VEHICLE BRAKE HYDRAULIC PRESSURE CONTROL APPARATUS AND ROAD SURFACE FRICTION COEFFICIENT ESTIMATING DEVICE

• US 20130103279A1
• Filed: 10/17/2012
• Published: 04/25/2013
• Est. Priority Date: 10/21/2011
• Status: Active Grant

• Current Assignee: Autoliv Nissin Brake Systems Japan Co., Ltd.
• Original Assignee: Nissin Kogyo Company Limited (Hitachi, Ltd.)
• Inventors: ASANO, Kiyonori
• Granted Patent: US 9,550,480 B2
• Time in Patent Office: Days
• US Class Current: 701/72
• CPC Class Codes: B60T 2201/16 Curve braking control, e.g. turn control within ABS control algorithm
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 2270/313 with less than three sensors (yaw rate, steering angle, lateral acceleration)
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02
• 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
• CPC Class Codes: B60T 8/17616 Microprocessor-based systems
• CPC Class Codes: B60T 8/17636 Microprocessor-based systems

Abstract

One embodiment provides a vehicle brake hydraulic controller including: an antilock braking controlling module configured to perform an antilock braking control in which a brake hydraulic pressure applied to wheel brakes is reduced under the condition that a slip-related amount has reached a pressure reduction threshold value; and a turning judging module configured to judge whether a vehicle is turning based on a steering angle, wherein, when the antilock braking control is performed and in the case that the turning judging module judges that the vehicle is turning, the antilock braking controlling module performs a turning pressure reduction control so as to: change the pressure reduction threshold values to be more easily reached by the slip-related amount than at the time of straight running; and change the pressure reduction amounts to be larger than that at the time of straight running.

Claims

1. A vehicle brake hydraulic controller including:

an antilock braking controlling module configured to perform an antilock braking control in which a brake hydraulic pressure applied to wheel brakes is reduced under the condition that a slip-related amount has reached a pressure reduction threshold value, the slip-related amount being calculated using a vehicle speed and a wheel speed; and

a turning judging module configured to judge whether a vehicle is turning based on a steering angle,

wherein, when the antilock braking control is performed and in the case that the turning judging module judges that the vehicle is turning, the antilock braking controlling module performs a turning pressure reduction control so as to;

change the pressure reduction threshold values to be more easily reached by the slip-related amount than at the time of straight running; and

change the pressure reduction amounts to be larger than that at the time of straight running.

2. The controller of claim 1, further including:

a turning state judging module configured to judge whether the vehicle is in an under-steering state, a neutral-steering state or an over-steering state,

wherein the antilock braking controlling module performs;

the turning pressure reduction control only for the front wheels in the case that the turning state judging module judges that the vehicle is in the under-steering state;

the turning pressure reduction control for the front wheels and the rear wheels in the case that the turning state judging module judges that the vehicle is in the neutral-steering state; and

the turning pressure reduction control only for the rear wheels in the case that the turning state judging module judges that the vehicle is in the over-steering state.

3. The controller of claim 2,

wherein, in the turning pressure reduction control that is performed only for the front wheels in the under-steering state, the pressure reduction threshold value is adjusted to be more easily reached than at the neutral-steering state, and the pressure reduction amount is adjusted to be larger more than at the neutral-steering state.

4. The controller of claim 2,

wherein, in the turning pressure reduction control that is performed only for the front wheels in the under-steering state, the pressure reduction threshold value of the outer wheel at the time of turning is adjusted to be more easily reached than the pressure reduction threshold value of the inner wheel at the time of turning.

5. The controller of claim 2,

wherein, in the turning pressure reduction control that is performed only for the rear wheels in the over-steering state, the pressure reduction threshold value is adjusted to be more easily reached than at the neutral-steering state, and the pressure reduction amount is adjusted to be larger than at the neutral-steering state.

6. The controller of claim 2,

wherein the turning state judging module includes:

a normative yaw rate calculation section configured to calculate a normative yaw rate using the steering angle and the vehicle speed;

a road surface limit yaw rate calculation section configured to calculate a road surface limit yaw rate using a lateral acceleration and the vehicle speed; and

a target yaw rate calculation section configured to calculate a target yaw rate from the normative yaw rate and the road surface limit yaw rate,

wherein the turning state judging module compares the target yaw rate with an actual yaw rate actually applied to the vehicle to thereby judge;

that the vehicle is in the under-steering state in the case that the actual yaw rate is smaller than a value obtained by subtracting a first given value from the target yaw rate;

that the vehicle is in the over-steering state in the case that the actual yaw rate is larger than a value obtained by adding a second given value to the target yaw rate; and

that the vehicle is in the neutral-steering state in the case that the vehicle is not judged to be in the under-steering state or the over-steering state.

7. The controller of claim 1,

wherein the slip-related amount is a slip amount obtained by subtracting the wheel speed from the vehicle speed, and

wherein, when the slip amount becomes larger than the pressure reduction threshold value, the antilock braking controlling module reduces the brake hydraulic pressure applied to the wheel brakes.

8. The controller of claim 1, further including:

a road surface friction coefficient judging module configured to judge whether a road surface on which the vehicle is running is at least a low friction coefficient road surface, and

wherein the antilock braking controlling module performs the turning pressure reduction control only in the case that the road surface is judged to be the low friction coefficient road surface.

9. The controller of claim 8,

wherein the road surface friction coefficient judging module includes:

a first estimating module configured to estimate a first road surface friction coefficient based on a lateral acceleration;

a second estimating module configured to estimate a second road surface friction coefficient based on a longitudinal acceleration;

a selecting module configured to select either the first road surface friction coefficient or the second road surface friction coefficient as a road surface friction coefficient of the road surface; and

a low μ

road judging module configured to judge that the road surface is the low friction coefficient road surface when the road surface friction coefficient selected by the selecting module is smaller than a fourth given value,

wherein the selecting module has a limit steering judgment section configured to judge whether steering exceeding the limit of road surface conditions is performed based on at least the steering angle and the vehicle speed, and

wherein the selecting module selects;

the first road surface friction coefficient or the second road surface friction coefficient, whichever smaller, as the road surface friction coefficient when limit steering judgment section judges that steering exceeding the limit of road surface conditions is performed; and

the second road surface friction coefficient as the road surface friction coefficient when limit steering judgment section judges that steering exceeding the limit of road surface conditions is not performed.

10. The controller of claim 8,

wherein the road surface friction coefficient judging module includes:

a first estimating module configured to estimate a first road surface friction coefficient based on a lateral acceleration;

a second estimating module configured to estimate a second road surface friction coefficient based on a longitudinal acceleration; and

a selecting module configured to select either the first road surface friction coefficient or the second road surface friction coefficient as a road surface friction coefficient of the road surface,

wherein the selecting module has a limit steering judgment section configured to judge whether steering exceeding the limit of road surface conditions is performed based on at least the steering angle and the vehicle speed, and

wherein the selecting module selects;

the first road surface friction coefficient or the second road surface friction coefficient, whichever smaller, as the road surface friction coefficient when limit steering judgment section judges that steering exceeding the limit of road surface conditions is performed; and

the second road surface friction coefficient as the road surface friction coefficient when limit steering judgment section judges that steering exceeding the limit of road surface conditions is not performed.

11. The controller of claim 10,

wherein the limit steering judgment section includes:

a normative yaw rate calculation section configured to calculate a normative yaw rate from the steering angle and the vehicle speed;

a road surface limit yaw rate calculation section configured to calculate a road surface limit yaw rate from a lateral acceleration and the vehicle speed; and

a yaw rate judgment section configured to judge whether the deviation obtained by subtracting the road surface limit yaw rate from the normative yaw rate is larger than a third given value, and

wherein the limit steering judgment section judges;

that steering exceeding the limit of road surface conditions is performed in the case that the deviation is larger than the third given value; and

that steering exceeding the limit of road surface conditions is not performed in the case that the deviation is not larger than the third given value.

12. The controller of claim 10,

wherein the first estimating module calculates the first road surface friction coefficient from a lateral acceleration filter value obtained by performing a filtering process in which an absolute value of the lateral acceleration is made difficult to be changed to the decreasing side.

13. The controller of claim 10,

wherein the road surface friction coefficient judging module further includes:

a low μ

road judging module configured to judge whether the road surface is the low friction coefficient road surface,

wherein the low μ

road judging module includes;

a first judgment section configured to judge whether a first condition that the road surface friction coefficient is smaller than a fourth given value is satisfied; and

at least one of a second judgment section configured to judge whether a second condition that an estimated lateral acceleration calculated based on an actual yaw rate actually applied to the vehicle is smaller than a fifth given value is satisfied, and a third judgment section configured to judge whether a third condition that a locking hydraulic pressure in the antilock braking control is smaller than a sixth given value is satisfied, and

wherein the low μ

road judging module judges that the road surface is the low friction coefficient road surface when the first condition and at least one of the second and third conditions are satisfied.

14. The controller of claim 13,

wherein the road surface friction coefficient judging module estimates the road surface friction coefficient using an actual lateral acceleration obtained by a lateral acceleration sensor.

15. The controller of claim 13,

wherein the second judgment section calculates:

a tentatively estimated lateral acceleration obtained from the absolute value of the actual yaw rate and the vehicle speed; and

the estimated lateral acceleration obtained by subjecting the tentatively estimated lateral acceleration to a filtering process in which the tentatively estimated lateral acceleration is made difficult to be changed only to the decreasing side.

16. The controller of claim 13,

wherein the third judgment section judges that the third condition is satisfied when the locking hydraulic pressures of the right front wheel and the left front wheel are respectively smaller than the sixth given value that is the same for all the wheels or different for the respective wheels.