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Heading for a hybrid navigation solution based on magnetically calibrated measurements

  • US 9,939,532 B2
  • Filed: 01/09/2015
  • Issued: 04/10/2018
  • Est. Priority Date: 01/09/2015
  • Status: Active Grant
First Claim
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1. A method for determining a heading for a hybrid navigation system with magnetometer aiding, the method comprising:

  • receiving signals from a plurality of global navigation satellite system (GNSS) satellites at a location corresponding to an object;

    obtaining three-dimensional inertial measurements from one or more inertial sensors corresponding to the object;

    obtaining three-dimensional magnetic measurements from one or more magnetometers corresponding to the object;

    estimating states for position, velocity, roll, pitch, and heading of the object with a magnetic calibration filter;

    estimating states for calibration of the three-dimensional inertial measurements with the magnetic calibration filter;

    estimating states for bias and drift of a GNSS clock with the magnetic calibration filter; and

    estimating states for pseudorange biases for the signals from the GNSS satellites with the magnetic calibration filterestimating nine soft iron bias states and three hard iron bias states for biases of the three-dimensional magnetic measurements with the magnetic calibration filter using the three-dimensional inertial measurements, data from the signals from the plurality of GNSS satellites, and the three-dimensional magnetic measurements;

    calculating an artificial heading for the object as a function of
    ψ

    ma=f



    ,mcalBx,mcalBy,mcalBz

    dec)where φ

    is the roll estimate from a main navigation filter, θ

    is the pitch estimate from the main navigation filter, ψ

    dec is the magnetic declination, and mcalBx, mcalBy, and mcalBz are calibrated magnetic measurements with components x, y, and z in the body frame, respectively, wherein mcalB is calculated as a function of
    mcalB=f(Dmag,{tilde over (m)}B,bmagB)where Dmag is the magnetic bias state matrix corresponding to soft iron biases, bmagB is the magnetic bias state vector corresponding to hard iron biases, and {tilde over (m)}B is the three-dimensional magnetic measurements;

    estimating a main navigation solution for the object with the main navigation filter using the three-dimensional inertial measurements, data from the signals from a plurality of GNSS satellites, and the artificial heading.

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