A magnetic compensation method for a high-speed weak maneuvering motion platform

Abstract

The present application relates to the technical field of magnetic field precision measurement, and particularly relates to a magnetic compensation method of a high-speed weak maneuvering motion platform; step 1, at least four magnetic sensors are installed at a position with less magnetic interference in the internal space of a carrier; step 2, dynamic tests of magnetic interference of the carrier under various working conditions are carried out, and then a magnetic interference database of the carrier under various working conditions is constructed; step 3, initial parameters of a magnetic compensation model are determined; step 4, a more accurate eddy current magnetic field is obtained; step 5, after online iterative optimization, when the difference between the geomagnetic field value calculated by the time-varying magnetic compensation model and the geomagnetic field value calculated by the multi-point measurement data inversion algorithm is less than a set value (such as 1nT), a high-precision geomagnetic field is output. The problems of difficult modeling of a complex magnetic field environment in a cabin, difficult compensation of an eddy current interference field of a high-speed motion platform carrier, and difficult calibration of compensation model parameters caused by the limitation of the maneuvering capability of the carrier are solved.

Description

Technical Field

[0001] This invention relates to the field of precision magnetic field measurement technology, and specifically to a magnetic compensation method for a high-speed, low-maneuverability motion platform. Background Technology

[0002] Precise measurement of the geomagnetic field is fundamental to geomagnetic navigation and target detection. Its accuracy is mainly affected by the residual magnetic field, induced magnetic field, eddy current magnetic field, and other noise of the carrier. Taking a traditional airborne magnetic measurement platform as an example, the magnetic sensor is installed outside the carrier via a pod or extension rod. The magnetic interference at the sensor location is mainly caused by the residual magnetic field (generated by permanent magnet materials) and the induced magnetic field (generated by geomagnetic field induction), while the eddy current magnetic field (generated by metal cutting the geomagnetic field) is negligible. The compensation accuracy based on the TL model can reach 0.1 nT.

[0003] However, for high-speed, low-maneuverability vehicles (such as high-speed aircraft and underwater vehicles), magnetic compensation technology faces multiple challenges: ① Due to the aerodynamic or fluid structure limitations of the vehicle, magnetic sensors must be installed inside the vehicle's cabin, resulting in significant influence from residual magnetism, magnetic flux density, eddy currents, and electromagnetic interference from the equipment inside the cabin; ② During high-speed motion, the metal materials in the vehicle cut through the geomagnetic field, generating significant eddy current magnetic fields, which cannot be compensated for using the traditional TL model as "perturbations"; ③ To ensure the stability of the vehicle's high-speed motion, it is difficult to perform the maneuvers required by traditional magnetic compensation, making it impossible to obtain accurate TL compensation model parameters (such as residual magnetism coefficient and magnetic flux density); ④ Due to the high speed and long flight distance of the vehicle, the gradient and time-varying characteristics of the geomagnetic field are significant, affecting the accuracy of traditional magnetic compensation.

[0004] Existing magnetic compensation technology has significant limitations in high-speed, low-maneuverability vehicles: the effects of in-cabin magnetic interference, eddy current magnetic fields, and time-varying geomagnetic fields are enormous. Due to poor maneuverability, it is impossible to obtain accurate TL compensation model parameters, resulting in large magnetic field measurement errors or even the inability to obtain correct magnetic field data. Summary of the Invention

[0005] This invention provides a magnetic compensation method for a high-speed, low-maneuverability motion platform. Its objectives are twofold: firstly, by employing the Eulerian inversion method to perform multi-point gradient measurements, combined with a ground-based model learning algorithm, the location of the magnetic source is quickly determined, yielding the carrier's background magnetic field and thus an accurate geomagnetic field; secondly, based on the geomagnetic field model and initial compensation parameters obtained from ground tests, the magnetic compensation model parameters are first calibrated through low-maneuverability flight to obtain the carrier's magnetic interference field. Then, the carrier's interfering magnetic field is eliminated using a multi-point measurement data inversion algorithm, resulting in a more accurate geomagnetic field magnitude and direction. These parameters are then substituted into the magnetic compensation model to further optimize it. Finally, after online iterative optimization, a high-precision geomagnetic field is obtained. This method addresses the challenges of modeling complex in-cabin magnetic field environments, compensating for eddy current interference fields in high-speed motion platform carriers, and calibrating compensation model parameters due to limitations in carrier maneuverability.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] This invention provides a magnetic compensation method for a high-speed, low-maneuverability motion platform, comprising the following steps: Step 1: Install at least four magnetic sensors in a location with minimal magnetic interference inside the carrier. The four sensors must not be in the same plane. Simultaneously measure and provide the position matrix of each magnetic sensor in the carrier coordinate system. Step 2: At a test site with a small ground magnetic field gradient, conduct dynamic magnetic interference tests on the carrier under various working conditions. Through a multi-point measurement data inversion algorithm, establish the mapping relationship between the magnetic source distribution and the interference magnetic field, and then construct a magnetic interference database for the carrier under various working conditions. Finally, obtain the comprehensive distribution characteristics of the residual magnetic field, induced magnetic field and eddy current magnetic field inside the cabin. Step 3: Determine the initial parameters of the magnetic compensation model and construct a high-precision time-varying magnetic compensation model that considers the changes in the magnitude and direction of the geomagnetic field; Step 4: When the carrier performs the actual mission, firstly, the magnitude and direction of the initial geomagnetic field are determined using a geomagnetic field model (such as the IGRF model). Then, the magnetic compensation model parameters are calibrated through weak maneuvering flight to obtain the carrier's magnetic interference field. Next, combined with the established carrier magnetic interference database, a more accurate geomagnetic field magnitude and direction are calculated using a multi-point measurement data inversion algorithm. Finally, the result is substituted into the magnetic compensation model to further optimize the model parameters, thereby obtaining a more accurate eddy current magnetic field. Step 5: After online iterative optimization, when the difference between the geomagnetic field value calculated by the time-varying magnetic compensation model and the geomagnetic field value calculated by the multi-point measurement data inversion algorithm is less than 1nT, a high-precision geomagnetic field is output.

[0008] Furthermore, the various operating conditions in step 2 include power supply to and from the carrier equipment, changes in equipment operating conditions, and movement of the control surfaces.

[0009] Furthermore, the multi-point measurement data inversion algorithm described in step 2 specifically includes the following steps: Step 2.1, Establish the inversion model: For m magnetic sources, the Euler equation can be expressed as:

[0010] Step 2.2, Inversion parameter calculation: The corresponding coefficients are obtained by using the minimum variance method to determine the number and location of magnetic sources, and then the magnetic moment information of each magnetic source is calculated by combining the multi-magnetic dipole model.

[0011] Furthermore, step 3 specifically includes the following steps: Step 3.1, Initial Parameter Calculation: Based on the comprehensive magnetic interference field calculated point by point in Step 2, the initial parameters of the magnetic compensation model are obtained by combining the traditional TL model: The carrier magnetic interference and the measured values ​​of the magnetic sensor can be expressed as:

[0012] in, These are the initial parameters of the model to be solved. ; To determine the magnitude of magnetic interference on the carrier, the comprehensive magnetic interference field calculated point by point in step 2 can be used. The magnitude of the background geomagnetic field; Let be the direction cosines of the Earth's magnetic field along the three coordinate axes in the carrier's coordinate system, i.e.: ; Step 3.2, Construction of a high-precision time-varying magnetic compensation model: A high-precision time-varying magnetic compensation model considering the changes in the magnitude and direction of the geomagnetic field is constructed; the modeling method for the residual magnetic field and induced magnetic field is consistent with the traditional TL model, and the eddy current magnetic field modeling process considers the changes in the magnitude and direction of the geomagnetic field caused by the rapid movement of the high-speed platform; the magnetic sensor measurements in the carrier... The expression is:

[0013] In the formula, Remanence coefficient, The magnetic induction coefficient, is the eddy current coefficient.

[0014] Furthermore, the process of calibrating the magnetic compensation model parameters in step 4, which involves weak maneuvering flight, is combined with a high-precision time-varying magnetic compensation model for calculation. This process yields an accurate eddy current magnetic field.

[0015] The comprehensive magnetic interference field inside the cabin is obtained through a multi-point measurement data inversion algorithm, thereby obtaining an accurate geomagnetic field:

[0016] =

[0017] in, The comprehensive interference field obtained from the multi-point measurement data inversion algorithm is removed from the magnetic measurement data, thus obtaining the geomagnetic field value. This geomagnetic field value is then used as the basis for the high-precision time-varying magnetic compensation model formula. .

[0018] The beneficial effects achieved by this invention are as follows: This invention employs a multi-sensor (≥4) magnetic field measurement system. By improving the traditional TL magnetic compensation model and performing online iterative optimization with a multi-point measurement data inversion algorithm, it solves problems such as the difficulty in modeling complex magnetic field environments inside cabins, the difficulty in compensating for eddy current interference fields on high-speed moving platforms, and the difficulty in calibrating compensation model parameters due to the limited maneuverability of the platform. It can be applied to multiple high-speed moving platforms in aerospace, aviation, ground, and underwater applications, promoting the development of applications in space magnetic surveying, geomagnetic navigation, target detection, and other fields. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is an example diagram showing the arrangement of magnetic sensors.

[0021] Figure 2 This describes the technical process for precise measurement of the magnetic field of a high-speed, low-mobility platform.

[0022] Figure 3 The input and output block diagram is shown for the multi-point measurement data inversion algorithm. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0025] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, if the word "and / or" appears throughout the text, it means including three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0026] To address the problems of existing technologies, this invention proposes a precise measurement method for the magnetic field of a carrier suitable for high-speed, low-maneuverability platforms. Its main innovations lie in the following two aspects: First, because the carrier's background magnetic field differs from the Earth's magnetic field, exhibiting characteristics of near-magnetic source and multi-point coupling, resulting in a significant magnetic field gradient, this invention employs the Euler inversion method for multi-point gradient measurement, combined with a ground-based model learning algorithm, to quickly determine the location of the magnetic source, obtain the carrier's background magnetic field caused by the magnetic source, and thus obtain a precise Earth's magnetic field. Second, due to the high speed, long flight distance, and limited maneuverability of high-speed motion platforms, which cannot perform complete maneuvering flights to obtain magnetic compensation parameters, this invention proposes an online optimization method for magnetic compensation parameters under low-maneuverability conditions. Based on the Earth's magnetic field model and initial compensation parameters obtained from ground tests, the magnetic compensation model parameters are first calibrated through low-maneuvering flight to obtain the carrier's magnetic interference field. Then, a multi-point measurement data inversion algorithm is used to eliminate the carrier's interfering magnetic field, obtaining a more accurate magnitude and direction of the Earth's magnetic field. These parameters are then substituted into the magnetic compensation model for further optimization. Finally, after online iterative optimization, a high-precision Earth's magnetic field is obtained.

[0027] like Figures 1-3 As shown, this invention provides a magnetic compensation method for a high-speed, low-maneuverability motion platform, specifically including the following steps: Step 1: Install at least four magnetic sensors in locations with minimal magnetic interference within the carrier's internal space (i.e., the spatial distance from each major magnetic interference source on the platform is greater than 20cm; the major magnetic interference sources refer to those with magnetic field strength greater than (supplementary) magnetic interference sources). The four sensors must not be in the same plane; the position matrix of each magnetic sensor in the carrier's coordinate system must be measured simultaneously. See [link to magnetic sensor installation method] for details. Figure 1 .

[0028] Step 2: In a test site with a small ground magnetic field gradient (i.e., geomagnetic field gradient ≤ 1nT / m), conduct dynamic magnetic interference tests on the carrier under various operating conditions (such as power-on / off of carrier equipment, changes in equipment operating conditions, and control surface movements). Through a multi-point measurement data inversion algorithm, establish the mapping relationship between magnetic source distribution and interference magnetic field, and then construct a magnetic interference database for various operating conditions of the carrier. Finally, obtain the comprehensive residual magnetic field, induced magnetic field, and eddy current magnetic field distribution characteristics inside the cabin.

[0029] (1) Establishing an inversion model

[0030] The magnetic field outside the source satisfies Laplace's equations. When the magnetic field generated by the source is an Nth-order homogeneous equation, then this Nth-order homogeneous equation also satisfies Euler's equations. Suppose there are two magnetic sources as the source, then Euler's equations can be written as:

[0031]

[0032]

[0033] in, For the coordinates of the measurement point, , Let be the coordinates of the two magnetic sources. As the background magnetic field, , Let N be the electric field strength generated by the magnetic source, and N be the order of the homogeneous equation. Let be the gradient operator. The total electric field intensity produced by the magnetic source at the measurement point can be obtained from the Euler equation above:

[0034] Magnetic field at the sourceless point (i.e., the measurement point) Satisfies the Laplace equation: ,use When installing a magnetic sensor, the gradient value of any measurement point can be obtained by direct measurement.

[0035] For m magnetic sources, Euler's equations can be expressed as:

[0036] in, Represents integers from 0 to m. The recursive variables are derived from the number and location of the magnetic sources. Let be the gradient operator for the k-th magnetic source.

[0037] (2) Inversion parameter solution

[0038] The corresponding coefficients are obtained by using the minimum variance method to determine the number and location of magnetic sources. Then, the magnetic moment information of each magnetic source can be calculated by combining it with the multi-magnetic dipole model.

[0039] Step 3: Determine the initial parameters of the magnetic compensation model and construct a high-precision time-varying magnetic compensation model that considers the changes in the magnitude and direction of the geomagnetic field.

[0040] (1) Calculation of initial parameters

[0041] Based on the magnetic source location and magnetic moment information calculated in step 2, the comprehensive magnetic interference field can be obtained, and the initial parameters of the magnetic compensation model can be obtained by combining them with the traditional TL model:

[0042] The carrier magnetic interference and the measured values ​​of the magnetic sensor can be expressed as:

[0043]

[0044] in, These are the initial parameters of the model to be solved. ; To determine the magnitude of magnetic interference on the carrier, the comprehensive magnetic interference field calculated point by point in step 2 can be used. The magnitude of the background geomagnetic field; Let be the direction cosines of the Earth's magnetic field along the three coordinate axes in the carrier's coordinate system, i.e.: .

[0045] in, The direction cosine, Let be the derivative of the direction cosine.

[0046] (2) Construction of high-precision time-varying magnetic compensation model

[0047] A high-precision time-varying magnetic compensation model considering the changes in the magnitude and direction of the geomagnetic field is constructed. The modeling method for the residual magnetic field and the induced magnetic field is consistent with the traditional TL model, and the eddy current magnetic field modeling process considers the changes in the magnitude and direction of the geomagnetic field caused by the rapid motion of the high-speed platform.

[0048] Based on the mathematical model of eddy current magnetic field, the eddy current magnetic field in the carrier coordinate system It can be represented as:

[0049] In the formula, EC is the eddy current parameter matrix of the eddy current magnetic field model, and the eddy current coefficient is... It depends only on the material properties and size of the carrier, as well as the installation location of the magnetic sensor. , , The geomagnetic field vector The derivatives of the three components in the carrier coordinate system, namely the rate of change of the eddy current magnetic field and the components of the geomagnetic field, are related.

[0050] The rates of change of the three axial components of the Earth's magnetic field are as follows:

[0051] Therefore, the eddy current magnetic field can be written as:

[0052] in,

[0053] In the formula, The geomagnetic gradient along the trajectory of the carrier. For the speed of the carrier, It is a quantity related to the magnitude of the geomagnetic field and the geomagnetic gradient of the trajectory.

[0054] The complete expression for the eddy current magnetic field, considering the variations in the magnitude and direction of the Earth's magnetic field, is:

[0055] Magnetic sensor measurement value in carrier The expression is:

[0056]

[0057] In the formula, Remanence coefficient, The magnetic induction coefficient, is the eddy current coefficient.

[0058] In the formula, The remaining magnetic field; To induce a magnetic field.

[0059] Step 4: When the carrier performs the actual mission, firstly, the magnitude and direction of the initial geomagnetic field are determined using a geomagnetic field model (such as the IGRF model). Then, the magnetic compensation model parameters are calibrated through weak maneuvering flight to obtain the carrier's magnetic interference field. Next, combined with the established carrier magnetic interference database, a more accurate geomagnetic field magnitude and direction are calculated using a multi-point measurement data inversion algorithm. Finally, the result is substituted into the magnetic compensation model to further optimize the model parameters, thereby obtaining a more accurate eddy current magnetic field.

[0060] (1) The process of calibrating the magnetic compensation model parameters for weak maneuvering flight is combined with the solution of a high-precision time-varying magnetic compensation model. This process can obtain a relatively accurate eddy current magnetic field:

[0061] (2) The comprehensive magnetic interference field inside the cabin is calculated by using a multi-point measurement data inversion algorithm, thereby obtaining a more accurate geomagnetic field:

[0062] =

[0063] in, The comprehensive interference field obtained from the multi-point measurement data inversion algorithm is removed from the magnetic measurement data, thus obtaining the geomagnetic field value. This geomagnetic field value is then used as the basis for the high-precision time-varying magnetic compensation model formula. .

[0064] Step 5: After online iterative optimization, when the difference between the geomagnetic field value calculated by the time-varying magnetic compensation model and the geomagnetic field value calculated by the multi-point measurement data inversion algorithm is less than the set value (e.g., 1nT, which varies depending on the motion platform and is determined by empirical values), a high-precision geomagnetic field is output.

[0065] The above description is merely a typical application example of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in various ways. For example, the present invention can be applied to aviation platforms and can also achieve magnetic compensation for aerospace, ground, and underwater platforms. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnetic compensation method for a high-speed, low-maneuverability motion platform, characterized in that, Includes the following steps: Step 1: Install at least four magnetic sensors in a location with minimal magnetic interference inside the carrier. The four sensors must not be in the same plane. Simultaneously measure and provide the position matrix of each magnetic sensor in the carrier coordinate system. Step 2: At a test site with a small ground magnetic field gradient, conduct dynamic magnetic interference tests on the carrier under various working conditions. Through a multi-point measurement data inversion algorithm, establish the mapping relationship between the magnetic source distribution and the interference magnetic field, and then construct a magnetic interference database for the carrier under various working conditions. Finally, obtain the comprehensive distribution characteristics of the residual magnetic field, induced magnetic field and eddy current magnetic field inside the cabin. Step 3: Determine the initial parameters of the magnetic compensation model and construct a high-precision time-varying magnetic compensation model that considers the changes in the magnitude and direction of the geomagnetic field; Step 4: When the carrier performs the actual mission, firstly, the magnitude and direction of the initial geomagnetic field are determined by using the geomagnetic field model. Then, the magnetic compensation model parameters are calibrated by weak maneuvering flight to obtain the carrier's magnetic interference field. Next, combined with the established carrier magnetic interference database, a more accurate geomagnetic field magnitude and direction are calculated using a multi-point measurement data inversion algorithm. Finally, the result is substituted into the magnetic compensation model to further optimize the model parameters, thereby obtaining a more accurate eddy current magnetic field. Step 5: After online iterative optimization, when the difference between the geomagnetic field value calculated by the time-varying magnetic compensation model and the geomagnetic field value calculated by the multi-point measurement data inversion algorithm is less than the set value, a high-precision geomagnetic field is output. The multi-point measurement data inversion algorithm described in step 2 specifically includes the following steps: Step 2.1, Establish the inversion model: For m magnetic sources, the Euler equation can be expressed as: in, Let the order of the homogeneous equation be . The number of magnetic sources The recursive variables are derived from the number and location of the magnetic sources. Let r be the gradient operator for the r-th magnetic source. As the background magnetic field, This represents the total magnetic field generated by the magnetic source at the measurement location; Step 2.2, Inversion parameter calculation: The corresponding coefficients are obtained by using the minimum variance method to determine the number and location of magnetic sources, and then the magnetic moment information of each magnetic source is calculated by combining the multi-magnetic dipole model; In addition, step 3 specifically includes the following steps: Step 3.1, Initial Parameter Calculation: Based on the comprehensive magnetic interference field calculated point by point in Step 2, the initial parameters of the magnetic compensation model are obtained by combining the traditional TL model: The carrier magnetic interference and the measured values ​​of the magnetic sensor can be expressed as: in, These are the initial parameters of the model to be solved. ; To determine the magnitude of magnetic interference on the carrier, the comprehensive magnetic interference field calculated point by point in step 2 can be used. The magnitude of the background geomagnetic field; Let be the direction cosines of the Earth's magnetic field along the three coordinate axes in the carrier's coordinate system. ,Right now: X, Y, and Z are the angles between the Earth's magnetic field and the three coordinate axes in the carrier's coordinate system. The derivative of the direction cosine; Step 3.2, Construction of a high-precision time-varying magnetic compensation model: A high-precision time-varying magnetic compensation model considering the changes in the magnitude and direction of the geomagnetic field is constructed; the eddy current magnetic field modeling process considers the changes in the magnitude and direction of the geomagnetic field caused by the rapid movement of the high-speed platform; the magnetic sensor measurements in the carrier... The expression is: In the formula, Remanence coefficient, ; The magnetic induction coefficient, ; The eddy current coefficient is... ; This represents the true value of the Earth's magnetic field. For carrier remanence, To induce a magnetic field in the carrier, The carrier eddy current magnetic field is given by v, where v is the carrier velocity; k = g / To the magnitude of the Earth's magnetic field The quantity related to the geomagnetic gradient g in the direction of the carrier's trajectory, where g is the geomagnetic gradient in the direction of the carrier's trajectory.

2. The magnetic compensation method for a high-speed, low-maneuverability motion platform according to claim 1, characterized in that: The various operating conditions in step 2 include power supply to and from the carrier equipment, changes in equipment operating conditions, and movement of the control surfaces.

3. The magnetic compensation method for a high-speed, low-maneuverability motion platform according to claim 1, characterized in that, Step 4, the process of calibrating the magnetic compensation model parameters during weak maneuvering flight, is combined with the high-precision time-varying magnetic compensation model for calculation. This process yields an accurate eddy current magnetic field. The comprehensive magnetic interference field inside the cabin is obtained through a multi-point measurement data inversion algorithm, thereby obtaining an accurate geomagnetic field: = in, The comprehensive interference field obtained from the multi-point measurement data inversion algorithm is removed from the magnetic measurement data, thus obtaining the geomagnetic field value. This geomagnetic field value is then used as the basis for the high-precision time-varying magnetic compensation model formula. B E1 To obtain a more accurate eddy current magnetic field by combining the parameters of the magnetic compensation model calibrated through weak maneuvering flight with the solution of a high-precision time-varying magnetic compensation model, B E2 To obtain a more accurate geomagnetic field by subtracting the comprehensive magnetic interference field inside the cabin from the measurement value of the magnetic sensor.

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