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Position sensor and assembly

  • US 7,307,416 B2
  • Filed: 10/22/2004
  • Issued: 12/11/2007
  • Est. Priority Date: 10/22/2004
  • Status: Active Grant
First Claim
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1. A position sensor assembly for detecting rotation of a rotating body, the rotating body having a longitudinal axis, the position sensor assembly comprising:

  • a cylindrically-shaped magnet positioned coaxially with the longitudinal axis of the rotating body, wherein the cylindrically-shaped magnet is rotatable with the rotating body;

    a plurality of Hall sensors disposed on a position sensor assembly and positioned at equal distances from a center of the cylindrically-shaped magnet, wherein rotation of the magnet is detected by the plurality of Hall sensors, wherein the plurality of Hall sensors includes two Hall sensors positioned 90 degrees apart from each other;

    a processor configured to receive output from the plurality of Hall sensors to determine an actual position of the rotating body and,a support surrounding an end of the rotating body and for holding the cylindrically-shaped magnet to the rotating body, wherein the support includes a cup shaped portion for holding the cylindrically-shaped magnet, wherein the Hall sensors are located exteriorly of the cup shaped portion;

    a processor configured to receive output from the Hall sensors, wherein rotating body position is extracted from the output using an algorithm as follows;


    f



    )=A cos φ



    B sin φ


    f





    )=−

    A sin φ



    B cos φ

    where A and B are signals obtained from the Hall sensors, A=Bm sin θ and

    B=Bm cos θ

    , Bm is amplitude of signal, θ

    is a position variable in mechanical degrees, and φ

    is an initial estimation of position angle, andφ

    new

    old

    f (θ



    )/f ′





    ), wherein the estimated position angle φ

    , provides a guessed value of an actual position of the rotating body so that convergence of φ

    with θ

    , as known values A and B are measured, can be checked, wherein the convergence of θ and

    100 indicates that θ

    is the actual position of the rotating body.

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