A split coil array signal detection method and detection device

Abstract

The present invention discloses a split coil array signal detection method and a detection device. The excitation coil of the detection device is a split coil array formed by a plurality of sub-coils that are pairwise symmetric on a horizontal plane. A magnetic field with a vector direction towards the center position of the excitation coil is generated through the rotating body structure of the split coil array, and the magnetic fields in the horizontal direction are mutually cancelled out through the pairwise symmetric arrangement. Further, since the induction coil and the excitation coil are axisymmetric about the same horizontal line, the vector sum of the horizontal components of the magnetic field generated by the excitation coil in the longitudinal direction is zero, thereby effectively weakening the magnetic field intensity generated by the excitation coil at the position of the induction coil.

Description

Technical Field

[0001] The present invention belongs to the technical field of eddy current testing, and particularly relates to a signal detection method and a detection device for a split coil array. Background Art

[0002] Existing pulsed eddy current transmitting and receiving devices generally adopt a central loop structure, where the excitation coil and the induction coil are on the same vertical line or in the same plane. The excitation magnetic field generated by the excitation coil coincides with the induction magnetic field generated by the object to be detected. The signal of the induction coil comes from the change of the magnetic field. Due to the aliasing of the excitation magnetic field and the induction magnetic field, the signal of the induction coil is not completely the signal of the induction magnetic field, and the excitation magnetic field generated by the excitation coil will cause great interference to signal acquisition. At the same time, in order to meet the signal acquisition requirements of the induction coil, the existing excitation coil and induction coil are placed at the same angle, which will result in a large mutual inductance coefficient between the two, thereby causing a large induced voltage in the induction coil by the excitation coil. During the signal processing, in order to remove the interference of the excitation coil, fine signal acquisition and complex calculations are usually required. Therefore, the aliasing of the excitation magnetic field and the induction magnetic field and the generation of the induced voltage will both lead to errors in pulsed eddy current detection and increase the complexity of pulsed eddy current signal processing.

[0003] In addition, the sensitivity of the coil is related to the self-inductance coefficient of the coil. The self-inductance coefficient of the induction coil of pulsed eddy current is generally achieved by increasing the radius and the number of turns of the coil. When the sensitivity of the induction coil is improved by increasing the number of turns of the coil, since the distributed capacitance of the induction coil itself will also increase when the number of turns increases, the simultaneous increase of the two will significantly reduce the cut-off frequency of the induction coil; when the sensitivity of the coil is improved by increasing the radius of the induction coil, in the case of a certain radius of the transmitting coil in the conventional central loop coil structure, due to the increase of the radius of the induction coil, the mutual inductance coefficient between the transmitting coil and the induction coil will increase accordingly, thereby causing the signal in the excitation coil to seriously interfere with the response signal in the induction coil.

[0004] Furthermore, the detection process of the existing eddy current probe depends on prior calibration. Usually, by changing the magnitude of the excitation current and obtaining the corresponding induction value, different shapes of defects are calibrated. In this process, rich calibration data cannot be obtained only by changing the magnitude of a single current. Summary of the Invention

[0005] In view of the technical problem of insufficient detection in the existing pulsed eddy current detection technology, a signal detection method for a split coil array is provided, including the following steps:

[0006] Step S1: Obtain the calibrated workpiece to be measured, activate the excitation coil, and move the excitation coil reciprocally above the workpiece to be measured for scanning; the excitation coil is a split coil array formed by a plurality of sub-coils that are pairwise symmetric on a horizontal plane, and the initial excitation current magnitudes in each sub-coil are the same and the directions are consistent;

[0007] Step S2: Obtain the induction value of the induction coil. When the change in the induction value exceeds a preset threshold, fix the position of the excitation coil and lock the defect position of the workpiece to be measured;

[0008] Step S3: Set the change threshold of the excitation current of the sub-coils. In the case of no workpiece to be measured, increase or decrease the excitation current of each sub-coil according to the change threshold, and obtain the induction value of the induction coil corresponding to the excitation current of each group of sub-coils as the reference value; detect the calibrated workpiece in Step S1, increase or decrease the excitation current of each sub-coil according to the same change threshold, obtain the induction value of the induction coil corresponding to the excitation current of each group of sub-coils as the detection induction value, and obtain the difference value between the detection induction value and the reference value of the induction coil to complete further calibration;

[0009] Step S4: According to the calibration data, use the least squares method to fit several groups of function curves with the calibration information of the workpiece to be measured as the independent variable and the corresponding difference value of the induction coil as the dependent variable, and use the least squares surface fitting algorithm based on a rectangular domain to fit the function curves into a continuous and smooth three-dimensional surface, so as to obtain the three-dimensional surface analytical formula;

[0010] The calibration data includes the calibration information of the workpiece to be measured, the calibration value of the excitation current, and the calibration value of the induction coil; the calibration information of the workpiece to be measured includes the defect depth, defect length, defect width, and defect radian of the workpiece to be measured; the calibration value of the induction coil includes the reference value and the difference value;

[0011] Step S5: Enter the actual measurement environment, activate the excitation coil, scan by reciprocally moving the excitation coil above the uncalibrated workpiece to be measured, obtain the induction value corresponding to the defect of the workpiece to be measured, and when the induction value is greater than the preset threshold, lock the position of the excitation coil; increase or decrease the excitation current of the sub-coils according to the preset change threshold, obtain the corresponding induction value as the detection induction value, and obtain the difference value of the induction coil based on this; import the difference value of the induction coil into the three-dimensional surface analytical formula to obtain the corresponding defect depth, defect length, defect width, and defect radian of the workpiece to be measured.

[0012] A split coil array signal detection device for implementing the above-mentioned split coil array signal detection method, the device includes:

[0013] An excitation coil in the shape of an annular frame, the excitation coil includes a plurality of sub-coils that are pairwise symmetric on a horizontal plane to form an array, and is used to generate an excitation magnetic field;

[0014] The induction coil is arranged at the central position of the excitation coil and includes a circular metal block and a first wire. The first wire is wound around the circular metal block and is used to receive the induced magnetic field;

[0015] The induction coil and the excitation coil are symmetrically arranged up and down based on the same horizontal line;

[0016] The sub-coils are centrosymmetric with respect to the center point of the excitation coil, and the current directions of the sub-coils are kept consistent;

[0017] The sub-coil includes a rotating body and a second wire. The through cavity of the rotating body penetrates in the horizontal plane and is arranged in pairs; the second wire is wound around the rotating body;

[0018] The rotating body includes a magnetic core inside and a rotating body housing wrapping the magnetic core. The rotating body housing is provided with a strip-shaped groove for accommodating the second wire. The rotating body includes an arc-shaped long side symmetrically arranged up and down and a short side symmetrically arranged left and right;

[0019] Each sub-coil is provided with an independent power supply device.

[0020] Further, the outer contour of the excitation coil is circular, and the sub-coil is arc-shaped.

[0021] Further, the number of the sub-coils is 4.

[0022] Further, the detection device further includes a housing made of an insulating material;

[0023] The housing is provided with an assembly groove matching the shapes of the excitation coil and the induction coil, and the excitation coil and the induction coil are fixed through the assembly groove.

[0024] Further, the arc-shaped long side includes a first arc-shaped long side at the upper part and a second arc-shaped long side at the lower part. The second wire starts to wind from one end of the first arc-shaped long side, winds along the first arc-shaped long side to the other end of the first arc-shaped long side, winds from the other end of the first arc-shaped long side along the corresponding short side to the non-homologous end of the second arc-shaped long side, and winds along the second arc-shaped long side to the homologous end of the second arc-shaped long side.

[0025] Further, one end of the first arc-shaped long side is docked with the positive pole of the power supply, and the homologous end of the second arc-shaped long side is docked with the negative pole of the power supply.

[0026] The positive progressive effect of the present invention is that:

[0027] 1) The present invention provides a split-type coil array signal detection device. By arranging the excitation coils of the detection device into several sub-coils that are symmetrically paired with each other on a horizontal plane to form an array, a magnetic field with a vector direction towards the center position of the excitation coil is generated through the rotating body structure arranged on the sub-coils, and the magnetic fields in the horizontal direction are cancelled one by one through the symmetrical arrangement; further, since the induction coil and the excitation coil are axisymmetric about the same horizontal line, the vector sum of the horizontal components of the magnetic field generated by the excitation coil in the longitudinal direction is zero, thereby effectively reducing the magnetic field intensity generated by the excitation coil at the position of the induction coil.

[0028] 2) The overall structure of the excitation coil composed of the sub-coil array adopted by the present invention can still be close to the excitation coil in the prior art in terms of size and shape. When used in actual eddy current detection, the cost of re-design is greatly reduced.

[0029] 3) By sequentially changing the magnitude of the excitation current of a single sub-coil of the excitation coil, the present invention can achieve the offset of the magnetic field vector direction of the excitation coil in the area of the object to be detected, thereby realizing the acquisition, analysis and calibration of detection signals at different angles of the object to be detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural diagram of a split-type coil array signal detection device of the present invention.

[0031] Figure 2 It is a structural diagram of a sub-coil of a split-type coil array signal detection device of the present invention.

[0032] Figure 3 It is a simulation diagram of the magnetic field generated by a single sub-coil of a split-type coil array signal detection device of the present invention.

[0033] Figure 4 It is a schematic structural diagram of an eddy current detection coil in the prior art.

[0034] Figure 5 It is a schematic diagram of the magnetic field distribution intensity generated by the excitation coil of an eddy current detection coil in the prior art.

[0035] Figure 6 It is a schematic diagram of the magnetic field distribution vector generated by the excitation coil of an eddy current detection coil in the prior art.

[0036] Figure 7 It is a schematic diagram of the magnetic field distribution intensity generated by a split-type coil array signal detection device of the present invention.

[0037] Figure 8 It is a schematic diagram of the magnetic field distribution intensity vector generated by a split-type coil array signal detection device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] The embodiments of the present invention will be described below through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0039] Referring to Figures 1 to 3 , a split coil array signal detection device, the device includes:

[0040] An excitation coil 1 in the shape of an annular frame, the excitation coil includes a plurality of sub-coils 11 symmetrically formed in pairs on the horizontal plane to form an array, and is used to generate an excitation magnetic field;

[0041] An induction coil 2 is arranged at the center position of the excitation coil, and includes a circular metal block and a first wire wound around the circular metal block, and is used to receive the induction magnetic field;

[0042] The induction coil 2 and the excitation coil 1 are symmetrically arranged up and down based on the same horizontal line;

[0043] The sub-coils 11 are centrosymmetric with respect to the center point of the excitation coil 1, and the current directions of the sub-coils 11 are kept consistent;

[0044] The sub-coil 11 includes a rotating body 111 and a second wire 112. The through cavity of the rotating body 111 penetrates in the horizontal plane and is arranged opposite to each other one by one; the second wire 112 is wound around the rotating body;

[0045] The rotating body 111 includes a magnetic core 111 in its interior and a rotating body outer shell 1112 wrapping the magnetic core. A strip-shaped groove 112A for accommodating the second wire 112 is provided on the rotating body outer shell 1112. The rotating body 111 includes arc-shaped long sides 111A symmetrically arranged up and down and short sides 111B symmetrically arranged left and right;

[0046] Each sub-coil is provided with an independent power supply device.

[0047] Further, the outer contour of the excitation coil 1 is circular, and the sub-coil 11 is arc-shaped.

[0048] Further, there are 4 sub-coils 11.

[0049] Further, in an example, not shown in the figure, the detection device further includes a housing, and the housing is made of insulating material;

[0050] The housing is provided with an assembly groove matching the shapes of the excitation coil 1 and the induction coil 2, and the excitation coil 1 and the induction coil 2 are fixed through the assembly groove.

[0051] Further, the long side of the arc strip includes a first long side of the arc strip at the upper side and a second long side of the arc strip at the lower side. The second wire 112 starts winding from one end of the first long side of the arc strip, winds along the first long side of the arc strip to the other end of the first long side of the arc strip, winds along the corresponding short side from the other end of the first long side of the arc strip to the non - same - side end of the second long side of the arc strip, and winds along the second long side of the arc strip to the same - side end of the second long side of the arc strip.

[0052] Further, one end of the first long side of the arc strip is connected to the positive pole of the power supply, and the same - side end of the second long side of the arc strip is connected to the negative pole of the power supply.

[0053] In an example, a split - type coil array signal detection method includes the following steps:

[0054] Step S1: Obtain a calibrated measured object, activate the excitation coil, and the excitation coil reciprocates above the measured object for scanning; the excitation coil is a split - type coil array formed by a plurality of sub - coils that are pairwise symmetric on a horizontal plane, and the initial excitation current magnitudes in each sub - coil are the same and the directions are consistent;

[0055] Step S2: Obtain the induction value of the induction coil. When the change in the induction value exceeds a preset threshold, fix the position of the excitation coil and lock the defect position of the measured object;

[0056] Step S3: Set the change threshold of the excitation current of the sub - coils. In the case of no measured object, increase or decrease the excitation current of each sub - coil according to the change threshold, and obtain the induction value of the induction coil corresponding to the excitation current of each group of sub - coils as the reference value; detect the calibrated measured object in Step S1, increase or decrease the excitation current of each sub - coil according to the same change threshold, obtain the induction value of the induction coil corresponding to the excitation current of each group of sub - coils as the detection induction value, and obtain the difference value between the detection induction value and the reference value of the induction coil to complete further calibration;

[0057] Step S4: According to the calibration data, use the least - squares method to fit a number of function curves with the calibration information of the measured object as the independent variable and the difference value of the corresponding induction coil as the dependent variable, and use the least - squares surface fitting algorithm based on a rectangular domain to fit the function curves into a continuous and smooth three - dimensional surface, so as to obtain the three - dimensional surface analytical formula;

[0058] The calibration data includes the calibration information of the measured object, the calibration value of the excitation current, and the calibration value of the induction coil; the calibration information of the measured object includes the defect depth, defect length, defect width, and defect radian of the measured object; the calibration value of the induction coil includes the reference value and the difference value;

[0059] Step S5: Enter the actual measurement environment, activate the excitation coil, scan by reciprocally moving the excitation coil above the uncalibrated DUT to obtain the induced value corresponding to the defect of the DUT. When the induced value is greater than the preset threshold, lock the position of the excitation coil; increase or decrease the excitation current of the sub-coil according to the preset change threshold, obtain the corresponding induced value as the detection induced value, and obtain the differential value of the induction coil based on this; import the differential value of the induction coil into the three-dimensional surface analytical formula to obtain the defect depth, defect length, defect width, and defect arc of the corresponding DUT.

[0060] It should be further noted that, in one example, the coil arrangement in the eddy current detection probe in the prior art is roughly as Figure 4 shown, and its corresponding magnetic field distribution diagram is as Figure 5 and Figure 6 shown. It can be seen from the figure that the magnetic field intensity generated by the excitation magnetic field at the position of the induction coil is relatively large, and the vector direction of the generated excitation magnetic field is orthogonal to the induction coil. The magnetic field aliasing near the induction coil is obvious, and the corresponding mutual inductance coefficient and induced voltage are both large, which will generate strong signal interference.

[0061] After adopting the split coil array structure provided by the present invention, referring to Figure 7 and Figure 8 , it can be seen that in the lower part of this structure, the overall synthesized magnetic field is still a magnetic field with a downward direction. During the pulsed eddy current detection process, the induction coil mainly senses the vertical component of the induced magnetic field generated by the eddy current in the object to be detected, while the excitation magnetic field is mainly a horizontal magnetic field in the induction coil area. Therefore, this structure can reduce or eliminate the interference of the excitation magnetic field and avoid the aliasing of the excitation magnetic field and the induced magnetic field, thereby improving the signal acquisition accuracy of the induction coil.

[0062] As a comparative illustration, referring to Table 1, it can be seen that under the same size, excitation, number of turns, the same induction coil, and the same simulation conditions, the mutual inductance coefficient and magnetic induction intensity at the induction coil are effectively weakened.

[0063] Table 1

[0064]

[0065] In one example, when the excitation coil of the present invention detects a target object, with the relative positions of the sub-coils and the induction coil fixed, it scans the entire detection area of the target object. During this process, the magnitudes of the excitation signals applied to each part of the excitation coil are equal and the phases are the same. After scanning the area to be measured and determining the position of the object to be detected, since the main component of the magnetic field generated by the excitation coil during the conventional detection process is vertically downward, when the target object is directly below, due to the influence of the pulsed eddy current skin effect, the eddy current signal is mainly generated by the part of the object to be measured perpendicular to the vertical component of the magnetic field. By sequentially changing the magnitude of the excitation current of a single sub-coil of the excitation coil, the offset of the magnetic field vector direction of the excitation coil in the area of the target object can be achieved, so as to realize the acquisition, analysis, and calibration of the detection signals of the target object at different angles.

[0066] The present invention has been described in detail with reference to the embodiments in the accompanying drawings. Those of ordinary skill in the art can make various variations to the present invention according to the above description. Therefore, certain details in the embodiments should not constitute a limitation to the present invention, and the present invention will be protected by the scope defined in the appended claims.

Claims

1. A split coil array signal detection method, characterized in that It includes the following steps: Step S1: Obtain the calibrated measured object, activate the excitation coil, and move the excitation coil reciprocally above the measured object for scanning; the excitation coil is a split coil array formed by a number of sub-coils that are pairwise symmetric on a horizontal plane, and the initial excitation current magnitudes in each sub-coil are the same and the directions are consistent; the induction coil is arranged at the central position of the excitation coil, and the induction coil and the excitation coil are symmetrically arranged up and down based on the same horizontal line; the sub-coils are centrosymmetric with respect to the center point of the excitation coil, and the current directions of the sub-coils remain consistent; Step S2: Obtain the induction value of the induction coil, and when the change in the induction value exceeds a preset threshold, fix the position of the excitation coil and lock the defect position of the measured object; Step S3: Set the change threshold of the excitation current of the sub-coils. In the case of no measured object, increase or decrease the excitation current of each sub-coil according to the change threshold, and obtain the induction value of the induction coil corresponding to the excitation current of each group of sub-coils as the reference value; detect the calibrated measured object in Step S1, increase or decrease the excitation current of each sub-coil according to the same change threshold, obtain the induction value of the induction coil corresponding to the excitation current of each group of sub-coils as the detection induction value, and obtain the difference value between the detection induction value and the reference value of the induction coil to complete further calibration; Step S4: According to the calibration data, use the least squares method to fit a number of function curves with the calibration information of the measured object as the independent variable and the difference value of the corresponding induction coil as the dependent variable, and fit the function curves into a continuous and smooth three-dimensional surface based on the least squares surface fitting algorithm of a rectangular domain, so as to obtain the three-dimensional surface analytical formula; The calibration data includes the calibration information of the measured object, the calibration value of the excitation current, and the calibration value of the induction coil; the calibration information of the measured object includes the defect depth, defect length, defect width, and defect radian of the measured object; the calibration value of the induction coil includes the reference value and the difference value; Step S5: Enter the actual measurement environment, activate the excitation coil, scan by reciprocally moving the excitation coil above the uncalibrated measured object, obtain the induction value corresponding to the defect of the measured object, and when the induction value is greater than the preset threshold, lock the position of the excitation coil; increase or decrease the excitation current of the sub-coils according to the preset change threshold, obtain the corresponding induction value as the detection induction value, and obtain the difference value of the induction coil based on this; import the difference value of the induction coil into the three-dimensional surface analytical formula to obtain the corresponding defect depth, defect length, defect width, and defect radian of the measured object.

2. A split coil array signal detection device for implementing the split coil array signal detection method described in claim 1, characterized in that, The device includes: An excitation coil in the shape of an annular frame, the excitation coil includes a number of sub-coils that are pairwise symmetric on a horizontal plane to form an array, and is used to generate an excitation magnetic field; An induction coil, arranged at the central position of the excitation coil, includes a circular metal block and a first wire, and the first wire is wound around the circular metal block and is used to receive the induction magnetic field; The induction coil and the excitation coil are symmetrically arranged up and down based on the same horizontal line; The sub-coils are centrosymmetric with respect to the center point of the excitation coil, and the current directions of the sub-coils remain consistent; The sub-coil includes a rotating body and a second wire. The through-cavity of the rotating body penetrates in the horizontal plane and is arranged in pairs; the second wire is wound around the rotating body; The rotating body includes a magnetic core inside and a rotating body housing wrapping the magnetic core. The rotating body housing is provided with a strip-shaped groove for accommodating the second wire. The rotating body includes arc-shaped long sides symmetrically arranged up and down and short sides symmetrically arranged left and right; Each sub-coil is provided with an independent power supply device.

3. The split coil array signal detection device according to claim 2, wherein The outer contour of the exciting coil is circular, and the sub-coil is arc-shaped.

4. The split coil array signal detection device according to claim 3, wherein The number of the sub-coils is 4 pieces.

5. The split coil array signal detection device according to claim 4, wherein The detection device further includes a housing, and the housing is made of insulating material; The housing is provided with an assembly groove matching the shapes of the exciting coil and the induction coil, and the exciting coil and the induction coil are fixed through the assembly groove.

6. The split coil array signal detection device according to claim 5, wherein, The arc-shaped long side includes a first arc-shaped long side at the upper part and a second arc-shaped long side at the lower part. The second wire starts to wind from one end of the first arc-shaped long side, winds along the first arc-shaped long side to the other end of the first arc-shaped long side, winds from the other end of the first arc-shaped long side along the corresponding short side to the non-homogeneous side end of the second arc-shaped long side, and winds along the second arc-shaped long side to the homogeneous side end of the second arc-shaped long side.

7. The split coil array signal detection device according to claim 6, characterized in that, One end of the first arc-shaped long side is docked with the positive pole of the power supply, and the homogeneous side end of the second arc-shaped long side is docked with the negative pole of the power supply.

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