System and method for estimating an articulation angle of an articulated vehicle combination

1. A system for estimating an articulation angle between a first and a second connected vehicle section of an articulated vehicle combination, the system comprising:

a primary image obtaining device configured to be mounted on a first position of one of the vehicle sections and to obtain images of the other vehicle section during use;

a secondary image obtaining device configured to be mounted on a second position of one of the vehicle sections and to obtain images of the other vehicle section during use, the second position being different from the first position, and/or a mounting orientation at the second position of the secondary image obtaining device being different from a mounting orientation at the first position of the primary image obtaining device; and

wherein the system is configured to:

estimate the articulation angle by use of at least one obtained image from the primary image obtaining device;

determine if an unreliability condition has been fulfilled which indicates that the articulation angle cannot be reliably estimated from the at least one obtained image from the primary image obtaining device; and

when the unreliability condition has been fulfilled, the system is further configured to:

estimate the articulation angle by use of at least one obtained image from the secondary image obtaining device.

2. The system according to claim 1 , wherein the primary image obtaining device is an optical image obtaining device, such as a camera or a LIDAR, wherein the unreliability condition is a condition considered fulfilled when a light intensity in the obtained images of the primary image obtaining device is outside a predetermined light intensity range.

3. The system according to claim 2 , wherein the predetermined light intensity range is defined by at least one of:

an upper limit associated with a too high light intensity, such as caused by direct or reflected sunlight and light from headlamps at night;

a lower limit associated with a too low light intensity, such as dark/night conditions and dirt and/or water splash on the primary image obtaining device.

4. The system according to claim 1 , wherein the articulation angle is estimated by determining a relative position and/or orientation of the first and second vehicle sections from the at least one obtained image.

5. The system according to claim 1 , wherein, when the unreliability condition is fulfilled, the articulation angle is estimated by determining an articulation angle change by use of the secondary image obtaining device and by using an absolute articulation angle estimated at least by use of the primary image obtaining device before the unreliability condition was fulfilled.

6. The system according to claim 5 , wherein the secondary image obtaining device is calibrated by use of the at least one obtained image from the primary image obtaining device.

7. The system according to claim 1 , wherein the secondary image obtaining device is any one of a camera, a LIDAR, a RADAR, an ultrasonic sensor and a SONAR.

8. The system according to claim 1 , wherein, when the unreliability condition is not fulfilled, the articulation angle is estimated by use of the primary and the secondary image obtaining devices.

9. A vehicle comprising at least parts of the system according to claim 1 , wherein at least the primary image obtaining device is preferably mounted on the vehicle.

10. The vehicle according to claim 9 , wherein the primary image obtaining device is mounted at a rearward facing side of the vehicle, such as on a rear side of a vehicle cabin or on a rearward facing side of a vehicle chassis, such as behind and/or below a vehicle coupling point.

11. The vehicle according to claim 9 , wherein the second position is any one of a position on a lateral side of the vehicle and on the rearward facing side of the vehicle.

12. An articulated vehicle combination comprising a first and a second vehicle section, wherein the first vehicle section is the vehicle according to claim 9 .

13. The articulated vehicle combination according to claim 12 , wherein the secondary image obtaining device is mounted on the second vehicle section.

14. A method for an articulated vehicle combination for estimating an articulation angle between a first and a second connected vehicle section of the articulated vehicle combination, wherein the articulated vehicle combination comprises:

a primary image obtaining device mounted on a first position of one of the vehicle sections;

a secondary image obtaining device mounted on a second position of one of the vehicle sections, the second position being different from the first position, and/or a mounting orientation at the second position of the secondary image obtaining device being different from a mounting orientation at the first position of the primary image obtaining device;

wherein the method comprises:

obtaining at least one image of the other vehicle section by the primary image obtaining device;

estimating the articulation angle by use of the at least one obtained image from the primary image obtaining device;

determining if an unreliability condition has been fulfilled which indicates that the articulation angle cannot be reliably estimated from the at least one obtained image from the primary image obtaining device; and

when the unreliability condition has been fulfilled, the method further comprises:

obtaining at least one image of the other vehicle section by the secondary image obtaining device; and

estimating the articulation angle by use of the at least one obtained image from the secondary image obtaining device.

15. A control unit for an articulated vehicle combination for estimating an articulation angle between a first and a second connected vehicle section of the articulated vehicle combination, wherein the control unit is configured to perform the method of claim 14 .