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

• US 20040032165A1
• Filed: 06/13/2003
• Published: 02/19/2004
• Est. Priority Date: 06/13/2002
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Levy, Georges, Fangeat, Nicolas
• Granted Patent: US 6,971,726 B2
• Time in Patent Office: Days
• 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 for controlling the stability of a vehicle having tires, the system including a controller using at least the parameter slip G^Opt corresponding to a predetermined value of the coefficient of friction μ, or the system including a controller maintaining the functioning of the tire at an optimum value δ^Opt of the drift angle corresponding to the maximum value of the drift thrust F_target, the controller including means for performing the following operations (where X is either the slip G or the drift angle δ, and Y is either μ or F):

Determining estimations or measurements (X_i, Y_i) for at least one pair of values;

Determining the corresponding values of the slope α_i of the straight line passing through the origin and through (X_i, Y_i);

Calculating coefficients A_p 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); and

Calculating a target value X^Target by using a predetermined Invariant “Invt”.

Claims

1. A system for controlling the stability of a vehicle, 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 the parameter slip G^Opt corresponding to a predetermined value of the coefficient of friction μ

, the controller 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 the values of the coefficient of friction μ

_i;

(b) determining the slope α

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

_i);

(c) calculating coefficients A_p by direct calculation or by an appropriate regression from a sufficient 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 its 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:

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

4. A system for controlling the stability of a vehicle according to claim 1, in which the device for modulating the longitudinal force acts on the 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.

5. A system for controlling the stability of a vehicle having 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 the commands imparted by the vehicle driver to his control means and depending on the commands delivered by a path controller aimed at maintaining the functioning of the tire at a predetermined target value of the drift thrust F_target, the path controller using at least one optimum value δ

^Opt of the drift angle corresponding to the maximum value of the drift thrust F_target, the controller 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 the drift angle δ

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

_i;

(b) determining the slope a_i of the straight line passing through the origin and through (δ

_i, F_Yi);

(c) Calculating coefficients A_p by direct calculation or by an appropriate regression from a sufficient 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:

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

is the steering of the wheels and, in the event of the occurrence of a warning signal, the system for controlling the steering of the steered wheels 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 a warning signal, the vehicle speed is limited or reduced.

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

of a tire where the lateral force is maximal, 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 the slope α

_i of the straight line passing through the origin and through (δ

_i, F_i);

(c) calculating coefficients A_p by direct calculation or by a regression from a sufficient 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 the 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.