Signal fast calculation method and system for pulsed eddy current metal flat plate detection

Abstract

The present invention discloses a rapid signal calculation method and system for pulsed eddy current metal plate inspection. This method analyzes magnetic sensor signals in real time during pulsed eddy current metal plate inspection. By rapidly solving the inverse Laplace transform using the residue theorem, the frequency-domain received signal is converted into a time-domain received signal in real time, enabling rapid and accurate calculation of the magnetic sensor signal. When the sensor size, i.e., the electromagnetic properties of the metal plate, changes, the received signal calculated by the proposed method is consistent with the results obtained using the finite element method. The average calculation time for a single received signal is only 0.68 seconds, far less than traditional calculation methods such as the inverse Fourier transform, effectively improving the speed of magnetic sensor signal analysis.

Description

Technical Field

[0001] The present invention relates to the technical field of signal calculation for pulsed eddy current, and in particular to a fast signal calculation method and system for pulsed eddy current metal flat plate detection. Background Art

[0002] Pulsed eddy current testing (PEC) is a non-contact, non-destructive testing technology used to detect surface and near-surface defects in metal and conductive materials, such as cracks, inclusions, and corrosion. It uses an alternating current (AC) electromagnetic field to generate eddy currents on the surface of the object being tested. This in turn induces a reverse electromagnetic field, which is then measured to detect defects in the material.

[0003] Pulsed eddy current testing offers high sensitivity and high resolution, enabling the detection of very small surface defects, such as tiny cracks and holes. Furthermore, its non-contact and rapid detection capabilities allow it to provide test data in a short period of time without damaging the object being tested. This makes it particularly suitable for efficient, large-scale production line testing.

[0004] In order to predict and analyze the results of eddy current measurements, the eddy current distribution can be analyzed through analytical solutions. Currently, traditional single-frequency eddy current analytical calculation methods require frequency domain calculations and feature separation to calculate and predict the eddy current distribution. For pulsed eddy current testing, the characteristics of the measurement signal are reflected in the time domain, and the calculation needs to be realized using a time-frequency conversion algorithm. This algorithm is often time-consuming, has low computational efficiency, and is difficult to solve in real time. Therefore, a fast analytical calculation method suitable for pulsed eddy current testing is needed to predict and analyze the measurement results of pulsed eddy current. Summary of the Invention

[0005] In order to solve the technical problems existing in the background technology, the present invention proposes a method and system for rapid signal calculation for pulsed eddy current metal flat plate detection.

[0006] The present invention proposes a method for rapid signal calculation for pulsed eddy current metal flat plate detection, comprising the following steps:

[0007] S1. Calculate the frequency domain received signal of the magnetic sensor using the TREE analytical model , the frequency domain received signal Convert to complex function model ;

[0008] S2. Approximately calculate the above complex function model using the Taylor expansion formula The poles of the phase function;

[0009] S3. Solve the inverse Laplace transform of the phase function poles by the residue theorem to obtain the time domain received signal. .

[0010] Preferably, in S1, the frequency domain received signal for:

[0011] in, , is the Bessel function of the first kind, , is the spatial frequency of the column harmonics, is the current function applied to the excitation coil, is the frequency domain received signal of the current, is a step function, is the current signal amplitude, is the time constant determined by the coil parameters, and are the distances between the upper and lower edges of the magnetic sensor and the surface of the measured plate, is the radius of the magnetic sensor, is the vacuum permeability, , and are the thickness, electrical conductivity and relative magnetic permeability of the measured plate respectively.

[0012] Preferably, in S1, the complex function model for: ;

[0013] in, is the phase function.

[0014] Preferably, in S2, the above complex function model is approximately calculated by Taylor expansion formula Phase function The extremes include:

[0015] S21. Calculate the phase function using the following equation:

[0016] Where, , is the spatial frequency of the column harmonics;

[0017] S22. Approximate solution of the phase function poles of the pulsed eddy current frequency domain model:

[0018] Among them, the poles of the phase function include , and , according to the variable substitution relationship , and Calculated by the following equations:

[0019] Where, , , the number of poles is .

[0020] Preferably, m=25.

[0021] Preferably, the time domain received signal of the inverse Laplace transform is solved by the residue theorem for:

[0022] Where, , is the Bessel function of the first kind, , .

[0023] The proposed rapid signal calculation method for pulsed eddy current metal plate inspection uses pulsed eddy current technology to analyze magnetic sensor signals in real time. By using the residue theorem to rapidly solve the inverse Laplace transform, the frequency-domain received signal is converted into the time-domain received signal in real time, enabling rapid and accurate calculation of the magnetic sensor signal. When the sensor size, i.e., the electromagnetic properties of the metal plate, changes, the received signal calculated by the proposed method is consistent with the results obtained using the finite element method. The average calculation time for a single received signal is only 0.68 seconds, far less than traditional calculation methods such as the inverse Fourier transform, effectively improving the speed of magnetic sensor signal analysis.

[0024] The present invention also proposes a rapid signal calculation system for pulsed eddy current metal flat plate detection, comprising:

[0025] A TMR sensing device is used to obtain a TMR detection signal of the excited eddy current field of the test sample;

[0026] processor;

[0027] Memory; and

[0028] One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the processor, the programs including a method for executing the above-mentioned fast signal calculation method for pulsed eddy current metal flat plate detection.

[0029] Preferably, the TMR sensing device includes two excitation coils and a TMR magnetic sensor, the excitation coils are used to excite eddy current fields in the test sample, and the TMR magnetic sensor is used to measure eddy current field signals in the test sample, and the two excitation coils are arranged at opposite sides of the TMR magnetic sensor.

[0030] In the present invention, the proposed rapid signal calculation system for pulsed eddy current metal flat plate detection has a technical effect similar to the rapid signal calculation method for pulsed eddy current metal flat plate detection, and therefore will not be described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of an embodiment of a method for rapid signal calculation for pulsed eddy current metal flat plate detection proposed by the present invention.

[0032] Figure 2 This is a detection schematic diagram of an implementation of a signal rapid calculation method for pulsed eddy current metal flat plate detection proposed by the present invention.

[0033] Figure 3 This is a schematic diagram of calculation results when sensor parameters and metal plate parameters change in an embodiment of a signal rapid calculation method for pulsed eddy current metal plate detection proposed by the present invention. DETAILED DESCRIPTION

[0034] like Figures 1 to 3 As shown, Figure 1 This is a schematic diagram of an embodiment of a method for rapid signal calculation for pulsed eddy current metal flat plate detection proposed by the present invention. Figure 2 This is a detection schematic diagram of an embodiment of a method for rapid signal calculation for pulsed eddy current metal flat plate detection proposed by the present invention. Figure 3 This is a schematic diagram of calculation results when sensor parameters and metal plate parameters change in an embodiment of a signal rapid calculation method for pulsed eddy current metal plate detection proposed by the present invention.

[0035] Reference Figure 1 The present invention proposes a method for rapid signal calculation for pulsed eddy current metal flat plate detection, comprising the following steps:

[0036] S1. Calculate the frequency domain received signal of the magnetic sensor using the TREE analytical model , the frequency domain received signal Convert to complex function model ;

[0037] Specifically, the frequency domain received signal for:

[0038] in, , is the Bessel function of the first kind, , is the spatial frequency of the column harmonics, is the current function applied to the excitation coil, is the frequency domain received signal of the current, is a step function, is the current signal amplitude, is the time constant determined by the coil parameters, and are the distances between the upper and lower edges of the magnetic sensor and the surface of the measured plate, is the radius of the magnetic sensor, is the vacuum permeability, , and are the thickness, electrical conductivity and relative magnetic permeability of the measured plate respectively.

[0039] The transformed complex function model for: ;

[0040] in, is the phase function.

[0041] S2. Approximately calculate the above complex function model using the Taylor expansion formula The poles of the phase function;

[0042] Specifically include:

[0043] S21. Calculate the phase function using the following equation:

[0044] Where, , is the spatial frequency of the column harmonics;

[0045] S22. Approximate solution of the phase function poles of the pulsed eddy current frequency domain model:

[0046] Among them, the poles of the phase function include , and , according to the variable substitution relationship , and Calculated by the following equations:

[0047] Where, , , the number of poles is During calculation, the number of poles can be set to 50, and the poles of the phase function can be solved by equations (26) and (27).

[0048] S3. Solve the inverse Laplace transform of the phase function poles by the residue theorem to obtain the time domain received signal. .

[0049] Specifically, the time domain received signal for:

[0050] Where, , is the Bessel function of the first kind, , .

[0051] This embodiment also provides a rapid signal calculation system for pulsed eddy current metal flat plate detection, including:

[0052] A TMR sensing device is used to obtain a TMR detection signal of the excited eddy current field of the test sample;

[0053] processor;

[0054] Memory; and

[0055] One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the processor, the programs including a method for executing the above-mentioned fast signal calculation method for pulsed eddy current metal flat plate detection.

[0056] Reference Figure 2 In the specific setting of the TMR sensing device, the TMR sensing device includes two excitation coils 1 and a TMR magnetic sensor 2. The excitation coil 1 is used to excite the eddy current field in the test sample 3, and the TMR magnetic sensor 2 is used to measure the eddy current field signal in the test sample. The two excitation coils 1 are arranged on both sides of the TMR magnetic sensor 2 with relative spacing.

[0057] During the specific detection process of the TMR sensing device of this embodiment, the TMR magnetic sensor is located at the center of the two excitation coils and measures the magnetic field signal perpendicular to the surface of the sample being tested. The magnetic field generated by the excitation coil generates eddy currents on the surface of the flat metal sample. After the magnetic field is maintained for a period of time and a steady state is formed, the current in the excitation coil is removed, causing the excitation magnetic field to quickly disappear. Due to Lenz's law, the secondary magnetic field generated by the eddy current will offset some of the effects of the sudden change in the magnetic field, making the change in the magnetic field relatively slow. The TMR magnetic sensor can collect the magnetic field in the corresponding area and convert it into a voltage signal, realizing the signal response detection of the metal sample to the pulsed eddy current.

[0058] In this embodiment, a rapid signal calculation method and system for pulsed eddy current metal plate testing is proposed. This method analyzes magnetic sensor signals used in pulsed eddy current metal plate testing in real time. By rapidly solving the inverse Laplace transform using the residue theorem, the received frequency domain signal is converted to a time domain signal in real time, enabling rapid and accurate calculation of the magnetic sensor signal. When the sensor size, i.e., the electromagnetic properties of the metal plate, changes, the received signal calculated by the proposed method is consistent with the results obtained using the finite element method. The average calculation time for a single received signal is only 0.68 seconds, significantly less than traditional calculation methods such as the inverse Fourier transform, effectively improving the speed of magnetic sensor signal analysis.

[0059] The following describes in detail the method and system for rapid signal calculation for pulsed eddy current metal flat plate detection according to this embodiment through specific examples.

[0060] This embodiment adopts a rapid analytical calculation method based on pulsed eddy current testing, which specifically includes the following steps:

[0061] Step 1) Calculate the frequency domain detection signal measured by the coil-excited magnetic sensor using the Truncated Eigenfunction Expansion (TREE) analytical model , and receive the signal in the frequency domain Convert to complex function model The frequency domain received signal when the magnetic sensor detects a single metal plate is:

[0062] Where, , is the Bessel function of the first kind, , is the spatial frequency of the column harmonics, is the current function applied to the excitation coil, is the frequency domain received signal of the current, is a step function, is the current signal amplitude, is the time constant determined by the coil parameters, and are the distances between the upper and lower edges of the magnetic sensor and the surface of the measured plate, is the radius of the magnetic sensor, is the vacuum permeability, , and are the thickness, electrical conductivity and relative magnetic permeability of the measured plate respectively.

[0063] In the complex plane, let , receiving signal It can be expressed as ,Right now

[0064] Step 2) Approximate calculation using Taylor expansion formula The poles of the signal phase function. Phase function The extreme and According to the formula and Root calculation,

[0065] By variable substitution ,Mode and Equivalent to the formula and Solve for the roots of

[0066] In the formula, the real variable , .

[0067] According to the relationship between tangent and cotangent functions, and Equivalent to the formula Solving the roots of

[0068] Where, is the number of extreme points.

[0069] The function is approximated by the first two terms of the Taylor expansion formula of the tangent function, that is, By solving the formula Approximate solution Root.

[0070] Where, is the Bernoulli number, .

[0071] Mode In this case, the real roots of the cubic equation are

[0072] Where, , .

[0073] According to the above relationship, the equation and The roots of and Approximate calculation,

[0074] Where, , , .

[0075] Step 3) Solve the inverse Laplace transform using the residue theorem to obtain the time domain received signal The time domain received signal is calculated by inverse Laplace transform as follows,

[0076] Among them, the inverse Laplace transform is calculated by the residue theorem,

[0077] Where, , and is the phase function The extreme point of the equation and Root.

[0078] General Zhishi Substitution After simplification, the time domain expression of the signal received by the magnetic sensor is obtained:

[0079] In the formula, the coefficient and They are and , can be calculated by the following formula

[0080] Where, .

[0081] The present invention provides real-time analysis of magnetic sensor signals from metal plate inspection using pulsed eddy current technology. By rapidly solving the inverse Laplace transform using the residue theorem, the frequency-domain received signal is converted to the time-domain received signal in real time, enabling rapid and accurate calculation of the magnetic sensor signal. Specifically, when the sensor size, i.e., the electromagnetic properties of the metal plate, changes, the received signal calculated by the proposed method is consistent with the results obtained using the finite element method. The average calculation time for a single received signal is only 0.68 seconds, significantly less than traditional calculation methods such as the inverse Fourier transform, effectively improving the speed of magnetic sensor signal analysis.

[0082] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A fast signal calculation method for pulsed eddy current metal flat plate detection, characterized in that: Detection is performed using a TMR sensing device, the TMR sensing device comprising two excitation coils (1) and a TMR magnetic sensor (2), the excitation coils (1) being used to excite an eddy current field in a test sample (3), the TMR magnetic sensor (2) being used to measure eddy current field signals in the test sample, and the two excitation coils (1) being arranged at opposite sides of the TMR magnetic sensor (2) with a relative spacing; The method comprises the following steps: S1. Calculate the frequency domain received signal B of the magnetic sensor using the TREE analytical model z (ω), the frequency domain received signal B z (ω) is transformed into complex function model B z (s); S2. Approximately calculate the above complex function model B using the Taylor expansion formula z (s) the phase function extremes; S3. Solve the inverse Laplace transform of the phase function poles by the residue theorem to obtain the time domain received signal B. z (t); Wherein, the complex function model B z (s) is: Among them, φ(α i ,s) is the phase function; α i is the spatial frequency of the column harmonics, c1 and c2 are the distances between the upper and lower edges of the magnetic sensor and the surface of the measured plate, i0(s) is the expression of the current in the frequency domain, and s is the frequency domain function obtained by Laplace transform.

2. The method for rapid signal calculation for pulsed eddy current metal flat plate detection according to claim 1, characterized in that: In S1, the frequency domain received signal B z (ω) is: i0(t)=I0(1-e -t / τ )u(t) (4) in, J1(·) is the Bessel function of the first kind, α i is the spatial frequency of the column harmonics, i0(t) is the current function applied to the excitation coil, i0(ω)=F[i0(t)] is the frequency domain received signal of the current, u(t) is the step function, I0 is the current signal amplitude, τ is the time constant determined by the coil parameters, c1 and c2 are the distances between the upper and lower edges of the magnetic sensor and the surface of the measured plate, r0 is the radius of the magnetic sensor, μ0 is the vacuum permeability, d, σ and μ r are the thickness, electrical conductivity and relative magnetic permeability of the measured plate respectively.

3. A fast signal calculation system for pulsed eddy current metal flat plate detection, characterized in that: include: A TMR sensing device is used to obtain a TMR detection signal of the excited eddy current field of the test sample; processor; Memory; as well as One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the processor, the programs including a method for executing a fast signal calculation method for pulsed eddy current metal flat plate detection according to any one of claims 1-2.

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