A magnetic anomaly detection method for metal classification detection using a magnetic anomaly detection device

Abstract

The present invention relates to the field of magnetic detection technology, and discloses a magnetic anomaly detection method for metal classification detection using a magnetic anomaly detection device. The magnetic anomaly detection device includes an excitation coil and eight induction coils arranged in a circumferential array along the excitation coil. The excitation coil and the eight induction coils are in the same plane and are uniformly fixed on an acrylic plate. The present invention adopts the design of an excitation coil and an array of induction coils, which can directly determine the position of a magnetic anomaly object through the difference in induced electromotive force, and extract the multi-angle magnetic polarization rate tensor matrix of the magnetic anomaly object; according to the relaxation model established by Langevin, determine the relationship between the magnetic polarization tensor and the material properties of the magnetic anomaly object material, and extract the initial change rate, time power term, and magnetization process of the material magnetic polarization rate as the basis for metal classification; realizes the precise positioning and real-time monitoring of the magnetic anomaly object, and can efficiently classify different types of metals, having broad application prospects and significant economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic detection, and particularly to a magnetic anomaly detection method for metal classification and detection using a magnetic anomaly detection device. Background Art

[0002] Metal detection and classification technologies have important applications in many fields such as industrial manufacturing, security, environmental protection, and medical treatment. In industry, metal detection is used to identify material components, ensure product quality, and is crucial in high-precision industries such as aviation and automotive manufacturing. In the security field, metal detectors are used to detect prohibited items, enhancing the safety of public places; in waste metal recycling, metal classification technologies improve the recycling efficiency of resources and reduce environmental pollution. In addition, it can be used to detect metal implants in the human body in medical equipment, and can be used to discover buried metal objects underground in archaeology and military detection.

[0003] Existing metal detection technologies mainly rely on single sensors or simple multi-sensor systems, and these systems have limitations in accurately positioning and classifying different types of metals. Generally, the existing technologies cannot achieve efficient classification and real-time monitoring of metal foreign objects, resulting in significant deficiencies in applications such as industrial detection, material classification, and security inspections. Therefore, there is an urgent need for a new method that can improve the accuracy and classification efficiency of metal detection. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a magnetic anomaly detection method for metal classification and detection using a magnetic anomaly detection device, which realizes accurate positioning and real-time monitoring of magnetic anomaly objects, and can efficiently classify different types of metals.

[0005] In order to achieve the above invention purpose, the following technical solutions are further adopted:

[0006] A magnetic anomaly detection device for metal classification and detection includes an excitation coil and eight induction coils arranged in a circumferential array along the excitation coil. The excitation coil and the eight induction coils are in the same plane and are uniformly fixed on an acrylic plate.

[0007] A magnetic anomaly detection method for metal classification and detection using a magnetic anomaly detection device includes the following steps:

[0008] S1. Place the magnetic anomaly detection device above the magnetic anomaly object, and provide an excitation current pulse to the excitation coil. The excitation coil generates an excitation magnetic field . The induced voltage generated by the excitation magnetic field at each induction coil is . When the excitation current pulse is turned off instantaneously, the excitation magnetic field rapidly decays, and the excitation magnetic anomaly object generates eddy currents This eddy current generates an induced magnetic field during the attenuation process. The induced voltage generated by the induced magnetic field at each induction coil is The induced voltages collected by each induction coil ;

[0009] S2. Metal target positioning: Divide the plane into approximately nine regions according to the positions of the excitation coil and the induction coils. The magnitude of the induced electromotive force of each induction coil is inversely proportional to the distance from the magnetic anomaly object. The horizontal orientation of the metal target can be determined based on the magnitude differences of the induced electromotive forces collected by the eight induction coils distributed in an array.

[0010] S3. According to the positioning methods in steps S1 and S2, move the magnetic anomaly detection device directly above the magnetic anomaly object so that the induced voltages collected by each induction coil are equal; different induction coils extract features at different angles of the magnetic anomaly object. According to the formula The induced electromotive force of the induction coil is:

[0011] ;

[0012] In the formula, is the magnetic polarizability tensor matrix at different angles of the magnetic anomaly object, represents the response function related to the distances between the magnetic anomaly object, the excitation coil, and the induction coils; , , are the main polarization elements of the magnetic polarizability tensor matrix. Calculate the average values , , respectively to eliminate the influence of the shape features;

[0013] Let represent the characteristic response matrix. The characteristic response matrix L(t) describes the dynamic response characteristics of the magnetic anomaly object in the time domain;

[0014] S4. Establish a relaxation model of the magnetic anomaly object under the action of the excitation magnetic field according to the Langevin function, calculate the steady-state magnetization intensity of the magnetic anomaly object, establish a variation model of the magnetization intensity with time, and calculate the variation of the magnetic polarizability with time;

[0015] S5. According to the relationship between the magnetic polarizability and the magnetization intensity , the characteristic response matrix is expressed as:

[0016] ;

[0017] represents the magnitude of the excitation magnetic field, represents the number of magnetic moments per unit volume, is the magnitude of a single magnetic moment, is the Boltzmann constant, is the temperature;

[0018] Extract the characteristics of the magnetic anomaly object:

[0019] ;

[0020] represents the initial change rate of the magnetic susceptibility, which is related to the steady-state magnetization of the material, the applied magnetic field, and the relaxation time is related, represents the influence of the time power term in the relaxation model, represents the relaxation rate, which is inversely proportional to the relaxation time inversely proportional;

[0021] By measuring the value, as the basis for classifying and identifying different metals.

[0022] The beneficial effects of the present invention are as follows: The present invention adopts the design of an excitation coil and an array induction coil, which can directly determine the position of the magnetic anomaly object through the difference in the induced electromotive force; through the layout design of the array induction coil, the multi-angle magnetic susceptibility tensor matrix of the magnetic anomaly object is extracted; according to Langevin, a relaxation model is established to determine the relationship between the magnetic polarization tensor and the material properties of the magnetic anomaly object material, and the initial change rate, time power term, and magnetization process of the material magnetic susceptibility are used as the basis for metal classification; precise positioning and real-time monitoring of the magnetic anomaly object are achieved, and different types of metals can be efficiently classified, with broad application prospects and significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0024] Figure 1 is a schematic diagram of the arrangement of the excitation coil and the induction coil of the present invention;

[0025] Figure 2 is a schematic diagram of magnetic anomaly detection of the present invention.

[0026] In the figure: 1. Excitation coil; 101. Excitation magnetic field; 2. Induction coil; 3. Magnetic anomaly object; 301. Eddy current of the magnetic anomaly object; 302. Induced magnetic field of the magnetic anomaly object. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] In order to enable those skilled in the art of this technology to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0029] As Figure 1 shown, a magnetic anomaly detection device for metal classification detection includes an excitation coil 1 and eight induction coils 2 arranged in a circumferential array along the excitation coil 1. The excitation coil 1 and the eight induction coils 2 are in the same plane and are uniformly fixed on an acrylic plate.

[0030] As Figure 2 shown, a magnetic anomaly detection method for metal classification detection using a magnetic anomaly detection device includes the following steps:

[0031] S1. Place the magnetic anomaly detection device above the magnetic anomaly object 3, and provide an excitation current pulse to the excitation coil 1, and the excitation coil 1 generates an excitation magnetic field 101 . The induced voltage generated by the excitation magnetic field 101 at each induction coil 2 is . When the excitation current pulse is turned off instantaneously, the excitation magnetic field 101 rapidly decays, and the excitation magnetic anomaly object 3 generates eddy currents . The eddy currents generate an induced magnetic field during the decay process . The induced voltage generated by the induced magnetic field at each induction coil 2 is . The induced voltages collected by each induction coil 2 are ;

[0032] S2. Metal target positioning. According to the positions of the excitation coil 1 and the induction coils 2, the plane is divided into approximately nine regions. The magnitude of the induced electromotive force of each induction coil 2 is inversely proportional to the distance from the magnetic anomaly object 3. According to the magnitude differences of the induced electromotive forces collected by the eight arrayed induction coils 2, the horizontal orientation of the metal target can be judged.

[0033] S3, according to the positioning method of step S1 and step S2, move the magnetic anomaly detection device to the top of the magnetic anomaly object 3, so that the induced voltage collected by each induction coil 2 is equal; different induction coils 2 extract features of the magnetic anomaly object 3 at different angles, according to the formula , the induced electromotive force of induction coil 2 is:

[0034] ;

[0035] Where, is the magnetic polarizability tensor matrix of the magnetic anomaly object 3 at different angles, The response function represents the distance between the magnetic object 3 and the excitation coil 1 and the induction coil 2; 、 、 is the main polarization element of the magnetic polarizability tensor matrix, and the average value is calculated respectively. 、 、 , eliminate the influence of shape features;

[0036] make It represents the characteristic response matrix, which describes the dynamic response characteristics of the magnetic anomaly object 3 in the time domain;

[0037] S4. Establish a relaxation model of the magnetic object 3 under the action of the excitation magnetic field 101 according to the Langevin function, and calculate the steady-state magnetization intensity of the magnetic object 3. , establish the magnetization Time-varying model to calculate magnetic polarizability changes over time;

[0038] S5, according to the magnetic polarizability and magnetization relationship , the characteristic response matrix Expressed as:

[0039] ;

[0040] Indicates the magnitude of the excitation magnetic field 101, Represents the number of magnetic moments per unit volume, is the magnitude of a single magnetic moment, is the Boltzmann constant, It is the temperature;

[0041] Extract 3 features of magnetic anomaly:

[0042] ;

[0043] represents the initial change rate of magnetic susceptibility and is related to the steady-state magnetization of the material , the applied magnetic field and the relaxation time . represents the influence of the time power term in the relaxation model represents the relaxation rate, which is inversely proportional to the relaxation time ;

[0044] By measuring the value of , it serves as a basis for classifying and identifying different metals.

[0045] Collect feature vectors by extracting different metal samples ; perform one-hot encoding on the metal categories ; construct a data set from the feature vectors of the metal samples and the corresponding category vectors ;

[0046] Furthermore, perform normalization processing on the feature vectors so that the values of each feature are within the same range;

[0047] Use a machine learning model, such as a support vector machine, to train the existing training data and construct a metal classification model;

[0048] Repeat steps S1 - S5 for unknown metals to locate and extract their feature vectors X ; perform normalization processing on the extracted feature vectors; input them into the metal classification model described in step four to calculate the output Y ; determine the metal type of the magnetic anomaly object according to the output one-hot encoding.

[0049] In the present invention, the excitation coil 1 is located at the center, and the induction coils 2 are evenly distributed around it, realizing the positioning of the magnetic anomaly object 3 and multi-angle feature extraction; by analyzing the magnetic field generated by the excitation current pulse and the multi-angle magnetic susceptibility tensor matrix, the influence of the object geometry on classification is eliminated; through the magnetization relaxation model established by the Langevin function, the dynamic response characteristics of metal materials in the magnetic field are described, and the initial change rate of the magnetic susceptibility of the material, the time power term, and the magnetization process are used as the basis for metal classification. The device can real-time locate the magnetic anomaly object 3 and distinguish different types of metals based on the magnetic susceptibility tensor matrix, and is applicable to industrial detection, material classification, security inspection and other fields, with broad application prospects and significant economic benefits.

[0050] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, component splitting or combination, etc., made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A magnetic anomaly detection method for metal classification and detection using a magnetic anomaly detection device. The magnetic anomaly detection device includes an excitation coil and eight induction coils arranged in a circumferential array along the excitation coil. The excitation coil and the eight induction coils are in the same plane and are uniformly fixed on an acrylic plate. It is characterized in that, Including the following steps: S1. Place the magnetic anomaly detection device above the magnetic anomaly object and apply an excitation current pulse to the excitation coil, and the excitation coil generates an excitation magnetic field . The induced voltage generated by the excitation magnetic field at each induction coil is . At the instant when the excitation current pulse is turned off, the excitation magnetic field rapidly decays, and the excitation magnetic anomaly object generates eddy currents . During the decay process of the eddy currents, an induced magnetic field is generated . The induced voltage generated by the induced magnetic field at each induction coil is . The induced voltages collected by each induction coil ; S2. Metal target positioning. The plane is divided into approximately nine regions according to the positions of the excitation coil and the induction coils. The magnitude of the induced electromotive force of each induction coil is inversely proportional to the distance from the magnetic anomaly object. The horizontal orientation of the metal target can be determined based on the magnitude differences of the induced electromotive forces collected by the eight induction coils distributed in an array. S3. Move the magnetic anomaly detection device directly above the magnetic anomaly object according to the positioning method in steps S1 and S2, so that the induced voltages collected by each induction coil are equal; different induction coils extract features from different angles of the magnetic anomaly object. According to the formula , the induced electromotive force of the induction coil is: ； In the formula, is the magnetic polarization rate tensor matrix of the magnetic anomaly object at different angles, represents the response function related to the distances between the magnetic anomaly object, the excitation coil, and the induction coil; , , are the main polarization elements of the magnetic polarization rate tensor matrix, and the average values , , are calculated respectively to eliminate the influence of the shape characteristics; Let represent the feature response matrix, and the feature response matrix L(t) describes the dynamic response characteristics of the magnetic anomaly object in the time domain; S4. Establish a relaxation model of the magnetic anomaly object under the action of the excitation magnetic field according to the Langevin function, and calculate the steady-state magnetization of the magnetic anomaly object. , establish the magnetization change model with time, and calculate the magnetic susceptibility change with time; S5. According to the relationship between magnetic susceptibility and magnetization intensity , the characteristic response matrix is expressed as: ； represents the magnitude of the excitation magnetic field, represents the number of magnetic moments per unit volume, is the magnitude of a single magnetic moment, is the Boltzmann constant, is the temperature; Extract the characteristics of the magnetic anomaly object: ； represents the initial change rate of magnetic susceptibility and is related to the steady-state magnetization of the material , the applied magnetic field, and the relaxation time, represents the influence of the time power term in the relaxation model, represents the relaxation rate, and is inversely proportional to the relaxation time ; By measuring values, as a basis for classifying and identifying different metals.

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