Weak magnetic moment repeated measurement system and repeated measurement method

Abstract

The invention discloses a weak magnetic moment repeated measurement system and a weak magnetic moment repeated measurement method, belongs to the technical field of magnetic moment measurement, and solves the problems of various defects and high-precision measurement requirements of an existing weak magnetic moment measurement method. According to the method, a to-be-measured material is made to reciprocate through a simple pendulum, a vector magnetic field is measured through a magnetic sensor array, a magnetic gradient tensor and related components are calculated, a superposed component image is analyzed to determine a time point, and finally a magnetic moment result is obtained through an inversion algorithm. The weak magnetic moment repeated measurement method is provided, materials are not magnetized, the measurement result is accurate, the speed is high, multiple times of measurement can be completed in about 3 minutes, the standard deviation is small, the precision is about 0.1%, and high-precision measurement is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic moment measurement, and in particular to a weak magnetic moment repeated measurement system and a repeated measurement method. Background Art

[0002] Due to structural and performance requirements, spacecraft need to use certain hard magnetic materials and soft magnetic materials; in addition, there are multiple current loops when the spacecraft is operating. The existence of hard magnetic materials, soft magnetic materials and current loops makes each spacecraft component magnetic. The magnetic properties of materials can be quantified by magnetic moment. During on-orbit operation, due to the interaction between the space magnetic field and the magnetic moment of spacecraft components, the orbit and attitude of the spacecraft will be changed. Therefore, in order not to affect the spacecraft attitude, more and more stringent requirements are put forward for the magnetic moments of each spacecraft component.

[0003] In addition, space gravitational wave detection is another typical scenario that strictly requires the magnetic moments of spacecraft components. Gravitational wave detection is an important means to observe cosmic events and reveal the origin of the universe, and is one of the most important frontiers in contemporary physics. Space gravitational wave detection satellites can detect gravitational waves in the frequency band of 0.1 mHz to 1 Hz. This frequency band of gravitational waves contains rich information on astrophysical sources, including the early structure and evolution of the universe. Many countries have implemented space gravitational wave detection programs, such as the "LISA program" led by the European Space Agency and the "DECIGO program" of Japan. Among them, the "LISA" program is listed as one of the top-level tasks in the "Cosmic Vision Decade Program (2015 - 2025)" of the European Space Agency. In the space gravitational wave detection mission, it is necessary to use inertial sensors and laser interferometry systems to achieve displacement measurements at the pm level at satellite formation distances of hundreds of thousands to millions of kilometers. The test mass is the core component of the inertial sensor, which is made of gold and platinum uniformly mixed in a certain ratio into a cube shape with a side length of about 5 cm and a mass of about 2 kg. The magnetic interference generated by the interaction between the magnetic moment of the test mass and the space magnetic field is one of the main sources of acceleration noise. In order to suppress this noise source, it is usually required that the magnetic moment of the test mass does not exceed 20 nA·m2, which is equivalent to the magnetic moment of 1 μg of ferromagnetic particles. The precise measurement of the magnetic moment of the test mass is of great significance for controlling the acceleration noise generated by the magnetic torque and is an important technical support for space gravitational wave detection.

[0004] While the requirements for the magnetic moments of spacecraft components are becoming more and more stringent, higher demands are put forward for the high-precision measurement of weak magnetic moments. The precision of commercially available vibrating sample magnetometers for measuring magnetic moments can reach 0.05 nA·m2, but they are only applicable to samples in the gram range. For the magnetic moments of materials in the kilogram range such as spacecraft components, there are mainly two measurement methods: the mechanical method and the magnetic method.

[0005] The principle of the mechanical method is as follows: A coil is used to generate an excitation magnetic field in the order of mT, and the torque generated by the interaction between the magnetic field and the material to be measured is measured. The magnetic moment is inversely obtained according to the mechanical formula. Research institutions at home and abroad mainly use a high-sensitivity torsion pendulum device to measure the torque and obtain good measurement results. However, this method has many disadvantages: the measurement results are affected by the fluctuation of the geomagnetic field; the excitation magnetic field will magnetize the material to be measured, resulting in inaccurate measurement results; the measurement period is long, about two weeks.

[0006] The principle of the magnetic method is as follows: A magnetic sensor array is used to measure the magnetic field distribution generated by the material to be measured in space, and the magnetic moment is inversely obtained by using the mathematical relationship between the magnetic moment and the magnetic field distribution. Research institutions at home and abroad generally measure the vector magnetic field of the material to be measured under the geomagnetic field and use an optimization algorithm to solve the nonlinear equation to obtain the magnetic moment. Due to the instability and inhomogeneity of the geomagnetic field, the measurement precision of this method will be seriously affected. In addition, the existing research realizes the repeated measurement of the magnetic moment through a motor. The motor will introduce additional magnetic interference, which will further affect the magnetic moment measurement. Summary of the Invention

[0007] The present invention proposes a weak magnetic moment repeated measurement system and a repeated measurement method to solve the defects existing in the existing mechanical method and magnetic method when measuring weak magnetic moments, such as being affected by the geomagnetic field, magnetizing the material to be measured, having a long measurement period, and the motor introducing magnetic interference, and to meet the urgent needs for high-precision measurement of weak magnetic moments in spacecraft components and space gravitational wave detection, etc.

[0008] A weak magnetic moment repeated measurement system, the weak magnetic moment repeated measurement system includes a material to be measured, a magnetic shielding device, a simple pendulum, a non-magnetic support platform, a magnetic sensor array, and a data acquisition and operation system. The simple pendulum, the material to be measured, the non-magnetic support platform, and the magnetic sensor array are all arranged inside the magnetic shielding device.

[0009] Among them, the magnetic sensor array is arranged on the upper surface of the non-magnetic support platform, the material to be measured is suspended at the lower end of the simple pendulum and is always located on the side of the magnetic sensor array. The signal output end of the magnetic sensor array is signal-connected to the signal input end of the data acquisition and operation system.

[0010] Before the simple pendulum is released, the initial position of the material to be measured is on the same horizontal line as the magnetic sensor array.

[0011] Further, the material to be measured is used to make reciprocating motion with the simple pendulum and generate a magnetic field through its own magnetic characteristics, serving as the object measured by the magnetic sensor array;

[0012] The magnetic shielding device is used to shield environmental magnetic interference and reduce the influence of external magnetic fields on the measurement process;

[0013] The simple pendulum is used to make the material to be measured perform reciprocating motion so that the magnetic sensor array can measure the magnetic field distribution of the material to be measured at different positions.

[0014] A non-magnetic support platform for placing the magnetic sensor array at a specified height;

[0015] A magnetic sensor array for measuring the magnetic field vector data of a material under test during movement;

[0016] A data acquisition and operation system, built-in with data acquisition and inversion algorithms, for converting the analog signal of the magnetic field vector data output by the magnetic sensor array into a digital signal, calculating the magnetic moment vector, and obtaining the inversion result of the magnetic moment of the material under test.

[0017] Further, the magnetic shielding device is a cubic cavity, and the length L of the pendulum is 1 / 3 to 2 / 3 of the side length of the magnetic shielding device.

[0018] Further, the magnetic shielding device is a cubic cavity, and the number of movement periods of the pendulum is 30 to 70.

[0019] Further, the frequency f of magnetic field data acquisition d ≥200f b .

[0020] A method for repeated measurement of weak magnetic moment, applied to the above-mentioned weak magnetic moment repeated measurement system, the method for repeated measurement of weak magnetic moment includes the following steps:

[0021] S1. Use a pendulum to make the material under test move back and forth, and use a magnetic sensor array to measure the vector magnetic field;

[0022] S2. Calculate the magnetic gradient tensor G through the magnetic field vector measurement data of each magnetic sensor in the magnetic sensor array, and calculate the independent components of the magnetic gradient tensor G;

[0023] S3. Calculate the superposition component G plus through the independent components of the magnetic gradient tensor G, and obtain the time points corresponding to the nearest distance and the farthest distance within each pendulum period through the obtained variation image G plus (t) of G; plus (t);

[0024] S4. Obtain the magnetic field vector and magnetic gradient tensor generated by the material under test, and obtain the inversion result of the magnetic moment through the inversion algorithm.

[0025] A storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the above-mentioned method for repeated measurement of weak magnetic moment is implemented.

[0026] A computer device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor executes the program to implement the above-mentioned method for repeated measurement of weak magnetic moment.

[0027] Compared with the prior art, the beneficial effects of the present invention include the following aspects:

[0028] (1) The present invention proposes a method for repeated measurement of weak magnetic moments, which will not magnetize the material to be measured. The measurement result is accurate and the measurement speed is fast. It can complete multiple repeated measurements of the weak magnetic moment of the material in about 3 minutes.

[0029] (2) The present invention proposes a method for repeated measurement of weak magnetic moments. For the material to be measured with a magnetic moment of 20 nA·m 2 , the standard deviations of the measurement results of the magnetic moment components m x , m y and m z are 0.206 nA·m 2 , 0.207 nA·m 2 and 0.228 nA·m 2 respectively, and the measurement precision is about 0.1%, realizing high-precision measurement of weak magnetic moments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic structural diagram of a system for repeated measurement of weak magnetic moments of the present invention;

[0031] Figure 2 is an array structure for measuring the magnetic gradient tensor, where Figure 2 (a) is an equilateral triangle array structure; Figure 2 (b) is a cross-shaped array structure; Figure 2 (c) is a square array structure; Figure 2 (d) is a regular tetrahedron array structure;

[0032] Figure 3 is the calculation result of the independent component in the first period;

[0033] Figure 4 is the calculation result of G plus in the first period;

[0034] Figure 5 is the measurement result of the material magnetic moment vector. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Refer to Figure 1As shown in the figure, a weak magnetic moment repeated measurement system, the weak magnetic moment repeated measurement system includes a material to be measured, a magnetic shielding device, a pendulum, a non-magnetic support platform, a magnetic sensor array and a data acquisition and calculation system. The pendulum, the material to be measured, the non-magnetic support platform and the magnetic sensor array are all arranged inside the magnetic shielding device.

[0037] Among them, the magnetic sensor array is arranged on the upper surface of the non-magnetic support platform. The material to be measured is suspended at the lower end of the pendulum and is always located on the side of the magnetic sensor array. The signal output end of the magnetic sensor array is signal-connected to the signal input end of the data acquisition and calculation system.

[0038] Before the pendulum is released, the initial position of the material to be measured is on the same horizontal line as the magnetic sensor array.

[0039] Specifically, in the present invention, by arranging the pendulum, the material to be measured, the non-magnetic support platform and the magnetic sensor array inside the magnetic shielding device, environmental magnetic interference can be effectively shielded, the accuracy and stability of the measurement can be improved, and the influence of the external magnetic field on the measurement result can be reduced. Before the pendulum is released, the initial position of the material to be measured is on the same horizontal line as the magnetic sensor array, which helps to maintain the consistency and standardization of the measurement conditions during the measurement process and further improve the measurement accuracy.

[0040] Further, the material to be measured is used to make reciprocating motion with the pendulum and generate a magnetic field through its own magnetic characteristics, serving as the object measured by the magnetic sensor array.

[0041] The magnetic shielding device is used to shield environmental magnetic interference and reduce the influence of the external magnetic field on the measurement process.

[0042] The pendulum is used to make the material to be measured perform reciprocating motion so that the magnetic sensor array can measure the magnetic field distribution of the material to be measured at different positions.

[0043] The non-magnetic support platform is used to place the magnetic sensor array at a specified height.

[0044] The magnetic sensor array is used to measure the magnetic field vector data of the material to be measured during the motion process.

[0045] The data acquisition and calculation system is built-in with data acquisition and inversion algorithms, which are used to convert the analog signal of the magnetic field vector data output by the magnetic sensor array into a digital signal and calculate the magnetic moment vector to obtain the inversion result of the magnetic moment of the material to be measured.

[0046] Specifically, the material to be measured, as the measurement object, can stably generate a magnetic field following the movement of the pendulum, ensuring the basic conditions for measurement. The magnetic shielding device effectively excludes external magnetic field interference, greatly improving the measurement accuracy and reliability and creating a stable environment for precise measurement. The reciprocating motion design of the pendulum enables the magnetic sensor array to obtain the magnetic field distribution data of the material to be measured at different positions, enriching the measurement information. The non-magnetic support platform ensures that the magnetic sensor array is at an appropriate height. The magnetic sensor array can accurately measure the magnetic field vector data, providing key raw data for subsequent calculations. The data acquisition and operation system converts the analog signal into a digital signal and accurately calculates the magnetic moment vector through its built-in algorithm, realizing the automation and intelligence of the measurement process and improving the measurement efficiency and accuracy. The present invention highly integrates the functions of each component and clearly defines the division of labor. In particular, the cooperation between the magnetic shielding device, the pendulum and other components, as well as the application of the algorithm in the data acquisition and operation system, effectively solves the problems of multiple interferences, inaccurate measurement, and complex calculation faced in traditional weak magnetic moment measurement.

[0047] Further, the magnetic shielding device is a cube cavity, and the length L of the pendulum is 1 / 3 to 2 / 3 of the side length of the magnetic shielding device.

[0048] Further, the magnetic shielding device is a cube cavity, and the number of movement cycles of the pendulum is 30 to 70.

[0049] Further, the frequency f of magnetic field data acquisition d ≥200f b 。

[0050] A weak magnetic moment measurement repeated measurement method is applied to the above-mentioned weak magnetic moment repeated measurement system. The weak magnetic moment measurement repeated measurement method includes the following steps:

[0051] S1. Use the pendulum to make the material to be measured perform reciprocating motion, and use the magnetic sensor array to measure the vector magnetic field;

[0052] S2. Calculate the magnetic gradient tensor G through the magnetic field vector measurement data of each magnetic sensor in the magnetic sensor array, and calculate the independent components of the magnetic gradient tensor G;

[0053] S3. Calculate the superimposed component G plus through the independent components of the magnetic gradient tensor G, and obtain the time points corresponding to the closest distance and the farthest distance within each pendulum period by obtaining the variation image G plus (t) of G; plus S4. Obtain the magnetic field vector and magnetic gradient tensor generated by the material to be measured, and obtain the inversion result of the magnetic moment through the inversion algorithm.

[0054]

[0055] ​Specifically, in S1, the material to be measured is fixed on a simple pendulum with a length of L, and the swing angle of the simple pendulum is α. It is recommended that L be between 1 / 3 and 2 / 3 of the side length of the magnetic shielding device. The maximum displacement s of the material to be measured in the horizontal direction can be calculated as follows: max is:

[0056] s max = 2Lsinα (1)

[0057] It is recommended that s max be between 0.5 m and 1 m, and the swing angle α is selected according to this range. Before the simple pendulum is released, the position of the material to be measured is called the initial position. The magnetic sensor array is on the same horizontal line as the initial position of the material to be measured. It is necessary to ensure that during the reciprocating motion, the material to be measured is always on one side of the magnetic sensor array, and there is no mechanical interference between the two. The motion frequency f of the simple pendulum b is:

[0058]

[0059] Release the simple pendulum, and use the magnetic sensor array to record the magnetic field vector data during the motion of the material to be measured. It is recommended that the data acquisition frequency f d ≥ 200f b . It is recommended that the number of motion cycles of the simple pendulum be between 30 and 70 to avoid excessive attenuation of the swing amplitude of the simple pendulum;

[0060] In S2, after obtaining the magnetic field vector measurement data of each magnetic sensor, the magnetic gradient tensor G is calculated using the difference method. G is the gradient of the magnetic field vector B in three spatial directions and is a 3×3 matrix:

[0061]

[0062] In the detection area without spatial current density, the divergence and curl of the magnetic field are both 0, and the magnetic gradient tensor G has symmetry and tracelessness, that is:

[0063]

[0064] G xx , G xy , G xz , G yy , G yz are called the independent components of G. The calculation formula of G is different for different magnetic sensor array structures. The magnetic sensor array structures used to measure G mainly include square, cross, triangle, and regular tetrahedron, etc., as shown in Figure 2 .

[0065] In this embodiment, taking the square array structure as an example, the calculation formula of the independent component G xx is shown in (5), and the calculation formulas of the other 4 independent components are similar to it.

[0066]

[0067] In the formula, D x is the baseline distance of the magnetic sensor array, is the x-axis magnetic field data of the magnetic sensor S i ;

[0068] S3. Calculate the superposition component G plus using formula (6):

[0069] G plus = G xx + G xy + G xz + G yy + G yz (6)

[0070] Within each pendulum period T, obtain the variation image of G plus with time G plus (t). When G plus (t) reaches the maximum value, the distance between the magnetic sensor array and the material to be measured is the closest. After half a pendulum period, the distance between the magnetic sensor array and the material to be measured is the closest. Therefore, the time point t min corresponding to the closest distance and the time point t max corresponding to the farthest distance can be obtained from the following formula:

[0071]

[0072] S4. In the magnetic field vector sum and the magnetic gradient tensor G in S1 and S2, it includes not only those generated by the material to be measured, but also those existing in the environment itself. By subtracting the magnetic field vector data at the time point t min corresponding to the closest distance from the magnetic field vector data at the time point t max corresponding to the closest distance, the magnetic field vector generated by the material to be measured can be obtained. Then, use the calculation formula of the magnetic gradient tensor to obtain the magnetic gradient tensor generated by the material to be measured.

[0073] When the measurement distance is more than 3 times its own size, the material to be measured can be regarded as a magnetic dipole. According to the magnetic dipole model, the tensor component G ij (i = x, y, z, j = x, y, z) generated by the material to be measured is:

[0074]

[0075] In the formula, μ 0 is the vacuum magnetic permeability, with a value of 4π×10 -7 T·m / A; m is the magnetic moment vector of the material to be measured; r is the position vector of the material to be measured, pointing from the measurement point to the material to be measured; r is the modulus of r; ri (i = x, y, z), r j (j = x, y, z) are the three-axis components of r; m i , m j are the three-axis components of m; δ ij is the Kronecker function.

[0076] After obtaining the position vector r of the material to be measured using the inversion algorithm, the calculation formula for the magnetic moment vector m can be obtained according to formula (8):

[0077]

[0078] In the formula, x 0 , y 0 , z 0 are the three-axis components of the position vector r.

[0079] A storage medium stores a computer program thereon, and when the computer program is executed by a processor, the above-mentioned method for repeated measurement of weak magnetic moment is implemented.

[0080] Specifically, the storage medium of the present invention stores the method for repeated measurement of weak magnetic moment in the form of a computer program, and has many beneficial effects when executed by a processor. It has portability and convenience, can be easily used in different computer systems, and is conducive to the popularization of technology. At the same time, it can automate the measurement process, reduce manual operation errors, and ensure the repeatability and stability of the measurement results. In addition, the computer program can quickly and accurately process a large amount of measurement data, ensure the efficiency of the measurement process and the accuracy of the results, and can also adjust and optimize the parameters in the measurement process, improve the flexibility and adaptability of the measurement method, and also realize the automation and integration of data processing, bringing many conveniences to the measurement process.

[0081] A computer device includes: a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor executes the program to implement the above-mentioned method for repeated measurement of weak magnetic moment.

[0082] Specifically, the computer device of the present invention stores the weak magnetic moment measurement repeated measurement method in the memory, and the processor runs the corresponding program, bringing many advantages to the measurement of weak magnetic moments. First, integrating the measurement process into the computer device realizes automated operation, greatly reducing errors in the manual operation process and making the measurement process more accurate and reliable. Second, the computer device can quickly process data according to the program, and can efficiently complete a series of complex operations from magnetic field vector measurement to magnetic moment inversion result calculation, improving the measurement efficiency. Moreover, with this device, the repeatability of the measurement is well guaranteed, ensuring that each measurement follows a unified program flow. Furthermore, it provides an integrated platform that integrates various functions and algorithms required for weak magnetic moment measurement, making the entire measurement process more standardized and systematic, and enabling the measurement task to be completed in a relatively stable environment, avoiding errors caused by environmental and human factors in different measurement links. Finally, its convenient storage and processing functions also facilitate subsequent data analysis, result storage, and improvement of the measurement method, contributing to in-depth mining of measurement data and further research, and promoting the development and improvement of weak magnetic moment measurement technology.

[0083] The following is a specific embodiment of the present invention:

[0084] Use Matlab software to perform analytical modeling of the magnetic moment measurement of materials to verify the effectiveness of the present invention. In the analytical model, the material is regarded as a magnetic dipole, and the magnetic moment magnitude is 20 nA·m 2 , and the magnetic moment components m x , m y , and m z are 8.66 nA·m 2 , 15 nA·m 2 , and 10 nA·m 2 respectively. The following are the specific implementation steps:

[0085] (1) Use a pendulum to make the material to be measured move back and forth, and use a magnetic sensor array to measure the vector magnetic field.

[0086] The magnetic shielding device is a cube structure with a side length of 3.6 m. Take the length of the pendulum L = 2 m and the pendulum angle α = 10°, then it can be known that the maximum displacement s max of the material to be measured in the horizontal direction is 0.6946 m. Taking the center of the magnetic sensor array as the origin, establish a space rectangular coordinate system, and the initial position of the material to be measured is [-0.7666 m, 0.07 m, 0 m] T . During the movement process, the material to be measured is always on the left side of the magnetic field sensor array, and there is no mechanical interference between the two.

[0087] Through calculation, the movement frequency f b of the pendulum is 0.35 Hz, and the data acquisition frequency fd Take 200 Hz, and the number of motion cycles of the simple pendulum is 50 times. Assume that after 50 simple pendulum cycles, the amplitude decays by 10%.

[0088] (2) Use the magnetic field vector measurement data of each magnetic sensor to calculate the magnetic gradient tensor G.

[0089] The structure of the magnetic sensor array is a square structure, and the resolution of the magnetic sensor is 15 fT. The magnetic noise in the magnetic shielding device is Gaussian white noise, and the noise standard deviation is 20 fT. After obtaining the magnetic field vector measurement data of each magnetic sensor, calculate G xx 、G xy 、G xz 、G yy and G yz These 5 independent components, and the calculation results of the independent components in the first cycle are as Figure 3 shown.

[0090] (3) By superimposing the images of the component G plus , obtain the time points corresponding to the nearest distance and the farthest distance in each simple pendulum cycle.

[0091] Use formula (6) to calculate the superimposed component G plus , and the calculation result of G plus in the first cycle is as Figure 4 shown. It can be seen from the results that the time point t min corresponding to the nearest distance in the first cycle is 1.42 s, and the time point t max corresponding to the farthest distance is 0 s. The t min and t max in other cycles are deduced by analogy.

[0092] (4) Obtain the magnetic field vector and magnetic gradient tensor generated by the material to be measured, and obtain the inversion result of the magnetic moment through the inversion algorithm.

[0093] By subtracting the magnetic field vector data at the nearest distance time point t min from the magnetic field vector data at the nearest distance time point t max , the magnetic field vector generated by the material to be measured can be obtained, as shown in Table 1.

[0094]

[0095] Table 1

[0096] Using the calculation formula of the magnetic gradient tensor, 5 independent components generated by the material to be measured can be obtained, as shown in Table 2.

[0097]

[0098] Table 2

[0099] The inversion algorithm adopts the Moore–Penrose generalized inverse Euler inversion method proposed by scholar T. Nara of the University of Tokyo in 2014. This inversion algorithm first performs singular value decomposition on the magnetic gradient tensor G:

[0100]

[0101] Calculate the matrix S according to formula (11) + :

[0102]

[0103] Then calculate the position vector r of the material to be measured according to formula (12):

[0104]

[0105] In the formula, B 1 , B 2 , B 3 , B 4 are the magnetic field vectors generated by the material to be measured. According to formula (9), the magnetic moment vector of the material to be measured can be obtained. The measurement results of the magnetic moment vectors of 50 single pendulum periods are as Figure 5 shown. The measurement results show that the standard deviations of the measurement results of the magnetic moment components m x , m y and m z are 0.206 nA·m 2 , 0.207 nA·m 2 and 0.228 nA·m 2 respectively, that is, the measurement precision is about 0.1%. Therefore, the method for repeated measurement of weak magnetic moments proposed by the present invention realizes high-precision measurement of weak magnetic moments.

[0106] By reasonably arranging the material to be measured, magnetic shielding device, single pendulum, non-magnetic support platform, magnetic sensor array, data acquisition and operation system, etc. of the weak magnetic moment repeated measurement system of the present invention, environmental magnetic interference can be effectively shielded to ensure the measurement accuracy and stability. The measurement method uses the single pendulum to drive the material to be measured to move back and forth, combined with the magnetic sensor array and the data acquisition and operation system, which not only improves the measurement accuracy, but also can accurately find the time point through the calculation of the magnetic gradient tensor and related components and the image analysis of the superimposed components, and obtain accurate magnetic moment results by using the inversion algorithm, realizing efficient measurement.

[0107] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A weak magnetic moment repeated measurement system, characterized in that: The weak magnetic moment repeated measurement system comprises a material to be measured, a magnetic shielding device, a simple pendulum, a non-magnetic support platform, a magnetic sensor array and a data acquisition and calculation system, wherein the simple pendulum, the material to be measured, the non-magnetic support platform and the magnetic sensor array are all arranged in the magnetic shielding device. The magnetic sensor array is arranged on the surface of the non-magnetic support platform, the material to be tested is suspended at the lower end of the pendulum and is always located on the side of the magnetic sensor array, and the signal output end of the magnetic sensor array is connected to the signal input end of the data acquisition operation system. Before the pendulum is released, the initial position of the material to be tested is on the same horizontal line as the magnetic sensor array.

2. A weak magnetic moment repeated measurement system according to claim 1, characterized in that: The material to be tested is used to make reciprocating motion with the simple pendulum and generate a magnetic field through its own magnetic properties, and serves as the object of measurement by the magnetic sensor array; The magnetic shielding device is used to shield environmental magnetic interference and reduce the influence of external magnetic fields on the measurement process; The simple pendulum is used to make the material to be tested reciprocate so that the magnetic sensor array can measure the magnetic field distribution of the material to be tested at different positions; A non-magnetic support table for placing the magnetic sensor array at a specified height; A magnetic sensor array is used to measure the magnetic field vector data of the material under test during its movement; The data acquisition and calculation system has a built-in data acquisition and inversion algorithm, which is used to convert the analog signal of the magnetic field vector data output by the magnetic sensor array into a digital signal, and calculate the magnetic moment vector to obtain the inversion result of the magnetic moment of the material to be tested.

3. A weak magnetic moment repeated measurement system according to claim 2, characterized in that: The magnetic shielding device is a cubic cavity, and the length L of the simple pendulum is 1 / 3 to 2 / 3 of the side length of the magnetic shielding device.

4. A weak magnetic moment repeated measurement system according to claim 3, characterized in that: The magnetic shielding device is a cubic cavity, and the number of motion cycles of the simple pendulum is 30 to 70.

5. A weak magnetic moment repeated measurement system according to claim 4, characterized in that: Frequency of magnetic field data acquisition f d ≥200f b .

6. A weak magnetic moment measurement repeated measurement method, applied to a weak magnetic moment repeated measurement system according to any one of claims 1 to 5, characterized in that: The repeated measurement method for weak magnetic moment measurement comprises the following steps: S1, using a simple pendulum to make the material to be tested reciprocate, and using a magnetic sensor array to measure the vector magnetic field; S2, calculating the magnetic gradient tensor G through the magnetic field vector measurement data of each magnetic sensor in the magnetic sensor array, and calculating the independent components of the magnetic gradient tensor G; S3. Calculate the superposition component G through the independent components of the magnetic gradient tensor G plus , and obtain G plus The change image G plus (t), get the time points corresponding to the shortest distance and the farthest distance in each simple pendulum cycle; S4. Obtain the magnetic field vector and magnetic gradient tensor generated by the material to be tested, and obtain the inversion result of the magnetic moment through an inversion algorithm.

7. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the repeated measurement method for weak magnetic moment measurement described in claim 6 is implemented.

8. A computer device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement a repeated measurement method for weak magnetic moment measurement as described in claim 6.

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