Data processing: measuring – calibrating – or testing – Calibration or correction system – Circuit tuning
Reexamination Certificate
2000-11-27
2003-04-08
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Circuit tuning
C702S034000, C702S038000, C702S104000, C700S028000, C700S032000, C700S033000, C324S200000, C324S207110, C324S207120
Reexamination Certificate
active
06546349
ABSTRACT:
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
BRIEF DESCRIPTION OF THE COMPUTER PROGRAM LISTING APPENDIX
Incorporated herein by reference is a computer program listing appendix setting forth an inventive embodiment of computer source code. This computer program listing appendix is contained as a text document which was created on Jan. 8, 2003 in a CD-R compact disc which is now situated in the application file. The CD-R compact disc contains one data file, 41 KB, in ASCII file format, entitled “uspto09721998computerprogramlistingappendix.”
BACKGROUND OF THE INVENTION
The present invention relates to reduction of the magnetic field of an object, more particularly to calibration pertaining to degaussing, and to methods and apparatuses for achieving same.
U.S. Naval combatants are equipped with systems of degaussing coils, the purpose of which is to compensate the magnetic field of the ship, thereby reducing the vessel's vulnerability to a mine threat. In order to perform effectively, it is necessary that a ship's degaussing coil system be calibrated.
The method currently used to calibrate a ship's degaussing coil system includes adjusting the electrical current flowing in each coil, and the number of turns in each coil, until the ship's peak vertical magnetic field, or signature, located at a beam's depth under the keel, has been reduced to a specified limit. This is accomplished by ranging the ship (e.g., at a “Magnetic Silencing Facility”) to determine it's existing magnetic field, consulting a handbook of coil effects and selecting the coil or coils which produce a magnetic peak nearest the peak in the ship's existing magnetic field, and adjusting the current and turns in that coil or coils to compensate for and reduce the peak in the ship's field. However, this method is limited to adjusting one or a few coils at a time, and becomes more difficult to implement as the number of coils in a degaussing system increases.
Another method for calibrating systems of degaussing coils has been used in the research model laboratory for over twenty years. This method includes performing a least-mean-squared-error (LMSE) fit of all of the model degaussing coil effects to the model ship's magnetic signature, using a computer. This method enables better magnetic signature reduction, as the impact of all coils in the system can be calculated and utilized at once. This computer-assisted “wholistic” approach has been used in the field recently and has met with success in reducing ship magnetic signatures to levels below that which is capable using the manual “coil-by-coil” approach described hereinabove. However, this method is limited to minimizing the average squared error between the ship signature (or signals derived from the ship signature) and a linear combination of the coil effects (or signals derived from the coil effects); it cannot be used, for example, to minimize the peak residual magnetic field signature.
Accordingly, there is a need for a degaussing coil methodology which can be efficiently implemented for practically any number of coils, and which is capable of achieving minimization of any signal derived from the degaussed signature—not merely minimization of the mean squared error between the undegaussed signature and the coil effects.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide method and apparatus for calibrating a system of degaussing coils located around or inside an entity (such as a ship), in order to reduce the magnetic field of the entity.
It is a further object of the present invention to provide such method and apparatus which admits of practical application with respect to large as well as small numbers of degaussing coils.
It is another object of the present invention to provide such method and apparatus which can be implemented so as minimize virtually any signal derived from the degaussed signature.
In accordance with the present invention, a method is provided for calibrating a degaussing system for application to an object having a magnetic field associated therewith. The degaussing system is of the kind including at least one coil (more typically, plural coils) for conducting electrical current and for being proximately (e.g., peripherally) disposed in relation to said object. The inventive method comprises: designating at least one optimization parameter pertaining to the magnetic signature of the object in a degaussed condition; defining a current vector (e.g., mathematical array) containing at least one current value wherein each coil corresponds to a (at least one, but typically one) current value; and, executing a genetic algorithm so as to identify a solution of the current vector wherein the application of at least one current value to (at least one coil in) the degaussing system tends to optimize at least one optimization parameter.
Further provided in accordance with the present invention is a computer program product which comprises a computer useable medium having computer program logic recorded thereon for enabling a computer to calibrate a degaussing system for application to an object having a magnetic field associated therewith. The degaussing system is of the type which includes at least one coil for conducting electrical current and for being proximately disposed in relation to the object. The computer program logic comprises: means for enabling the computer to designate at least one optimization parameter pertaining to the magnetic signature of the object in a degaussed condition; means for enabling the computer to define a current vector containing at least one current value wherein each coil corresponds to a current value; and, means for enabling the computer to execute a genetic algorithm so as to identify a solution of the current vector wherein the application of at least one current value to the degaussing system tends to optimize at least one optimization parameter.
Also provided according to the present invention is a machine having a memory, such as a computer (e.g., that which includes a processor). The machine contains a data representation of the calibration of a degaussing system for application to an object having a magnetic field associated therewith. The degaussing system is of the type which includes at least one coil for conducting electrical current and for being proximately disposed in relation to the object. The data representation is generated, for availability for containment by the machine, by the method comprising: designating at least one optimization parameter pertaining to the magnetic signature of the object in a degaussed condition; defining a current vector containing at least one current value wherein each coil corresponds to a current value; and, executing a genetic algorithm so as to identify a solution of the current vector wherein the application of at least one current value to the degaussing system tends to optimize at least one optimization parameter.
Further provided in accordance with the present invention is a method for degaussing an object having a magnetic field associated therewith. The inventive method comprises: proximately disposing at least one coil in relation to the object; calibrating at least one coil; and, causing at least one coil to conduct electrical current in accordance with the calibrating. The calibrating includes: designating at least one optimization parameter pertaining to the magnetic signature of the object in a degaussed condition; defining a current vector containing at least one current value wherein each coil corresponds to a current value; and, executing a genetic algorithm so as to identify a solution of the current vector wherein the effectuation of at least one current value tends to optimize at least one optimization parameter.
Also provided according to the present invention is
Powell Nevin D.
Tarr Paulo Bertell
Desta Elisa
Hoff Marc S.
Kaiser Howard
The United States of America as represented by the Secretary of
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