Boundary Sensor Assembly for a Robotic Lawn Mower, Robotic Lawn Mower and Robotic Lawn Mower System

• US 20140012418A1
• 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, Cross, Patrick Wilson, Das, Colin Eric
• Granted Patent: US 9,072,218 B2
• Time in Patent Office: Days
• US Class Current: 700/258
• CPC Class Codes: A01D 34/00 Mowers combined with apparatus performing additional operations while mowing A01D37/00 - A01D41/00, A01D43/00; convertible to apparatus for purposes other than mowing or capable of performing operations other than mowing A01D42/00; Mowing apparatus of harvesters
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: A47L 2201/04 Automatic control of the travelling movement; Automatic obstacle detection
• CPC Class Codes: B25J 9/0003 Home robots, i.e. small robots for domestic use
• CPC Class Codes: G05D 1/0265 using buried wires

Abstract

A robotic mower sensor assembly for detecting a boundary wire signal. The sensor assembly includes a plurality of analog inductive sensors with a first inductive sensor oriented along a first axis and a second inductive sensor oriented along a second, different axis. Each inductive sensor is configured to generate a signal indicative of the distance of the robotic mower from the boundary wire. A control unit communicating with the sensor assembly is configured to operate the robotic mower in response to the signals from the sensor assembly which are indicative of the distance of the robotic mower from the boundary wire.

Claims

1. A sensor assembly for detecting a boundary wire signal, the sensor assembly comprising:

a plurality of inductive sensors, the plurality of inductive sensors including at least a first inductive sensor and a second inductive sensor, the first inductive sensor oriented along a first axis, the second inductive sensor oriented along a second axis, the first and second axes being arranged at a non-zero angle relative to each other.

2. The sensor assembly of claim 1, wherein each inductive sensor of the plurality of inductive sensors is an analog sensor configured to generate a signal indicative of the distance of the sensor assembly from the boundary wire.

3. The sensor assembly of claim 2, wherein the signals generated by the plurality of inductive sensors have amplitudes with a ratio with respect to each other that is indicative of an angular position of the sensor assembly relative to the boundary wire.

4. The sensor assembly of claim 1, wherein the first axis has at least a vertical component and the second axis has at least a horizontal component.

5. The sensor assembly of claim 1, wherein the first and second axes are perpendicular to each other.

6. The sensor assembly of claim 1, wherein the plurality of inductive sensors comprises a third sensor oriented along a third axis, the third axis forming non-zero angles with both the first axis and the second axis.

7. The sensor assembly of claim 6, wherein no more than two of the first axis, the second axis and the third axis are coplanar.

8. The sensor assembly of claim 7, wherein the first axis, the second axis and the third axis are all generally perpendicular to one another.

9. The sensor assembly of claim 6, wherein the plurality of sensors further comprises a fourth sensor oriented along a fourth axis, the fourth axis forming non-zero angles with each of the first axis, the second axis and the third axis.

10. The sensor assembly of claim 9, wherein no more than three of the first axis, the second axis, the third axis and the fourth axis are coplanar.

11. The sensor assembly of claim 10, wherein no more than two of the first axis, the second axis, the third axis and the fourth axis are coplanar.

12. The sensor assembly of claim 11, wherein the first axis, the second axis and the third axis are all perpendicular to each other as represented by unit vectors [1,0,0], [0,1,0] and [0,0,1] in a Cartesian coordinate system, and the fourth axis extends diagonally as represented by a vector [1,1,1].

13. The sensor assembly of claim 1, wherein each inductive sensor of the plurality of inductive sensors comprises a pickup coil.

14. A robotic mower for mowing an area relative to a boundary wire, the robotic mower comprising:

a cutting system including an element for cutting grass;

a propulsion system including a motor for propelling the robotic mower;

a sensor assembly configured to detect a distance from the boundary wire, the sensor assembly having a plurality of inductive sensors, the plurality of inductive sensors including at least a first inductive sensor and a second inductive sensor, the first inductive sensor oriented along a first axis, the second inductive sensor oriented along a second axis, the first and second axes being arranged at a non-zero angle relative to each other; and

a control unit in communication with the cutting system, the propulsion system and the sensor assembly, wherein the control unit is configured to operate the cutting system and the propulsion system in response to receipt of a signal from the sensor assembly indicative of the distance of the robotic mower from the boundary wire.

15. The robotic mower of claim 14, wherein the first axis has at least a vertical component and the second axis has at least a horizontal component, and the first and second axes are perpendicular to each other.

16. The robotic mower of claim 14, wherein the plurality of inductive sensors comprises a third sensor being oriented along a third axis, the third axis forming non-zero angles with both the first axis and the second axis.

17. The robotic mower of claim 16, wherein no more than two of the first axis, the second axis and the third axis are coplanar, and the first axis, the second axis and the third axis are all generally perpendicular to one another.

18. The robotic mower of claim 16, wherein the control unit is configured to calculate an angular position from the signal from the sensor assembly.

19. The robotic mower of claim 14, wherein the control unit further comprises 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.

20. A robotic mower system comprising:

a boundary wire;

a boundary wire driving circuit configured to transmit a signal on the boundary wire;

a cutting system including an element for cutting grass;

a propulsion system including a motor for propelling the robotic mower;

a sensor assembly configured to detect the signal on the boundary wire, the sensor assembly having a plurality of inductive sensors, the plurality of inductive sensors including at least a first inductive sensor and a second inductive sensor, the first inductive sensor oriented along a first axis, the second inductive sensor oriented along a second axis, the first and second axes being arranged at a non-zero angle relative to each other; and

a control unit in communication with the cutting system, the propulsion system and the sensor assembly, wherein the control unit is configured to, in response to receipt of a signal from the sensor assembly, determine a distance of the robotic mower from the boundary wire and operate the cutting system and the propulsion system based on the determined distance.

21. The robotic mower system of claim 20, wherein the first axis has at least a vertical component and the second axis has at least a horizontal component, and the first and second axes are perpendicular to each other.

22. The robotic mower system of claim 20, wherein the plurality of inductive sensors comprises a third sensor being oriented along a third axis, the third axis forming non-zero angles with both the first axis and the second axis.

23. The robotic mower system of claim 22, wherein no more than two of the first axis, the second axis and the third axis are coplanar, and the first axis, the second axis and the third axis are all generally perpendicular to one another.

24. A control unit for controlling a robotic mower, the control unit configured to operate a cutting system and a propulsion system in response to receipt of at least one signal from a sensor assembly with a plurality of sensors arranged along at least two axes arranged at a non-zero angle relative to each other, the at least one signal being indicative of a distance of the robotic mower from a boundary wire.

25. The control unit of claim 24, wherein the control unit is configured to calculate an angular position from the at least one signal.

26. The control unit of claim 24, wherein the control unit is configured to generate input quantities for the propulsion system to cause a desired behavior based on calculated coordinates calculated from the at least one signal.

27. The control unit of claim 24, further 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.