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1、外 文 资 料 原 文 : 河南科技大学毕业设计(论文) 1 E F F E C T ON C O RN E R IN G Vis co u s co u p l in g s a ls o p r o v id e a s el f - lo ck i n g t o r q u e w h e n co r n er in g , d u e to sp ee d d i ff e r e n c es b e tw e en t h e d r iv in g w h ee ls . D u r in g st e ad y st at e co r n e r i n g , a s

2、s h o w n i n f ig u r e 1 0 , t h e s lo w er in s id e w h e e l te n d s to b e a d d it io n a ll y d r i v en t h r o u g h t h e v is co u s c o u p lin g b y t h e o u t s id e w h ee l. F ig u r e 1 0 : Tr ac t iv e f o r ce s f o r a f r o n t - w h ee l d r i v e v e h ic le d u r in g st

3、e ad y st at e co r n er in gTh e d i f f er e n c e b et we e n th e Tr a ct i ve fo r c es D r y a n d D S L r e s u lt s i n a y aw mo men t M CO G, w h i ch h as to b e co mp e n sa t ed b y a h ig h e r lat e r a l f o r c e, an d h e n c e a lar g e r s l ip a n g le a f t at th e f r o n t a

4、x le . T hu s t h e in f lu e n c e o f a v i sc o u s c o u p lin g in a f r o n t - w h e el d r i v e v eh i c le o n s el f - s t eer in g t en d s to w ar d s a n u nd er s t ee r in g c h ar ac te r is t ic . Th is b e ha v io r is t o t a lly c o n s i st e n t wit h t h e h an d li n g b i a

5、s o f m o d e r n v e h ic le s w h ic h al l u n d e r st e er d u r in g st e ad y s t at e co r n er in g ma n e u v e r s . Ap p r o p r ia te t es t r es u lt s ar e s h o w n in f ig u r e 1 1 . F ig u r e 1 1 : co mp a r i so n b e t we en v e h ic le s f it t ed w it h a n o p e n d i ff e r

6、 e n t ia l a n d v is co u s co u p l in g d u r i n g s t ea d y s t at e co r n er in g . Th e as y m met r i c d i st r i b u t io n o f t h e t r ac t iv e f o r ce s d u r in g c o r n e r in g as s h o w n in f ig u r e 1 0 i mp r o ve s a ls o t h e s t r a ig h t - li n e r u n n i n g . E

7、v er y d e v ia t io n f r o m t h e s t r a ig ht - lin e p o s it io n ca u s es t h e w h ee ls to r o ll o n s lig h t ly d if f e r e n t r ad ii. Th e d i f f er en c e b et w ee n t he d r iv i n g f o r ce s an d t h e r e su lt in g ya w mo me nt t r ie s t o r e st o r e t he v e h ic le t

8、o s t r a ig h t - l in e r u n n i n g ag a in ( s ee f i g u r e 1 0 ) . Al t h o u g h t h es e d ir e ct io n al d e v i at io n s r es u lt in o n ly s ma ll d i ff e r e n ce s in w h ee l t r a v el r a d i i, t h e r o t a tio n a l d if f e r e n ce s es p ec ia l ly at h ig h sp ee d s a r

9、 e lar g e en o u g h f o r a v is c o u s co u p li n g f r o n t d if f er e n t ia l to b r i n g i mp r o v e me n ts in s t r a ig h t - l in e r u n n in g . H ig h p o we r e d f r o n t - w h ee l d r iv e v e h ic le s f it te d w it h o p e n d i ff e r e n t ia ls o f te n s p in t h e ir

10、 i n s id e w h ee ls w h e n acc e ler at in g o u t o f t ig h t c o r n e r s in lo w g ea r. I n v eh i cl es f i tt ed w ith l im it ed - s li p v is co u s 22河南科技大学毕业设计(论文) d i ff e r e n t ia ls , t h i s s p i n n i n g is li mit e d a n d th e t o r q u e g e n er a t ed b y t h e s p ee d

11、d if f e r e n ce b e tw e en t h e w h e el s p r o v id e s a d d it io n a l t r a ct iv e ef f o r t f o r t h e o u t s id e d r iv i n g w h e e l. T h is is s h o w n in f ig u r e 1 2 F ig u r e 1 2 : t r ac t iv e f o r c es fo r a f r o n t - w h e el d r iv e v eh ic le w it h v is c o u

12、s lim it ed - s lip d i f f er en t ia l d u r i n g a cc e ler a t io n in a b e n dTh e a cc ele r a t io n cap ac it y is t h u s imp r o v e d , p ar t ic u l ar ly w h e n tu r n in g o r a cc el er a t in g o u t o f a T- ju n c t io n m an e u v e r ( i. e. ac ce le r at i ng f r o m a st o p

13、 p ed p o s it io n at a “T ” in t er s ec t io n - r ig h t o r le f t t u r n ) . F ig u r es 1 3 an d 1 4 s h o w s th e r es u l ts o f a cc e ler at io n t es t s d u r i n g st e ad y s t at e c o r n e r i n g w it h a n o p en d i ff e r e n t ia l a n d w it h v is co u s li mit e d - s l i

14、p d if f e r e n t ial . F ig u r e 1 3 : a cc el er a t io n c h ar ac te r i st ic s f o r a f r o n t- w he e l d r iv e v e h ic le w it h an o p en d if f e r e n t ia l o n w e t as p ha lt at a r a d iu s o f 4 0 m ( f i x ed st e er in g wh e e l a n g l e t h r o u g h o u t t es t ) . F ig

15、 u r e 1 4 : A cc e ler at io n Ch ar ac te r i st ic s f o r a F r o n t - W h ee l Dr iv e Ve h i cl e w it h Vi s co u s Co u p l in g o n Wet A s p h a lt at a Ra d iu s o f 4 0 m ( F ix e d s t ee r i n g w h e el a n g le t h r o u g h o u t te st ) Th e v eh i cl e w it h a n o p en d if f er

16、 en t i al a ch ie v es an a v er ag e ac ce le r at io n o f 2 . 0 m / s w h i le t h e Ve h ic le w ith t h e v i sc o u s co u p l in g r e ac h es an a v er a g e o f 2 . 3 m / s ( li mit e d b y en g in e - p o w e r ) . I n t h e se t e st s , th e ma x i mu m sp eed d i ff e r e n ce , c au s

17、 e d b y s p in n in g o f th e in s id e d r iv e n w h ee l w a s r ed u ce d f r o m 2 4 0 r p m w it h o p e n d if f e r e n t ia l to 10 0 r p m w it h t h e v is co u s co u p l in g . D u r in g ac ce le r at io n i n a b e n d , f r o n t - w h e el d r i v e ve h i cl es i n g e n er a l t

18、 en d t o u n d er s t ee r mo r e t h an w h e n r u n n in g at a st e ad y s p e ed . T he r e as o n f o r t h i s is th e r e d u ct io n o f th e p o t en t ia l t o tr an s m it lat e r a l f o r c es at t h e f r o n t - t ir e s d u e t o w ei g h t t r an s f e r t o t h e r e ar w h ee ls

19、 an d in c r e as ed lo n g it u d in a l f o r c es a t t h e d r iv i n g w he e ls . I n a n o p en lo o p co n tr o l- c ir c l e- t es t t h i s c an b e s ee n in t h e d r o p o f t h e ya w in g s p e ed ( ya w r at e) a f t er st ar t i n g t o ac ce le r at e ( T ime 0 i n F ig u r e 1 3 a

20、n d 1 4 ) . I t ca n a lso b e t a k en f r o m F i g u r e 1 3 a n d F ig u r e 1 4 t h at t h e y a w r at e o f t h e v e h ic le w it h t h e o p en d if f er en t ia l f a lls - o f f mo r e r ap i d ly t h a n f o r t h e 河南科技大学毕业设计(论文) v e h ic le w it h t h e v is co u s co u p l in g st ar

21、t in g t o a cc el er a t e. Ap p r o x ima t el y 2 s ec o n d s a f t er st a r t in g t o a cc el er a t e, h o w ev e r, th e y a w r at e f al l- o f f g r a d ie n t o f t h e v is c o u s- co u p led v e h ic l e in c r e as e s mo r e t h an at t h e v e h ic le w it h o p en d if f e r e n

22、t ial . Th e v e h ic le w it h t h e li mit e d s l ip fr o n t d if f e r e n t ia l t h u s h a s a mo r e st a b le in it i al r ea ct io n u n d er a cc el er a t in g d u r in g c o r n e r i n g th a n th e v e h ic le w it h th e o p en d if f er en t i al, r e d u c in g it s u n d er s t e

23、e r. T h i s is d u e to th e h ig h e r s li p at t h e in s id e d r iv in g w h ee l c au s in g a n i n cr ea se i n d r i v in g f o r ce t h r o u g h t h e v i s co u s co u p l in g to t h e o u t s id e w h e e l, w h ic h is i llu st r at e d in F i g u r e 1 2 . Th e im b al a n ce in t h

24、 e f r o n t w h ee l a tt r a ct iv e f o r c es r e su lt s i n a y aw mo me n t M CSD a ct in g in d ir e ct io n o f t h e t u r n , co u n t er in g t h e u n d er s t ee r. Wh e n t h e ad h es io n lim it s o f th e d r iv i n g wh e e ls a r e ex c ee d , t h e v e h ic le w it h t h e v i s

25、c o u s co u p lin g u n d e r st e er s mo r e n o t ice a b ly t h a n t h e v e h ic le w it h t h e o p e n d if f er e n t ia l ( h e r e , 2 s eco n d s a ft e r st a r ti n g to ac ce le r at e ) . O n v er y l o w f r i ct io n s u r fa c es , s u c h as s n o w o r ic e, s tr o n g e r u n

26、d e r s t ee r is t o b e e x p e ct ed w h e n a cc e ler a t in g in a cu r v e w it h a li mit e d s li p d i f f er en t ia l b ec au se th e d r iv i n g w h e el s- co n n ec t ed t h r o u g h t h e v is co u s co u p lin g - ca n b e ma d e t o sp in mo r e ea s il y ( p o we r - u n d e r -

27、 s t eer in g ) . T h i s ch ar a ct er is t ic ca n , h o w e v er , b e ea s il y co n tr o lle d b y th e d r iv e r o r b y a n au t o m at ic th r o tt le mo d u la t in g t r a ct io n co n tr o l s y st e m. U n d e r t h e se co n d it io n s a mu c h e as i er t o co n t r o l t h a n a r e

28、 ar - w h ee l d r i v e ca r. Wh i ch c a n ex h ib it p o w er - o v er st ee r i n g w h e n ac ce le r at i n g d u r in g co r n er in g ? Al l t h in g s , co n s id e r e d , t h e a d v a n t ag e t hr o u g h t h e s ta b i liz ed ac ce le r a t io n b e h a v io r o f a v i s co u s co u p

29、 li n g eq u ip p e d v e h i cl e d u r in g a cc e ler at io n th e s ma ll d is a d v a n t ag e o n s li p p er y s u r fa ce s . Th r o tt le - o f f r ea ct i o n s d u r i n g co r ne r i n g , ca u s ed b y r e le as i n g th e ac ce le r at o r s u d d e n ly, u s u a l ly r es u lt i n a f

30、 r o n t - w h e el d r iv e v e h ic le tu r n in g in t o t h e t ur n ( t h r o t t le- o f f o v e r s t ee r in g ) . H ig h - p o we r e d mo d el es s s w h i ch ca n r e ac h h ig h lat er al a c ce ler at io n s s h o w t h e h e av ie st r e act io n s . Th is t h r o tt le - o ff r eac t

31、io n h a s s ev er al ca u s es s u c h as k i n em at ic s in f l u e n ce , o r as t h e v e h i cl e at t emp t in g to t r a v e l o n a s ma l ler 河南科技大学毕业设计(论文) co r n er in g r ad iu s w it h r e d u c in g sp ee d . T h e e s se n t ia l r e a so n , h o we v er , is t h e d yn am ic w ei g

32、h t t r an s f e r f r o m t h e r ea r to t h e f r o n t ax l e, wh ic h r e su lt s in r e d u ce d s lip - a n g le s o n t h e f r o n t a n d in c r ea s ed s li p - a n g le s o n t h e r ea r wh e e ls . Bec au s e th e r ea r wh e e ls ar e n o t tr an s m itt i n g d r i v in g to r q u e

33、, t he i n f lu en c e o n t h e r e ar ax le in t h is c as e is g r ea te r t h a n t h a t o f t h e f r o n t ax l e. T h e d r iv in g f o r c es o n th e f r o n t w h ee ls b ef o r e t h r o t t le- o f f ( s ee F i g u r e 1 0 ) b ec o me o v er r u n n in g o r b r a k in g f o r ce s a ft

34、 e r w ar d s , w h ic h i s il lu s t r a te d f o r t h e v is co u s eq u ip p ed v eh i c le in F i g u r e 1 5 . F ig u r e 1 5 : Ba r k in g F o r c es f o r a F r o n t - W h ee l D r i v e Ve h ic le w it h Vis c o u s L im it ed - S lip D if f e r e nt ial I m me d ia te ly af t er a T h r

35、o t t le- o f f M an e u v e r W h il e Co r n er in g As th e in n e r w h ee l co nt in u ed t o t u r n m o r e s lo w ly t h a n t h e o u t e r w h ee l, t h e v is co u s co u p l in g p r o v id e s th e o u t er wh e e l w it h th e la r g e r b r a k in g f o r c e B f . T h e f o r c e d i

36、 f f er e n c e b e t we en t h e f r o n t - w h e el s a p p lie d ar o u n d th e c e nt e r o f g r av it y o f t h e v eh ic le c au s e s a y a w mo me n t M C 0Gt h at co u n te r a ct s th e n o r ma l t u r n - in r ea ct io n . Wh e n co r n er in g b e h a v io r d u r in g a t h r o t t

37、le- o f f ma n eu v er is co mp a r ed f o r v e h ic le s w it h o p e n d i ff er e n t ia ls a n d v is c o u s co u p l in g s, as s h o w n in F ig u r e 1 6 a n d 1 7 , th e s p ee d d i ff e r e n ce b et w ee n t h e t wo d r i v in g w h ee ls is r e d u c ed w it h a v is c o u s d if f er

38、 en t ia l. F ig u r e 1 6 : T h r o t t le- o f f Ch a r a ct er ist i cs f o r a Fr o n t- Wh e el Dr iv e Ve h ic l e w it h a n o p en D if f e r e nt i al o n Wet A s p h a lt at a Rad iu s o f 4 0 m ( O p e n Lo o p ) F ig u r e 1 7 : T h r o t t le- o f f Ch a r a ct er ist i cs f o r a Fr o

39、n t- Wh e el Dr iv e Ve h ic l e w it h Vi s co u s Co u p l in g o n Wet A s p h a lt at a Ra d iu s o f 4 0 m ( O p e n Lo o p ) Th e y aw i n g s p e e d ( ya w r at e ) , a n d t h e r e lat iv e y a w in g an g le ( i n ad d it io n t o t h e y a w an g le w h ic h th e v e h ic le wo u ld h a

40、v e ma in t a in e d i n ca s e o f c o n t in u e d s t ea d y st at e co r n er in g ) s h o w a p r o n o u nc ed i n cr e as e a ft er t hr o tt le - o ff ( Tim e =0 s ec o n d s in F i g u r e 1 4 a n d 1 5 ) w it h t h e o p e n d i ff e r e n t ia l. Bo t h t h e s u d d en i n cr eas e o f t

41、h e ya w r at e a ft er t h r o t t le- o f f an d a ls o t h e i n cr ea se o f t h e r e la t iv e y a w an g le a r e s i g n i f ic an t l y r ed u ce d in t h e v e h ic le e q u ip p ed w it h a v is c o u s li mit ed - s li p d if f er en t ia l. 河南科技大学毕业设计(论文) A n o r mal d r i v er a s a f

42、r o n t- wh e e l d r iv e v e h ic le is u s u a ll y o n l y ac cu st o med t o n eu t r a l a n d u n d e r s te er in g v e h ic le h a n d in g b e h a v io r , t h e d r i v er can t h e n b e s u r p r is ed b y su d d e n an d f o r ce f u l o v er s t ee r in g r e act io n a f t er an ab r

43、 u p t r e lea s e o f t h e t h r o t tle , f o r ex a mp l e in a b e nd w it h d e cr eas i n g r ad iu s . Th is v e h ic le r e ac t io n is fu r t h er w o r s e n ed if t h e d r i v er o v er - c o r r e ct s fo r th e s it u at io n . Ac c id e n ts w h er e ca r s lea v e t h e r o a d t o

44、 t h e in n er s id e o f th e cu r v e is p r o o f o f t h is o ccu r r en c e. He n c e th e v is c o u s co u p li n g i mp r o v es th e t h r o t t le - o ff b e h a v io r w h i le r em ai n in g co nt r o lla b l e, p r e d ic t ab l e, an d sa f e r f o r a n a ve r a g e d r i v er . 2. E

45、F F E C T ON B R A KI NGTh e v i sc o u s c o u p lin g in a f r o n t- w h ee l d r iv e v e h ic le w it h o u t A BS ( a n ti- lo ck b r a k i n g s y s te m) h a s o n ly a v er y s ma ll i n f l u en c e o n t h e b r a k in g b e h a v io r o n s p l it - s u r f ac es . He n ce t h e fr o n t

46、 - w h ee l s a r e co n n ec te d p ar t ia l ly v ia t h e f r o nt - w h e el o n t h e lo w - s id e is s l ig h t ly h ig h er t h a n i n an v eh i c le w ith an o p en d if f e r e nt i al . O n t h e o t h e r s id e , th e b r a k e p r e s su r e t o lo ck t h e f r o n t- wh e e l o n th

47、e h ig h - s id e is s li g h t ly lo we r. T h e se d if f e r e n ce s c an b e m ea su r ed in an in s t r u men t e d te st v eh ic le b u t a r e h ar d l y n o t ic ea b l e in a s u b j ec ti v e as s e ss m en t . Th e lo c k i n g s eq u en c e o f f r o nt a n d r e ar a x le i s n o t in

48、f l u e n ce d b y t h e v is co u s co u p l in g . Mo st AB S o f f er e d to d a y h as in d i v id u al co n tr o l o f e ac h f r o n t w h e el . E lec tr o n ic A BS in fr o n t - w h ee l d r iv e v e h ic le s mu s t al lo w f o r t h e co n s id e r a b le d if f e r e nc es in e f f ec t

49、iv e w h e el in e r t ia b e tw e en b r a k in g w it h t h e c lu t c h e n g ag ed an d d i se n g a g ed . P ar t ia l co u p li n g o f t h e f r o n t w h ee ls t h r o u g h t h e v i s co u s u n it d o e s n o t t h e r e fo r e co mp r o mis e t h e a ct io n o f th e A BS - a f ac t t h at h a s b ee n co n f ir med b y n u m er o u s t es t s an d b y se v e r a l i n d e p e n d en t ca r ma n u f a ct u r e r s . Th e o n e t h e o r e ti ca l e x ce p t io n to t h i s o cc u r s o n a s p l it - s u r f a ce i f a ya

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