Method of navigating an agricultural vehicle, and an agricultural vehicle implementing the same

1. A method of navigating an agricultural vehicle, comprising the steps of:

equipping the vehicle with a 3D imaging device for imaging surroundings of the vehicle, and with an image processing device;

obtaining from the 3D imaging device frames imaging at least a part of the surrounding of the vehicle at different points of time while the vehicle is moving thus providing a chronological sequence of frames;

analyzing the frames;

establishing a change of pose of the vehicle using results of the analysis of at least two chronologically different frames;

estimating a slip angle, wherein the vehicle comprises a steering angle gauge for measuring an angle of steering wheels of the agricultural vehicle; and

comparing a change of pose and the angle of the steering wheels of the agricultural vehicle.

2. The method as defined in claim 1 , further comprising equipping the vehicle with at least one further navigation sensor; and using a response from the at least one further navigation sensor when establishing the change of pose.

3. The method as defined in claim 2 , further comprising selecting the at least one further navigation sensor from a group consisting of a GPS sensor, an inertial measuring unit, a steering angle gauge indicating an angle of steering wheels of the agricultural vehicle, and a wheel revolution indicator.

4. The method of defined in claim 1 , further comprising performing in the analysis of the frames establishing of distinct features in the frames, establishing of 3D information about the distinctive features found in the frames, matching distinct features found in one frame with distinct features found in a second earlier frame; establishing a change of pose between the one frame and the second frame on basis of respective positions of matched distinctive features in the two frames.

5. The method as defined in claim 4 , further comprising comparing the change of pose to a predetermined change of pose, and rejecting the one frame if the change of pose is smaller than the predetermined change of pose.

6. The method as defined in claim 4 , further comprising, in the matching of a distinctive feature found in a second frame with a distinct feature found in the one frame, including establishing a search area in the second frame within which the distinct feature is suspected to be found based on knowledge of a current movement of the vehicle.

7. The method as defined in claim 6 , further comprising providing the establishing of the knowledge of the current movement of the vehicle on basis of information from at least one further navigation sensor.

8. The method as defined in claim 4 , further comprising tracking information about distinct features in a non-rejected frame in stored, distinct features found in one frame and matched with distinct features in a second frame, back in a chronological sequence of frames; and taking into account changes of pose between different frames, in which such distinctive features are tracked, for establishing a change of pose through the chronological sequence.

9. The method as defined in claim 8 , wherein said tracking the changes of pose includes tracking the changes of pose between different, chronologically adjacent frames.

10. The method as defined in claim 8 , further comprising tracking back the distinct features found in one frame and matched with distinct features in a second image frame as far as possible in the chronological sequence of frames.

11. The method as defined in claim 8 , further comprising rejecting from the chronologic sequence frames in the chronological sequence, in which distinctive features of the one frame are not tracked.

12. The method as defined in claim 8 , further comprising establishing an estimate of a current pose of the vehicle on basis of a pose of the vehicle at the time of eldest frame in the chronological sequence in which distinctive features of the one frame are tracked and the change of pose between the eldest frame and the one frame.

13. The method as defined in claim 1 , further comprising sensing a global direction of travel of the vehicle by a global direction sensing device provided in the vehicle; and comparing the change of pose of the vehicle with the global direction of travel of the vehicle.

14. The method as defined in claim 1 , further comprising comparing a speed of the vehicle indicated by a wheel revolution indicator attached to driving wheels of the vehicle, with the change of pose of the vehicle.

15. The method as defined in claim 1 , further comprising currently establishing the change of pose of a specific location on the vehicle.

16. An agricultural vehicle, comprising a 3D imaging device; a computer system including an image processing device; at least one navigation sensor; and a computer-readable medium having stored thereon a set of instructions, which when run by a computer system causes the computer system to perform the method of claim 1 .

17. An agricultural vehicle as defined in claim 16 , wherein said at least one navigation sensor is a sensor selected from the group consisting of a GPS sensor, an internal measuring unit, a steering angle gauge for measuring an angle of steering wheels of the agricultural vehicle, and the wheel revolution indicator.

18. The method as defined in claim 1 , wherein the agricultural vehicle is the vehicle selected from the group consisting of a tractor and an automotive agricultural implement.

19. The method as defined in claim 18 , wherein said automotive agricultural implement is an implement selected from a group consisting of a harvester and a baler.