Offset calibration of a semi-relative steering wheel angle sensor

• US 20040061500A1
• Filed: 09/30/2002
• Published: 04/01/2004
• Est. Priority Date: 09/30/2002
• Status: Active Grant

• Current Assignee: Continental Teves Incorporated (Continental AG)
• Original Assignee: Continental Teves Incorporated (Continental AG)
• Inventors: Olejnik, Peter, Baker, Paul, Lou, Yongle, Glover, Michael C., Endress, Ralf
• Granted Patent: US 6,895,357 B2
• Time in Patent Office: Days
• US Class Current: 324/332
• CPC Class Codes: B60T 2250/06 Sensor zero-point adjustment; Offset compensation
• CPC Class Codes: B62D 15/0245 Means or methods for determination of the central position of the steering system, e.g. straight ahead position

Abstract

A new method for determining an actual steering wheel angle is provided that does not require re-calculation of a steering center upon each ignition of the vehicle. Accordingly, the vehicle dynamic controller may be activated very quickly after ignition, while a less costly relative steering wheel angle sensor may be employed.

Claims

1. A method for determining an actual steering wheel angle θ

of a vehicle steering mechanism, the vehicle steering mechanism having an initial steering wheel angle θ

_i when the vehicle enters an ignition-on state, the vehicle steering mechanism having a center steering wheel angle θ

₀ when the vehicle is heading straight-forward, the method comprising the steps of;

determining a semi-relative steering wheel angle offset Δ

θ

representing the difference between θ

_i and θ

₀;

storing Δ

θ

in erasable programmable read-only memory when said vehicle enters an ignition-off state;

measuring a relative steering wheel angle θ

_R from a semi-relative steering wheel angle sensor during the ignition-off state;

retrieving Δ

θ

from the erasable programmable read-only memory when said vehicle enters an ignition-on state;

continuing to measure the relative steering wheel angle θ

_R from the semi-relative steering wheel angle sensor during the ignition-on state; and

determining said steering wheel angle θ

based on θ

_R and Δ

θ

.

2. The method of claim 1, further comprising the step of detecting if power to the semi-relative steering wheel angle sensor was terminated.

3. The method of claim 2, further comprising the step of re-determining an initial semi-relative steering wheel angle offset Δ

θ

when it is detected that power to the semi-relative steering wheel angle sensor was terminated.

4. The method of claim 1, said vehicle including a sensor cluster including a yaw rate sensor, further comprising the step of determining if a failure has occurred with the sensor cluster.

5. The method of claim 4, further comprising the step of re-determining an initial semi-relative steering wheel angle offset Δ

θ

when it is detected that a failure has occurred with the sensor cluster.

6. The method of claim 1, wherein the semi-relative steering wheel angle sensor is powered independently from the vehicle ignition.

7. The method of claim 1, wherein θ

=θ

_R−

Δ

θ

.

8. A method for determining an actual steering wheel angle θ

of a steering mechanism in a vehicle, the vehicle including an electrical control unit in communication with a calibration module, a sensor module and an erasable programmable read-only memory, the calibration module including a semi-relative steering wheel angle sensor reading the relative movement of the steering mechanism, the sensor module including a yaw rate sensor, the method comprising the steps of;

reading a last known semi-relative steering wheel angle offset value Δ

θ

(t_n) from the erasable programmable read-only memory to the electrical control unit;

determining whether power to the calibration module has been terminated;

determining whether a failure has occurred with the sensor module, and

setting the last known semi-relative steering wheel angle offset value Δ

θ

(t_n) as an initial semi-relative steering wheel angle offset value Δ

θ

(t₀) if power to the calibration module was not terminated and no failure occurred with the sensor module.

9. The method of claim 8, further comprising the step of activating a vehicle dynamic controller when the initial semi-relative steering wheel angle offset value Δ

θ

(t₀) has been determined.

10. The method of claim 9, further comprising the step of measuring a semi-relative steering wheel angle θ

_R from said semi-relative steering wheel angle sensor.

11. The method of claim 8, further comprising the step of calculating an initial semi-relative steering wheel angle offset value Δ

θ

(t₀) if power to the calibration module was terminated or if a failure occurred with the sensor module.

12. The method of claim 11, wherein the step of calculating Δ

θ

(t₀) includes the steps of;

measuring a relative steering wheel angle θ

_R from a semi-relative steering wheel angle sensor;

identifying a center steering wheel angle θ

₀ of the steering mechanism representing the vehicle being headed straight-forward and stable; and

setting Δ

θ

(t₀)=θ

_R when the steering mechanism has been identified as being at θ

₀.

13. The method of claim 12, wherein the vehicle being headed straight-forward is determined only when the CAN BUS is functional, the YRS signal is valid, and the Semi-RSAS signal is valid.

14. The method of claim 12, wherein the vehicle being stable is determined by calculating the amplitudes of predetermined vehicle natural frequencies using an on-line frequency detection method.

15. The method of claim 8, further comprising the steps of:

determining whether communication between the electrical control unit and the sensor module is functional; and

determining whether communication between the electrical control unit and the calibration module is functional.

16. The method of claim 9, further comprising the step of determining whether the calibration module outputs valid data.

17. A method for determining a steering wheel angle θ

of a steering mechanism for a vehicle, the method comprising the steps of;

measuring a relative steering wheel angle θ

_R from a semi-relative steering wheel angle sensor during both ignition-off and ignition-on states of said vehicle;

retrieving a semi-relative steering wheel angle offset Δ

θ

from the erasable programmable read-only memory when said vehicle enters an ignition-on state; and

determining said steering wheel angle θ

based on θ

_R and Δ

θ

.

18. The method of claim 17, further comprising the step of storing the semi-relative steering wheel angle offset Δ

θ

to erasable programmable read-only memory when said vehicle enters an ignition-off state.

19. The method of claim 17, said vehicle including a sensor cluster including a yaw rate sensor, further comprising the steps of re-determining Δ

θ

if the semi-relative steering wheel angle sensor looses power or a failure occurs with the sensor cluster.

20. The method of claim 17, further comprising the step of powering the semi-relative steering wheel angle sensor independently from the vehicle ignition.