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Method for three-dimensional positions, orientation and mass distribution

  • US 5,844,415 A
  • Filed: 05/01/1996
  • Issued: 12/01/1998
  • Est. Priority Date: 02/03/1994
  • Status: Expired due to Term
First Claim
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1. A method of characterizing at least one property selected from mass distribution, position and orientation of an electrically conductive mass within a defined space, the method comprising the steps of:

  • a. disposing a plurality of electrodes proximate to the space and with defined positions relative to each other;

    b. providing an AC source;

    c. connecting the AC source to one of the electrodes to create an electric field around the mass;

    d. measuring current levels through a plurality of the electrodes to produce a measurement set; and

    e. inferring, from the measurement set, the instance of the property which, according to a forward model relating a plurality of instances of the property to corresponding expected current levels through a plurality of the electrodes given an AC signal through one of the electrodes, produces expected current levels closest to the measured levels, wherein the inferring step comprises;

    i. selecting an arbitrary instance of the property;

    ii. solving the forward model for the property instance to produce a set of expected current levels;

    iii. computing an error metric indicating the difference between the expected current levels and the measured current levels;

    iv. modifying the property instance to reduce the error metric; and

    v. repeating steps ii-iv until the error metric is minimized.

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