Robotic garden tool following wires at a distance using multiple signals

• US 9,119,341 B2
• Filed: 04/14/2010
• Issued: 09/01/2015
• Est. Priority Date: 04/14/2010
• Status: Active Grant

• Current Assignee: Husqvarna AB (HUSQVARNA)
• Original Assignee: Husqvarna AB (HUSQVARNA)
• Inventors: Jgenstedt, Patrik
• Primary Examiner(s): Jabr, Fadey
• Assistant Examiner(s): Troost, Aaron L
• Application Number:
  US13/639,302
• Publication Number:
  US 20130030609A1
• Time in Patent Office: 1,966 Days
• Field of Search: 901/1, 901/46, 901/50, 700/245, 700/253, 700/258, 318/568.12, 318/568.16, 318/568.22, 701/2, 701/23, 701/25, 701/26, 180/67
• US Class Current: 1/1
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: G05D 1/0265 using buried wires

Abstract

The present invention relates to a method (300) and a system (100) for guiding a robotic garden tool to a predetermined position. The robotic garden tool includes a control unit (104) and a sensor unit (102) to detect signals. The sensor unit (102) detects a first signal (110) from a first signal source (106) and the robotic garden tool follows the first signal (110) at a varying distance from the first signal source (106) that is less than or equal to a maximum distance to the first signal source, towards the predetermined position. Wherein, the varying distance is a function of the strength of the detected first signal (110). While detecting the first signal (110), the sensor unit may also detect a second signal (112) from a second signal source (108). The robotic garden tool follows the first signal (110) at a varying distance that is less than or equal to the maximum distance to the first signal source, wherein the maximum distance, at least in part, is now set based on the strength of the detected second signal (112), to reach a predetermined position.

Claims

1. A method for guiding a robotic garden tool to a predetermined position, the robotic garden tool is provided with at least one sensing means adapted to detect a signal in a wire, the method comprising the steps wherein the robotic garden tool;

detects a first signal from a first signal source,

follows the first signal source at a varying distance to the first signal source, wherein the varying distance is a distance less than or equal to a first maximum distance to the first signal source,

detects a second signal from a second signal source, and

responsive to detection of the second signal, follows the first signal source at a varying distance from the first signal source that is less than or equal to a second maximum distance from the first signal source,

wherein the second maximum distance to the first signal source is set based on detected strength of both the first signal source and the second signal source.

2. A method according to claim 1, wherein the at least one sensing means comprises a first and a second sensing means, and wherein the first sensing means is adapted to detect the first signal from the first signal source, and the second sensing means is adapted to detect the second signal from the second signal source.

3. A method according to claim 1, wherein the first signal source is a guide wire.

4. A method according to claim 1, wherein second signal source is a boundary wire.

5. A method according to claim 1, wherein the robotic garden tool follows the first signal source at a varying distance from the first signal source based at least in part on a detected strength of the first signal from the first signal source.

6. A method according to claim 1, wherein the robotic garden tool is configured to reduce the second maximum distance on detection of a larger strength of the second signal from the second signal source.

7. A method according to claim 1, wherein the first signal and the second signal are magnetic field signals.

8. A method according to claim 1, further comprising determining the distance of the robotic garden tool from both the first signal source and the second signal source.

9. A method according to claim 8, further comprising determining the maximum distance based on the determined distances from both the first signal source and the second signal source.

15. A method according to claim 1, wherein the robotic garden tool is configured to reduce the second maximum distance on detection of a larger strength of the second signal from the second signal source.

10. A robotic garden tool guiding system comprising,

a first signal source providing a first signal,

a second signal source providing a second signal,

a robotic garden tool comprising at least one sensing means adapted to detect the first signal and the second signal,

wherein the robotic garden tool is adapted to detect the first signal and follow the first signal source towards a predetermined position, at a varying distance to the first signal source wherein the varying distance is less than or equal to a first maximum distance to the first signal source, and

responsive to detection of the second signal, follows the first signal source at a varying distance from the first signal source that is less than or equal to a second maximum distance from the first signal source,

wherein the second maximum distance to the first signal source is set based on detected strength of both the first signal source and the second signal source.

11. A system according to claim 10, wherein the at least one sensing means, comprises a first and a second sensing means, and wherein the first sensing means is adapted to detect the first signal and the second sensing means is adapted to detect the second signal.

12. A system according to claim 10, wherein first signal source is a guiding wire.

13. A system according to claim 10, wherein second signal source is a boundary wire.

14. A system according to claim 10, wherein the robotic garden tool is adapted to follow the first signal source at a varying distance to the first signal source based at least in part on a detected strength of the first signal from the first signal source.

16. A system according to claim 10, wherein first signal and the second signal are magnetic field signals.

17. A system according to claim 10, wherein the predetermined position is the position of a charging station.

18. A system according to claim 10, wherein the robotic garden tool is a robotic lawn mower.