Magnetic direction finding device with improved accuracy
First Claim
1. Apparatus for accurately measuring the relative positioning in three-dimensional space of a first object relative to a second object when said objects are in proximity to surrounding structures tending to distort magnetic field patterns, comprising:
- (a) a first plurality of mutually orthogonal flux transmitting coils affixed to said first object to define a coordinate frame of reference;
(b) a second plurality of mutually orthogonal flux receiving means affixed to said second object;
(c) means for energizing each of said transmitting coils with a voltage having a number of harmonically related frequency components sufficient to characterize the distortion of said magnetic field patterns;
(d) means coupled to said plurality of receiving means for periodically sampling the instantaneous analog voltage induced in said receiving means by the transmitted flux and converting said analog voltage samples into a corresponding digital value;
(e) FFT processor means coupled to receive said digital values for determining pitch and yaw angles of said first object concurrently at said number of harmonically related frequencies; and
(f) computing means coupled to receive digital values defining the multiple pitch and yaw angles to the multiple harmonically related frequencies for mathematically extrapolating said multiple pitch and yaw angles to produce an estimate of a pitch and yaw angle associated with an arbitrarily low frequency at which distortion of said magnetic field is substantially zero.
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Accused Products
Abstract
A system for determining the relative orientation in three dimensions between a fixed frame of reference and an unconstrained object. Mutual coupling between three orthogonally disposed transmitting coils driven by a multifrequency source and three orthogonal receiving coils produce sets of analog voltages which are sampled; digitized and processed using a fast fourier transform device to yield directional components for determining the pitch and yaw angles about a line-of-sight axis. By using a multi-frequency source to drive the transmitting coils and by deriving coordinate component measurements to at least two discrete frequencies, errors in the results due to eddy currents in surrounding conductive structures can be compensated for.
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Citations
5 Claims
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1. Apparatus for accurately measuring the relative positioning in three-dimensional space of a first object relative to a second object when said objects are in proximity to surrounding structures tending to distort magnetic field patterns, comprising:
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(a) a first plurality of mutually orthogonal flux transmitting coils affixed to said first object to define a coordinate frame of reference; (b) a second plurality of mutually orthogonal flux receiving means affixed to said second object; (c) means for energizing each of said transmitting coils with a voltage having a number of harmonically related frequency components sufficient to characterize the distortion of said magnetic field patterns; (d) means coupled to said plurality of receiving means for periodically sampling the instantaneous analog voltage induced in said receiving means by the transmitted flux and converting said analog voltage samples into a corresponding digital value; (e) FFT processor means coupled to receive said digital values for determining pitch and yaw angles of said first object concurrently at said number of harmonically related frequencies; and (f) computing means coupled to receive digital values defining the multiple pitch and yaw angles to the multiple harmonically related frequencies for mathematically extrapolating said multiple pitch and yaw angles to produce an estimate of a pitch and yaw angle associated with an arbitrarily low frequency at which distortion of said magnetic field is substantially zero. - View Dependent Claims (2, 3, 4, 5)
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Specification