System for Estimating the Maximum Adherence Coefficient by Measuring Stresses in a Tire Tread

• US 20080294352A1
• Filed: 06/27/2005
• Published: 11/27/2008
• Est. Priority Date: 06/30/2004
• 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: Spetler, Frederic
• Granted Patent: US 7,827,858 B2
• Time in Patent Office: Days
• US Class Current: 702/33
• CPC Class Codes: G01M 17/02 Tyres

Abstract

A system for estimating the maximal grip coefficient μ in the contact area of a tire on a road. A tire tread is fitted with at least one tread sensor for measuring at least the tangential stresses which the tread experiences locally when the tire rolls on the ground. a signal processing unit and means for transmitting to the processing unit at least one signal delivered by the tread sensor are provided. The processing unit comprises means for finding in the signal the values corresponding to the sensor passing through the contact area of the tire on the ground, means for calculating an instantaneous value of a preselected criterion as a function of a series of values chosen from those relating to the sensor passing through the contact area, and means for extracting an estimate of the maximal grip coefficient μ by using the said instantaneous value.

Claims

1. A system for estimating the maximal grip coefficient t in the contact area of a tire on a road, comprising:

at least one tread sensor adapted to be fitted in a tire tread for measuring at least the tangential stresses which the tread experiences locally when the tire rolls on the ground;

a signal processing unit; and

means for transmitting to the signal processing unit at least one signal delivered by said tread sensor,

wherein the processing unit comprises

means for finding in the signal the values corresponding to the sensor passing through the contact area of the tire on the ground,

means for calculating an instantaneous value of a preselected criterion as a function of a series of values chosen from those relating to the sensor passing through the contact area, and

means for extracting an estimate of the maximal grip coefficient μ

by using the instantaneous value.

2. The system according to claim 1, wherein said means for extracting an estimate of the maximal grip coefficient μ

comprise means for selecting a predetermined characteristic curve of the change in the maximal grip coefficient μ

as a function of the values of the preselected criterion and identification on this characteristic curve of an estimate of the maximal grip coefficient μ

on the basis of the instantaneous value.

3. The system according to claim 1, wherein said means for extracting an estimate of the maximal grip coefficient μ

comprise means for calculating an estimate of the maximal grip coefficient μ

on the basis of the said instantaneous value and mathematical equations whose parameters have been fitted.

4. The system according to claim 1, wherein the preselected criterion is a standard deviation of the values σ

(x) of the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

5. The system according to claim 1, wherein the preselected criterion is a sum of the squares of the values σ

(x) of the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

6. The system according to claim 1, wherein the preselected criterion is a maximal value of the values σ

(x) of the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

7. The system according to claim 1, wherein the preselected criterion is a minimum value of the values σ

(x) of the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

8. The system according to claim 1, wherein the preselected criterion is a value of the weight <

<

a>

>

of an n^th order polynomial σ

(x)=a·

xⁿ+b·

x<sup>n−

1</sup>+c·

x<sup>n−

2</sup>+ . . . +u, fitted over at least a part of the contact area.

9. The system according to claim 1, wherein the preselected criterion is an amplitude a₁ of the first harmonic of a Fourier series expansion of the signal σ

(x) representing the change in the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

10. The system according to claim 1, wherein the preselected criterion is an amplitude a₂ of the second harmonic of a Fourier series expansion of the signal σ

(x) representing the change in the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

11. The system according to claim 1, wherein the preselected criterion is a mean value of the values of the derivative dσ

(x)/dx of the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

12. The system according to claim 1, wherein the preselected criterion is a standard deviation of the values of the derivative dσ

(x)/dx of the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

13. The system according to claim 1, wherein the preselected criterion is a sum of the squares of the values of the derivative dσ

(x)/dx of the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

14. The system according to claim 1, wherein the preselected criterion is a maximal value of the values of the derivative dσ

(x)/dx of the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

15. The system according to claim 1, wherein the preselected criterion is a value of the weight <

<

a>

>

of an n'"'"'h order polynomial dσ

(x)/dx=a·

xⁿ+b·

x<sup>n−

1</sup>+c·

x<sup>n−

2</sup>+ . . . +u, fitted to the values of the derivative dσ

(x)/dx of the tangential stresses measured in the longitudinal direction, the values being taken in at least a part of the contact area.

16. The system according to claim 2, wherein the means for finding in the signal the values corresponding to the sensor passing through the contact area of the tire on the ground comprise detection of the maximum and the minimum of σ

(x).

17. The system according to claim 16, wherein the values are taken between the maximum and the minimum.

18. The system according to claim 1, comprising indicators for certain of the operating parameters of the tire, chosen from the group consisting of the load and pressure of the tire and the camber angle of the tire and the speed of the tire and the transmitted torque and the drift angle and the lateral thrust Y, and comprising means for selecting as a function of the chosen indicators a predetermined characteristic curve of change in the maximal grip coefficient p as a function of the values of the said preselected “

grip”

criterion, and comprising means for deriving an estimate of the maximal grip coefficient μ

from the said instantaneous value.

19. The system according to claim 1, comprising indicators for certain of the operating parameters of the tire, chosen from the group consisting of the load and pressure of the tire and the camber angle of the tire and the speed of the tire and the transmitted torque and the drift angle and the lateral thrust Y, and comprising means for calculating an estimate of the maximal grip coefficient μ

as a function of the chosen indicators and the values of the said preselected “

grip”

criterion, with the aid of mathematical equations whose parameters have been fitted.