CN111522835B - Multi-magnetic target position detection method based on database feature matching - Google Patents
Multi-magnetic target position detection method based on database feature matching Download PDFInfo
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Abstract
The invention discloses a database-based feature matching methodThe detection method of the position of the matched multiple magnetic targets comprises the following steps: (1) calculating a magnetic field vector and a gradient tensor which are generated by superposing all the magnetic beacons after random combination at each measuring point position; (2) constructing a magnetic field vector index table and a magnetic field gradient tensor index table; (3) the carrier measures magnetic field vector and gradient tensor data on a flight path in real time; (4) calculating an actual measurement magnetic field vector matrix L according to the actual measurement magnetic field vector and the gradient tensor data 2 Norm value and measured magnetic field gradient tensor matrix L 2 A norm value; and directly carrying out matching positioning and confirmation optimization in the magnetic field vector index table and the magnetic field gradient tensor index table by using a dichotomy to obtain a final magnetic marker combination situation, and determining the number of magnetic beacons and beacon position information corresponding to the magnetic marker combination situation. The method can make up for the defects that the traditional magnetic beacon positioning inversion technology only needs the known quantity of magnetic sources, and has strong dependence on the distribution of the measuring points and high noise sensitivity.
Description
Technical Field
The invention relates to a magnetic target detection technology, in particular to a multi-magnetic target position detection method based on database feature matching.
Background
The magnetic target detection technology plays an important role in the fields of resource exploration, target detection and tracking, navigation and positioning, medical engineering and the like. However, the magnetic field characteristics generated by the targets have strong non-linear relationship with the positions of the targets, so that the position calculation based on the magnetic field characteristics has high complexity. The problem is further compounded when the region of interest has multiple magnetic targets whose magnetic fields are mixed, when the number of magnetic targets is unknown.
When the distance between the measuring point and the magnetic source is more than 2.5 times of the maximum dimension of the magnetic source, the magnetic source can be regarded as a magnetic dipole. At present, the research on the magnetic dipole inversion technology is mainly based on a single magnetic source and can be divided into two types, one type is an analytical method, and the analytical solution of a magnetic target position is deduced from the analytical expression of a magnetic field vector and a gradient, so that the problem of multiple solutions is solved; the second type is the euler convolution method, which uses the mathematical relationship between the three-dimensional magnetic field vector of the magnetic target and the magnetic field gradient tensor to solve the three-dimensional position, and has the defect of high noise sensitivity. Some scholars popularize single-source positioning methods, such as the Euler convolution method, into the multi-magnetic target position detection research, the noise sensitivity is further improved, and the known quantity of magnetic sources is required. The wiener convolution method requires only a first derivative of the magnetic field gradient and is more noise sensitive, but also requires a known number of magnetic sources. In recent years, nonlinear optimization methods are increasingly used in the field of magnetic target inversion. The method constructs an objective function by using the difference between a measured magnetic field and an estimated magnetic field, and solves the objective function by using a nonlinear optimization estimation method such as least square and the like. But current research also presupposes that the number of magnetic targets is known.
In order to overcome the defects in the method, the application provides a multi-magnetic target position detection method under the condition of unknown quantity. The method has strong adaptability to the distribution of the measuring points and does not need complex mathematical calculation. By taking the magnetic field vector and the gradient data as features, a feature database containing various magnetic target position combinations is established, and the number and the position coordinates of the multi-magnetic dipole can be determined by matching according to the magnetic field feature values at the measuring points.
Disclosure of Invention
The invention aims to provide a multi-magnetic target position detection method based on database feature matching aiming at the problem of multi-magnetic target detection with known and unknown magnetic moments.
The technical scheme adopted by the invention is as follows: a multi-magnetic target position detection method based on database feature matching comprises the following steps:
constructing a magnetic field gradient tensor index table: according to the database established in the step 1, all the correspondingly recorded magnetic field gradient tensors under the conditions of different measuring points and each magnetic beacon combination are taken out to form a magnetic field gradient tensor matrix, and the magnetic field gradient tensor matrix L is calculated 2 Norm value, according to the magnetic field gradient tensor matrix L 2 Sequencing all the magnetic marker combination situations in a sequence from small norm value to large norm value;
step 3, actually measuring data: in an environment of aliasing of a multi-dipole magnetic source magnetic field, a carrier measures magnetic field vector and gradient tensor data on a flight path in real time;
Wherein, step 1 further comprises:
step 1-1, setting a target area:
selecting N track points P ═ P at set interval D 1 P 2 … P i … P N Wherein N is more than or equal to 3, and (N-1) D is more than or equal to 10 and less than or equal to 20, P i The ith track point is represented, namely the ith measuring point, i is 1,2, …, N, and P represents a vector formed by N track points; a square area with the side length of L is defined by taking a measuring point positioned in the middle position as a center, and all possible magnetic targets are positioned in the square area; in the square region, a grid is defined by a width d of 1, and a total of M netsGrid points, each grid point being a potential location of a magnetic dipole;
step 1-2, establishing a database:
assuming that there are at most K magnetic targets in the square region, the magnetic moments of the magnetic targets are all [ M ] x M y M z ]Wherein M is x Component of the magnetic moment of a magnetic target in the x-direction, M y Component of the magnetic moment of the magnetic target in the y-direction, M z Is the component of the magnetic moment of the magnetic target in the z direction; these magnetic targets may be present at any one grid point, but cannot overlap;
let K be the number of magnetic targets, K is less than or equal to K, in total
And (3) calculating a magnetic field vector B and a magnetic field gradient tensor G generated at the position of each track point in each case according to different magnetic beacon combination situations:
wherein, B i The magnetic field vector G generated by the ith magnetic target at a certain track point under the condition of a specific magnetic target combination i The gradient generated by the ith magnetic target at a certain track point under the condition of a specific magnetic target combination, B i The calculation method (2) is obtained according to a magnetic dipole model, and G is shown in formula i The calculation method of (2) is shown in formula (3):
in the formula, B x,i Magnetic field B generated at a certain track point for the ith magnetic target i Component in the x-direction, B y,i Magnetic field B generated at a certain track point for the ith magnetic target i Component in the y-direction, B z,i Magnetic field B generated at a certain track point for the ith magnetic target i Component in the z-direction, (x, y, z) 0 ) Is the three-dimensional position of the measuring point relative to the ith magnetic target, r is the distance between the measuring point and the ith magnetic target, mu is the medium permeability and m x Is the component of the magnetic moment of the ith magnetic target in the x-direction, m y Is the component of the i-th magnetic target's magnetic moment in the y-direction, m z Is the component of the magnetic moment of the ith magnetic target in the z direction;
g xx,i magnetic field vector B generated at a certain track point for the ith magnetic target x,i Spatial rate of change in x-direction, g xy,i Magnetic field vector B generated at a certain track point for the ith magnetic target x,i Spatial rate of change in y-direction, g xz,i Magnetic field vector B generated at a certain track point for the ith magnetic target x,i Spatial rate of change in z-direction, g yx,i Magnetic field vector B generated at a certain track point for the ith magnetic target y,i Spatial rate of change in x-direction, g yy,i Magnetic field vector B generated at certain track point for ith magnetic target y,i Spatial rate of change in y-direction, g yz,i Magnetic field vector B generated at a certain track point for the ith magnetic target y,i Spatial rate of change in z-direction, g zx,i Magnetic field vector B generated at a certain track point for the ith magnetic target z,i Spatial rate of change in x-direction, g zy,i Magnetic field vector B generated at a certain track point for the ith magnetic target z,i Spatial rate of change in y-direction, g zz,i Magnetic field vector B generated at a certain track point for the ith magnetic target z,i Spatial rate of change in the z-direction, and g xx,i +g yy,i +g zz,i ＝0， g xy,i ＝g yx,i ，g xz,i ＝g zx,i ；
For a certain measuring point, the data record stored in the case of a certain specific magnetic mark combination corresponding to the measuring point is as follows:
BG＝[B x B y B z g xx g yx g zx g yy g yz ] (4)
wherein BG is a magnetic field vector and gradient sequence generated at a measuring point by a specific magnetic marker combination, B x For a particular magnetic marker, the component in the x-direction of the magnetic field generated at a certain measuring point, B y For a particular magnetic marker, the component in the y-direction of the magnetic field generated at a certain measuring point, B z For a particular magnetic marker, the component in the z-direction of the magnetic field generated at a certain measuring point, g xx Magnetic field component B generated at a measuring point for a specific magnetic marker combination x Spatial rate of change in x-direction, g yx Magnetic field component B generated at a measuring point for a specific magnetic marker combination y Spatial rate of change in x-direction, g zx Magnetic field component B generated at a measuring point for a specific magnetic marker combination z Spatial rate of change in x-direction, g yy Magnetic field component B generated at a measuring point for a specific magnetic marker combination y Spatial rate of change in y-direction, g yz Magnetic field component B generated at a measuring point for a specific magnetic marker combination y Spatial rate of change in the z-direction;
according to the mode, the magnetic field data at the multiple measuring points corresponding to each combination under each magnetic target quantity is calculated and stored in a database; for each measuring point, the corresponding record number of the measuring point in the database is
Taking all data corresponding to each measuring point as a single data table in a database, wherein the complete database comprises S 1 ,S 2 ,…,S i ,…,S N N data tables, wherein S i A data table corresponding to the ith measuring point, wherein i is 1,2, … and N; the records with the same sequence number in the N data tables are produced on the respective measuring points under the condition of the same magnetic beacon combinationMagnetic field data is generated.
In step 4, the actually measured magnetic field vector matrix L is divided into two 2 Norm value and measured magnetic field gradient tensor matrix L 2 The norm value is directly matched, positioned and optimized in the magnetic field vector index table and the magnetic field gradient tensor index table to obtain the final magnetic target combination situation, and the method further comprises the following steps:
when based on the measured magnetic field vector matrix L 2 The magnetic mark combination corresponding to the best matching value searched by the norm value in the magnetic field vector index table and the magnetic field gradient tensor matrix L according to the actual measurement 2 When the magnetic marker combination corresponding to the best matching value searched by the norm value in the magnetic field gradient tensor index table is the same magnetic marker combination, the magnetic marker combination is regarded as the actual magnetic marker combination;
When based on the measured magnetic field vector matrix L 2 The magnetic mark combination corresponding to the best matching value searched by the norm value in the magnetic field vector index table and the magnetic field gradient tensor matrix L according to the actual measurement 2 Setting a magnetic field vector norm matching threshold c when the magnetic target combination corresponding to the best matching value searched by the norm value in the magnetic field gradient tensor index table is not the same magnetic target combination B Threshold c matched to magnetic field gradient norm G Extracting the actually measured magnetic field vector matrix L 2 The absolute value of the norm value matching error is less than the magnetic field vector norm matching threshold c B All combinations of magnetic markers and the measured magnetic field gradient tensor matrix L 2 The absolute value of the norm value matching error is less than the magnetic field gradient norm matching threshold c G All the magnetic target combinations are used as magnetic target combinations to be selected, and the actually measured magnetic field vector matrix L in the magnetic target combinations to be selected 2 Norm value matching error absolute value and actually measured magnetic field gradient tensor matrix L 2 And the magnetic target combination with the minimum sum of the absolute values of the norm value matching errors is used as a matching result.
The invention has the beneficial effects that: the invention provides a multi-magnetic target position detection method which is simple in principle, efficient and accurate. Compared with the traditional magnetic beacon inversion technology, the method has small influence on the distribution condition of measured points, and can realize positioning on any navigation track; the quantity information and the position coordinates of the magnetic beacons can be directly obtained through database matching without depending on beacon initial values and complex mathematical calculation. Technical support is provided for target tracking, resource exploration, navigation positioning, medical engineering and the like.
Drawings
FIG. 1: the invention relates to a flow chart of a multi-magnetic target position detection method based on database feature matching;
FIG. 2: a mesh division schematic diagram;
FIG. 3: schematic diagram of measuring point and real beacon position;
FIG. 4: the matching result is compared with the real beacon position.
Detailed Description
In order to further understand the contents, features and effects of the present invention, the following embodiments are illustrated and described in detail with reference to the accompanying drawings:
the invention relates to a method for determining the position of a multi-magnetic dipole by establishing a database and carrying out multi-dimensional feature matching in the database by using the characteristic value of a magnetic field at a measuring point. The method is mainly used for determining the number and the positions of a plurality of magnetic targets under the condition that the magnetic moment parameters of the magnetic targets are known and identical.
As shown in fig. 1, a method for detecting the position of multiple magnetic targets based on database feature matching includes the following steps:
Step 1-1, setting a target area:
selecting N track points P (P) with a set interval D (the unit of D is'm') 1 P 2 … P i … P N Wherein N is more than or equal to 3, and (N-1) D is more than or equal to 10 and less than or equal to 20, P i The method comprises the steps of (1) representing an ith track point, namely an ith measuring point, wherein i is 1,2, …, N, and P represents a vector formed by N track points; with measuring points in intermediate positionsThe center of the magnetic field sensor is used for defining a square area with the side length of L, and all possible magnetic targets are located in the square area; a grid is defined within the square region with a width d equal to 1, and there are M grid points, each of which is a potential position of a magnetic dipole.
Step 1-2, establishing a database:
assuming that there are at most K magnetic targets in the square region, the magnetic moments of the magnetic targets are all [ M ] x M y M z ]Wherein M is x Component of the magnetic moment of a magnetic target in the x-direction, M y Component of the magnetic moment of the magnetic target in the y-direction, M z Is the component of the magnetic moment of the magnetic target in the z direction; these magnetic targets may be present at any one grid point, but cannot overlap;
let K be the number of magnetic targets, K is less than or equal to K, in total
And (3) calculating a magnetic field vector B and a gradient tensor G generated at the position of each track point in each case according to different magnetic beacon combination situations:
Wherein, B i The magnetic field vector G generated by the ith magnetic target at a certain track point under the condition of a specific magnetic target combination i The gradient generated by the ith magnetic target at a certain track point under the condition of a specific magnetic target combination, B i The calculation method (2) is obtained according to a magnetic dipole model, and G is shown in formula i The calculation method of (2) is shown in formula (3):
in the formula, B x,i The component in the x direction of the magnetic field Bi generated by the ith magnetic target at a certain track point, B y,i Magnetic field B generated at a certain track point for the ith magnetic target i Component in the y-direction, B z,i Magnetic field B generated at a certain track point for the ith magnetic target i Component in the z-direction, (x, y, z) 0 ) Is the three-dimensional position of the measuring point relative to the ith magnetic target, r is the distance between the measuring point and the ith magnetic target, mu is the medium permeability and m x Is the component of the magnetic moment of the ith magnetic target in the x-direction, m y Is the component of the i-th magnetic target's magnetic moment in the y-direction, m z Is the component of the magnetic moment of the ith magnetic target in the z direction;
g xx,i magnetic field vector B generated at a certain track point for the ith magnetic target x,i Spatial rate of change in x-direction, g xy,i Magnetic field vector B generated at a certain track point for the ith magnetic target x,i Spatial rate of change in y-direction, g xz,i Magnetic field vector B generated at a certain track point for the ith magnetic target x,i Spatial rate of change in z direction, g yx,i Magnetic field vector B generated at a certain track point for the ith magnetic target y,i Spatial rate of change in x-direction, g yy,i Magnetic field vector B generated at certain track point for ith magnetic target y,i Spatial rate of change in y-direction, g yz,i Magnetic field vector B generated at a certain track point for the ith magnetic target y,i Spatial rate of change in z direction, g zx,i Magnetic field vector B generated at a certain track point for the ith magnetic target z,i Spatial rate of change in x-direction, y zy,i Magnetic field vector B generated at a certain track point for the ith magnetic target z,i Spatial rate of change in y-direction, g zz,i Magnetic field vector B generated at a certain track point for the ith magnetic target z,i Spatial rate of change in the z-direction; g i There are only 5 independent gradient variables, because g xx,i +g yy,i +g zz,i ＝0，g xy,i ＝g yx,i ，g xz,i ＝g zx,i ；
Thus, for a measurement point, the data stored for a particular combination of magnetic markers for that measurement point is recorded as:
BG＝[B x B y B z g xx g yx g zx g yy g yz ] (4)
wherein BG is a magnetic field vector and gradient sequence generated at a measuring point by a specific magnetic marker combination, B x For a particular magnetic marker, the component in the x-direction of the magnetic field generated at a certain measuring point, B y For a particular magnetic marker, the component in the y-direction of the magnetic field generated at a certain measuring point, B z For a particular magnetic marker, the component in the z-direction of the magnetic field generated at a certain measuring point, g xx Magnetic field component B generated at a measuring point for a specific magnetic marker combination x Spatial rate of change in x-direction, g yx Magnetic field component B generated at a measuring point for a specific magnetic marker combination y Spatial rate of change in x-direction, g zx Magnetic field component B generated at a measuring point for a specific magnetic marker combination z Spatial rate of change in x-direction, g yy Magnetic field component B generated at a measuring point for a specific magnetic marker combination y Spatial rate of change in y-direction, g yz Magnetic field component B generated at a measuring point for a specific magnetic marker combination y Spatial rate of change in the z-direction;
according to the mode, the magnetic field data at the multiple measuring points corresponding to each combination under each magnetic target quantity is calculated and stored in a database; for each measuring point, the corresponding record number of the measuring point in the database is
Taking all data corresponding to each measuring point as a single data table in a database, wherein the complete database comprises S 1 ,S 2 ,…,S i ,…,S N N data tables, wherein S i A data table corresponding to the ith measuring point, wherein i is 1,2, … and N; the records with the same sequence number in the N data tables generate magnetic field data on the respective measuring points for the same magnetic beacon combination.
Constructing a magnetic field gradient tensor index table: according to the database established in the step 1, all the correspondingly recorded magnetic field gradient tensors under the conditions of different measuring points and each magnetic beacon combination are taken out to form a magnetic field gradient tensor matrix, and the magnetic field gradient tensor matrix L is calculated 2 Constructing a magnetic field gradient tensor index table by using the norm values; wherein the magnetic field gradient tensor index table stores a magnetic field gradient tensor matrix L under the condition of all magnetic target combinations 2 Norm values, at which point the table is recorded in order according to the coordinates of the magnetic target; then, according to the magnetic field gradient tensor matrix L 2 All the magnetic mark combination situations are sorted in the order from small to large of the norm value, and simultaneously, the corresponding recording sequence numbers before the sorting are stored.
Step 3, actually measuring data: in the environment of aliasing of a multi-dipole magnetic source magnetic field, a carrier measures magnetic field vectors and gradient tensor data on N measuring points in real time on a flight path by using a vector magnetometer and a gradiometer according to the same measuring point interval as that in the step 1.
When based on the measured magnetic field vector matrix L 2 The norm value is the best matching value searched in the magnetic field vector index table (the best matching value is the matrix L with the actually measured magnetic field vector) 2 The closest norm value or the smallest difference value, the same applies to the following) corresponding magnetic marker combination and the tensor matrix L based on the actually measured magnetic field gradient 2 When the magnetic target combination corresponding to the best matching value searched by the norm value in the magnetic field gradient tensor index table is the same magnetic target combination, the magnetic target combination is regarded as the actual magnetic target combination;
when based on the measured magnetic field vector matrix L 2 The magnetic mark combination corresponding to the best matching value searched by the norm value in the magnetic field vector index table and the magnetic field gradient tensor matrix L according to the actual measurement 2 Setting a magnetic field vector norm matching threshold c when the magnetic target combination corresponding to the best matching value searched by the norm value in the magnetic field gradient tensor index table is not the same magnetic target combination B Threshold c matched to magnetic field gradient norm G Extracting the actually measured magnetic field vector matrix L 2 The absolute value of the norm value matching error is less than the magnetic field vector norm matching threshold c B All combinations of magnetic markers and the measured magnetic field gradient tensor matrix L 2 The absolute value of the norm value matching error is less than the magnetic field gradient norm matching threshold c G All the magnetic target combinations are used as magnetic target combinations to be selected, and the actually measured magnetic field vector matrix L in the magnetic target combinations to be selected 2 Norm value matching error absolute value and actually measured magnetic field gradient tensor matrix L 2 And the magnetic target combination with the minimum sum of the absolute values of the norm value matching errors is used as a matching result.
And determining the number of the magnetic beacons and the beacon position information corresponding to the magnetic beacon combination situation according to the finally obtained magnetic beacon combination situation.
Fig. 2 is a schematic diagram of the meshing, i.e., the location coordinates where all magnetic beacons may be located in the present invention. The grid area is determined according to the motion track of the aircraft, the grid area is divided outwards by taking the center position of the track as the center, and each grid point is a position where a magnetic dipole can possibly appear. Through random permutation and combination, the combination conditions of 1, 2, … and M magnetic beacons can be obtained, and the magnetic field information at each measuring point in all the combination conditions is superposed and calculated.
Fig. 3 is a schematic diagram of the measuring points and the positions of real beacons. By utilizing the magnetic dipole model, according to the position information of the measuring point and the real magnetic beacon, the real magnetic field vector matrix and the magnetic field gradient tensor matrix at the position of the measuring point can be obtained, and the magnetic field vector matrix L is further calculated 2 Norm value and magnetic field gradient tensor matrix L 2 The norm value corresponds to the magnetic field information at the measured point measured in the actual measurement. The information can be used for searching and matching in the database.
Fig. 4 is a graph comparing the matching result with the real beacon position. It can be seen that after searching, the magnetic beacon position information stored in the database can be matched more accurately. However, since the preset magnetic beacon position is located at the grid point and there is a gap in the grid, if the real magnetic beacon position falls in the gap in the grid, there will be some deviation from the screened beacon position. But the matching result is already a better approximate position, and a basis can be provided for further optimization calculation to determine an accurate solution.
Table 1, table 2, and table 3 are the results of comparing the real values of the magnetic dipoles with the calculated inversion optimization values when k is 3, 2, and 1, respectively. By comparing the position coordinates obtained by the real magnetic dipole and the inversion optimization calculation, the method can accurately invert the quantity of the magnetic sources to obtain the position information approximate to the magnetic dipole, and lays a good foundation for further optimization calculation.
TABLE 1 comparison of the actual values of the magnetic dipoles with the calculated values for the inversion optimization (k 3)
(1-1)
(1-2)
(1-3)
(1-4)
(1-5)
TABLE 2 comparison of the actual values of the magnetic dipoles with the calculated values for the inversion optimization (k 2)
(2-1)
(2-2)
(2-3)
(2-4)
(2-5)
TABLE 3 comparison of the actual values of the magnetic dipoles with the calculated values for the inversion optimization (k ═ 1)
(3-1)
(3-2)
(3-3)
(3-4)
(3-5)
Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make many modifications without departing from the spirit and scope of the present invention as defined in the appended claims.
Claims (2)
1. A multi-magnetic target position detection method based on database feature matching is characterized by comprising the following steps:
step 1, establishing a database: defining a database establishing area according to the track of the aircraft, arranging measuring points, and calculating a magnetic field vector and a gradient tensor generated by superposing all 1, 2, … and M magnetic beacons at each measuring point position after random combination by using a magnetic dipole model;
step 2, constructing a magnetic field vector index table: according to the database established in the step 1, all the correspondingly recorded magnetic field vectors under the conditions of different measuring points and each magnetic beacon combination are taken out to form a magnetic field vector matrix, and a magnetic field vector matrix L is calculated 2 Norm value, according to magnetic field vector matrix L 2 Sequencing all the magnetic marker combination situations in a sequence from small norm values to large norm values;
constructing a magnetic field gradient tensor index table: according to the database established in the step 1, all the correspondingly recorded magnetic field gradient tensors under the conditions of different measuring points and each magnetic beacon combination are taken out to form a magnetic field gradient tensor matrix, and a magnetic field gradient tensor matrix L is calculated 2 Norm value, according to the magnetic field gradient tensor matrix L 2 Sequencing all the magnetic marker combination situations in a sequence from small norm values to large norm values;
step 3, actually measuring data: in an environment of aliasing of a multi-dipole magnetic source magnetic field, a carrier measures magnetic field vector and gradient tensor data on a flight path in real time;
step 4, actual matching: constructing an actual measurement magnetic field vector matrix and an actual measurement magnetic field gradient tensor matrix according to the actual measurement magnetic field vector and gradient tensor data in the step 3, and respectively calculating an actual measurement magnetic field vector matrix L 2 Norm value and measured magnetic field gradient tensor matrix L 2 A norm value; actual measurement magnetic field vector matrix L by using dichotomy 2 Norm value and measured magnetic field gradient tensor matrix L 2 The norm value is directly matched, positioned and confirmed and optimized in a magnetic field vector index table and a magnetic field gradient tensor index table to obtain the final magnetic marker combination situation, and the number and the position information of the magnetic beacons corresponding to the magnetic marker combination situation are determined;
Wherein, theThe actual measurement magnetic field vector matrix L is formed by utilizing the dichotomy 2 Norm value and measured magnetic field gradient tensor matrix L 2 The norm value is directly matched, positioned and optimized in the magnetic field vector index table and the magnetic field gradient tensor index table to obtain the final magnetic target combination situation, and the method further comprises the following steps:
when based on the measured magnetic field vector matrix L 2 The magnetic mark combination corresponding to the best matching value searched by the norm value in the magnetic field vector index table and the tensor matrix L according to the actually measured magnetic field gradient 2 When the magnetic target combination corresponding to the best matching value searched by the norm value in the magnetic field gradient tensor index table is the same magnetic target combination, the magnetic target combination is regarded as the actual magnetic target combination;
when based on the measured magnetic field vector matrix L 2 The magnetic mark combination corresponding to the best matching value searched by the norm value in the magnetic field vector index table and the tensor matrix L according to the actually measured magnetic field gradient 2 When the magnetic marker combination corresponding to the best matching value searched by the norm value in the magnetic field gradient tensor index table is not the same magnetic marker combination, setting a magnetic field vector norm matching threshold c B Threshold c matched to magnetic field gradient norm G Extracting the actually measured magnetic field vector matrix L 2 The absolute value of the norm value matching error is less than the magnetic field vector norm matching threshold c B All magnetic marker combinations and the measured magnetic field gradient tensor matrix L 2 The absolute value of the norm value matching error is less than the magnetic field gradient norm matching threshold c G All the magnetic target combinations are used as magnetic target combinations to be selected, and the actually measured magnetic field vector matrix L in the magnetic target combinations to be selected 2 Norm value matching error absolute value and actually measured magnetic field gradient tensor matrix L 2 And the magnetic target combination with the minimum sum of the absolute values of the norm value matching errors is used as a matching result.
2. The method for detecting the positions of multiple magnetic targets based on database feature matching according to claim 1, wherein the step 1 further comprises:
step 1-1, setting a target area:
selecting N sails at a set interval DLocus point P ═ P 1 P 2 …P i …P N Wherein N is more than or equal to 3, and (N-1) D is more than or equal to 10 and less than or equal to 20, P i The ith track point is represented, namely the ith measuring point, i is 1,2, …, N, and P represents a vector formed by N track points; a square area with the side length of L is defined by taking a measuring point positioned in the middle position as a center, and all possible magnetic targets are positioned in the square area; defining a grid with the width d being 1 in the square area, wherein M grid points are provided, and each grid point is a potential position of a magnetic dipole;
Step 1-2, establishing a database:
assuming that there are at most K magnetic targets in the square region, the magnetic moments of the magnetic targets are all [ M ] x M y M z ]Wherein M is x Component of the magnetic moment of a magnetic target in the x-direction, M y Component of the magnetic moment of the magnetic target in the y-direction, M z Is the component of the magnetic moment of the magnetic target in the z direction; these magnetic targets may be present at any one grid point, but cannot overlap;
let K be the number of magnetic targets, K is less than or equal to K, in total
Different magnetic beacon combination cases, calculating the magnetic field vector B and the magnetic field gradient tensor G generated at each track point position in each case:
wherein, B i The magnetic field vector G generated by the ith magnetic target at a certain track point under the condition of a specific magnetic target combination i The gradient generated by the ith magnetic target at a certain track point under the condition of a specific magnetic target combination, B i The calculation method (2) is obtained according to a magnetic dipole model, and G is shown in formula i The calculation method of (2) is shown in formula (3):
in the formula, B x,i Magnetic field B generated at a certain track point for the ith magnetic target i Component in the x-direction, B y,i Magnetic field B generated at a certain track point for the ith magnetic target i Component in the y-direction, B z,i Magnetic field B generated at a certain track point for the ith magnetic target i Component in the z-direction, (x, y, z) 0 ) Is the three-dimensional position of the measuring point relative to the ith magnetic target, r is the distance between the measuring point and the ith magnetic target, mu is the medium permeability and m x Is the component of the magnetic moment of the ith magnetic target in the x-direction, m y Is the component of the magnetic moment of the ith magnetic target in the y direction, m z Is the component of the magnetic moment of the ith magnetic target in the z direction;
g xx,i magnetic field vector B generated at a certain track point for the ith magnetic target x,i Spatial rate of change in x-direction, g xy,i Magnetic field vector B generated at a certain track point for the ith magnetic target x,i Spatial rate of change in y-direction, g xz,i Magnetic field vector B generated at a certain track point for the ith magnetic target x,i Spatial rate of change in z-direction, g yx,i Magnetic field vector B generated at a certain track point for the ith magnetic target y,i Spatial rate of change in x-direction, g yy,i Magnetic field vector B generated at a certain track point for the ith magnetic target y,i Spatial rate of change in y-direction, g yz,i Magnetic field vector B generated at a certain track point for the ith magnetic target y,i Spatial rate of change in z-direction, g zx,i Magnetic field vector B generated at a certain track point for the ith magnetic target z,i Spatial rate of change in x-direction, g zy,i For the ith magnetic target at a certain track pointA magnetic field vector B generated thereby z,i Spatial rate of change in y-direction, g zz,i Magnetic field vector B generated at a certain track point for the ith magnetic target z,i Spatial rate of change in the z-direction, and g xx,i +g yy,i +g zz,i ＝0，g xy,i ＝g yx,i ，g xz,i ＝g zx,i ；
For a certain measuring point, the data record stored in the case of a certain specific magnetic mark combination corresponding to the measuring point is as follows:
BG＝[B x B y B z g xx g yx g zx g yy g yz ] (4)
wherein BG is a magnetic field vector and gradient sequence generated at a certain measuring point by a specific magnetic marker combination, B x For a particular magnetic marker, the component in the x-direction of the magnetic field generated at a certain measuring point, B y For a particular magnetic marker, the component in the y-direction of the magnetic field generated at a certain measuring point, B z For a particular magnetic marker, the component in the z-direction of the magnetic field generated at a certain measuring point, g xx Magnetic field component B generated at a measuring point for a specific magnetic marker combination x Spatial rate of change in x-direction, g yx Magnetic field component B generated at a measuring point for a specific magnetic marker combination y Spatial rate of change in x-direction, g zx Magnetic field component B generated at a measuring point for a specific magnetic marker combination z Spatial rate of change in x-direction, g yy Magnetic field component B generated at a measuring point for a specific magnetic marker combination y Spatial rate of change in y-direction, g yz Magnetic field component B generated at a measuring point for a specific magnetic marker combination y Spatial rate of change in the z-direction;
according to the mode, the magnetic field data at the multiple measuring points corresponding to each combination under each magnetic target quantity is calculated and stored in a database; for each measuring point, the corresponding record number of the measuring point in the database is
Taking all data corresponding to each measuring point as a single data table in a database, wherein the complete database comprises S 1 ,S 2 ,…,S i ,…,S N N data tables, wherein S i A data table corresponding to the ith measuring point, wherein i is 1,2, …, N; the records with the same sequence number in the N data tables generate magnetic field data on the respective measuring points for the same magnetic beacon combination.
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