Compensation method for geomagnetic vector measurement system based on three-dimensional helmholtz coil

Abstract

The application discloses a geomagnetic vector measurement system compensation method based on a three-dimensional helmholtz coil, and steps include: S01. Constructing a geomagnetic vector measurement system interference magnetic field compensation model; S02. Placing the geomagnetic vector measurement system in the center region of the three-dimensional helmholtz coil, and generating magnetic field data of different directions and different sizes through the three-dimensional helmholtz coil, so as to obtain multiple groups of measurement data, wherein the measurement data include output values of three-axis magnetic field sensors, true values generated by the three-dimensional helmholtz coil and a change rate of the true values generated by the three-dimensional helmholtz coil with time; S03. Obtaining an error model equation group according to the data obtained in the step S02 and the geomagnetic vector measurement system interference magnetic field compensation model; and S04. Solving parameters in the error model equation group, and compensating the magnetic interference field of the geomagnetic vector measurement system by using the solved parameters. The application has the advantages of simple operation, low cost, high compensation precision, strong flexibility and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geomagnetic vector measurement, and particularly relates to a geomagnetic vector measurement system compensation method based on a three-dimensional helmholtz coil. BACKGROUND

[0002] The geomagnetic vector measurement (north, vertical and east components) has very important applications in many occasions, such as geological survey, autonomous underwater vehicle (AUV) navigation, unexploded ordnance detection (UXO) and the like. The geomagnetic vector measurement system mainly comprises a three-axis fluxgate magnetometer and an attitude measurement unit (such as an inertial navigation unit), the three-axis fluxgate magnetometer provides the projection of the geomagnetic field on the magnetometer coordinate, and the attitude measurement unit provides the attitude of the magnetometer, and the attitude information provided by the attitude measurement unit is used to convert the vector into a geographic coordinate system.

[0003] In the geomagnetic vector measurement system, there are mainly three types of error sources: magnetometer error, misalignment error between the inertial coordinate and the magnetometer coordinate, and magnetic interference error caused by ferromagnetic materials, and these errors can reach several nT, so it is necessary to calibrate and compensate the geomagnetic vector measurement system, and among them, the magnetic interference error caused by ferromagnetic materials is the most serious. The interference magnetic field is closely related to the ferromagnetic components and other electrical equipment (such as inertial elements, power circuit modules) around the magnetometer and the interference of the application platform. The above magnetic interference field can be divided into permanent field, induced field and eddy current field, and compared with the permanent magnetic field, the induced and eddy current fields are more complex, especially the eddy current field determined by the direction, amplitude and time variation of the earth's magnetic field. Therefore, the eddy current field cannot be ignored in the mobile geomagnetic vector measurement.

[0004] The essence of the magnetic field interference compensation is to estimate the parameters of the compensation model, and to calculate the interference field by using the parameters. The magnetic interference field compensation of the geomagnetic vector measurement system mainly includes three key parts: (1) compensation model; (2) compensation strategy (or equation construction process); (3) compensation parameter estimation, and the accuracy of the compensation model, the compensation strategy and the compensation parameter estimation will directly affect the final compensation effect. For the calibration and compensation problem of the geomagnetic vector measurement system, the following several ways are usually adopted in the prior art:

[0005] 1. The three-axis fluxgate magnetometer is compensated based on the attitude rotation strategy, including three different attitude rotation strategies (symmetric rotation, orthogonal rotation and random rotation) to construct equations to realize compensation, and since the selection of the measurement position is representative and covers the entire attitude space, the compensation effect of the symmetric rotation strategy is the best. However, this kind of way needs to rotate the geomagnetic vector measurement system, and there will be problems of sensitivity to the geomagnetic field gradient and environmental geomagnetic interference.

[0006] 2. A component compensation method for geomagnetic vector measurement system based on a parallelepiped frame. However, the rotational attitude provided by the parallelepiped frame is limited and insufficient to construct equations to accurately estimate parameters. Furthermore, the application scenarios are limited because the magnetic sensor and the inertial navigation system must be deployed separately.

[0007] 3. The error parameters in the compensation of geomagnetic field vector measurement components are estimated using the Lagrange multiplier method to achieve compensation, but the eddy current field is not considered in the component compensation model.

[0008] In summary, the correction and compensation effects of existing technologies for geomagnetic vector measurement systems still need improvement and their application scenarios are limited. In addition, the distribution of measurement data in attitude space (when the system is deployed in different attitudes) is often insufficient or unreasonable, which may lead to multicollinearity problems, affecting the final compensation results. Furthermore, the compensation methods in existing technologies usually rely on the rotation of the system in the geomagnetic field, while the geomagnetic field should remain constant and the system should be deployed in different attitudes to obtain different magnetic field component outputs. Therefore, the compensation process is not only sensitive to the geomagnetic gradient but also to environmental geomagnetic interference, which makes it difficult to meet the above requirements in practical applications. Summary of the Invention

[0009] The technical problem to be solved by the present invention is: in view of the technical problems existing in the prior art, the present invention provides a geomagnetic vector measurement system compensation method based on three-dimensional Helmholtz coil, which is simple to operate, low in cost, high in compensation accuracy and effect, and highly flexible.

[0010] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0011] A compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil, comprising the following steps:

[0012] S01 divides the interfering magnetic field into permanent magnetic field, induced magnetic field and eddy current magnetic field, and constructs an interfering magnetic field compensation model for the geomagnetic vector measurement system, which includes a triaxial magnetic field sensor.

[0013] S02. Place the geomagnetic vector measurement system in the central region of the three-dimensional Helmholtz coil, and generate magnetic field data of different directions and magnitudes through the three-dimensional Helmholtz coil to obtain multiple sets of measurement data. The measurement data includes the output value of the triaxial magnetic field sensor, the true value generated by the three-dimensional Helmholtz coil, and the rate of change of the true value generated by the three-dimensional Helmholtz coil over time.

[0014] S03. Based on the data obtained in step S02 and the interference magnetic field compensation model of the geomagnetic vector measurement system, the error model equation set is obtained;

[0015] S04. Solve for the parameters in the error model equations and use the solved parameters to compensate for the magnetic interference field of the geomagnetic vector measurement system.

[0016] Furthermore, in step S01, the interference magnetic field compensation model is constructed according to the following formula:

[0017]

[0018] Among them, H m H is the measured value of the triaxial magnetic field sensor that needs compensation. mx H my H mz For H m The three components H on the x, y, and z axes mx H my H mz H p Represents permanent magnet magnetic field and H px H py H pz H respectively p The three components on the x, y, and z axes; A i H0 represents the induced magnetic field, and since the induced magnetic field is determined by the external background magnetic field, the induced magnetic field is represented as H. i That is:

[0019]

[0020] A i It is the induction coefficient matrix, a ij For A i The inductance coefficients in the figure, i,j=x,y,z,A i This relates to the induced magnetic field in the i-direction of the body, which is generated by a magnetic field applied in the j-direction of the body;

[0021] The eddy current magnetic field is represented by H, and since it is proportional to the rate of change of the eddy current magnetic field with the external background magnetic field, the eddy current magnetic field is represented as H. e That is, it can be expressed as:

[0022]

[0023] Where H0 is the true value of the background geomagnetic field component in the coordinate system of the triaxial magnetic field sensor, H 0x H 0y H 0z Let H0 have three components on the x, y, and z axes, and let A e It is the eddy current coefficient matrix, b ij For A e The eddy current coefficients in the figure, i,j=x,y,z,Ae with respect to the vortex magnetic field in the body i direction, the vortex magnetic field being generated by the field applied in the body j direction.

[0024] Further, the interference magnetic field compensation model is transformed to obtain a final interference magnetic field compensation model:

[0025]

[0026] Wherein, Δt is the time change value, and Δ represents the change value.

[0027] Further, the error model equation group constructed in the step S03 is:

[0028]

[0029] Wherein, N represents the number of measurement points, and dH0 / dt represents the rate of change of the H0 magnetic field with respect to time.

[0030] Further, the rate of change of the H0 magnetic field with respect to time dH0 / dt in the error model equation group is obtained by controlling the current of the three-dimensional Helmholtz coil.

[0031] Further, in the step S02, when the geomagnetic vector measurement system is placed in the central region of the three-dimensional Helmholtz coil, the three sensitive axis directions of the three-axis magnetic field sensor of the geomagnetic vector measurement system are aligned with the three orthogonal directions of the three-dimensional Helmholtz coil.

[0032] Further, in the step S02, when the three-dimensional Helmholtz coil generates magnetic field data of different directions and different sizes, the current sequence of the three-dimensional Helmholtz coil is controlled to generate different directions and amplitudes in the three-dimensional spherical involute, and the three orthogonal coil current sequences are obtained according to the following spherical involute equation:

[0033]

[0034] Wherein, R represents the involute radial, θ represents the involute development angle, and α represents the involute pressure angle, the current sequence will change with the change of θ and α, and the sampling interval Δθ and Δα will determine the magnetic field change rate.

[0035] Further, in the step S04, the linear least square method is used to solve the parameters.

[0036] Further, in the step S04, when the parameters in the error model equation group are solved, it further includes judging whether the magnetic interference field of the geomagnetic vector measurement system compensated by the solved parameters meets the preset compensation requirement, if yes, the compensation is ended, otherwise, returning to the step S02 until the preset compensation requirement is met.

[0037] A geomagnetic vector measurement system compensation system based on a three-dimensional Helmholtz coil, comprising:

[0038] A measurement control module for placing the geomagnetic vector measurement system in the center of the three-dimensional Helmholtz coil and generating magnetic field data of different directions and different sizes through the three-dimensional Helmholtz coil to obtain a plurality of sets of measurement data, the measurement data including output values of the three-axis magnetic field sensor, true values generated by the three-dimensional Helmholtz coil, and a rate of change of the true values generated by the three-dimensional Helmholtz coil over time;

[0039] A compensation module for obtaining an error model equation set according to the data obtained by the measurement control module and a geomagnetic vector measurement system interference magnetic field compensation model, and solving parameters in the error model equation set to compensate for the magnetic interference field of the geomagnetic vector measurement system using the solved parameters, the geomagnetic vector measurement system interference magnetic field compensation model being constructed by dividing the magnetic interference source into a permanent magnetic field, an induced magnetic field, and an eddy current magnetic field, and the geomagnetic vector measurement system including a three-axis magnetic field sensor.

[0040] Compared with the prior art, the advantages of the present application are that:

[0041] 1. The present application establishes an interference magnetic field component compensation model including a permanent magnetic field, an induced magnetic field, and an eddy current magnetic field, places the geomagnetic vector measurement system in the center of the uniform area of the three-dimensional Helmholtz coil, uses the coil to generate magnetic fields of different amplitudes, different directions, and different rates of change to establish an equation set of error parameters, estimates the error parameters by solving the equation set, quickly generates sufficient representative data to construct the equation, and greatly reduces the measurement error of the geomagnetic vector measurement system.

[0042] 2. The present application can conveniently obtain a sufficient and reasonable data set by controlling the coil current, quickly generates sufficient representative data to construct the equation, and not only realizes simple and low-cost compensation, but also does not need to construct a compensation equation through a rotating platform, and the magnetic field data generated by the three-dimensional Helmholtz coil can ensure that the equation does not have complex collinearity, so that the error parameters can be more accurately estimated.

[0043] 3. The present application uses the three-dimensional Helmholtz coil, can flexibly compensate according to different application scenarios, ensures good compensation accuracy, and compared with the traditional rotating strategy, can also complete the compensation in a shorter time. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is the implementation flowchart of the geomagnetic vector measurement system compensation method based on the three-dimensional Helmholtz coil of the present embodiment.

[0045] Figure 2is a schematic diagram of the structural principle of the geomagnetic vector measurement system in the embodiment.

[0046] Figure 3 is a detailed implementation process schematic diagram of the geomagnetic vector measurement system compensation in the specific application embodiment.

[0047] Figure 4 is a schematic diagram of the principle of the partial current constraint of the three orthogonal coils in the specific application embodiment.

[0048] Figure 5 is a schematic diagram of the partial alternating current curve of the three orthogonal coils obtained in the specific application embodiment. DETAILED DESCRIPTION

[0049] The application will be further described in conjunction with the drawings and specific preferred embodiments in the specification, but the protection scope of the application is not limited thereby.

[0050] As Figure 1 shown, the steps of the geomagnetic vector measurement system compensation method based on the three-dimensional Helmholtz coil in the embodiment include:

[0051] S01. Divide the interference magnetic field into permanent magnetic field, induced magnetic field and eddy current magnetic field, construct the interference magnetic field compensation model of the geomagnetic vector measurement system, and the geomagnetic vector measurement system as Figure 2 shown, includes a high-precision optical fiber inertial navigation system INS and a three-axis magnetic field sensor (specifically a three-axis fluxgate magnetometer);

[0052] S02. Place the geomagnetic vector measurement system in the central region of the three-dimensional Helmholtz coil, and generate magnetic field data of different directions and different sizes through the three-dimensional Helmholtz coil, to obtain multiple sets of measurement data, including the output value of the three-axis magnetic field sensor, the true value generated by the three-dimensional Helmholtz coil and the rate of change of the true value generated by the three-dimensional Helmholtz coil with time;

[0053] S03. Obtain the error model equation set according to the data obtained in step S02 and the interference magnetic field compensation model of the geomagnetic vector measurement system;

[0054] S04. Solve the parameters in the error model equation set, and compensate the magnetic interference field of the geomagnetic vector measurement system using the solved parameters.

[0055] The interference sources mainly come from the ferromagnetic components and other electrical equipment in the system, such as the inertial navigation system and the power module, which can be divided into permanent magnetic field, induced magnetic field and eddy current magnetic field. The permanent magnetic field remains constant for a long time, and the permanent magnetic field can be expressed as:

[0056] H p =[H px Hpy H pz ] T (1)

[0057] Among them, H p It's permanent magnet interference, H px H py H pz For H p The three components on the x, y, and z axes.

[0058] Induced magnetic field H i Determined by the external background magnetic field, it can be expressed as:

[0059]

[0060] Among them, A i It is the induction coefficient matrix, a ij For A i The inductance coefficients in the figure, i,j=x,y,z,A i It relates to the induced magnetic field in the i-direction of the body, which is generated by the magnetic field applied in the j-direction of the body.

[0061] Eddy current magnetic field H e It is proportional to the rate of change of the external background magnetic field, and can be expressed as:

[0062]

[0063] Among them, A e It is the eddy current coefficient matrix, b ij For A e The eddy current coefficients in the figure, i,j=x,y,z,A e It relates to the eddy current magnetic field in the i-direction of the main body, which is generated by the field applied in the j-direction of the main body.

[0064] In step S01 of this embodiment, a mathematical model of a triaxial magnetic field sensor considering magnetic field interference is specifically constructed based on the above equations (1) to (3), namely, the interference magnetic field compensation model:

[0065]

[0066] Among them, H m The measured value of the triaxial magnetometer that needs compensation, H mx H my H mz For H m The three components H on the x, y, and z axes mx H my H mz H0 is the true value of the background geomagnetic field component in the triaxial magnetometer coordinate system. 0xH 0y H 0z H0is the true value of the geomagnetic field component on the x, y, z axis.

[0067] The differential of the true value H0of the geomagnetic field component with respect to time can be expressed as formula (5) as follows, and the differential value can be obtained by controlling the current of the three-dimensional Helmholtz coil in the embodiment The differential value can be accurately obtained.

[0068]

[0069] Since it is unknown in the actual measurement process, dH0 / dt in formula (4) can be replaced by dH / dt, and the influence of the difference is very small. m

[0070] Further combining formula (5), the mathematical model of the three-axis magnetic sensor considering the magnetic field interference is transformed to obtain the final interference magnetic field compensation model of the geomagnetic vector measurement system as follows:

[0071]

[0072]

[0073]

[0074] Where Δt is the time change value, and Δ represents the change value.

[0075] As can be seen from the above, there are 21 (H px ,H py ,H pz , a ij i,j=x,y,z, b ij i,j=x,y,z) unknown parameters in the model that need to be estimated. When the system collects measurement data samples H mx ,H my ,H mz , combined with the reference true value H 0x ,H 0y ,H 0z provided by the 3D Helmholtz coil, formula (6)-(8) can be obtained. In the specific application embodiment, at least 7 measurement values are required to be collected to form a plurality of equation groups according to the above interference magnetic field compensation model, and subsequent parameter estimation can be realized by solving the equation group. Preferably, by obtaining a sufficient number of representative data sets, each unknown parameter can be more accurately estimated, thereby ensuring the compensation accuracy.

[0076] ​The step S02 of the embodiment places the geomagnetic vector measurement system in the central region of the three-dimensional Helmholtz coil, uses the three-dimensional Helmholtz coil to generate magnetic field data of different directions and different sizes, constructs error model equations, and then estimates 21 unknown parameters in the model. The embodiment specifically uses a 3D Helmholtz coil, which is composed of three completely orthogonal coils, and the coils are driven by current. Each coil has a corresponding current controller. By controlling the current flowing through the coil, any magnetic field component can be generated in the uniform region at the center of the three-dimensional coil. Therefore, the three-dimensional Helmholtz coil can generate a high-precision magnetic field uniform region of any size. The embodiment realizes compensation by combining the three-dimensional Helmholtz coil. The compensation can be adaptive and flexible according to different application scenarios, for example, the gradient of the background magnetic field can be simulated. The compensation is simple and convenient to implement, and good compensation accuracy can be ensured.

[0077] Preferably, when the geomagnetic vector measurement system is placed in the central region of the three-dimensional Helmholtz coil in step S02, the three sensitive axis directions of the three-axis magnetic field sensor of the geomagnetic vector measurement system are specifically aligned with the three orthogonal directions of the three-dimensional Helmholtz coil.

[0078] Preferably, when the three-dimensional Helmholtz coil is used to generate magnetic field data of different directions and different sizes, the current sequence of the three-dimensional Helmholtz coil is specifically controlled to generate different directions and amplitudes in the three-dimensional spherical involute. The current sequence of the three orthogonal coils is specifically obtained according to the following spherical involute equation:

[0079]

[0080] where R represents the involute radial, θ represents the involute expansion angle, and α represents the involute pressure angle. The current sequence will change with the changes of θ and α. The sampling interval Δθ and Δα will determine the magnetic field change rate.

[0081] In a specific application embodiment, the generation of different directions and amplitudes in the three-dimensional spherical involute is as shown in Figure 4 According to the generation of the current of the three orthogonal coils in the three-dimensional spherical involute, part of the current curve is as shown in Figure 5

[0082] After generating magnetic field components with different amplitudes and directions in the uniform region of the three-dimensional Helmholtz coil, a plurality of measurement data can be obtained through measurement, including the output value H m of the three-axis magnetic field sensor, the true value H0 generated by the three-dimensional Helmholtz coil, and the change rate of the true value generated by the three-dimensional Helmholtz coil over time Based on the plurality of measurement data and the model as shown in equations (6) to (8), the model equation set can be constructed as:

[0083] ​

[0084] Where N represents the number of measurement points, and dH0 / dt represents the rate of change of the H0 magnetic field with respect to time.

[0085] By further solving the linear equations in equation (9), the 21 unknown parameters of the permanent magnet, induction, and eddy current fields can be estimated. After accurately estimating all 21 unknown parameters, the magnetic interference field can be calculated based on the error parameters to obtain the expected true value of the geomagnetic vector, thus realizing magnetic interference field compensation of the geomagnetic vector measurement system. Preferably, the linear least squares method can be used to solve the parameters. Since the magnetic field data generated by the three-dimensional Helmholtz coil can ensure that the equations do not have complex collinearity, the linear least squares method can accurately and quickly estimate the error parameters, which can further improve the solution efficiency and accuracy.

[0086] In step S04 of this embodiment, when solving for the parameters in the error model equations, it also includes determining whether the compensation of the magnetic interference field of the geomagnetic vector measurement system using the solved parameters meets the preset compensation requirements. If it does, the compensation ends; otherwise, it returns to step S02 until the preset compensation requirements are met. Through multiple iterations, the required compensation accuracy can be accurately achieved in the end.

[0087] like Figure 3 As shown, in a specific application embodiment, the geomagnetic vector measurement system is first placed on a non-magnetic platform at the center of a three-dimensional Helmholtz coil (e.g., Figure 2 As shown in the figure), magnetic field components with different amplitudes and directions are generated in the uniform region of the coil to construct the model error equation, as shown in equation (9). Then, the least squares sampling algorithm is used to estimate each unknown parameter to compensate the geomagnetic vector measurement system. After each compensation, it is judged whether the compensation accuracy is met. If not, the above steps are repeated until the compensation accuracy requirement is finally met. In this embodiment, the geomagnetic vector measurement system is placed in the center of the uniform region of the three-dimensional Helmholtz coil. The magnetic fields with different amplitudes, directions and rates of change generated by the coil are used to establish the equation set of error parameters. This makes it possible to establish the equation set without relying on the attitude of the traditional rotating measurement system during the entire compensation process. This not only achieves simple operation and low cost, but also allows for adaptive and flexible compensation according to different application scenarios, while ensuring good compensation accuracy.

[0088] The application is applied to the component compensation of the geomagnetic vector measurement system, and the compensation model of the permanent magnetic field, the induced magnetic field and the eddy current magnetic field is established, different vector magnetic fields are generated by using the three-dimensional Helmholtz coil, the geomagnetic vector measurement system is placed in the central region of the three-dimensional Helmholtz coil, the error equation set is formed according to the compensation model and a plurality of groups of measurement data, the error parameter estimation is carried out by solving the equation set, sufficient representative data can be quickly generated to construct the equation, the compensation efficiency and the precision are high, the measurement error of the geomagnetic vector measurement system can be greatly reduced, and the compensation equation does not need to be constructed by using the rotating platform. In addition, the application can be applied to various scenes of the geomagnetic field vector measurement system carried on the autonomous underwater vehicle or the unmanned aerial vehicle and the like, when the three-dimensional Helmholtz coil is large enough, the interference source of the platform can be considered together with the interference source of the measurement system itself.

[0089] In order to verify the effectiveness of the above-mentioned method of the application, a compensation test is carried out by using the method of the application in the specific application embodiment, and the experimental device is shown in Figure 2 , and includes: 1) a geomagnetic field vector measurement system, including a high-precision optical fiber inertial navigation system (INS, providing attitude information) and a Mag-13 three-axis fluxgate magnetometer (measuring magnetic components); 2) a 3D Helmholtz coil (creating an arbitrary magnetic field component); 3) a data processor and data acquisition software and data processing software. The sampling rate of the magnetometer is specifically 20 Hz. It should be noted that the three-axis magnetometer has been calibrated before the experiment, and the output error is reduced to below 1 nT after calibration. The inertial navigation system has also been calibrated in the laboratory by using a three-degree-of-freedom turntable.

[0090] According to the Mag-13 magnetometer manual, the main performance indicators are as follows: the magnetic field range of each sensor axis: 100 uT; orthogonal error: <±0.1°; offset: <5 nT; noise: <5 pTrms / Hz-1Hz is 1 / 2. According to the INS manual, the main performance specifications are as follows: attitude accuracy: <0.008°; head angle range: 0°-360°; pitch angle range: ±90°; roll angle range: ±180°. According to the 3D Helmholtz coil manual, the main performance specifications are as follows: coil size: 1 meter; uniformity: 0.1% in the central region of 260 cm3; orthogonal error: <±0.01°;

[0091] The specific steps of the geomagnetic vector measurement system compensation are realized in the embodiment:

[0092] ①The geomagnetic vector measurement system is placed in the center of the three-dimensional Helmholtz coil, as shown in Figure 2 .

[0093] ②The three-dimensional Helmholtz coil generates a magnetic field under the pre-defined coil current excitation, and the output value H of the three-axis magnetic field sensor is started to be recordedm and the rate of change of H0 with time, and part of the data is shown in Table 1.

[0094] ③According to the obtained data and formula (9), the following equation group is obtained:

[0095]

[0096] ④Solving the above linear equation group, 21 unknown parameters of the permanent magnet, induction and eddy current field are estimated, and whether the compensation accuracy requirement is met is judged. If it is met, the compensation is ended. Otherwise, return to step ② until the requirement is met. When all 21 unknown parameters are accurately estimated, the magnetic disturbance field of the geomagnetic vector measurement system can be compensated using the error parameters.

[0097] Table 1: Part of the measurement data of the three-axis magnetic field sensor and the true value data generated by the coil

[0098]

[0099] As shown in Table 2, after compensation using the proposed method, the root mean square errors of the north, vertical, east and total intensity are reduced from 3448.3nT, 4396.2nT, 4096.2nT and 3994.1nT to 58.92nT, 60.88nT, 65.72nT and 65.92nT, respectively.

[0100] Table 2: Interference magnetic field compensation effect (nT)

[0101]

[0102] From the test results, it can be seen that the interference magnetic field compensation method of the geomagnetic vector measurement system based on the three-dimensional Helmholtz coil can effectively eliminate the interference magnetic field around the magnetometer, and effectively improve the accuracy and reliability of the geomagnetic vector measurement.

[0103] The embodiment also provides a geomagnetic vector measurement system compensation system based on a three-dimensional Helmholtz coil, which comprises:

[0104] A measurement control module is configured to place the geomagnetic vector measurement system in the central region of the three-dimensional Helmholtz coil, and generate magnetic field data of different directions and different sizes through the three-dimensional Helmholtz coil to obtain multiple sets of measurement data, the measurement data including output values of the three-axis magnetic field sensor, true values generated by the three-dimensional Helmholtz coil, and the rate of change of the true values generated by the three-dimensional Helmholtz coil with time;

[0105] The compensation module is configured to obtain an error model equation group according to the data obtained by the measurement control module and a geomagnetic vector measurement system interference magnetic field compensation model, and solve parameters in the error model equation group, and compensate a magnetic interference field of the geomagnetic vector measurement system using the solved parameters, wherein the geomagnetic vector measurement system interference magnetic field compensation model is obtained by dividing the magnetic interference source into a permanent magnetic field, an induced magnetic field and an eddy current magnetic field, and the geomagnetic vector measurement system comprises a three-axis magnetic field sensor.

[0106] The compensation system of the geomagnetic vector measurement system based on the three-dimensional Helmholtz coil corresponds to the compensation method of the geomagnetic vector measurement system based on the three-dimensional Helmholtz coil, and will not be described here.

[0107] The compensation model of the interference magnetic field component containing the permanent magnetic field, the induced magnetic field and the eddy current magnetic field is established, different vector magnetic fields are generated by using the three-dimensional Helmholtz coil, and then the error parameter equation is constructed, and a sufficient and reasonable data set can be obtained by controlling the coil current, and a sufficient representative data is quickly generated to construct the equation, so that the compensation equation does not need to be constructed by the rotating platform, and the magnetic field data generated by using the three-dimensional Helmholtz coil can ensure that the equation does not exist complex collinearity, so that the error parameters can be more accurately estimated, and the three-dimensional Helmholtz coil is also used, and flexible compensation can be performed according to different application scenarios, so that the compensation is simple to realize, low in cost, and high in compensation precision, and compared with the traditional rotating strategy, the compensation can be completed in a shorter time.

[0108] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Therefore, any simple modification, equivalent change and modification of the above embodiment without departing from the technical solution of the present application, and according to the technical essence of the present application, should fall within the protection scope of the technical solution of the present application.

Claims

1. A compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil, characterized in that the steps include... include: S01 divides the interfering magnetic field into permanent magnetic field, induced magnetic field and eddy current magnetic field, and constructs an interfering magnetic field compensation model for the geomagnetic vector measurement system, which includes a triaxial magnetic field sensor. S02. Place the geomagnetic vector measurement system in the central region of the three-dimensional Helmholtz coil, and generate magnetic field data of different directions and magnitudes through the three-dimensional Helmholtz coil to obtain multiple sets of measurement data. The measurement data includes the output value of the triaxial magnetic field sensor, the true value generated by the three-dimensional Helmholtz coil, and the rate of change of the true value generated by the three-dimensional Helmholtz coil over time. S03. Based on the data obtained in step S02 and the interference magnetic field compensation model of the geomagnetic vector measurement system, the error model equation set is obtained; S04. Solve for the parameters in the error model equations and use the solved parameters to compensate for the magnetic interference field of the geomagnetic vector measurement system; In step S01, the interference magnetic field compensation model is constructed according to the following formula: in, These are the measured values ​​from the triaxial magnetic field sensor that require compensation. for The three components on the x, y, and z axes , Represents permanent magnet magnetic field and , They are respectively The three components on the x, y, and z axes; The induced magnetic field is represented as follows, and since the induced magnetic field is determined by the external background magnetic field, the induced magnetic field is represented as... That is: It is the induction coefficient matrix. for The various inductance coefficients in the data, , With in the subject i The induced magnetic field is related to the direction of the induced magnetic field, which is generated by the induced magnetic field in the body. j A magnetic field applied in the direction is generated; The eddy current magnetic field is represented by the following formula: Since the rate of change of the eddy current magnetic field is proportional to that of the external background magnetic field, the eddy current magnetic field is expressed as: That is, it can be expressed as: in, It is the true value of the background geomagnetic field component in the coordinate system of the triaxial magnetic field sensor. for The three components on the x, y, and z axes, It is the eddy current coefficient matrix. for The eddy current coefficients in the data, , With in the subject i The eddy current magnetic field is related to the direction of the eddy current magnetic field, which is generated by the eddy current magnetic field in the main body. j The field is generated by applying a field in a certain direction.

2. The compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil according to claim 1, characterized in that, The interference magnetic field compensation model is transformed to obtain the final interference magnetic field compensation model: in, Values ​​that change over time. Indicates the change value.

3. The compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil according to claim 2, characterized in that, The error model equations constructed in step S03 are as follows: ； ； in, N Indicates the number of measurement points. express The rate of change of the magnetic field with respect to time.

4. The compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil according to claim 3, characterized in that, In the error model equation system Rate of change of magnetic field with respect to time This is achieved by controlling the current in the three-dimensional Helmholtz coil.

5. The compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil according to any one of claims 1 to 4, characterized in that, In step S02, when the geomagnetic vector measurement system is placed in the central region of the three-dimensional Helmholtz coil, the three sensitive axes of the three-axis magnetic field sensor of the geomagnetic vector measurement system are aligned with the three orthogonal directions of the three-dimensional Helmholtz coil.

6. The compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil according to any one of claims 1 to 4, characterized in that, In step S02, when generating magnetic field data of different directions and magnitudes through the three-dimensional Helmholtz coil, the current sequence of the three-dimensional Helmholtz coil is controlled to generate different directions and amplitudes in the three-dimensional spherical involute. The three orthogonal coil current sequences are specifically obtained according to the following spherical involute equation: in, Indicates the radial direction of the involute. Indicates the involute development angle. Indicates the involute pressure angle; the current sequence will follow... and The sampling interval changes with the change. and Determines the rate of change of the magnetic field.

7. The compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil according to any one of claims 1 to 4, characterized in that, In step S04, the parameters are solved using the linear least squares method.

8. The compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil according to claim 7, characterized in that, In step S04, when solving for the parameters in the error model equation set, it is also necessary to determine whether the magnetic interference field of the geomagnetic vector measurement system compensated by the solved parameters meets the preset compensation requirements. If it does, the compensation ends; otherwise, return to step S02 until the preset compensation requirements are met.

9. A system for implementing the compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil as described in any one of claims 1 to 8, characterized in that, include: The measurement and control module is used to place the geomagnetic vector measurement system in the central region of the three-dimensional Helmholtz coil, and generate magnetic field data of different directions and magnitudes through the three-dimensional Helmholtz coil to acquire multiple sets of measurement data. The measurement data includes the output value of the triaxial magnetic field sensor, the true value generated by the three-dimensional Helmholtz coil, and the rate of change of the true value generated by the three-dimensional Helmholtz coil over time. The compensation module is used to obtain an error model equation set based on the data acquired by the measurement and control module and the interference magnetic field compensation model of the geomagnetic vector measurement system; and to solve the parameters in the error model equation set, and use the solved parameters to compensate the magnetic interference field of the geomagnetic vector measurement system. The interference magnetic field compensation model of the geomagnetic vector measurement system is constructed by dividing the magnetic interference source into permanent magnetic field, induced magnetic field and eddy current magnetic field. The geomagnetic vector measurement system includes a triaxial magnetic field sensor.

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