CN107092001B - Ship induced magnetic field measurement method based on surface subdivision and magnetic field mapping between measuring points - Google Patents

Ship induced magnetic field measurement method based on surface subdivision and magnetic field mapping between measuring points Download PDF

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CN107092001B
CN107092001B CN201710360922.7A CN201710360922A CN107092001B CN 107092001 B CN107092001 B CN 107092001B CN 201710360922 A CN201710360922 A CN 201710360922A CN 107092001 B CN107092001 B CN 107092001B
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ship
coil
generated
unit
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CN107092001A (en
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刘胜道
周国华
陈瀚斯
赵文春
高俊吉
李志新
郭成豹
刘月林
吴轲娜
张明
田东
张树
朱武兵
周炜昶
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Naval University of Engineering PLA
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    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract

The invention discloses a ship induction magnetic field measurement method based on a magnetic field mapping relation between a surface subdivision unit and a measuring point, which comprises the following steps: selecting a closed surface capable of enclosing a ship, dividing the closed surface into a plurality of surface units, and setting the center of the closed surface as a calculation point; setting the coil currents and combining the magnetic fields generated by the computation points into a matrix Be(ii) a Before the ship enters the degaussing station, collecting the magnetic field of each sensor measuring point and recording as Bbj(ii) a Sequentially electrifying the coils according to the set current, collecting the magnetic field again and turning BbjSubtract to obtain Bc0(ii) a After the ship enters the degaussing station, collecting the magnetic field and converting B into BbjSubtract to obtain Bship(ii) a Sequentially electrifying the coils according to the set current, collecting the magnetic field again and turning BbjAnd BshipSubtract to obtain Bc1(ii) a With Bc1Minus the corresponding Bc0To obtain Bc(ii) a According to CoeK Be=BcThus, CoeK can be obtained, and the corresponding induced magnetic field of the ship can be obtained. The invention has the beneficial effects that: the accuracy and the efficiency of the ship induction magnetic field measurement are improved, and a large amount of manpower and material resources are saved.

Description

Ship induced magnetic field measurement method based on surface subdivision and magnetic field mapping between measuring points
Technical Field
The invention relates to the technical field of ship demagnetization, in particular to a ship induction magnetic field measuring method.
Background
The magnetic field of the ship generally refers to the magnetic field generated by the ship in the surrounding space, and is the main physical field for various magnetic detection devices and weapons in water to detect and attack. In order to resist the attack of magnetic weapons in water and the magnetic detection in the air, magnetic protection measures must be implemented on ships, and accurate control of ship induction magnetic fields is an important prerequisite for implementing the magnetic protection measures. The ship induced magnetic field can be obtained by a 2-class method: numerical calculation methods and magnetic field measurement methods. Common numerical calculation methods for calculating the ship induction magnetic field include a finite element method, an integral equation method and the like, but the precision of a numerical calculation result is difficult to guarantee at present due to the factors that the ship structure is complex, parameters of various magnetic materials are difficult to accurately obtain and the like. Two common methods for obtaining the ship induction magnetic field in the magnetic field measurement method are a double-course method (only longitudinal and transverse induction magnetic fields can be obtained) + two-place measurement method (only vertical induction magnetic field can be obtained) and a geomagnetic simulation method (longitudinal, transverse and vertical induction magnetic fields can be obtained). When the double-course method is used for measuring the ship induction magnetic field, the process of changing course when the ship enters and exits is time-consuming and labor-consuming due to the large size and special shape of the ship and the narrow entrance and channel of the degaussing station; in addition, the berthing position of the ship is easy to change after the ship is changed to navigate, and the corresponding magnetic field measurement position coordinate is difficult to ensure to be fixed, so certain measurement error can be caused. The vertical induced magnetic field of the ship can be obtained by two-place measurement method in theory, but actually, the method is not feasible in practice and precision because the magnetic state of the ship during long-distance navigation at two latitudes can not be guaranteed to be unchanged and the technical indexes of the two-place magnetic field measurement system are consistent. In the conventional geomagnetic simulation method, a local geomagnetic field is changed by electrifying a geomagnetic simulation coil (or a geomagnetic compensation coil) of a degaussing station, and a ship induction magnetic field is calculated according to the change of the ship magnetic field before and after electrification. The method can avoid the waste of manpower and material resources caused by turning the course and measuring the course in two places, and can obviously shorten the acquisition time of the induction magnetic field, however, the accuracy of the induction magnetic field acquired by applying the method is highly related to the uniformity of the simulated geomagnetic field. Due to the limitation of various factors, the magnetic field generated by the compensation coil of the degaussing station cannot reach the ideal uniformity, and the larger the ship is, the worse the uniformity is, so that the precision of the measured induced magnetic field cannot be ensured, and the popularization and the use of the geomagnetic simulation method are greatly limited.
Disclosure of Invention
Aiming at the technical problems in the related art, the invention provides a ship induced magnetic field measurement method based on a magnetic field mapping relation between a surface subdivision unit and a measurement point.
In order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows:
a ship induced magnetic field measurement method based on a magnetic field mapping relation between a surface subdivision unit and a measurement point comprises the following steps:
s1: selecting a closed surface capable of enclosing a ship, carrying out mesh unit subdivision on the closed surface, and taking the center of each surface unit as a calculation point;
s2: the degaussing stations are respectively provided with a plurality of groups of longitudinal coils, transverse coils and vertical coils for compensating the geomagnetic fieldWherein, assuming that X groups of longitudinal coils (X01, X02, …, X0X), Y groups of transverse coils (Y01, Y02, …, Y0Y) and Z groups of vertical coils (Z01, Z02, …, Z0Z) are laid, wherein X, Y and Z are positive integers, setting each coil current and calculating the magnetic field generated by each coil at the calculation point, and respectively marking as BeX01、BeX02、…、BeX0x、BeY01、BeY02、…、BeY0y、BeZ01、BeZ02、…、BeZ0zCombining these magnetic fields into a matrix BeThe magnetic field matrix generated by each coil on each surface unit;
s3: before the ship enters the degaussing station, collecting the magnetic field of each sensor measuring point and recording as Bbj；
S4: before the ship enters the degaussing station, the coil currents set in S2 are electrified in sequence, the magnetic fields at the measuring points of the sensors are collected, and B is usedbjThe results of the subtraction are respectively denoted as Bc0X01、Bc0X02、…、Bc0X0x、Bc0Y01、Bc0Y02、…、Bc0Y0y、Bc0Z01、Bc0Z02、…、Bc0Z0zWherein x, y and z are positive integers;
s5: after the ship enters the degaussing station, collecting the magnetic field of each sensor measuring point, and detecting BbjSubtract, the result is recorded as Bship；
S6: after the ship enters the degaussing station, the coil currents set in the step S2 are sequentially electrified, the magnetic field of each sensor measuring point is collected, and BbjAnd BshipThe results of the subtraction are respectively denoted as Bc1X01、Bc1X02、…、Bc1X0x、Bc1Y01、Bc1Y02、…、Bc1Y0y、Bc1Z01、Bc1Z02、…、Bc1Z0zWherein x, y and z are positive integers;
s7: with Bc1X01Minus the corresponding Bc0X01Obtaining a ship magnetic field B under the action of the energizing magnetic field of the coil X01cX01(ii) a By the same method, B can be obtainedcX02、…、BcX0x、BcY01、BcY02、…、BcY0y、BcZ01、BcZ02、…、BcZ0zWhere x, y, z are positive integers, combining these magnetic fields into a matrix BcNamely a magnetic field matrix generated by the ship under the action of the magnetic field of each coil;
s8: using a matrix BeAnd BcThe relation between them establishes a matrix equation CoeK Be＝BcWhere CoeK is a relationship matrix, now BeAnd BcAre all known, so that CoeK can be obtained by solving;
s9: setting the longitudinal component of the magnetic field of each surface unit calculation point as the magnetic field component value of the local geomagnetic field along the longitudinal direction of the ship, setting the other components as 0, and multiplying the components by CoeK to obtain the longitudinal induction magnetic field of the ship; and in the same way, a transverse induction magnetic field and a vertical induction magnetic field of the ship can be obtained.
The invention has the beneficial effects that:
the ship is magnetized by utilizing the magnetic fields generated by the existing geomagnetic compensation coils of each group of the degaussing station, the induced magnetic field of the ship under the action of the local geomagnetic field is obtained through measurement, analysis and calculation, the mapping relation between the magnetic field matrix generated by each coil on each surface unit and the magnetic field matrix generated by the ship under the action of the magnetic field of each coil is mainly utilized, and the induced magnetic field of the ship can be obtained through the mapping relation.
Compared with the prior art, the method has the advantages that the requirement on the uniformity of the magnetic field generated by the geomagnetic compensation coil is not required, so that the method can not only improve the precision and efficiency of the measurement of the ship induction magnetic field and save a large amount of manpower and material resources, but also can be widely popularized and used in the existing degaussing stations. If the method is applied to the design and construction of a new degaussing station, the construction cost is obviously saved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic diagram of a ship induced magnetic field measurement method based on a magnetic field mapping relationship between a surface subdivision unit and a measurement point according to an embodiment of the invention;
FIG. 2 is a schematic view of a longitudinal coil;
FIG. 3 is a schematic view of a transverse coil;
FIG. 4 is a schematic view of a vertical coil;
in the figure: 1-calculating a point; 2-face unit; 3-magnetic sensor array.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.
The ship induction magnetic field measurement method based on the magnetic field mapping relation between the surface subdivision unit and the measuring point comprises the following steps:
step 1): as shown in fig. 1, a closed surface is selected that encloses the vessel. Without loss of generality, a cuboid surface slightly larger than the size of the ship is selected, the ship is positioned in the cuboid surface, and the center of the cuboid surface is coincided with the center of the cuboid. And dividing the surface of the cuboid into m surface units, and taking the center of each surface unit as a calculation point, wherein the number of the calculation points is m.
Step 2): without loss of generality, assume that a degaussing station is provided with 3 sets of longitudinal coils (X01, X02, X03), 4 sets of transverse coils (Y01, Y02, Y03, Y04) and 5 sets of vertical coils (Z01, Z02, Z03, Z04, Z05), and 12 sets of coils are provided, and the coil diagrams are respectively shown in fig. 2, fig. 3 and fig. 4. Taking coil X01 as an example, assume that current I is passed through the coilX01The magnetic field generated by coil X01 at the above m calculation points can be calculated according to Biao-Saval theorem, and is marked as BeX01. By the same method, B can be obtainedeX02、BeX03、BeY01、BeY02、BeY03、BeY04、BeZ01、BeZ02、BeZ03、BeZ04、BeZ05Combining these magnetic fields into a matrix BeIt is called the magnetic field matrix generated by each coil on each surface unit.
Step 3): in order to measure the magnetic field of the ship, a magnetic sensor array as shown in fig. 1 is arranged in the degaussing station, and the number of the magnetic sensors is assumed to be n. Before the ship enters the degaussing station, the magnetic field measured by each magnetic sensor is collected and recorded as Bbj。
Step 4): before the ship enters the degaussing station, taking coil X01 as an example, assume that current I is passed through the coilX01Collecting the magnetic field measured by each magnetic sensor and comparing BbjSubtract, the result is recorded as Bc0X01. By the same method, B can be obtainedc0X02、Bc0X03、Bc0Y01、Bc0Y02、Bc0Y03、Bc0Y04、Bc0Z01、Bc0Z02、Bc0Z03、Bc0Z04、Bc0Z05。
Step 5): after the ship enters the degaussing station, collecting the magnetic field measured by each magnetic sensor, and comparing BbjSubtract, the result is recorded as Bship。
Step 6): after the ship enters the degaussing station, taking coil X01 as an example, assume that current I is passed through the coilX01Collecting the magnetic field measured by each magnetic sensor and comparing BbjAnd BshipSubtract, the result is recorded as Bc1X01. By the same method, B can be obtainedc1X02、Bc1X03、Bc1Y01、Bc1Y02、Bc1Y03、Bc1Y04、Bc1Z01、Bc1Z02、Bc1Z03、Bc1Z04、Bc1Z05。
Step 7): with Bc1X01Minus the corresponding Bc0X01Obtaining a ship magnetic field B under the action of the energizing magnetic field of the coil X01cX01(ii) a By the same method, B can be obtainedcX02、BcX03、BcY01、BcY02、BcY03、BcY04、BcZ01、BcZ02、BcZ03、BcZ04、BcZ05Combining these magnetic fields into a matrix BcThe magnetic field matrix is called a magnetic field matrix generated by the ship under the action of the magnetic field of each coil;
step 8): ferromagnetic objects (such as ships with steel structures) are magnetized by external magnetic fields (such as geomagnetic fields or coil magnetic fields) and then any field point P (x) in the surrounding spaceP,yP,zP) The generated magnetic field BPCan be expressed as:
Figure BDA0001299822720000061
in the formula: v is the volume occupied by the ferromagnetic object; m (r)Q) An additional magnetization generated inside the ferromagnetic object for an external magnetic field; r ispField point vector is used; r isQIs the source point vector; r ispQ＝rp-rQ；Bp(rp) Is rpProcessing a column vector consisting of three component values of the magnetic field intensity;
Figure BDA0001299822720000062
performing gradient calculation on the source point coordinates;
Figure BDA0001299822720000063
to perform a gradient calculation on the field point coordinates.
If the unit subdivision is performed on a ferromagnetic object, the integration in equation (1) will be transformed into a summation. For a linear material ferromagnetic object or a homogeneous ferromagnetic object, equation (1) will ultimately form a system of linear equations:
C·M＝B (2)
in the formula: m is the additional magnetization intensity generated by the external magnetic field in each unit in the ferromagnetic object; c is a subdivision unit coupling coefficient matrix; and B is a column vector formed by the magnetic fields generated by the external magnetic field in each unit in the ferromagnetic object.
According to the Biao-Saval theorem, the magnetic field generated by the current element is as follows:
Figure BDA0001299822720000064
in the formula: dl is a current element, and the current flowing through the current element is I; r is the radius from the field point to the current element, and the length of r; dh is the magnetic field generated by the current element at the field point.
The electrified coil is split into a plurality of small current elements, and the magnetic field generated by the coil can be obtained by superposing the magnetic fields generated by the current elements. Under the condition that the relative position of the coil and the ferromagnetic object is fixed and unchanged, the relationship between the magnetic field generated by each unit of the coil in the ferromagnetic object and the current I is as follows:
C1·I＝B (4)
in the formula: c1The coefficient matrix is determined by the position relationship between each current element and each unit in the ferromagnetic object.
Similarly, under the condition that the relative position of the coil and the surface of the rectangular solid is fixed and unchanged as shown in fig. 1, the relationship between the magnetic field generated by the coil in each unit of the surface of the rectangular solid and the current I is as follows:
C2·I＝Be(5)
in the formula: c2The coefficient matrix is determined by the position relationship between each current element and each unit on the surface of the cuboid.
From formulas (4) and (5):
Figure BDA0001299822720000071
formula (6) is substituted for formula (2) to obtain:
Figure BDA0001299822720000072
the formula (7) relates the additional magnetization intensity generated by each unit in the ferromagnetic object and the magnetic field generated by each unit on the surface of the cuboid by the coil.
Assuming that the additional magnetization M generated by the units inside the ferromagnetic object when a coil of the degaussing station is energized1Then, it can be obtained from equation (7):
Figure BDA0001299822720000073
in the formula:Be1the magnetic field generated by the coil on each unit of the surface of the cuboid.
Corresponding by M1The generated measuring point magnetic field is as follows:
C3·M1＝Bc1(9)
the combination of formula (8) and formula (9) gives:
Figure BDA0001299822720000074
order to
Figure BDA0001299822720000075
Combining the magnetic fields generated by the coils of the degaussing station at the computation points of the surface unit into a matrix BeThe ship magnetic fields excited by the magnetic fields of the coils at the measuring point of the magnetic sensor are combined into a matrix BcThen, there are:
CoeK·Be＝Bc(11)
the conclusion can be drawn from equation (11): a mapping relation exists between the magnetic field generated by the coil at each calculation point of the surface unit and the ship magnetic field excited by the coil magnetic field at the measurement point, and the induced magnetic field of the ship under the action of any geomagnetic field can be solved as long as the mapping relation is obtained.
In the formula (11) BeAnd BcAre known quantities, and therefore can be solved to obtain the CoeK:
Figure BDA0001299822720000081
step 9): setting the longitudinal component of the magnetic field of each surface unit calculation point as the magnetic field component value of the local geomagnetic field along the longitudinal direction of the ship, setting the other components as 0, and multiplying the components by CoeK to obtain the longitudinal induction magnetic field of the ship; and in the same way, a transverse induction magnetic field and a vertical induction magnetic field of the ship can be obtained. The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (4)

1. A ship induced magnetic field measurement method based on a magnetic field mapping relation between a surface subdivision unit and a measurement point is characterized by comprising the following steps:
s1: selecting a closed surface capable of enclosing a ship, wherein the closed surface is a cuboid surface, the ship is a ferromagnetic object, the ship is positioned in the closed surface, and the closed surface is subjected to meshing division into a plurality of groups
Figure FDA00023663485900000129
A face unit, taking the center of each face unit as a calculation point;
s2: the degaussing stations are all provided with a plurality of groups of longitudinal coils, transverse coils and vertical coils, wherein x groups of longitudinal coils are arranged
Figure FDA00023663485900000125
Figure FDA00023663485900000126
Set of transverse coils
Figure FDA00023663485900000127
And z sets of vertical coils
Figure FDA00023663485900000128
Wherein
Figure FDA00023663485900000130
Setting the current of each coil as a positive integer, calculating the magnetic field generated by each coil at the calculation point, combining the magnetic fields into a magnetic field matrix generated by each coil at each surface unit
Figure FDA0002366348590000011
S3: before a ship does not enter a degaussing station, collecting the magnetic field of each sensor measuring point of a magnetic sensor array distributed in the degaussing station
Figure FDA0002366348590000012
S4: before the ship enters the degaussing station, the coil currents set in the step S2 are electrified in sequence, the magnetic fields at the measuring points of the magnetic sensors are collected, and the magnetic fields are transmitted
Figure FDA0002366348590000013
The results of subtraction are respectively recorded as
Figure FDA0002366348590000014
Figure FDA0002366348590000015
Wherein
Figure FDA00023663485900000131
Is a positive integer;
s5: after the ship enters the degaussing station, collecting the magnetic field of each sensor measuring point of the sensor array arranged in the degaussing station, and collecting the magnetic field
Figure FDA0002366348590000016
Subtract, the result is recorded as
Figure FDA0002366348590000017
S6: after the ship enters the degaussing station, the coil currents set in the step S2 are sequentially electrified, the magnetic field at the measuring point of each sensor is collected, and the magnetic field is measured
Figure FDA0002366348590000018
And
Figure FDA0002366348590000019
the results of subtraction are respectively recorded as
Figure FDA00023663485900000110
Figure FDA00023663485900000111
Wherein
Figure FDA00023663485900000132
Is a positive integer;
s7: by using
Figure FDA00023663485900000112
Minus the corresponding
Figure FDA00023663485900000113
Obtained in a coil
Figure FDA00023663485900000114
Ship magnetic field under action of electrified magnetic field
Figure FDA00023663485900000115
By the same token can obtain
Figure FDA00023663485900000116
Figure FDA00023663485900000117
Wherein
Figure FDA00023663485900000133
For positive integers, combining these fields into a matrix
Figure FDA00023663485900000118
Namely a magnetic field matrix generated by the ship under the action of the magnetic field of each coil;
s8: using matrices
Figure FDA00023663485900000119
And
Figure FDA00023663485900000120
the relation between them establishes a matrix equation
Figure FDA00023663485900000121
Is a relationship matrix, now
Figure FDA00023663485900000122
And
Figure FDA00023663485900000123
are all known, and therefore solved for
Figure FDA00023663485900000124
S9: setting the longitudinal component of the magnetic field of each calculation point of each surface unit as the value of the magnetic field component of the local geomagnetic field along the longitudinal direction of the ship, setting the other components as 0, and
Figure FDA0002366348590000022
multiplying to obtain a longitudinal induction magnetic field of the ship; and similarly, obtaining a transverse induction magnetic field and a vertical induction magnetic field of the ship.
2. The method for measuring the induced magnetic field of a ship based on the magnetic field mapping relationship between the surface subdivision unit and the measuring points as claimed in claim 1, wherein in step S2, the coil positions of the coils are calculated according to the Biao-savart theorem
Figure FDA00023663485900000218
The magnetic field generated by each point is calculated.
3. The method for measuring the induced magnetic field of the ship based on the magnetic field mapping relationship between the surface subdivision unit and the measuring point as claimed in claim 2, wherein in the step S3, the number of the magnetic sensors is
Figure FDA00023663485900000219
Before a ship enters a degaussing station, collecting magnetic fields measured by each magnetic sensor
Figure FDA0002366348590000023
4. The method of claim 3, wherein in step S8, the ferromagnetic object is magnetized by an external magnetic field and then placed at any field point in the surrounding space
Figure FDA0002366348590000024
The generated magnetic field
Figure FDA0002366348590000025
Can be expressed as:
Figure FDA0002366348590000021
wherein:
Figure FDA00023663485900000220
the volume occupied by the ferromagnetic object;
Figure FDA00023663485900000210
an additional magnetization generated inside the ferromagnetic object for an external magnetic field;
Figure FDA00023663485900000211
field point vector is used;
Figure FDA00023663485900000212
is the source point vector;
Figure FDA00023663485900000213
Figure FDA00023663485900000214
is composed of
Figure FDA00023663485900000215
Three-component value set of magnetic field intensityA column vector of;
Figure FDA00023663485900000216
performing gradient calculation on the source point coordinates;
Figure FDA00023663485900000217
calculating the gradient of the field point coordinate;
if the ferromagnetic object is subdivided, the integrals in equation (1) are transformed into sums, and for a linear material ferromagnetic object or a homogeneous ferromagnetic object, equation (1) finally forms a linear system of equations:
Figure FDA0002366348590000029
wherein:
Figure FDA0002366348590000027
additional magnetization generated in each unit in the ferromagnetic object for an external magnetic field;
Figure FDA0002366348590000028
a subdivision unit coupling coefficient matrix is obtained;
Figure FDA0002366348590000026
the column vector is formed by the magnetic fields generated by the external magnetic field in each unit in the ferromagnetic object;
according to the Biao-Saval theorem, the magnetic field generated by the current element is as follows:
Figure FDA0002366348590000031
wherein:
Figure FDA0002366348590000035
is a current element, through which a current is
Figure FDA0002366348590000036
Figure FDA0002366348590000037
The radius from the field point to the current element is
Figure FDA0002366348590000038
Figure FDA0002366348590000039
A magnetic field generated at a field point for the current element;
the electrified coil is divided into a plurality of small current elements, the magnetic field generated by the coil can be obtained by superposing the magnetic fields generated by the current elements, and the magnetic field and the current generated by the coil in each unit in the ferromagnetic object are constant under the condition that the relative position of the coil and the ferromagnetic object is constant
Figure FDA00023663485900000310
The relationship between them is:
Figure FDA00023663485900000311
wherein:
Figure FDA00023663485900000312
is a coefficient matrix which is determined by the position relation between each current element and each unit in the ferromagnetic object;
similarly, under the condition that the relative position of the coil and the surface of the cuboid is fixed, the coil generates magnetic fields and currents on each unit of the surface of the cuboid
Figure FDA00023663485900000313
The relationship between them is:
Figure FDA00023663485900000314
wherein:
Figure FDA00023663485900000315
is a coefficient matrix which is determined by the position relation between each current element and each unit on the surface of the cuboid;
from formulas (4) and (5):
Figure FDA0002366348590000032
formula (6) is substituted for formula (2) to obtain:
Figure FDA0002366348590000033
the formula (7) links the additional magnetization intensity generated by each unit in the ferromagnetic object with the magnetic field generated by each unit on the surface of the cuboid by the coil;
assuming that the additional magnetization produced by the elements inside the ferromagnetic object when a coil of the degaussing station is energized is
Figure FDA00023663485900000316
Then, it can be obtained from equation (7):
Figure FDA0002366348590000034
wherein:
Figure FDA00023663485900000317
the magnetic field generated by the coil on each unit on the surface of the cuboid;
corresponding by
Figure FDA00023663485900000318
The generated measuring point magnetic field is as follows:
Figure FDA0002366348590000046
the combination of formula (8) and formula (9) gives:
Figure FDA0002366348590000041
order to
Figure FDA0002366348590000042
Combining the magnetic fields generated by the coils of the degaussing station at the computation points of the surface unit into a matrix
Figure FDA0002366348590000047
Ship magnetic field excited by each coil magnetic field at measuring point of magnetic sensor is combined into matrix
Figure FDA0002366348590000048
Then there are:
Figure FDA0002366348590000045
the conclusion can be drawn from equation (11): the magnetic field generated by the coil at each calculation point of the surface unit and the ship magnetic field excited by the coil magnetic field at the measurement point have a mapping relation, and the induction magnetic field of the ship under the action of any geomagnetic field can be solved as long as the mapping relation is obtained;
in the formula (11)
Figure FDA0002366348590000049
And
Figure FDA00023663485900000410
are all known quantities and can therefore be solved for
Figure FDA00023663485900000411
Figure FDA0002366348590000043
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