Estimating adhesion potential by assessing rolling radius

Patent metadata

Field	Value
Publication number	US-9821815-B2
Application number	US-201415103947-A
Country	US
Kind code	B2
Filing date	Dec 15, 2014
Priority date	Dec 18, 2013
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

A method is provided for determining an adhesion potential of a tire mounted on a wheel and travelling over ground. The method utilizes a database constructed to contain information obtained by evaluating experimental data on an evolution of a rolling radius of the tire as a function of predetermined rolling conditions of the tire on ground of variable and known adhesion. Based on the information in the database, an estimation model (M adpot ) of an adhesion potential is established by determining a function linking an adhesion potential (μ max ) of the tire to a rolling radius (RRt) of the tire and to vehicle parameters. The rolling radius (RRt) of the tire is determined while the tire is rolling. The adhesion potential (μ max ) of the tire is evaluated by application of the estimation model (M adpot ) and as a function of the vehicle parameters.

First claim

The invention claimed is:

1. A method for determining an adhesion potential (μ max ) of a tire mounted on a wheel of a vehicle travelling over ground, the method comprising steps of:
(a) constructing a database of information obtained by evaluating experimental data on an evolution of a rolling radius (RRt) of the tire as a function of predetermined rolling conditions of the tire on ground of variable and known adhesion;
(b) based on the information in the database, establishing an adhesion-potential estimation model (M adpot ) by determining a function linking an adhesion potential (μ max ) of the tire to the rolling radius (RRt) of the tire and to vehicle parameters; and
(c) determining the rolling radius (RRt) of the tire while the tire is rolling, and determining the adhesion potential (μ max ) of the tire as a function of the vehicle parameters by applying the adhesion-potential estimation model (M adpot ).

2. The method according to claim 1 , wherein the rolling radius (RRt) of the tire is determined by establishing a ratio between a speed of movement (V sol ) of the vehicle relative to the ground and a speed of rotation (Ω) of the wheel about an axis of the wheel according to:
RRt=V sol /Ω.

3. The method according to claim 2 , wherein the rolling radius (RRt) of the tire is determined by averaging rolling-radius measurements of the tire acquired during a mean period.

4. The method according to claim 3 , wherein the mean period is between 1 and 10 seconds, inclusive, with between 2.5 and 3.5 seconds, inclusive, being preferable for the mean period.

5. The method according to claim 4 , wherein the rolling radius (RRt) of the tire is determined by using the speed of movement (V sol ) of the vehicle relative to the ground obtained using a GPS system onboard the vehicle and the rotation speed (Ω) of the wheel obtained using a coder that generates a plurality of pulses on each wheel revolution.

6. The method according to claim 5 , wherein the rolling radius (RRt) of the tire is determined on each pulse generated by the coder.

7. The method according to claim 1 , wherein the adhesion-potential estimation model (M adpot ) is applied when the rolling radius (RRt) of the tire is below a predetermined threshold.

8. The method according to claim 1 , wherein the adhesion-potential estimation model (M adpot ) estimates the adhesion potential (μ max ) according to:
μ max =α 1 e (RRt) +α 2 Ze (RRt) +α 3 Pe (RRt) +α 4 Z +α 5 P+α 6 PZ+α 7 ,

where RRt represents the rolling radius of the tire, Z represents a load applied to the wheel, P represents a tire pressure value, and α 1 , α 2 , α 3 , α 4 , α 5 , α 6 , α 7 are constants.

9. The method according to claim 8 , wherein the tire pressure value (P) is given by:
P=P TPMS +α 8 V sol 2 ,

where P TPMS represents a value of a pressure given by a sensor accommodated inside the tire, V sol represents the speed of movement of the vehicle relative to the ground, and a 8 is a constant.

10. The method according to claim 8 , further comprising a step of:
(d) determining a free load (Z free ) applied to the wheel by carrying out the steps (a), (b), and (c) during which, when the vehicle is not engaged in a turn and is not subject to any transverse or longitudinal acceleration, when a zero drive or braking torque is applied to the wheel, and when the wheel is under free rolling conditions:
detecting that the ground on which the vehicle is travelling is dry,
estimating the rolling radius (RRt) of the tire, and
searching for a value of Z that causes the adhesion-potential estimation model (M adpot ) to determine the adhesion potential (μ max ) to be equal to 1, the value of Z corresponding to the free load (Z free ).

11. The method according to claim 10 , further comprising a step of determining a mean free load (Z meanfree ) during a period when the ground on which the vehicle is travelling is dry.

12. The method according to claim 10 , wherein the adhesion potential (μ max ) is determined using the adhesion-potential estimation model (M adpot ), and based on the rolling radius (RRt) of the tire, the tire pressure value (P), and the free load (Z free ) or the mean free load (Z meanfree ).

13. The method according to claim 10 , wherein the adhesion potential (μ max ) is determined using the adhesion-potential estimation model (M adpot ) and based on the rolling radius (RRt), the tire pressure value (P), and the load (Z) equal to an instantaneous load (Z inst ) applied to the wheel and calculated using a function defining a dynamic of the vehicle corresponding to vehicle data at a given moment that includes any one or any combination of two or more of:
the free load (Z free ) on the wheel or the mean load (Z meanfree ),
a drive or braking torque,
a drift angle,
transverse and longitudinal accelerations, and
a camber angle.

14. The method according to claim 8 , wherein the load (Z) is determined as a function of a measurement of a distance between a point situated on a chassis of the vehicle and a point situated on a support of the wheel and a stiffness of a suspension connecting the support to the chassis.

15. The method according to claim 1 , wherein the adhesion potential (μ max ) of the tire determined in the step (c) corresponds to a tire mounted on a non-steered and non-driving wheel.

Assignees

• Michelin & Cie
• Michelin Rech Tech

Inventors

• Duvernier Marc

Classifications

• B60T8/172

  Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters {(B60T8/17551 takes precedence)} · CPC title

• B60W2520/10

  Longitudinal speed · CPC title

• B60W2520/28

  Wheel speed · CPC title

• B60W40/068 Primary

  Road friction coefficient · CPC title

• B60W40/12 Primary

  related to parameters of the vehicle itself {, e.g. tyre models} · CPC title