Magnetic anomaly detection device and method for metal classification detection

Abstract

The invention relates to the technical field of magnetic detection, and discloses a magnetic anomaly detection device and method for metal classification detection, the magnetic anomaly detection device for metal classification detection comprises an excitation coil and eight induction coils distributed in the circumferential direction of the excitation coil in an array mode, and the excitation coil and the eight induction coils are located on the same plane. And the fixing plates are uniformly fixed on the acrylic plate. The design of the excitation coil and the array induction coil is adopted, the position of the magnetic heterogeneity object can be determined directly through the difference of induced electromotive force, and a multi-angle magnetic polarization rate tensor matrix of the magnetic heterogeneity object is extracted; establishing a relaxation model according to the Langhuan, determining the relationship between the magnetic polarization tensor and the material property of the material magnetic heterogeneity object, and extracting the initial change rate, the time power term and the magnetization process of the material magnetic polarization rate as metal classification basis; the method realizes accurate positioning and real-time monitoring of the magnetic foreign object, can efficiently classify different types of metals, and has wide application prospects and remarkable economic benefits.

Description

Technical Field

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

[0002] Metal detection and sorting technology has important applications in many fields such as industrial manufacturing, security, environmental protection and medical treatment. In industry, metal detection is used to identify material composition, ensure product quality, and is crucial in high-precision industries such as aviation and automobile manufacturing. In the security field, metal detectors are used to detect prohibited items and improve the safety of public places; in scrap metal recycling, metal sorting technology improves the efficiency of resource recycling and reduces environmental pollution. In addition, it can be used in medical equipment to detect metal implants in the human body, and in archaeological detection, it can be used to discover buried metal objects.

[0003] Existing metal detection technologies mainly rely on single sensors or simple multi-sensor systems, which have limitations in accurately locating and classifying different types of metals. Typically, existing technologies cannot achieve efficient classification and real-time monitoring of metallic foreign bodies, resulting in significant deficiencies in applications such as industrial inspection, material sorting, and security inspection. Therefore, a new method that can improve metal detection accuracy and classification efficiency is urgently needed. Summary of the invention

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

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted is as follows:

[0006] A magnetic anomaly detection device for metal classification detection comprises an excitation coil and eight induction coils distributed in an array along the circumference of the excitation coil. The excitation coil and the eight induction coils are in the same plane and are evenly fixed on an acrylic plate.

[0007] The magnetic anomaly detection method using the magnetic anomaly detection device for metal classification detection as described above comprises the following steps:

[0008] S1. Place the magnetic anomaly detection device above the magnetic anomaly object, and provide the excitation current pulse i(t) to the excitation coil, which excites the excitation coil to generate an excitation magnetic field B. 1 (t), the induced voltage generated by the excitation magnetic field at each induction coil is v 1 (t), the moment when the excitation current pulse i(t) is turned off, the excitation magnetic field B 1 (t) Rapid decay, exciting magnetic anomalies to generate eddy current i 2(t), the eddy current generates an induced magnetic field B during the decay process 2 (t), the induced voltage generated by the induced magnetic field at each induction coil is v 2i (t), the induced voltage v collected by each induction coil oi (t) = v 1i (t)+v 2i (t);

[0009] S2. Metal target positioning: the plane is divided into nine regions of approximately 3×3 according to the positions of the excitation coil and the induction coil. The magnitude of the induced electromotive force of each induction coil is inversely proportional to the distance of the magnetic object. The horizontal position of the metal target can be determined based on the magnitude difference of the induced electromotive force collected by the eight array-distributed induction coils.

[0010] S3, according to the positioning method of step S1 and step S2, the magnetic anomaly detection device is moved to the top of the magnetic anomaly object, so that the induced voltage collected by each induction coil is equal; different induction coils extract features of the magnetic anomaly object at different angles, according to formula B 2 (r 2i )=G(r 2i )·χ·B 1 (r 0 ), the induced electromotive force of the induction coil is:

[0011]

[0012] In the formula, χ i is the magnetic polarizability tensor matrix of the magnetic anomaly object at different angles, q(t) represents the response function related to the distance between the magnetic anomaly object and the excitation coil and the induction coil; xx , χ yy , χ zz is the main polarization element of the magnetic polarizability tensor matrix, and the average values ​​are calculated respectively. Eliminate the influence of shape features;

[0013] make It represents the characteristic response matrix, which describes the dynamic response characteristics of the magnetic anomaly object in the time domain;

[0014] S4. Based on the Langevin function, a relaxation model of a magnetic anomaly object under the action of an excitation magnetic field is established to calculate the steady-state magnetization intensity M of the magnetic anomaly object. 0 , establish a model of the change of magnetization intensity M(t) with time, and calculate the change of magnetic polarizability χ(t) with time;

[0015] S5. According to the relationship between magnetic polarizability χ(t) and magnetization intensity M(t), M(t)=χ(t)H, the characteristic response matrix L(t) is expressed as:

[0016]

[0017] H represents the magnitude of the excitation magnetic field, n represents the number of magnetic moments per unit volume, μ is the magnitude of a single magnetic moment, and k B is the Boltzmann constant, T is the temperature;

[0018] Extract the characteristics of magnetic anomalies:

[0019]

[0020] k represents the initial rate of change of magnetic polarizability, which is related to the steady-state magnetization intensity M of the material. 0 , the external magnetic field H is related to the relaxation time τ, β represents the influence of the time power term in the relaxation model, and γ represents the relaxation rate, which is inversely proportional to the relaxation time τ;

[0021] By measuring the values ​​of k, β, and γ, different metals can be classified and identified.

[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, and can directly determine the position of a magnetic anomaly object through the difference in induced electromotive force; extracts a multi-angle magnetic polarizability tensor matrix of the magnetic anomaly object through the layout design of the array induction coil; establishes a relaxation model based on Langevin to determine the relationship between the magnetic polarization tensor and the material properties of the magnetic anomaly object, extracts the initial change rate of the material magnetic polarizability, the time power term, and the magnetization process as the basis for metal classification; realizes accurate positioning and real-time monitoring of the magnetic anomaly object, and can efficiently classify different types of metals, and has broad application prospects and significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary 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 It is a schematic diagram of the arrangement of the excitation coil and the induction coil of the present invention;

[0025] Figure 2 It 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; 301. eddy current of magnetic anomaly; 302. induced magnetic field of magnetic anomaly. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application 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 to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0029] like Figure 1 As shown, a magnetic anomaly detection device for metal classification detection includes an excitation coil 1 and eight induction coils 2 distributed 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 evenly fixed on an acrylic plate.

[0030] like Figure 2 As shown, the magnetic anomaly detection method using the magnetic anomaly detection device for metal classification detection as described above comprises the following steps:

[0031] S1. Place the magnetic anomaly detection device above the magnetic anomaly object 3, and provide the excitation current pulse i(t) to the excitation coil 1, which excites the excitation coil 1 to generate an excitation magnetic field 101B. 1 (t), the induced voltage generated by the excitation magnetic field 101 at each induction coil 2 is v 1 (t), the moment when the excitation current pulse i(t) is turned off, the excitation magnetic field 101B 1 (t) Rapid decay, exciting the magnetic object 3 to generate eddy current i 2 (t), the eddy current generates an induced magnetic field B during the decay process 2 (t), the induced voltage generated by the induced magnetic field at each induction coil 2 is v 2i (t), the induced voltage v collected by each induction coil 2 oi (t) = v 1i (t)+v 2i (t);

[0032] S2. Metal target positioning: the plane is divided into nine regions of approximately 3×3 according to the positions of the excitation coil 1 and the induction coil 2. The magnitude of the induced electromotive force of each induction coil 2 is inversely proportional to the distance of the magnetic object 3. The horizontal position of the metal target can be determined based on the magnitude difference of the induced electromotive force collected by the eight array-distributed induction coils 2.

[0033] S3, according to the positioning method of step S1 and step S2, the magnetic anomaly detection device is moved 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 formula B 2 (r 2i)=G(r 2i )·χ·B 1 (r 0 ), the induced electromotive force of induction coil 2 is:

[0034]

[0035] In the formula, χ i is the magnetic polarizability tensor matrix of the magnetic anomaly object 3 at different angles, q(t) represents the response function related to the distance between the magnetic anomaly object 3 and the excitation coil 1 and the induction coil 2; xx , χ yy , χ zz is the main polarization element of the magnetic polarizability tensor matrix, and the average values ​​are calculated respectively. Eliminate the influence of shape features;

[0036] make represents the characteristic response matrix, and the characteristic response matrix L(t) describes the dynamic response characteristics of the magnetic anomaly object 3 in the time domain;

[0037] S4. Based on the Langevin function, a relaxation model of the magnetic anomaly object 3 under the action of the excitation magnetic field 101 is established to calculate the steady-state magnetization intensity M of the magnetic anomaly object 3. 0 , establish a model of the change of magnetization intensity M(t) with time, and calculate the change of magnetic polarizability χ(t) with time;

[0038] S5. According to the relationship between magnetic polarizability χ(t) and magnetization intensity M(t), M(t)=χ(t)H, the characteristic response matrix L(t) is expressed as:

[0039]

[0040] H represents the magnitude of the excitation magnetic field 101, n represents the number of magnetic moments per unit volume, μ is the magnitude of a single magnetic moment, k B is the Boltzmann constant, T is the temperature;

[0041] Extract 3 features of magnetic anomalies:

[0042]

[0043] k represents the initial rate of change of magnetic polarizability, which is related to the steady-state magnetization intensity M of the material. 0 , the external magnetic field H is related to the relaxation time τ, β represents the influence of the time power term in the relaxation model, and γ represents the relaxation rate, which is inversely proportional to the relaxation time τ;

[0044] By measuring the values ​​of k, β, and γ, different metals can be classified and identified.

[0045] Collect different metal samples to extract feature vector X i= [k, β, γ]; uniquely encode the metal category Y i ; The feature vectors and corresponding category vectors of metal samples are constructed as a data set {(X i ,Y i )};

[0046] Furthermore, the feature vectors are normalized so that the value of each feature is in the same range;

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

[0048] Repeat steps S1 to S5 for the unknown metal to locate and extract its feature vector X; standardize the extracted feature vector; input it into the metal classification model described in step 4 to calculate the output Y; determine the metal type of the magnetic anomaly object based on the output unique hot encoding.

[0049] The excitation coil 1 of the present invention is located in the center, and the induction coil 2 is evenly distributed around it, so as to realize the positioning and multi-angle feature extraction of the magnetic anomaly 3; the magnetic field generated by the excitation current pulse is analyzed with the multi-angle magnetic polarizability tensor matrix, eliminating the influence of the geometric shape of the object on the classification; the magnetization relaxation model established by the Langevin function is used to describe the dynamic response characteristics of the metal material in the magnetic field, and the initial change rate of the material magnetic polarizability, the time power term, and the magnetization process are extracted as the basis for metal classification. The device can locate the magnetic anomaly 3 in real time and distinguish different types of metals based on the magnetic polarizability tensor matrix, and is suitable for industrial detection, material classification, safety inspection and other fields, with broad application prospects and significant economic benefits.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, component splitting or combination, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnetic anomaly detection device for metal classification detection, characterized in that: It comprises an excitation coil and eight induction coils which are distributed in an array along the circumference of the excitation coil. The excitation coil and the eight induction coils are in the same plane and are evenly fixed on an acrylic plate.

2. A magnetic anomaly detection method using the magnetic anomaly detection device for metal classification detection as claimed in claim 1, characterized in that: The following steps are involved: S1. Place the magnetic anomaly detection device above the magnetic anomaly object. Provide the excitation current pulse i(t) to the excitation coil, which excites the excitation coil to generate an excitation magnetic field B1(t). The induced voltage generated by the excitation magnetic field at each induction coil is v1(t). At the moment when the excitation current pulse i(t) is turned off, the excitation magnetic field B1(t) decays rapidly, and the magnetic anomaly object is excited to generate an eddy current i2(t). The eddy current generates an induced magnetic field B2(t) during the decay process. The induced voltage generated by the induced magnetic field at each induction coil is v 2i (t), the induced voltage v collected by each induction coil oi (t) = v 1i (t)+v 2i (t); S2. Metal target positioning: the plane is divided into nine regions of approximately 3×3 according to the positions of the excitation coil and the induction coil. The magnitude of the induced electromotive force of each induction coil is inversely proportional to the distance of the magnetic object. The horizontal position of the metal target can be determined based on the magnitude difference of the induced electromotive force collected by the eight array-distributed induction coils. S3, according to the positioning method of step S1 and step S2, the magnetic anomaly detection device is moved to the top of the magnetic anomaly object, so that the induced voltage collected by each induction coil is equal; different induction coils extract features of the magnetic anomaly object at different angles, and according to formula B2(r 2i )=G(r 2i )·χ·B1(r0), the induced electromotive force of the induction coil is: In the formula, χ i is the magnetic polarizability tensor matrix of the magnetic anomaly object at different angles, q(t) represents the response function related to the distance between the magnetic anomaly object and the excitation coil and the induction coil; xx , χ yy , χ zz is the main polarization element of the magnetic polarizability tensor matrix, and the average values ​​are calculated respectively. Eliminate the influence of shape features; make It represents the characteristic response matrix, which describes the dynamic response characteristics of the magnetic anomaly object in the time domain; S4. A relaxation model of a magnetic anomaly object under an excitation magnetic field is established according to the Langevin function, the steady-state magnetization intensity M0 of the magnetic anomaly object is calculated, a model of the change of the magnetization intensity M(t) over time is established, and the change of the magnetic polarizability χ(t) over time is calculated; S5. According to the relationship between magnetic polarizability χ(t) and magnetization intensity M(t), M(t)=χ(t)H, the characteristic response matrix L(t) is expressed as: H represents the magnitude of the excitation magnetic field, n represents the number of magnetic moments per unit volume, μ is the magnitude of a single magnetic moment, and k B is the Boltzmann constant, T is the temperature; Extract the characteristics of magnetic anomalies: k represents the initial change rate of magnetic polarizability, which is related to the steady-state magnetization intensity M0 of the material, the external magnetic field H and the relaxation time τ, β represents the influence of the time power term in the relaxation model, and γ represents the relaxation rate, which is inversely proportional to the relaxation time τ; By measuring the values ​​of k, β, and γ, different metals can be classified and identified.

Images