Boundary sensor assembly for a robotic lawn mower, robotic lawn mower and robotic lawn mower system

• US 9,072,218 B2
• Filed: 07/09/2012
• Issued: 07/07/2015
• 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
• Primary Examiner(s): HOLLOWAY, JASON R
• Application Number:
  US13/544,270
• Publication Number:
  US 20140012418A1
• Time in Patent Office: 1,093 Days
• Field of Search: 700/253, 700/258, 700/259, 701/23, 901/1
• US Class Current: 1/1
• 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 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 of sensitivity for detecting a first component of a magnetic field along the first axis of sensitivity, the second inductive sensor oriented along a second axis of sensitivity for detecting a second component of the magnetic field along the second axis of sensitivity, the first and second axes of sensitivity 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 generated in response to the plurality of inductive sensors detecting the signal on the boundary wire and indicative of the distance of the robotic mower from the boundary wire.

2. The robotic mower of claim 1, wherein the first axis of sensitivity has at least a vertical component and the second axis of sensitivity has at least a horizontal component, and the first and second axes of sensitivity are perpendicular to each other.

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

4. The robotic mower of claim 3, wherein no more than two of the first axis of sensitivity, the second axis of sensitivity and the third axis of sensitivity are coplanar, and the first axis of sensitivity, the second axis of sensitivity and the third axis of sensitivity are all generally perpendicular to one another.

5. The robotic mower of claim 3, wherein the control unit is configured to calculate an angular position from the signal from the sensor assembly.

6. The robotic mower of claim 1, 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.

7. A robotic mower system comprising:

a boundary wire;

a boundary wire driving circuit configured to transmit a signal on the boundary wire, the signal on the boundary wire generating a magnetic field; and

a robotic mower including;

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 of sensitivity for detecting a first component of the magnetic field along the first axis of sensitivity, the second inductive sensor oriented along a second axis of sensitivity for detecting a second component of the magnetic field along the second axis of sensitivity, the first and second axes of sensitivity 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 signal from the sensor assembly generated in response to the plurality of inductive sensors collectively detecting the signal on the boundary wire, 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.

8. The robotic mower system of claim 7, wherein the first axis of sensitivity has at least a vertical component and the second axis of sensitivity has at least a horizontal component, and the first and second axes of sensitivity are perpendicular to each other.

9. The robotic mower system of claim 7, wherein the plurality of inductive sensors comprises a third sensor being oriented along a third axis of sensitivity, the third axis of sensitivity forming non-zero angles with both the first axis of sensitivity and the second axis of sensitivity.

10. The robotic mower system of claim 9, wherein no more than two of the first axis of sensitivity, the second axis of sensitivity and the third axis of sensitivity are coplanar, and the first axis of sensitivity, the second axis of sensitivity and the third axis of sensitivity are all generally perpendicular to one another.

11. 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 inductive sensors arranged along at least two axes of sensitivity arranged at a non-zero angle relative to each other, the at least one signal representing magnetic field components along each of the at least two axes of sensitivity and being indicative of a distance of the robotic mower from a boundary wire.

12. The control unit of claim 11, wherein the control unit is configured to calculate an angular position from the at least one signal.

13. The control unit of claim 11, 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.

14. The control unit of claim 11, 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.