Vehicle brake hydraulic pressure control apparatus and road surface friction coefficient estimating device

Patent metadata

Field	Value
Publication number	US-9550480-B2
Application number	US-201213653876-A
Country	US
Kind code	B2
Filing date	Oct 17, 2012
Priority date	Oct 21, 2011
Publication date	Jan 24, 2017
Grant date	Jan 24, 2017

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.

First claim

The invention claimed is:

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 at the time of turning smaller than the pressure reduction threshold values at the time of straight running,
wherein the pressure reduction threshold value at the time of straight running is a first threshold value, the pressure reduction threshold value at the time of turning is a second threshold value, and the first threshold value is larger than the second threshold value, and further comprising:

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, and
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.

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, 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.

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, 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 ,
wherein the road surface friction coefficient judging module further includes:
a low friction coefficient (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.

9. The controller of claim 1 ,
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.

10. The controller of claim 1 ,
wherein the first estimating module calculates the first road surface friction coefficient from a lateral acceleration filter value obtained by performing a filtering process.

11. The controller of claim 1 ,
wherein the road surface friction coefficient judging module further includes:
a low friction coefficient (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 configu

Assignees

• Nissin Kogyo Kk
• Autoliv Nissin Brake Systems Japan Co Ltd

Inventors

• Asano Kiyonori

Classifications

• B60T8/17551

  determining control parameters related to vehicle stability used in the regulation, e.g. by calculations involving measured or detected parameters · CPC title

• B60T8/17616

  Microprocessor-based systems · CPC title

• B60T8/1755

  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 title

• B60T2210/12

  Friction · CPC title

• B60T8/17636 Primary

  Microprocessor-based systems · CPC title