Apparatus and method for locating and tracking magnetic objects or sources
First Claim
1. Magnetic locating apparatus comprising a pair of spaced gradiometers for producing output signals dependent upon the gradient of a magnetic field associated with a magnetic object to be located, means supporting the gradiometers for movement relative to the magnetic object to be located, and means responsive to the output signals for indicating the location of the magnetic object relative to the gradiometers along a coordinate axis irrespective of the magnetic field signature of the object.
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Accused Products
Abstract
At least one pair of vector gradiometers is employed to locate (and track) magnetic objects or sources. A first signal, S, is produced as a function of the difference in the absolute values of output signals L and R from left and right gradiometers, respectively. The form of the signal depends upon whether the magnetic field associated with the object or source is symmetric or anti-symmetric and is selected in accordance with observations made as the gradiometer pair passes over the magnetic object or source. A second signal, V, is produced as a function of the sum of the absolute values of signals L and R and represents total strength. A third signal, H=S/V, is produced to determine whether the observer is to the left or to the right of the magnetic object or source and is independent of the magnetic field strength and polarity of the magnetic field, even where the polarity and magnetic field strength vary with distance along a linear source. Compensation is employed for gradiometer sensor misalignment and temperature variations, and extraneous magnetic fields are nulled.
52 Citations
36 Claims
- 1. Magnetic locating apparatus comprising a pair of spaced gradiometers for producing output signals dependent upon the gradient of a magnetic field associated with a magnetic object to be located, means supporting the gradiometers for movement relative to the magnetic object to be located, and means responsive to the output signals for indicating the location of the magnetic object relative to the gradiometers along a coordinate axis irrespective of the magnetic field signature of the object.
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4. Magnetic locating apparatus comprising first and second pairs of spaced gradiometers for producing first and second output signals, respectively, dependent upon the gradient of a magnetic field associated with a magnetic object to be located, means supporting the gradiometers for movement relative to the magnetic object and such that the magnetic axes of the gradiometers of each pair are substantially parallel and such that each of the gradiometers of the second pair is located laterally relative to a corresponding gradiometer of the first pair, and means responsive to the first and second output signals from the first and second pairs of gradiometers for indicating the position of the magnetic object relative to the gradiometers along first and second coordinate axes irrespective of the magnetic field signature of the object.
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5. Magnetic locating apparatus comprising first and second pairs of spaced gradiometers for producing first and second output signals, respectively, dependent upon the gradient of a magnetic field associated with a magnetic object to be located, means supporting the gradiometers for movement relative to the magnetic object and such that the magnetic axes of the gradiometers of each pair are substantially parallel and such that the gradiometers of the second pair are located above or below the gradiometers of the first pair, and means responsive to the first and second output signals from the first and second pairs of gradiometers for indicating the position of the magnetic object relative to the gradiometers along first and second coordinate axes irrespective of the magnetic field signature of the object.
- 6. Magnetic locating apparatus comprising a pair of spaced gradiometers for producing output signals dependent upon the gradient of a magnetic field associated with a magnetic object to be located, each gradiometer having a pair of substantially aligned magnetic sensors and having temperature-corrected misalignment compensating means, means supporting the gradiometers for movement relative to the magnetic object to be located, and means responsive to the output signals for indicating the location of the magnetic object relative to the gradiometers along a coordinate axis irrespective of the magnetic field signature of the object.
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13. Magnetic locating apparatus comprising a pair of spaced gradiometers for producing output signals dependent upon the gradient of a magnetic field associated with a magnetic object to be located, means supporting the gradiometers for movement relative to the magnetic object to be located, and means responsive to the output signals comprising signal processing means having a pair of selectable operating modes, one of which is selected when the magnetic field associated with the object is principally symmetric and the other of which is selected when the magnetic field associated with the object is principally anti-symmetric, for indicating the location of the magnetic object relative to the gradiometers along a coordinate axis irrespective of the magnetic field signature of the object.
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14. Magnetic locating apparatus comprising a pair of spaced gradiometers for producing output signals dependent upon the gradient of a magnetic field associated with a magnetic object to be located, means supporting the gradiometers for movement relative to the magnetic object to be located, and means responsive to the output signals for indicating the location of the magnetic object relative to the gradiometers along a coordinate axis irrespective of the magnetic field signature of the object, wherein the means responsive to the output signals from the gradiometers produces a first signal, S, related to output signals L and R of the gradiometers, respectively, in accordance with one of the relationships:
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space="preserve" listing-type="equation">S=|L|.sup.n -|R|.sup.n and
space="preserve" listing-type="equation">S=sign (L) sign (R) [|L|.sup.n -|R|.sup.n ],a second signal, V, related to L and R in accordance with the relationship V=|L|n +|R|n, and produces a third signal, H, where H=S/V and n≧
0. - View Dependent Claims (15, 16, 17, 18)
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- 19. A method of locating a magnetic object which comprises providing a pair of gradiometers having substantially parallel magnetic axes, producing output signals L and R from the gradiometers in response to a magnetic field associated with the object, producing a signal V=|L|n +|R|n, producing a signal S=|L|n -|R|n or sign (L) sign (R) [|L|n -|R|n ] depending upon whether the magnetic field associated with the object is symmetric or antisymmetric, producing a signal H=S/V, and indicating, as a function of H, the position of the gradiometers relative to the object along a coordinate axis.
- 22. A method of locating a magnetic object which comprises providing a pair of gradiometers at spaced locations on a vehicle for producing output signals dependent upon the gradient of a magnetic field associated with the magnetic object, processing said output signals to produce an indication of the direction of the magnetic object from the vehicle along a coordinate axis, moving the vehicle in the direction indicated to approach the object, and controlling the processing so that the direction of the object relative to the vehicle is indicated irrespective of whether the magnetic field associated with the object is predominantly symmetric or anti-symmetric.
- 29. Magnetic locating apparatus comprising a pair of spaced gradiometers for producing output signals dependent upon the gradient of a magnetic field associated with an object carrying AC current of a predetermined frequency, means supporting the gradiometers for movement relative to the object, means for deriving output signals of said predetermined frequency from the gradiometers, and means responsive to the signals derived by the deriving means for indicating the location of the object relative to the gradiometers along a coordinate axis.
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35. Magnetic locating apparatus comprising a pair of spaced gradiometers for producing output signals dependent upon the gradient of a DC magnetic field associated with a linear object and the gradient of an AC magnetic field associated with an AC source of a predetermined frequency that moves along the linear object, and signal processing means for seperately processing output signals dependent upon the gradient of the DC magnetic field and output signals dependent upon the gradient of the AC magnetic field to enable simultaneous tracking of both the linear object and the AC source.
Specification