×

Method and device for simultaneous identification and correction of errors in the measurements of a magnetometer

  • US 5,682,335 A
  • Filed: 04/09/1996
  • Issued: 10/28/1997
  • Est. Priority Date: 04/10/1995
  • Status: Expired due to Term
First Claim
Patent Images

1. A method for identifying and correcting errors due to determined perturbations in the measurements of a magnetometer (2) mounted on board a vehicle (3), wherein:

  • a theoretical model correcting the measurement errors of the magnetometer is defined in the form;

    ##EQU37## n being an integer greater than or equal to 1, in which;

    Hc is the corrected field, A! is a matrix to be determined,Hm is the value measured by the magnetometer (2) of the magnetic field in a reference frame (R1) associated with said vehicle (3),the elements C!i are matrices to be determined, with respective dimensions (3×

    mi), mi being an integer greater than or equal to 1,the elements E!i are matrices with respective dimensions (mi×

    1), the coefficients of which are measurements of perturbing parameters or combinations of such measurements, andHp is a perturbing field to be determined;

    the corrected field Hc is assumed to be the terrestrial field defined in the vehicle reference frame, so that;

    ##EQU38## with;

    H representing the effective value of the magnetic field in a base reference frame (R2), and M! representing a change of frame matrix from said base reference frame (R2) to said vehicle reference frame (R1);

    successive measurements Hm of the magnetic field are taken using the magnetometer during movements of the vehicle;

    the coefficients of the various matrices E!i are determined on the basis of the measurements of the perturbing parameters, taken simultaneously with the Hm measurements;

    the coefficients of the change of frame matrix M! are determined;

    an error vector E with components Ex, Ey and Ez is defined, defined by the equation;

    ##EQU39## a composite error E2 =Ex2 +Ey2 +Ez2 is defined;

    a system of equations formed by m equations of the type (∂

    Σ

    E2)/∂

    c1=0, 1=1 to m, (∂

    Σ

    E2)/∂

    c1 corresponding to the partial derivative of the sum of the composite errors Σ

    E2 is defined, for all the measurements, with respect to a coefficient cl, the various coefficients cl representing the coefficients to be determined in said theoretical model, namely the coefficients of the matrix A!, of the matrices C!i and of the vector Hp, as well as at least one component of the effective magnetic field H;

    said system of equations is solved so as to obtain said coefficients cl, including said component of the effective magnetic field H; and

    the corrective model obtained on the basis of said coefficients is used to correct the errors due to determined perturbations in the measurements of said magnetometer (2).

View all claims
  • 2 Assignments
Timeline View
Assignment View
    ×
    ×