A method for compensating magnetic interference of carrier in shipborne geomagnetic vector measurement

Abstract

The present invention discloses a method for compensating magnetic interference of a ship-borne geomagnetic vector measurement carrier, which includes compensation data acquisition and compensation parameter acquisition. In the compensation data acquisition process, the carrier only needs to navigate according to a predetermined action to complete the compensation data acquisition. The process is simple, operable and time-saving. In the compensation parameter acquisition process, the geomagnetic component constraint principle is adopted, and the compensation parameters are calculated using the least squares method. The calculation process is simple and the calculation speed is fast. In addition, the method does not require auxiliary equipment and has strong applicability. In an actual ship-borne geomagnetic vector measurement test, the accuracy of the geomagnetic vector compensated by this method reaches the nT level, which can meet the accuracy requirements of general geomagnetic measurements.

Description

Technical Field

[0001] The invention belongs to the technical field of geomagnetic vector measurement, and in particular relates to a method for compensating carrier magnetic interference in shipborne geomagnetic vector measurement. Background Art

[0002] The geomagnetic field is a vector field. Geomagnetic vector measurement can obtain the component information of the geomagnetic field, and then the seven geomagnetic elements can be obtained. Compared with geomagnetic scalar measurement, geomagnetic vector measurement has the characteristics of rich measurement information and high detection efficiency. Marine shipborne geomagnetic vector measurement is one of the main ways to obtain high-precision ocean geomagnetic vector field. When conducting shipborne geomagnetic vector field measurement, it is necessary to carry the geomagnetic vector measurement system (generally including three-component magnetometer, high-precision inertial navigation, data acquisition module, GNSS module, data storage module, structural parts, etc.) on the survey ship / survey boat, and then conduct navigation measurement.

[0003] The power plant, electrical equipment and hull structure of the survey ship / survey boat inevitably contain ferromagnetic materials, which will produce interfering magnetic fields including hard magnetism, induced magnetic fields and eddy current magnetic fields, which will seriously affect the measurement accuracy of the geomagnetic vector field. Therefore, how to compensate for the interfering magnetic field of the carrier is a key issue in the study of ship-borne geomagnetic vector measurement.

[0004] In terms of interference magnetic field compensation, in the existing compensation methods, for example, a differential compensation method for reducing the interference of the carrier of the three-component magnetic measurement system is used to compensate for the fixed interference magnetic field and the induced interference magnetic field of the carrier. First, a non-magnetic flat plate is selected as a working platform, and then the magnetic source and two three-component magnetometers are fixed on the working platform. By rotating the posture of the working platform, the interference magnetic field value is obtained by the differential method. This method requires the magnetic source to be fixed on a non-magnetic flat plate, which is not feasible under the actual ship-borne geomagnetic vector measurement conditions. For another example, a geomagnetic vector measurement error calibration method combining component and total amount constraints requires the geomagnetic vector measurement system to be encapsulated in a non-magnetic regular hexahedron box, and each face of the box is used as the bottom surface in turn, and the box is rotated to achieve the correction of interference (including soft magnetism and hard magnetism) and misalignment errors. This method can only compensate for the magnetic field generated by the interference source in the regular hexahedron, and obviously cannot compensate for the actual ship hull magnetic field. For another example, a method for compensating interference magnetic field based on fuzzy adaptive Kalman filtering, in the experimental analysis in the article, the actual application effect of this method is poor. After the measured data is compensated for interference, the errors of each component are still as high as hundreds of nT, which is obviously unacceptable in the actual application of geomagnetic vector measurement. For another example, a method for compensating for the interference of ship magnetization magnetic field, by measuring the magnetic field value of the ship traveling in a circle under the swinging state, an adaptive multi-population genetic algorithm is used to solve the induction and fixed magnetic parameters of the ship, so as to eliminate the magnetic interference of the ship, but this method only stays at the simulation level, and its actual application is unknown, and the algorithm used requires repeated iterative calculations, which is slow in calculation speed and is not conducive to the rapid compensation of interference magnetic field. For example, the magnetic interference elimination algorithm for the ocean geomagnetic three-component measurement ship based on Kalman filtering requires the measurement ship to maneuver in the nearshore area to complete the calculation of some compensation parameters, and then maneuver in the far sea area to complete the calculation of the remaining compensation parameters. In the simulation experiment, the error of the compensated geomagnetic component is better than 200nT. This method needs to complete the compensation operation in the nearshore area and the far sea area respectively. The compensation process is cumbersome and the component error after compensation still reaches 200nT, which cannot meet the requirements in actual measurement operations.

[0005] In summary, the existing carrier interference magnetic field compensation methods have the following problems: 1) The compensation method has high limitations and can only perform interference magnetic field compensation under semi-physical simulation measurement conditions, and cannot compensate for the actual hull magnetic field; 2) The compensation accuracy of the proposed method is not high. In simulation or actual measurement experiments, the error of the compensated magnetic field component is still as high as hundreds of nT, which cannot meet the actual application requirements; 3) The compensation steps are cumbersome and the calculations are complex, which is not conducive to performing high-quality and fast compensation under actual measurement conditions. Summary of the invention

[0006] To solve the above problems, the present invention proposes a method for compensating for magnetic interference of a shipborne geomagnetic vector measurement carrier, which includes a compensation data acquisition method and a compensation parameter acquisition algorithm; in the compensation data acquisition process, the compensation data acquisition can be completed by only letting the carrier navigate according to the predetermined action, and the process is simple, highly operable, and time-saving; in the compensation parameter acquisition process, the geomagnetic component constraint principle is adopted, and the compensation parameters are calculated using the least squares method, and the calculation process is simple and the calculation speed is fast. Moreover, this method does not require auxiliary equipment and has strong applicability. In the actual shipborne geomagnetic vector measurement test, the accuracy of the geomagnetic vector compensated by this method reaches the nT level, which can meet the accuracy requirements of general geomagnetic measurements.

[0007] The present invention is implemented by the following technical solutions:

[0008] A method for compensating magnetic interference of a shipborne geomagnetic vector measurement carrier is proposed, comprising:

[0009] S1) obtaining a correction model of the three-component magnetometer based on the measurement model of the carrier coordinate system;

[0010] Among them, the three-component magnetometer measurement model is B m =(I+M)B e +B h (1);

[0011] The calibration model is B e =G(B m -B h ) (2); G = (I + M) -1 ;

[0012] B m =[B mx ,B my ,B mz ] T are the three-component values ​​output by the three-component magnetometer,

[0013] B e =[B ex ,B ey ,B ez ] T is the projection vector value of the geomagnetic field in the carrier coordinate system,

[0014] B h =[B hx ,B hy ,B hz ] T is the hard magnetic interference generated by the carrier, I is the unit matrix,

[0015] is the induced magnetic field coefficient matrix;

[0016] S2) Set get

[0017]

[0018] Transform it into

[0019] Among them, B′ m =[B mx ,B my ,B mz ,-1],G1=[g 11 ,g 12 ,g 13 ,g 14 ] T , G2=[g 21 ,g 22 ,g 23 ,g 24 ] T , G3=[g 31 ,g 32 ,g 33 ,g 34 ],

[0020] S3) Control the ship carrier to sail in an S-curve cross pattern, during which n groups of measurement data are collected to obtain

[0021] S4) According to the least squares method, the best estimates of G1, G2 and G3 can be calculated as follows:

[0022]

[0023] in, is the matrix composed of the output values ​​of the three-component magnetometer; B e ' x ,B e ' y ,B e ' z The solutions include:

[0024] Calculate the geomagnetic vector in the geographic coordinate system within the compensation water area using IGRF Assume that the attitude angle output by the high-precision inertial navigation system of the geomagnetic vector measurement system during the calibration process is At (r,p,h) , according to At (r,p,h) right Rotate the coordinates to get B e ″=[B′ ex ,B′ ey ,B′ ez ] T ; is the transformation matrix from the geographic coordinate system to the carrier coordinate system: r, p, and h represent the roll angle, pitch angle, and heading angle output by the high-precision inertial navigation system, respectively;

[0025] S5) Define vector G4 = [g 14 ,g 24 ,g 34 ] T According to formula (3) and (4), GB is obtained h = G4, and the hard magnetic vector B is calculated by the least square method h ;

[0026] S6) Based on B e =G(B m -B h ) compensates the geomagnetic vector data obtained from the actual measurement operation to obtain the geomagnetic vector B in the carrier coordinate system e ;

[0027] S7) Using the attitude angle output by high-precision inertial navigation, e Rotate the coordinates to obtain the geomagnetic vector B in the geographic coordinate system g =[B gx ,B gy ,B gz ] T Compared with the prior art, the advantages and positive effects of the present invention include:

[0028] 1. When collecting compensation data, the ship carrier sails back and forth in an "S" turn and draws a "cross" pattern; compared with the traditional "eight" azimuth method, it saves more time and can reduce the impact of geomagnetic diurnal changes in the compensation process; compared with the "O" method, it can better cover the possible postures in the measurement, and the collected compensation data is more effective; 2. The least squares method is used to calculate the compensation parameters. Compared with general iterative calculation methods, Kalman filtering and other methods, this method has faster calculation speed and higher efficiency; 3. The compensation parameters are calculated using geomagnetic component constraints. Compared with the total geomagnetic field constraints, the calculated compensation parameters are more accurate and have better compensation effect on geomagnetic vector data; 4. No auxiliary equipment is required, the implementation process is simple, and it is more practical; 5. It can be extended to the magnetic interference compensation of geomagnetic vector measurement carriers based on other carriers, such as aircraft, AUV, etc.

[0029] Other features and advantages of the present invention will become more apparent after reading the detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0031] Figure 1 This is a schematic diagram of the navigation trajectory of the carrier in the magnetic interference compensation of the ship-borne geomagnetic vector measurement carrier proposed by the present invention;

[0032] Figure 2 Schematic diagram of the carrier coordinate system in the present invention;

[0033] Figure 3 The following is a schematic diagram of the implementation steps of the method for supplementing the magnetic interference of a shipborne geomagnetic vector measurement carrier proposed by the present invention;

[0034] Figure 4 The invention compares the data curves before and after compensation of the geomagnetic vector measurement based on the carrier magnetic interference supplementation method of the shipborne geomagnetic vector measurement proposed by the invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0038] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0039] In shipborne geomagnetic vector measurement, the interference of the carrier mainly includes hard magnetism, induced magnetic field and eddy current magnetic field; hard magnetism is the magnetic field retained by the hard magnetic material on the carrier after being magnetized by the external magnetic field, and its value remains fixed relative to the carrier coordinate system in a short time; induced magnetic field is the magnetic field generated by the soft magnetic material on the carrier when excited by the external magnetic field, and it changes with the posture of the carrier relative to the geomagnetic field; eddy current magnetic field is the magnetic field generated by the metal conductor on the carrier cutting the magnetic lines of force.

[0040] Among the interfering magnetic fields, the hard magnetic and induced magnetic fields have the greatest impact on the accuracy of geomagnetic vector measurement. The eddy current magnetic field is small in value and belongs to the high-frequency component, which can be removed by filtering; therefore, this method only compensates for the hard magnetic and induced magnetic fields.

[0041] Based on the concept of the present invention, before or after the operation of the ship-borne geomagnetic vector measurement system begins, the ship carrier is ordered to perform navigation maneuvers according to certain actions. During this period, compensation data is obtained to calculate the carrier magnetic interference compensation parameters, which are used to perform magnetic interference compensation on the actual measurement operation data.

[0042] In principle, when calibrating the error of a three-component magnetometer or calculating the compensation parameters of the carrier's magnetic interference, the three-component magnetometer needs to be fully rotated in space and traverse the spatial attitude in order to calculate more accurate compensation parameters; however, in the actual shipborne geomagnetic vector measurement process, the three-component magnetometer is strapdown-mounted to the carrier. Due to the limitation of the carrier's motion range, the three-component magnetometer cannot traverse the spatial attitude.

[0043] In the concept of the present invention, during the compensation navigation process, the carrier is made to make a "cross" in the manner of "S" curve navigation, such as Figure 1 As shown, the possible postures of the carrier during the formal measurement operation are covered, and the specific implementation method is as follows:

[0044] In or near the survey area, select an open water area with a small geomagnetic gradient and no obvious magnetic interference source around it, select a point in the water area (which can be marked on the electronic nautical chart), and use this point as the center to sail back and forth in an "S" curve to draw a "cross". The schematic diagram of the navigation trajectory is shown below. Figure 1 As shown in the figure, the length of each side of the "cross" is defined according to the length of the hull, usually 20 times the length of the ship. Figure 1 The "L" in it stands for captain.

[0045] Establish carrier coordinate system OX b Y b Z b , its OX b Axis along the carrier horizontal axis to the right, OY b The axis moves forward along the longitudinal axis of the carrier, OZ b The axis is upward along the vertical axis of the carrier. Usually, the three-component magnetometer and high-precision inertial navigation in the geomagnetic vector measurement system are installed through structural parts, and the coordinate system between the two has been calibrated and the two coordinate systems are in an aligned state; suppose the three-component magnetometer coordinate system OX m Y m Z m , inertial navigation coordinate system OX p Y p Z p With the carrier coordinate system one.

[0046] In the carrier coordinate system, when considering the hard magnetic and induced magnetic field interference of the carrier, the measurement model of the three-component magnetometer can be expressed as:

[0047] B m =(I+M)B e +B h (1)

[0048] Among them B m =[B mx ,B my ,B mz ] T is the three-component value output by the three-component magnetometer, B e =[B ex ,B ey ,B ez ] T is the projection vector value of the geomagnetic field in the carrier coordinate system, B h =[B hx ,B hy ,B hz ] T is the hard magnetic interference generated by the carrier, I is the unit matrix, is the induced magnetic field coefficient matrix.

[0049] Through the above measurement model, the correction model of three-component magnetometer data can be obtained:

[0050] B e =G(B m -B h ) (2)

[0051] Where G = (I + M) -1 According to the correction model, only the coefficient matrix G and the hard magnetic vector B are required. h, the output B of the three-component magnetometer can be used m , and obtain the real geomagnetic vector B under the load system e , which realizes the compensation of the carrier interference magnetic field.

[0052] In the correction model, the coefficient matrix G and the hard magnetic vector B h The process of obtaining is as follows:

[0053] The above coefficient matrix G is a 3×3 matrix, let it be Expanding formula (2) yields:

[0054]

[0055] From formula (3), we can get:

[0056]

[0057] Among them, B′ m =[B mx ,B my ,B mz ,-1],G1=[g 11 ,g 12 ,g 13 ,g 14 ] T , G2=[g 21 ,g 22 ,g 23 ,g 24 ] T , G3=[g 31 ,g 32 ,g 33 ,g 34 ],

[0058] In the actual carrier magnetic interference compensation process, multiple sets of measurement data will be collected, and the form of formula (4) becomes:

[0059]

[0060] The first formula B in formula (5) ex (i) = B′ m (i) G1, (i=1,2,...,n,n>4) is taken as an example, and expanded to obtain:

[0061]

[0062] Formula (6) can be abbreviated as:

[0063] B′ ex =B″ m G1 (7)

[0064] In the formula,

[0065] According to formula (7), when B″ m , B′ ex When is known, the best estimate of G1 can be obtained according to the least squares principle:

[0066]

[0067] B″ m It is a matrix composed of the actual output values ​​of the three-component magnetometer and is a known quantity.

[0068] B′ ex The method to obtain is as follows:

[0069] In practice, carrier magnetic interference compensation is usually selected in waters with small geomagnetic gradient and no obvious geomagnetic anomalies and magnetic interference sources around. At this time, the geomagnetic vector calculated by IGRF can be used to approximately represent the real background geomagnetic vector here; the geomagnetic vector calculated in the geographic coordinate system is designed to be During the calibration process, the attitude angle output by the high-precision inertial navigation system of the geomagnetic vector measurement system is At (r,p,h) According to At (r,p,h) right By rotating the coordinates, we can obtain the geomagnetic vector value B corresponding to each attitude in the carrier coordinate system. e ″=[B′ ex ,B′ ey ,B′ ez ] T , the process is as follows:

[0070]

[0071] in, is the transformation matrix from geographic system to carrier coordinate system:

[0072] r, p, and h represent the roll angle, pitch angle, and heading angle output by the high-precision inertial navigation system, respectively.

[0073] Through the above rotation, we get B′ ex ; Using formula (8) to calculate, we can get the best estimate of G1. Similarly, we can calculate the best estimates of G2 and G3.

[0074] The coefficient matrix G can be obtained based on G1, G2, and G3.

[0075] Hard magnetic vector B h Calculate as follows:

[0076] Define vector G4, let G4 = [g 14,g 24 ,g 34 ] T , referring to formulas (3) and (4):

[0077] GB h =G4 (10)

[0078] In the formula, G and G4 are known quantities. According to the least squares principle, the hard magnetic vector B can be obtained: h :

[0079] B h =(G T G) -1 G T G4 (11).

[0080] Through the above derivation and calculation, the coefficient matrix G and hard magnetic vector B have been obtained. h , the geomagnetic vector data obtained from the actual measurement operation can be compensated in real time online or offline according to formula (2).

[0081] After the carrier magnetic interference compensation, the geomagnetic vector B under the carrier system is obtained. e ; Using the attitude angle output by high-precision inertial navigation, e By rotating the coordinates, we can get the geomagnetic vector B in the geographic coordinate system. g =[B gx ,B gy ,B gz ] T , the process is as follows:

[0082]

[0083] in, is the rotation matrix from the carrier system to the geographic coordinate system:

[0084] r, p, and h represent the roll angle, pitch angle, and heading angle output by the high-precision inertial navigation system, respectively.

[0085] The flow chart of the compensation method is shown in Figure 3 .

[0086] In a specific embodiment of the present invention, during the compensation navigation process, the measured data collected are shown in the following table:

[0087] Table 1

[0088]

[0089] The geomagnetic vector in the geographic coordinate system within the compensated water area calculated using IGRF is:

[0090]

[0091] Calculation: G1 = [0.9967, -0.0090, 0.0100, 622.4720] T , G2=[0.0081,1.0027,-0.0016,-446.5671] T , G3=[-0.0014,-0.0038,1.0076,-504.6515] T .

[0092] The coefficient matrix

[0093] G4=[622.4720,-446.5671,-504.6515] T .

[0094] Calculate B h =[625.5000,-451.2034,-501.6596] T .

[0095] According to the calculated coefficient matrix and vector, the measured data is compensated, and the geomagnetic data before and after compensation are rotated to the geographic coordinate system according to the attitude angle, such as Figure 4 shown.

[0096] It should be noted that, in the specific implementation process, the above-mentioned control part can be implemented by a hardware processor executing computer execution instructions in software form stored in the memory, which will not be elaborated here, and the programs corresponding to the actions performed by the above-mentioned control can be stored in the computer-readable storage medium of the system in software form, so that the processor can call and execute the operations corresponding to the above modules.

[0097] The computer-readable storage medium mentioned above may include volatile memory, such as random access memory; may also include non-volatile memory, such as read-only memory, flash memory, hard disk or solid-state drive; may also include a combination of the above types of memory.

[0098] The processor mentioned above may also be a general term for multiple processing elements. For example, the processor may be a central processing unit, or other general-purpose processors, digital signal processors, application-specific integrated circuits, field programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc., or may be a dedicated processor.

[0099] It should be pointed out that the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for compensating magnetic interference of a shipborne geomagnetic vector measurement carrier, characterized in that: include: S1) obtaining a correction model of the three-component magnetometer based on the measurement model of the carrier coordinate system; Among them, the three-component magnetometer measurement model is B m =(I+M)B e +B h (1); The calibration model is B e =G(B m -B h ) (2); G = (I + M) -1 ; B m =[B mx ,B my ,B mz ] T are the three-component values ​​output by the three-component magnetometer, B e =[B ex ,B ey ,B ez ] T is the projection vector value of the geomagnetic field in the carrier coordinate system, B h =[B hx ,B hy ,B hz ] T is the hard magnetic interference generated by the carrier, I is the unit matrix, is the induced magnetic field coefficient matrix; S2) Set get Transform it into where B′ m =[B mx ,B my ,B mz , -1], G1 = [g 11 , g 12 , g 13 , g 14 T , G2 = [g 21 , g 22 , g 23 , g 24 T , G3 = [g 31 , g 32 , g 33 , g 34 , ​​ S3) Control the ship carrier to sail in an S-curve cross pattern, during which n groups of measurement data are collected to obtain S4) According to the least squares method, the best estimates of G1, G2 and G3 are: in, is the matrix composed of the output values ​​of the three-component magnetometer; B e ' x ,B e ' y ,B e ' z The solutions include: Calculate the geomagnetic vector in the geographic coordinate system using IGRF Assume that the attitude angle output by the high-precision inertial navigation system of the geomagnetic vector measurement system during the calibration process is At (r,p,h) , according to At (r,p,h) right Rotate the coordinates to get B e ″=[B′ ex ,B′ ey ,B′ ez ] T ; is the transformation matrix from the geographic coordinate system to the carrier coordinate system: r, p, and h represent the roll angle, pitch angle, and heading angle output by the high-precision inertial navigation system, respectively; S5) Define vector G4 = [g 14 ,g 24 ,g 34 ] T According to formula (2) and (3), GB is obtained h = G4, and the hard magnetic vector B is calculated by the least square method h ; S6) Based on B e =G(B m -B h ) compensates the geomagnetic vector data obtained from the actual measurement operation to obtain the geomagnetic vector B in the carrier coordinate system e ; S7) Using the attitude angle output by high-precision inertial navigation, e Rotate the coordinates to obtain the geomagnetic vector B in the geographic coordinate system g =[B gx ,B gy ,B gz ] T .

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