Process for improved determination of the ratio among the radii of the wheels of a vehicle

• US 6,644,105 B2
• Filed: 04/27/2001
• Issued: 11/11/2003
• Est. Priority Date: 05/17/2000
• Status: Active Grant

• Current Assignee: Wabco GmbH (Wabco Holdings Incorporated)
• Original Assignee: Wabco GmbH (Wabco Holdings Incorporated)
• Inventors: Michaelsen, Arne, Dieckmann, Thomas
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): FERGUSON SAMRETH, MARISSA LIANA
• Application Number:
  US09/844,039
• Publication Number:
  US 20010054310A1
• Time in Patent Office: 928 Days
• Field of Search: 731/46--468, 701/1, 701/2, 701/83, 701/70, 701/19, 701/38, 340/442, 340/444, 340/3
• US Class Current: 73/146
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00

Abstract

A process for determining the wheel radius ratios of a vehicle equipped with an anti-lock braking system uses the rotational speeds of the vehicle wheels to determine a vehicle drive slip value. This drive slip value and the driving force of the vehicle drive wheels are combined in a Kalman filter to compute the wheel radius ratio data. When traveling around curves, however, the drive slip value calculation can become inaccurate, thereby corrupting the computed wheel radius ratio data. To correct for this curve travel effect, the inventive process includes the yawing rate of the vehicle in its computations. As a result, the corrected wheel radius ratios can be more reliably used for detecting tire pressure problems.

Claims

1. A process for determining a wheel radius ration for a vehicle, including compensation for curve travel, comprising the following steps:

a) measuring a rotations-speed of each wheel of said vehicle,

b) calculating an angular velocity for each wheel of said vehicle, based on said rotational speed measurements,

c) measuring a vehicle movement signal,

d) calculating a yawing rate for said vehicle, based on said vehicle movement signal measurement,

e) calculating a drive slip for each side of said vehicle, based on corresponding said angular velocities and said yawing rate, wherein said drive slip calculation uses said yawing rate to compensate for curve travel effects, and

f) determining said wheel radius ratios, based on said calculated drive slip signal and said vehicle movement signal received from said vehicle.

2. The process of claim 1, wherein said vehicle movement signal is derived from a yawing rate sensor.

3. The process of claim 1, wherein said vehicle movement signal is derived from a steering angle sensor.

4. The process of claim 1, wherein said vehicle movement signal is derived from a transverse acceleration sensor.

5. The process of claim 1, wherein said wheel radius ratio of a front wheel and a rear wheel on the same side of said vehicle is determined by means of a Kalman filter.

6. The process of claim 1, wherein said calculation of said drive slip, with compensation for curve travel, is in accordance with the following equation:

$S_A=\frac{{\mathrm{\omega <br><br>}}_A}{{\mathrm{\omega <br><br>}}_A}·<br><br>\frac{r_A}{r_V}·<br><br>\sqrt{\frac{1}{1-\frac{L^2}{r_V^2}·<br><br>\frac{{\mathrm{\omega <br><br>}}_G^2}{{\mathrm{\omega <br><br>}}_V^2}}}-$

wherein S_A is the drive slip,

ω

_V and r_V are the angular velocity and radius, respectively, of a front wheel of said vehicle,

ω

_A and r_A are the angular velocity and radius, respectively, of a rear wheel of said vehicle,

L is the wheel base dimension of said vehicle, and

ω

_G is the yawing rate of said vehicle.

7. The process of claim 6, wherein said drive slip calculation can be corrected for a zero-slip portion of said rear wheels, in accordance with the following equation:

8. The process of claim 1, wherein a wheel radius ratio of the wheels on the front axle of said vehicle is calculated in accordance with the following equation:

$\frac{r_1}{r_2}=\frac{{\mathrm{\omega <br><br>}}_2}{{\mathrm{\omega <br><br>}}_1}·<br><br>\sqrt{1+\frac{{\mathrm{\omega <br><br>}}_G^2}{{\mathrm{\omega <br><br>}}_2^2}·<br><br>\frac{S}{r_2^2}·<br><br>\left(S+2·<br><br>\sqrt{\frac{{\mathrm{\omega <br><br>}}_2^2}{{\mathrm{\omega <br><br>}}_G^2}·<br><br>r_2^2-L^2}\right)}$

wherein r₁ and r₂ are the radii of the left and right wheels, respectively, on said front axle of said vehicle,

ω

₁ and ω

₂ are the angular velocities of said left and right wheels, respectively, on said front axle of said vehicle,

ω

_G is the yawing rate of said vehicle,

S is the wheel gauge of said vehicle, and

L is the wheel base dimension of said vehicle.

9. The process of claim 7, wherein a wheel radius ratio of the wheels on the rear axle of said vehicle is calculated in accordance with the following equation:

$\frac{r_3}{r_4}=\frac{{\mathrm{\omega <br><br>}}_4}{{\mathrm{\omega <br><br>}}_3}·<br><br>\left(1+\frac{{\mathrm{\omega <br><br>}}_G}{{\mathrm{\omega <br><br>}}_4}·<br><br>\frac{S}{r_4}·<br><br>\left(S_{4<br><br>\mathrm{corr}}+1\right)\right)·<br><br>\frac{1}{1-\frac{S_{3<br><br>\mathrm{corr}}-S_{4<br><br>\mathrm{corr}}}{S_{3<br><br>\mathrm{corr}}+1}}$

wherein r₃ and r₄ are the radii of the left and right wheels, respectively, on said rear axle of said vehicle,

ω

₃ and ω

₄ are the angular velocities of said left and right wheels, respectively, on said rear axle of said vehicle,

ω

_G is the yawing rate of said vehicle,

S_3corr and S_4corr are the corrected drive slip values of said left and right wheels, respectively, on said rear axle of said vehicle,

S is the wheel gauge of said vehicle, and

L is the wheel base dimension of said vehicle.

10. The process of claim 9, wherein said wheel radius ratios r₁/r₂, r₁/r₃, r₂/r₄, r₃/r₄ are monitored continuously, such that a change in said wheel radius ratios caused by a particular one of said wheels is indicative of an unacceptable tire pressure in said particular one of said wheels.

11. The process of claim 10, wherein said change in said wheel radius ratios must exceed a predetermined threshold level in order to indicate an unacceptable tire pressure.

12. The process of claim 11, wherein a warning signal is generated when said unacceptable tire pressure is detected.

13. The process of claim 1, wherein said calculation of said drive slip with compensation for both curve travel and slip angle, is in accordance with the following equation:

$S_A^{\mathrm{\prime <br><br>}}=\frac{r_A·<br><br>{\mathrm{\omega <br><br>}}_A·<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\alpha <br><br>}}_V}{r_V·<br><br>{\mathrm{\omega <br><br>}}_V·<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\arcsin <br><br>\left(\frac{L}{r_V}·<br><br>\frac{{\mathrm{\omega <br><br>}}_G}{{\mathrm{\omega <br><br>}}_V}·<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\alpha <br><br>}}_A·<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\alpha <br><br>}}_V\right)-{\mathrm{\alpha <br><br>}}_A\right)}-1$

wherein

S_A′

is the drive slip corrected for curve travel and slip angle,

ω

_V and r_V are the angular velocity and radius, respectively, of a front wheel of said vehicle,

ω

_A and r_A are the angular velocity and radius, respectively, of a rear wheel of said vehicle,

L is the wheel base dimension of said vehicle,

ω

_G is the yawing rate of said vehicle, and

α

_V and α

_A are the front and rear slip angles, respectively, of said wheels of said vehicle.