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Robotic working tool

  • US 9,713,303 B2
  • Filed: 02/21/2013
  • Issued: 07/25/2017
  • Est. Priority Date: 02/21/2013
  • Status: Active Grant
First Claim
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1. A robotic work tool for use with a guiding wire, the guiding wire being configured to conduct electric current to generate a magnetic field around the guiding wire, the robotic work tool comprising:

  • a sensing system configured to detect a strength of the magnetic field, the sensing system comprising a first magnetic field sensor and a second magnetic field sensor, the second magnetic field sensor being positioned at an offset with respect to the first magnetic field sensor;

    a steering system; and

    a controller configured to control said steering system in response to output from said sensing system by means of a feedback control loop so as to cause movement of said robotic work tool along said guiding wire, wherein the controller is configured to;

    determine a distance measure indicative of a distance between the robotic work tool and the guiding wire, wherein determining the distance measure comprisesreading a first sensor signal value from the first magnetic field sensor,reading a second sensor signal value from the second magnetic field sensor,assessing the first sensor signal value and a relation between the first sensor signal value and the second sensor signal value, anddetermining a present distance value, in response to multiple possible present distance values, based on the relation between the first sensor signal value and the second sensor signal value; and

    adjust at least one parameter of the feedback control loop in response to the distance measure determined.

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