Gradient-based carrier platform near-field magnetic interference compensation method and system

Abstract

The invention discloses a gradient-based carrier platform near-field magnetic interference compensation method and system, and relates to the technical field of magnetic interference compensation. The method is characterized by comprising the following steps: acquiring two groups of magnetic field intensity data acquired by a pair of asymmetrically mounted magnetometers, wherein the magnetic field intensity data comprises an environment magnetic interference signal, a platform magnetic interference signal and a target magnetic field signal; acquiring two groups of magnetic field direction data acquired by a pair of asymmetrically mounted fluxgates; filtering the two groups of magnetic field intensity data by using a calibrated band-pass filter to obtain an environment magnetic interference signal; constructing a matrix containing geomagnetic direction cosine and a time derivative thereof based on the magnetic field direction data; calculating by using the matrix and a calibrated compensation coefficient matrix to obtain a platform magnetic interference signal; and subtracting the filtered environment magnetic interference signal and the calculated platform magnetic interference signal from the magnetic field intensity data to obtain a target magnetic field signal. The accuracy of magnetic interference separation is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic interference compensation, and specifically relates to a gradient-based near-field magnetic interference compensation method and system for a carrier platform. Background Art

[0002] Magnetic compensation technology is a technology for compensating various traceable magnetic interference types in the process of airborne magnetic exploration. By analyzing and modeling various interferences causing magnetic anomalies, then calculating the magnetic interference of this type during the magnetic exploration of the carrier platform by monitoring a certain characteristic of the magnetic interference source, and finally compensating this type of magnetic interference through data processing means to obtain the true magnetic field value measured by the probe.

[0003] During the actual magnetic exploration process of the carrier platform, there are various types of magnetic interferences. Among the measurable magnetic interferences, the most influential one is the magnetic interference brought by the carrier platform, and the magnetic interference of this type can be coefficient-calibrated and compensated through the T-L model. The working process of the T-L model mainly includes identifying, calculating, and compensating the magnetic interference generated by the flight platform; first, collecting the magnetic field data recorded by the instrument during the magnetic exploration process, and classifying these data into different magnetic interference types caused by the magnetic substances of the carrier platform itself, motion induction, current eddy currents, etc.; next, by establishing a mathematical model, representing the actually measured magnetic field as a combination of these interferences, and applying the T-L formula to form a system of linear equations; using numerical methods such as the least squares method to solve this system of equations to obtain the coefficients of various magnetic interferences; subsequently, using these coefficients to compensate the measurement data to remove the interference influence and finally obtain the corrected magnetic field data.

[0004] However, during the magnetic compensation process of the carrier platform, there are not only magnetic interferences generated by the carrier platform itself, but also environmental magnetic interferences. If the environmental magnetic interferences are not compensated, it is easy to cause the problem of low data quality of the sensors carried by the carrier platform after compensation. Summary of the Invention

[0005] In view of the above problems, the present invention proposes a gradient-based near-field magnetic interference compensation method and system for a carrier platform.

[0006] According to one aspect of the present invention, a gradient-based near-field magnetic interference compensation method for a carrier platform is proposed, and the method includes:

[0007] Obtaining two groups of magnetic field intensity data collected by a pair of magnetometers installed asymmetrically, where the magnetic field intensity data includes environmental magnetic interference signals, platform magnetic interference signals, and target magnetic field signals; among them, the phases and amplitudes of the two groups of platform magnetic interference signals in the two groups of magnetic field intensity data are different;

[0008] Obtaining two groups of magnetic field direction data collected by a pair of fluxgates installed asymmetrically;

[0009] Filter the two sets of magnetic field intensity data using a calibrated band - pass filter to obtain the environmental magnetic interference signal;

[0010] Construct a matrix containing the geomagnetic direction cosine and its time derivative based on the magnetic field direction data; Calculate the platform magnetic interference signal using the calibrated compensation coefficient matrix and the matrix containing the geomagnetic direction cosine and its time derivative;

[0011] Subtract the environmental magnetic interference signal obtained after filtering the magnetic field intensity data and the calculated platform magnetic interference signal from the magnetic field intensity data to obtain the target magnetic field signal.

[0012] Further, the calibration process of the band - pass filter includes:

[0013] Obtain two sets of calibrated measurement magnetic field intensity data collected by a pair of magnetometers installed asymmetrically, and the calibrated measurement magnetic field intensity data includes the environmental magnetic interference signal and the platform magnetic interference signal; Among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of calibrated measurement magnetic field intensity data are different;

[0014] Perform Fourier transforms on the two sets of calibrated measurement magnetic field intensity data respectively;

[0015] Subtract and add the two sets of calibrated measurement magnetic field intensity data respectively, and perform Fourier transforms on the subtraction result and the addition result respectively;

[0016] Based on the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data, and the Fourier transform results of the subtraction result and the addition result, determine two frequency intervals;

[0017] Take the intersection of the two frequency intervals as the frequency band of the environmental magnetic interference signal, and use this frequency band as the frequency band of the band - pass filter, thereby obtaining the calibrated band - pass filter.

[0018] Further, the determining of the two frequency intervals based on the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data, and the Fourier transform results of the subtraction result and the addition result includes:

[0019] The first frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data are the same and the amplitude in the Fourier transform result of the subtraction result is zero;

[0020] The second frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data are the same and the amplitude in the Fourier transform result of the addition result is twice the amplitude of the Fourier transform result of any one set of calibrated measurement magnetic field intensity data.

[0021] Further, the calibration process of the band - pass filter includes:

[0022] Obtain two sets of calibrated measurement magnetic field intensity data collected by a pair of magnetometers installed asymmetrically. The calibrated measurement magnetic field intensity data includes environmental magnetic interference signals and platform magnetic interference signals. Among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of calibrated measurement magnetic field intensity data are different;

[0023] Perform wavelet transform on the two sets of calibrated measurement magnetic field intensity data respectively;

[0024] Subtract and add the two sets of calibrated measurement magnetic field intensity data respectively, and perform wavelet transform on the subtraction result and the addition result respectively;

[0025] Based on the wavelet transform results of the two sets of calibrated measurement magnetic field intensity data, and the wavelet transform results of the subtraction result and the addition result, determine two scale intervals;

[0026] Take the intersection of the two scale intervals as the scale interval of the environmental magnetic interference signal, and use this scale interval as the scale interval of the band - pass filter, thereby obtaining a calibrated band - pass filter.

[0027] Further, the determining two scale intervals based on the wavelet transform results of the two sets of calibrated measurement magnetic field intensity data, and the wavelet transform results of the subtraction result and the addition result includes:

[0028] The first scale interval is: the scale interval where the absolute values of the time coefficients in the wavelet transform results of the two sets of calibrated measurement magnetic field intensity data are the same and the absolute value of the same time coefficient in the wavelet transform result of the subtraction result is zero;

[0029] The second frequency interval is: the scale interval where the absolute values of the time coefficients in the wavelet transform results of the two sets of calibrated measurement magnetic field intensity data are the same and the absolute value of the same time coefficient in the wavelet transform result of the addition result is twice the absolute value of the wavelet transform result of any set of calibrated measurement magnetic field intensity data.

[0030] Further, the matrix containing the geomagnetic direction cosine and its time derivative is constructed as follows:

[0031]

[0032] In the formula, u i , i = 1, 2, 3 represent the geomagnetic direction cosine; u i ′, i = 1, 2, 3 is the time derivative of u i , i = 1, 2, 3.

[0033] Further, the calibration process of the compensation coefficient matrix includes:

[0034] Construct a compensation coefficient matrix using the T-L model as follows:

[0035]

[0036] In the formula, p1, p2, and p3 respectively represent the components of the fixed magnetic field on the x, y, and z axes; All are interference coefficients to be solved;

[0037] Use a calibrated band-pass filter to filter two groups of calibrated measured magnetic field intensity data to obtain a calibrated environmental magnetic interference signal;

[0038] Subtract the calibrated environmental magnetic interference signal from the calibrated measured magnetic field intensity data to obtain a calibrated platform magnetic interference signal H I ;

[0039] Use the recursive least squares method to solve the following formula to obtain the compensation coefficient matrix θ:

[0040] H I = F × θ.

[0041] According to another aspect of the present invention, a near-field magnetic interference compensation system for a carrier platform based on gradient is proposed. The system includes:

[0042] A data acquisition module configured to acquire two groups of magnetic field intensity data collected by a pair of magnetometers installed asymmetrically. The magnetic field intensity data includes an environmental magnetic interference signal, a platform magnetic interference signal, and a target magnetic field signal; wherein, the phases and amplitudes of the two platform magnetic interference signals in the two groups of magnetic field intensity data are different; acquire two groups of magnetic field direction data collected by a pair of fluxgates installed asymmetrically;

[0043] A magnetic interference signal calculation module configured to use a calibrated band-pass filter to filter two groups of magnetic field intensity data to obtain an environmental magnetic interference signal; construct a matrix containing geomagnetic direction cosines and their time derivatives based on the magnetic field direction data; calculate and obtain a platform magnetic interference signal using the calibrated compensation coefficient matrix and the matrix containing geomagnetic direction cosines and their time derivatives;

[0044] A magnetic interference compensation module configured to subtract the environmental magnetic interference signal obtained after filtering and the calculated platform magnetic interference signal from the magnetic field intensity data to obtain the target magnetic field signal.

[0045] Further, the calibration process of the band-pass filter in the magnetic interference signal calculation module includes:

[0046] Obtain two sets of calibrated measured magnetic field intensity data collected by a pair of magnetometers installed asymmetrically. The calibrated measured magnetic field intensity data includes environmental magnetic interference signals and platform magnetic interference signals. Among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of calibrated measured magnetic field intensity data are different;

[0047] Perform Fourier transforms on the two sets of calibrated measured magnetic field intensity data respectively;

[0048] Subtract and add the two sets of calibrated measured magnetic field intensity data respectively, and perform Fourier transforms on the subtraction result and the addition result respectively;

[0049] Based on the Fourier transform results of the two sets of calibrated measured magnetic field intensity data, and the Fourier transform results of the subtraction result and the addition result, determine two frequency intervals. Among them, the two frequency intervals include: The first frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated measured magnetic field intensity data are the same and the amplitude in the Fourier transform result of the subtraction result is zero; The second frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated measured magnetic field intensity data are the same and the amplitude in the Fourier transform result of the addition result is twice the amplitude of the Fourier transform result of any one set of calibrated measured magnetic field intensity data;

[0050] Take the intersection of the two frequency intervals as the frequency band of the environmental magnetic interference signal, and use this frequency band as the frequency band of the band-pass filter, thereby obtaining a calibrated band-pass filter.

[0051] Further, the matrix containing the geomagnetic direction cosine and its time derivative in the magnetic interference signal calculation module is constructed as follows:

[0052]

[0053] In the formula, u i , i = 1, 2, 3 represent the geomagnetic direction cosine; u′ i , i = 1, 2, 3 is the time derivative of u i , i = 1, 2, 3;

[0054] The calibration process of the compensation coefficient matrix includes:

[0055] Use the T-L model to construct the compensation coefficient matrix as follows:

[0056]

[0057] In the formula, p1, p2, p3 respectively represent the components of the fixed magnetic field on the x, y, z axes; are all interference coefficients to be solved;

[0058] Filter the two groups of calibrated measured magnetic field intensity data by using a calibrated band-pass filter to obtain a calibrated environmental magnetic interference signal;

[0059] Subtract the calibrated environmental magnetic interference signal from the calibrated measured magnetic field intensity data to obtain a calibrated platform magnetic interference signal H I ;

[0060] Solve the following formula by using the recursive least squares method to obtain a compensation coefficient matrix θ:

[0061] F I = F × θ.

[0062] The beneficial technical effects of the present invention are:

[0063] The present invention provides a gradient-based near-field magnetic interference compensation method and system for a carrier platform, aiming to solve the problem that the data quality of the sensors carried by the carrier platform is low after compensation due to the existence of environmental magnetic interference in addition to the magnetic interference generated by the carrier platform itself during the magnetic compensation process of the carrier platform. Through actual on-site data collection and adaptive frequency band identification, the present invention can dynamically adjust the environmental magnetic interference frequency band, significantly improving the accuracy of magnetic interference separation. Compared with the method relying on geomagnetic diurnal variation station data, the present invention is more accurate and more targeted at the on-site magnetic field environment. The present invention can be applied to the separation of environmental magnetic interference and platform magnetic interference in a carrier platform magnetic compensation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features, and advantages of the exemplary embodiments of the present invention will become readily understood. In the drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, wherein:

[0065] Figure 1 is a flowchart of a gradient-based near-field magnetic interference compensation method for a carrier platform according to an embodiment of the present invention.

[0066] Figure 2 is a schematic diagram of the installation of gradient sensors in an embodiment of the present invention.

[0067] Figure 3 is a schematic structural diagram of a gradient-based near-field magnetic interference compensation system for a carrier platform according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0068] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are provided only to enable those skilled in the art to better understand and thus implement the present invention, rather than to limit the scope of the present invention in any way. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to be able to fully convey the scope of the present disclosure to those skilled in the art.

[0069] Those skilled in the art know that the embodiments of the present invention can be implemented as a system, device, equipment, method, or computer program product. Therefore, the present disclosure can be specifically implemented in the following forms: complete hardware, complete software (including firmware, resident software, microcode, etc.), or a combination of hardware and software. In this article, it should be understood that any number of elements in the drawings is for illustration rather than limitation, and any naming is only for distinction and does not have any limiting meaning.

[0070] In existing methods, generally the data of geomagnetic diurnal variation stations are used to obtain the environmental magnetic interference during the magnetic compensation process, or the frequency band of the default environmental magnetic interference is a certain fixed interval, or filtering is only carried out according to a pre-fixed frequency band to separate the environmental magnetic interference, without analyzing the on-site measured data. The present invention obtains the frequency band of the environmental magnetic interference according to the gradient sensor to separate the environmental magnetic interference.

[0071] An embodiment of the present invention provides a method for compensating near-field magnetic interference of a carrier platform based on gradient, as Figure 1 shown, the method includes:

[0072] S1. Obtain two groups of magnetic field intensity data collected by a pair of magnetometers installed asymmetrically, where the magnetic field intensity data includes environmental magnetic interference signals, platform magnetic interference signals, and target magnetic field signals; among them, the phases and amplitudes of the two groups of platform magnetic interference signals in the two groups of magnetic field intensity data are different;

[0073] S2. Obtain two groups of magnetic field direction data collected by a pair of fluxgates installed asymmetrically;

[0074] S3. Filter the two groups of magnetic field intensity data by using a calibrated band-pass filter to obtain environmental magnetic interference signals;

[0075] S4. Construct a matrix containing geomagnetic direction cosines and their time derivatives based on the magnetic field direction data; calculate and obtain platform magnetic interference signals by using a calibrated compensation coefficient matrix and the matrix containing geomagnetic direction cosines and their time derivatives;

[0076] S5. Subtract the environmental magnetic interference signals obtained after filtering and the calculated platform magnetic interference signals from the magnetic field intensity data to obtain the target magnetic field signals.

[0077] The method starts from S1. In S1, two sets of magnetic field intensity data collected by a pair of asymmetrically installed magnetometers are obtained. The magnetic field intensity data includes ambient magnetic interference signals, platform magnetic interference signals, and target magnetic field signals. Then, in S2, two sets of magnetic field direction data collected by a pair of asymmetrically installed fluxgate sensors are obtained.

[0078] According to an embodiment of the present invention, a gradient sensor is a pair of sensors located at different positions to capture the differences between data at different positions. The sensors that act as gradient sensors in the present invention are a pair of magnetometer sensors (magnetometer 1 and magnetometer 2) and a pair of three-component magnetic field magnetometers (abbreviated as fluxgate in the present invention, fluxgate 1 and fluxgate 2). Magnetometer 1 and magnetometer 2 are installed at asymmetric positions on the platform, and fluxgate 1 and fluxgate 2 are also installed at asymmetric positions on the platform (fluxgate 1 is close to the position of magnetometer 1, and fluxgate 2 is close to the position of magnetometer 2). An example is shown Figure 2 as shown.

[0079] The magnetic interference generated by the ambient magnetic field at the positions of the two magnetometers is the same; however, because the two magnetometers are at different positions on the platform, the magnetic interference generated by the platform on the two magnetometers is different, that is, the phases and amplitudes of the magnetic interference signals are different. At the same time, the frequency ranges of the ambient magnetic interference signals and the platform magnetic interference signals generally do not overlap.

[0080] During the actual operation of compensating for magnetic interference, the data of the sensors are collected. Taking magnetometer 1 and fluxgate 1 as an example, the data collected by magnetometer 1 is H1. During the actual operation, in addition to the platform interference and the ambient magnetic field interference, there is also the magnetic field of the monitored target in H1.

[0081] Then S3 is executed. In S3, the two sets of magnetic field intensity data are filtered by a calibrated band-pass filter to obtain ambient magnetic interference signals. The calibration process of the band-pass filter includes:

[0082] S31: Obtain two sets of calibrated measurement magnetic field intensity data collected by a pair of asymmetrically installed magnetometers. The calibrated measurement magnetic field intensity data includes ambient magnetic interference signals and platform magnetic interference signals. Among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of calibrated measurement magnetic field intensity data are different;

[0083] S32: Perform Fourier transforms on the two sets of calibrated measurement magnetic field intensity data respectively;

[0084] S33: Subtract and add the two sets of calibrated measurement magnetic field intensity data respectively, and perform Fourier transforms on the subtraction result and the addition result respectively;

[0085] S34. Determine two frequency intervals based on the Fourier transform results of two sets of calibrated magnetic field intensity measurement data, as well as the Fourier transform results of the difference result and the sum result, including:

[0086] The first frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated magnetic field intensity measurement data are the same and the amplitude in the Fourier transform result of the difference result is zero;

[0087] The second frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated magnetic field intensity measurement data are the same and the amplitude in the Fourier transform result of the sum result is twice that of the Fourier transform result of any one set of calibrated magnetic field intensity measurement data;

[0088] S35. Take the intersection of the two frequency intervals as the frequency band of the environmental magnetic interference signal, and use this frequency band as the frequency band of the band-pass filter, thereby obtaining a calibrated band-pass filter.

[0089] According to the embodiments of the present invention, the calibration operation of the band-pass filter is carried out in an area without electromagnetic interference and magnetic field anomalies. Ensure that during the calibration process, the magnetic field measured by the sensor is only environmental interference and platform interference. Specifically, record the start and end times of the calibration operation process. First, collect the data collected by each sensor (a pair of magnetometers and a pair of fluxgate sensors) during the operation process. Regard the data of magnetometer 1 as the superposition of environmental magnetic interference and the platform magnetic interference at this position, that is, H1 = H e +H I1 ; Similarly, the data of magnetometer 2 can be expressed as H2 = H e +H I2 . Then, perform Fourier transform on H1 and H2, and the frequency range to be investigated is from 0 to nHz (the sampling frequency of the sensor). The obtained results are X(H1) = X(H e ) + X(H I1 ) and X(H2) = X(H e ) + X(H I2 ). Then, perform the following operations on the collected signals respectively: Subtract H1 and H2 to get D = H1 - H2 = H I1 -H I2 ; Add H1 and H2 to get P = H1 + H2 = 2H e +H I1 +H I2 . Then, perform Fourier transform on D and P, and the obtained results are X(D) = X(H I1 ) - X(H I2 ), X(P) = 2X(H e ) + X(H I1 ) + X(H I2)。Then, compare X(H1), X(H2), X(D), and X(P), and find the following two frequency intervals respectively: the frequency interval where the amplitudes and phases are consistent in X(H1) and X(H2) and the amplitude of X(D) is zero; the frequency interval where the amplitudes and phases are consistent in X(H1) and X(H2) and the amplitude of X(P) becomes twice that of X(H1) and X(H2). Then, take the intersection (a, b) of the two frequency intervals as the frequency band of H e and select a band-pass filter with the frequency band (a, b) to filter H1 and H2, and the filtering result is the environmental magnetic interference H e .

[0090] The above process completes the calibration of the band-pass filter. Use the calibrated band-pass filter above to filter the two sets of magnetic field intensity data to obtain the environmental magnetic interference signal.

[0091] In this embodiment, optionally, S32 to S35 can be replaced by the following process:

[0092] S32': Perform wavelet transform on the two sets of calibrated measured magnetic field intensity data respectively;

[0093] S33': Subtract and add the two sets of calibrated measured magnetic field intensity data respectively, and perform wavelet transform on the subtraction result and the addition result respectively;

[0094] S34': Based on the wavelet transform results of the two sets of calibrated measured magnetic field intensity data, as well as the wavelet transform results of the subtraction result and the addition result, determine two scale intervals;

[0095] S35': Take the intersection of the two scale intervals as the scale interval of the environmental magnetic interference signal, and use this scale interval as the scale interval of the band-pass filter, thereby obtaining the calibrated band-pass filter.

[0096] Specifically, perform wavelet transform on H1 and H2, and the frequency range under investigation is from 0 to n (corresponding to the sampling frequency of the sensor). The obtained results are X(H1) = X(H e ) + X(H I1 ) and X(H2) = X(H e ) + X(H I2 ); then, perform the following operations on the collected signals respectively: Subtract H1 and H2 to get D = H1 - H2 = H I1 - H I2 ; Add H1 and H2 to get P = H1 + H2 = 2H e + H I1 + H I2 ; then, perform wavelet transform on D and P, and the obtained results are X(D) = X(H I1 ) - X(HI2 )、X(P) = 2X(H e ) + X(H I1 ) + X(H I2 ); Then, compare X(H1), X(H2), X(D), X(P), and find the following two scale intervals respectively: the scale interval where the absolute values of the same time coefficients in X(H1) and X(H2) are the same and the absolute value of the same time coefficient in X(D) is zero; the scale interval where the absolute values of the same time coefficients in X(H1) and X(H2) are the same and the absolute value of the same time coefficient in X(P) is twice that of X(H1) and X(H2); Then, take the intersection (a, b) of the two intervals as the scale interval of H e and make a band-pass filter according to this result to obtain the environmental magnetic interference H at H1 and H2 e .

[0097] Then execute S4. In S4, construct a matrix containing the geomagnetic direction cosine and its time derivative based on the magnetic field direction data; calculate and obtain the platform magnetic interference signal by using the calibrated compensation coefficient matrix and the matrix containing the geomagnetic direction cosine and its time derivative; where, the calibration process of the compensation coefficient matrix includes:

[0098] S41. Use the T-L model to construct the compensation coefficient matrix as follows:

[0099]

[0100] In the formula, p1, p2, p3 respectively represent the components of the fixed magnetic field on the x, y, z axes; are all interference coefficients to be solved;

[0101] S42. Use the calibrated band-pass filter to filter two groups of calibrated measured magnetic field intensity data to obtain the calibrated environmental magnetic interference signal;

[0102] S43. Subtract the calibrated environmental magnetic interference signal from the calibrated measured magnetic field intensity data to obtain the calibrated platform magnetic interference signal H I ;

[0103] S44. Use the recursive least squares method to solve the following formula to obtain the compensation coefficient matrix θ:

[0104] H I = F × θ.

[0105] According to the embodiments of the present invention, use the T-L model and the calibrated data collected by the fluxgate to solve the compensation coefficient matrix.

[0106] The platform is made of metal materials. Under the action of an external magnetic field, some of the materials are magnetized to form a strong magnetic field, which is called the fixed magnetic field. The magnitude and direction of the fixed magnetic field do not change with the change of the external magnetic field, nor with the change of the maneuvering actions. In the platform coordinate system (with magnetometer 1 as the origin, the L-axis pointing to the front of the platform, the T-axis pointing to the left of the platform, and the V-axis pointing directly below the aircraft), the fixed magnetic field H p has a vector form of:

[0107]

[0108] The simultaneously existing induced magnetic field is mainly generated by the magnetization of the soft magnetic materials in the platform under the action of the background geomagnetic field. Its magnitude and direction are related to the magnitude and direction of the background geomagnetic field in the platform coordinate system and can be expressed as:

[0109]

[0110] where X, Y, and Z respectively represent the three angles between the geomagnetic vector and the platform coordinate system, cosX, cosY, and cosZ are called the geomagnetic direction cosines, H0 is the total value of the geomagnetic field, and A is the coefficient matrix to be determined.

[0111] The existing eddy current field is the magnetic field generated by the cutting of the geomagnetic field by the metal materials of the platform during the navigation of the platform. This magnetic field is related to the rate of change of the geomagnetic field with time and can be expressed as:

[0112]

[0113] where cos′X, cos′Y, and cos′Z represent the derivatives of cosX, cosY, and cosZ with respect to time, and B is the coefficient matrix to be determined. Combining the fixed field, the induced field, and the eddy current field, the platform interference obtained is:

[0114]

[0115] Converting the vector model to a scalar model gives:

[0116]

[0117] And there is Substituting into the above formula, we get:

[0118]

[0119] Let:

[0120] u1 = cosX, u2 = cosY, u3 = cosZ

[0121] u′1 = cos′X, u′2 = cos′Y, u′3 = cosZ

[0122] p1 = H px , p2 = H py , p3 = H pz ,

[0123] Then we can obtain:

[0124]

[0125] And assuming that the background field remains unchanged, then Making further simplification gives:

[0126]

[0127] Furthermore, the geomagnetic field H0 and the interference coefficient a ij , i, j = 1, 2, 3, b ij , i, j = 1, 2, 3 can be combined to obtain a new interference coefficient: Then the formula in the previous step can be further simplified to:

[0128]

[0129] Wherein,

[0130]

[0131] In matrix F, u i , i = 1, 2, 3 represents the geomagnetic direction cosine, and u' i , i = 1, 2, 3 is the time derivative of u i , i = 1, 2, 3.

[0132] Then, using the calibrated band-pass filter to filter the two groups of calibrated measured magnetic field intensity data to obtain the calibrated environmental magnetic interference signal; and subtracting the calibrated environmental magnetic interference signal from the calibrated measured magnetic field intensity data to obtain the calibrated platform magnetic interference signal H I . Taking the data of magnetometer 1 as an example, subtracting the calibrated environmental magnetic interference signal H e from the calibrated measured magnetic field intensity data H1 to obtain the calibrated platform magnetic interference signal H I1 , and using the T-L model mentioned above and given the derivation, constructing through the value of fluxgate 1:

[0133]

[0134] According to the formula H I1 = F1θ1, using the recursive least squares method to calculate and obtain the 18-term compensation coefficient matrix θ1. Similarly, θ2 is calculated.

[0135] The compensation coefficient matrix is obtained through the above calibration process. During the actual operation of compensating for magnetic interference, a matrix F including geomagnetic direction cosine and its time derivative is constructed based on the magnetic field direction data (data collected by the fluxgate); the calibrated compensation coefficient matrix θ1 or θ2 and the matrix are used to calculate the platform magnetic interference signal H according to the formula I = F×θ I1 and H I2 .

[0136] Then, S5 is executed. In S5, the target magnetic field signal is obtained by subtracting the environmental magnetic interference signal obtained after filtering processing and the calculated platform magnetic interference signal from the magnetic field intensity data.

[0137] According to an embodiment of the present invention, after filtering processing using a calibrated filter, the environmental interference H e is obtained, and the environmental magnetic interference signal H e is subtracted from the magnetic field intensity data collected by the magnetometer to obtain the platform magnetic interference signal and the target magnetic field data. Then, the matrix F is constructed using the data collected by the fluxgate, and the calibrated compensation coefficient matrix is used to calculate the platform magnetic interference signal H I , and then the target magnetic field data is obtained, that is, the target result after compensating for the platform interference and the environmental magnetic field interference is obtained.

[0138] Through actual on-site data collection and adaptive frequency band identification, the present invention can dynamically adjust the environmental magnetic interference frequency band, significantly improving the accuracy of magnetic interference separation. Compared with the method relying on the data of the geomagnetic diurnal variation station, the present invention is more accurate and more targeted at the on-site magnetic field environment.

[0139] Another embodiment of the present invention proposes a gradient-based near-field magnetic interference compensation system for a carrier platform, as Figure 3 shown. The system includes:[[]]

[0140] A data acquisition module 310 configured to acquire two sets of magnetic field intensity data collected by a pair of asymmetrically installed magnetometers. The magnetic field intensity data includes an environmental magnetic interference signal, a platform magnetic interference signal, and a target magnetic field signal; wherein, the phases and amplitudes of the two platform magnetic interference signals in the two sets of magnetic field intensity data are different; two sets of magnetic field direction data collected by a pair of asymmetrically installed fluxgates are acquired.

[0141] A magnetic interference signal calculation module 320 configured to perform filtering processing on the two sets of magnetic field intensity data using a calibrated band-pass filter to obtain the environmental magnetic interference signal; construct a matrix including geomagnetic direction cosine and its time derivative based on the magnetic field direction data; calculate the platform magnetic interference signal using the calibrated compensation coefficient matrix and the matrix including geomagnetic direction cosine and its time derivative.

[0142] The magnetic interference compensation module 330 is configured to subtract the environmental magnetic interference signal obtained after filtering processing from the magnetic field intensity data and the platform magnetic interference signal obtained through calculation to obtain the target magnetic field signal.

[0143] In this embodiment, preferably, the calibration process of the band-pass filter in the magnetic interference signal calculation module 320 includes:

[0144] Obtain two sets of calibrated measurement magnetic field intensity data collected by a pair of magnetometers asymmetrically installed, where the calibrated measurement magnetic field intensity data includes an environmental magnetic interference signal and a platform magnetic interference signal; among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of calibrated measurement magnetic field intensity data are different;

[0145] Perform Fourier transforms on the two sets of calibrated measurement magnetic field intensity data respectively;

[0146] Subtract and add the two sets of calibrated measurement magnetic field intensity data respectively, and perform Fourier transforms on the subtraction result and the addition result respectively;

[0147] Based on the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data, and the Fourier transform results of the subtraction result and the addition result, determine two frequency intervals; among them, the two frequency intervals include: the first frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data are the same and the amplitude in the Fourier transform result of the subtraction result is zero; the second frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data are the same and the amplitude in the Fourier transform result of the addition result is twice the amplitude of the Fourier transform result of any one set of calibrated measurement magnetic field intensity data;

[0148] Take the intersection of the two frequency intervals as the frequency band of the environmental magnetic interference signal, and use this frequency band as the frequency band of the band-pass filter, thereby obtaining a calibrated band-pass filter.

[0149] In this embodiment, preferably, the matrix including the geomagnetic direction cosine and its time derivative in the magnetic interference signal calculation module 320 is constructed as follows:

[0150]

[0151] In the formula, u i , i = 1, 2, 3 represent the geomagnetic direction cosine; u' i , i = 1, 2, 3 is the time derivative of u i , i = 1, 2, 3;

[0152] The calibration process of the compensation coefficient matrix includes:

[0153] Use the T-L model to construct the compensation coefficient matrix as follows:

[0154]

[0155] Wherein, p1, p2, and p3 respectively represent the components of the fixed magnetic field on the x, y, and z axes; All are interference coefficients to be solved;

[0156] Filter the two sets of calibrated measured magnetic field intensity data using a calibrated band-pass filter to obtain the calibrated environmental magnetic interference signal;

[0157] Subtract the calibrated environmental magnetic interference signal from the calibrated measured magnetic field intensity data to obtain the calibrated platform magnetic interference signal H I ;

[0158] Use the recursive least squares method to solve the following formula to obtain the compensation coefficient matrix θ:

[0159] H I = F × θ.

[0160] It should be noted that the functions of the near-field magnetic interference compensation system for a carrier platform based on gradient described in this embodiment can be illustrated by the aforementioned near-field magnetic interference compensation method for a carrier platform based on gradient. For the parts not detailed in this embodiment, refer to the above method embodiments.

[0161] It should be noted that although several units, modules, or sub-modules are mentioned in the above detailed description, this division is merely exemplary and not mandatory. In fact, according to the embodiments of the present invention, the features and functions of the two or more modules described above can be embodied in one module. Conversely, the features and functions of one module described above can be further divided and embodied by multiple modules.

[0162] In addition, although the operations of the method of the present invention are described in a specific order in the drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step for execution, and / or one step may be decomposed into multiple steps for execution.

[0163] Although the spirit and principles of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the specific embodiments disclosed, and the division of each aspect does not mean that the features in these aspects cannot be combined for benefit. This division is only for the convenience of expression. The present invention aims to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A gradient-based near-field magnetic interference compensation method for a carrier platform, characterized in that Including: Obtain two sets of magnetic field intensity data collected by a pair of magnetometers asymmetrically installed, where the magnetic field intensity data includes ambient magnetic interference signals, platform magnetic interference signals, and target magnetic field signals; among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of magnetic field intensity data are different; Obtain two sets of magnetic field direction data collected by a pair of fluxgate magnetometers asymmetrically installed; Filter the two sets of magnetic field intensity data using a calibrated band-pass filter to obtain ambient magnetic interference signals; Construct a matrix containing geomagnetic direction cosines and their time derivatives based on the magnetic field direction data; calculate the platform magnetic interference signals using the calibrated compensation coefficient matrix and the matrix containing geomagnetic direction cosines and their time derivatives; Subtract the ambient magnetic interference signals obtained after filtering and the calculated platform magnetic interference signals from the magnetic field intensity data to obtain the target magnetic field signals.

2. The method for compensating near-field magnetic interference of a gradient-based carrier platform according to claim 1, wherein The calibration process of the band-pass filter includes: Obtain two sets of calibrated measurement magnetic field intensity data collected by a pair of magnetometers asymmetrically installed, where the calibrated measurement magnetic field intensity data includes ambient magnetic interference signals and platform magnetic interference signals; among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of calibrated measurement magnetic field intensity data are different; Perform Fourier transforms on the two sets of calibrated measurement magnetic field intensity data respectively; Subtract and add the two sets of calibrated measurement magnetic field intensity data respectively, and perform Fourier transforms on the subtraction result and the addition result respectively; Determine two frequency intervals based on the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data, and the Fourier transform results of the subtraction result and the addition result; Take the intersection of the two frequency intervals as the frequency band of the ambient magnetic interference signal, and use this frequency band as the frequency band of the band-pass filter, thereby obtaining a calibrated band-pass filter.

3. A method for compensating near-field magnetic interference of a carrier platform based on gradient according to claim 2, characterized in that, The determination of the two frequency intervals based on the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data, and the Fourier transform results of the subtraction result and the addition result includes: The first frequency interval is: the frequency interval where the amplitudes and phases of the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data are the same and the amplitude of the Fourier transform result of the subtraction result is zero; The second frequency interval is: the frequency interval where the amplitudes and phases of the Fourier transform results of the two sets of calibrated measurement magnetic field intensity data are the same and the amplitude of the Fourier transform result of the addition result is twice the amplitude of the Fourier transform result of any one set of calibrated measurement magnetic field intensity data.

4. A method for compensating near-field magnetic interference of a carrier platform based on gradient, as claimed in claim 1, wherein The calibration process of the band-pass filter includes: Obtain two sets of calibrated measurement magnetic field intensity data collected by a pair of magnetometers asymmetrically installed, where the calibrated measurement magnetic field intensity data includes ambient magnetic interference signals and platform magnetic interference signals; among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of calibrated measurement magnetic field intensity data are different; Perform wavelet transforms on the two sets of calibrated measurement magnetic field intensity data respectively; Subtract and add the two sets of calibrated measurement magnetic field intensity data respectively, and perform wavelet transforms on the subtraction result and the addition result respectively; Determine two scale intervals based on the wavelet transform results of the two sets of calibrated measurement magnetic field intensity data, and the wavelet transform results of the subtraction result and the addition result; Take the intersection of two scale intervals as the scale interval of the environmental magnetic interference signal, and use this scale interval as the scale interval of the band-pass filter, thereby obtaining a calibrated band-pass filter.

5. A method for compensating near-field magnetic interference of a gradient-based carrier platform according to claim 4, characterized in that, Determining the two scale intervals based on the wavelet transform results of two sets of calibrated measured magnetic field intensity data, as well as the wavelet transform results of the difference result and the sum result, includes: The first scale interval is: the scale interval where the absolute values of the time coefficients in the wavelet transform results of the two sets of calibrated measured magnetic field intensity data are the same and the absolute values of the same time coefficients in the wavelet transform result of the difference result are zero; The second frequency interval is: the scale interval where the absolute values of the time coefficients in the wavelet transform results of the two sets of calibrated measured magnetic field intensity data are the same and the absolute values of the same time coefficients in the wavelet transform result of the sum result are twice the absolute values of the time coefficients in the wavelet transform result of any one set of calibrated measured magnetic field intensity data.

6. A gradient-based near-field magnetic interference compensation method for a carrier platform according to claim 3 or 5, characterized in that The matrix including the geomagnetic direction cosine and its time derivative is constructed as follows: where \(u\) i , \(i = 1, 2, 3\) represent the geomagnetic direction cosines; \(u'\) i , \(i = 1, 2, 3\) is the time derivative of \(u\) i , \(i = 1, 2, 3\).

7. A method for compensating near-field magnetic interference of a gradient-based carrier platform according to claim 6, characterized in that, The calibration process of the compensation coefficient matrix includes: Construct the compensation coefficient matrix using the T-L model as follows: wherein, p1, p2, and p3 respectively represent the components of the fixed magnetic field on the x, y, and z axes; i, j = 1, 2, 3, i, j = 1, 2, 3 are interference coefficients to be solved; Filter the two sets of calibrated measured magnetic field intensity data using the calibrated band-pass filter to obtain the calibrated environmental magnetic interference signal; Subtract the calibrated ambient magnetic interference signal from the calibrated measured magnetic field intensity data to obtain a calibrated platform magnetic interference signal H I ; Use the recursive least squares method to solve the following formula to obtain the compensation coefficient matrix θ: H I = F × θ.

8. A gradient-based near-field magnetic interference compensation system for a carrier platform, characterized in that, Including: A data acquisition module configured to acquire two sets of magnetic field intensity data collected by a pair of asymmetrically installed magnetometers, where the magnetic field intensity data includes environmental magnetic interference signals, platform magnetic interference signals, and target magnetic field signals; among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of magnetic field intensity data are different; acquire two sets of magnetic field direction data collected by a pair of asymmetrically installed fluxgates; A magnetic interference signal calculation module configured to filter the two sets of magnetic field intensity data using the calibrated band-pass filter to obtain the environmental magnetic interference signal; construct a matrix including the geomagnetic direction cosine and its time derivative based on the magnetic field direction data; calculate the platform magnetic interference signal using the calibrated compensation coefficient matrix and the matrix including the geomagnetic direction cosine and its time derivative; A magnetic interference compensation module configured to subtract the environmental magnetic interference signal obtained after filtering and the calculated platform magnetic interference signal from the magnetic field intensity data to obtain the target magnetic field signal.

9. The near-field magnetic interference compensation system for a gradient-based carrier platform according to claim 8, wherein, The calibration process of the band-pass filter in the magnetic interference signal calculation module includes: Acquire two sets of calibrated measured magnetic field intensity data collected by a pair of asymmetrically installed magnetometers, where the calibrated measured magnetic field intensity data includes environmental magnetic interference signals and platform magnetic interference signals; among them, the phases and amplitudes of the two sets of platform magnetic interference signals in the two sets of calibrated measured magnetic field intensity data are different; Perform Fourier transform on the two sets of calibrated measured magnetic field intensity data respectively; Subtract and add the two sets of calibrated measured magnetic field intensity data respectively, and perform Fourier transform on the difference result and the sum result respectively; Based on the Fourier transform results of two sets of calibrated measured magnetic field intensity data, as well as the Fourier transform results of the difference result and the sum result, two frequency intervals are determined; wherein, the two frequency intervals include: the first frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated measured magnetic field intensity data are the same and the amplitude in the Fourier transform result of the difference result is zero; the second frequency interval is: the frequency interval where the amplitudes and phases in the Fourier transform results of the two sets of calibrated measured magnetic field intensity data are the same and the amplitude in the Fourier transform result of the sum result is twice that of the Fourier transform result of any one set of calibrated measured magnetic field intensity data; Take the intersection of the two frequency intervals as the frequency band of the environmental magnetic interference signal, and use this frequency band as the frequency band of the band-pass filter, thereby obtaining a calibrated band-pass filter.

10. A near-field magnetic interference compensation system for a gradient-based carrier platform according to claim 9, characterized in that The matrix containing the geomagnetic direction cosine and its time derivative in the magnetic interference signal calculation module is constructed as follows: where \(u\) i , \(i = 1, 2, 3\) represent the geomagnetic direction cosines; \(u'\) i , \(i = 1, 2, 3\) is the time derivative of \(u\) i , \(i = 1, 2, 3\). The calibration process of the compensation coefficient matrix includes: Use the T-L model to construct the compensation coefficient matrix as follows: wherein, p1, p2, and p3 respectively represent the components of the fixed magnetic field on the x, y, and z axes; i, j = 1, 2, 3, i, j = 1, 2, 3 are interference coefficients to be solved; Use the calibrated band-pass filter to filter the two sets of calibrated measured magnetic field intensity data to obtain the calibrated environmental magnetic interference signal; Subtract the calibrated ambient magnetic interference signal from the calibrated measured magnetic field intensity data to obtain a calibrated platform magnetic interference signal H I ; Use the recursive least squares method to solve the following formula to obtain the compensation coefficient matrix θ: H I = F × θ.

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