System for controlling the stability of a vehicle using an algorithm analyzing the variation in a representative parameter over time

• US 20050184584A1
• Filed: 01/18/2005
• Published: 08/25/2005
• Est. Priority Date: 01/16/2004
• Status: Active Grant

• Current Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Original Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Inventors: Levy, Georges, Fangeat, Nicolas
• Granted Patent: US 7,426,431 B2
• Time in Patent Office: Days
• US Class Current: 303/146
• CPC Class Codes: B60T 8/17551 determining control parameters related to vehicle stability used in the regulation, e.g. by calculations involving measured or detected parameters

Abstract

Vehicle stability control system, the system comprising means for imparting a longitudinal force on the tire and means for calculating the slip parameter G^Opt at each activation of the means for imparting a longitudinal force on the tire in the following manner: as the values of G_i are acquired, calculating the variation in G with respect to time, as long as the variation is above a low threshold, calculating coefficients A_{[wet, p]} by direct calculation or by an appropriate regression so as to model variation in G with respect to time by a variation curve which is a function of (G_i, A_{[wet, p]}), as soon as the variation is greater than a high threshold, determining a target slip G^Cwet using at least the last values of A_{[wet, p]}.

Claims

1. A vehicle stability control system in which a characteristic parameter Q of a functioning of a tire of the vehicle intended to roll on the ground varies as a function of a parameter P according to a certain law, an optimum value of the parameter P being imposed by a controller directly or indirectly, so as to act on at least one of elements chosen from a group comprising a rotation torque applied to the tire, a steering angle of the tire, a camber angle of the tire and a vertical force applied to the tire, in which the controller comprises means for:

as values of P_i are acquired, calculating a variation in P with respect to time,

as long as the variation is above a low threshold, calculating coefficients A_{[wet, p]} by direct calculation or by a regression, so as to model the variation in P with respect to time by a variation curve which is a function of (P_i, A_{[wet, p]}), and

if the variation is above a high threshold, determining a target slip P^Cwet using values of A_{[wet, p]}.

11. A vehicle stability control system according to claim 1, in which the parameter P is a drift angle δ

of the tire and the characteristic parameter Q is a drift thrust F^det of the tire, the system comprising means for controlling a parameter “

ξ

”

according to instructions entered by a driver of the vehicle on a control means and according to instructions delivered by a path controller, means of modulating the parameter “

ξ

” and

means for calculating the drift angle parameter δ

^Opt at each activation of the means for entering the parameter “

ξ

”

in the following manner;

as values of δ

_i are acquired, calculating variation in δ

with respect to time,

as long as the variation is above a low threshold, calculating coefficients A_{[wet, p]} by direct calculation or by a regression, so as to model the variation in δ

with respect to time by a variation curve which is a function of (δ

_i, A_{[wet, p]}),

if the variation is above a high threshold, determining a target slip δ

^Cwet using values of A_{[wet, p]}.

2. A vehicle stability control system, in which a parameter G is a slip of a tire and a characteristic parameter μ

is a coefficient of friction of the tire, the system comprising means for imparting a longitudinal force to the tire, means of modulating the longitudinal force and means for calculating an optimal slip parameter G_Opt at each activation of the means for imparting a longitudinal force to the tire in the following manner;

as values of G_i are acquired, calculating a variation in G with respect to time,

as long as the variation is above a low threshold, calculating coefficients A_{[wet, p]} by direct calculation or by a regression, so as to model the variation in G with respect to time by a variation curve which is a function of (G_i, A_{[wet p]}), and

if the variation is above a high threshold, determining a target slip G^Cwet using values of A_{[wet, p]}.

3. The vehicle stability control system according to claim 2, in which a linear regression is used and coefficients A_wet and B_wet are calculated in the following manner:

$\frac{d<br><br>G}{d<br><br>t}=A^{\mathrm{WET}}·<br><br>G+B^{\mathrm{WET}}$

and the target slip G^Cwet is therefore determined as follows;

$G^{\mathrm{Cwet}}=\frac{\mathrm{dG\_tgt}-B^{\mathrm{WET}}}{A^{\mathrm{WET}}}$

4. The vehicle stability control system according to claim 3, in which “

dG_tgt”

is used as a fine-tuning parameter.

5. The vehicle stability control system according to claim 2, in which the means for modulating the longitudinal force acts on a braking control and is initialized (with i=0) at a start of each braking control operation.

6. The vehicle stability control system according to claim 2, in which the means for modulating the longitudinal force acts on a driving torque at the wheels and is initialized (with i=0) at each request for a variation in the driving torque above a predetermined torque threshold.

7. The vehicle stability control system according to claim 2, in which, before obtaining the target values of the slip using a curve comprising determined values of μ

_i as a function of G_i, a correction of a start of the curve is carried out by;

eliminating from the curve at least a first real pair of values (μ

_i, G_i), as long as the variation in μ

_i as a function of G_i is not substantially constant,

seeking the slip G₀ associated with a zero coefficient of friction, such that the pair (0, G₀) and non-eliminated pairs (μ

_i, G_i) are substantially aligned, and

using a curve starting from (0, G₀) and joining the non-eliminated pairs (μ

_i, G_i), so that, for any value of G_i greater than G₀, G_i is replaced by G_i-G₀.

8. The vehicle stability control system according to claim 2, in which, when the variation in the slip with respect to time becomes greater than a predetermined variation threshold, before obtaining the target values for the slip using a curve comprising determined values of μ

_i as a function of G_i, a correction to the end of the curve is carried out, by replacing the values of μ

_i corresponding to the values of slip that result in the variation in the slip with respect to time being beyond the predetermined variation threshold, by corrected values as follows;

${\mathrm{\mu <br><br>}}_i^{\mathrm{Corr}}={\mathrm{\mu <br><br>}}_i·<br><br>{\left[\mathrm{Max}<br><br>\left(\frac{d<br><br>G}{d<br><br>t};<br><br>1\right)\right]}^{-\mathrm{ACorr}}$

where “

Acorr”

is a preset parameter.

9. The vehicle stability control system according to claim 8, in which “

Acorr”

is equal to approximately 0.2.

10. The vehicle stability control system according to claim 8, in which “

Acorr”

is used as a fine-tuning parameter.

12. A tire testing system in which a characteristic parameter Q of a functioning of a tire under test varies as a function of a parameter P according to a certain law, an optimum value of the parameter P being imposed by a controller directly or indirectly, so as to act on at least one of elements chosen from a group comprising a rotation torque applied to the tire, a steering angle of the tire, a camber angle of the tire and a vertical force applied to the tire, in which the controller comprises means for:

as values of P_i are acquired, calculating variation in P with respect to time, as long as the variation is above a low threshold, calculating coefficients A_{[wet, p]} by direct calculation or by a regression so as to model the variation in P with respect to time by a variation curve which is a function of (P_i, A_{[wet, p]}),

if the variation is above a high threshold, determining a target slip P^Cwet using values of A_{[wet, p]}.

22. The tire testing system according to claim 12, using means for imparting a drift angle to a tire under test on the ground, the means for imparting a drift angle being equipped with a system for controlling a parameter “

ξ

”

according to instructions coming from a test control means and according to instructions delivered by a controller aimed at maintaining the functioning of the tire at a predetermined value of the drift thrust F^det, the controller using at least one optimum value δ

^Opt of the drift angle corresponding to the maximum value of the drift thrust F^det, the controller comprising means for performing the following operations;

as values of δ

_i are acquired, calculating the variation in δ

with respect to time,

as long as the variation is above a low threshold, calculating coefficients A_{[wet, p]} by direct calculation or by a regression so as to model the variation in δ

with respect to time by a variation curve which is a function of (δ

_i, A_{[wet, p]}),

if the variation is above a high threshold, determining a target slip δ

^Cwet using at least the last values of A_{[wet, p]}.

13. A tire testing system, in which a parameter G is a slip of the tire and a characteristic parameter μ

is a coefficient of friction of the tire, the system comprising means for imparting a longitudinal force to the tire, means of modulating the longitudinal force and means for calculating a slip parameter G^Opt at each activation of the means for imparting a longitudinal force to the tire in the following manner;

as values of G_i are acquired, calculating variation in G with respect to time,

as long as the variation is above a low threshold, calculating coefficients A_{[wet, p]} by direct calculation or by a regression, so as to model the variation in G with respect to time by a variation curve which is a function of (G_i, A_{[wet, p]}),

if the variation is above a high threshold, determining a target slip G^Cwet using values of A_{[wet, p]}.

14. The tire testing system according to claim 13, in which a linear regression is used and coefficients A_wet and B_wet are calculated in the following manner:

$\frac{d<br><br>G}{d<br><br>t}=A^{\mathrm{WET}}·<br><br>G+B^{\mathrm{WET}}$

and the target slip G^Cwet is therefore determined as follows;

$G^{\mathrm{Cwet}}=\frac{\mathrm{dG\_tgt}-B^{\mathrm{WET}}}{A^{\mathrm{WET}}}$

15. The tire testing system according to claim 13, in which “

dG_tgt”

is used as a fine-tuning parameter.

16. The tire testing system according to claim 13, in which the means for modulating the longitudinal force acts on a braking control and is initialized (with i=0) at a start of each braking control operation.

17. The tire testing system according to claim 13, in which the means for modulating the longitudinal force acts on a driving torque at the wheels and is initialized (with i=0) at each request for a variation in the driving torque above a predetermined torque threshold.

18. The tire testing system according to claim 13, in which, before obtaining the target values for the slip using a curve comprising determined values of μ

_i as a function of G_i, a correction of the start of the curve is carried out by;

eliminating from the curve at least a first real pair of values (μ

_i, G_i), as long as the variation in μ

_i as a function of G_i is not substantially constant,

seeking the slip G₀ associated with a zero coefficient of friction, such that the pair (0, G₀) and non-eliminated pairs (μ

_i, G_i) are substantially aligned, and

using a curve starting from (0, G₀) and joining the non-eliminated pairs (μ

_i, G_i), so that, for any value of G_i greater than G₀, G_i is replaced by G_i-G₀.

19. The tire testing system according to claim 13, in which, when the variation in the slip with respect to time becomes greater than a predetermined variation threshold, before obtaining the target values for the slip using a curve comprising determined values of μ

_i as a function of G_i, a correction to the end of the curve is carried out, by replacing the values of μ

_i corresponding to the values of slip that result in the variation in the slip with respect to time beyond the predetermined variation threshold, by corrected values as follows;

${\mathrm{\mu <br><br>}}_i^{\mathrm{Corr}}={\mathrm{\mu <br><br>}}_i·<br><br>{\left[\mathrm{Max}<br><br>\left(\frac{d<br><br>G}{d<br><br>t};<br><br>1\right)\right]}^{-\mathrm{ACorr}}$

where “

Acorr”

is a preset parameter.

20. The tire testing system according to claim 19, in which “

Acorr”

is equal to approximately 0.2.

21. The tire testing system according to claim 19, in which “

Acorr”

is used as a fine-tuning parameter.