A full-tensor high-order magnetic field gradient sensing system and method of use

Abstract

This invention discloses a full-tensor high-order magnetic field gradient sensing system and its usage method. The full-tensor high-order magnetic field gradient sensing system includes a magnetic field sensing probe, a non-metallic directional support, a high-strength engineering plastic shell, and a communication antenna. The magnetic field sensing probe includes a pure wood support frame, 15 triaxial magnetic field sensors, and a magnetic field acquisition, processing, and communication module. Nine triaxial magnetic field sensors are arranged in a crisscross pattern in the xy-plane, and six triaxial magnetic field sensors are arranged in two rows in the xz-plane. The magnetic field sensing probe is mounted in the non-metallic directional support frame via the pure wood support frame, and the z-axis of the magnetic field probe is always kept vertically downward. The plastic-sealed shell encloses the directional support, and the communication antenna covers the shell. Using this full-tensor high-order magnetic field gradient sensing system and method, all first-order and second-order magnetic field gradient parameters can be obtained, thereby enabling accurate measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic field gradient measurement, and particularly relates to a full-tensor high-order magnetic field gradient sensing system and a use method. BACKGROUND

[0002] The magnetic gradient tensor is the rate of change of three components of a magnetic field along three directions in space. Compared with single-component magnetic field and total magnetic field, the magnetic gradient tensor technology can extract more abundant attitude information and magnetic source information about a target object, has higher spatial resolution, and has strong anti-interference ability, is not easily affected by environmental magnetic interference and geomagnetic diurnal variation, has strong adaptability to complex environments, has good properties that are less affected by the magnetization direction of the target object, and improves the positioning accuracy of the target object, which is more conducive to the positioning and tracking of magnetic targets. After obtaining the magnetic field gradient tensor, more abundant magnetic field information such as tensor invariants, eigenvalues and modulus, and many rotation invariants can be obtained. After further processing, more abundant, 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. Using magnetic gradient tensor data can realize airborne magnetic exploration, mineral exploration and soil black metal search, unexploded bomb exploration, mine clearance, submarine detection or underwater metal target positioning and inversion identification, underwater / underground explosive detection, underwater magnetic object detection, intrusion object detection, indoor positioning, in-vivo micro-diagnosis and treatment device positioning, metal defect, corrosion, stress and other damage detection, and other civil and military fields, and has very broad application prospects.

[0003] In an actual magnetic field gradient measurement system, a target magnetic field is generally measured by a plurality of three-axis magnetic sensors, so as to indirectly obtain a magnetic field gradient. In order to adapt to different application scenarios, various magnetic field gradient sensing systems with different structures and combinations have also appeared. The first-order magnetic gradient tensor is the most commonly used measurement object in practical applications, and the first-order magnetic gradient tensor has a total of 9 parameters, of which 5 are independent parameters. Correspondingly, many scholars have developed the measurement structure, principle and algorithm of the first-order magnetic field gradient tensor, and the first-order magnetic field gradient tensor has been applied in different fields. For example, the cross-shaped array and the hexahedral array have large errors when encountering strong noise, and the first-order magnetic field gradient tensor needs to be combined with the magnetic induction intensity when used in positioning applications, which inevitably affects the environmental magnetic field such as the geomagnetic field, making it difficult to realize the detection and positioning of magnetic targets. The second-order magnetic gradient tensor also has important applications in positioning, and the second-order magnetic gradient tensor has a total of 27 parameters, of which 9 are independent parameters. However, the second-order magnetic field gradient measurement method in the existing public literature only gives part of the parameters of the second-order magnetic gradient tensor, such as the plane forming a rhombic arrangement, which can only obtain part of the parameters of the second-order magnetic gradient tensor, resulting in limited application occasions. In addition, at present, a large number of scholars only give the composition schematic diagram of the three-axis magnetic sensor in the magnetic field gradient sensing system, and do not give the specific structure and assembly method, and there is a large distance in specific practical applications.

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

[0005] (1) Most of the existing magnetic field gradient sensing systems are first-order magnetic field gradient sensing systems, which can only measure first-order magnetic field gradient parameters and cannot measure 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 and cannot measure the complete first-order magnetic field gradient parameters, which is only a partial tensor first-order magnetic field gradient sensing system and 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, but the magnetic induction intensity parameter has the problem of environmental interference magnetic field such as earth background magnetic field, which is difficult to eliminate, so the error is large during positioning;

[0009] (5) The existing magnetic field gradient sensing system needs to use GPS and other auxiliary means for self-positioning and cannot self-position through its own magnetic field gradient sensing system. SUMMARY

[0010] In view of the fact that most of the existing magnetic field gradient sensing systems are for first-order magnetic field gradient and cannot obtain all first-order and second-order magnetic field gradient parameters, and no specific construction method is given, a full tensor high-order magnetic field gradient sensing system and a use method are proposed.

[0011] In order to achieve the above purpose, the present application is realized by the following technical scheme: 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 communication module, the pure wood support frame is used to support 15 three-axis magnetic field sensors and a magnetic field acquisition processing communication module, in the coordinate system oxyz, the pure wood support frame has 9 mounting nodes A, B, C, D, O, E, F, G and H distributed in the shape of a field in the xy plane, and has 6 mounting nodes I, J, K, L, M and N distributed in two rows in the xz plane, and the two rows of mounting nodes are located above and below the xy plane, 15 three-axis magnetic field sensors are located on 15 mounting nodes, and 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;

[0013] A non-metallic directional support, 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 always keeps plumb downward;

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

[0015] A communication antenna, which is covered on the high-strength engineering plastic shell, is used for receiving the magnetic field data transmitted by the magnetic field acquisition processing communication module and transmitting the magnetic field data to a remote data system.

[0016] Further, the pure wood support frame includes a plurality of wood poles, and the plurality of wood poles are connected to each other to form 15 mounting nodes, and 15 three-axis magnetic field sensors are respectively mounted on the 15 mounting nodes, and the distance between adjacent two mounting nodes located on the same wood pole is equal.

[0017] Further, the plurality of wood poles are connected to each other through mortise and tenon joints.

[0018] Further, the non-metallic directional support includes three wooden hollow spherical balls, and the three wooden hollow spherical balls are sequentially connected from inside to outside through ceramic bearings and cylindrical wooden tenons which can freely rotate, the pure wood support frame is mounted on the innermost wooden hollow spherical ball, the outermost wooden hollow spherical ball is rotatably connected with the inner wall of the high-strength engineering plastic shell through the ceramic bearings and the cylindrical wooden tenons, and is arranged concentrically with the high-strength engineering plastic shell.

[0019] Further, the three wooden hollow spherical 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 spherical wooden hollow spherical ball, and the diameter of the first circular wooden ring is the same as that of the wooden hollow spherical ball; the diameters of the four second circular wooden rings are smaller than that of the first circular wooden ring.

[0020] Among them, the first circular wooden ring of the outermost and middle layer of the wooden hollow spherical ball is provided with a ceramic bearing and a cylindrical wooden tenon at four positions uniformly spaced at an angle of 90 degrees, and the outermost wooden hollow spherical ball is rotatably connected with the high-strength engineering plastic shell through the ceramic bearings and cylindrical wooden tenons arranged at two positions spaced at an angle of 180 degrees, and the ceramic bearings and cylindrical wooden tenons arranged at other two positions of the outermost wooden hollow spherical ball spaced at an angle of 180 degrees are rotatably connected with the ceramic bearings and cylindrical wooden tenons arranged at two positions of the middle layer of the wooden hollow spherical ball spaced at an angle of 180 degrees.

[0021] The first circular wood ring of the innermost wood hollow spherical ball is provided with a ceramic bearing and a cylindrical wood tenon at two positions spaced 180 degrees apart, and the innermost wood hollow spherical ball is rotatably connected with another two ceramic bearings and cylindrical wood tenons provided at positions spaced 180 degrees apart on the wood hollow spherical ball of the middle layer.

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

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

[0024] Further, a plurality of solar cells are provided, the plurality of solar cells are spliced into a grid shape and cover the high-strength engineering plastic shell, and the metal mesh formed by the communication antenna covers the spliced grid of the solar cells.

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

[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] A complete first-order magnetic field gradient is calculated from the magnetic induction intensity measured by the three-axis magnetic field sensor.

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

[0029] A three-dimensional position vector of the magnetic field sensing probe to the underwater submarine is calculated from the first-order magnetic field gradient and the second-order magnetic field gradient.

[0030] The longitude, latitude and other geographical parameters of the position of the magnetic field sensing probe are given.

[0031] The angle between the coordinate system of the magnetic field sensing probe and the geographic true north is given.

[0032] The three-dimensional position of the underwater submarine is given.

[0033] The position of the sea where the full-tensor high-order magnetic field gradient sensing system is located, the angle between the coordinate system of the magnetic field sensing probe and the geographic true north, and the three-dimensional position of the underwater submarine are sent to a remote data system.

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

[0035] The magnetic induction intensity B is composed of three scalars B x , B y and B z , the first-order magnetic field gradient G is a 3-by-3 matrix including 9 parameters, and can be expressed as three vectors, i.e., G x , G y and G z , each of which contains three scalars; the second-order magnetic field gradient H is three matrices, i.e., H x , H y and H z , each of which contains 9 scalars.

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

[0037]

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

[0039]

[0040] The gradient of the magnetic induction intensity B along the z direction is B xz , B yz and B zz , i.e., 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, the trace thereof trace G = B xx +B yy +B zz =0, so among the 9 elements of the magnetic field gradient tensor, only 5 elements are independent, i.e., B xx , B xy , B xz , B yy, B yz ;

[0043] The magnetic field gradient is calculated by the way of the differential of the magnetic induction intensity measured by the triaxial magnetic field sensor in two positions, and then multiple magnetic field gradients are averaged;

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

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

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

[0047] The magnetic field gradient G x can be calculated by the magnetic induction intensity measured by the triaxial magnetic field sensors at A and C points, D and E points, F and H points, L and N points, and I and K points.

[0048]

[0049] The magnetic field gradient G y can be calculated by the magnetic induction intensity measured by the triaxial magnetic field sensors at A and F points, B and G points, and C and H points.

[0050]

[0051] The magnetic field gradient G z can be calculated by the magnetic induction intensity measured by the triaxial magnetic field sensors at I and L points, J and M points, and K and N points.

[0052]

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

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

[0055]

[0056] In the formula, the main diagonal elements satisfy H xxx +H yyx +H zzx =0, the matrix H x is a symmetric matrix, and there are 9 parameters in the matrix H x , but only 5 independent parameters, i.e., H xxx , H xyx , H xzx , H yyx and H yzx ;

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

[0058]

[0059] In the formula, the main diagonal elements satisfy H xxy +H yyy +H zzy =0, the matrix H y is a symmetric matrix, and there are 9 parameters in the matrix H y , but only 5 independent parameters, i.e., H xxy , Hxyy H xzy H yyy and H yzy ;

[0060] The gradient of the first-order magnetic field gradient G along the z-direction, i.e., G x G y and G z The gradient along the z-direction is 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 in the formula satisfy H xxz +H yyz +H zzz =0, H z The matrix is ​​a symmetric matrix, H z The matrix has a total of 9 parameters, but only 5 of them are independent, namely H. xxz H xyz H xzz H yyz and H yzz ;

[0063] Based on the spatial arrangement of the triaxial magnetic sensor and the definition of the second-order magnetic field gradient tensor, the second-order magnetic field gradient tensor at the origin o of the coordinate system are respectively:

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

[0065] Where Q is the center of the line connecting E and O, and P is the center of the line connecting O and D, then the first-order magnetic field gradient G passes through points Q and P. 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 Calculate the magnetic field gradient G respectively x Gy and G z The magnetic field gradient along the x direction, i.e. the second-order magnetic field gradient H x , is calculated as follows:

[0066]

[0067] The first-order magnetic field gradient G x at points S and R is calculated from the magnetic induction measured by the three-axis magnetic field sensors at points G and O, and O and B respectively. y The first-order magnetic field gradient G z at points E and D is calculated from the magnetic induction measured by the three-axis magnetic field sensors at points K and N, and L and I respectively.

[0068] where R is the center of the line connecting points O and B, and S is the center of the line connecting points G and O. The second-order magnetic field gradient G x at points G and B, and the first-order magnetic field gradient G y at points S and R are used to calculate the magnetic field gradient G x and G y along the y direction, respectively. z The third parameter H xzy in the third parameter H yzy in the third parameter H zzy in the third parameter H x in the third parameter H xxy in the third parameter H yxy in the third parameter H zxy in the third parameter H zxy in the third parameter H y in the third parameter H xyy in the third parameter H yyy in the third parameter H zyy in the third parameter H zyy in the second parameter H z in the second parameter H xzz in the second parameter H yzz in the second parameter H zzz in the second parameter H yzz are the same, and are denoted by an asterisk. The magnetic field gradient G x , G y and G z along the y direction, i.e. the second-order magnetic field gradient H y , is calculated as follows:

[0069]

[0070] where the asterisk indicates that the parameter in this vector is the same as H x , Hy H z The other parameters in the calculation 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 using the magnetic induction intensity measured by triaxial magnetic field sensors at points N and L, and K and I, respectively. x The first-order magnetic field gradient G at points T and W is calculated using the magnetic induction intensity measured by triaxial magnetic field sensors at points M and O, and O and J, respectively. z ;

[0073] Then through 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 Calculate the magnetic field gradient G respectively x and G z Magnetic field gradient along the z-direction; G y Magnetic field gradient H along the z-direction xyz H yyz H zyz ) respectively with G z Magnetic field gradient along the x-direction (H) xzx H yzx H zzx The second parameter H in ) yzx G y Magnetic field gradient along the y-direction (H) xyy H yyy H zyy The third parameter H in ) zyy G z Magnetic field gradient along the z-direction (H) xzz H yzz H zzz The second parameter H in ) yzz The same is represented by **. Magnetic field gradient G x G y and G z The magnetic field gradient along the z-direction, i.e., the second-order magnetic field gradient H z The calculation is as follows:

[0074]

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

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

[0077] Through the first-order magnetic field gradient G x and the second-order magnetic field gradient H x in the x direction, the three-dimensional position vector of the underwater submarine is obtained:

[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] Through the first-order magnetic field gradient G y and the second-order magnetic field gradient H y in the y direction, the three-dimensional position vector of the underwater submarine is obtained:

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

[0082] Through the first-order magnetic field gradient G z and the second-order magnetic field gradient H z in the z direction, the three-dimensional position vector of the underwater submarine is obtained:

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

[0084] The three-dimensional position vectors of the underwater submarine obtained through the first-order and second-order magnetic field gradients in the x, y, and z directions are averaged to obtain

[0085]

[0086] The specific method for giving the longitude, latitude, and other geographic parameters of the position of the magnetic field sensor probe is as follows:

[0087] Through the magnetic induction intensity B xO , B yO , and B zO of point O, the magnetic declination longitude λ, latitude Ψ, and three geographic parameters are given by comparing with the built-in geomagnetic map.

[0088] Among them, B zO is the magnetic induction intensity in the plumb direction, B xO and B yOThe magnetic induction intensity in the horizontal direction, the magnetic declination angle is positive when north is east, and negative when north is west; wherein, the geographic north is the direction of the meridian towards the north pole. The geomagnetic north is the north of the earth's magnetic pole, i.e. the north direction indicated by the compass. The declination angle between the geomagnetic north and the geographic north is the magnetic declination angle.

[0089] The specific method for giving the angle between the coordinate system of the magnetic field sensing probe and the geographic north is as follows:

[0090] According to the latitude and longitude, the magnetic induction intensity is recalculated, and compared with the actually measured magnetic induction intensity, the angle between the x-axis of the coordinate system of the magnetic field sensing probe and the geographic north is given;

[0091] The International Reference Geomagnetic Field (IGRF) is a standard global model for describing 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 harmonics functions:

[0092]

[0093] In the formula, r is the geocentric distance of any point, λ is the longitude, θ is the complementary latitude, θ = 90-Ψ, and Ψ is the latitude, is the Schmidt quasi-normalized associated Legendre function, is the spherical harmonic coefficient of the internal source field magnetic potential;

[0094] The geomagnetic coordinate system OXYZ is defined, wherein 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 rule is satisfied. In the geomagnetic coordinate system OXYZ, the derivative along the axis 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] In the formula, R is the international reference sphere radius, i.e. the average radius of the earth (R = 6371.2 km), is the n-order m-time Gaussian spherical harmonic coefficient, the value is taken according to the 11th generation IGRF, and N is the truncation order, N = 10;

[0097] The specific values of the parameters in the formula (18) to the formula (21), such as r, m, n, The values of the parameters are shown in many published documents, which are not described herein.

[0098] Such as C.C.Finlay, S.Maus, C.D.Beggan, T.N.Bondar, 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 of the coordinate system of the magnetic field sensing probe and the geomagnetic north direction is

[0100]

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

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

[0103] The full-tensor high-order magnetic field gradient sensing system is located at latitude Ψ and longitude λ, and at this position, in the coordinate system of the magnetic field sensing probe, the angle between the x-axis and the geographic north direction is north by east The angle, the z-axis is plumb downward, and the y-axis conforms to the right-hand rule.

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

[0105] 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 direction, and the three-dimensional position vector of the underwater submarine are transmitted to a remote data system by a remote communication mode.

[0106] The beneficial effects of the present application are:

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

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

[0109] 2. The magnetic induction intensity of the underwater submarine is obtained by the three-axis magnetic field sensor in the magnetic field sensor probe, the 9 parameters of the first-order magnetic field gradient and the 27 parameters of the second-order magnetic field gradient can be calculated, the three-dimensional position of the underwater submarine is obtained by the first-order magnetic field gradient and the second-order magnetic field gradient, the longitude, the latitude, 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 pure wood support frame and the non-metal directional support in the sensing system eliminate electromagnetic interference, and the full-tensor high-order magnetic field gradient sensing system can obtain the position of the underwater submarine and the three-dimensional position of the underwater submarine without the aid of GPS and other auxiliary positioning means. BRIEF DESCRIPTION OF DRAWINGS

[0111] In order to more clearly illustrate the specific embodiments of the present application, the drawings required in the specific embodiments will be briefly introduced below. In all the drawings, the elements or parts are 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 according to an embodiment of the present application is shown in the figure.

[0113] Figure 2 A data transmission schematic diagram of a full-tensor high-order magnetic field gradient sensing system according to an embodiment of the present application is shown in the figure. Figure 1

[0114] Figure 3 A node arrangement diagram of a magnetic field sensor probe in a full-tensor high-order magnetic field gradient sensing system according to an embodiment of the present application is shown in the figure. Figure 1

[0115] Figure 4 A schematic diagram of a pure wood support frame in a full-tensor high-order magnetic field gradient sensing system according to an embodiment of the present application is shown in the figure. Figure 1

[0116] A schematic diagram of a pure wood support frame in a full-tensor high-order magnetic field gradient sensing system according to an embodiment of the present application is shown in the figure. Figure 5 Figure 1 A schematic diagram of a pure wood support frame in a full-tensor high-order magnetic field gradient sensing system according to an embodiment of the present application is shown in the figure.

[0117] Figure 6 Figure 1 A connection and installation sequence of a wood pole of a pure wood support frame in a full-tensor high-order magnetic field gradient sensing system according to an embodiment of the present application is shown in the figure.

[0118] Figure 7 A connection and installation sequence of a wood pole of a pure wood support frame in a full-tensor high-order magnetic field gradient sensing system according to an embodiment of the present application is shown in the figure. Figure 1 ​​​​An installation mode schematic diagram of a three-axis sensor in a full tensor high-order magnetic field gradient sensing system shown in the figure;

[0119] Figure 8 For Figure 1 An outermost layer of a wooden hollow spherical ball of a non-metallic directional support in a full tensor high-order magnetic field gradient sensing system shown in the figure;

[0120] Figure 9 For Figure 1 An intermediate layer of a wooden hollow spherical ball of a non-metallic directional support in a full tensor high-order magnetic field gradient sensing system shown in the figure;

[0121] Figure 10 For Figure 1 An innermost layer of a wooden hollow spherical ball of a non-metallic directional support in a full tensor high-order magnetic field gradient sensing system shown in the figure;

[0122] Reference signs:

[0123] 100, magnetic field sensing probe; 110, three-axis magnetic field sensor; 120, wooden rod; 130, wooden key; 200, non-metallic directional support; 210, hollow ceramic bearing; 300, high-strength engineering plastic shell. DETAILED DESCRIPTION

[0124] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0125] Please refer to Figures 1 to 10 The present application provides a full tensor high-order magnetic field gradient sensing system and a use method, comprising a magnetic field sensing probe 100, a non-metallic directional support 200, a high-strength engineering plastic shell 300 and a communication antenna.

[0126] Specifically, the magnetic field sensing probe 100 comprises a pure wood support frame, 15 three-axis magnetic field sensors 110 and a magnetic field acquisition processing 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 communication module, in the coordinate system oxyz, the pure wood support frame has 9 installation nodes A, B, C, D, O, E, F, G and H distributed in the shape of a field in the xy plane, and has 6 installation nodes I, J, K, L, M and N distributed in two rows in the xz plane, and the two rows of installation nodes are opposite to each other and located above and below the xy plane, and 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 for acquiring, processing and transmitting the magnetic field data of the 15 three-axis magnetic field sensors 110. In specific use, the magnetic field acquisition processing communication module integrates the magnetic field signal acquisition, data processing and communication, and is integrated in 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, the longitude and latitude where the full-tensor high-order magnetic field gradient sensing system is located and the azimuth of the coordinate system of the system and the geographic true north are calculated, the three-dimensional position of the underwater submarine is calculated, and then the longitude and latitude where the full-tensor high-order magnetic field gradient sensing system is located, the angle between the coordinate system of the system and the geographic true 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, which are connected to each other to form 15 mounting nodes, and the 15 three-axis magnetic field sensors 110 are respectively mounted on the 15 mounting nodes. The distance between adjacent mounting nodes located on the same wood pole 120 is equal. In specific implementation, the pure wood support frame can be formed by splicing a T-shaped frame and an I-shaped frame, and then splicing the T-shaped frame and the I-shaped frame. The wood poles 120 are all connected by mortise and tenon joints, and do not use any metal materials such as metal nails or bolts.

[0129] The specific mode can be:

[0130] In the coordinate system oxyz of the magnetic field sensing probe, the coordinate 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 T-shaped frame is located in the xy plane, and the I-shaped frame is located in the xz plane.

[0131] The H-shaped frame is composed of 3 original wooden bars, including 6 nodes, I, J, K, L, M and N, which are all in a plane. The 3 original wooden bars are IK wooden bar, LN wooden bar and JM wooden bar. The 0.5 times length (i.e. the middle part of the length of the wooden bar) of the IK wooden bar is the J node, the 0.5 times length (i.e. the middle part of the length of the wooden bar) of the LN wooden bar is the J node M, and the 0.5 times length (i.e. the middle part of the length of the wooden bar) of the JM wooden bar is the O node. In addition, the IK wooden bar is parallel to the LN wooden bar, and the IK wooden bar and the LN wooden bar are both perpendicular to the JM wooden bar. Among the 6 nodes, there are 4 end nodes, I, K, L and N; and 2 T-shaped nodes, J and M. One three-axis magnetic field sensor 110 is arranged at each node, and a total of 6 three-axis magnetic field sensors 110 are arranged.

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

[0133] The H-shaped frame is composed of 3 original wooden bars, including 6 nodes, I, J, K, L, M and N, which are all in a plane. The 3 original wooden bars are IK wooden bar, LN wooden bar and JM wooden bar. The 0.5 times length (i.e. the middle part of the length of the wooden bar) of the IK wooden bar is the J node, the 0.5 times length (i.e. the middle part of the length of the wooden bar) of the LN wooden bar is the J node M, and the 0.5 times length (i.e. the middle part of the length of the wooden bar) of the JM wooden bar is the O node. In addition, the IK wooden bar is parallel to the LN wooden bar, and the IK wooden bar and the LN wooden bar are both perpendicular to the JM wooden bar. Among the 6 nodes, there are 4 end nodes, I, K, L and N; and 2 T-shaped nodes, J and M. One three-axis magnetic field sensor 110 is arranged at each node, and a total of 6 three-axis magnetic field sensors 110 are arranged.

[0134] In the plane containing the grid-shaped frame, node O is a cross node, meaning BG and DE are perpendicularly connected at point O. Furthermore, since the grid-shaped and I-shaped frames are connected at point O, three wooden poles—BG, DE, and JM—are also connected at point O. Therefore, node O is a double cross node in three-dimensional space, referred to as the cross node throughout 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 on the same wooden pole is equal, and the 15 triaxial magnetic field sensors are located on 15 mounting nodes, meaning the distance between two adjacent triaxial magnetic field sensors on the same wooden pole is equal, denoted by d.

[0135] Of the 15 nodes, there are 4 end nodes, 4 right-angle nodes, 6 T-shaped nodes, and 1 cross node. An end node is the end of a single wooden pole; a right-angle node is formed by connecting two wooden poles at their ends; a T-shaped node is formed by connecting the end of one wooden pole at 0.5 times its length (the middle of its length) to the end of another wooden pole; and a cross node is formed by connecting three wooden poles at 0.5 times their length (the middle of their lengths).

[0136] When connecting two or more wooden poles, mortise and tenon joints are used, and no metal nails or bolts or any other metal materials are used.

[0137] It should be noted that in the specific implementation, the single triaxial magnetic field sensor 110 is a low-power ultra-small size. After being protected by ultra-thin engineering plastic encapsulation, the dimensions in all three directions are in the millimeter level (less than 10 mm). Since the single triaxial magnetic field sensor 110 is ultra-small, holes are directly drilled on the wooden rod of the sensing probe, and then it is fixed with thin wooden wedges 130.

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

[0139] In practical use, when the entire device rotates, rolls, or moves, the plane containing the grid-shaped frame remains horizontal but rotates. MJ always maintains a downward vertical direction, so the z-axis always points downward vertically, while the x-axis and y-axis rotate together at the same angle and in the same direction. That is, the coordinate system oxyz of the magnetic field sensing probe is a dynamic coordinate system where the z-axis direction remains unchanged, while the x-axis and y-axis directions change.

[0140] Specifically, the non-metal directional support includes three wooden hollow spherical balls, the three wooden hollow spherical balls are sequentially connected by ceramic bearings and cylindrical wooden dowels from inside to outside, the pure wooden support frame is installed on the innermost wooden hollow spherical ball, the outermost wooden hollow spherical ball is rotatably connected with the inner wall of the high-strength engineering plastic shell by ceramic bearings and cylindrical wooden dowels, and is arranged concentrically with the high-strength engineering plastic shell.

[0141] Specifically, the three wooden hollow spherical 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 the spherical wooden hollow spherical ball, the first circular wooden ring has the same diameter as the wooden hollow spherical ball; the four second circular wooden rings have smaller diameters than the first circular wooden ring;

[0142] The first circular wooden ring of the outermost and middle wooden hollow spherical balls is provided with a ceramic bearing and a cylindrical wooden dowel at four positions uniformly spaced by 90 degrees, the outermost wooden hollow spherical ball is rotatably connected with the high-strength engineering plastic shell through the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced by 180 degrees, and the ceramic bearings and cylindrical wooden dowels arranged at other two positions spaced by 180 degrees on the outer wooden hollow spherical ball are rotatably connected with the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced by 180 degrees on the middle wooden hollow spherical ball;

[0143] The first circular wooden ring of the outermost and middle wooden hollow spherical balls is provided with a ceramic bearing and a cylindrical wooden dowel at four positions uniformly spaced by 90 degrees, the outermost wooden hollow spherical ball is rotatably connected with the high-strength engineering plastic shell through the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced by 180 degrees, and the ceramic bearings and cylindrical wooden dowels arranged at other two positions spaced by 180 degrees on the outer wooden hollow spherical ball are rotatably connected with the ceramic bearings and cylindrical wooden dowels arranged at two positions spaced by 180 degrees on the middle wooden hollow spherical ball;

[0144] In this way, the connection of the inner and outer wooden hollow spherical balls can be facilitated, and the function of free rotation can be well realized.

[0145] In specific implementation, the following method can be used for manufacturing:

[0146] Three wooden spherical balls are used for construction, the three wooden spherical balls are all internally hollow and have a common spherical center, the outermost wooden spherical ball, the middle wooden spherical ball and the innermost wooden spherical ball, wherein the spherical surface diameter of the outermost wooden spherical ball is d max , the thickness of the spherical surface of the outermost wooden spherical ball is d ma , the spherical surface diameter of the middle wooden spherical ball is d mid , the thickness of the spherical surface of the middle wooden spherical ball is d mi , and the spherical surface diameter of the innermost wooden spherical ball is dmin The thickness of the innermost wooden spherical surface is d mn The distance from the middle of the wooden thickness of the sphere to the center of the sphere is d. The clearance between the outermost wooden sphere and the middle wooden sphere is d1, and the clearance between the middle wooden sphere and the innermost wooden sphere is d2. The two clearances can satisfy that the three wooden spheres do not touch each other during rotation. The size of the three wooden spheres needs to meet 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 composed of one large circular wooden ring and four small circular wooden rings, and the five circular wooden rings are located on a spherical surface with a diameter of d max , wherein the diameter of the large circular wooden ring is the same as the diameter d max of the spherical surface. Four cylindrical through holes are formed in the large circular wooden ring of the outermost wooden sphere, which are W1, W2, Z1 and Z2, and the four cylindrical through holes are uniformly distributed on the large circular wooden ring with an interval of 90 degrees. Hollow ceramic bearings 210 are installed on the four cylindrical through holes, and cylindrical wooden dowels are fixed in the inner holes of the ceramic bearings 210. The cylindrical wooden dowels in the inner holes of the ceramic bearings 210 at W1 and W2 are fixed on the inner wall of the high-strength engineering plastic shell 300.

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

[0151] The middle wooden sphere is composed of one large circular wooden ring and four small circular wooden rings, and the five circular wooden rings are located on a spherical surface with a diameter of d mid , wherein the diameter of the large circular wooden ring is the same as the diameter d mid of the spherical surface. Four cylindrical through holes are formed in the large circular wooden ring of the middle wooden sphere, which are N3, N4, Z3 and Z4, and the four cylindrical through holes are uniformly distributed on the large circular wooden ring with an interval of 90 degrees. Hollow ceramic bearings 210 are installed on the four cylindrical through holes, and cylindrical wooden dowels are fixed in the inner holes of the ceramic bearings 210.

[0152] The cylindrical wooden dowel in the inner hole of the ceramic bearing 210 at N3 and N4 on the large circular wooden ring of the middle wooden sphere is fixed on the ceramic bearing 210 at N1 and N2 on the large circular wooden ring of the innermost wooden sphere.

[0153] The innermost wooden sphere is spliced by one large circular wooden ring and four small circular wooden rings, and the five circular wooden rings are located on a spherical surface with a diameter of d min , wherein the diameter of the large circular wooden ring is the same as the diameter d min of the spherical surface. On the large circular wooden ring of the innermost wooden sphere, two cylindrical through holes are opened, which are N1 and N2, and the two cylindrical through holes are uniformly distributed on the large circular wooden ring with an interval of 180 degrees. Hollow ceramic bearings 210 are installed on the two cylindrical through holes N1 and N2, and a cylindrical wooden dowel is fixed in the inner hole of the ceramic bearing 210. In the innermost wooden sphere, the large circular wooden ring and the two small circular wooden rings in the plumb direction have four connection points, wherein the two bottom connection points are nodes 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 eight connection points, wherein the four bottom connection points are nodes 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 sensing probe 100, and the nodes L, N, A, C, F and H of the pure wooden support frame of the magnetic field sensing probe 100 are fixed at the nodes L0, N0, A0, C0, F0 and H0 of the innermost wooden sphere, respectively.

[0154] The three wooden spheres are made of hard wenge (green sandalwood). The parameters of wenge (green sandalwood) need to meet the following requirements: the density of wenge (green sandalwood) > 1000 kg / m3, Janka hardness > 16000 N, compressive strength > 70 MPa, fracture modulus > 170 MPa, and elastic modulus > 15 GPa. The shrinkage rates of the raw wood in the radial and tangential directions are both less than 8%, and the volume shrinkage rate is < 15%.

[0155] Due to the properties of the non-metallic directional support, when the entire device rotates, rolls or moves, the plane where the cross-shaped frame is located will remain horizontal but will rotate, MJ will always remain in the direction of the plumb downward, the z-axis will always be in the direction of the plumb downward, and the x-axis and y-axis will rotate together in the same angle and 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 does not change, and the directions of the x-axis and y-axis change.

[0156] The high-strength engineering plastic shell 300 is wrapped outside the non-metallic directional support, and the high-strength engineering plastic shell 300 has a spherical outer surface. The spherical shell facilitates the use of the entire sensor on the water surface or uneven ground, and the spherical shell can automatically adapt to the external environment.

[0157] A communication antenna, covering the outer casing, is used to receive magnetic field data transmitted from the magnetic field acquisition and processing communication module and output it to the remote data transmission system. Specifically, the communication antenna is a metal mesh wrapped around the outer casing, which can be adapted to the shape of a spherical, high-strength engineering plastic casing. Of course, in other embodiments, the communication antenna can take other forms. In a specific implementation, galvanized copper wire and galvanized molybdenum wire can be interwoven into a twisted pair, and then the twisted pair can be woven into a metal mesh, which serves as the communication antenna.

[0158] In a preferred embodiment, the sensing system further includes multiple solar cells, which are spliced ​​together in a grid pattern and cover a high-strength engineering plastic shell. A metal mesh formed by the communication antenna covers the grid-like splicing points of the solar cells. The solar cells can power other components.

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

[0160] S110. Place the full tensor high-order magnetic field gradient sensing system on the surface of the ocean, in a floating state, to measure the position of an underwater submarine.

[0161] Specifically, because the full-tensor high-order magnetic field gradient sensing system is made of materials such as wood and plastic, its overall density is much less than that of water, allowing it to float on the ocean surface. When locating underwater submarines, the full-tensor high-order magnetic field gradient sensing system can be placed directly on the ocean surface, where it will float. For single-point measurements, the system can be placed at the target location. For measurements in the ocean, the system can be placed in the water, allowing it to float. When locating surface / underwater targets such as ships, several full-tensor high-order magnetic field gradient sensing systems can be thrown and floated on the ocean surface. For locating deep underground explosives such as bombs and landmines, the system can be placed at a safe distance from the target location.

[0162] S120. The complete first-order magnetic field gradient is calculated from the magnetic induction intensity measured by the triaxial magnetic field sensor.

[0163] The specific operating method is as follows:

[0164] Define the magnetic field strength B, which includes three scalars B. x B y and B z The first-order magnetic field gradient G is a 3x3 matrix containing 9 parameters, which can be represented as 3 vectors, namely G0. x G y and G zEach vector contains 3 scalars. The second order magnetic field gradient H is a 3x3 matrix, i.e. H x , H y and H z . Each matrix contains 9 scalars.

[0165] The gradient of the magnetic induction B in the x direction is B xx , B yx and B zx , i.e. the magnetic field gradient G x

[0166]

[0167] The gradient of the magnetic induction B in the y direction is B xy , B yy and B zy , i.e. the magnetic field gradient G y

[0168]

[0169] The gradient of the magnetic induction B in the z direction is B xz , B yz and B zz , i.e. 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 trace G = B xx + B yy + B zz = 0, so of the 9 elements of the magnetic field gradient tensor, only 5 are independent, i.e. B xx , B xy , Bxz, B yy , B yz .

[0172] The magnetic field gradient is calculated from the way the magnetic induction differential is measured by two position three-axis magnetic field sensors, and then multiple magnetic field gradients are averaged.

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

[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, and j can be B, D, E, G, M, J, P, Q, R, S, T, or W.

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

[0176] The magnetic induction intensity measured by the three-axis magnetic field sensors at points A and C, points D and E, points F and H, points L and N, and points I and K can be used to calculate the magnetic field gradient G x .

[0177]

[0178] The magnetic induction intensity measured by the three-axis magnetic field sensors at points A and F, points B and G, and points C and H can be used to calculate the magnetic field gradient G y .

[0179]

[0180] The magnetic induction intensity measured by the three-axis magnetic field sensors at points I and L, points J and M, and points K and N can be used to calculate the magnetic field gradient G z .

[0181]

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

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

[0184]

[0185] where 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, i.e. H xxx , H xyx , H xzx , H yyx and H yzx .

[0186] The gradient of the first order magnetic field gradient G along the y direction, i.e. G x , G y and G z along the y direction, are expressed as H xxy , H yxy , H zxy , H xyy , H yyy , H zyy , H xzy , H yzy , H zzy , i.e. the second order magnetic field gradient H y :

[0187]

[0188] where 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, i.e. H xxy , H xyy , H xzy , H yyy and H yzy ;

[0189] The gradient of the first order magnetic field gradient G along the z direction, i.e. G x , G y and G z along the z direction, are expressed as H xyz , H yxz , H zxz , H xyzH 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 in the formula satisfy H xxz +H yyz +H zzz =0, H z The matrix is ​​a symmetric matrix, H z The matrix has a total of 9 parameters, but only 5 of them are independent, namely H. xxz H xyz H xzz H yyz and H yzz ;

[0192] Based on the spatial arrangement of the triaxial magnetic sensor and the definition of the second-order magnetic field gradient tensor, the second-order magnetic field gradient tensor at the origin O of the coordinate system are as follows:

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

[0194] Where Q is the center of the line connecting E and O, and P is the center of the line connecting O and D, then the first-order magnetic field gradient G passes through points Q and P. 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 Calculate the magnetic field gradient G respectively x G y and G z The magnetic field gradient along the x-direction, i.e., the second-order magnetic field gradient H. x The calculation is as follows:

[0195]

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

[0197] Where R is the center of the line connecting O and B, S is the center of the line connecting G and O, and the first-order magnetic field gradient G passes through points G and B. x The first-order magnetic field gradient G at points S and R y Calculate the magnetic field gradient G respectively x and G y Magnetic field gradient along the y-direction. G z Magnetic field gradient along the y-direction (H) xzy H yzy H zzy ) respectively with G x Magnetic field gradient along the y-direction (H) xxy H yxy H zxy The third parameter H in ) zxy G y Magnetic field gradient along the y-direction (H) xyy H yyy H zyy The third parameter H in ) zyy G z Magnetic field gradient along the z-direction (H) xzz H yzz H zzz The second parameter H in ) yzz Similar values ​​are indicated by *. Magnetic field gradient G x G y and G z The magnetic field gradient along the y-direction, i.e., the second-order magnetic field gradient H. y The calculation is as follows:

[0198]

[0199] In the formula, * indicates that the parameters in the vector are related to H. x H y H z The other parameters 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 using the magnetic induction intensity measured by triaxial magnetic field sensors at points N and L, and K and I, respectively. xThe first-order magnetic field gradient G at points T and W is calculated using the magnetic induction intensity measured by triaxial magnetic field sensors at points M and O, and O and J, respectively. z Then, through 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 Calculate the magnetic field gradient G respectively x and G z Magnetic field gradient along the z-direction; G y Magnetic field gradient along the z-direction (H) xyz H yyz H zyz ) respectively with G z Magnetic field gradient along the x-direction (H) xzx H yzx H zzx The second parameter H in ) yzx G y Magnetic field gradient along the y-direction (H) xyy H yyy H zyy The third parameter H in ) zyy G z Magnetic field gradient along the z-direction (H) xzz H yzz H zzz The second parameter H in ) yzz The same is represented by **. Magnetic field gradient G x G y and G z The magnetic field gradient along the z-direction, i.e., the second-order magnetic field gradient H z The calculation is as follows:

[0202]

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

[0204] S140. Calculate the three-dimensional position vector from the magnetic field sensing probe 100 to the underwater submarine using the first-order and second-order magnetic field gradients. The specific method is as follows:

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

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

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

[0208] Similarly, by solving the first-order magnetic field gradient G y and the second-order magnetic field gradient H y , the three-dimensional position vector of the underwater submarine is obtained:

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

[0210] Similarly, by solving the first-order magnetic field gradient G z and the second-order magnetic field gradient H z , the three-dimensional position vector of the underwater submarine is obtained:

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

[0212] The three-dimensional position vectors of the underwater submarine obtained by the first-order and second-order magnetic field gradients in the x, y and z directions are averaged to obtain

[0213]

[0214] S150, the longitude, latitude and other geographic parameters of the position of the magnetic field sensing probe 100 are given;

[0215] The specific method is:

[0216] The magnetic induction intensity B xO , B yO and B zO measured by the three-axis magnetic field sensor of point O, wherein B zO is the magnetic induction intensity in the plumb direction, B xO and B yO are the magnetic induction intensity in the horizontal direction, by comparing with the built-in geomagnetic map (the geomagnetic map can use the public national geomagnetic data, global geomagnetic data), the magnetic declination longitude λ, latitude Ψ and other three geographic parameters, wherein the magnetic declination is positive for north deviation east and negative for north deviation west.

[0217] The geographic true north is the direction of the meridian towards the north pole. The geomagnetic true north is the north of the earth's magnetic pole, that is, the north direction indicated by the compass. The declination between the geomagnetic true north and the geographic true north is the magnetic declination.

[0218] S160, the angle between the coordinate system of the magnetic field sensing probe 100 and the geographic true north is given. The specific method is:

[0219] According to the latitude and longitude, the magnetic induction intensity is recalculated, compared with the actually measured magnetic induction intensity, the azimuth is given, and the angle between the x-axis of the coordinate system of the magnetic field sensing probe and the geographic north is given; the International Reference Geomagnetic Field (IGRF) is a standard global model describing 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 harmonics:

[0220]

[0221] In the formula, r is the geocentric distance of any point, λ is the longitude, θ is the complementary latitude, θ = 90-Ψ, Ψ is the latitude, is the Schmidt quasi-normalized associated Legendre function, is the spherical harmonic coefficient of the internal source field magnetic potential.

[0222] The geomagnetic coordinate system OXYZ is defined, in which 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 rule is satisfied. In the geomagnetic coordinate system OXYZ, according to the longitude and latitude, the derivative along the axial direction is calculated according to the magnetic potential spherical harmonics, and the three components of the calculated geomagnetic field magnetic induction intensity are:

[0223]

[0224] In the formula, R is the international reference sphere radius, i.e. the average radius of the earth (R = 6371.2 km), is the n-order m-time Gaussian spherical harmonic coefficient, the value is taken according to the 11th generation IGRF, and N is the truncation order (N = 10 in this paper).

[0225] The specific values of the parameters in formula (18) to formula (21) are, for example, r, m, n, The values of the parameters are seen in many published documents, which are not described here.

[0226] For example, C.C.Finlay, S.Maus, C.D.Beggan, T.N.Bondar, 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 of the coordinate system of the magnetic field sensing probe and the geomagnetic north direction 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 the angle of north by east , the z-axis is plumb downward, and the y-axis complies with the right-hand rule.

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

[0231] The latitude Ψ and the longitude λ of the position where the full-tensor high-order magnetic field gradient sensing system is located, in the coordinate system of the magnetic field sensor probe at the position, the angle between the x-axis and the geographic north is the angle of north by east , the z-axis is plumb downward, and the y-axis complies with the right-hand rule, and in the coordinate system, the three-dimensional position vector of the underwater submarine is r.

[0232] S180, the position of the full-tensor high-order magnetic field gradient sensing 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 transmitted to a remote data system.

[0233] The specific method is:

[0234] The position of the full-tensor high-order magnetic field gradient sensing system in the sea and 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 transmitted to a remote data system by a remote communication method.

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

[0236] The specific advantages are:

[0237] The above full-tensor high-order magnetic field gradient sensing system and the use method, the sensing system includes a magnetic field sensor probe 100, a non-metallic directional support 200, and a high-strength engineering plastic shell 300, the solar cell of the high-strength engineering plastic shell 300 supplies power to the magnetic field acquisition and processing and communication module in the magnetic field sensor probe 100, the non-metallic directional support 200 makes the z-axis in the coordinate system of the magnetic field sensor probe 100 always plumb downward. The magnetic induction intensity of the underwater submarine is obtained by the three-axis magnetic field sensor 110 in the magnetic field sensor probe 100, and 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, the latitude of the position of the full-tensor high-order magnetic field gradient sensing system in the sea, and the angle between the coordinate system of the magnetic field sensor probe and the geographic north. The three-dimensional position of the underwater submarine is obtained by the first-order magnetic field gradient and the second-order magnetic field gradient. The longitude, the latitude of the position of the full-tensor high-order magnetic field gradient sensing 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 remote data receiving system by 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 processing communication module, the non-metallic directional support 200, the pure wood support frame of the magnetic field sensing 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 and metal screws, and completely eliminate electromagnetic interference. Without the aid of GPS and any other auxiliary positioning means, the full-tensor high-order magnetic field gradient sensing system can obtain its own position and the three-dimensional position of the target object such as the underwater submarine.

[0239] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and 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 application, and they should be covered in the scope of the claims and the specification of the present application.

Claims

1. A full-tensor high-order magnetic field gradient sensing system, characterized by, The pure wood support frame is used for supporting 15 three-axis magnetic field sensors and a magnetic field acquisition processing communication module. The pure wood support frame includes a plurality of wood bars. The plurality of wood bars are connected with each other to form 15 mounting nodes. The 15 three-axis magnetic field sensors are respectively arranged on the 15 mounting nodes. The distance between two adjacent mounting nodes on the same wood bar is equal. The plurality of wood bars are connected with each other through mortise and tenon joints.

2. The full-tensor high-order magnetic field gradient sensing system and method of using thereof according to claim 1, wherein, The non-metallic directional support frame includes three wooden hollow spherical balls.

3. The full-tensor high-order magnetic field gradient sensing system and method of using thereof according to claim 2, wherein, The three wooden hollow spherical balls are sequentially connected through ceramic bearings and cylindrical wooden tenons from inside to outside.

4. The full-tensor high-order magnetic field gradient sensing system of claim 1, wherein, The pure wood support frame is arranged on the innermost wooden hollow spherical ball.

5. The full-tensor high-order magnetic field gradient sensing system of claim 4, wherein, The outermost wooden hollow spherical ball is rotatably connected with the inner wall of the high-strength engineering plastic shell through ceramic bearings and cylindrical wooden tenons and is arranged concentrically with the high-strength engineering plastic shell. Each of the three wooden hollow spherical balls includes a first circular wooden ring and four second circular wooden rings. The first circular wooden ring has the same diameter as the wooden hollow spherical ball. The diameters of the four second circular wooden rings are smaller than that of the first circular wooden ring. The communication antenna is arranged on the high-strength engineering plastic shell. The communication antenna is used for receiving magnetic field data transmitted by the magnetic field acquisition processing communication module and transmitting the magnetic field data to a remote data system. The pure wood support frame includes a plurality of wood bars. The plurality of wood bars are connected with each other to form 15 mounting nodes. The 15 three-axis magnetic field sensors are respectively arranged on the 15 mounting nodes. The distance between two adjacent mounting nodes on the same wood bar is equal. The plurality of wood bars are connected with each other through mortise and tenon joints. The non-metallic directional support frame includes three wooden hollow spherical balls. The three wooden hollow spherical balls are sequentially connected through ceramic bearings and cylindrical wooden tenons from inside to outside. The pure wood support frame is arranged on the innermost wooden hollow spherical ball. The outermost wooden hollow spherical ball is rotatably connected with the inner wall of the high-strength engineering plastic shell through ceramic bearings and cylindrical wooden tenons and is arranged concentrically with the high-strength engineering plastic shell. Each of the three wooden hollow spherical balls includes a first circular wooden ring and four second circular wooden rings. The first circular wooden ring has the same diameter as the wooden hollow spherical ball. The diameters of the four second circular wooden rings are smaller than that of the first circular wooden ring. The communication antenna is arranged on the high-strength engineering plastic shell. The communication antenna is used for receiving magnetic field data transmitted by the magnetic field acquisition processing communication module and transmitting the magnetic field data to a remote data system. The four positions on the first circular wood ring of the wood hollow sphere of the outermost layer and the intermediate layer are evenly spaced by 90 degrees, and each position is provided with a ceramic bearing and a cylindrical wood tenon, and the wood hollow sphere of the outermost layer is rotatably connected with the high-strength engineering plastic shell through the ceramic bearings and cylindrical wood tenons provided at two positions spaced by 180 degrees, and the ceramic bearings and cylindrical wood tenons provided at other two positions spaced by 180 degrees on the wood hollow sphere of the outer layer are rotatably connected with the ceramic bearings and cylindrical wood tenons provided at two positions spaced by 180 degrees on the wood hollow sphere of the intermediate layer. The two positions on the first circular wood ring of the wood hollow sphere of the innermost layer are spaced by 180 degrees, and each position is provided with a ceramic bearing and a cylindrical wood tenon, and the wood hollow sphere of the innermost layer is rotatably connected with the ceramic bearings and cylindrical wood tenons provided at two positions spaced by 180 degrees on the wood hollow sphere of the intermediate layer.

6. The full-tensor high-order magnetic field gradient sensing system and method of using thereof according to claim 1, wherein, 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 using thereof according to claim 6, wherein, The metal mesh includes galvanized copper wires and galvanized molybdenum wires, the copper wires and the molybdenum wires are interwoven into twisted wires, and the twisted wires are woven into the metal mesh.

8. The full-tensor high-order magnetic field gradient sensing system and method of using thereof according to claim 7, wherein, A plurality of solar cells are further included, and the plurality of solar cells are spliced into a grid shape and covered on the high-strength engineering plastic shell, and the metal mesh formed by the communication antenna is covered on the spliced grid of the solar cells.

9. A method of using a full-tensor high-order magnetic field gradient sensing system, characterized by, The method for using the full-tensor high-order magnetic field gradient sensing system according to any one of claims 1-8 comprises: placing the full-tensor high-order magnetic field gradient sensing system on the sea surface in a floating state to measure the position of a submarine; calculating a complete first-order magnetic field gradient from the measured magnetic induction intensity of the three-axis magnetic field sensor; calculating a complete second-order magnetic field gradient from the measured magnetic induction intensity of the three-axis magnetic field sensor; calculating a three-dimensional position vector of the magnetic field sensing probe to the submarine from the first-order magnetic field gradient and the second-order magnetic field gradient; giving the longitude and latitude geographical parameters of the position of the magnetic field sensing probe; giving the angle between the coordinate system of the magnetic field sensing probe and the geographic north; giving the three-dimensional position of the submarine; sending the position of the full-tensor high-order magnetic field gradient sensing system on the sea, the angle between the coordinate system of the magnetic field sensing probe and the geographic north, and the three-dimensional position of the submarine to a remote data system.

10. The use method of the full-tensor high-order magnetic field gradient sensing system according to claim 9, wherein the specific method for calculating a complete first-order magnetic field gradient from the measured magnetic induction intensity of the three-axis magnetic field sensor is: calculating the magnetic field gradient by differentiating the measured magnetic induction intensity of the three-axis magnetic field sensor at two positions, and then averaging a plurality of magnetic field gradients; The magnetic induction B is set to comprise three scalars B x , B y and B z , the first magnetic field gradient G is in the form of a 3x3 matrix comprising nine parameters and can be represented by three vectors, namely G x , G y and G z , each of which comprises three scalars, and the second magnetic field gradient H is in the form of three matrices, namely H x , H y and H z , each of which comprises nine parameters The gradient of the magnetic induction B in the x-direction is B xx , B yx and B zx , i.e. the magnetic field gradient G x The gradient of the magnetic induction B in the y direction is B xy , B yy and B zy , i.e. the magnetic field gradient G y The gradient of the magnetic induction B in the z direction is B xz , B yz and B zz , i.e. 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, whose trace trace G = B xx +B yy +B zz = 0, so of the 9 elements of the magnetic field gradient tensor, only 5 are independent, namely B xx , B xy , B xz , B yy , B yz ; the distance between the three-axis magnetic field sensors on the two adjacent mounting nodes located on the same wood rod is d. ​ B i B is the magnetic induction intensity vector measured by the triaxial magnetic field sensor at point i, i can be A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, B xi , B yi , and B xz are three components of the magnetic induction intensity vector B i , respectively; G xj Gx is the first order magnetic field gradient in the x direction of the magnetic induction at point j, G yj Gy is the first order magnetic field gradient in the y direction of the magnetic induction at point j, G zj Gz is the first order magnetic field gradient in the z direction of the magnetic induction at point j, j can be B, D, E, G, M, J, P, Q, R, S, T, W; The magnetic induction intensity measured by the triaxial magnetic field sensor of A and C points, D and E points, F and H points, L and N points, and I and K points can all be used to calculate the magnetic field gradient G x To reduce the error, the average is calculated as follows: The magnetic induction intensity measured by the triaxial magnetic field sensor of points A and F, points B and G, and points C and H can all be used to calculate the magnetic field gradient G y To reduce the error, an average is taken, and the following calculation is performed: The magnetic induction intensity measured by the three-axis magnetic field sensor of I and L points, J and M points, and K and N points can all be calculated to obtain the magnetic field gradient G z To reduce the error, average is further performed, and the calculation is as follows: The specific method for calculating the complete second-order magnetic field gradient from the measured magnetic induction intensity by the triaxial magnetic field sensor is as follows: The gradient of the first order magnetic field gradient G along the direction of x, i.e. G x , G y and G z along the direction of x is denoted as H xxx , H yxx , H zxx , H xyx , H yyx , H zyx , H xzx , H yzx , H zzx , i.e. the second order magnetic field gradient H x : where the main diagonal elements satisfy H xxx +H yyx +H zzx = 0, H x is a symmetric matrix, H x There are 9 parameters in the matrix, but only 5 independent parameters, i.e. H xxx , H xyx , H xzx , H yyx and H yzx ; the gradient of the first order magnetic field gradient G along the y direction, i.e. G x , G y , and G z the gradient along the y direction, denoted H xxy , H yxy , H zxy , H xyy , H yyy , H zyy , H xzy , H yzy , H zzy , i.e. the second order magnetic field gradient H y : where 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, i.e. H xxy , H xyy , H xzy , H yyy and H yzy ; the gradient of the first order magnetic field gradient G along the z direction, i.e. G x , G y and G z the gradient along the z direction, denoted H xyz , H yxz , H zxz , H xyz , H yyz , H zyz , H xzz , H yzz , H zzz i.e. the second order magnetic field gradient H z : where the main diagonal elements satisfy H xxz +H yyz +H zzz = 0, H z is a symmetric matrix, H z There are 9 parameters in the matrix, but only 5 independent parameters, i.e. H xxz , H xyz , H xzz , H yyz and H yzz ; According to the spatial arrangement of the triaxial magnetic sensor and the definition of the second-order magnetic field gradient tensor, the second-order magnetic field gradient tensors at the coordinate system origin o are respectively as follows: Q and P points are calculated by the first order magnetic field gradient G measured by the magnetic induction intensity of the triaxial magnetic field sensor of E and O points, O and D points respectively x E and D points are calculated by the first order magnetic field gradient G measured by the magnetic induction intensity of the triaxial magnetic field sensor of C and H points, A and F points respectively y E and D points are calculated by the first order magnetic field gradient G measured by the magnetic induction intensity of the triaxial magnetic field sensor of K and N points, L and I points respectively z ; wherein Q is the center of the line connecting E and O, P is the center of the line connecting O and D, and the first-order magnetic field gradient G through Q and P x , the first-order magnetic field gradient G through E and D y , the first-order magnetic field gradient G through E and D z , the first-order magnetic field gradient G through E and D x , the first-order magnetic field gradient G through E and D y , the first-order magnetic field gradient G through E and D z , the second-order magnetic field gradient H along the x direction, i.e., the second-order magnetic field gradient H x , is calculated as follows: The first-order magnetic field gradients G of points G and B are calculated respectively by the magnetic induction intensity measured by the three-axis magnetic field sensors of points H and F, and points A and C x The first-order magnetic field gradients G of points S and R are calculated respectively by the magnetic induction intensity measured by the three-axis magnetic field sensors of points G and O, and points O and B y The first-order magnetic field gradients G of points E and D are calculated respectively by the magnetic induction intensity measured by the three-axis magnetic field sensors of points K and N, and points L and I z ; Wherein, R is the center of the line connecting B and O, S is the center of the line connecting G and O, and the first-order magnetic field gradient G x of G y , S and R x y The magnetic field gradient G z along the y direction, G xzy along the y direction (H yzy , H zzy , H x ) respectively with the third parameter H xxy in the magnetic field gradient along the y direction (H yxy , H zxy , H zxy ) G y along the y direction (H xyy , H yyy , H zyy ) respectively with the third parameter H zyy , G z along the z direction (H xzz , H yzz , H zzz ) respectively with the second parameter H yzz , the magnetic field gradient G x , G y and G z along the y direction, that is, the second-order magnetic field gradient H y , is calculated as follows:​ where * indicates that the parameter in this vector is repeated in H x , H y , and H z , which do not need to be solved again; T is the center of the line connecting M and O, and W is the center of the line connecting O and J; The first-order magnetic field gradients G of the M and J points are calculated respectively by the magnetic induction intensity measured by the triaxial magnetic field sensors of the N and L points, and the K and I points x The first-order magnetic field gradients G of the T and W points are calculated respectively by the magnetic induction intensity measured by the triaxial magnetic field sensors of the M and O points, and the O and J points z ; through the first order magnetic field gradient G of points M and J x , T and W z , respectively, calculate the magnetic field gradient G x and G z along the z direction; G y along the z direction (H xyz , H yyz , H zyz ) respectively with the second parameter H z along the x direction (H xzx , H yzx , H zzx ) in the second parameter H yzx , G y along the y direction (H xyy , H yyy , H zyy ) in the third parameter H zyy , G z along the z direction (H xzz , H yzz , H zzz ) in the second parameter H yzz , represented by **, the magnetic field gradient G x , G y and G z along the z direction, that is, the second order magnetic field gradient H z , is calculated as follows: where ** indicates the parameters in the vector that are solved for H x , H y , and H z , and the other parameters are repeated from the previous solution. The specific method for calculating the three-dimensional position vector of the magnetic field sensor probe to the submarine from the first-order magnetic field gradient and the second-order magnetic field gradient is as follows: by a first magnetic field gradient G in the x direction x and a second magnetic field gradient H x resulting in a three-dimensional position vector of the underwater submarine r = -4 (H x ) -1 G x (14) r is the position vector, and the three-dimensional position of the submarine in the coordinate system oxyz is r(x, y, z); By taking the first order magnetic field gradient G y and the second order magnetic field gradient H y in the y direction, the three-dimensional position vector of the underwater submarine can be obtained: r = -4 (H y ) -1 G y (15) By taking the first order magnetic field gradient G z and the second order magnetic field gradient H z in the z direction, the three-dimensional position vector of the underwater submarine can be obtained: r = -4 (H z ) -1 G z (16) The three-dimensional position vector of the submarine obtained from the first-order and second-order magnetic field gradients along the x, y and z directions is averaged to obtain The specific method for giving the longitude, latitude and other geographical parameters of the position of the magnetic field sensor probe is as follows: magnetic induction intensity B measured by the three-axis magnetic field sensor through point O xO , B yO and B zO , by comparing with the built-in geomagnetic map, give the magnetic declination longitude λ, latitude Ψ three geographical parameters; wherein B zO is the magnetic induction in the vertical direction, B xO and B yO is the magnetic induction in the horizontal direction, positive for north by east, negative for north by west; wherein geographic true north is the direction of the meridian towards the north pole, geomagnetic true north is the north of the earth's magnetic pole, i.e. the north indicated by the compass, and the declination between the geomagnetic true north and the geographic true north is the magnetic declination; The specific method for giving the angle between the coordinate system of the magnetic field sensor probe and the geographic north is as follows: According to the latitude and longitude, the magnetic induction intensity is recalculated, and compared with the actually measured magnetic induction intensity, the angle between the x-axis of the coordinate system of the magnetic field sensor probe and the geographic north is given; The International Reference Geomagnetic Field (IGRF) is a standard global model describing 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 harmonics: where r is the geocentric distance of a 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, are the spherical harmonic coefficients of the internal field magnetic potential. The geomagnetic coordinate system OXYZ is defined, in which 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 rule is satisfied. In the geomagnetic coordinate system OXYZ, the three components of the geomagnetic field are calculated by calculating the derivative of the magnetic potential spherical harmonics along the axis according to the longitude and latitude: In the formula, R is the international reference sphere radius, that is, the average radius of the earth (R = 6371.2 km), is an n-order m-degree Gaussian harmonic coefficient, the value is taken according to the 11th generation IGRF, N is a truncation order, N = 10; The parameters in the formula (18) to formula (21) such as r, m, n, The values of the parameters are described in many published documents, which are not described herein. The angle between the x-axis of the coordinate system of the magnetic field sensor probe and the geomagnetic north direction is calculated as follows: The angle between the x-axis and the geographic north in the coordinate system of the magnetic field sensing probe is north by east The z-axis is plumb down, and the y-axis complies with the right-hand rule. The specific method for giving the three-dimensional position vector of the submarine is as follows: The full tensor high order magnetic field gradient sensing system is located at latitude Ψ and longitude λ, at which the angle between the x-axis of the coordinate system of the magnetic field sensing probe and the geographic north is the angle along the north by east , the z-axis is plumb downward, and the y-axis conforms to the right-hand rule, and under the coordinate system, the three-dimensional position vector of the underwater submarine is r; The specific method for transmitting the position of the full-tensor high-order magnetic field gradient sensing 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 submarine to the remote data system is as follows: The longitude, latitude, angle between the coordinate system of the magnetic field sensor probe and the geographic north, and the three-dimensional position vector of the submarine are transmitted to the remote data system by remote communication.

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