Dynamic magnetic anomaly compensation
First Claim
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1. A system for dynamically compensating for magnetic anomalies due to the proximity of ferromagnetic objects or electric motors, comprising:
- a parallelopiped;
three-axis magnetometers each having three orthogonal axes, each of said magnetometers measuring magnetic field thereat and supplying a corresponding output, located at selected corners of said parallelopiped, said magnetometers having their three orthogonal axes aligned with the three orthogonal axes of the other magnetometers;
a processor coupled to the outputs of said magnetometers to derive a magnetic anomaly gradient vector in terms of a difference in sensed magnetic field due to the presence of an anomaly; and
,an instrument for which heading is an output including a compass, said magnetic anomaly gradient vector coupled to said compass to compensate said compass for said magnetic anomalies.
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Abstract
An array of three-axis magnetometers used for dynamic magnetic anomaly compensation are located at the corners of a parallelopiped, with pairs of magnetometer outputs used to derive a magnetic anomaly gradient vector used to compensate a compass and/or the output of a gyroscope in an inertial management unit. The system may be used in a neutrally buoyant remotely operated vehicle to permit ascertaining of course and position in the absence of surface control signals.
44 Citations
17 Claims
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1. A system for dynamically compensating for magnetic anomalies due to the proximity of ferromagnetic objects or electric motors, comprising:
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a parallelopiped; three-axis magnetometers each having three orthogonal axes, each of said magnetometers measuring magnetic field thereat and supplying a corresponding output, located at selected corners of said parallelopiped, said magnetometers having their three orthogonal axes aligned with the three orthogonal axes of the other magnetometers; a processor coupled to the outputs of said magnetometers to derive a magnetic anomaly gradient vector in terms of a difference in sensed magnetic field due to the presence of an anomaly; and
,an instrument for which heading is an output including a compass, said magnetic anomaly gradient vector coupled to said compass to compensate said compass for said magnetic anomalies. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system for dynamically compensating for magnetic anomalies due to the proximity of ferromagnetic objects or electric motors, comprising:
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a parallelopiped; three-axis magnetometers each having three orthogonal axes, said magnetometers being located at selected corners of said parallelopiped, each of said magnetometers having the three orthogonal axes thereof aligned with the three orthogonal axes of the other magnetometers; an instrument for which heading is an output, said instrument including a compass and a gyroscope; and
,a processor coupled to the outputs of said magnetometers to derive a magnetic anomaly gradient vector in terms of the difference in sensed magnetic field due to the presence of an anomaly, said magnetic anomaly gradient vector used to compensate for heading errors from said instrument by compensating said compass or said gyroscope. - View Dependent Claims (8)
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9. A method for assuring positional control of a remotely operated vehicle adapted to be maneuvered around the hull of a vessel when acoustic network positioning signals are unavailable, comprising the steps of:
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providing the remotely operated vehicle with an inertial management unit having a compass, a gyroscope and a positional output for ascertaining the position of the remotely operated vehicle and for controlling the position thereof; establishing the position of the remotely operated vehicle utilizing the acoustic network; establishing the position of the remotely operated vehicle utilizing the inertial management unit when the position associated with the acoustic network is unreliable; detecting any magnetic anomaly gradient vector at the remotely operated vehicle; and
,compensating the positional output of the inertial management unit utilizing the detected magnetic anomaly gradient vector. - View Dependent Claims (10, 11, 12, 13)
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14. For use in a neutrally buoyant remotely operated vehicle to permit ascertaining position of said vehicle in the absence of surface control signals, said vehicle having an inertial management unit including a compass, apparatus for compensating the compass used by the inertial management unit for said vehicle for magnetic anomalies in the vicinity of said compass, comprising:
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an array of three-axis magnetometers, each having three orthogonal axes, said magnetometers being disposed at selected corners of a parallelopiped, said magnetometers having their axes co-aligned; and
,a processor for deriving from pairs of outputs of said magnetometers a magnetic anomaly gradient at said compass in terms of the difference in sensed magnetic field due to the presence of an anomaly and for generating a deviation correction for said compass responsive to said magnetic anomaly gradient, thus to cancel out the effect of said magnetic anomaly gradient on said compass, whereby said compass may be used by said inertial management unit in the absence of surface control signals regardless of local magnetic anomalies. - View Dependent Claims (15, 16, 17)
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Specification