驅動方式與轉向特性 - 歐洲車

By Jacky
at 2008-08-14T01:31
at 2008-08-14T01:31
Table of Contents
在前面的文章推文之後,最好還是詳細澄清一下比較好.
在跟驅動方式相關的討論開始以前,我們先在想像中做一個實驗:
"無輪驅動"
如果有一輛四輪(汽車)裝上噴射引擎(jet;假設無向量噴嘴那種玩意兒,直接往正後方推)
然後用這輛車在平坦路面上順時針繞圈,逐漸增加繞圈的速度,
同時調整方向盤的角度(舵角)讓右後輪走在固定的半徑上.
此車將會出現:
a.轉向不足?
b.轉向過度?
c.轉向中性?
我相信寫到這裡已經有些魔人可以想通其中的意義了.
根據SAE的定義(是的,就是定義機油那個xxW-xx的SAE.敝組織很龜毛,啥都要定義):
1. A=V^2/R (向心力公式,這是物理學家搞的跟我們無關)
2. δu=αu=αf-αr (αf與αr分別為前後輪之滑差角)
3. δ=δk+δu (δ為前輪轉動角度;δk為無側向力時的角度,δu為有側向力時需增加的角度)
(中間略...抱歉有很多詳細分析跳過,但我想這樣就夠解釋了)
dδu dδ
4. Ku = _______ =(_____) (此為定義式)
dA dA R
當Ku為正值,為轉向不足
當Ku為負值,為轉向過度
當Ku為零,為轉向中性
(以上u應為大寫,為understeer之縮寫)
以下是我的註解:
1. 向心力公式我想就不多說明了.
2. 滑差角αf與αr:
當有側向力存在時,輪胎的胎壁會扭轉.
當車輛帶速度轉彎時,輪胎與地面接觸的部分會想要走慣性要它走的方向,
相較於輪框的指向,輪胎指向會偏向彎道外側--前後輪都一樣.
3. 前輪轉動角度δk與δu:
當以極慢速度繞小圈時(側向力趨近於零),要不要打方向盤(前輪指向)?
當然是要!這個值就是δk.
當速度加快以後駕駛卻被要求保持相同的半徑繞圈,
則必須打更多(或更少,或不變)的方向盤,這個差異值就是δu.它可以是正,負或零.
4. 定義式:
這個公式裡面利用dA當分母,只是用來判別方向,最後以正或負表示.
用白話來說就是方向盤"增加"的角度跟側向力的方向同向,或是反向.
重要的其實是前面的滑差角,與前輪(方向盤)轉動角度的關係.
不知道大家有沒有被騙的感覺...
這篇文章沒有討論到驅動方式跟轉向特性的關係,因為根本沒有關係.
個人心得:
最後,我必須承認任何人都有權利自己下定義,例如將後驅定義為必然轉向過度.
可是當後驅車發生任何原因的推頭時,則必須堅持這個定義-推頭也是轉向過度的現象.
這樣不是不可以,只是後續很多問題的進一步討論跟現有的汽車工程學兜不起來.
這樣做好不好?雖然說見仁見智,但是我比較喜歡融入現有的系統.
Reference:
Tires, Suspension and Handling-Second Edition, 1996
Author: John C. Dixon
Publish: Society of Automotive Engineers, Inc.
--
超跑夢 ///M Power
--
在跟驅動方式相關的討論開始以前,我們先在想像中做一個實驗:
"無輪驅動"
如果有一輛四輪(汽車)裝上噴射引擎(jet;假設無向量噴嘴那種玩意兒,直接往正後方推)
然後用這輛車在平坦路面上順時針繞圈,逐漸增加繞圈的速度,
同時調整方向盤的角度(舵角)讓右後輪走在固定的半徑上.
此車將會出現:
a.轉向不足?
b.轉向過度?
c.轉向中性?
我相信寫到這裡已經有些魔人可以想通其中的意義了.
根據SAE的定義(是的,就是定義機油那個xxW-xx的SAE.敝組織很龜毛,啥都要定義):
1. A=V^2/R (向心力公式,這是物理學家搞的跟我們無關)
2. δu=αu=αf-αr (αf與αr分別為前後輪之滑差角)
3. δ=δk+δu (δ為前輪轉動角度;δk為無側向力時的角度,δu為有側向力時需增加的角度)
(中間略...抱歉有很多詳細分析跳過,但我想這樣就夠解釋了)
dδu dδ
4. Ku = _______ =(_____) (此為定義式)
dA dA R
當Ku為正值,為轉向不足
當Ku為負值,為轉向過度
當Ku為零,為轉向中性
(以上u應為大寫,為understeer之縮寫)
以下是我的註解:
1. 向心力公式我想就不多說明了.
2. 滑差角αf與αr:
當有側向力存在時,輪胎的胎壁會扭轉.
當車輛帶速度轉彎時,輪胎與地面接觸的部分會想要走慣性要它走的方向,
相較於輪框的指向,輪胎指向會偏向彎道外側--前後輪都一樣.
3. 前輪轉動角度δk與δu:
當以極慢速度繞小圈時(側向力趨近於零),要不要打方向盤(前輪指向)?
當然是要!這個值就是δk.
當速度加快以後駕駛卻被要求保持相同的半徑繞圈,
則必須打更多(或更少,或不變)的方向盤,這個差異值就是δu.它可以是正,負或零.
4. 定義式:
這個公式裡面利用dA當分母,只是用來判別方向,最後以正或負表示.
用白話來說就是方向盤"增加"的角度跟側向力的方向同向,或是反向.
重要的其實是前面的滑差角,與前輪(方向盤)轉動角度的關係.
不知道大家有沒有被騙的感覺...
這篇文章沒有討論到驅動方式跟轉向特性的關係,因為根本沒有關係.
個人心得:
最後,我必須承認任何人都有權利自己下定義,例如將後驅定義為必然轉向過度.
可是當後驅車發生任何原因的推頭時,則必須堅持這個定義-推頭也是轉向過度的現象.
這樣不是不可以,只是後續很多問題的進一步討論跟現有的汽車工程學兜不起來.
這樣做好不好?雖然說見仁見智,但是我比較喜歡融入現有的系統.
Reference:
Tires, Suspension and Handling-Second Edition, 1996
Author: John C. Dixon
Publish: Society of Automotive Engineers, Inc.
--
超跑夢 ///M Power
--
Tags:
歐洲車
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