MAGNETIC ANOMALY SENSING SYSTEM AND METHODS FOR MANEUVERABLE SENSING PLATFORMS
First Claim
1. A magnetic anomaly sensing system, comprising:
- a support that is electrically non-conductive and non-magnetic;
at least one pair of triaxial magnetometer-accelerometer (TMA) sensors coupled to said support and separated by a known distance, each of said TMA sensors having X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes that are parallel to one another and parallel to said X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes of all others of said TMA sensors, wherein each of said TMA sensors outputs X,Y,Z components (Bx,By,Bz) of local magnetic fields and X,Y,Z components (Ax,Ay,Az) of local gravitational acceleration fields;
means for processing said X,Y,Z components (Bx,By,Bz) and (Ax,Ay,Az) for each of said TMA sensors to generate motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) of local magnetic fields for each of said TMA sensors;
means for generating a difference between said motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) for each said pair of TMA sensors to generate differential vector field components (Δ
Bx,Δ
By,Δ
Bz);
means for generating gradient components Gij using said differential vector field components (Δ
Bx,Δ
By,Δ
Bz) where i={x,y,z} and j={x,y,z} and wherein, for each of said X,Y,Z magnetic sensing axes, said gradient components Gij are defined by (Δ
Bx/Δ
j,Δ
By/Δ
j,Δ
Bz/Δ
j) wherein Δ
j is a distance between said pair of TMA sensors relative to a j-th one of said X,Y,Z magnetic sensing axes; and
means for generating a scalar-quantity gradient contraction
for each said pair of TMA sensors wherein said gradient contraction C2 changes monotonically with proximity to a magnetic target.
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Abstract
A system and method for sensing magnetic anomalies uses a gradiometer having at least one pair of triaxial magnetometer-accelerometer (TMA) sensors. Each TMA sensor has X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes that are parallel to one another and to the X,Y,Z magnetic sensing and acceleration axes of all other TMA sensors. Each TMA sensor outputs components (Bx,By,Bz) of local magnetic fields and components (Ax,Ay,Az) of local gravitational acceleration fields. The components (Bx,By,Bz) and (Ax,Ay,Az) output from each TMA sensor are processed to generate motion-compensated components (Bcx,Bcy,Bcz) of local magnetic fields. A difference is generated between the motion-compensated components (Bcx,Bcy,Bcz) for each pair of TMA sensors thereby generating differential vector field components (ΔBx,ΔBy,ΔBz). For improved accuracy, the differential vector field components (ΔBx,ΔBy,ΔBz) are adjusted using the local gravitational acceleration field components and motion-compensated local magnetic field components in order to compensate for gradiometer motion. Gradient components are generated using the differential vector field components (ΔBx,ΔBy,ΔBz). In general, for each of the magnetic sensing axes, the gradient components G are defined by (ΔBx/Δj,ΔBy/Δj,ΔBz/Δj), wherein Δj is a distance between a pair of TMA sensors relative to a j-th one of the X,Y,Z magnetic sensing axes. A scalar-quantity gradient contraction defined as
is generated for each pair of TMA sensors. The gradient contraction C2 is a robust, rotationally-invariant quantity that changes monotonically with proximity to a magnetic target.
17 Citations
20 Claims
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1. A magnetic anomaly sensing system, comprising:
-
a support that is electrically non-conductive and non-magnetic;
at least one pair of triaxial magnetometer-accelerometer (TMA) sensors coupled to said support and separated by a known distance, each of said TMA sensors having X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes that are parallel to one another and parallel to said X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes of all others of said TMA sensors, wherein each of said TMA sensors outputs X,Y,Z components (Bx,By,Bz) of local magnetic fields and X,Y,Z components (Ax,Ay,Az) of local gravitational acceleration fields;
means for processing said X,Y,Z components (Bx,By,Bz) and (Ax,Ay,Az) for each of said TMA sensors to generate motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) of local magnetic fields for each of said TMA sensors;
means for generating a difference between said motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) for each said pair of TMA sensors to generate differential vector field components (Δ
Bx,Δ
By,Δ
Bz);
means for generating gradient components Gij using said differential vector field components (Δ
Bx,Δ
By,Δ
Bz) where i={x,y,z} and j={x,y,z} and wherein, for each of said X,Y,Z magnetic sensing axes, said gradient components Gij are defined by (Δ
Bx/Δ
j,Δ
By/Δ
j,Δ
Bz/Δ
j) wherein Δ
j is a distance between said pair of TMA sensors relative to a j-th one of said X,Y,Z magnetic sensing axes; and
means for generating a scalar-quantity gradient contraction
for each said pair of TMA sensors wherein said gradient contraction C2 changes monotonically with proximity to a magnetic target. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of sensing magnetic anomalies, comprising the steps of:
-
providing a non-magnetic and electrically non-conductive support with at least one pair of triaxial magnetometer-accelerometer (TMA) sensors coupled thereto and separated by a known distance, each of said TMA sensors having X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes that are parallel to one another and parallel to said X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes of all others of said TMA sensors, wherein each of said TMA sensors outputs X,Y,Z components (Bx,By,Bz) of local magnetic fields and X,Y,Z components (Ax,Ay,Az) of local gravitational acceleration fields;
generating motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) of local magnetic fields for each of said TMA sensors using said X,Y,Z components (Bx,By,Bz) and (Ax,Ay,Az) for each of said TMA sensors;
generating a difference between said motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) for each said pair of TMA sensors to generate differential vector field components (Δ
Bx,Δ
By,Δ
Bz);
generating gradient components Gij using said differential vector field components (Δ
Bx,Δ
By,Δ
Bz) where i={x,y,z} and j={x,y,z} and wherein, for each of said X,Y,Z magnetic sensing axes, said gradient components Gij are defined by (Δ
Bx/Δ
j,Δ
By/Δ
j,Δ
Bz/Δ
j), wherein Δ
j is a distance between said pair of TMA sensors relative to a j-th one of said X,Y,Z magnetic sensing axes; and
generating a scalar-quantity gradient contraction
for each said pair of TMA sensors wherein said gradient contraction C2 changes monotonically with proximity to a magnetic target. - View Dependent Claims (8, 9, 10, 11, 12, 14, 16, 18, 20)
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13. A magnetic anomaly sensing system, comprising:
-
a support that is electrically non-conductive and non-magnetic;
a pair of triaxial magnetometer-accelerometer (TMA) sensors coupled to said support, each of said TMA sensors having X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes that are parallel to one another and parallel to said X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes of another of said TMA sensors, said pair of TMA sensors being positioned such that a known distance A separates said TMA sensors along only one coordinate axis of said X,Y,Z magnetic sensing axes and said X,Y,Z acceleration sensing axes, wherein each of said TMA sensors outputs X,Y,Z components (Bx,By,Bz) of local magnetic fields and X,Y,Z components (Ax,Ay,Az) of local gravitational acceleration fields;
means for processing said X,Y,Z components (Bx,By,Bz) and (Ax,Ay,Az) for each of said TMA sensors to generate motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) of local magnetic fields for each of said TMA sensors;
means for generating a difference between said motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) for said pair of TMA sensors to generate differential vector field components (Δ
BX,Δ
By,Δ
Bz);
means for generating gradient components Gi using said differential vector field components (Δ
Bx,Δ
By,Δ
Bz) where i={x,y,z} and wherein, for each of said X,Y,Z magnetic sensing axes, said gradient components Gi are defined by (Δ
Bx/Δ
,Δ
By/Δ
,Δ
Bz/Δ
); and
means for generating a scalar-quantity gradient contraction
for said pair of TMA sensors wherein said gradient contraction C2 changes monotonically with proximity to a magnetic target.
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15. A method for sensing magnetic anomalies, comprising the steps of:
-
a) providing a non-magnetic and electrically non-conductive support with a pair of triaxial magnetometer-accelerometer (TMA) sensors coupled thereto, each of said TMA sensors having X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes that are parallel to one another and parallel to said X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes of another of said TMA sensors;
b) positioning said pair of TMA sensors on said non-magnetic support such that a known distance A separates said TMA sensors along only one coordinate axis of said X,Y,Z magnetic sensing axes and said X,Y,Z acceleration sensing axes;
c) moving said non-magnetic support with said pair of TMA sensors coupled thereto to a measurement location wherein each of said TMA sensors outputs X,Y,Z components (Bx,By,Bz) of local magnetic fields and X,Y,Z components (Ax,Ay,Az) of local gravitational acceleration fields;
d) generating motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) of local magnetic fields for each of said TMA sensors using said X,Y,Z components (Bx,By,Bz) and (Ax,Ay,Az) for each of said TMA sensors;
e) generating a difference between said motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) for said pair of TMA sensors to generate differential vector field components (Δ
Bx,Δ
By,Δ
Bz);
f) generating gradient components Gi using said differential vector field components (Δ
Bx,Δ
By,Δ
Bz) where i={x,y,z} and wherein, for each of said X,Y,Z magnetic sensing axes, said gradient components Gi are defined by (Δ
Bx/Δ
,Δ
By/Δ
,Δ
Bz/Δ
);
g) generating a scalar-quantity gradient contraction
for said pair of TMA sensors; and
h) repeating steps c)-g) for a second measurement location wherein said gradient contraction C2 changes monotonically with proximity to a magnetic target.
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17. A magnetic anomaly sensing system, comprising:
-
a support that is electrically non-conductive and non-magnetic;
four triaxial magnetometer-accelerometer (TMA) sensors coupled to said support, each of said four TMA sensors being positioned at a vertex of a planar square of side length S and having X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes that are parallel to one another and parallel to said X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes of all others of said TMA sensors, wherein each of said TMA sensors outputs X,Y,Z components (Bx,By,Bz) of local magnetic fields and X,Y,Z components (Ax,Ay,Az) of local gravitational acceleration fields;
means for processing said X,Y,Z components (Bx,By,Bz) and (Ax,Ay,Az) for each of said TMA sensors to generate motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) of local magnetic fields for each of said TMA sensors;
means for generating a difference between said motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) for pairs of said TMA sensors positioned on opposite sides of said planar square to generate differential vector field components (Δ
Bx,Δ
By,Δ
Bz) for each of said pairs;
means for generating gradient components Gi for each of said pairs using said differential vector field components (Δ
By,Δ
By,Δ
Bz) where i={X,Y,Z} and wherein, for each of said X,Y,Z magnetic sensing axes, said gradient components Gi are defined by (Δ
Bx/S,Δ
By/S,Δ
Bz/S);
means for generating a scalar-quantity gradient contraction
for each of said pairs; and
means for determining range and relative bearing to a magnetic target using values of said gradient contraction C2 for said pairs positioned on opposite sides of said planar square.
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19. A method for sensing magnetic anomalies, comprising the steps of:
-
a) providing a non-magnetic and electrically non-conductive support with four triaxial magnetometer-accelerometer (TMA) sensors coupled thereto, each of said TMA sensors being positioned at a vertex of a planar square of side length S and having X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes that are parallel to one another and parallel to said X,Y,Z magnetic sensing axes and X,Y,Z acceleration sensing axes of all others of said TMA sensors;
b) moving said non-magnetic support with said four TMA sensors coupled thereto to a measurement location wherein each of said TMA sensors outputs X,Y,Z components (Bx,By,Bz) of local magnetic fields and X,Y,Z components (Ax,Ay,Az) of local gravitational acceleration fields;
c) generating motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) of local magnetic fields for each of said TMA sensors using said X,Y,Z components (Bx,By,Bz) and (Ax,Ay,Az) for each of said TMA sensors;
d) generating a difference between said motion-compensated X,Y,Z components (Bcx,Bcy,Bcz) for pairs of TMA sensors positioned on opposite sides of said planar square to generate differential vector field components (Δ
Bx,Δ
By,Δ
Bz) for each of said pairs;
e) generating gradient components Gi for each of said pairs using said differential vector field components (Δ
Bx,Δ
By,Δ
Bz) where i={x,y,z} and wherein, for each of said X,Y,Z magnetic sensing axes, said gradient components Gi are defined by (Δ
Bx/Δ
,Δ
By/Δ
,Δ
Bz/Δ
);
f) generating a scalar-quantity gradient contraction
for each of said pairs of TMA sensors; and
g) repeating steps b)-f) for a second measurement location wherein said gradient contraction C2 changes monotonically with proximity to a magnetic target.
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Specification