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DEVICE AND METHOD FOR DETERMINING A CHARACTERISTIC OF A PATH FORMED BY CONSECUTIVE POSITIONS OF A TRIAXIAL ACCELEROMETER RIGIDLY CONNECTED TO A MOBILE ELEMENT

  • US 20110264400A1
  • Filed: 10/20/2009
  • Published: 10/27/2011
  • Est. Priority Date: 10/22/2008
  • Status: Active Grant
First Claim
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1. A device for determining a characteristic of a trajectory formed of successive positions of a triaxial accelerometer (3A) rigidly tied to a mobile element (EM), between a first instant of immobility (t0) and a second instant of immobility (tn) of the triaxial accelerometer (3A), subsequent to said first instant of immobility (t0), said device comprising, furthermore, a triaxial additional sensor for measuring a vector of a substantially constant vector field between said first and second instants of immobility (t0,tn), in a fixed global reference frame (GF) tied to the terrestrial reference frame, said additional sensor being rigidly tied to said mobile element (EM) and fixed in the reference frame of the accelerometer (3A), and control means (CMD), characterized in that said control means (CMD) comprise:

  • first means (MD1) for determining said first and second instants of immobility (t0,tn) of the triaxial accelerometer (3A);

    second means (MD2) for determining a substantially invariant axis of rotation of the triaxial accelerometer (3A) between said first and second instants of immobility (t0,tn), and a plane orthogonal to said substantially invariant axis of rotation, in a mobile reference frame (LF) tied to the accelerometer (3A) or to the additional sensor on the basis of the vectors delivered by the triaxial accelerometer (3A), or on the basis of the vectors delivered by the additional sensor;

    first means (MC1) for calculating, at said successive instants (t0, t1, . . . , tn), first orthogonal projections onto said plane of the vectors delivered by the triaxial accelerometer (3A) and of the vectors delivered by the additional sensor in said mobile reference frame (LF);

    third means (MD3) for determining, at said successive instants (t0, t1, . . . , tn), the rotation for switching from said mobile reference frame (LF) to said fixed global reference frame (GF), on the basis of said first orthogonal projections of the vectors delivered by the additional sensor;

    second means (MC2) for calculating, at said successive instants (t0, t1, . . . , tn), second orthogonal projections in said fixed global reference frame (GF), of the first orthogonal projections, provided by said first calculation means (MC1), in said plane of the vectors delivered by the triaxial accelerometer (3A);

    third calculation means (MC3) for subtracting from each second orthogonal projection in said fixed global reference frame (GF) the mean vector over said successive instants (t0, t1, . . . , tn), so as to obtain the accelerations centered in said plane, devoid of the influence of terrestrial gravity and of drifts of said device, in said fixed global reference frame (GF); and

    fourth means (MC4) for calculating a characteristic of the trajectory on the basis of the centered accelerations.

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