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System and method for electromagnetic navigation in the vicinity of a metal object

  • US 8,611,986 B2
  • Filed: 03/02/2012
  • Issued: 12/17/2013
  • Est. Priority Date: 05/05/2005
  • Status: Active Grant
First Claim
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1. A system for determining the position and orientation of an object, said system comprising:

  • a transmitter assembly comprising at least two transmitters, each said transmitter capable of simultaneously emitting plural magnetic fields at different frequencies, wherein said transmitters are configured to;

    simultaneously emit navigation magnetic fields, wherein the navigation magnetic field emitted by each said transmitter is at a frequency different than the frequencies of the navigation magnetic fields emitted by the other said transmitters; and

    with each said transmitter, simultaneously with the navigation magnetic field emitted by said transmitter, emit a plurality of surveillance magnetic fields, the surveillance magnetic fields being at different frequencies and at frequencies less than the frequencies at which said transmitters emit the navigation magnetic fields wherein the surveillance magnetic fields are sequentially emitted by said transmitters so that, after a first said transmitter emits the surveillance magnetic fields, a second said transmitter emits the surveillance magnetic fields;

    at least two sensors, each sensor configured to measure the strength of a composite magnetic field that is the sum of the navigation magnetic fields and the surveillance magnetic fields emitted by said transmitters that are received by the sensor and to generate a sensor signal representative of the strength of the received composite magnetic field; and

    a processor connected to said sensor to receive the sensor signals, said processor is further configured to;

    for each sensor signal, based on the sensor signal from said sensor, determine the strengths of the navigation magnetic fields and the strengths of the surveillance magnetic fields received by said sensor;

    based on the strengths of the surveillance magnetic fields that are transmitted with each navigation magnetic field, determine the strength of eddy current induced magnetic field as a function of field frequency;

    for the navigation magnetic field emitted with the surveillance magnetic fields, based on the strength of the eddy current induced magnetic fields as a function of field frequency and the frequency of the navigation magnetic field, determine an error value for the navigation magnetic field;

    for the navigation magnetic field emitted with the surveillance magnetic fields received by each sensor, based on the strength of the navigation magnetic field and the error value for the navigation magnetic field, generate a corrected measurement of navigation magnetic field strength; and

    based on the corrected measurements of navigation magnetic field strengths for the plurality of navigation magnetic fields that are received by said plurality of sensors, compute position and orientation data for the sensors.

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