Automatic stability control system for a vehicle using an invariant characterizing any tire

• US 6,971,726 B2
• Filed: 06/13/2003
• Issued: 12/06/2005
• Est. Priority Date: 06/13/2002
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Inventors: Levy, Georges, Fangeat, Nicolas
• Primary Examiner(s): Butler, Douglas C.
• Application Number:
  US10/461,628
• Publication Number:
  US 20040032165A1
• Time in Patent Office: 907 Days
• Field of Search: 303/20, 303/199, 303/150, 303148-149, 303163-165, 303/191, 303/146, 303/122.03, 731/46, 73/9, 701/80, 701/72, 701/79, 701/90, 701/82, 701/71, 701/83, 701/86, 180/197, 702/105, 702/42, 700/80, 700/32, 700/73, 700/57, 188/181.A
• US Class Current: 303/150
• CPC Class Codes: B60T 8/172 Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• CPC Class Codes: B60T 8/17552 responsive to the tire sideslip angle or the vehicle body slip angle

Abstract

A system is presented for controlling the stability of a vehicle. The system includes a controller using a slip parameter G_OPT corresponding to a predetermined value of the coefficient of friction μ or a controller maintaining the functioning of the tire at an optimal value δ^OPT of the drift angle corresponding to the maximum value of the draft thrust F_target. The controller performs the following operations (where X is either the slip G or the drift angle δ, and Y is either μ or F). Estimations or measurements are determined for at least one pair of values (X_i, Y_i). The corresponding values of the slope α_i are determined for the straight line passing through the origin (X_i, Y_i). Coefficients A_p are calculated by direct calculation or by a regression from a sufficient number of pairs with (α_i, X_i) so as to model a variation curve α_i=f(X_i, A_p). A target value X^Target is calculated by using a predetermined invariant “Invt”.

Claims

1. A system for controlling the stability of a vehicle having wheels, including means for imparting a longitudinal force to a tire intended to roll on the ground, means for modulating the longitudinal force, and comprising a controller using at least a slip parameter G^Opt corresponding to a predetermined value of a coefficient of friction μ

, the system including means for performing the following operations;

(a) on each activation of the means for imparting a longitudinal force to the tire, for at least two different levels “

i”

of the longitudinal force each corresponding to one slip G_i, on condition that there is no loss of grip, determining values of the coefficient of friction μ

_i;

(b) determining a slope α

_i of a straight line passing through the origin and through (CT_i, μ

_i);

(c) calculating coefficients A_p by direct calculation or by a regression from a selected number of pairs with (α

_i, G_i) so as to model a variation curve α

_i=f(G_i, A_p);

(d) calculating the optimum slip G^Opt by using a predetermined Invariant “

Invt”

; and

(e) acting on the means for imparting a longitudinal force to the tire so as to maintain the slip at optimum value G^Opt.

2. A system for controlling the stability of a vehicle according to claim 1, in which the Invariant is determined as follows:

$\mathrm{Invt}=\frac{\frac{\mathrm{\mu <br><br>}}{G}<br><br>\left(G_{\max }\right)}{\frac{\mathrm{\mu <br><br>}}{G}<br><br>\left(p·<br><br>G_{\max }\right)},$

with p having a positive value less than 1.

3. A system for controlling the stability of a vehicle according to claim 1, in which the means for modulating the longitudinal force acts on a brake control.

4. A system for controlling the stability of a vehicle according to claim 1, in which the means for modulating the longitudinal force acts on a driving torque at the wheels.

9. A system for controlling the stability of a vehicle according to claim 1 or 5, in which two particular coefficients A_p, the coefficients A and B, are calculated by a regression chosen from the group consisting of a linear regression and an exponential regression.

10. A system for controlling the stability of a vehicle according to claim 2 or 6, in which the value of p is between 0.25 and 0.75.

11. A system for controlling the stability of a vehicle according to claim 10, in which p is 0.5.

13. A system for controlling the stability of a vehicle according to any one of claims 1, 5 and 12, in which the means for performing operation (d) includes means for using the Invariant “

Invt”

as an adjustment variable.

14. A system for controlling the stability of a vehicle according to claim 2, in which the value of “

Invt”

is about 0.58.

15. A system for controlling the stability of a vehicle according to claim 1, in which the slope α

_i is determined by direct calculation according to;

α

_i=μ

_i/G_i.

16. A system for controlling the stability of a vehicle according to claim 1, in which the slope α

_i is determined by carrying out a regression.

17. A system for controlling the stability of a vehicle according to claim 1, in which a linear regression is carried out according to:

$\underset{\mathrm{GG}}{\sum <br><br>}<br><br>=\sum <br><br>G_j^2,\underset{G<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\mu <br><br>}}{\sum <br><br>}<br><br>=\sum <br><br>G_j·<br><br>{\mathrm{\mu <br><br>}}_j,{\mathrm{\alpha <br><br>}}_i=\frac{\underset{G<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\mu <br><br>}}{\sum <br><br>}}{\underset{\mathrm{GG}}{\sum <br><br>}}.$

18. A system for controlling the stability of a vehicle according to claim 1, in which the two particular coefficients A_p, the coefficients A and B, are calculated by the following linear regression, applied to “

n”

measured or estimated points;

$A^{\mathrm{Lin}}=\frac{n·<br><br>\sum <br><br>G·<br><br>\mathrm{\alpha <br><br>}-\sum <br><br>G·<br><br>\sum <br><br>\mathrm{\alpha <br><br>}}{n·<br><br>\sum <br><br>G^2-{\left(\sum <br><br>G\right)}^2},<br><br>B^{\mathrm{Lin}}=\frac{\sum <br><br>\mathrm{\alpha <br><br>}·<br><br>\sum <br><br>G^2-\sum <br><br>G·<br><br>\mathrm{\alpha <br><br>}·<br><br>\sum <br><br>G}{n·<br><br>\sum <br><br>G^2-{\left(\sum <br><br>G\right)}^2}.$

19. A system for controlling the stability of a vehicle according to claim 18, in which G^Opt is calculated as follows:

$G^{\mathrm{Opt}}=\frac{B^{\mathrm{Lin}}}{A^{\mathrm{Lin}}}·<br><br>\frac{1-\mathrm{Invt}}{1-p·<br><br>\mathrm{Invt}},$

with α

=A^Lin·

G+B^Lin.

20. A system for controlling the stability of a vehicle according to claim 19, in which in addition the value of μ

corresponding to G^Opt is determined as follows;

μ

=μ

<sup>coeff—

lin</sup>·

G^Opt·

(A^Lin·

G^Opt+B^Lin).

21. A system for controlling the stability of a vehicle according to claim 1, in which the two particular coefficients A_p, the coefficients A and B, are calculated by the following exponential regression, applied to “

n”

measured or estimated points;

$A^{\mathrm{Exp}}=\frac{n·<br><br>\sum <br><br>G·<br><br>L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{\alpha <br><br>}\right)-\sum <br><br>G·<br><br>\sum <br><br>L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{\alpha <br><br>}\right)}{n·<br><br>\sum <br><br>G^2-{\left(\sum <br><br>G\right)}^2},<br><br>B^{\mathrm{Exp}}=\frac{\sum <br><br>L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{\alpha <br><br>}\right)·<br><br>\sum <br><br>G^2-\sum <br><br>G·<br><br>L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{\alpha <br><br>}\right)·<br><br>\sum <br><br>G}{n·<br><br>\sum <br><br>G^2-{\left(\sum <br><br>G\right)}^2}.$

22. A system for controlling the stability of a vehicle according to claim 21, in which G^Opt is calculated as follows:

$G^{\mathrm{Opt}}=\frac{L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{Invt}\right)}{p·<br><br>A^{\mathrm{Exp}}},\mathrm{with}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}={\mathrm{e<br><br>}}^{A^{\mathrm{Exp}}·<br><br>G+B^{\mathrm{Exp}}}.$

23. A system for controlling the stability of a vehicle according to claim 22, in which μ

_max is determined as follows;

μ

_max=μ

<sup>coeff—

exp</sup>·

G^Opt·

e/<sup>Aexp·

GOpt+BExp</sup>.

5. A system for controlling the stability of a vehicle having wheels and at least one tire intended to roll on the ground, the vehicle being equipped with a system for controlling a selected parameter λ

depending on commands imparted by a vehicle driver to a control means and depending on commands delivered by a path controller aimed at maintaining functioning of the tire at a predetermined target value of drift thrust F_target, the path controller using at least one optimum value δ

^Opt of drift angle corresponding to a maximum value of the drift thrust F_target, the system for controlling the stability of a vehicle including means for performing the following operations;

(a) on each activation of the system controlling said parameter λ

for at least two different levels “

i”

of drift angle δ

, recording various values of F_Yi, and the estimated or measured drift angle δ

_i;

(b) determining a slope α

_i of a straight line passing through an origin and through (δ

_i, F_Yi);

(c) calculating coefficients A_p by direct calculation or by a regression from a selected number of pairs with (α

_i, δ

_i) so as to model a variation curve α

_i=f(δ

_i, A_p);

(d) calculating the optimum drift angle value δ

^Opt associated with the maximum value of the drift thrust F_target by using a predetermined Invariant “

Invt”

; and

(e) producing a warning signal when the drift angle δ

is close to δ

^Opt.

6. A system for controlling the stability of a vehicle according to claim 5, in which the Invariant is determined as follows:

$\mathrm{Invt}=\frac{\frac{F}{\mathrm{\delta <br><br>}}<br><br>\left({\mathrm{\delta <br><br>}}^{\mathrm{Opt}}\right)}{\frac{F}{\mathrm{\delta <br><br>}}<br><br>\left(p·<br><br>{\mathrm{\delta <br><br>}}^{\mathrm{Opt}}\right)},$

with p having a positive value less than 1.

7. A system for controlling the stability of a vehicle according to claim 5, in which the parameter λ

relates to steering of the wheels and, in the event of the occurrence of the warning signal, the system for controlling the parameter λ

is acted upon so as to maintain the drift angle δ

at the optimum value δ

^Opt.

8. A system for controlling the stability of a vehicle according to claim 5, in which, in the event of the occurrence of the warning signal, a speed of the vehicle is limited or reduced.

24. A system for controlling the stability of a vehicle according to claim 5, in which the slope α

_i is determined by direct calculation according to;

α

_i=F_i/δ

_i.

25. A system for controlling the stability of a vehicle according to claim 5, in which the slope α

_i is determined by carrying out a regression.

26. A system for controlling the stability of a vehicle according to claim 5, in which a linear regression is carried out according to:

$\underset{\mathrm{\delta <br><br>\delta <br><br>}}{\sum <br><br>}<br><br>=\sum <br><br>{\mathrm{\delta <br><br>}}_j^2,\underset{\mathrm{\delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>F}{\sum <br><br>}<br><br>=\sum <br><br>{\mathrm{\delta <br><br>}}_j·<br><br>F_j,{\mathrm{\alpha <br><br>}}_i=\frac{\underset{\mathrm{\delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>F}{\sum <br><br>}}{\underset{\mathrm{\delta <br><br>\delta <br><br>}}{\sum <br><br>}}.$

27. A system for controlling the stability of a vehicle according to claim 5, in which the two particular coefficients A_p, the coefficients A and B, are calculated by the following linear regression, applied to “

n”

measured or estimated points;

$A^{\mathrm{Lin}}=\frac{n·<br><br>\sum <br><br>\mathrm{\delta <br><br>}·<br><br>\mathrm{\alpha <br><br>}-\sum <br><br>\mathrm{\delta <br><br>}·<br><br>\sum <br><br>\mathrm{\alpha <br><br>}}{n·<br><br>\sum <br><br>{\mathrm{\delta <br><br>}}^2-{\left(\sum <br><br>\mathrm{\delta <br><br>}\right)}^2},<br><br>B^{\mathrm{Lin}}=\frac{\sum <br><br>\mathrm{\alpha <br><br>}·<br><br>\sum <br><br>{\mathrm{\delta <br><br>}}^2-\sum <br><br>G·<br><br>\mathrm{\alpha <br><br>}·<br><br>\sum <br><br>\mathrm{\delta <br><br>}}{n·<br><br>\sum <br><br>{\mathrm{\delta <br><br>}}^2-{\left(\sum <br><br>\mathrm{\delta <br><br>}\right)}^2}.$

28. A system for controlling the stability of a vehicle according to claim 27, in which δ

^Opt is calculated as follows;

${\mathrm{\delta <br><br>}}^{\mathrm{Opt}}=\frac{B^{\mathrm{Lin}}}{A^{\mathrm{Lin}}}·<br><br>\frac{1-\mathrm{Invt}}{1-p·<br><br>\mathrm{Invt}},$

with α

=A^Lin·

δ

+B^Lin.

29. A system for controlling the stability of a vehicle according to claim 28, in which in addition F^Target is determined as follows:

F^Target=F^coeffLin·

δ

^Opt·

(A^Lin·

δ

^Opt+B^Lin).

30. A system for controlling the stability of a vehicle according to claim 5, in which the two particular coefficients A_p, the coefficients A and B, are calculated by the following exponential regression:

$A^{\mathrm{Exp}}=\frac{n·<br><br>\sum <br><br>\mathrm{\delta <br><br>}·<br><br>L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{\alpha <br><br>}\right)-\sum <br><br>\mathrm{\delta <br><br>}·<br><br>\sum <br><br>L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{\alpha <br><br>}\right)}{n·<br><br>\sum <br><br>{\mathrm{\delta <br><br>}}^2-{\left(\sum <br><br>\mathrm{\delta <br><br>}\right)}^2},<br><br>B^{\mathrm{Exp}}=\frac{\sum <br><br>L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{\alpha <br><br>}\right)·<br><br>\sum <br><br>{\mathrm{\delta <br><br>}}^2-\sum <br><br>\mathrm{\delta <br><br>}·<br><br>L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{\alpha <br><br>}\right)·<br><br>\sum <br><br>\mathrm{\delta <br><br>}}{n·<br><br>\sum <br><br>{\mathrm{\delta <br><br>}}^2-{\left(\sum <br><br>\mathrm{\delta <br><br>}\right)}^2}.$

31. A system for controlling the stability of a vehicle according to claim 30, in which δ

^Opt is calculated as follows;

${\mathrm{\delta <br><br>}}^{\mathrm{Opt}}=\frac{L<br><br>\text{\hspace{1em}<br><br>}<br><br>n<br><br>\left(\mathrm{Invt}\right)}{p·<br><br>A^{\mathrm{Exp}}},\mathrm{with}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}={\mathrm{e<br><br>}}^{A^{\mathrm{Exp}}·<br><br>\mathrm{\delta <br><br>}+B^{\mathrm{Exp}}}.$

32. A system for controlling the stability of a vehicle according to claim 30, in which in addition F^Target is determined as follows:

F^Target=F<sup>coeff—

exp·

δ

Opt</sup>·

e<sup>aexp·

δ

Opt</sup>+A^target.

12. A system for controlling the stability of a vehicle having wheels and at least one tire intended to roll on the ground and capable of functioning when subject to drift, including means for predicting a value of a drift angle δ

of the tire where a lateral force is maximal, the means for predicting comprising means for performing the following operations;

(a) determining estimations (δ

i, F_i) for at least one pair “

i”

of values;

(b) determining the corresponding values of a slope α

_i of a straight line passing through an origin and through (δ

_i, F_i);

(c) calculating coefficients A_p by direct calculation or by a regression from a selected number of pairs with (α

_i, δ

_i) so as to model a variation curve α

_i=f(δ

_i, A_p);

(d) calculating a value of drift angle δ

^Opt by using a predetermined Invariant “

Invt”

;

(e) producing a warning signal when the drift angle δ

is close to δ

^Opt; and

(f) in the event of the occurrence of the warning signal, limiting or reducing automatically the vehicle speed.