JP2011111085A - Method for deriving demagnetization coil combination of hull - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for deriving the demagnetization coil combination of a hull simulating the demagnetized state at an arbitrary adjusting surface or line when conducting each demagnetization coil to be selected among the demagnetization coils as candidates provided in the hull from the ship design stage without manufacturing any hull magnetic model, and deriving the combination of the demagnetization coils in which the hull external magnetic field at the adjusting surface or line is minimized. <P>SOLUTION: A numerical calculation model of a hull is prepared (ST1). A numerical calculation model of n-sets of candidate demagnetization coils C<SB>1</SB>-C<SB>n</SB>is prepared (ST2). An adjusting surface or line forming an object for demagnetization is set (ST3). The optimum demagnetization current in which the hull external magnetic field vector H<SB>F/D</SB>in a demagnetized state is minimized is identified by the optimum parameter search method for each of the combination (ST8) of m-sets of demagnetization coils among the n-sets of candidate demagnetization coils C<SB>1</SB>-C<SB>n</SB>(ST11). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention simulates a demagnetization state when each demagnetizing coil provided in a hull (for example, steel) of a magnetic body is energized, and derives a demagnetizing coil combination deriving method for a hull. About.

  The external magnetic field of a ship having a hull made of a magnetic material such as steel is roughly divided into a permanent magnetic field by the steel material itself and an induced magnetic field that is induced by the earth's magnetic field. Is forming.

  The degaussing coil installed in the hull to demagnetize these hull external magnetic fields generated from the ship cannot be changed in location after installation. Therefore, it is necessary to estimate the hull external magnetic field as accurately as possible from the design stage, and to determine the location of the degaussing coil that can demagnetize the hull external magnetic field most efficiently and effectively.

  Conventionally, in order to determine the location of the degaussing coil when designing a new ship, a hull magnetic model is manufactured, more than the number of candidate degaussing coils to be installed are installed in the model, the magnetic field around the model is measured, and the degaussing is performed. The demagnetizing effect in each of the coil combinations was examined, and the location of the degaussing coil to be actually installed was determined.

  In the above-described method, the production of the ship's magnetic model requires advanced techniques, high costs, and a long production period by craftsmen. Moreover, there is a limit to the number of candidate degaussing coils that can be installed in the hull magnetic model, and it is impossible to change the hull shape and the location of the degaussing coils as in an actual ship.

  Furthermore, in order to evaluate the effect of demagnetization, a large-scale magnetic field measurement device that measures the magnetic field around the magnetic model is required. It takes a lot of time. In addition, the demagnetization effect varies depending on the skill of the engineer, and the deviation of the demagnetized hull external magnetic field from the ideal value tends to be large.

  Furthermore, in the magnetic field measuring device, the position where the magnetic detector can be attached is limited. In order to use the measured value as it is for the adjustment of the demagnetizing current, The degaussing current cannot be adjusted for the external magnetic field of the hull.

  The present invention has been made in view of such a situation, and its purpose is to produce a demagnetizing coil selected from candidate demagnetizing coils to be provided in the hull without producing a hull magnetic model as in the prior art. The demagnetization state at any setting surface or settling line when energized can be simulated from the ship design stage, and thereby a demagnetizing coil combination that minimizes the hull external magnetic field at the setting surface or setting line can be obtained. It is an object of the present invention to provide a method for deriving a combination of degaussing coils of a hull that can be derived.

One embodiment of the present invention is a method for deriving a demagnetizing coil combination for a hull. This method
Creating a numerical model of the hull;
Creating a numerical calculation model of n degaussing coils that are candidates for provision in the hull;
Setting an adjustment surface or adjustment line to be demagnetized;
Estimating a hull external magnetic field when each demagnetizing coil is not energized on the setting surface or setting line by a numerical simulation method;
Estimating each degaussing coil effect magnetic field, which is a magnetic field per unit current generated by each degaussing coil, in the setting surface or setting line by a numerical simulation method;
Selecting m (m <n) from the n degaussing coils;
Identifying a demagnetizing current value at which the hull external magnetic field at the time of energization of the selected m degaussing coils on the settling surface or settling line is minimized using an optimum parameter search method,
The selecting step and the specifying step are executed a plurality of times by changing the combination of m demagnetizing coils, and the hull external magnetic field when m demagnetizing coils are energized on the setting surface or setting line is the smallest. It is characterized by deriving a combination of m degaussing coils.

In an aspect of the method, the selecting step and the identifying step may be performed a total of _n C _m times.

  In a certain aspect of the method, the n degaussing coils may be divided into a plurality of groups, and in the selecting step, a predetermined number of m degaussing coils may be selected from each group.

  In the method of an embodiment, the numerical simulation method may be an integral equation method.

  In a certain aspect of the method, the numerical simulation method may be a finite element method.

  In the method of an embodiment, the optimal parameter search method may be a genetic algorithm.

  In the method of an embodiment, the optimum parameter search method may be a steepest descent method.

  In a method according to an aspect, the optimum parameter search method may be an annealing method.

  In the method according to an aspect, the optimum parameter search method may be a least square method.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between systems and programs are also effective as an aspect of the present invention.

  According to the present invention, a numerical calculation model of a candidate degaussing coil is created, a setting surface or a setting line to be degaussed is set, and a combination of a plurality of patterns of degaussing coils is selected from the candidate degaussing coils. Since the optimum demagnetizing current value is specified by the optimum parameter search method for each combination, any demagnetizing coil provided in the hull is energized without producing a hull magnetic model as in the past. Demagnetization state on the setting surface or the setting line can be simulated from the ship design stage, thereby finally deriving a combination of degaussing coils that minimizes the hull external magnetic field on the setting surface or setting line. Is possible.

Explanatory drawing of the procedure of the degaussing coil combination derivation method of the hull which concerns on embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, process, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 1 is a procedure explanatory diagram of a demagnetizing coil combination deriving method for a hull according to an embodiment of the present invention. The following steps are basically realized by the cooperation of a computer and software.

First, a ship three-dimensional calculation model corresponding to a numerical simulation method such as an integral equation method or a finite element method is created (ST1). In addition, a numerical calculation model of _n candidate degaussing coils C _{1 to} C _n which is larger than the actual number of installations is created (ST2). Next, a setting surface or a setting line to be demagnetized is set (ST3). It should be noted that this adjustment surface or adjustment line can be arbitrarily set not only at the lower part of the hull, but also at the upper part, front part, rear part, right part, left part and others. Subsequently, by a numerical simulation method such as an integral equation method or a finite element method, the hull external magnetic field vector H _{N / D} when each demagnetizing coil is not energized (non-demagnetized state) on the setting surface or setting line set in ST3 is obtained. Estimate and calculate (ST4). Similarly, each demagnetizing coil effect magnetic field vector H _{C1 to} H _Cn that is a magnetic field per unit current generated by each degaussing coil on the adjustment surface or adjustment line is estimated and calculated by numerical simulation (ST5).

Then, setting the number m of degaussing coils to choose from among the candidate demagnetizing coils C ₁ -C _n of n the (ST6). At this time, as a matter of course, the number m of selective degaussing coils is less than the number n of candidate degaussing coils. _Further , an initial value K is substituted into a variable _{HF / D_MIN} for storing an estimated calculation value of the hull external magnetic field vector _{HF / D} when the selected m number of degaussing coils are energized (demagnetization state) (ST7). The initial value K is an arbitrary value larger than the estimated calculation value of the hull external magnetic field vector H _{F / D} obtained in the steps described later.

となる。 Subsequently, a combination of m degaussing coils selected from the n candidate degaussing coils is set (ST8). Incidentally, the total number of combinations is _n C _m . Here, assuming that the current values of the n degaussing coils are i _{C1 to} i _Cn , the hull exterior at the time of energization (demagnetization state) of the selected m degaussing coils on the setting surface or setting line set in ST3, respectively. The magnetic field vector H _{F / D} is

It becomes.

Thereafter, m current values i _Cm that minimize the hull external magnetic field vector H _{F / D in the} demagnetized state expressed by Equation 1 above are calculated using a genetic algorithm (GA: Genetic Algorithm), steepest descent method, annealing method, minimum It is obtained by an optimum parameter search method such as a square method. Since all of them are known techniques, a detailed description thereof is omitted, but here, an example of adaptation when the steepest descent method is used will be described as an example.

First, each current value i _Cm of m degaussing coils is provisionally set (ST9). Next, the demagnetized hull external magnetic field vector H _{F / D} at the temporarily set current value is calculated by Equation 1 (ST10). When, for example, the maximum value of the demagnetized hull external magnetic field vector HF _{/ D} is memorized, the current value of each degaussing coil is changed little by little until the value gradually decreases and finally converges. The demagnetizing current value becomes the optimum demagnetizing current value, and the optimum demagnetizing current value and the demagnetized hull external magnetic field vector HF _{/ D} in the combination of the m degaussing coils selected in ST8 are specified (ST11). Note that the hull external magnetic field vector HF _{/ D} is the minimum, for example, set in ST3, which is one of the x component, y component or z component of the hull external magnetic field vector HF _{/ D} , or the mean square of these three components. It means that the average value or the maximum value on the settling surface or the setting line is the minimum.

Then, when an _{H F / D <H F /} D_MIN In ST12, substituting H _{F / D} to H F _{/ D_MIN} (ST13), combined with optimal demagnetizing current value of the degaussing coils of the m at that time Is stored (ST14). Next, it is determined whether optimum demagnetizing current values have been calculated for all combinations of degaussing coils (ST15). If there is an uncalculated combination, ST8 to ST15 are performed again. A combination of m demagnetizing coils having the smallest _{HF / D,} the optimum demagnetizing current value at that time, and the hull external magnetic field vector HF _{/ D} are output (ST17).

Regarding the estimation calculation of the non-demagnetized hull external magnetic field vector H _{N / D} in ST4, a numerical analysis model such as the integral equation method or the finite element method creates a numerical calculation model of the hull and applies geomagnetism to the hull. While it is possible to calculate the induced magnetism due to, the problem is how to calculate the permanent magnetism of the hull. However, in reality, the hull is demagnetized to remove permanent magnetism (a number of hull windings are attached to the hull, and the current polarity is changed to positive and negative while the current is gradually reduced to energize the hull. (That is, demagnetization processing (applying a magnetic field)) is performed, so that the hull external magnetic field vector H _{N / D} can be estimated and calculated with the permanent magnetism of the hull being zero. Alternatively, the residual permanent magnetism after the demagnetization process may be estimated and calculated by simulation, and the calculated value may be used as the value of the permanent magnetism of the hull to estimate and calculate the hull external magnetic field vector H _{N / D.}

  According to the present embodiment, the following effects can be achieved.

(1) Create a numerical model of the hull, creating a numerical model of the candidate demagnetizing coils C ₁ -C _n of the n sets the tone Teimen or tone constant linear as a degaussing subject, the n candidates The optimum demagnetizing current value that minimizes the hull external magnetic field vector H _{F / D in the} demagnetized state is specified by the optimum parameter search method for all combinations of the m degaussing coils in the degaussing coils C _{1 to} C _n. The demagnetization state at any setting surface or setting line when energizing each degaussing coil provided in the hull can be simulated from the ship design stage by a computer without producing a hull magnetic model as shown in FIG. Finally, the combination of m demagnetizing coils with the smallest hull external magnetic field vector H _{F / D on the} setting surface or setting line, the optimum demagnetizing current value in that case, and the degaussed hull external magnetic field vector H _{F / D} can be derived.

(2) In determining (calculating) the location of the degaussing coil, it is easier to create a hull numerical calculation model than to make a hull magnetic model if there is a design drawing of the hull. Therefore, it is possible to save time and cost for determining the position of the demagnetizing coil without requiring high technology, high cost and long production period by the craftsman for manufacturing the hull magnetic model.

(3) There is no theoretical limit on the number of candidate degaussing coils, and it is easy to change the shape of the hull numerical calculation model and the arrangement of candidate degaussing coils.

(4) In the evaluation of the demagnetization effect, the demagnetization current setting is completely automated, and the demagnetization current setting work of the degaussing coil in the ship's magnetic model is unnecessary, so the time is shortened and anyone can use it easily regardless of skill In addition, various degaussing coil arrangements can be tried in a short time. Moreover, if the model of the candidate degaussing coil is the same, there will be no difference in the degaussing effect depending on the skill of the engineer. Furthermore, a large-scale magnetic field measuring device is not necessary for evaluating the effect of demagnetization.

(5) Due to the computer simulation, it is possible to adjust the degaussing current for deeper hull external magnetic fields and upper or side hull external magnetic fields.

  The present invention has been described above by taking the embodiment as an example. However, it is understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiment within the scope of the claims. By the way. Hereinafter, modifications will be described.

As described in the embodiment, the total number of combinations of m degaussing coils selected from _n candidate degaussing coils C _{1 to} C _n is _n C _m , but in the modification, candidate degaussing coils C _{1 to} C are selected. _n may be divided into a plurality of groups to reduce the number of combinations. For example, each group of degaussing coils that generate a magnetic field in the tail line direction, lateral direction, and vertical direction that lays over the entire hull, and degaussing coils that are laid to demagnetize a local external magnetic field near the bow, etc. A total of m degaussing coils may be selected from each group by a predetermined number.

C _{1 to} C _n degaussing coil i _{C1 to} i _Cn demagnetizing current value H _{C1 to} H _Cn degaussing coil effect magnetic field vector H _{N / D} hull external magnetic field vector (non-degaussing state)
HF _{/ D} hull external magnetic field vector (demagnetized state)

Claims (9)

Creating a numerical model of the hull;
Creating a numerical calculation model of n degaussing coils that are candidates for provision in the hull;
Setting an adjustment surface or adjustment line to be demagnetized;
Estimating a hull external magnetic field when each demagnetizing coil is not energized on the setting surface or setting line by a numerical simulation method;
Estimating each degaussing coil effect magnetic field, which is a magnetic field per unit current generated by each degaussing coil, in the setting surface or setting line by a numerical simulation method;
Selecting m (m <n) from the n degaussing coils;
Identifying a demagnetizing current value at which the hull external magnetic field at the time of energization of the selected m degaussing coils on the settling surface or settling line is minimized using an optimum parameter search method,
The selecting step and the specifying step are executed a plurality of times by changing the combination of m demagnetizing coils, and the hull external magnetic field when m demagnetizing coils are energized on the setting surface or setting line is the smallest. A demagnetizing coil combination deriving method for a hull, characterized by deriving a combination of m degaussing coils. The method according to claim 1, wherein the selecting step and the specifying step are executed a total of _n C _m times.   The method according to claim 1, wherein the n degaussing coils are divided into a plurality of groups, and in the selecting step, a predetermined number of m degaussing coils are selected from each group in total. .   4. The method according to claim 1, wherein the numerical simulation method is an integral equation method.   4. The method according to claim 1, wherein the numerical simulation method is a finite element method.   6. A method according to claim 1, wherein the optimum parameter search method is a genetic algorithm.   6. The method according to claim 1, wherein the optimum parameter search method is a steepest descent method.   6. The method according to claim 1, wherein the optimum parameter search method is an annealing method.   6. The method according to claim 1, wherein the optimum parameter search method is a least square method.

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