Full-tensor high-order magnetic field gradient sensing system and use method

Abstract

The invention discloses a full-tensor high-order magnetic field gradient sensing system and a use method, the full-tensor high-order magnetic field gradient sensing system comprises a magnetic field sensing probe, a non-metal directional support, a high-strength engineering plastic shell and a communication antenna, the magnetic field sensing probe comprises a pure wood support frame, 15 three-axis magnetic field sensors and a magnetic field acquisition processing communication module; the nine three-axis magnetic field sensors are distributed in an xy plane in a shape like a Chinese character'tian ', and the six three-axis magnetic field sensors are arranged in an xz plane in an upper row and a lower row. The magnetic field sensing probe is installed in the nonmetal directional support through the pure wood supporting frame, and the z-axis of the magnetic field sensing probe is always kept in a plumb downward mode. The plastic sealed shell is wrapped outside the directional support, and the communication antenna is covered on the shell. By adopting the full-tensor high-order magnetic field gradient sensing system and the full-tensor high-order magnetic field gradient sensing method, all first-order and second-order magnetic field gradient parameters can be obtained, so that accurate measurement is carried out.

Description

Technical Field

[0001] The present invention relates to the field of magnetic field gradient measurement technology, and in particular to a full tensor high-order magnetic field gradient sensing system and a use method thereof. Background Art

[0002] The magnetic gradient tensor is the rate of change of the three components of the magnetic field along the three directions of space. Compared with the single-component magnetic field and the total magnetic field, the magnetic gradient tensor technology can extract richer attitude information and magnetic source information about the target body, has higher spatial resolution, and strong anti-interference ability, is not easily affected by environmental magnetic interference and geomagnetic diurnal changes, has strong adaptability to complex environments, has the good property of being less affected by the magnetization direction of the target object, and improves the positioning accuracy of the target, which is more conducive to the positioning and tracking of magnetic targets. After obtaining the magnetic field gradient tensor, richer magnetic field information such as tensor invariants, eigenvalues ​​and moduli and many rotation invariants can be obtained. After further processing, richer, detailed and in-depth magnetic field characteristic information can be obtained. It is widely used in non-destructive testing, magnetic dipole source positioning, magnetic body geometric parameter inversion and other fields. Magnetic gradient tensor data can be used to realize aeromagnetic detection, mineral exploration and soil ferrous metal search, search for unexploded bombs, mine clearance, submarine reconnaissance or underwater metal target positioning and inversion identification, underwater / underground explosive detection, underwater magnetic object detection, intrusion object detection, indoor positioning, in vivo micro-diagnostic device positioning, metal defect, rust, stress and other damage detection and other civil and military fields, and the application prospects are very broad.

[0003] In the actual magnetic field gradient measurement system, the target magnetic field is generally measured by multiple three-axis magnetic sensors, thereby indirectly obtaining the magnetic field gradient. In order to adapt to different application scenarios, various magnetic field gradient sensing systems with different structures and combinations have also emerged. The first-order magnetic gradient tensor is the most commonly used measurement object in practical applications. The first-order magnetic gradient tensor has a total of 9 parameters, 5 of which are independent parameters. Correspondingly, many scholars have developed the measurement structure, principle and algorithm of the first-order magnetic field gradient tensor, and have been applied in different fields. For example, when encountering strong noise, there will be large errors in the cross array and the hexahedral array. At present, the first-order magnetic field gradient tensor needs to be combined with the magnetic induction intensity when it is used in positioning applications. It will inevitably be affected by environmental magnetic fields such as the geomagnetic field, making it difficult to detect and locate magnetic targets. The second-order magnetic gradient tensor also has important applications in positioning. The second-order magnetic gradient tensor has a total of 27 parameters, 9 of which are independent parameters. However, the second-order magnetic field gradient measurement method in the existing public literature only gives some parameters of the second-order magnetic gradient tensor. For example, the plane forms a diamond arrangement, which can only obtain some parameters of the second-order magnetic gradient tensor, resulting in limited application occasions. In addition, many scholars have only given a schematic diagram of the composition of the three-axis magnetic sensor in the magnetic field gradient sensing system, and have not given a specific structure and assembly method, so there is still a long way to go for specific practical applications.

[0004] In summary, the existing magnetic field gradient sensing system has the following disadvantages:

[0005] (1) Most of the existing magnetic field gradient sensing systems are first-order magnetic field gradient sensing systems, which only measure the first-order magnetic field gradient and cannot measure the second-order magnetic field gradient parameters;

[0006] (2) The existing first-order magnetic field gradient sensing system can only measure part of the first-order magnetic field gradient parameters, but cannot measure the complete first-order magnetic field gradient parameters. It is only a partial tensor first-order magnetic field gradient sensing system, not a full tensor first-order magnetic field gradient sensing system;

[0007] (3) The probe of the existing first-order magnetic field gradient sensing system is made of metal, which causes a certain degree of magnetic field interference;

[0008] (4) The existing first-order magnetic field gradient sensing system still needs to combine magnetic induction intensity and magnetic field gradient for positioning. However, the magnetic induction intensity parameter has the problem that it is difficult to eliminate environmental interference magnetic fields such as the earth's background magnetic field, so the error is large during positioning;

[0009] (5) The existing magnetic field gradient sensing system needs to use other auxiliary means such as GPS for self-positioning and cannot perform self-positioning through its own magnetic field gradient sensing system. Summary of the invention

[0010] Aiming at the current situation that most of the existing magnetic field gradient sensing systems are for the first-order magnetic field gradient, cannot obtain all the first-order and second-order magnetic field gradient parameters, and do not provide a specific construction method, a full tensor high-order magnetic field gradient sensing system and its use method are proposed.

[0011] In order to achieve the above object, the present invention is implemented through the following technical solutions: a full tensor high-order magnetic field gradient sensing system, comprising:

[0012] A magnetic field sensing probe, comprising a pure wood support frame, 15 three-axis magnetic field sensors and a magnetic field acquisition, processing and communication module, wherein the pure wood support frame is used to support the 15 three-axis magnetic field sensors and the magnetic field acquisition, processing and communication module, and in a coordinate system oxyz, the pure wood support frame has 9 installation nodes A, B, C, D, O, E, F, G, H distributed in a field shape in an xy plane, and has 6 installation nodes I, J, K, L, M, N distributed in two rows in an xz plane, and the two rows of installation nodes are relatively located above and below the xy plane, the 15 three-axis magnetic field sensors are located on the 15 installation nodes, and the magnetic field acquisition, processing and communication module is used to collect, process and transmit magnetic field data of the 15 three-axis magnetic field sensors;

[0013] A non-metallic directional support, wherein the magnetic field sensor probe is installed in the non-metallic directional support through the pure wood support frame; and the magnetic field sensor probe can rotate in the non-metallic directional support so that the z-axis of the magnetic field sensor probe is always kept with the plumb bob downward;

[0014] A high-strength engineering plastic shell, wherein the high-strength engineering plastic shell is wrapped outside the non-metallic directional bracket, and the outer surface of the high-strength engineering plastic shell is spherical; and

[0015] The communication antenna is covered on the high-strength engineering plastic shell and is used to receive the magnetic field data transmitted by the magnetic field acquisition and processing communication module and transmit it to the remote data system.

[0016] Furthermore, the pure wood support frame includes a plurality of wood poles, the plurality of wood poles are interconnected to form 15 installation nodes, the 15 three-axis magnetic field sensors are respectively installed on the 15 installation nodes, and the distance between two adjacent installation nodes on the same wood pole is equal.

[0017] Furthermore, the plurality of wooden poles are mortise and tenon-jointed with each other.

[0018] Furthermore, the non-metallic directional bracket includes three wooden hollow spheres, and the three wooden hollow spheres are connected to each other freely from the inside to the outside through ceramic bearings and cylindrical wooden dowels. The pure wooden support frame is installed on the innermost wooden hollow spheres, and the outermost wooden hollow sphere is rotatably connected to the inner wall of the high-strength engineering plastic shell through ceramic bearings and cylindrical wooden dowels, and is concentrically arranged with the high-strength engineering plastic shell.

[0019] Furthermore, the three wooden hollow balls each include a first circular wooden ring and four second circular wooden rings, the first circular wooden ring and the four second circular wooden rings are spliced ​​to form the wooden hollow ball in a spherical shape, the first circular wooden ring has the same diameter as the wooden hollow ball; the diameters of the four second circular wooden rings are smaller than the diameter of the first circular wooden ring;

[0020] Among them, one ceramic bearing and one cylindrical wooden dowel are arranged at four positions evenly spaced 90 degrees on the first circular wooden rings of the wooden hollow spheres of the outermost layer and the middle layer, and the wooden hollow spheres of the outermost layer are rotatably connected to the high-strength engineering plastic shell through the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced 180 degrees apart, and the ceramic bearings and cylindrical wooden dowels arranged at the other two positions spaced 180 degrees apart on the wooden hollow spheres of the outer layer are rotatably connected to the wooden hollow spheres of the middle layer through the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced 180 degrees apart;

[0021] A ceramic bearing and a cylindrical wooden dowel are arranged at two positions 180 degrees apart on the first circular wooden ring of the innermost layer of the wooden hollow sphere. The innermost layer of the wooden hollow sphere can be rotatably connected with the other two ceramic bearings and cylindrical wooden dowels arranged at positions 180 degrees apart on the wooden hollow sphere of the middle layer through the ceramic bearings and cylindrical wooden dowels arranged at the two positions.

[0022] Furthermore, the communication antenna is a metal mesh wrapped in the high-strength engineering plastic shell.

[0023] Furthermore, the metal mesh comprises galvanized copper wires and galvanized molybdenum wires, the copper wires and the molybdenum wires are interwoven and woven into twisted pairs, and the twisted pairs are woven into the metal mesh.

[0024] Furthermore, it also includes a plurality of solar cells, which are spliced ​​into a grid and covered on the high-strength engineering plastic shell, and the metal mesh formed by the communication antenna covers the grid-shaped splicing of the solar cells.

[0025] A method for using a full tensor high-order magnetic field gradient sensing system, using the method of the full tensor high-order magnetic field gradient sensing system, comprising:

[0026] The full tensor high-order magnetic field gradient sensing system is placed on the sea surface in a floating state to measure the position of an underwater submarine;

[0027] The complete first-order magnetic field gradient is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensor;

[0028] The complete second-order magnetic field gradient is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensor;

[0029] The three-dimensional position vector from the magnetic field sensor probe to the underwater submarine is calculated through the first-order magnetic field gradient and the second-order magnetic field gradient;

[0030] Provide the longitude, latitude and other geographical parameters of the location of the magnetic field sensor probe;

[0031] Give the angle between the coordinate system of the magnetic field sensor probe and the geographic north;

[0032] Give the three-dimensional position of the underwater submarine;

[0033] The location of the full tensor high-order magnetic field gradient sensor system in the sea, the angle between the coordinate system of the magnetic field sensor probe and the geographic north, and the three-dimensional position of the underwater submarine are sent to a distant data system.

[0034] Furthermore, the specific method for calculating the complete first-order magnetic field gradient using the magnetic induction intensity measured by the three-axis magnetic field sensor is as follows:

[0035] Set the magnetic induction intensity B, including three scalars B x , B y and B z , the first-order magnetic field gradient G, is in the form of a matrix of 3 rows and 3 columns, including 9 parameters, which can be expressed as 3 vectors, namely G x , G y and G z , each vector contains three scalars; the second-order magnetic field gradient H is three matrices, namely H x , H y and H z , each matrix contains 9 scalars;

[0036] The gradient of magnetic induction intensity B along the x direction is B xx , B yx and B zx , that is, the magnetic field gradient G x

[0037]

[0038] The gradient of magnetic induction intensity B along the y direction is B xy , B yy and B zy , that is, the magnetic field gradient G y

[0039]

[0040] The gradient of magnetic induction intensity B along the z direction is B xz , B yz and B zz , that is, the magnetic field gradient G z

[0041]

[0042] The first-order magnetic field gradient G is a symmetric matrix, B xy -B yx =0, B xz -B zx =0, B yz -B zy =0, its trace traceG=B xx +B yy +B zz = 0, so among the 9 elements of the magnetic field gradient tensor, only 5 elements are independent, namely B xx , B xy , B xz , B yy, B yz ;

[0043] The magnetic field gradient is calculated by differentiating the magnetic induction intensity measured by the three-axis magnetic field sensor at two locations, and then the multiple magnetic field gradients are averaged;

[0044] B i is the magnetic induction intensity vector measured by the three-axis magnetic field sensor at point i. Point i can be A, B, C, D, E, F, G, H, I, J, K, L, M, N, O nodes, B xi , B yi , and B xz They are the magnetic induction intensity vector B i The three components.

[0045] G xj is the first-order magnetic field gradient of the magnetic induction intensity along the x direction at point j, G yj is the first-order magnetic field gradient of the magnetic induction intensity along the y direction at point j, G zj is the first-order magnetic field gradient of the magnetic induction intensity along the z direction at point j. Point j can be B, D, E, G, M, J, P, Q, R, S, T, or W.

[0046] The distance between two adjacent installation nodes on the same wooden pole is equal, and the 15 three-axis magnetic field sensors are located on the 15 installation nodes, that is, the distance between the three-axis magnetic field sensors on two adjacent installation nodes on the same wooden pole is equal, which is d;

[0047] The magnetic field gradient G can be calculated by measuring the magnetic induction intensity of the three-axis magnetic field sensors at points A and C, D and E, F and H, L and N, and I and K. x , in order to reduce the error, average it and calculate it as follows:

[0048]

[0049] The magnetic field gradient G can be calculated by measuring the magnetic induction intensity of the three-axis magnetic field sensors at points A and F, points B and G, and points C and H. y , in order to reduce the error, average it and calculate it as follows:

[0050]

[0051] The magnetic field gradient G can be calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points I and L, J and M, and K and N. z , in order to reduce the error, average it and calculate it as follows:

[0052]

[0053] The specific method for calculating the complete second-order magnetic field gradient using the magnetic induction intensity measured by the three-axis magnetic field sensor is:

[0054] Set the first-order magnetic field gradient G along the x direction, that is, G x , G y and G z The gradient along the x direction, denoted as H xxx , H yxx , Hzxx , H xyx , H yyx , H zyx , H xzx , H yzx , H zzx , that is, the second-order magnetic field gradient H x :

[0055]

[0056] The main diagonal elements satisfy H xxx +H yyx +H zzx =0,H x The matrix is ​​a symmetric matrix, H x There are 9 parameters in the matrix, but only 5 independent parameters, namely H xxx , H xyx , H xzx , H yyx and H yzx ;

[0057] The first-order magnetic field gradient G is the gradient along the y direction, that is, G x , G y and G z The gradient along the y direction, denoted as H xxy , H yxy , H zxy , H xyy , H yyy , H zyy , H xzy , H yzy , H zzy , that is, the second-order magnetic field gradient H y :

[0058]

[0059] The main diagonal elements satisfy H xxy +H yyy +H zzy =0,H y The matrix is ​​a symmetric matrix, H y There are 9 parameters in the matrix, but only 5 independent parameters, namely H xxy , Hxyy , H xzy , H yyy and H yzy ;

[0060] The first-order magnetic field gradient G is the gradient along the z direction, that is, G x , G y and G z The gradient along the z direction, denoted as H xyz , H yxz , H zxz , H xyz , H yyz , H zyz , H xzz , H yzz , H zzz , that is, the second-order magnetic field gradient H z :

[0061]

[0062] The main diagonal elements satisfy H xxz +H yyz +H zzz =0,H z The matrix is ​​a symmetric matrix, H z There are 9 parameters in the matrix, but only 5 independent parameters, namely H xxz , H xyz , H xzz , H yyz and H yzz ;

[0063] According to the spatial arrangement of the three-axis magnetic sensor and the definition of the second-order magnetic field gradient tensor, the second-order magnetic field gradient tensors at the origin o of the coordinate system are respectively;

[0064] First, the first-order magnetic field gradient G at points Q and P is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensor at points E and O, and points O and D. x The first-order magnetic field gradient G at points E and D is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points C and H, and points A and F. y The first-order magnetic field gradient G at points E and D is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points K and N, L and I. z ;

[0065] Among them, point Q is the center of the line connecting points E and O, point P is the center of the line connecting points O and D, and the first-order magnetic field gradient G passing through points Q and P is x The first-order magnetic field gradient G at points E and D y The first-order magnetic field gradient G at points E and D z , respectively calculate the magnetic field gradient G x , Gy and G z The magnetic field gradient along the x direction, that is, the second-order magnetic field gradient H x , calculated as follows:

[0066]

[0067] First, the first-order magnetic field gradient G at points G and B is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points H and F, and points A and C. x The first-order magnetic field gradient G at points S and R is calculated by using the magnetic induction intensity measured by the three-axis magnetic field sensors at points G and O, and points O and B. y The first-order magnetic field gradient G at points E and D is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points K and N, L and I. z ;

[0068] Among them, R is the center of the line connecting points O and B, S is the center of the line connecting points G and O, and the first-order magnetic field gradient G passing through points G and B is x The first-order magnetic field gradient G at points S and R y , respectively calculate the magnetic field gradient G x and G y The magnetic field gradient along the y direction, G z The magnetic field gradient along the y direction (H xzy , H yzy , H zzy ) and G x The magnetic field gradient along the y direction (H xxy , H yxy , H zxy ) in the third parameter H zxy , G y The magnetic field gradient along the y direction (H xyy , H yyy , H zyy ) in the third parameter H zyy , G z The magnetic field gradient along the z direction (H xzz , H yzz , H zzz ) in the second parameter H yzz Same, * is used to indicate the magnetic field gradient G x , G y and G z The magnetic field gradient along the y direction, that is, the second-order magnetic field gradient H y , calculated as follows:

[0069]

[0070] In the formula, * indicates the parameters in the vector and H x , Hy , H z The other parameters in are repeated and do not need to be solved again;

[0071] Point T is the center of the line connecting points M and O, and point W is the center of the line connecting points O and J;

[0072] First, the first-order magnetic field gradient G at points M and J is calculated by using the magnetic induction intensity measured by the three-axis magnetic field sensors at points N and L, and points K and I. x The first-order magnetic field gradient G at points T and W is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points M and O, and points O and J. z ;

[0073] Then the first-order magnetic field gradient G passing through points M and J x , the first-order magnetic field gradient G at points T and W z , respectively calculate the magnetic field gradient G x and G z Magnetic field gradient along the z direction; G y The magnetic field gradient H along the z direction xyz , H yyz , H zyz ) and G z The magnetic field gradient along the x direction (H xzx , H yzx , H zzx ) in the second parameter H yzx , G y The magnetic field gradient along the y direction (H xyy , H yyy , H zyy ) in the third parameter H zyy , G z The magnetic field gradient along the z direction (H xzz , H yzz , H zzz ) in the second parameter H yzz The same is indicated by **. Magnetic field gradient G x , G y and G z The magnetic field gradient along the z direction, that is, the second-order magnetic field gradient H z , calculated as follows:

[0074]

[0075] In the formula, ** indicates the parameters in the vector and H x , H y , H z The other parameters in are repeated and do not need to be solved again;

[0076] The specific method for calculating the three-dimensional position vector from the magnetic field sensor probe to the underwater submarine through the first-order magnetic field gradient and the second-order magnetic field gradient is:

[0077] The first-order magnetic field gradient G along the x direction x and the second-order magnetic field gradient H x , get the three-dimensional position vector of the underwater submarine:

[0078] r=-4(H x ) -1 G x (14)

[0079] r is the position vector, and the three-dimensional position of the underwater submarine in the coordinate system oxyz is r(x, y, z).

[0080] By finding the first-order magnetic field gradient G in the y direction y and the second-order magnetic field gradient H y , we can get the three-dimensional position vector of the underwater submarine

[0081] r=-4(H y ) -1 G y (15)

[0082] By finding the first-order magnetic field gradient G in the z direction z and the second-order magnetic field gradient H z , we can get the three-dimensional position vector of the underwater submarine

[0083] r=-4(H z ) -1 G z (16)

[0084] By averaging the three-dimensional position vectors of the underwater submarine obtained from the first-order and second-order magnetic field gradients along the x, y and z directions, we can obtain

[0085]

[0086] The specific method for giving the geographical parameters such as longitude and latitude of the location of the magnetic field sensor probe is:

[0087] The magnetic field intensity B passing through point O xO , B yO and B zO , by comparing with the built-in geomagnetic map, giving the magnetic declination Three geographical parameters: longitude λ, latitude Ψ;

[0088] Among them, B zO is the magnetic induction intensity in the plumb bob direction, B xO and B yOIt is the magnetic induction intensity in the horizontal direction. The magnetic declination is positive when it is east of the north and negative when it is west of the north. The geographic north is the direction of the meridian toward the North Pole. The geomagnetic north is the north of the Earth's magnetic pole, that is, the north direction indicated by the compass. The declination between the geomagnetic north and the geographic north is the magnetic declination.

[0089] The specific method to give the angle between the coordinate system of the magnetic field sensor probe and the geographic north is:

[0090] Recalculate the magnetic induction intensity based on the latitude and longitude, compare it with the actually measured magnetic induction intensity, and give the angle between the x-axis of the coordinate system of the magnetic field sensor probe and the geographic north;

[0091] The International Geomagnetic Reference Field (IGRF) is a standard global model that describes the Earth's main magnetic field. In the IGRF model, the magnetic potential of the main magnetic field (i.e., the internal source field) can be expressed by spherical harmonics:

[0092]

[0093] Where r is the distance from the center of the earth at any point, λ is the longitude, θ is the co-latitude, θ=90-Ψ, Ψ is the latitude, is the Schmidt quasi-normalized associated Legendre function, is the spherical harmonic series coefficient of the internal source field magnetic potential;

[0094] The geomagnetic coordinate system is defined as OXYZ, where the north horizontal component is the X axis, the east horizontal component is the Y axis, the plumb downward component is the Z axis, and the right-hand criterion is satisfied. In the geomagnetic coordinate system OXYZ, the differential of the magnetic potential spherical harmonic function along the axial direction is calculated according to the longitude and latitude, and the three components of the magnetic induction intensity of the geomagnetic field are calculated;

[0095]

[0096] Where R is the radius of the international reference sphere, that is, the average radius of the earth (R = 6371.2 km). is the nth order mth order Gaussian spherical harmonic coefficient, which is taken according to the 11th generation IGRF, N is the cutoff order, N = 10;

[0097] The specific values ​​of the parameters in formula (18)-(21), such as r, m, n, The value of can be found in many published documents and will not be elaborated here.

[0098] For example, CCFinlay, S.Maus, CDBeggan, TNBondar, A.Chambodut, et al. International Geomagnetic Reference Field: the eleventh generation[J], Geophysical Journal International, 2010, 183, 1216–1230;

[0099] The angle between the x-axis and the geomagnetic north direction in the coordinate system of the magnetic field sensor probe is

[0100]

[0101] In the coordinate system of the magnetic field sensor probe, the angle between the x-axis and the geographic north is: north by east The z-axis is the plumb bob pointing downward, and the y-axis conforms to the right-hand rule;

[0102] The specific method of giving the three-dimensional position vector of an underwater submarine is:

[0103] The full tensor high-order magnetic field gradient sensing system is located at latitude Ψ and longitude λ. At this location, in the coordinate system of the magnetic field sensor probe, the x-axis is east of the geographic north. The z-axis is the plumb bob pointing downward, and the y-axis conforms to the right-hand rule. In this coordinate system, the three-dimensional position vector of the underwater submarine is r;

[0104] The specific method of transmitting the position of the full tensor high-order magnetic field gradient sensor system in the sea, the angle between the coordinate system of the magnetic field sensor probe and the geographic north, and the three-dimensional position of the underwater submarine to a remote data system is as follows:

[0105] By means of remote communication, the longitude and latitude of the full tensor high-order magnetic field gradient sensing system, the angle between the coordinate system of the magnetic field sensing probe and the geographic north, and the three-dimensional position vector of the underwater submarine are transmitted to a remote data system.

[0106] Beneficial effects of the present invention:

[0107] The above full tensor high-order magnetic field gradient sensing system and use method have the following advantages:

[0108] 1. Since the magnetic field sensor probe can rotate in the directional bracket, the z-axis in the coordinate system of the magnetic field sensor probe is always plumb downward.

[0109] 2. The magnetic induction intensity of the underwater submarine is obtained through the three-axis magnetic field sensor in the magnetic field sensor probe, and 9 parameters of the first-order magnetic field gradient and 27 parameters of the second-order magnetic field gradient can be calculated. The three-dimensional position of the underwater submarine is obtained through the first-order magnetic field gradient and the second-order magnetic field gradient. The longitude and latitude of the sea position where the full tensor high-order magnetic field gradient sensor system is located, the angle between the coordinate system of the magnetic field sensor probe and the geographic north, and the three-dimensional position of the underwater submarine are sent to the remote data receiving system through the communication antenna, and the accurate position of the underwater submarine can be obtained;

[0110] 3. The sensing system uses a pure wooden support frame and non-metallic directional bracket to eliminate electromagnetic interference. Without the help of any auxiliary positioning means such as GPS, the full tensor high-order magnetic field gradient sensing system can obtain its own position and the three-dimensional position of the underwater submarine. BRIEF DESCRIPTION OF THE DRAWINGS

[0111] In order to more clearly illustrate the specific implementation of the present invention, the following will briefly introduce the drawings required for use in the specific implementation. In all the drawings, each element or part is not necessarily drawn according to the actual scale.

[0112] Figure 1 A schematic diagram of a full tensor high-order magnetic field gradient sensing system provided by an embodiment of the present invention;

[0113] Figure 2 for Figure 1 A data transmission schematic diagram of a full tensor high-order magnetic field gradient sensing system is shown;

[0114] Figure 3 for Figure 1 A node arrangement diagram of a magnetic field sensing probe in a full tensor high-order magnetic field gradient sensing system is shown;

[0115] Figure 4 for Figure 1 A schematic diagram of a full tensor high-order magnetic field gradient sensing system in which a pure wooden support frame is spliced ​​at right-angle nodes is shown;

[0116] Figure 5 for Figure 1 A schematic diagram of a pure wood support frame spliced ​​at a T-point in a full tensor high-order magnetic field gradient sensing system is shown;

[0117] Figure 6 for Figure 1 The connection and installation sequence of wooden poles of a pure wooden support frame at a spatial cross-shaped node in a full tensor high-order magnetic field gradient sensing system shown;

[0118] Figure 7 for Figure 1A schematic diagram of the installation method of a three-axis sensor in a full tensor high-order magnetic field gradient sensing system is shown;

[0119] Figure 8 for Figure 1 A schematic diagram of a wooden hollow sphere on the outermost layer of a non-metallic directional support in a full tensor high-order magnetic field gradient sensing system shown;

[0120] Fig. 9 for Figure 1 A schematic diagram of a wooden hollow sphere in the middle layer of a non-metallic directional support in a full tensor high-order magnetic field gradient sensing system shown;

[0121] Fig.10 for Figure 1 A schematic diagram of a wooden hollow sphere in the innermost layer of a non-metallic directional support in a full tensor high-order magnetic field gradient sensing system is shown;

[0122] Reference numerals:

[0123] 100. Magnetic field sensing probe; 110. Three-axis magnetic field sensor; 120. Wooden pole; 130. Wooden wedge; 200. Non-metallic directional bracket; 210. Hollow ceramic bearing; 300. High-strength engineering plastic shell. DETAILED DESCRIPTION

[0124] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0125] See also Figures 1 to 10 The present invention provides a full tensor high-order magnetic field gradient sensing system and a method of use, including a magnetic field sensing probe 100, a non-metallic directional bracket 200, a high-strength engineering plastic shell 300 and a communication antenna.

[0126] Specifically, the magnetic field sensing probe 100 includes a pure wood support frame, 15 three-axis magnetic field sensors 110 and a magnetic field acquisition, processing and communication module. The pure wood support frame is used to support the 15 three-axis magnetic field sensors 110 and the magnetic field acquisition, processing and communication module. In the coordinate system oxyz, the pure wood support frame has 9 installation nodes A, B, C, D, O, E, F, G, H distributed in a field shape in the xy plane, and 6 installation nodes I, J, K, L, M, N distributed in two rows in the xz plane, and the two rows of installation nodes are relatively located above and below the xy plane. The 15 three-axis magnetic field sensors 110 are located on the 15 installation nodes.

[0127] The magnetic field acquisition processing communication module is used to acquire, process and transmit the magnetic field data of 15 three-axis magnetic field sensors 110. When used specifically, the magnetic field acquisition processing communication module integrates magnetic field signal acquisition, data processing and communication, all of which are integrated into the module. The magnetic induction intensity data is acquired and processed into the first-order magnetic field gradient and the second-order magnetic field gradient, and then the longitude and latitude of the full tensor high-order magnetic field gradient sensing system and the azimuth of the coordinate system of the system and the geographic north are calculated, and the three-dimensional position of the underwater submarine is calculated, and then the longitude and latitude of the full tensor high-order magnetic field gradient sensing system, the angle between the coordinate system of the system and the geographic north, and the three-dimensional position of the underwater submarine are transmitted to the remote data system through the communication antenna.

[0128] The pure wood support frame includes a plurality of wood poles 120, and the plurality of wood poles 120 are connected to each other to form 15 installation nodes, and the 15 three-axis magnetic field sensors 110 are respectively installed on the 15 installation nodes. The distances between the adjacent installation nodes on the same wood pole 120 are equal. In specific implementation, the pure wood support frame can be formed by splicing wood poles to form a field-shaped frame and an I-shaped frame, and then splicing the field-shaped frame and the I-shaped frame to form a pure wood support frame, and the wood poles 120 are all connected by mortise and tenon joints, and no metal materials such as metal nails or bolts are used.

[0129] The specific methods can be:

[0130] In the coordinate system oxyz of the magnetic field sensor probe, the origin o is at the node O, the x-axis points to E along D, the z-axis points to M along J, and the y-axis points to G along B. The field-shaped frame is located in the xy plane, and the I-shaped frame is located in the xz plane.

[0131] Cross-shaped frame: It is composed of 6 wooden rods 120, including 9 nodes, namely A, B, C, D, O, E, F, G, and H. These 9 nodes are all in the same plane. The 6 wooden rods are AC rod, AF rod, FH rod, CH rod, BG rod, and DE rod. The AC rod, DE rod, and FH rod are parallel to each other and are all in the same plane. The AF rod, CH rod, and BG rod are parallel to each other and are all in the same plane. The 3 rods (AC rod, DE rod, and FH rod) are all perpendicular to the other 3 rods (AF rod, CH rod, and BG rod). The midpoint of the AC rod (i.e., 0.5 times the length of the rod) is node B, the midpoint of the AF rod (i.e., 0.5 times the length of the rod) is node D, the midpoint of the FH rod (i.e., 0.5 times the length of the rod) is node G, the midpoint of the CH rod (i.e., 0.5 times the length of the rod) is node E, the midpoint of the BG rod (i.e., 0.5 times the length of the rod) is node O, and the midpoint of the DE rod (i.e., 0.5 times the length of the rod) is node O. The connection lines between nodes A and C, nodes A and F, nodes F and H, and nodes C and H form a square, that is, the lengths of the 4 connection lines are the same.

[0132] In the plane where the cross-shaped frame is located, among the total 9 nodes, there are 4 right-angle nodes, namely A, C, F, and H; 4 T-shaped nodes, namely B, D, E, and G; and 1 cross node, which is O. One triaxial magnetic field sensor 110 is arranged at each node, and a total of 9 triaxial magnetic field sensors 110 are arranged.

[0133] I-shaped frame: It is composed of 3 wooden rods, including 6 nodes, namely I, J, K, L, M, and N. These 6 nodes are all in the same plane. The 3 wooden rods are IK rod, LN rod, and JM rod; the midpoint of the IK rod (i.e., 0.5 times the length of the rod) is node J, the midpoint of the LN rod (i.e., 0.5 times the length of the rod) is node M, and the midpoint of the JM rod (i.e., 0.5 times the length of the rod) is node O. In addition, the IK rod is parallel to the LN rod, and both the IK rod and the LN rod are perpendicular to the JM rod. Among the 6 nodes, there are 4 end nodes, namely I, K, L, and N; 2 T-shaped nodes, namely J and M. One triaxial magnetic field sensor 110 is arranged at each node, and a total of 6 triaxial magnetic field sensors 110 are arranged. The lengths of the connection lines between nodes L and N, nodes I and K, and nodes J and M are all equal.

[0134] In the plane where the cross-shaped frame is located, the O node is a cross node, that is, BG and DE are perpendicularly connected at the O point. On the other hand, since the cross-shaped frame and the I-shaped frame are connected at the O point, three wooden rods, namely the BG wooden rod, the DE wooden rod, and the JM wooden rod, are connected at the O point. Therefore, the O node is a double cross node in three-dimensional space, which is simply referred to as a cross node throughout the full text of this specification. At the cross node, the length of the line connecting nodes D and E is the same as the length of the line connecting nodes J and M. Therefore, the distance between two adjacent mounting nodes located on the same wooden rod is equal. The 15 triaxial magnetic field sensors are located on the 15 mounting nodes, that is, the distance between the triaxial magnetic field sensors on two adjacent mounting nodes on the same wooden rod is equal, which is d.

[0135] Among the 15 nodes, there are 4 end nodes, 4 right-angle nodes, 6 T-shaped nodes, and 1 cross node. Among them, the end node is the end of one wooden rod, the right-angle node is formed by connecting the ends of two wooden rods, the T-shaped node is formed by connecting the end of one wooden rod at the 0.5 length (i.e., the middle of the length of the wooden rod) of another wooden rod, and the cross node is formed by connecting three wooden rods at the 0.5 times the length (i.e., the middle of the length of the wooden rod) of each wooden rod.

[0136] When connecting two or more wooden rods, the mortise and tenon structure is adopted, and any metal materials such as metal nails or bolts are not used.

[0137] It should be noted that in specific implementation, a single triaxial magnetic field sensor 110 has low power consumption and ultra-small volume. After being encapsulated and protected by an ultra-thin engineering plastic, the dimensions in all three directions are in the millimeter level (less than 10 mm). Due to the ultra-small volume of a single triaxial magnetic field sensor 110, holes are directly drilled on the wooden rod of the sensing probe, and then a thin wooden wedge 130 is used for fixation.

[0138] The magnetic field sensing probe 100 is installed in the non-metallic directional bracket 200 through a pure wooden support frame, and the magnetic field sensing probe 100 can rotate within the non-metallic directional bracket so that the z-axis of the magnetic field sensing probe always remains vertically downward and unchanged.

[0139] In specific use, when the entire device rotates, rolls, or moves, the plane where the cross-shaped frame is located will remain in the horizontal plane but will rotate. MJ always remains in the vertically downward direction, then the z-axis always remains in the vertically downward direction, while the x-axis and the y-axis will rotate together in the same angle and the same direction. That is: the coordinate system oxyz of the magnetic field sensing probe is a dynamic coordinate system with the z-axis direction unchanged, while the two directions of the x-axis and the y-axis will change.

[0140] Specifically, the non-metallic directional bracket includes three wooden hollow spheres, and the three wooden hollow spheres are connected to each other freely from the inside to the outside through ceramic bearings and cylindrical wooden dowels. The pure wooden support frame is installed on the innermost wooden hollow spheres, and the outermost wooden hollow sphere is rotatably connected to the inner wall of the high-strength engineering plastic shell through ceramic bearings and cylindrical wooden dowels, and is concentrically arranged with the high-strength engineering plastic shell.

[0141] Specifically, the three wooden hollow balls include a first circular wooden ring and four second circular wooden rings, the first circular wooden ring and the four second circular wooden rings are spliced ​​to form a spherical wooden hollow ball, the first circular wooden ring has the same diameter as the wooden hollow ball; the diameters of the four second circular wooden rings are smaller than the diameter of the first circular wooden ring;

[0142] Among them, a ceramic bearing and a cylindrical wooden dowel are arranged at four positions evenly spaced 90 degrees on the first circular wooden ring of the wooden hollow spheres in the outermost layer and the middle layer, and the wooden hollow spheres in the outermost layer are rotatably connected to the high-strength engineering plastic shell through the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced 180 degrees apart, and the ceramic bearings and cylindrical wooden dowels arranged at the other two positions spaced 180 degrees apart on the wooden hollow spheres in the outer layer are rotatably connected to the wooden hollow spheres in the middle layer through the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced 180 degrees apart;

[0143] A ceramic bearing and a cylindrical wooden dowel are arranged at two positions 180 degrees apart on the first circular wooden ring of the innermost layer of the wooden hollow sphere. The ceramic bearings and cylindrical wooden dowels arranged at two positions of the innermost layer of the wooden hollow sphere can be rotatably connected with the other two ceramic bearings and cylindrical wooden dowels arranged at two positions 180 degrees apart on the wooden hollow sphere of the middle layer.

[0144] This method can facilitate the connection between the inner and outer wooden hollow balls, and can well realize the function of free rotation.

[0145] In the specific implementation, it can be made in the following way:

[0146] It is composed of three wooden balls, all of which are hollow inside and have a common center, the outermost wooden ball, the middle wooden ball and the innermost wooden ball. The spherical diameter of the outermost wooden ball is d max , the thickness of the outermost wooden sphere is d ma , the diameter of the wooden sphere in the middle is d mid , the thickness of the wooden sphere in the middle is d mi , the diameter of the innermost wooden sphere is dmin , the thickness of the innermost wooden sphere is d mn , the three diameters are the distance from the middle of the wood thickness of the spherical surface to the center of the ball. The net gap between the outermost wooden ball and the middle wooden ball is d1, and the net gap between the middle wooden ball and the innermost wooden ball is d2. Two net gaps can ensure that the three wooden balls will not touch each other during the rotation process. The sizes of the three wooden balls need to meet the requirements of the following two formulas:

[0147] d max -d mid >0.5d ma +0.5d mi +d1,

[0148] d mid -d min >0.5d mi +0.5d mn +d2.

[0149] The outermost wooden sphere is made up of a large wooden ring and four small wooden rings. The five wooden rings are located on a circle with a diameter of d. max The diameter of the large wooden ring is equal to the diameter of the sphere d. max The same. The large circular wooden ring of the outermost wooden ball has four cylindrical through holes, namely W1, W2, Z1 and Z2. The four cylindrical through holes are located on the large circular wooden ring, evenly distributed and spaced 90 degrees apart. Hollow ceramic bearings 210 are installed on the four cylindrical through holes, and cylindrical wooden dowels are fixed to the inner holes of the ceramic bearings 210. The cylindrical wooden dowels of the inner holes of the ceramic bearings 210 at W1 and W2 are fixed to the inner wall of the high-strength engineering plastic shell 300.

[0150] The cylindrical wooden dowels of the inner holes of the ceramic bearings 210 at Z1 and Z2 on the large circular wooden ring of the outermost wooden ball are fixed to the inner holes of the ceramic bearings 210 at Z3 and Z4 on the large circular wooden ring of the middle wooden ball.

[0151] The wooden sphere in the middle is made up of a large wooden ring and four small wooden rings. The five wooden rings are located in a circle with a diameter of d. mid The diameter of the large wooden ring is equal to the diameter of the sphere d. mid The large circular wooden ring of the wooden sphere in the middle is provided with four cylindrical through holes, namely N3, N4, Z3 and Z4, which are located on the large circular wooden ring, evenly distributed and spaced 90 degrees apart. Hollow ceramic bearings 210 are installed on the four cylindrical through holes, and cylindrical wooden tenons are fixed to the inner holes of the ceramic bearings 210.

[0152] The cylindrical wooden dowels of the inner holes of the ceramic bearing 210 at N3 and N4 on the large circular wooden ring of the wooden ball in the middle are fixed to the inner holes of the ceramic bearing 210 at N1 and N2 on the large circular wooden ring of the innermost wooden ball.

[0153] The innermost wooden sphere is composed of a large wooden ring and four small wooden rings. The five wooden rings are located in a circle with a diameter of d. min The diameter of the large wooden ring is equal to the diameter of the sphere d. min The same. The large circular wooden ring of the innermost wooden sphere is provided with two cylindrical through holes, namely N1 and N2. The two cylindrical through holes are located on the large circular wooden ring, evenly distributed, and spaced 180 degrees apart. Hollow ceramic bearings 210 are installed on the two cylindrical through holes N1 and N2, and cylindrical wooden dowels are fixed to the inner holes of the ceramic bearings 210. In the innermost wooden sphere, the large circular wooden ring and the two small circular wooden rings in the plumb direction have a total of four connections, of which the two nodes at the bottom connection are L0 and N0 respectively. The two small circular wooden rings in the plumb direction and the two small circular wooden rings on the horizontal plane have a total of eight connections, of which the four nodes at the bottom connection are A0, C0, F0, and H0 respectively. In the innermost wooden sphere, the six nodes (L0, N0, A0, C0, F0 and H0) are the connection points of the magnetic field sensor probe 100, and the nodes L, N, A, C, F and H of the pure wooden support frame of the magnetic field sensor probe 100 are respectively fixed at the nodes L0, N0, A0, C0, F0 and H0 of the innermost wooden sphere.

[0154] The three wooden balls are made of hard walnut. The parameters of walnut need to meet the following requirements: the density of walnut is >1000kg / m3, the Janka hardness is >16000N, the compressive strength is >70MPa, the modulus of rupture is >170MPa, and the elastic modulus is >15GPa. The radial and tangential shrinkage of the log is less than 8%, and the volume shrinkage is <15%.

[0155] Due to the properties of the non-metallic directional bracket, when the entire device rotates, rolls or moves, the plane where the field-shaped frame is located will remain in the horizontal plane but will rotate, and MJ will always remain in the direction of the plumb bob downward, then the z-axis will always be in the direction of the plumb bob downward, and the x-axis and y-axis will rotate together at the same angle and in the same direction. That is, the coordinate system oxyz of the magnetic field sensing probe 100 is a dynamic coordinate system in which the z-axis direction remains unchanged, while the directions of the x-axis and y-axis will change.

[0156] The high-strength engineering plastic shell 300 is wrapped around the non-metallic directional bracket, and the high-strength engineering plastic shell 300 has a spherical outer surface. The spherical shell is convenient for using the entire sensor on the water surface or uneven ground, and the spherical shell can automatically adapt to the external environment.

[0157] The communication antenna is covered on the shell, and is used to receive the magnetic field data transmitted by the magnetic field acquisition and processing communication module and transmit it to the remote data acquisition system. Specifically, the communication antenna is a metal mesh wrapped in the shell, which can adapt to the spherical high-strength engineering plastic shell shape. Of course, in other embodiments, the communication antenna can be in other forms. In specific implementation, galvanized copper wire and galvanized molybdenum wire can be interwoven and woven into a twisted pair, and then the twisted pair can be woven into a metal mesh, and the metal mesh can be used as a communication antenna.

[0158] As a preferred embodiment, the sensor system further includes a plurality of solar cells, which are spliced ​​into a grid and covered on a high-strength engineering plastic shell, and a metal mesh formed by a communication antenna covers the grid-shaped splicing of the solar cells. The solar cells can provide power for other components.

[0159] The specific method of using the full tensor high-order magnetic field gradient sensing system is as follows:

[0160] S110, placing the full tensor high-order magnetic field gradient sensor system on the sea surface in a floating state to measure the position of the underwater submarine;

[0161] Specifically, since the full tensor high-order magnetic field gradient sensor system is made of wood poles, plastics, etc., the overall density is much smaller than water, and it can float on the sea surface. When it is necessary to locate an underwater submarine, the full tensor high-order magnetic field gradient sensor system is directly placed on the sea surface and can be in a floating state. When performing single-point measurement, the full tensor high-order magnetic field gradient sensor system can be placed at the target position; if it is necessary to measure in the ocean, the full tensor high-order magnetic field gradient sensor system can be placed in the water to float on the water surface; when locating surface / underwater target objects such as ships, a number of full tensor high-order magnetic field gradient sensor systems can be directly thrown and floated on the surface of the ocean. If it is necessary to locate explosives such as bombs and mines deep underground, the full tensor high-order magnetic field gradient sensor system can be placed at a safe distance away from the target position.

[0162] S120, calculating the complete first-order magnetic field gradient by using the magnetic induction intensity measured by the three-axis magnetic field sensor;

[0163] The specific operation method is:

[0164] Set the magnetic induction intensity B, including three scalars B x , B y and B z The first-order magnetic field gradient G is in the form of a matrix with 3 rows and 3 columns, including 9 parameters, which can be expressed as 3 vectors, namely G x , G y and G z, each vector contains 3 scalars. The second-order magnetic field gradient H is composed of 3 matrices, namely H x , H y and H z . Each matrix contains 9 scalars.

[0165] The gradient of magnetic induction intensity B along the x direction is B xx , B yx and B zx , that is, the magnetic field gradient G x

[0166]

[0167] The gradient of magnetic induction intensity B along the y direction is B xy , B yy and B zy , that is, the magnetic field gradient G y

[0168]

[0169] The gradient of magnetic induction intensity B along the z direction is B xz , B yz and B zz , that is, the magnetic field gradient G z

[0170]

[0171] The first-order magnetic field gradient G is a symmetric matrix, B xy -B yx =0, B xz -B zx =0, B yz -B zy = 0. Its trace traceG = B xx +B yy +B zz = 0, so among the 9 elements of the magnetic field gradient tensor, only 5 elements are independent, namely B xx , B xy , Bxz, B yy , B yz .

[0172] The magnetic field gradient is calculated by differentiating the magnetic induction intensity measured by the three-axis magnetic field sensor at two positions, and then multiple magnetic field gradients are averaged.

[0173] B i is the magnetic induction intensity vector measured by the three-axis magnetic field sensor at point i. Point i can be A, B, C, D, E, F, G, H, I, J, K, L, M, N, O nodes, B xi , B yi, and B xz They are the magnetic induction intensity vector B i The three components.

[0174] G xj is the first-order magnetic field gradient of the magnetic induction intensity along the x direction at point j, G yj is the first-order magnetic field gradient of the magnetic induction intensity along the y direction at point j, G zj is the first-order magnetic field gradient of the magnetic induction intensity along the z direction at point j. Point j can be B, D, E, G, M, J, P, Q, R, S, T, or W.

[0175] The distance between two adjacent installation nodes on the same wooden pole is equal, and the 15 three-axis magnetic field sensors are located on the 15 installation nodes, that is, the distance between the three-axis magnetic field sensors on two adjacent installation nodes on the same wooden pole is equal, which is d.

[0176] The magnetic field gradient G can be calculated by measuring the magnetic induction intensity of the three-axis magnetic field sensors at points A and C, D and E, F and H, L and N, and I and K. x , in order to reduce the error, average it and calculate it as follows:

[0177]

[0178] The magnetic field gradient G can be calculated by measuring the magnetic induction intensity of the three-axis magnetic field sensors at points A and F, points B and G, and points C and H. y , in order to reduce the error, average it and calculate it as follows:

[0179]

[0180] The magnetic field gradient G can be calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points I and L, J and M, and K and N. z , in order to reduce the error, average it and calculate it as follows:

[0181]

[0182] S130, calculating the complete second-order magnetic field gradient by the magnetic induction intensity measured by the three-axis magnetic field sensor, the specific method is as follows:

[0183] Set the first-order magnetic field gradient G along the x direction, that is, G x , G y and G z The gradient along the x direction, denoted as H xxx , H yxx , H zxx , H xyx , H yyx , Hzyx , H xzx , H yzx , H zzx , that is, the second-order magnetic field gradient H x :

[0184]

[0185] The main diagonal elements satisfy H xxx +H yyx +H zzx =0,H x The matrix is ​​a symmetric matrix, H x There are 9 parameters in the matrix, but only 5 independent parameters, namely H xxx , H xyx , H xzx , H yyx and H yzx .

[0186] The first-order magnetic field gradient G is the gradient along the y direction, that is, G x , G y and G z The gradient along the y direction, denoted as H xxy , H yxy , H zxy , H xyy , H yyy , H zyy , H xzy , H yzy , H zzy , that is, the second-order magnetic field gradient H y :

[0187]

[0188] The main diagonal elements satisfy H xxy +H yyy +H zzy =0,H y The matrix is ​​a symmetric matrix, H y There are 9 parameters in the matrix, but only 5 independent parameters, namely H xxy , H xyy , H xzy , H yyy and H yzy ;

[0189] The first-order magnetic field gradient G is the gradient along the z direction, that is, G x , G y and G z The gradient along the z direction, denoted as H xyz , H yxz , H zxz , H xyz, H yyz , H zyz , H xzz , H yzz , H zzz , that is, the second-order magnetic field gradient H z :

[0190]

[0191] The main diagonal elements satisfy H xxz +H yyz +H zzz =0,H z The matrix is ​​a symmetric matrix, H z There are 9 parameters in the matrix, but only 5 independent parameters, namely H xxz , H xyz , H xzz , H yyz and H yzz ;

[0192] According to the spatial arrangement of the three-axis magnetic sensor and the definition of the second-order magnetic field gradient tensor, the second-order magnetic field gradient tensors at the origin O of the coordinate system are respectively;

[0193] First, the first-order magnetic field gradient G at points Q and P is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensor at points E and O, and points O and D. x The first-order magnetic field gradient G at points E and D is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points C and H, and points A and F. y The first-order magnetic field gradient G at points E and D is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points K and N, L and I. z ;

[0194] Among them, point Q is the center of the line connecting points E and O, point P is the center of the line connecting points O and D, and the first-order magnetic field gradient G passing through points Q and P is x The first-order magnetic field gradient G at points E and D y The first-order magnetic field gradient G at points E and D z , respectively calculate the magnetic field gradient G x , G y and G z The magnetic field gradient along the x direction, that is, the second-order magnetic field gradient H x , calculated as follows:

[0195]

[0196] First, the first-order magnetic field gradient G at points G and B is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points H and F, and points A and C. xThe first-order magnetic field gradient G at points S and R is calculated by using the magnetic induction intensity measured by the three-axis magnetic field sensors at points G and O, and points O and B. y The first-order magnetic field gradient G at points E and D is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points K and N, L and I. z .

[0197] Among them, point R is the center of the line connecting points O and B, point S is the center of the line connecting points G and O, and then the first-order magnetic field gradient G x The first-order magnetic field gradient G at points S and R y , respectively calculate the magnetic field gradient G x and G y The magnetic field gradient along the y direction. G z The magnetic field gradient along the y direction (H xzy , H yzy , H zzy ) and G x The magnetic field gradient along the y direction (H xxy , H yxy , H zxy ) in the third parameter H zxy , G y The magnetic field gradient along the y direction (H xyy , H yyy , H zyy ) in the third parameter H zyy , G z The magnetic field gradient along the z direction (H xzz , H yzz , H zzz ) in the second parameter H yzz The same is indicated by *. Magnetic field gradient G x , G y and G z The magnetic field gradient along the y direction, that is, the second-order magnetic field gradient H y , calculated as follows:

[0198]

[0199] In the formula, * indicates the parameters in the vector and H x , H y , H z The other parameters in are repeated and do not need to be solved again.

[0200] Point T is the center of the line connecting points M and O, and point W is the center of the line connecting points O and J;

[0201] First, the first-order magnetic field gradient G at points M and J is calculated by using the magnetic induction intensity measured by the three-axis magnetic field sensors at points N and L, and points K and I. xThe first-order magnetic field gradient G at points T and W is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points M and O, and points O and J. z Then the first-order magnetic field gradient G at points M and J x The first-order magnetic field gradient G at points T and W z , respectively calculate the magnetic field gradient G x and G z Magnetic field gradient along the z direction; G y The magnetic field gradient along the z direction (H xyz , H yyz , H zyz ) and G z The magnetic field gradient along the x direction (H xzx , H yzx , H zzx ) in the second parameter H yzx , G y The magnetic field gradient along the y direction (H xyy , H yyy , H zyy ) in the third parameter H zyy , G z The magnetic field gradient along the z direction (H xzz , H yzz , H zzz ) in the second parameter H yzz The same is indicated by **. Magnetic field gradient G x , G y and G z The magnetic field gradient along the z direction, that is, the second-order magnetic field gradient H z , calculated as follows:

[0202]

[0203] In the formula, ** indicates the parameters in the vector and H x , H y , H z The other parameters in are repeated and do not need to be solved again;

[0204] S140, calculating the three-dimensional position vector from the magnetic field sensing probe 100 to the underwater submarine through the first-order magnetic field gradient and the second-order magnetic field gradient, the specific method is as follows:

[0205] The first-order magnetic field gradient G along the x direction x and the second-order magnetic field gradient H x , get the three-dimensional position vector of the underwater submarine

[0206] r=-4(H x ) -1 G x (14)

[0207] r is the position vector, and the three-dimensional position of the underwater submarine in the coordinate system oxyz is r(x, y, z).

[0208] Similarly, by finding the first-order magnetic field gradient G in the y direction y and the second-order magnetic field gradient H y , we can get the three-dimensional position vector of the underwater submarine:

[0209] r=-4(H y ) -1 G y (15)

[0210] Similarly, by finding the first-order magnetic field gradient G in the z direction z and the second-order magnetic field gradient H z , we can get the three-dimensional position vector of the underwater submarine

[0211] r=-4(H z ) -1 G z (16)

[0212] By averaging the three-dimensional position vectors of the underwater submarine obtained from the first-order and second-order magnetic field gradients along the x, y and z directions, we can obtain

[0213]

[0214] S150, providing geographical parameters such as longitude and latitude of the location of the magnetic field sensor probe 100;

[0215] The specific method is:

[0216] The magnetic induction intensity B measured by the three-axis magnetic field sensor at point O xO , B yO and B zO , where B zO is the magnetic induction intensity in the plumb bob direction, B xO and B yO It is the horizontal magnetic induction intensity. By comparing it with the built-in geomagnetic map (geomagnetic map, which can use public national geomagnetic data and global geomagnetic data), it gives the magnetic declination. There are three geographical parameters, namely longitude λ and latitude Ψ. Among them, the magnetic declination is positive when it is north-east and negative when it is north-west.

[0217] Geographical north is the direction of the meridian toward the North Pole. Geomagnetic north is the north of the Earth's magnetic pole, which is the north direction indicated by the compass. The declination between geomagnetic north and geographic north is called magnetic declination.

[0218] S160, the specific method for giving the angle between the coordinate system of the magnetic field sensor probe 100 and the geographic north is:

[0219] According to the latitude and longitude, the magnetic induction intensity is recalculated and compared with the actually measured magnetic induction intensity to give the azimuth, which is the angle between the x-axis of the coordinate system of the magnetic field sensor probe and the geographic north. The International Geomagnetic Reference Field (IGRF) is a standard global model that describes the main magnetic field of the Earth. In the IGRF model, the magnetic potential of the main magnetic field (i.e., the internal source field) can be expressed by spherical harmonic functions:

[0220]

[0221] Where r is the distance from the center of the earth at any point, λ is the longitude, θ is the co-latitude, θ=90-Ψ, Ψ is the latitude, is the Schmidt quasi-normalized associated Legendre function, is the spherical harmonic series coefficient of the internal source field magnetic potential.

[0222] The geomagnetic coordinate system is defined as OXYZ, where the north horizontal component is the X axis, the east horizontal component is the Y axis, and the plumb downward component is the Z axis, and the right-hand criterion is satisfied. In the geomagnetic coordinate system OXYZ, according to the longitude and latitude, the differential of the magnetic potential spherical harmonic function along the axial direction is calculated, and the three components of the magnetic induction intensity of the geomagnetic field are calculated as follows:

[0223]

[0224] Where R is the radius of the international reference sphere, that is, the average radius of the earth (R = 6371.2 km). are the nth-order and mth-order Gaussian spherical harmonic coefficients, which are taken according to the 11th generation IGRF, and N is the cutoff order (N = 10 in this paper).

[0225] The specific values ​​of the parameters in formula (18)-(21), such as r, m, n, The value of can be found in many published documents and will not be elaborated here.

[0226] For example, CC Finlay, S. Maus, CD Beggan, TNBondar, A. Chambodut, et al. International Geomagnetic Reference Field: the eleventh generation[J], Geophysical Journal International, 2010, 183, 1216–1230.

[0227] The angle between the x-axis and the geomagnetic north direction in the coordinate system of the magnetic field sensor probe is calculated as follows:

[0228]

[0229] In the coordinate system of the magnetic field sensor probe 100, the angle between the x-axis and the geographic north is north by east. The z-axis is plumb downward and the y-axis conforms to the right-hand rule.

[0230] S170. The specific method for providing the three-dimensional position of the underwater submarine is:

[0231] The location of the full tensor high-order magnetic field gradient sensor system, latitude Ψ, longitude λ. At this location, in the coordinate system of the magnetic field sensor probe, the angle between the x-axis and the geographic north is: east of north The z-axis is the plumb bob pointing downward, and the y-axis conforms to the right-hand rule. In this coordinate system, the three-dimensional position vector of the underwater submarine is r.

[0232] S180, transmit the location of the full tensor high-order magnetic field gradient sensor system in the sea, the angle between the coordinate system of the magnetic field sensor probe and the geographic north, and the three-dimensional position of the underwater submarine to a remote data system.

[0233] The specific method is:

[0234] By means of remote communication, the sea location of the full tensor high-order magnetic field gradient sensor system, the angle between the magnetic field sensor probe coordinate system and the geographic north, and the three-dimensional position of the underwater submarine are transmitted to a distant data system.

[0235] The above full tensor high-order magnetic field gradient sensing system and method of use:

[0236] The advantages are as follows:

[0237] The above-mentioned full tensor high-order magnetic field gradient sensing system and use method, the sensing system includes a magnetic field sensing probe 100, a non-metallic directional bracket 200 and a high-strength engineering plastic shell 300, the magnetic field acquisition and processing and communication modules in the magnetic field sensing probe 100 are powered by the solar cell of the high-strength engineering plastic shell 300, and the z-axis in the coordinate system of the magnetic field sensing probe 100 is always plumb downward through the non-metallic directional bracket 200. The magnetic induction intensity of the underwater submarine is obtained by the three-axis magnetic field sensor 110 in the magnetic field sensing probe 100, and then the first-order magnetic field gradient and the second-order magnetic field gradient are calculated. The magnetic induction intensity is compared with the built-in geomagnetic map to obtain the longitude and latitude of the sea location where the full tensor high-order magnetic field gradient sensing system is located and the angle between the coordinate system of the magnetic field sensing probe and the geographic north. The three-dimensional position of the underwater submarine is obtained through the first-order magnetic field gradient and the second-order magnetic field gradient. The longitude, latitude, angle between the coordinate system of the magnetic field sensor probe and the geographic north, and the three-dimensional position of the underwater submarine of the full tensor high-order magnetic field gradient sensor system at the sea are sent to the remote data receiving system through the communication antenna of the high-strength engineering plastic shell 300.

[0238] The full tensor high-order magnetic field gradient sensing system can completely measure 9 parameters of the first-order magnetic field gradient and 27 parameters of the second-order magnetic field gradient. In addition to the magnetic field acquisition and processing communication module, the non-metallic directional bracket 200, the pure wooden support frame of the magnetic field sensor probe 100 and the high-strength engineering plastic shell 300 in the sensing system do not contain any metal materials such as metal nails, metal rods, metal screws, etc., completely eliminating electromagnetic interference. Without the help of any auxiliary positioning means such as GPS, the full tensor high-order magnetic field gradient sensing system can obtain its own position and the three-dimensional position of target objects such as underwater submarines.

[0239] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A full tensor high-order magnetic field gradient sensing system, characterized in that: include: A magnetic field sensing probe, comprising a pure wood support frame, 15 three-axis magnetic field sensors and a magnetic field acquisition, processing and communication module, wherein the pure wood support frame is used to support the 15 three-axis magnetic field sensors and the magnetic field acquisition, processing and communication module, and in a coordinate system oxyz, the pure wood support frame has 9 installation nodes A, B, C, D, O, E, F, G, H distributed in a field shape in an xy plane, and has 6 installation nodes I, J, K, L, M, N distributed in two rows in an xz plane, and the two rows of installation nodes are relatively located above and below the xy plane, the 15 three-axis magnetic field sensors are located on the 15 installation nodes, and the magnetic field acquisition, processing and communication module is used to collect, process and transmit magnetic field data of the 15 three-axis magnetic field sensors; A non-metallic directional support, wherein the magnetic field sensor probe is installed in the non-metallic directional support through the pure wood support frame; and the magnetic field sensor probe can rotate in the non-metallic directional support so that the z-axis of the magnetic field sensor probe is always kept with the plumb bob downward; A high-strength engineering plastic shell, wherein the high-strength engineering plastic shell is wrapped outside the non-metallic directional bracket, and the outer surface of the high-strength engineering plastic shell is spherical; and The communication antenna is covered on the high-strength engineering plastic shell and is used to receive the magnetic field data transmitted by the magnetic field acquisition and processing communication module and transmit it to the remote data system.

2. The full tensor high-order magnetic field gradient sensing system and method of use according to claim 1, characterized in that: The pure wood support frame includes a plurality of wood poles, which are interconnected to form 15 installation nodes. The 15 three-axis magnetic field sensors are respectively installed on the 15 installation nodes, and the distance between two adjacent installation nodes on the same wood pole is equal.

3. The full tensor high-order magnetic field gradient sensing system and method of use according to claim 2, characterized in that: The plurality of wooden poles are mutually mortise and tenoned.

4. The full tensor high-order magnetic field gradient sensing system according to claim 1, characterized in that: The non-metallic directional bracket includes three wooden hollow spheres, which are connected to each other freely from the inside to the outside through ceramic bearings and cylindrical wooden dowels. The pure wooden support frame is installed on the innermost wooden hollow spheres, and the outermost wooden hollow sphere is rotatably connected to the inner wall of the high-strength engineering plastic shell through ceramic bearings and cylindrical wooden dowels, and is concentrically arranged with the high-strength engineering plastic shell.

5. The full tensor high-order magnetic field gradient sensing system according to claim 4, characterized in that: The three wooden hollow balls each include a first circular wooden ring and four second circular wooden rings, the first circular wooden ring and the four second circular wooden rings are spliced ​​to form a spherical wooden hollow ball, the first circular wooden ring has the same diameter as the wooden hollow ball; the diameters of the four second circular wooden rings are smaller than the diameter of the first circular wooden ring; Among them, one ceramic bearing and one cylindrical wooden dowel are arranged at four positions evenly spaced 90 degrees on the first circular wooden rings of the wooden hollow spheres of the outermost layer and the middle layer, and the wooden hollow spheres of the outermost layer are rotatably connected to the high-strength engineering plastic shell through the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced 180 degrees apart, and the ceramic bearings and cylindrical wooden dowels arranged at the other two positions spaced 180 degrees apart on the wooden hollow spheres of the outer layer are rotatably connected to the wooden hollow spheres of the middle layer through the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced 180 degrees apart; A ceramic bearing and a cylindrical wooden dowel are arranged at two positions 180 degrees apart on the first circular wooden ring of the innermost layer of the wooden hollow sphere. The innermost layer of the wooden hollow sphere can be rotatably connected with the other two ceramic bearings and cylindrical wooden dowels arranged at positions 180 degrees apart on the wooden hollow sphere of the middle layer through the ceramic bearings and cylindrical wooden dowels arranged at the two positions.

6. The full tensor high-order magnetic field gradient sensing system and method of use according to claim 1, characterized in that: The communication antenna is a metal mesh wrapped in the high-strength engineering plastic shell.

7. The full tensor high-order magnetic field gradient sensing system and method of use according to claim 6, characterized in that: The metal mesh comprises galvanized copper wires and galvanized molybdenum wires, the copper wires and the molybdenum wires are interwoven and woven into twisted pairs, and the twisted pairs are woven into the metal mesh.

8. The full tensor high-order magnetic field gradient sensing system and method of use according to claim 7, characterized in that: It also includes a plurality of solar cells, which are spliced ​​into a grid-like shape and covered on the high-strength engineering plastic shell, and the metal mesh formed by the communication antenna covers the grid-like splicing of the solar cells.

9. A method for using a full tensor high-order magnetic field gradient sensing system, characterized in that: A method using the full tensor high-order magnetic field gradient sensing system according to any one of claims 1 to 8, comprising: The full tensor high-order magnetic field gradient sensing system is placed on the sea surface in a floating state to measure the position of an underwater submarine; The complete first-order magnetic field gradient is obtained by calculating the magnetic induction intensity measured by the three-axis magnetic field sensor; The complete second-order magnetic field gradient is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensor; The three-dimensional position vector from the magnetic field sensor probe to the underwater submarine is calculated through the first-order magnetic field gradient and the second-order magnetic field gradient; Provide the longitude and latitude geographic parameters of the location of the magnetic field sensor probe; Give the angle between the coordinate system of the magnetic field sensor probe and the geographic north; Give the three-dimensional position of the underwater submarine; The location of the full tensor high-order magnetic field gradient sensor system in the sea, the angle between the coordinate system of the magnetic field sensor probe and the geographic north, and the three-dimensional position of the underwater submarine are sent to a distant data system.

10. The method for using the full tensor high-order magnetic field gradient sensing system according to claim 9, characterized in that: The specific method for calculating the complete first-order magnetic field gradient using the magnetic induction intensity measured by the three-axis magnetic field sensor is as follows: Set the magnetic induction intensity B, including three scalars B x , B y and B z , the first-order magnetic field gradient G, is in the form of a 3-row 3-column matrix, including 9 parameters, which can be expressed as 3 vectors, namely G x , G y and G z , each vector contains three scalars; the second-order magnetic field gradient H is three matrices, namely H x , H y and H z , each matrix contains 9 scalars; The gradient of magnetic induction intensity B along the x direction is B xx , B yx and B zx , that is, the magnetic field gradient G x The gradient of magnetic induction intensity B along the y direction is B xy , B yy and B zy , that is, the magnetic field gradient G y The gradient of magnetic induction intensity B along the z direction is B xz , B yz and B zz , that is, the magnetic field gradient G z The first-order magnetic field gradient G is a symmetric matrix, B xy -B yx =0, B xz -B zx =0, B yz -B zy =0, its trace traceG=B xx +B yy +B zz = 0, so among the 9 elements of the magnetic field gradient tensor, only 5 elements are independent, namely B xx , B xy , B xz , B yy , B yz ; The magnetic field gradient is calculated by differentiating the magnetic induction intensity measured by the three-axis magnetic field sensor at two locations, and then the multiple magnetic field gradients are averaged; It is set that the distance between the three-axis magnetic field sensors on two adjacent installation nodes on the same wooden pole is d; B i is the magnetic induction intensity vector measured by the three-axis magnetic field sensor at point i. Point i can be A, B, C, D, E, F, G, H, I, J, K, L, M, N, O nodes, B xi , B yi , and B xz They are the magnetic induction intensity vector B i The three components of G xj is the first-order magnetic field gradient of the magnetic induction intensity along the x direction at point j, G yj is the first-order magnetic field gradient of the magnetic induction intensity along the y direction at point j, G zj is the first-order magnetic field gradient of the magnetic induction intensity along the z direction at point j. Point j can be B, D, E, G, M, J, P, Q, R, S, T, or W; The magnetic field gradient G can be calculated by measuring the magnetic induction intensity of the three-axis magnetic field sensors at points A and C, D and E, F and H, L and N, and I and K. x , in order to reduce the error, average it and calculate it as follows: The magnetic field gradient G can be calculated by measuring the magnetic induction intensity of the three-axis magnetic field sensors at points A and F, points B and G, and points C and H. y , in order to reduce the error, average it and calculate it as follows: The magnetic field gradient G can be calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points I and L, J and M, and K and N. z , in order to reduce the error, average it and calculate it as follows: The specific method for calculating the complete second-order magnetic field gradient using the magnetic induction intensity measured by the three-axis magnetic field sensor is: Set the first-order magnetic field gradient G along the x direction, that is, G x , G y and G z The gradient along the x direction, denoted as H xxx , H yxx , H zxx , H xyx , H yyx , H zyx , H xzx , H yzx , H zzx , that is, the second-order magnetic field gradient H x : The main diagonal elements satisfy H xxx +H yyx +H zzx =0,H x The matrix is ​​a symmetric matrix, H x There are 9 parameters in the matrix, but only 5 independent parameters, namely H xxx , H xyx , H xzx , H yyx and H yzx ; The first-order magnetic field gradient G is the gradient along the y direction, that is, G x , G y and G z The gradient along the y direction, denoted as H xxy , H yxy , H zxy , H xyy , H yyy , H zyy , H xzy , H yzy , H zzy , that is, the second-order magnetic field gradient H y : The main diagonal elements satisfy H xxy +H yyy +H zzy =0,H y The matrix is ​​a symmetric matrix, H y There are 9 parameters in the matrix, but only 5 independent parameters, namely H xxy , H xyy , H xzy , H yyy and H yzy ; The first-order magnetic field gradient G is the gradient along the z direction, that is, G x , G y and G z The gradient along the z direction, denoted as H xyz , H yxz , H zxz , H xyz , H yyz , H zyz , H xzz , H yzz , H zzz , that is, the second-order magnetic field gradient H z : The main diagonal elements satisfy H xxz +H yyz +H zzz =0,H z The matrix is ​​a symmetric matrix, H z There are 9 parameters in the matrix, but only 5 independent parameters, namely H xxz , H xyz , H xzz , H yyz and H yzz ; According to the spatial arrangement of the three-axis magnetic sensor and the definition of the second-order magnetic field gradient tensor, the second-order magnetic field gradient tensors at the origin o of the coordinate system are respectively; First, the first-order magnetic field gradient G at points Q and P is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensor at points E and O, and points O and D. x The first-order magnetic field gradient G at points E and D is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points C and H, and points A and F. y The first-order magnetic field gradient G at points E and D is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points K and N, L and I. z ; Among them, point Q is the center of the line connecting points E and O, point P is the center of the line connecting points O and D, and the first-order magnetic field gradient G passing through points Q and P is x The first-order magnetic field gradient G at points E and D y The first-order magnetic field gradient G at points E and D z , respectively calculate the magnetic field gradient G x , G y and G z The magnetic field gradient along the x direction, that is, the second-order magnetic field gradient H x , calculated as follows: First, the first-order magnetic field gradient G at points G and B is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points H and F, and points A and C. x The first-order magnetic field gradient G at points S and R is calculated by using the magnetic induction intensity measured by the three-axis magnetic field sensors at points G and O, and points O and B. y The first-order magnetic field gradient G at points E and D is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points K and N, L and I. z ; Among them, R is the center of the line connecting points O and B, S is the center of the line connecting points G and O, and the first-order magnetic field gradient G passing through points G and B is x The first-order magnetic field gradient G at points S and R y , respectively calculate the magnetic field gradient G x and G y The magnetic field gradient along the y direction, G z The magnetic field gradient along the y direction (H xzy , H yzy , H zzy ) respectively with G x The magnetic field gradient along the y direction (H xxy , H yxy , H zxy ) in the third parameter H zxy , G y The magnetic field gradient along the y direction (H xyy , H yyy , H zyy ) in the third parameter H zyy , G z The magnetic field gradient along the z direction (H xzz , H yzz , H zzz ) in the second parameter H yzz Same, * is used to indicate the magnetic field gradient G x , G y and G z The magnetic field gradient along the y direction, that is, the second-order magnetic field gradient H y , calculated as follows: In the formula, * indicates the parameters in the vector and H x , H y and H z The other parameters in are repeated and do not need to be solved again; Point T is the center of the line connecting points M and O, and point W is the center of the line connecting points O and J; First, the first-order magnetic field gradient G at points M and J is calculated by using the magnetic induction intensity measured by the three-axis magnetic field sensors at points N and L, and points K and I. x The first-order magnetic field gradient G at points T and W is calculated by the magnetic induction intensity measured by the three-axis magnetic field sensors at points M and O, and points O and J. z ; Then the first-order magnetic field gradient G passing through points M and J x The first-order magnetic field gradient G at points T and W z , respectively calculate the magnetic field gradient G x and G z Magnetic field gradient along the z direction; G y The magnetic field gradient along the z direction (H xyz , H yyz , H zyz ) respectively with G z The magnetic field gradient along the x direction (H xzx , H yzx , H zzx ) in the second parameter H yzx , G y The magnetic field gradient along the y direction (H xyy , H yyy , H zyy ) in the third parameter H zyy , G z The magnetic field gradient along the z direction (H xzz , H yzz , H zzz ) in the second parameter H yzz Same, ** is used to represent the magnetic field gradient G x , G y and G z The magnetic field gradient along the z direction, that is, the second-order magnetic field gradient H z , calculated as follows: In the formula, ** indicates the parameters in the vector and H x , H y and H z The other parameters in are repeated and do not need to be solved again; The specific method for calculating the three-dimensional position vector from the magnetic field sensor probe to the underwater submarine through the first-order magnetic field gradient and the second-order magnetic field gradient is: The first-order magnetic field gradient G along the x direction x and the second-order magnetic field gradient H x , get the three-dimensional position vector of the underwater submarine: r=-4(H x ) -1 G x (14) r is the position vector, with the three-dimensional position of the underwater submarine in the coordinate system oxyz as r(x, y, z); By finding the first-order magnetic field gradient G in the y direction y and the second-order magnetic field gradient H y , we can get the three-dimensional position vector of the underwater submarine: r=-4(H y ) -1 G y (15) By finding the first-order magnetic field gradient G in the z direction z and the second-order magnetic field gradient H z , we can get the three-dimensional position vector of the underwater submarine: r=-4(H z ) -1 G z (16) By averaging the three-dimensional position vectors of the underwater submarine obtained from the first-order and second-order magnetic field gradients along the x, y and z directions, we can obtain The specific method for giving the geographical parameters such as longitude and latitude of the location of the magnetic field sensor probe is: The magnetic induction intensity B measured by the three-axis magnetic field sensor at point O xO , B yO and B zO , by comparing with the built-in geomagnetic map, giving the magnetic declination Three geographical parameters: longitude λ, latitude Ψ; Among them, B zO is the magnetic induction intensity in the plumb bob direction, B xO and B yO It is the magnetic induction intensity in the horizontal direction. The magnetic declination is positive when it is east of the north and negative when it is west of the north. Among them, the geographic north is the direction of the meridian toward the North Pole, the geomagnetic north is the north of the earth's magnetic pole, that is, the north direction indicated by the compass. The declination between the geomagnetic north and the geographic north is the magnetic declination. The specific method to give the angle between the coordinate system of the magnetic field sensor probe and the geographic north is: Recalculate the magnetic induction intensity based on the latitude and longitude, compare it with the actually measured magnetic induction intensity, and give the angle between the x-axis of the coordinate system of the magnetic field sensor probe and the geographic north; The International Geomagnetic Reference Field (IGRF) is a standard global model that describes the Earth's main magnetic field. In the IGRF model, the magnetic potential of the main magnetic field (i.e., the internal source field) can be expressed by spherical harmonics: Where r is the distance from the center of the earth at any point, λ is the longitude, θ is the co-latitude, θ=90-Ψ, Ψ is the latitude, is the Schmidt quasi-normalized associated Legendre function, is the spherical harmonic series coefficient of the internal source field magnetic potential; The geomagnetic coordinate system is defined as OXYZ, where the north horizontal component is the X axis, the east horizontal component is the Y axis, and the plumb downward component is the Z axis, and the right-hand criterion is satisfied. In the geomagnetic coordinate system OXYZ, according to the longitude and latitude, the differential of the magnetic potential spherical harmonic function along the axial direction is calculated to obtain the three components of the magnetic induction intensity of the geomagnetic field: Where R is the radius of the international reference sphere, that is, the average radius of the earth (R = 6371.2 km). is the nth order mth order Gaussian spherical harmonic coefficient, which is taken according to the 11th generation IGRF, N is the cutoff order, N = 10; The specific values ​​of the parameters in formula (18)-(21), such as r, m, n, The value of can be found in many published documents and will not be elaborated here; The angle between the x-axis and the geomagnetic north direction in the coordinate system of the magnetic field sensor probe is calculated as follows: In the coordinate system of the magnetic field sensor probe, the angle between the x-axis and the geographic north is north by east. The z-axis is plumb downward, and the y-axis conforms to the right-hand rule; The specific method of giving the three-dimensional position vector of an underwater submarine is: The full tensor high-order magnetic field gradient sensing system is located at latitude Ψ and longitude λ. At this location, in the coordinate system of the magnetic field sensor probe, the angle between the x-axis and the geographic north is: east of north The z-axis is the plumb bob pointing downward, and the y-axis conforms to the right-hand rule. In this coordinate system, the three-dimensional position vector of the underwater submarine is r; The specific method of transmitting the position of the full tensor high-order magnetic field gradient sensor system in the sea, the angle between the coordinate system of the magnetic field sensor probe and the geographic north, and the three-dimensional position of the underwater submarine to a remote data system is as follows: By means of remote communication, the longitude and latitude of the sea where the full tensor high-order magnetic field gradient sensor system is located, the angle between the coordinate system of the magnetic field sensor probe and the geographic north, and the three-dimensional position vector of the underwater submarine are transmitted to the remote data system.

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