Vehicle Anti-Skid Brake Control System and Its Control Method

• US 20080319611A1
• Filed: 01/25/2006
• Published: 12/25/2008
• Est. Priority Date: 02/04/2005
• Status: Active Grant

• Current Assignee: BYD Company Limited
• Original Assignee: BYD Company Limited
• Inventors: Song, Youchuan
• Granted Patent: US 8,000,872 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• 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 2210/36 Global Positioning System [GPS]
• CPC Class Codes: B60T 2230/02 Side slip angle, attitude angle, floating angle, drift angle
• 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 8/17616 Microprocessor-based systems

Abstract

An anti-skid brake control system and its control method for vehicle has a signal collection unit and an electronic control unit. The electronic control unit includes a data receiving module, a data processing module and a data control module. The data receiving module receives the data collected by the signal collection unit. The data processing module calculates sideslip angles and slip rates for wheels. The data control module sets target slip rates based on the slip rates corresponding to the friction coefficient μ for different sideslip angles. The device emits control commands after comparing the calculated slip rate to the set target slip rate, so that the ABS control is real time.

Claims

1. An vehicle anti-skid brake control system, comprising a signal collection unit and an electronic control unit;

said electronic control unit comprises a data receiving module, a data processing module, and a data control module;

said data receiving module is configured to obtain the data from the signal collection unit, wherein said data processing module is configured to calculate the sideslip angles and slip rates for wheels, said data control module sets a slip rate threshold in accordance with the slip rate corresponding to the respective peak of braking force coefficient μ

at different sideslip angles, and outputs a control command in accordance with the result of comparison between the calculated slip rate and the set slip rate threshold to perform anti-skid brake control in real time.

2. The vehicle anti-skid brake control system of claim 1, wherein, said vehicle is a four-wheel vehicle, said data receiving module is configured to receive the data of the four-wheel vehicle collected by said signal collection unit, said data processing module is configured to calculate the sideslip angle α

_i and slip rate s_i for each wheel of the four-wheel vehicle, said data control module sets the lower limit s^min and upper limit s^max of respective slip rate threshold in accordance with the slip rates s_i corresponding to respective peak of braking force coefficients μ

at different sideslip angles, and outputs a control command based on the result of comparison between the calculated slip rate s_i and the set limits of slip rate threshold s^min and s^max to perform anti-skid brake control in real time;

wherein, α

_i is the sideslip angle of the i^th wheel, s_i is the slip rate of the i^th wheel, and i=1, 2, 3, or 4.

3. The vehicle anti-skid brake control system of claim 2, wherein, said signal collection unit comprises a GPS configured to obtain an instantaneous centroidal speed V_cg^GPS of the vehicle, a gyro configured to obtain an instantaneous angular speed of the vehicle, an accelerometer configured to obtain an instantaneous acceleration of the vehicle, wheel speed sensors configured to obtain instantaneous wheel rotation speeds ω

_i of the vehicle, and a steering wheel angle sensor configured to obtain an instantaneous steering wheel angle of the vehicle;

said GPS is mounted on the top of the vehicle, right above the centroid of the vehicle;

said data processing module comprises

a submodule for calculating the sideslip angle β

^GPS and the estimated yaw rate r at the centroid from said centroidal speed V_cg^GPS and angular speed,

a submodule for calculating the GPS measured values of longitudinal and lateral velocities V_x^GPS and V_y^GPS at the centroid respectively from the obtained centroidal speed V_cg^GPS and sideslip angle β

^GPS,

a submodule for calculating the estimated longitudinal and lateral velocities V_x and V_y at the centroid from the obtained GPS measured values of longitudinal and lateral velocities V_x^GPS and V_y^GPS,

a submodule for calculating the longitudinal and lateral velocities V_ix and V_iy for each wheel,

a submodule for calculating the sideslip angle α

_i for each wheel, and

a submodule for calculating the slip rate s_i for each wheel.

4. The vehicle anti-skid brake control system of claim 3, wherein, the submodule for calculating the sideslip angle β

^GPS and the estimated yaw rate r at the centroid is a yaw Kalman filter;

the submodule for calculating the GPS measured values of longitudinal and lateral velocities V_x^GPS and V_y^GPS calculates according to the equations (1) and (2);

V_x^GPS=V_cg^GPS cos(β

^GPS) 

 

(1)

V_y^GPS=V_cg^GPS sin(β

^GPS) 

 

(2)

the submodule for calculating the estimated longitudinal and lateral velocities V_x and V_y at the centroid is a Kalman filter for speed;

the submodule for calculating the longitudinal and lateral velocities V_ix and V_iy for each wheel calculates according to the equations (3)-(10);

V_1x=V_x+r(d₂+e cos(δ

)) 

 

(3)

V_1y=V_y+r(l_f+e sin(δ

)) 

 

(4)

V_2x=V_x−

r(d₂−

e cos(δ

)) 

 

(5)

V_2y=V_y+r(l_f−

e sin(δ

)) 

 

(6)

V_3x=V_x+r(d₂+e) 

 

(7)

V_3y=V_y+rl_r 

 

(8)

V_4x=V_x−

r(d₂+e) 

 

(9)

V_4y=V_y−

rl_r 

 

(10)

where, δ

is the steering angle of wheel, e is the distance from the steering knuckle spindle to the tire tread centre;

d₂ is the lateral distance from the centroid to the steering knuckle; and

l_f and l_r are the distance from the centroid to the front axle and the distance from the centroid to the rear axle, respectively;

the submodule for calculating the sideslip angle α

_i for each wheel calculates according to the equations (11)-(14);

$\begin{array}{cc}{\mathrm{\alpha <br><br>}}_1=\mathrm{\delta <br><br>}-\arctan <br><br>\frac{V_{1<br><br><br><br>y}}{V_{1<br><br><br><br>x}}& \left(11\right)\\ {\mathrm{\alpha <br><br>}}_2=\mathrm{\delta <br><br>}-\arctan <br><br>\frac{V_{2<br><br><br><br>y}}{V_{2<br><br><br><br>x}}& \left(12\right)\\ {\mathrm{\alpha <br><br>}}_3=\arctan <br><br>\frac{V_{3<br><br><br><br>y}}{V_{3<br><br><br><br>x}}& \left(13\right)\\ {\mathrm{\alpha <br><br>}}_4=\arctan <br><br>\frac{V_{4<br><br><br><br>y}}{V_{4<br><br><br><br>x}}& \left(14\right)\end{array}$

the submodule for calculating the slip rate s_i for each wheel calculates according to the equations (15);

$\begin{array}{cc}{s}_i=\frac{\sqrt{V_{\mathrm{ix}}^2+V_{\mathrm{iy}}^2}<br><br>\cos <br><br>\left({\mathrm{\alpha <br><br>}}_i\right)-r_w<br><br>{\mathrm{\omega <br><br>}}_i}{\sqrt{V_{\mathrm{ix}}^2+V_{\mathrm{iy}}^2}<br><br>\cos <br><br>\left({\mathrm{\alpha <br><br>}}_i\right)}& \left(15\right)\end{array}$

5. The vehicle anti-skid brake control system of claim 2, wherein, said data control module utilizes a look-up table method and/or an interpolation method to set the lower limit s^min and upper limit s^max of respective slip rate threshold at different sideslip angles.

6. The vehicle anti-skid brake control system of claim 2, wherein, if the slip rate s_i meets s^min<

s_i<

s^max, said data control module will output a command that keeps the wheel braking force unchanged;

if the slip rate s_i is greater than s^max, said data control module will output a command that decreases the wheel braking force; and

if the slip rate s_i is smaller than s^min, said data control module will output a command that increases the wheel braking force.

7. The vehicle anti-skid brake control system of claim 2, wherein, said system further comprises an ABS actuator unit, which comprises an ABS actuator for the first wheel, an ABS actuator for the second wheel, an ABS actuator for the third wheel, and an ABS actuator for the fourth wheel;

the four ABS actuators are independent to each other and receive the control commands from said data processing module.

14. The vehicle anti-skid brake control system of claim 3, wherein, said system further comprises an ABS actuator unit, which comprises an ABS actuator for the first wheel, an ABS actuator for the second wheel, an ABS actuator for the third wheel, and an ABS actuator for the fourth wheel;

the four ABS actuators are independent to each other and receive the control commands from said data processing module.

15. The vehicle anti-skid brake control system of claim 4, wherein, said system further comprises an ABS actuator unit, which comprises an ABS actuator for the first wheel, an ABS actuator for the second wheel, an ABS actuator for the third wheel, and an ABS actuator for the fourth wheel;

the four ABS actuators are independent to each other and receive the control commands from said data processing module.

16. The vehicle anti-skid brake control system of claim 5, wherein, said system further comprises an ABS actuator unit, which comprises an ABS actuator for the first wheel, an ABS actuator for the second wheel, an ABS actuator for the third wheel, and an ABS actuator for the fourth wheel;

the four ABS actuators are independent to each other and receive the control commands from said data processing module.

17. The vehicle anti-skid brake control system of claim 6, wherein, said system further comprises an ABS actuator unit, which comprises an ABS actuator for the first wheel, an ABS actuator for the second wheel, an ABS actuator for the third wheel, and an ABS actuator for the fourth wheel;

the four ABS actuators are independent to each other and receive the control commands from said data processing module.

8. An vehicle anti-skid brake control method, comprising:

step 1;

a data collection unit collecting vehicle data;

step 2;

an electronic control unit receiving the vehicle data collected by the data collection unit, and calculating sideslip angles and slip rates for the vehicle wheels from said data;

step 3;

the electronic control unit setting the slip rate threshold for respective sideslip angle in accordance with the slip rate corresponding to the respective peak of braking force coefficient μ

at different sideslip angles; and

step 4;

the electronic control unit comparing the calculated slip rate with the set slip rate threshold, and outputting an ABS control command in accordance with the result of comparison.

9. The vehicle anti-skid brake control method of claim 8, wherein, said vehicle is a four-wheel vehicle, and said data collection unit collects the data for the four-wheel vehicle through the following steps:

step 1′

;

the data collection unit collecting the data for each wheel of the four-wheel vehicle;

step 2′

;

the electronic control unit receiving the data for each wheel of the four-wheel vehicle collected by the data collection unit and calculating sideslip angle α

_i and slip rate s_i for each wheel of the four-wheel vehicle from said data;

step 3′

;

the electronic control unit setting the lower limit s^min and the upper limit s^max of respective slip rate thresholds at different sideslip angles in accordance with the different slip rates corresponding to the respective peak of braking force coefficients μ

at the different sideslip angles; and

step 4′

;

the electronic control unit comparing the calculated slip rate s_i with the slip rate limits s^min and s^max, and outputting a control command;

where, α

_i is the sideslip angle of the i^th wheel, s_i is the slip rate of the i^th wheel, and i=1, 2, 3, or 4.

10. The vehicle anti-skid brake control method of claim 9, wherein said signal collection unit comprises a GPS, a gyro, an accelerometer, wheel speed sensors, and a steering wheel angle sensor;

said GPS is mounted on the top of the vehicle, right above the centroid of the vehicle;

said step 1′

that is used to collect the data for each wheel of the four-wheel vehicle comprises;

the GPS measuring an instantaneous centroidal speed V_cg^GPS of the running vehicle, the gyro measuring an instantaneous angular speed of the running vehicle, the accelerometer measuring an instantaneous acceleration of the running vehicle, the wheel speed sensors measuring instantaneous wheel rotation speeds ω

_i of the running vehicle, and the steering wheel angle sensor measuring an instantaneous steering wheel angle of the running vehicle; and

said step 2′

that is used to calculate the sideslip angle α

_i and slip rate s_i for each wheel of the four-wheel vehicle comprises;

calculating the sideslip angle β

^GPS and estimated yaw rate r at the centroid from said centroidal speed V_cg^GPS and angular speed;

calculating the GPS measured values of longitudinal and lateral speeds V_x^GPS and V_y^GPS at the centroid from said centroidal speed V_cg^GPS and sideslip angle β

^GPS;

calculating the estimated longitudinal and lateral velocities V_x and V_y at the centroid from the measured GPS values of longitudinal and lateral velocities V_x^GPS and V_y^GPS;

calculating the estimated longitudinal and lateral velocities for each wheel Vx;

and calculating the sideslip angle α

_i and slip rate s_i for each wheel.

11. The vehicle anti-skid brake control method of claim 10, wherein said step 1′

that is used to calculate the sideslip angle α

_i and slip rates_i for each wheel comprises;

A. said electronic control unit calculating the estimated sideslip angle β

^GPS and yaw rate r at the centroid with a yaw Kalman filter from said V_cg^GPS and angular speed;

B. said electronic control unit calculating the GPS measured values of longitudinal and lateral velocities V_x^GPS and V_y^GPS at the centroid of the vehicle according to the equations (1) and (2);

V_x^GPS=V_cg^GPS cos(β

^GPS) 

 

(1)

V_y^GPS=V_cg^GPS sin(β

^GPS) 

 

(2)

C. said electronic control unit calculating the estimated longitudinal and lateral velocities V_x and V_y with a Kalman filter for speed from said V_x^GPS, V_y^GPS, and the acceleration;

D. said electronic control unit calculating the longitudinal velocity V_ix and lateral velocity V_iy at the center of each wheel from said V_x, V_y, and the steering wheel angle according to the following equations (3)-(10), wherein, i=1, 2, 3, or 4;

V_1x=V_x+r(d₂+e cos(δ

)) 

 

(3)

V_1y=V_y+r(l_f+e sin(δ

)) 

 

(4)

V_2x=V_x−

r(d₂−

e cos(δ

)) 

 

(5)

V_2y=V_y+r(l_f−

e sin(δ

)) 

 

(6)

V_3x=V_x+r(d₂+e) 

 

(7)

V_3y=V_y+rl_r 

 

(8)

V_4x=V_x−

r(d₂+e) 

 

(9)

V_4v=V_y−

rl_r 

 

(10);

wherein, δ

is the steering angle of wheel, e is the distance from the steering knuckle spindle to the tire tread centre;

d₂ is the lateral distance from the centroid to the steering knuckle; and

l_f and l_r are the distance from the centroid to the front axle and the distance from centroid to rear axle, respectively;

E. said electronic control unit calculating the sideslip angle α

_i for each wheel according to the following equations (11)-(14);

$\begin{array}{cc}{\mathrm{\alpha <br><br>}}_1=\mathrm{\delta <br><br>}-\arctan <br><br>\frac{V_{1<br><br><br><br>y}}{V_{1<br><br><br><br>x}}& \left(11\right)\\ {\mathrm{\alpha <br><br>}}_2=\mathrm{\delta <br><br>}-\arctan <br><br>\frac{V_{2<br><br><br><br>y}}{V_{2<br><br><br><br>x}}& \left(12\right)\\ {\mathrm{\alpha <br><br>}}_3=\arctan <br><br>\frac{V_{3<br><br><br><br>y}}{V_{3<br><br><br><br>x}}& \left(13\right)\\ {\mathrm{\alpha <br><br>}}_4=\arctan <br><br>\frac{V_{4<br><br><br><br>y}}{V_{4<br><br><br><br>x}}& \left(14\right)\end{array}$

F. said electronic control unit calculating the slip rate s_i for each wheel from said longitudinal velocity V_ix, lateral velocity V_iy, wheel rolling radius r_w, and wheel rotation speed ω

_i of the i^th wheel according to the equation (15).

$\begin{array}{cc}{s}_i=\frac{\sqrt{V_{\mathrm{ix}}^2+V_{\mathrm{iy}}^2}<br><br>\cos <br><br>\left({\mathrm{\alpha <br><br>}}_i\right)-r_w<br><br>{\mathrm{\omega <br><br>}}_i}{\sqrt{V_{\mathrm{ix}}^2+V_{\mathrm{iy}}^2}<br><br>\cos <br><br>\left({\mathrm{\alpha <br><br>}}_i\right)}& \left(15\right)\end{array}$

12. The vehicle anti-lock brake control method of claim 9, wherein, in step 3′

, utilizing a look-up table method and/or an interpolation method to set the respective lower limit s^min and upper limit s^max of different slip rate thresholds at different sideslip angles.

13. The vehicle anti-skid brake control method of claim 9, wherein said step 4′

comprises;

judging whether the slip rate s_i of the wheel is within the slip rate threshold, if the slip rate s_i meets s^min<

S_i<

s^max, said data control module will output a control command that keeps the wheel braking force unchanged;

if the slip rate S_i is larger than s^max, said data control module will output a control command that decreases the wheel braking force; and

if the slip rate S_i is smaller than s^min, said data control module will output a control command that increases the wheel braking force.