CN115524762A - Geomagnetic vector measurement system compensation method based on three-dimensional Helmholtz coil - Google Patents
Geomagnetic vector measurement system compensation method based on three-dimensional Helmholtz coil Download PDFInfo
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Abstract
The invention discloses a compensation method of a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil, which comprises the following steps of: s01, constructing an interference magnetic field compensation model of a geomagnetic vector measurement system; s02, placing a geomagnetic vector measurement system in a central area 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 time-dependent change rate of the true value generated by the three-dimensional Helmholtz coil; s03, obtaining an error model equation set according to the data obtained in the step S02 and an 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. The invention has the advantages of simple realization and operation, low cost, high compensation precision, strong flexibility and the like.
Description
Technical Field
The invention relates to the technical field of geomagnetic vector measurement, in particular to a compensation method of a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil.
Background
Geomagnetic vector measurements (north, vertical, and east components) have important applications in many situations, such as geological surveys, autonomous Underwater Vehicle (AUV) navigation, unexplosive explosive detection (UXO), and so on. The geomagnetic vector measurement system mainly comprises a triaxial fluxgate magnetometer and an attitude measurement unit (such as inertial navigation), wherein the triaxial magnetometer provides projection of a geomagnetic field on the coordinate of the magnetometer, the attitude measurement unit provides the attitude of the magnetometer, and the vector is converted into a geographic coordinate system by utilizing attitude information provided by an attitude measurement element.
The error sources in the geomagnetic vector measurement system mainly include three types: magnetometer errors, misalignment errors between inertial and magnetometer coordinates, and magnetic interference errors caused by ferromagnetic materials, which can reach thousands of nT, make it necessary to calibrate and compensate the geomagnetic vector measurement system, among which the magnetic interference errors caused by ferromagnetic materials are the most serious. The disturbing magnetic field is closely related to the interference of ferromagnetic parts and other electrical devices (such as inertial elements, power circuit modules) around the magnetometer and the application platform. The magnetic interference fields can be divided into permanent, induced and eddy fields, wherein the induced and eddy fields are more complex than the permanent magnetic field, especially the eddy field determined by the direction, amplitude and its variation with time of the earth's magnetic field. Therefore, eddy fields cannot be ignored in the measurement of the mobile geomagnetic vector.
The essence of the magnetic field disturbance compensation is to estimate the parameters of the compensation model and to use these parameters to calculate the disturbance field. The magnetic interference field compensation of the geomagnetic vector measurement system mainly comprises three key parts: (1) a compensation model; (2) a compensation strategy (or construction process of the equation); (3) The compensation parameter estimation, the compensation model, the compensation strategy and the accuracy of the compensation parameter estimation will directly affect the final compensation effect. For the problem of correction and compensation of a geomagnetic vector measurement system, the prior art generally adopts the following methods:
1. compensating the triaxial magnetometer based on an attitude rotation strategy, wherein the compensation effect of the symmetrical rotation strategy is the best as the selection of the measurement position is representative and covers the whole attitude space. However, this type of method requires a rotating geomagnetic vector measurement system, and has a problem of sensitivity to geomagnetic field gradients and environmental geomagnetic interference.
2. The component compensation method of the geomagnetic vector measurement system based on the parallelepiped frame is limited in rotation posture provided by the parallelepiped frame, insufficient for constructing an equation to accurately estimate parameters, and limited in applicable scene due to the fact that a magnetic sensor and an inertial navigation system must be separately deployed.
3. And estimating error parameters in the compensation of the geomagnetic field vector measurement component by adopting a Lagrange multiplier method to realize compensation, but not considering the eddy current field in a component compensation model.
In summary, the effect of the correction compensation for the geomagnetic vector measurement system in the prior art still needs to be improved and the application scenarios are limited, and in addition, because the distribution of the measurement data in the attitude space (when the system is deployed in different attitudes) usually has a problem of insufficiency or unreasonable, a multiple collinearity problem may occur, which may affect the final compensation result, and meanwhile, the compensation method in the prior art usually needs to rely on the rotation of the system in the geomagnetic field, while the geomagnetic field should be kept constant and the system is deployed in different attitudes to obtain different magnetic field component outputs, so that the compensation process is not only sensitive to the geomagnetic field gradient, but also sensitive to the environmental geomagnetic interference, and the actual application is difficult to meet the above requirements.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: aiming at the technical problems in the prior art, the invention provides the compensation method of the geomagnetic vector measurement system based on the three-dimensional Helmholtz coil, which is simple to operate, low in cost, high in compensation precision, good in effect and strong in flexibility.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a compensation method of a geomagnetic vector measurement system based on a three-dimensional Helmholtz coil comprises the following steps:
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 area 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 time-dependent change rate of the true value generated by the three-dimensional Helmholtz coil;
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 a magnetic interference field of the geomagnetic vector measurement system by using the solved parameters.
Further, in 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 px ,H py ,H pz are each H p Three components in the x, y, 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;
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 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.
Further, the disturbing magnetic field compensation model is transformed to obtain a final disturbing magnetic field compensation model:
where Δ t is a time variation value, and Δ represents a variation value.
Further, the error model equation set constructed in step S03 is:
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.
Further, 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.
Further, in step S02, when the geomagnetic vector measurement system is placed in the central region of the three-dimensional helmholtz coil, three sensitive axis directions of the three-axis magnetic field sensor of the geomagnetic vector measurement system are aligned with three orthogonal directions of the three-dimensional helmholtz coil.
Further, in step S02, when the three-dimensional helmholtz coil generates magnetic field data in different directions and different magnitudes, different directions and amplitudes are generated in the three-dimensional spherical involute by controlling a current sequence of the three-dimensional helmholtz coil, and the three orthogonal coil current sequences are specifically obtained according to the following spherical involute equation:
where R represents the radial direction of the involute, θ represents the involute flare angle, α represents the involute pressure angle, the current sequence will change with the change in θ and α, and the sampling intervals Δ θ and Δ α will determine the magnetic field rate of change.
Further, in step S04, a linear least square method is used to solve the parameters.
Further, in the step S04, when the parameters in the error model equation set are solved, the method further includes determining whether the magnetic interference field of the geomagnetic vector measurement system compensated by the solved parameters meets a preset compensation requirement, if so, the compensation is finished, otherwise, the method returns to the step S02 until the preset compensation requirement is met.
A geomagnetic vector measurement system compensation system based on a three-dimensional Helmholtz coil comprises:
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 using the solved parameters to compensate a magnetic interference field of a geomagnetic vector measurement system, 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.
Compared with the prior art, the invention has the advantages that:
1. according to the invention, by establishing an interference magnetic field component compensation model containing a permanent magnetic field, an induction magnetic field and an eddy magnetic field, arranging a geomagnetic vector measurement system at the center of a uniform region of a three-dimensional Helmholtz coil, establishing an equation set of error parameters by utilizing the coils to generate magnetic fields with different amplitudes, different directions and different change rates, and performing error parameter estimation by solving the equation set, enough representative data can be quickly generated to construct an equation, so that the measurement error of the geomagnetic vector measurement system can be greatly reduced.
2. According to the invention, a sufficient and reasonable data set can be conveniently obtained by controlling the current of the coil, sufficient representative data is rapidly generated to construct an equation, the compensation is simple to implement and low in cost, a compensation equation does not need to be constructed 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 as much as possible, so that the error parameters can be more accurately estimated.
3. According to the invention, by using the three-dimensional Helmholtz coil, flexible compensation can be performed according to different application scenes, good compensation precision is ensured, and compensation can be completed in a shorter time compared with the traditional rotation strategy.
Drawings
Fig. 1 is a schematic flow chart illustrating an implementation of the compensation method of the geomagnetic vector measurement system based on a three-dimensional helmholtz coil in this embodiment.
Fig. 2 is a schematic view of the structural principle of the geomagnetic vector measurement system in the present embodiment.
Fig. 3 is a schematic diagram of a detailed implementation flow of compensation of a geomagnetic vector measurement system in an embodiment of the present invention.
Fig. 4 is a schematic diagram of the current generation constraints of portions of three orthogonal coils in a specific application embodiment.
Fig. 5 is a partial ac current curve diagram of three orthogonal coils obtained in a specific application example.
Detailed Description
The invention is further described below with reference to the drawings and the specific preferred embodiments, without thereby limiting the scope of protection of the invention.
As shown in fig. 1, the steps of the compensation method for the geomagnetic vector measurement system based on the three-dimensional helmholtz coil in this embodiment include:
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 high-precision optical fiber inertial navigation system INS and a triaxial magnetic field sensor (specifically a triaxial fluxgate magnetometer) as shown in figure 2;
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 time-dependent change rate of the true value generated by the three-dimensional Helmholtz coil;
s03, obtaining an error model equation set according to the data obtained in the step S02 and an 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.
The interference sources mainly come from ferromagnetic parts and other electrical devices in the system, such as an inertial navigation system and a power module, and can be divided into a permanent magnetic field, an induced magnetic field and an eddy current magnetic field. The permanent magnetic field remains constant for a considerable time, which can be expressed as:
H p ＝[H px H py H pz ] T (1)
wherein H p Is a permanent magnetic interference, H px ,H py ,H pz Is H p Three components in the x, y, z axes.
Induced magnetic field H i Depending on the external background magnetic field, it can be expressed as:
wherein, A i Is an inductance matrix, a ij Is A i I, j = x, y, z, a i In relation to the induced magnetic field in the direction of the body i, the induced magnetic field is generated by a magnetic field applied in the direction of the body j.
Eddy magnetic field H e Proportional to the rate of change of the external background magnetic field, can be expressed as:
wherein, 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 In relation to the eddy current magnetic field in the direction of the body i, the eddy current magnetic field is generated by a field applied in the direction of the body j.
In step S01 of this embodiment, a mathematical model of the three-axis magnetic field sensor considering magnetic field interference, that is, an interference magnetic field compensation model, is constructed based on the above equations (1) to (3):
wherein H m Is the measurement of the three-axis magnetometer to be compensated, H mx ,H my ,H mz Is H m Three components H in the x, y, z axes mx ,H my ,H mz ，H 0 Is the true value, H, of the background geomagnetic field component in the coordinates of the magnetometer in three axes 0x ,H 0y ,H 0z Is H 0 Three components in the x, y, z axes.
True value H of above background geomagnetic field component 0 Differentiation with respect to time
This embodiment, which may be expressed as the following equation (5), specifically utilizes a three-dimensional helmholtz coil, and obtains the differential value by controlling the current of the three-dimensional helmholtz coil
The differential value can be realized
Accurate acquisition of the image.
Since it is not known in the actual measurement process, dH in equation (4) can be expressed 0 (iv) dH for dt m The effect of this difference is very small/dt.
Further combining formula (5), transforming the mathematical model of the three-axis magnetic sensor considering the magnetic field interference to obtain a final interference magnetic field compensation model of the geomagnetic vector measurement system, wherein the model is as follows:
where Δ t is a time variation value, and Δ represents a variation value.
As can be seen from the above, there are 21 (H) in the model px ,H py ,H pz 、a ij i,j＝x,y,z、b ij i, j = x, y, z) unknown parameters need to be estimated. When the system collects the measurement data sample H mx ,H my ,H mz In combination with a reference true value H provided by a 3D helmholtz coil 0x ,H 0y ,H 0z And substituting the equations (6) to (8) to obtain three equations. In a specific application embodiment, at least 7 measurement values are collected to form a plurality of equation sets according to the disturbing magnetic field compensation model,parameter estimation can be achieved subsequently by solving the system of equations. Preferably, by acquiring a sufficient number of representative data sets, unknown parameters can be estimated more accurately, thereby ensuring compensation accuracy.
In step S02 of this embodiment, a geomagnetic vector measurement system is placed in a central region of a three-dimensional helmholtz coil, the three-dimensional helmholtz coil is used to generate magnetic field data in different directions and different sizes, an error model equation set is constructed, and then 21 unknown parameters in the model are estimated. This embodiment specifically adopts 3D Helmholtz coil, and this coil comprises three complete orthogonal coils, and the coil is by current drive, and every coil all has corresponding current controller, through the electric current of control flow coil, can generate arbitrary magnetic field component in the even region in center of three-dimensional coil, then can produce the even region in high accuracy magnetic field of any size through three-dimensional Helmholtz coil. According to the embodiment, compensation is realized by combining the three-dimensional Helmholtz coil, self-adaption flexible compensation can be performed according to different application scenes, for example, the gradient of a background magnetic field can be simulated, the compensation is simple and convenient to realize, and good compensation precision can be ensured.
Preferably, when the geomagnetic vector measurement system is placed in the central region of the three-dimensional helmholtz coil in step S02, three sensitive axis directions of the three-axis magnetic field sensor of the geomagnetic vector measurement system are specifically aligned with three orthogonal directions of the three-dimensional helmholtz coil.
Preferably, when the three-dimensional helmholtz coil generates magnetic field data in different directions and different sizes, different directions and amplitudes are generated in the three-dimensional spherical involute by specifically controlling a current sequence of the three-dimensional helmholtz coil, and the current sequences of the three orthogonal coils are specifically obtained according to the following spherical involute equation:
where R represents the radial direction of the involute, θ represents the involute flare angle, α represents the involute pressure angle, the current sequence will change with the change in θ and α, and the sampling intervals Δ θ and Δ α will determine the magnetic field rate of change.
In a specific application embodiment, different directions and amplitudes can be generated in the three-dimensional spherical involute as shown in fig. 4. Part of the current curve is shown in fig. 5, based on the currents of three orthogonal coils generated in a three-dimensional spherical involute.
After magnetic field components with different amplitudes and directions are generated in a uniform region of the three-dimensional Helmholtz coil, multiple groups of measurement data including output value H of the triaxial magnetic field sensor can be obtained through measurement m True value H generated by three-dimensional Helmholtz coil 0 And the rate of change of the true value produced by the three-dimensional Helmholtz coil over time
Based on the multiple sets of measurement data and the models shown in the formulas (6) to (8), a model equation set can be constructed as follows:
where N denotes the number of points measured, dH 0 Dt represents H 0 The rate of change of the magnetic field with respect to time.
And further solving the linear equation set in the formula (9) to estimate 21 unknown parameters of the permanent magnet, the induction field and the eddy current field, and calculating the magnetic interference field according to the error parameters after accurately estimating all 21 unknown parameters to obtain an expected true value of the geomagnetic vector so as to realize the compensation of the magnetic interference field of the geomagnetic vector measurement system. Preferably, a linear least square method can be used for solving the parameters, and the magnetic field data generated by the three-dimensional Helmholtz coil can ensure that the equation has no complex collinearity as much as possible, so that the error parameters can be accurately and quickly estimated by using the linear least square method, and the solving efficiency and precision can be further improved.
In step S04 of this embodiment, when the parameters in the error model equation set are solved, the method further includes determining whether the magnetic interference field of the geomagnetic vector measurement system compensated by the solved parameters meets the preset compensation requirement, if so, the compensation is finished, otherwise, the method returns to step S02 until the preset compensation requirement is met. And the required compensation precision requirement can be accurately met finally through multiple iterations.
As shown in fig. 3, in a specific application embodiment, the geomagnetic vector measurement system is first prevented from being on a non-magnetic platform at the center of a three-dimensional helmholtz coil (as shown in fig. 2), and then magnetic field components with different amplitudes and directions are generated in a uniform region of the coil to construct a model error equation, as shown in equation (9); and then, a least square algorithm is sampled, each unknown parameter is estimated to be used for compensating the geomagnetic vector measurement system, whether the compensation precision is met or not is judged after each compensation, and if the compensation precision is not met, the steps are repeatedly executed until the compensation precision requirement is finally met. In the embodiment, the geomagnetic vector measurement system is arranged in the center of the uniform area of the three-dimensional Helmholtz coil, and the equation set of the error parameters is established by utilizing the magnetic fields with different amplitudes, different directions and different change rates generated by the coil, so that the equation set is established without depending on the posture of the traditional rotation measurement system in the whole compensation process, the operation is simple, the cost is low, the self-adaptive flexible compensation can be performed according to different application scenes, and meanwhile, the good compensation precision is ensured.
In the component compensation of the geomagnetic vector measurement system, a compensation model integrating a permanent magnetic field, an induction magnetic field and an eddy magnetic field is established, different vector magnetic fields are generated by adopting a three-dimensional Helmholtz coil, the geomagnetic vector measurement system is placed in the central area of the three-dimensional Helmholtz coil, an error equation set is established according to the compensation model and multiple sets of measurement data, and error parameter estimation is carried out by solving the equation set, so that enough representative data can be quickly generated to establish an equation, the compensation efficiency and the compensation 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 established by a rotating platform. In addition, the geomagnetic field vector measurement method and the geomagnetic field vector measurement system can be suitable for being carried in various scenes where the geomagnetic field vector measurement system carries out geomagnetic vector measurement on platforms such as an autonomous underwater vehicle or an unmanned aerial vehicle, and when the three-dimensional Helmholtz coil is large enough, an interference source of the platform can be considered together with an interference source of the measurement system.
In order to verify the effectiveness of the method of the present invention, in a specific application example, the method of the present invention is used for a compensation test, and an experimental apparatus is shown in fig. 2, and includes: 1) The geomagnetic field vector measurement system comprises a high-precision optical fiber inertial navigation system (INS for providing attitude information) and a Mag-13 triaxial fluxgate magnetometer (for measuring magnetic components); 2) 3D helmholtz coils (creating arbitrary magnetic field components); 3) A data processor, data acquisition software and data processing software. The sampling rate of the magnetometer is specifically 20Hz. It should be noted that the three-axis magnetometer was calibrated before the experiment, and the output error after calibration was reduced to below 1 nT. Inertial navigation systems have also been calibrated in the laboratory using a turntable with three degrees of freedom.
According to the Mag-13 magnetometer handbook, the main performance indexes are as follows: magnetic field range of each sensor axis: 100uT; quadrature error: < +/-0.1 degrees; offset amount: <5nT; noise: <5pTrms/Hz-1Hz is 1/2. According to the INS manual, the main performance specifications are as follows: attitude precision: <0.008 °; head angle range: 0 degree to 360 degrees; pitch angle range: 90 degrees; rolling angle range: 180 deg.. According to the 3D helmholtz coils handbook, the main performance specifications are as follows: coil size: 1 m; uniformity: 0.1% in the central region of 260cm 3; quadrature error: < +/-0.01 degrees;
the embodiment realizes the specific steps of compensation of the geomagnetic vector measurement system:
(1) the geomagnetic vector measurement system is placed at the center of the three-dimensional helmholtz coil, as shown in fig. 2.
(2) The three-dimensional Helmholtz coil generates a magnetic field under the excitation of the predefined coil current, and the output value H of the three-axis magnetic field sensor starts to be recorded m And true value H generated by a three-dimensional Helmholtz coil 0 And H 0 The partial data obtained with the time-dependent rate of change are shown in Table 1.
(3) Obtaining the following equation set according to the obtained data sets and the formula (9):
(4) and solving the linear equation set, estimating 21 unknown parameters of the permanent magnet, the induction and the eddy current field, judging whether the compensation precision requirement is met, and if so, finishing the compensation. Otherwise, returning to the step (2) until the requirement is met. When all 21 unknown parameters are accurately estimated, the error parameters can be used for compensating the magnetic interference field of the geomagnetic vector measurement system.
Table 1: measurement data of a part of a three-axis magnetic field sensor and truth data generated by a coil
As shown in table 2, the rms errors of the north, vertical, east components and total intensity were reduced from 3448.3nT, 4396.2nT, 4096.2nT and 3994.1nT to 58.92nT, 60.88nT, 65.72nT and 65.92nT, respectively, after compensation using the proposed method.
Table 2: interference magnetic field compensation effect (nT)
According to the experimental result, 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 precision and reliability of geomagnetic vector measurement.
This embodiment still provides earth magnetism vector measurement system compensation system based on three-dimensional helmholtz coil and includes:
the measurement control module is used for placing the geomagnetic vector measurement system in the 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 the output value of the three-axis magnetic field sensor, the true value generated by the three-dimensional Helmholtz coil and the 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 the 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 the 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.
The compensation system of the geomagnetic vector measurement system based on the three-dimensional helmholtz coil in this embodiment corresponds to the compensation method of the geomagnetic vector measurement system based on the three-dimensional helmholtz coil, and is not described here any more.
According to the method, an interference magnetic field component compensation model containing a permanent magnetic field, an induction magnetic field and an eddy magnetic field is established, the three-dimensional Helmholtz coil is adopted to generate different vector magnetic fields so as to construct an error parameter equation, a reasonable enough data set can be conveniently obtained by controlling the current of the coil, enough representative data can be rapidly generated to construct the equation, a compensation equation does not need to be constructed through a rotary platform, the magnetic field data generated by the three-dimensional Helmholtz coil can ensure that the equation does not have complex collinearity as much as possible, so that the error parameters can be more accurately estimated, meanwhile, the three-dimensional Helmholtz coil is used, flexible compensation can be carried out according to different application scenes, the compensation implementation is simple, the cost is low, the compensation precision is high, and compared with the traditional rotation strategy, the compensation can be completed in a shorter time.
The foregoing is illustrative of the preferred embodiments of the present invention and is not to be construed as limiting the invention in any way. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Therefore, any simple modification, equivalent change and modification 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, unless the technical essence of the present invention departs from the content 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;
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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