Improvement to a method for controlling an autonomous mobile robot and related device

• US 20070027578A1
• Filed: 01/31/2003
• Published: 02/01/2007
• Est. Priority Date: 01/31/2002
• Status: Active Grant

• Current Assignee: Husqvarna AB (HUSQVARNA)
• Original Assignee: Husqvarna AB (HUSQVARNA)
• Inventors: Colens, Andre
• Granted Patent: US 7,787,989 B2
• Time in Patent Office: Days
• 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 microprocessor and a means for measuring the amplitude of a periodic electromagnetic signal of low frequency transmitted by one or more limiting elements, for example a wire, positioned at a periphery of a work surface of said mobile robot, said measuring means carrying out a sampling of the signal amplitude during each period, the result of each measurement of the sampling being stored in an independent memory and the measuring being repeated during several periods, the collected results being added to said memories until the content of one memory reaches a reference threshold, the number of samplings necessary and the content of each memory being then interpreted by numerical analysis to determine a distance or a variation of a distance of the robot in relation to said limiting elements.

2. The navigation device according to claim 1 wherein the means for measuring the amplitude is also the means for measuring the phase.

3. The navigation device according to claim 2 wherein the numerical analysis detects the shape of the signal and is able to determine a phase change caused by the passing of the robot beyond said limiting elements.

4. The device according to claim 1 wherein the numerical analysis 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 device according to claim 4 wherein the message is an instruction to the robot to return to the recharging station.

6. The device according to claim 1 wherein a phase reference is conserved by the onboard computer.

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

8. The device according to claim 1 wherein the frequency of the electromagnetic signal varies from 1 to 15 KHz.

9. The device according to claim 1 wherein the number of sampling per period varies from 4 to 64.

10. The device according to claim 1 comprising two detectors of the amplitude of the periodic signal placed at two different locations of the mobile machine.

11. A method for controlling a mobile robotic machine wherein the mobile robot comprises the device according to claim 1.

12. A method for controlling a mobile robotic machine comprising the measurement of the amplitude and of the phase of a periodic electromagnetic signal of low frequency transmitted by one or several limit elements, for example a wire, located at the periphery of the working surface of said mobile robot, said measuring means effecting a sampling of the amplitude of the signal during each period, the result of each sampling measurement being stored in a independent memory and the measurements being repeated during several periods, the collected results being added in said memories until the content of one memory reach a reference value, the number of necessary samplings and the content of each memory allowing the interpretation by numeric analysis performed by the microprocessor in order to determine the distance or variation of the distance relative to said limiting elements and/or the shape of the periodic signal.

13. A method according to claim 12 wherein an instruction of return is transmitted to the robotic machine when a phase change is detected.