Method for determining the steering ratio of a vehicle

1. A method for determining the steering ratio of a vehicle, comprising the steps of determining whether a stable travel condition of a vehicle exists, when said stable travel condition exists, obtaining vehicle parameter information, obtaining sensed measured values associated with said vehicle, and calculating a steering ratio of said vehicle based on said vehicle parameter information and said sensed measured values.

2. The method according to claim 1 , wherein said sensed measured values include a yaw rate, a steering wheel angle and speed of said vehicle.

3. The method according to claim 2 , wherein said yaw rate is measured by means of a yaw rate sensor, and said steering wheel angle is measured by means of a steering wheel angle sensor.

4. The method according to claim 2 , wherein yaw rates are obtained for a plurality of steering wheel angle grid points.

5. The method according to claim 4 , wherein an entire range of said steering wheel angle is divided into a plurality of sub-ranges, each of said sub-ranges including at least one of said grid points.

6. The method according to claim 4 , wherein values between said grid points are determined by interpolation.

7. The method according to claim 4 , wherein at least two grid points are determined at the end of vehicle production.

8. The method according to claim 4 , wherein said steering ratio is determined for each of said grid points.

9. The method according to claim 8 , wherein a data matrix describing steering ratio variation is generated based on said steering ratio for each of said grid points.

10. The method according to claim 2 , wherein at least one of said yaw rate, said steering wheel angle and a lateral acceleration of said vehicle is compensated for zero-point drift.

11. The method according to claim 10 , wherein said compensation for zero-point drift is based on average values of said at least one of said yaw rate, said steering wheel angle and said lateral acceleration of said vehicle.

12. The method according to claim 11 , wherein said average values are at least one of vehicle travel distance dependent and time dependent.

13. The method according to claim 10 , wherein said yaw rate is measured by means of a yaw rate sensor, and said measured yaw rate is used as a base variable for said compensation for zero-point drift.

14. The method according to claim 13 , wherein said base variable is determined during at least one of standstill and travel of said vehicle.

15. The method according to claim 13 , wherein at least one of said steering wheel angle and said lateral acceleration is compensated for as a function of said base variable and as a function of at least one of vehicle travel distance and a time interval.

16. The method according to claim 1 , wherein said vehicle parameter information includes at least one of a self-steering gradient, a wheelbase and dimensions of said vehicle.

17. The method according to claim 16 , wherein said vehicle parameter information is obtained via at least one of a vehicle data bus, vehicle electronic systems and data memories.

18. The method according to claim 1 , further comprising the step of generating a warning signal when said step of calculating said steering ratio is not complete.

19. A method for determining the steering ratio of a vehicle, comprising the steps of determining whether a stable travel condition of a vehicle exists, when said stable travel condition exists, obtaining vehicle parameter information, obtaining sensed measured values associated with said vehicle, and calculating a steering ratio i s of said vehicle based on said vehicle parameter information and said sensed measured values according to the relationship:

i

s

=

δ

H

ψ

(

l

v

+

EG

*

v

)

where:

ψ: yaw rate

δ H : steering wheel angle

EG: self-steering gradient

v: vehicle speed

l: wheelbase.