inertial orientation tracker having automatic drift compensation using an at rest sensor for tracking parts of a human body

  • US 6,786,877 B2
  • Filed: 12/18/2001
  • Issued: 09/07/2004
  • Est. Priority Date: 06/16/1994
  • Status: Expired due to Fees
First Claim
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1. An apparatus to be attached to a body part of a human having a size between the sizes of a finger and a torso, said body part having an orientation, relative to an external reference frame, said apparatus generating an orientation signal that corresponds to at least two degrees of freedom of said orientation of said body part, said apparatus comprising:

  • a. a self contained angular rate sensor that generates first sensor signals that correspond to rotational rates, which are first order integrals of rotational accelerations of said body part about at least two axes of said body part, and said first sensor signals being impervious to any interference from electromagnetic, acoustic, optical and mechanical sources;

    b. a mechanism for mounting said sensor to said body part;

    c. coupled to said sensor, an integrator signal processor that integrates said rotational rate signals with respect to time and generates an orientation signal that corresponds to said at least two degrees of freedom of said orientation of said body part; and

    d. a verifier drift compensator, coupled to said angular rate sensor and said integrator, said drift compensator comprising an at rest sensor that identifies any occurrence of periods exceeding a predetermined duration when the body is substantially at rest relative to said reference frame, periodically measures said orientation of said body part by a means different from using said rotational rate signal and generates an orientation drift compensation signal based on results of said verification measurement to reduce the effect of any drift over time in said orientation signal, said at rest sensor comprising;

    i. a timer;

    ii. a signal generator that generates signals that correspond to;

    A. nongravitational acceleration and;

    B. rotation of the body part;

    means for storing and comparing said nongravitational acceleration and rotation signals at several moments over time; and

    iv. a signal generator that generates an at rest signal if said nongravitational acceleration and rotation signals are both constant over a preselected time period.

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