為450，250和100Nm。 假設(shè)一條加速度時間曲線是在車輪局部負荷即在半載和滿載之間在瀝青路面(0.9)上做出的那么它將位于制動力矩為900NM和450NM的曲線之間，那么部分負荷曲線將與制動力矩700nm和500nm的曲線相似。因此，加速度時間曲線的標準不符合的路面情況但符合最大地面制動力矩。 由此可以看出,車輪反映取決于施加的制動扭矩和道路摩擦潛力(地面制動力矩)。如果車輪負載變化并不大，如轎車,滿載的車重不等于空載車重的兩倍，這時在瀝青路面和雪地路面上的加速度時間曲線無論在任何操作情況下都將不會相交。 在這種情況下,可以用加速度時間曲線的標準來分辨出瀝青路面和雪地路面。 圖三：在四中路面情況下的車輪加速度時間曲線 t: 時間 在0.05s時 a: 加速度 在 -50rad/s2 圖四：滿載和半載情況下的車輪加速度時間曲線 t: 時間 在0.05s時 a: 加速度 在 -50rad/s2 3結(jié)論 本文分析了車輪加速度與路面情況以及車輪負荷之間的關(guān)系。 建議采用的車輪加速時間標準，可以用一個帶有控制單元的車輪速度傳感器來測出。可以反映出由路面情況和車輪負載決定的道路摩擦潛力。對轎車來說,，標準甚至可以確定路面情況，即確定車輪是與瀝青路面還是雪地路面相接觸。 共 頁 第 頁 Road Identification for Anti-Lock Brake Systems Equipped with Only Wheel Speed Sensors Abstract :Anti-lock brake systems (ABS) are now widely used on motor vehicles .To reduce cost and to use currently available technologies ,standard ABS uses only wheel speed sensors to detect wheel angular velocities ,which is not enough to directly obtain wheel slip rations needed by the control unit ,but can be used to calculate reference slip ratios with measured wheel angular velocities and the estimated vehicle speed .Therefore ,the road friction coefficient, which determines the vehicle deceleration during severe braking , is an important parameter in estimating vehicle speed .This paper analyzes wheel acceleration responses in simulations of severe braking on different road surfaces and selects a pair of specific points to identify the wheel acceleration curve for each operating condition ,such as road surface , pedal-braking torque and wheel vertical load .It was found that the curve using the selected points for each road surface clearly differs from that of the other road surface. Therefore, different road surfaces can be distinguished with these selected points which represent their corresponding road surfaces. The analysis assumes that only wheel speed sensors are available as hardware and that the road cohesion condition can be determined in the initial part of the severe braking process. Key words: anti-lock brake systems (ABS); road identification; wheel angular acceleration; tire characteristics Introduction For anti-lock brake systems(ABS),the road cohesion condition is one of the most important factors .Standard ABS can identify road cohesion conditions while braking and decide whether the road friction is high (asphalt) or low (snow , ice),so that the control unit activates the corresponding control logic . Only wheel speed sensors are available in standard ABS to identify the road conditions, with no other sensors needed. Road identification research is currently a popular topic in automotive control, but researchers usually assume extra equipment is available for measuring vehicle motion and other state parameters besides wheel speed sensors, to continuously monitor the road condition. But standard ABS only needs to identify road conditions during the initial braking period, and then obtain road information to ensure necessary operations of the control unit. Obviously, the standard ABS demands less strict identification, therefore less hardware and cost. However, the method to identify the conditions is not obvious. This paper investigates the road identification method for the standard ABS configuration. The analysis is based on the wheel angular acceleration, which is acquired from the measured wheel angular speed. Since tire-road friction characteristics differ on different road surfaces, the wheel responses while braking on different surfaces are also different, so the wheel responses must contain road cohesion information. Therefore, we simulated braking situations and then chose two typical values on the wheel acceleration curve as criteria to distinguish between different road surfaces. Influence of uncertainties in the measurements is also discussed. 1 Modeling A one quarter vehicle model (Fig.1) is used with the Dugoff tire model. The peak values of the tire slip-friction curve (i.e., cohesion coefficient) are different for different road surfaces, such as dry asphalt 0.8-0.9, wet asphalt 0.5-0.7, snow about 0.2 and ice about 0.1.Furthermore, when the slip ratio increases above zero, the friction coefficient increases at a different rate. This is especially true for the increase of the friction coefficients on snow or ice which are much lower than on asphalt. This feature is important since the control unit makes decisions about road conditions before the friction coefficient reaches a maximum .Once the friction coefficient is close to the maximum, the control unit starts to regulate the braking pressure. Generally, the friction coefficient rate of increase with the increasing slip ratio on asphalt is at least double that on snow or ice. To reflect this difference, the initial slope of the characteristic curve on asphalt was assumed to be twice that of snow. If the difference is even greater, the results using the assumption will be even more effective. Fig.1 one quarter vehicle model A first-order braking model is given by: dTp/dt=(Tp-Tb)/ て (1) where Tp is the pedal-braking torque, Tb is the actual braking torque, and てis the brake constant. 2 Results and Discussion Full load for the quarter-vehicle model is 400 kg. The maximum pedal-braking torque is 1000Nm, which is theoretically enough to produce a vehicle deceleration of 1g. On snow (0.2), the maximum ground-braking torque is 200Nm so if the pedal-braking torque is over 200Nm, the wheel will lock. On wet asphalt (0.5), the maximum ground-braking torque is 500Nm so the wheel will lock at a pedal-braking torque higher than 500Nm.Wheel acceleration curves are shown in Fig.2 for braking on wet asphalt (0.5) and snow (0.2) using different pedal-braking torques. In each case, the pedal-braking torque is high enough to lock the wheel. On either road surface, increasing the pedal-braking torque cause the wheel to decelerate more rapidly and the slip ratio to increase. On snow, when the pedal-braking torque is very, the wheel decelerate much more rapidly than on asphalt, so the system can easily judge when the road is covered with snow. However, when the pedal-braking torque is not very high but enough to cause lockup, the wheel deceleration process may resemble that on asphalt, the control unit may not be able to decide which type of road surface has been encountered. This case needs further analysis. ---------- Snow Wet asphalt Fig.2 Wheel acceleration for different pedal braking torques on wet asphalt and snow Each acceleration curve in Fig.2 can be described with two points on the curve. One is the acceleration at the time 0.05s, and the other is the time when the acceleration reaches – 50 rad/s2. (Braking starts at time 0.) We refer to these as the acceleration-time criteria and the curve defined by these points is referred to as the acceleration-time curve. Acceleration-time curves for asphalt (0.9, 0.7, and 0.5) and snow (0.2) are drawn in Fig.3 for maximum ground-braking torques of 900, 700, 500, and 200 Nm. None of the curves intersect which means the acceleration –time criteria corresponds to a particular road surface or maximum ground braking torque. The previous analysis assumed a fully-loaded vehicle. If the wheel vertical load changes, the wheel will behave differently which will result in different acceleration-time curves. Three acceleration-time curves for a half-loaded wheel on asphalt (0.9 and 0.5) and snow (0.5) are shown in Fig.4 with the full-load curves. Their maximum ground braking torque are 450, 250, and 100 Nm. Assuming that the acceleration-time curve for a wheel with a partial load between “full” and “half” on asphalt (0.9) will be located between the curves for braking torque of 900 Nm and 450Nm, then a partial load curve would be similar to the curve for braking torque of 700Nm and 500Nm. Therefore, the acceleration-time criteria do not correspond to the road surface, but to the maximum ground braking torque. It is physically reasonable that the wheel response depends on the difference between the pedal-braking torque and the road friction potential (ground-braking Torque), In cases where the wheel load does not vary greatly, such as in passenger cars, the full load of a car may not be double the load of empty car, then the acceleration-time curves for asphalt and snow will always be separated for any operating conditions. In such cases, asphalt and snow can be distinguished by the acceleration-time criterion. 3 Conclusions This paper analyzes the relationships between the wheel load. The proposed wheel acceleration-time criteria, which can be measured by a control unit with wheel speed sensors, can reflect the road friction potential resulting from the road surface and wheel load. For passenger cars, the criteria can even determine the road conditions, whether the wheel is in contact with asphalt or snow.