Method for estimation of a trailer wheelbase length

1. A method for estimating an effective wheelbase length of a trailer in a vehicle combination comprising a towing vehicle and at least one towed trailer, comprising:

driving the vehicle combination forwards,

recording the speed of the vehicle combination,

recording the steering angle of the towing vehicle,

recording the yaw rate of the towing vehicle and of the towed trailers,

determining the yaw rate of the towed trailers using the recorded yaw rate of the towing vehicle and adding a time derivative of an articulation angle between the towing vehicle and the towed trailers,

recording the steering angle of each towed trailer,

using the recorded values and the determined yaw rate to calculate a value for the effective wheelbase for each towed trailer, and

using the calculated value of the effective wheelbase for each towed trailer to perform one or more autonomous or semi-automatic driving functions.

2. Method according to claim 1 , wherein both the yaw rate of the towing vehicle and the towed trailers and the articulation angle for each towed trailer is also recorded.

3. Method according to claim 1 , wherein the recorded values are arranged in a data set.

4. Method according to claim 1 , wherein a plurality of data sets are recorded.

5. Method according to claim 1 , wherein the calculation of the effective wheelbase is done by using a least square fit to a one track linear vehicle model.

6. Method according to claim 5 , wherein a plurality of effective wheelbase values are calculated, and that a mean value of the calculated values are used as the effective wheelbase value.

7. Method according to claim 1 , wherein the method is repeated every time the ignition of the vehicle is turned on.

8. Method according to claim 1 , wherein the method is repeated every time the load of a trailer has changed by a predetermined amount.

9. A computer programmed for performing all the steps of claim 1 .

10. A computer program product comprising a program stored on a non-transitory computer readable medium for performing all the steps of claim 1 when the program product is run on a computer.

11. A vehicle combination, comprising

a towing vehicle and at least one towed trailer,

an autonomous or semi-automatic driving system for the towing vehicle; and

an arrangement for estimating an effective wheelbase length of the trailer, where the arrangement comprises

means for obtaining the speed of the vehicle combination,

means for obtaining the steering angle of the towing vehicle,

means for obtaining the steering angle of each towed trailer,

wherein the arrangement further comprises

means for obtaining the yaw rate of the towing vehicle and each towed trailer, the yaw rate of the towed trailers being obtained using the obtained yaw rate of the towing vehicle and adding a time derivative of an articulation angle between the towing vehicle and the towed trailers, and

means for calculating a value for the effective wheelbase for each towed trailer using the obtained values,

wherein the autonomous or semi-automatic driving system is arranged to use the calculated value of the effective wheelbase for each towed trailer to perform one or more autonomous or semi-automatic driving functions.

12. The vehicle according to claim 11 , wherein the arrangement comprises means for obtaining both the yaw rate of the towing vehicle and the towed trailers and the articulation angle for each towed trailer.

13. The vehicle according to claim 11 , wherein the means for calculating a value for the effective wheelbase uses a least square fit to a one track linear vehicle model.

14. A method for estimating an effective wheelbase length of a trailer in a vehicle combination comprising a towing vehicle and at least one towed trailer, comprising:

driving the vehicle combination forwards,

recording the speed of the vehicle combination,

recording the steering angle of the towing vehicle,

recording the yaw rate of the towing vehicle,

recording an articulation angle for each towed trailer, wherein the articulation angle for each towed trailer is an angle between a longitudinal center-line of the trailer and a longitudinal center-line of the towing vehicle,

determining the yaw rate of the towed trailers using the recorded yaw rate of the towing vehicle and adding a time derivative of the articulation angle between the towing vehicle and the towed trailers,

recording the steering angle of each towed trailer,

using the recorded values and the determined yaw rate to calculate a value for the effective wheelbase for each towed trailer, and

using the calculated value of the effective wheelbase for each towed trailer to perform one or more autonomous or semi-automatic driving functions.