EP2114752A1

EP2114752A1 - Device for correcting the course of a motor vehicle comprising first means for selectively braking the wheels and second means for turning the rear wheels

Info

Publication number: EP2114752A1
Application number: EP07823723A
Authority: EP
Inventors: Stéphane Guegan; Richard Pothin
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2006-10-16
Filing date: 2007-08-17
Publication date: 2009-11-11
Also published as: FR2907090A1; WO2008047014A1; FR2907090B1; JP5460325B2; JP2010506790A

Abstract

The invention relates to a device for correcting the actual course followed by a motor vehicle (10) comprising four steered wheels (12, 14), which have first means (18, 20) for correcting the actual course of the vehicle (10) with respect to a first reference course (30) by individually or collectively braking the four wheels (12, 14) of the motor vehicle (10), the correcting first means (18, 20) being employed when the discrepancy between the actual course of the vehicle (10) and the first reference course (30) exceeds an activation threshold value (32), characterized in that it includes second means (34, 14) for correcting the actual course followed by the vehicle (10) with respect to a second reference course (36) by turning the two steered rear wheels (14) through a correction angle (A2).

Description

"DEVICE FOR CORRECTING THE TRACK OF A

MOTOR VEHICLE COMPRISING FIRST

SELECTIVE BRAKING MEANS FOR WHEELS AND

The invention relates to a device for correcting the real trajectory of a motor vehicle.

The invention more particularly relates to a device for correcting the real trajectory of a motor vehicle comprising four steering wheels, which comprises first means for correcting the real trajectory of the vehicle with respect to a first reference trajectory by individual or combined braking. of the four wheels of the motor vehicle, the first correction means being implemented when the distance between the real trajectory of the vehicle and the first reference trajectory is greater than an activation threshold.

In some situations, the driver of a motor vehicle may lose control of his vehicle. This loss of control may be due to external causes. This is particularly the case when the vehicle is traveling on a slippery road, because of moisture or ice, or when the vehicle is exposed to a strong side wind.

It is considered that a driver controls the vehicle when the trajectory of the vehicle is in line with the expectations of the driver, that is to say when the trajectory of the motor vehicle follows a reference path.

To mitigate the external causes of loss of control of the vehicle, it is known to equip the vehicle with means for correcting the path by braking individually or combined four wheels of the vehicle. These means are more particularly known by the acronym "ESP" or "Electronic Stability Program". By selectively braking one or more wheels, the "ESP" produces a yaw moment and a deceleration that can bring the vehicle back to the reference path.

For example, in case of oversteer, that is to say when the radius of gyration of the vehicle is less than the radius of gyration of the reference trajectory, the "ESP" controls the braking of the outer front wheel.

According to another example, in the event of understeer, ie when the radius of gyration of the vehicle is greater than the radius of gyration of the reference trajectory, the "ESP" controls the braking of the four wheels with greater efforts on the inner wheels. In this last example, the "ESP" is also likely to act on the engine torque to complete the action of the brakes. However, it is not desirable that the "ESP" be too sensitive. Indeed, if the "ESP" is triggered too often, it can disturb the driver. It is therefore preferable that the "ESP" be triggered only in potentially dangerous situations and not just to fine-tune the trajectory of the vehicle. To solve this problem and improve the driving comfort of the vehicle without involving the "ESP" too often, the invention proposes a trajectory correction device of the type described above, characterized in that it comprises second correction means the actual trajectory of the vehicle relative to a second reference trajectory by pivoting the two rear steered wheels with a correction angle.

According to other features of the invention:

the second correction means are implemented as soon as the real trajectory of the vehicle deviates from its second reference trajectory; the spacing between the second reference trajectory and the first reference trajectory is less than the activation threshold of the first correction device

the first and the second reference trajectory are calculated by electronic control units, in particular as a function of the steering angle of a steering wheel of the motor vehicle;

- The electronic control unit of the second correction means is capable of controlling the two rear wheels steering pivoting of an angle of participation in the gyration of the vehicle;

- The angle of participation of the rear wheels is determined in particular according to the steering angle of the steering wheel and the longitudinal speed of the motor vehicle - the device comprises means for detecting a malfunction of the second correction means;

when a malfunction of the second correction means is detected, the activation threshold of the first correction means is lowered. Other features and advantages will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings among which:

FIG. 1 schematically represents a motor vehicle equipped with a device for correcting the trajectory according to the invention

- Figure 2 schematically shows the reference paths of a motor vehicle in a bend.

For the remainder of the description, a longitudinal, vertical and transverse orientation indicated by the "L, V, T" trihedron of FIG. 1 will be adopted without limitation. The rotation of the vehicle around its vertical axis will be called later

"lace" . Subsequently identical, similar or similar elements will be designated by the same reference numbers.

There is shown in Figure 1 a motor vehicle 10 which is equipped with two front steering wheels 12 and two rear guide wheels 14. Thus, the rear wheels 14 are pivotable about a substantially vertical axis.

The front wheels 12 are pivotally controlled by the driver of the vehicle via a steering wheel 16. Thus, the steering wheel 16 is likely to be rotated by a certain steering angle "A1" by the driver.

The vehicle 10 is equipped with a device for correcting the trajectory which comprises first means for correcting the trajectory of the "ESP" type.

For this purpose, each wheel 12, 14 of the vehicle 10 is equipped with braking means 18. The braking means 18 of each wheel 12, 14 can be controlled independently by a first electronic control unit intermediate of the control circuit which is shown in dashed lines in Figure 1. The first electronic control unit 20 is also able to act on the engine torque (not shown).

The first electronic control unit 20 also receives information concerning the path desired by the driver and the actual trajectory of the vehicle. Thus, the trajectory desired by the driver is determined from the steering angle "A1" of the steering wheel 16 and the longitudinal speed of the vehicle 10. For this purpose, the steering wheel 16 comprises an angular sensor 22 and the vehicle comprises a longitudinal velocity sensor 24. The actual trajectory is determined in particular from the lateral acceleration of the vehicle and the yaw rate of rotation of the vehicle. For this purpose, the vehicle 10 comprises a sensor lateral acceleration 26 and a yaw rate sensor 28 of the vehicle 10.

As represented in FIG. 2, the first electronic control unit 20 calculates, on the basis of the information provided by the angular sensor 22 of the steering wheel 16 and by the longitudinal speed sensor 24 of the vehicle 10, a first reference trajectory 30 which is considered by the first electronic control unit 20 as the desired path by the driver.

For example, the first reference trajectory 30 is calculated according to the following equation: in which :

- M is the total mass of the vehicle;

- l _z is the inertia of the vehicle around a vertical axis passing through its center of gravity; l_i is the distance between the center of gravity and the front axle; l_2 is the distance between the center of gravity and the rear axle;

- Di is the rigidity of forward drift;

D ₂ is the rear drift rigidity;

ai is the angle made by the front wheels 12 with the longitudinal axis of the vehicle;

- V is the longitudinal speed of the vehicle; ψ is the yaw rate of the vehicle around its center of gravity along a vertical axis;

- β is the drift angle that the velocity vector of the vehicle with its longitudinal axis. Then the first electronic control unit 20 defines two lines 32 on either side of the first reference path 30 which are spaced from the first reference trajectory 30 with a predetermined spacing "E1". These two lines 32 form activation thresholds of the first correction means of the trajectory "ESP".

The first electronic control unit 20 also determines the real trajectory of the vehicle from the data communicated by the lateral acceleration sensor 26 and the yaw rate sensor 28 as well as from the longitudinal speed sensor 24 of the vehicle. 10.

If the actual trajectory calculated by the first electronic control unit is between the two activation thresholds 32, the trajectory correction device is not implemented.

On the other hand, if the real trajectory deviates too much from the first reference trajectory 30, that is to say if the real trajectory intersects one of the activation thresholds 32, the trajectory correction device "ESP "is implemented. The first electronic control unit 20 then acts selectively on the brakes 18 of the wheels 12, 14 and possibly on the engine of the vehicle 10 to bring the real trajectory of the vehicle between the two activation thresholds 32.

According to the teachings of the invention, the device for correcting the trajectory of the vehicle 10 comprises second means "4RD" for correcting the trajectory by pivoting the rear guide wheels 14.

For this purpose, as shown in Figure 1, the vehicle 10 comprises a second electronic control unit 34 which is capable of controlling the rear wheels 14 director pivoting a correction angle "A2".

The second electronic control unit 34 determines the correction angle "A2" by comparing a trajectory desired by the driver, in the form of a second reference path, and the actual trajectory of the vehicle.

The second electronic control unit 34 thus also receives information concerning the trajectory desired by the driver and the real trajectory of the vehicle 10.

The second reference trajectory and the real trajectory of the vehicle 10 are determined from the same information from the same sensors 22, 24, 26, 28 as previously described for the first correction means. Thus, when the real trajectory calculated by the second electronic control unit 34 deviates from the second reference trajectory, that is to say when the real trajectory is not superimposed on the second reference trajectory, the second electronic unit control acts on the orientation of the guide rear wheels 14 by applying the correction angle "A2" to return the vehicle 10 on its second reference path.

However, the second reference trajectory is not necessarily identical to the first reference trajectory. Indeed, it happens that the two correction means are designed separately and they both have different models for calculating the associated reference trajectory. This is particularly the case when the correction means "ESP" and "4RD" are provided by two different suppliers. As represented in FIG. 2, under the same running conditions of the vehicle 10 and from the same information, the second reference trajectory 36 is not then confused with the first reference trajectory 30.

So that the two means for correcting the trajectory "ESP" and "4RD" do not act simultaneously in the opposite direction on the vehicle 10, it is necessary that the second reference trajectory 36 be between the activation thresholds 32 of the first means of correction "ESP". Thus, if the real trajectory of the vehicle follows the second reference trajectory 36, neither of the two correction means "ESP", "4RD" is implemented.

As long as the real trajectory of the vehicle 10 deviates from the second reference trajectory 36 without going beyond the limits of the activation thresholds 32, only the second correction means

"4RD" are implemented. The first means of correction

"ESP" are not implemented.

When the real trajectory of the vehicle 10 exceeds the limits set by the activation thresholds 32, the two correction means "ESP" and "4RD" are implemented simultaneously so as to bring the vehicle 10 between the thresholds first. When this first step is performed, the first correction means "ESP" are deactivated and the second correction means "4RD" remain activated to bring the vehicle 10 back onto the second reference trajectory 36.

So that the condition that the second reference trajectory 36 is always included between the two activation thresholds 32 is respected, a step of setting the first correction means "ESP" is therefore performed. During this adjustment step, the spacing "E1" of the activation thresholds 32 is adjusted so as to include the second reference trajectory 36. According to another aspect of the invention, the first correction means "ESP" are likely to be activated in a so-called degraded operating mode when the second correction means "4RD" suffer a malfunction or failure. For example, the malfunction is detected by comparing a measurement made by a rear wheel pivot angle sensor 14 (not shown) with the pivot angle controlled by the second electronic control unit. control 34. If this angle measurement does not correspond to the angle controlled by the second electronic control unit 34, it is considered that there is a malfunction.

The activation thresholds 32 of the first correction means "ESP" are then tightened so that the trajectory of the vehicle 10 is corrected more often by the first correction means "ESP" than when the two correction means "ESP" and " 4RD "are functional. Thus, in degraded operating mode, the spacing "E2" of the activation thresholds 32 with respect to the reference trajectory 30 is smaller than their spacing "E1" in normal operating mode.

According to a variant of the invention, the second electronic control unit 34 is able to control the rear wheels 14 pivotally at an angle of participation

"A3" to the gyration of the vehicle 10 also called "angle of typing of the vehicle".

This feature makes it possible to modify the radius of gyration of the vehicle 10 for the same steering angle "A1" of the steering wheel 16 in particular as a function of the longitudinal speed of the vehicle

1 0.

Thus, if the speed of the vehicle 10 is very low and the driver wishes to strongly steer the vehicle 10, the second electronic control unit 34 controls the rear wheels 14 pivotally in a direction of rotation opposite that of the front wheels 12 in order to reduce the radius of gyration of the vehicle.

Conversely, if the vehicle is traveling at high speed, the second electronic control unit 34 controls the rear wheels 14 pivotally in the same direction of rotation as the front wheels 12 in order to increase the radius of gyration so that the driver can refine his trajectory without risk of skidding. The second electronic control unit is thus capable of transmitting two types of control towards the rear wheels 14: on the one hand a pivoting control according to a correction angle "A2", on the other hand a pivoting control according to a participation angle "A3" when turning the vehicle.

The second participation angle "A3" is taken into account by the driver to define his desired trajectory. The second participation angle "A3" must therefore be taken into account both by the first electronic control unit 20 to determine the first reference trajectory 30 and also by the second electronic control unit 34 to determine the second reference trajectory 36.

On the other hand, the first correction angle "A2" must in no case be taken into account by the electronic control units 20, 34 to define the reference trajectories 30, 36 because it is not an information that can influence on the path desired by the driver.

For example, the first reference trajectory 30 is then calculated according to the following equation:

in which :

- M is the total mass of the vehicle;

- l _z is the inertia of the vehicle around a vertical axis passing through its center of gravity;

Li is the distance between the center of gravity and the front axle;

₂ is the distance between the center of gravity and the rear axle;

- Di is the rigidity of forward drift; D ₂ is the rear drift rigidity;

- Ct2 is the angle of participation "A3" that make the rear wheels 14 with the longitudinal axis of the vehicle;

- V is the longitudinal speed of the vehicle; ψ is the yaw rate of the vehicle around its center of gravity along a vertical axis; β is the angle of drift made by the vehicle speed vector with its longitudinal axis.

Thanks to the correction device according to the invention, it is thus possible to finely correct the trajectory of the motor vehicle 10 without constantly involving the first correction means "ESP".

Claims

REVEN D ICATIONS

1. Device for correcting the real trajectory of a motor vehicle (10) comprising four steering wheels (12, 14), which comprises first means (18, 20) for correcting the real trajectory of the vehicle (10) with respect to a first reference trajectory (30) by individual or combined braking of the four wheels (12, 14) of the motor vehicle (10), the first correction means (18, 20) being implemented when the distance between the real trajectory of the vehicle (10) and the first reference trajectory (30) is greater than an activation threshold (32), characterized in that it comprises second correction means (34, 14) of the real trajectory of the vehicle (10). ) relative to a second reference path (36) by pivoting the two rear guide wheels (14) by a correction angle (A2).

2. Device according to the preceding claim, characterized in that the second correction means (34, 14) are implemented as soon as the real trajectory of the vehicle deviates from its second reference path (36).

3. Device according to the preceding claim, characterized in that the spacing between the second reference path (36) and the first reference path (30) is less than the activation threshold (32) of the first correction device (20). , 18).

4. Device according to any one of the preceding claims, characterized in that the first and second reference paths (30, 36) are calculated by electronic control units (20, 34) in particular according to the angle of steering (A1) of a steering wheel (16) of the motor vehicle (1 0).

5. Device according to any one of the preceding claims, characterized in that the electronic control unit (34) of the second correction means is capable of controlling the two rear steering wheels (14) pivoting a participation angle (A3) to the vehicle turning (10).

6. Device according to the preceding claim, characterized in that the angle of engagement of the rear wheels (14) is determined in particular according to the steering angle (A1) of the steering wheel (16) and the longitudinal speed of the motor vehicle (10).

7. Device according to any one of the preceding claims, characterized in that it comprises means for detecting a malfunction of the second correction means.

8. Device according to the preceding claim, characterized in that, when a malfunction of the second correction means is detected, the activation threshold (32) of the first correction means is lowered.