Method for controlling an autonomous mobile robot and related device

• US 7,787,989 B2
• Filed: 01/31/2003
• Issued: 08/31/2010
• Est. Priority Date: 01/31/2002
• Status: Active Grant

• Current Assignee: Husqvarna AB (HUSQVARNA)
• Original Assignee: HUSQVARNA
• Inventors: Colens, Andre
• Primary Examiner(s): Tran; Khoi
• Assistant Examiner(s): Sample; Jonathan
• Application Number:
  US10/503,041
• Publication Number:
  US 20070027578A1
• Time in Patent Office: 2,769 Days
• Field of Search: 700/245, 700/247, 700/257, 700/258, 700/259
• US Class Current: 700/245
• CPC Class Codes: G05D 1/0265 using buried wires

Abstract

The invention concerns a navigation device for a mobile robot comprising means for measuring the amplitude and the phase of an electromagnetic signal emitted by a wire acting as limit for a working area of the robot. The measuring means samples the amplitude of the signal during each time interval, the result of each measurement is stored in a memory and the measurements are repeated for several time intervals, the collected results being added in said memories until the content of a memory reaches a reference threshold. The number of samples required and the content of each memory is interpreted by numerical analysis to determine the distance or distance variation relative to said limiting elements. Any phase change corresponding to a passage beyond the limiting wire is easily detected and results for example in a command returning the robot to its working area.

Claims

1. A navigational device for a mobile robot, comprising:

a plurality of independent memories;

at least one limiting element positioned at a periphery of a work surface of said mobile robot;

a means for measuring the amplitude of a periodic electromagnetic signal of low frequency transmitted by said at least one limiting element, said measuring means carrying out at least two samples of the signal amplitude during a single period;

a means for adding a first one of said at least two samples to a content of a first one of said plurality of independent memories and for adding a second one of said at least two samples to a content of a second one of said plurality of independent memories, said content of said second one of said plurality of independent memories independent from said content of said first one of said plurality of independent memories, said at least two samples being measured repeatedly over several periods and for each period during which said at least two samples are measured said at least two samples being added to said respective ones of said plurality of independent memories reaches a reference threshold;

wherein said at least two samples are synchronic samples of said periodic electromagnetic signal amplitude measured repeatedly over several periods;

a means for interpreting by numerical analysis the number of samples necessary and the content of each of said plurality of independent memories to determine a distance of said robot in relation to said at least one limiting element.

2. The navigation device according to claim 1 further comprising a means for measuring the phase of said periodic electromagnetic signal.

3. The navigation device according to claim 2 wherein the numerical analysis interpreting means also detects the shape of the signal and is able to determine a phase change caused by the passing of the robot beyond said at least one limiting element.

4. The navigation device according to claim 1 further comprising a peripheral wire generator which produces said periodic electromagnetic signal of low frequency, wherein the numerical analysis interpreting means is also capable of detecting a phase modulation generated by the peripheral wire generator, and therefore of receiving a message sent by the peripheral wire to the mobile robot.

5. The navigation device according to claim 4 wherein the message is an instruction to the robot to return to a recharging station.

6. The navigation device according to claim 1 wherein a phase reference is conserved.

7. The navigation device according to claim 1 adapted to a robotic lawn mower.

8. The navigation device according to claim 1 wherein said amplitude measuring means further comprises two detectors of the amplitude of the periodic signal placed at two different locations of the mobile machine.

13. The navigation device according to claim 1 wherein said one or more limiting elements further comprise a wire.

14. The navigation device according to claim 1 wherein said distance comprises a distance variation of said robot relative to said at least one limiting element.

15. The navigation device according to claim 1 wherein said means for interpreting by numerical analysis further comprises a microprocessor.

9. A method of controlling a mobile robotic machine, comprising the steps of:

measuring an amplitude and a phase of a periodic electromagnetic signal of low frequency transmitted by at least one limit element located at the periphery of a working surface of said mobile robot, said measuring means effecting at least two samples of the amplitude of the signal during each period;

storing the result of said at least two samples separately and distinctly in at least two memories;

repeating said measuring and storing steps during several periods, said at least two samples being added in said at least two memories until the content of one memory reaches a reference value, the number of necessary samples and the content of each memory allowing the interpretation by numeric analysis performed by the microprocessor, wherein said interpretation by numeric analysis further comprises determining a shape of said periodic signal.

10. A method according to claim 9 wherein an instruction of return is transmitted to the robotic machine when a phase change is detected.

11. The method of claim 9 wherein said interpretation by numeric analysis further comprises determining a distance between said mobile robotic machine and said at least one limiting element.

12. The method of claim 9 wherein said interpretation by numeric analysis further comprises determining a variation of distance between said mobile robotic machine and said at least one limiting element.