CN115524762A - Compensation method of geomagnetic vector measurement system based on three-dimensional Helmertz coil - Google Patents

Abstract

The invention discloses a method for compensating a geomagnetic vector measurement system based on a three-dimensional Helmertz coil. The steps include: S01. Constructing a compensation model for an interference magnetic field of the geomagnetic vector measurement system; S02. Placing the geomagnetic vector measurement system at the center of the three-dimensional Helmertz coil area, and generate magnetic field data in different directions and sizes through the three-dimensional Helmholtz coil, and obtain multiple sets of measurement data. The measurement data includes the output value of the three-axis magnetic field sensor, the true value generated by the three-dimensional Helmholtz coil and the three-dimensional Helm The rate of change of the true value produced by the Holtz coil over time; S03. According to the data obtained in step S02 and the disturbance magnetic field compensation model of the geomagnetic vector measurement system, the error model equations are obtained; S04. Solving the parameters in the error model equations, using the solution The obtained parameters compensate the magnetic interference field of the geomagnetic vector measurement system. The invention has the advantages of simple operation, low cost, high compensation precision, strong flexibility and the like.

Description

Compensation method of geomagnetic vector measurement system based on three-dimensional Helmertz coil

technical field

The invention relates to the technical field of geomagnetic vector measurement, in particular to a compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmertz coil.

Background technique

Geomagnetic vector measurements (north, vertical and easting components) have very important applications in many situations, such as geological surveys, autonomous underwater vehicles (AUV) navigation, unexploded ordnance detection (UXO), etc. The geomagnetic vector measurement system is mainly composed of a three-axis fluxgate magnetometer and an attitude measurement unit (such as inertial navigation). The three-axis magnetometer provides the projection of the geomagnetic field on the coordinates of the magnetometer, and the attitude measurement unit provides the attitude of the magnetometer. Measure the pose information provided by the element, and convert this vector to a geographic coordinate system.

There are three main types of error sources in geomagnetic vector measurement systems: magnetometer errors, misalignment errors between inertial coordinates and magnetometer coordinates, and magnetic interference errors caused by ferromagnetic materials. These errors can reach thousands of nT, so they must be calibrated 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 interference of ferromagnetic components around the magnetometer and other electrical equipment (such as inertial components, power circuit modules) and application platforms. The above-mentioned magnetic interference field can be divided into permanent field, induction field and eddy current field. Compared with the permanent magnetic field, the induction and eddy current field are more complex, especially the eddy current determined by the direction, amplitude and time-dependent changes of the earth's magnetic field. field. Therefore, the eddy current field cannot be ignored in the mobile geomagnetic vector measurement.

The essence of magnetic field disturbance compensation is to estimate the parameters of the compensation model and use these parameters to calculate the disturbance field. The magnetic interference field compensation of the geomagnetic vector measurement system mainly includes three key parts: (1) compensation model; (2) compensation strategy (or the construction process of the equation); (3) compensation parameter estimation, compensation model, compensation strategy and compensation parameters The estimation accuracy will directly affect the final compensation effect. For the correction and compensation of the geomagnetic vector measurement system, the following methods are usually used in the prior art:

1. Compensate the three-axis magnetometer based on the attitude rotation strategy, including three different attitude rotation strategies (symmetrical rotation, orthogonal rotation and random rotation) to construct equations to achieve compensation, because the selection of the measurement position is representative, and The entire pose space is covered, so the symmetric rotation strategy has the best compensation. However, this type of method requires a rotating geomagnetic vector measurement system, which may be sensitive to geomagnetic gradients and environmental geomagnetic interference.

2. The component compensation method of the geomagnetic vector measurement system based on the parallelepiped frame, but the rotation attitude provided by the parallelepiped frame is limited, which is not enough to construct the equation to accurately estimate the parameters, and because the magnetic sensor and the inertial navigation system must be deployed separately, the applicable scenarios are limited. limit.

3. The Lagrange multiplier method is used to estimate the error parameters in the component compensation of the geomagnetic field vector measurement to realize the compensation, but the eddy current field is not considered in the component compensation model.

To sum up, the correction and compensation effect of the geomagnetic vector measurement system in the prior art still needs to be improved and the application scenarios are limited. In addition, due to the distribution of measurement data in the attitude space (when the system is deployed in different attitudes), there are usually insufficient or insufficient Reasonable problems will also lead to possible multicollinearity problems, which will affect the final compensation results. At the same time, the compensation methods in the prior art usually need to rely on the rotation of the system in the geomagnetic field, while the geomagnetic field should remain constant and the system should be different Therefore, the compensation process is not only sensitive to the gradient of the geomagnetic field, but also sensitive to environmental geomagnetic interference, and it is difficult to meet the above requirements in practical applications.

Contents of the invention

The technical problem to be solved by the present invention is: aiming at the technical problems existing in the prior art, the present invention provides a geomagnetic vector sensor based on a three-dimensional Helmertz coil that realizes simple operation, low cost, high compensation accuracy, good effect, and strong flexibility. Measurement system compensation method.

In order to solve the problems of the technologies described above, the technical solution proposed by the present invention is:

A compensation method for a geomagnetic vector measurement system based on a three-dimensional Helmertz coil, the steps comprising:

S01 divides the disturbance magnetic field into a permanent magnetic field, an induced magnetic field and an eddy current magnetic field, and constructs a disturbance magnetic field compensation model of a geomagnetic vector measurement system, which includes a three-axis magnetic field sensor;

S02. Place the geomagnetic vector measurement system in the central area of the three-dimensional Helmertz coil, and generate magnetic field data in different directions and sizes through the three-dimensional Helmertz coil, and obtain multiple sets of measurement data, including three-axis The output value of the magnetic field sensor, the true value produced by the three-dimensional Helmholtz coil, and the rate of change of the true value produced by the three-dimensional Helmholtz coil over time;

S03. According to the data obtained in step S02 and the magnetic field compensation model of the geomagnetic vector measurement system, an error model equation group is obtained;

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

Further, in the step S01, the disturbance magnetic field compensation model is constructed according to the following formula:

H_px,H_py,H_pz分别为H_p在x、y、z轴上的三个分量；A_iH₀表示感应磁场，且根据感应磁场由外部背景磁场决定，将感应磁场表示为H_i，即为：Among them, H _m is the measured value of the three-axis magnetic field sensor to be compensated, H _mx , H _my , H _mz are the three components of H _m on the x, y, and z axes H _mx , H _my , H _mz , H _p represents the permanent magnetic field and

H _px , H _py , and H _pz are the three components of H _p on the x, y, and z axes respectively; A _i H ₀ represents the induced magnetic field, and according to the induced magnetic field is determined by the external background magnetic field, the induced magnetic field is expressed as H _i , which is:

A _i is the inductance matrix, a _ij is each inductance coefficient in A _i , i, j=x, y, z, A _i is related to the induced magnetic field in the direction of the subject i, and the induced magnetic field is generated by the subject j A magnetic field applied in the direction produces;

表示涡流磁场，且根据涡流磁场与外部背景磁场的变化率成正比，将涡流磁场表示为H_e，即表示为：

Represents the eddy current magnetic field, and according to the fact that the eddy current magnetic field is proportional to the rate of change of the external background magnetic field, the _eddy current magnetic field is expressed as He , which is expressed as:

Among them, H ₀ is the true value of the background geomagnetic field component in the coordinates of the three-axis magnetic field sensor, H _0x , H _0y , H _0z are the three components of H ₀ on the x, y, and z axes, A _e is the eddy current coefficient matrix, b _ij is each eddy current coefficient in A _e , i, j=x, y, z, A _e is related to the eddy current magnetic field in the direction of the body i, and the eddy current magnetic field is generated by the field applied in the direction of the body j .

Further, transform the disturbance magnetic field compensation model to obtain the final disturbance magnetic field compensation model as:

Among them, Δt is the time change value, and Δ represents the change value.

Further, the error model equations constructed in the step S03 are:

Wherein, N represents the number of measurement points, and dH ₀ /dt represents the change rate of the H ₀ magnetic field with respect to time.

Further, the rate of change dH ₀ /dt of the H ₀ magnetic field with respect to time in the error model equations is obtained by controlling the current of the three-dimensional Helmertz coil.

Further, in the step S02, when the geomagnetic vector measurement system is placed in the central area of the three-dimensional Helmhertz coil, the directions of the three sensitive axes of the three-axis magnetic field sensor of the geomagnetic vector measurement system and the directions of the three-dimensional Helmhertz coil Three orthogonal directions remain aligned.

Further, in the step S02, when magnetic field data of different directions and sizes are generated by the three-dimensional Helmertz coil, the current sequence of the three-dimensional Helmertz coil is controlled to generate a three-dimensional spherical involute With different directions and amplitudes, three orthogonal coil current sequences are obtained specifically according to the following spherical involute equation:

Among them, R represents the radial direction of the involute, θ represents the expansion angle of the involute, and α represents the pressure angle of the involute. The current sequence will change with the change of θ and α, and the sampling interval Δθ and Δα will determine the rate of change of the magnetic field.

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

Further, in the step S04, when solving the parameters in the error model equations, it also includes judging whether the magnetic interference field of the geomagnetic vector measurement system is compensated by using the solved parameters to meet the preset compensation requirements, and if so, the compensation End, otherwise return to step S02 until the preset compensation requirements are met.

A compensation system for a geomagnetic vector measurement system based on a three-dimensional Helmertz coil, comprising:

The measurement control module is used to place the geomagnetic vector measurement system in the central area of the three-dimensional Helmertz coil, and generate magnetic field data in different directions and sizes through the three-dimensional Helmertz coil, and obtain multiple sets of measurement data. The measurement The data includes 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 over time;

The compensation module is used to obtain the error model equations according to the data obtained by the measurement control module and the magnetic field compensation model of the geomagnetic vector measurement system; and solve the parameters in the error model equations, and use the solved parameters to compensate the geomagnetic vector The magnetic interference field of the 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, and the geomagnetic vector measurement system includes a three-axis magnetic field sensor.

Compared with the prior art, the present invention has the advantages of:

1. The present invention establishes a compensation model for disturbance magnetic field components including permanent magnetic field, induced magnetic field and eddy current magnetic field, and places the geomagnetic vector measurement system in the center of the homogeneous area of the three-dimensional Helmertz coil, and uses the coil to generate different amplitudes, different directions, and different changes By solving the equations to estimate the error parameters, enough representative data can be quickly generated to construct the equations, which can greatly reduce the measurement error of the geomagnetic vector measurement system.

2. The present invention can conveniently obtain sufficient and reasonable data sets by controlling the coil current, and quickly generate sufficient representative data to construct equations. Not only is the compensation simple and cost-effective, but also there is no need to construct compensation equations through rotating platforms. By using The magnetic field data generated by the three-dimensional Helmholtz coil can try to ensure that there is no complex collinearity in the equation, so that the error parameters can be estimated more accurately.

3. By using the three-dimensional Helmholtz coil, the present invention can perform flexible compensation according to different application scenarios, while ensuring good compensation accuracy, compared with the traditional rotation strategy, the compensation can be completed in a shorter time.

Description of drawings

Fig. 1 is a schematic diagram of the implementation flow of the compensation method of the geomagnetic vector measurement system based on the three-dimensional Helmertz coil in this embodiment.

Fig. 2 is a schematic diagram of the structure and principle of the geomagnetic vector measurement system in this embodiment.

Fig. 3 is a schematic diagram of a detailed implementation process for implementing geomagnetic vector measurement system compensation in a specific application embodiment of the present invention.

Fig. 4 is a schematic diagram of the principle of partial current generation constraints of three orthogonal coils in a specific application embodiment.

Fig. 5 is a schematic diagram of partial alternating current curves of three orthogonal coils obtained in a specific application embodiment.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

As shown in Figure 1, the steps of the compensation method for the geomagnetic vector measurement system based on the three-dimensional Helmertz coil in this embodiment include:

S01. Divide the disturbance magnetic field into permanent magnetic field, induction magnetic field and eddy current magnetic field, and construct the disturbance magnetic field compensation model of the geomagnetic vector measurement system. The geomagnetic vector measurement system is shown in Figure 2, including the high-precision optical fiber inertial navigation system INS and the three-axis magnetic field sensor (Specifically, a three-axis fluxgate magnetometer);

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

S03. According to the data obtained in step S02 and the geomagnetic vector measurement system disturbance magnetic field compensation model, an error model equation group is obtained;

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

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

H _p =[H _px H _py H _pz ] ^T (1)

Among them, H _p is the permanent magnetic interference, H _px , H _py , and H _pz are the three components of H _p on the x, y, and z axes.

The induced magnetic field H _i is determined according to the external background magnetic field, which can be expressed as:

Among them, A _i is the inductance matrix, a _ij is each inductance coefficient in A _i , i, j=x, y, z, A _i is related to the induced magnetic field in the direction of the subject i, and the induced magnetic field is generated by the subject j A magnetic field applied in the direction produces.

The _eddy current magnetic field He is proportional to the rate of change of the external background magnetic field, which can be expressed as:

Among them, A _e is the eddy current coefficient matrix, b _ij is each eddy current coefficient in A _e , i, j=x, y, z, A _e is related to the eddy current magnetic field in the direction of the main body i, and the eddy current magnetic field is generated by the main body j A field applied in the direction produces.

In step S01 of this embodiment, the mathematical model of the three-axis magnetic field sensor considering the magnetic field interference is specifically constructed based on the above formulas (1) to (3), that is, the interference magnetic field compensation model:

Among them, H _m is the measured value of the three-axis magnetometer to be compensated, H _mx , H _my , H _mz are the three components of H _m on the x, y, and z axes H _mx , H _my , H _mz , H ₀ is the true value of the background geomagnetic field component in the coordinates of the three-axis magnetometer, and H _0x , H _0y , and H _0z are the three components of H ₀ on the x, y, and z axes.

可表示为如下式(5)，本实施例具体利用三维亥姆霍兹线圈，通过控制三维亥姆赫兹线圈的电流获取该微分值

可以实现该微分值

的精确获取。The differential of the true value _H0 of the above-mentioned background geomagnetic field component with respect to time

It can be expressed as the following formula (5). In this embodiment, a three-dimensional Helmholtz coil is specifically used to obtain the differential value by controlling the current of the three-dimensional Helmholtz coil

It is possible to achieve this differential value

accurate acquisition.

Since it is unknown in the actual measurement process, dH ₀ /dt in formula (4) can be replaced by dH _m /dt, and the influence of this difference is very small.

Further combined with formula (5), the mathematical model of the above-mentioned three-axis magnetic sensor considering magnetic field interference is transformed, and the final interference magnetic field compensation model of the geomagnetic vector measurement system is obtained as:

Among them, Δt is the time change value, and Δ represents the change value.

It can be known from the above that 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 the measurement data samples H _mx , H _my , H _mz , combined with the reference true values H _0x , H _0y , H _0z provided by the 3D Helmholtz coil, they can be obtained by substituting into formulas (6)～(8) Three equations. According to the above-mentioned interference magnetic field compensation model in a specific application embodiment, at least seven measured values need to be collected to form a plurality of equations, and parameter estimation can be realized by solving the equations subsequently. Preferably, each unknown parameter can be estimated more accurately by obtaining a sufficient number of representative data sets, thereby ensuring compensation accuracy.

In step S02 of this embodiment, the geomagnetic vector measurement system is placed in the central area of the three-dimensional Helmholtz coil, and the three-dimensional Helmholtz coil is used to generate magnetic field data of different directions and sizes, and the error model equations are constructed to form an error model equation group, and then the model is estimated There are 21 unknown parameters in it. This embodiment specifically uses a 3D Helmholtz coil, which consists of three completely orthogonal coils, and the coils are driven by current, and each coil has a corresponding current controller. By controlling the current flowing through the coil, it can Any magnetic field component is generated in the central uniform area of the three-dimensional coil, and a high-precision magnetic field uniform area of any size can be generated through the three-dimensional Helmholtz coil. In this embodiment, compensation is realized by combining a three-dimensional Helmholtz coil, and adaptive and flexible compensation can be performed according to different application scenarios. For example, the gradient of the background magnetic field can be simulated. Not only is the compensation simple and convenient, but it can also ensure good compensation accuracy.

Preferably, when the geomagnetic vector measurement system is placed in the central area of the three-dimensional Helmertz coil in step S02, specifically, the directions of the three sensitive axes of the three-axis magnetic field sensor of the geomagnetic vector measurement system are aligned with the three positive axes of the three-dimensional Helmhertz coil. The intersection direction remains aligned.

Preferably, when magnetic field data of different directions and sizes are generated by the three-dimensional Helmertz coil, specifically by controlling the current sequence of the three-dimensional Helmertz coil to generate different directions and amplitudes in the three-dimensional spherical involute, the three The orthogonal coil current sequence is specifically obtained according to the following spherical involute equation:

Among them, R represents the radial direction of the involute, θ represents the expansion angle of the involute, and α represents the pressure angle of the involute. The current sequence will change with the change of θ and α, and the sampling interval Δθ and Δα will determine the rate of change of the magnetic field.

In a specific application embodiment, different directions and amplitudes are generated in the three-dimensional spherical involute as shown in FIG. 4 . Part of the current curves are shown in Fig. 5 according to the currents generating three orthogonal coils in a three-dimensional spherical involute.

基于多组测量数据以及如式(6)～(8)所示的模型，即可构建出模型方程组为：After the magnetic field components with different amplitudes and directions are generated in the uniform area of the three-dimensional Helmholtz coil, multiple sets of measurement data can be obtained after measurement, including the output value H _m of the three-axis magnetic field sensor, the true value generated by the three-dimensional Helmholtz coil The value H ₀ and the rate of change of the true value produced by the three-dimensional Helmholtz coil with time

Based on multiple sets of measurement data and the models shown in equations (6)-(8), the model equations can be constructed as follows:

Wherein, N represents the number of measured points, and dH ₀ /dt represents the rate of change of the H ₀ magnetic field with respect to time.

Further by solving the linear equations in the above formula (9), 21 unknown parameters of the permanent magnet, induction and eddy current fields can be estimated. After all 21 unknown parameters are accurately estimated, the magnetic interference can be calculated according to the error parameters Field, get the expected true value of the geomagnetic vector, and realize the magnetic interference field compensation of the geomagnetic vector measurement system. Preferably, the linear least square method can be used to solve the parameters. Since the magnetic field data generated by the three-dimensional Helmholtz coil can ensure that there is no complex collinearity in the equation, the error parameter can be accurately and quickly estimated by using the linear least square method. The solution efficiency and accuracy can be further improved.

In step S04 of this embodiment, when the parameters in the error model equations are solved, it also includes judging whether the magnetic interference field of the geomagnetic vector measurement system using the solved parameters to compensate the magnetic interference field satisfies the preset compensation requirements, and if so, the compensation ends, otherwise returns Step S02, until the preset compensation requirement is met. After multiple iterations, the required compensation precision can be accurately achieved finally.

As shown in Figure 3, in a specific application embodiment, the geomagnetic vector measurement system is first placed on the non-magnetic platform at the center of the three-dimensional Helmholtz coil (as shown in Figure 2), and then the uniform area of the coil is generated with different The magnetic field components of the amplitude and direction are used to construct the model error equation, as shown in formula (9); then the least squares algorithm is sampled to estimate each unknown parameter, which is used to compensate the geomagnetic vector measurement system. After each compensation, it is judged whether it satisfies Compensation accuracy, if not satisfied, repeat the above steps until the compensation accuracy requirements are finally met. In this embodiment, the geomagnetic vector measurement system is placed in the center of the homogeneous area of the three-dimensional Helmertz coil, and the coils are used to generate magnetic fields with different amplitudes, directions, and rates of change to establish a system of error parameter equations, so that no Relying on the attitude of the traditional rotation measurement system to establish a system of equations not only achieves simple operation and low cost, but also enables adaptive and flexible compensation according to different application scenarios, while ensuring good compensation accuracy.

In the component compensation of the geomagnetic vector measurement system, the present invention establishes a compensation model integrating the permanent magnetic field, the induced magnetic field and the eddy current magnetic field, and simultaneously uses a three-dimensional Helmholtz coil to generate different vector magnetic fields, and places the geomagnetic vector measurement system in a three-dimensional In the central area of the Helmholtz coil, the error equations are constructed based on the compensation model and multiple sets of measurement data. By solving the equations to estimate the error parameters, enough representative data can be quickly generated to construct the equations, making the compensation efficient and accurate. , can greatly reduce the measurement error of the geomagnetic vector measurement system, and there is no need to construct a compensation equation through the rotating platform. In addition, the present invention can also be applied to various scenarios where the geomagnetic vector measurement system is carried on platforms such as autonomous underwater vehicles or unmanned aerial vehicles to perform geomagnetic vector measurement. When the three-dimensional Helmholtz coil is large enough, the interference of the platform Sources can also be considered together with sources of interference in the measurement system itself.

In order to verify the effectiveness of the above-mentioned method of the present invention, adopt the method of the present invention to carry out compensation test in concrete application embodiment, experimental device as shown in Figure 2, comprises: 1) geomagnetic field vector measurement system, comprises high-precision optical fiber inertial navigation system ( INS, provides attitude information) and Mag-13 three-axis fluxgate magnetometer (measures magnetic components); 2) 3D Helmholtz coils (creates arbitrary magnetic field components); 3) 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 less than 1nT after calibration. The inertial navigation system has also been calibrated in the laboratory using a turntable with three degrees of freedom.

According to the Mag-13 magnetometer manual, the main performance indicators are as follows: Magnetic field range of each sensor axis: 100uT; Quadrature error: <±0.1°; Offset: <5nT; Noise: <5pTrms/Hz-1Hz 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 area of 260cm3; quadrature error: <±0.01°;

In this embodiment, the specific steps for realizing the compensation of the geomagnetic vector measurement system are as follows:

① Place the geomagnetic vector measurement system at the center of the three-dimensional Helmholtz coil, as shown in Figure 2.

②The three-dimensional Helmholtz coil generates a magnetic field under the excitation of the pre-defined coil current, and starts to record the output value H _m of the three-axis magnetic field sensor and the true value H ₀ generated by the three-dimensional Helmholtz coil, as well as the change of H ₀ with time Some of the data obtained are shown in Table 1.

③According to the obtained data and formula (9), the following equations are obtained:

④ Solve the above linear equations, estimate 21 unknown parameters of permanent magnet, induction and eddy current field, and judge whether the compensation accuracy requirements are met. If so, the compensation ends. Otherwise, return to step ② until the requirements are met. When all 21 unknown parameters are accurately estimated, the error parameter can be used to compensate the magnetic interference field of the geomagnetic vector measurement system.

Table 1: Measurement data of some three-axis magnetic field sensors and true data generated by coils

As shown in Table 2, after compensation using the proposed method, the root mean square errors of the northern, vertical, eastern components 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.

Table 2: Interference magnetic field compensation effect (nT)

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 Helmertz coil of the present invention can effectively eliminate the interference magnetic field around the magnetometer, and effectively improve the accuracy and reliability of the geomagnetic vector measurement.

This embodiment also provides a geomagnetic vector measurement system compensation system based on a three-dimensional Helmertz coil, including:

The measurement control module is used to place the geomagnetic vector measurement system in the central area of the three-dimensional Helmertz coil, and generate magnetic field data in different directions and sizes through the three-dimensional Helmertz coil, and obtain multiple sets of measurement data. The measurement data includes three-axis The output value of the 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;

The compensation module is used to obtain the error model equations according to the data obtained by the measurement control module and the disturbance magnetic field compensation model of the geomagnetic vector measurement system; and solve the parameters in the error model equations, and use the solved parameters to compensate the magnetic field of the geomagnetic vector measurement system. Interference field, geomagnetic vector measurement system The interference magnetic field compensation model 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 three-axis magnetic field sensor.

The compensation system of the geomagnetic vector measurement system based on the three-dimensional Helmertz coil in this embodiment corresponds to the above compensation method for the geomagnetic vector measurement system based on the three-dimensional Helmertz coil, and will not be repeated here.

The present invention establishes a compensation model for interference magnetic field components including permanent magnetic field, induced magnetic field and eddy current magnetic field, uses three-dimensional Helmholtz coils to generate different vector magnetic fields and then constructs error parameter equations, and can conveniently obtain sufficient and reasonable data by controlling the coil current Set, quickly generate enough representative data to construct the equation, without the need to construct the compensation equation through the rotating platform, and by using the magnetic field data generated by the three-dimensional Helmholtz coil, it can try to ensure that the equation does not have complex collinearity, so that it can be estimated more accurately Error parameters, while using three-dimensional Helmholtz coils, can also be flexibly compensated according to different application scenarios. Not only is the compensation simple, the cost is low, and the compensation accuracy is high. Compared with the traditional rotation strategy, it can be realized in a shorter time. Complete compensation.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims (10)

1. A compensation method of a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil is characterized by comprising the following steps of:

s01, dividing an interference magnetic field into a permanent magnetic field, an induction magnetic field and an eddy magnetic field, and constructing an interference magnetic field compensation model of a geomagnetic vector measurement system, wherein the geomagnetic vector measurement system comprises a three-axis magnetic field sensor;

s02, placing a geomagnetic vector measurement system in a central region of a three-dimensional Helmholtz coil, generating magnetic field data in different directions and different sizes through the three-dimensional Helmholtz coil, and acquiring multiple groups of measurement data, wherein the measurement data comprise an output value of a three-axis magnetic field sensor, a true value generated by the three-dimensional Helmholtz coil and a change rate of the true value generated by the three-dimensional Helmholtz coil along with time;

s03, obtaining an error model equation set according to the data obtained in the step S02 and the interference magnetic field compensation model of the geomagnetic vector measurement system;

and S04, solving parameters in the error model equation set, and compensating the magnetic interference field of the geomagnetic vector measurement system by using the solved parameters.

2. The method for compensating a three-dimensional Helmholtz coil-based geomagnetic vector measurement system according to claim 1, wherein in the step S01, the disturbing magnetic field compensation model is constructed according to the following formula:

wherein H _m Is the measured value of the three-axis magnetic field sensor requiring compensation, H _mx ,H _my ,H _mz Is H _m Three components H in the x, y, z axes _mx ,H _my ,H _mz ，H _p Represents a permanent magnetic field and H _p ＝[H _px H _py H _pz ] ^T ，H _px ,H _py ,H _pz Are respectively H _p At x,Three components on the y and z axes; a. The _i H ₀ Represents an induced magnetic field and is determined by an external background magnetic field according to the induced magnetic field, and represents the induced magnetic field as H _i Namely:

A _i is an inductance matrix, a _ij Is A _i I, j = x, y, z, a _i Relating to an induced magnetic field in a direction of a body i, the induced magnetic field being generated by a magnetic field applied in a direction of a body j;

representing the eddy magnetic field and representing it as H, in proportion to the rate of change of the eddy magnetic field and the external background magnetic field _e I.e. expressed as:

wherein H ₀ Is the true value, H, of the background geomagnetic field component in the three-axis magnetic field sensor coordinates _0x ,H _0y ,H _0z Is H ₀ Three components in the x, y, z axes, A _e Is a matrix of eddy current coefficients, b _ij Is A _e Each eddy current coefficient of (1), i, j = x, y, z, a _e Related to the eddy current magnetic field in the direction of the body i, which is generated by the field applied in the direction of the body j.

3. The compensation method for the three-dimensional Helmholtz coil-based geomagnetic vector measurement system, according to claim 2, wherein the disturbing magnetic field compensation model is transformed to obtain a final disturbing magnetic field compensation model:

H _mz ＝H _0z +H _pz +a _zx H _0x +a _zy H _0y +a _zz H _0z +b _zx (ΔH _0x /Δt)+b _zy (ΔH _0y /Δt)+b _zz (ΔH _0z /Δt)

where Δ t is a time variation value, and Δ represents a variation value.

4. The method for compensating a three-dimensional Helmholtz coil-based geomagnetic vector measurement system according to claim 3, wherein the error model equation set constructed in the step S03 is as follows:

wherein N represents the number of measurement points, dH ₀ (dt represents H) ₀ The rate of change of the magnetic field with respect to time.

5. A three-dimensional Helmholtz-coil-based compensation method for a geomagnetic vector measurement system according to claim 4, wherein H in the error model equation set ₀ Rate of change dH of magnetic field with respect to time ₀ The/dt is obtained by controlling the current of the three-dimensional Helmholtz coil.

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

7. A compensation method for a three-dimensional Helmholtz coil-based geomagnetic vector measurement system according to any one of claims 1 to 5, wherein in the step S02, when the three-dimensional Helmholtz coil generates magnetic field data with different directions and different sizes, by controlling a current sequence of the three-dimensional Helmholtz coil, different directions and different amplitudes are generated in a three-dimensional spherical involute, and three orthogonal coil current sequences are obtained according to the following spherical involute equations:

where R represents the involute radial direction, θ represents the involute flare angle, α represents the involute pressure angle, the current sequence will vary with the variation of θ and α, and the sampling intervals Δ θ and Δ α determine the magnetic field rate of change.

8. The method for compensating for a three-dimensional Helmholtz coil-based geomagnetic vector measurement system according to any one of claims 1 to 5, wherein in the step S04, a linear least square method is adopted for parameter solution.

9. A method for compensating a three-dimensional helmholtz coil-based geomagnetic vector measurement system, as recited in claim 8, wherein in step S04, when the parameters in the error model equation set are solved, the method further comprises determining whether the magnetic interference field of the geomagnetic vector measurement system compensated by the solved parameters satisfies a predetermined compensation requirement, if so, the compensation is ended, otherwise, the method returns to step S02 until the predetermined compensation requirement is satisfied.

10. The utility model provides a earth magnetism vector measurement system compensating system based on three-dimensional helmholtz coil which characterized in that includes:

the measurement control module is used for placing a geomagnetic vector measurement system in a central area of the three-dimensional Helmholtz coil, generating magnetic field data in different directions and different sizes through the three-dimensional Helmholtz coil, and acquiring multiple groups of measurement data, wherein the measurement data comprise an output value of the three-axis magnetic field sensor, a true value generated by the three-dimensional Helmholtz coil and a time-dependent change rate of the true value generated by the three-dimensional Helmholtz coil;

the compensation module is used for obtaining an error model equation set according to the data acquired by the measurement control module and an interference magnetic field compensation model of the geomagnetic vector measurement system; and solving parameters in the error model equation set, and compensating a magnetic interference field of a geomagnetic vector measurement system by using the solved parameters, wherein the geomagnetic vector measurement system interference magnetic field compensation model is constructed by dividing a magnetic interference source into a permanent magnetic field, an induction magnetic field and an eddy magnetic field, and the geomagnetic vector measurement system comprises a three-axis magnetic field sensor.

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