Navigation System and Method for Autonomous Mower

• US 20140012453A1
• Filed: 07/09/2012
• Published: 01/09/2014
• Est. Priority Date: 07/09/2012
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Johnson, David August, Das, Colin Eric
• Granted Patent: US 9,026,299 B2
• Time in Patent Office: Days
• US Class Current: 701/23
• CPC Class Codes: G05D 1/0219 ensuring the processing of the whole working surface
• CPC Class Codes: G05D 1/0265 using buried wires

Abstract

A navigation system for a robotic mower includes a boundary wire defining a boundary of a specified area; a boundary sensor assembly, and a vehicle control unit with a navigation arbitration logic configured to arbitrate a selection between at least a straight propagation mode and an arc propagation mode. The navigation arbitration module is configured to select the arc propagation mode when the sensor assembly indicates that the mower approaches the boundary of the specified area and has a distance from the boundary that is equal to or smaller than a specified turn distance. The boundary sensor assembly generates a sensor signal representative of a measured yaw angle of the mower relative to the boundary wire, and the navigation arbitration logic is configured to generate output information representative of a desired yaw angle dependent on an assumed actual yaw angle.

Claims

1. A vehicle control unit for a robotic mower, the vehicle control unit comprising a navigation arbitration logic configured to arbitrate a selection between at least a first propagation mode and a second propagation mode, the first propagation mode being a mode of straight propagation of the mower and the second propagation mode being a mode of arc-shaped propagation of the mower, the navigation arbitration module being configured to select the second propagation mode when receiving sensor information indicating that the mower approaches a boundary of a specified area and has a distance from the boundary that is equal to or smaller than a specified turn distance.

2. The vehicle control unit of claim 1, wherein the vehicle control unit is configured to receive sensor information representative of a measured yaw angle of the mower relative to the boundary.

3. The vehicle control unit of claim 2, wherein the navigation arbitration logic is configured to generate output information representative of a desired yaw angle, the desired yaw angle being dependent on an assumed actual yaw angle being one of an estimated yaw angle and the measured yaw angle.

4. The vehicle control unit of claim 3, wherein in the first propagation mode the desired yaw angle relative to the boundary is equal to the measured yaw angle.

5. The vehicle control unit of claim 3, wherein in the second propagation mode the desired yaw angle represents a mirror reflection of the measured yaw angle on a vertical plane extending along the boundary.

6. The vehicle control unit of claim 3, further comprising an actuator module configured to convert the desired yaw angle into a yaw angle difference between the desired yaw angle and the assumed actual yaw angle.

7. The vehicle control unit of claim 1, wherein the vehicle control unit is configured to receive sensor information representative of a measured distance of the mower relative from the boundary and wherein the navigation arbitration logic is configured to generate output information representative of a desired speed vector in the second propagation mode, the desired speed vector being dependent on the measured distance.

8. The vehicle control unit of claim 7, wherein a speed component of the desired speed vector perpendicular to the boundary is positively correlated to the measured distance from the boundary.

9. The vehicle control unit of claim 7, wherein the magnitude of the desired speed vector is positively correlated to the measured distance from the boundary.

10. The vehicle control unit of claim 1, wherein the control unit is configured to generate input quantities for a mower propulsion system to cause a desired behavior based on the selection of the first propagation mode or the second propagation mode.

11. The vehicle control unit of claim 1, wherein the control unit is configured to generate input quantities for a mower blade motor system to cause a desired rotational blade speed based on the selection of the first propagation mode or the second propagation mode.

12. The vehicle control unit of claim 1, wherein the navigation arbitration logic is configured to generate output information representative of a desired speed vector, the desired speed vector having a greater magnitude in the first propagation mode than in the second propagation mode.

13. The vehicle control unit of claim 1, further comprising a positioning module configured to calculate an absolute current position of the mower within the specified area.

14. The vehicle control unit of claim 1, where the navigation arbitration module is configured to select the first propagation mode when the distance to the boundary is greater than the specified turn distance or the mower is moving away or parallel to the boundary wire.

15. A navigation system for a robotic mower, the navigation system comprising:

a boundary wire defining a boundary of a specified area, a boundary sensor assembly, and a vehicle control unit including a navigation arbitration logic configured to arbitrate a selection between at least a first propagation mode and a second propagation mode, the first propagation mode being a mode of straight propagation of the mower and the second propagation mode being a mode of arc-shaped propagation of the mower, the navigation arbitration module being configured to select the second propagation mode when the sensor assembly indicates that the mower approaches the boundary of the specified area and has a distance from the boundary that is equal to or smaller than a specified turn distance.

16. The navigation system of claim 15, wherein the boundary sensor assembly generates a sensor signal representative of a measured yaw angle of the mower relative to the boundary wire.

17. The navigation system of claim 16, wherein the navigation arbitration logic is configured to generate output information representative of a desired yaw angle, the desired yaw angle being dependent on an assumed actual yaw angle being one of an estimated yaw angle and the measured yaw angle.

18. The navigation system of claim 16, wherein in the first propagation mode the desired yaw angle relative to the boundary wire is equal to the measured yaw angle.

20. The navigation system of claim 17, further comprising an actuator module configured to convert the desired yaw angle into a yaw angle difference between the desired yaw angle and the assumed actual yaw angle.

21. The navigation system of claim 15, wherein the boundary sensor assembly generates a sensor signal representative of a measured distance of the mower relative from the boundary wire and wherein the navigation arbitration logic is configured to generate output information representative of a desired speed vector in the second propagation mode, the desired speed vector being dependent on the measured distance.

22. The navigation system of claim 21, wherein a speed component of the desired speed vector perpendicular to the boundary wire is positively correlated to the measured distance from the boundary wire.

23. The navigation system of claim 21, wherein the magnitude of the desired speed vector is positively correlated to the measured distance from the boundary wire.

24. The navigation system of claim 17, wherein the control unit is configured to generate input quantities for a mower propulsion system to cause a desired behavior based on the selection of the first propagation mode or the second propagation mode.

25. The navigation system of claim 15, wherein the control unit is configured to generate input quantities for a mower blade motor system to cause a desired rotational blade speed based on the selection of the first propagation mode or the second propagation mode.

26. The navigation system of claim 15, wherein the navigation arbitration logic is configured to generate output information representative of a desired speed vector, the desired speed vector having a greater magnitude in the first propagation mode than in the second propagation mode.

27. The navigation system of claim 15, further comprising a positioning module configured to calculate an absolute current position of the mower within the specified area.

28. The navigation system of claim 15, where the navigation arbitration module is configured to select the first propagation mode when the distance to the boundary is greater than the specified turn distance or the mower is moving away or parallel to the boundary wire.

19. The navigation system of claim 19, wherein in the second propagation mode the desired yaw angle represents a mirror reflection of the measured yaw angle on a vertical plane extending along the boundary wire.

29. A method of navigating a robotic mower, the method comprising the steps of

receiving sensor information representative of a measured distance from a boundary of a specified area and a measured yaw angle relative to the boundary;

and

arbitrating a selection between at least a first propagation mode and a second propagation mode, the first propagation mode being a mode of straight propagation of the mower and the second propagation mode being a mode of arc-shaped propagation of the mower;

wherein the second propagation mode is selected when receiving sensor information indicating that the mower approaches the boundary of the specified area and that the distance from the boundary is equal to or smaller than a specified turn distance.

30. The method of claim 29, wherein the navigation arbitration logic is configured to generate output information representative of a desired yaw angle, the desired yaw angle being dependent on an assumed actual yaw angle being one of an estimated yaw angle and the measured yaw angle.

31. The method of claim 30, wherein in the first propagation mode the desired yaw angle relative to the boundary wire is equal to the measured yaw angle.

32. The method of claim 30, wherein in the second propagation mode the desired yaw angle represents a mirror reflection of the measured yaw angle on a vertical plane extending along the boundary wire.

33. The method of claim 30, further comprising the step of converting the desired yaw angle into a yaw angle difference between the desired yaw angle and the assumed actual yaw angle.

34. The method of claim 29, further comprising the step of generating output information representative of a desired speed vector in the second propagation mode, the desired speed vector being dependent on the measured distance.

35. The method of claim 34, wherein a speed component of the desired speed vector perpendicular to the boundary is positively correlated to the measured distance from the boundary.

36. The method of claim 34, wherein the magnitude of the desired speed vector is positively correlated to the measured distance from the boundary.

37. The method of claim 29, further comprising the step of generating input quantities for a mower propulsion system to cause a desired behavior based on the selection of the first propagation mode or the second propagation mode.

38. The method of claim 29, further comprising the step of generating input quantities for a mower blade motor system to cause a desired rotational blade speed based on the selection of the first propagation mode or the second propagation mode.

39. The method of claim 29, further comprising the step of generating output information representative of a desired speed vector, the desired speed vector having a greater magnitude in the first propagation mode than in the second propagation mode.

40. The method of claim 29, further comprising the step of calculating an absolute current position of the mower within the specified area.

41. The method of claim 29, where the first propagation mode is selected when the distance to the boundary is greater than the specified turn distance or the mower is moving away or parallel to the boundary wire.