Magnetic anomaly sensing system and methods for maneuverable sensing platforms

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 (ΔBx, ΔBy, ΔBz);
• generating gradient components Gij using said differential vector field components (ΔBx, ΔBy, ΔBz) 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 (ΔBx/Δj, ΔBy/Δj, ΔBz/Δj) wherein Δj 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 C 2 = ∑ i , j ⁢ ⁢ ( G ij ) 2
• for each said pair of TMA sensors wherein said gradient contraction C2 changes monotonically with proximity to a magnetic target.

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 (ΔBx, ΔBy, ΔBz);
• means for generating gradient components Gi using said differential vector field components (ΔBx, ΔBy, ΔBz) where i={x, y, z} and wherein, for each of said X, Y, Z magnetic sensing axes, said gradient components Gi are defined by (ΔBx/Δ, ΔBy/Δ, ΔBz/66 );
• and
• means for generating a scalar-quantity gradient contraction C 2 = ∑ i ⁢ ⁢ ( G i ) 2
• for said pair of TMA sensors wherein said gradient contraction C2 changes monotonically with proximity to a magnetic target.

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 (ΔBx, ΔBy, ΔBz);
• f) generating gradient components Gj using said differential vector field components (ΔBx, ΔBy1 ΔBz) where i={x, y, z} and wherein, for each of said X, Y, Z magnetic sensing axes, said gradient components Gi are defined by (ΔBx/Δ, ΔBy/Δ, ΔBz/Δ);
• g) generating a scalar-quantity gradient contraction C 2 = ∑ i ⁢ ⁢ ( G i ) 2
• 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.

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 (ΔBx, ΔBy, ΔBz) for each of said pairs;
• means for generating gradient components Gi for each of said pairs using said differential vector field components (ΔBx, ΔBy, ΔBz) where i={x, y, z} and wherein, for each of said X, Y, Z magnetic sensing axes, said gradient components G, are defined by (ΔBx/S, ΔBy/S, ΔBz/S);
• means for generating a scalar-quantity gradient contraction C 2 = ∑ i ⁢ ⁢ ( G i ) 2
• 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.

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 (ΔBx, ΔBy, ΔBz) for each of said pairs;
• e) generating gradient components Gi for each of said pairs using said differential vector field components (ΔBx, ΔBy, ΔBz) where i=(x, y, z) and wherein, for each of said X, Y, Z magnetic sensing axes, said gradient components Gj are defined by (ΔBx/Δ, ΔBy/Δ, ΔBz/Δ);
• f) generating a scalar-quantity gradient contraction C 2 = ∑ i ⁢ ⁢ ( G i ) 2
• 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.