Surface defect quality inspection method and device of sintered ferrite sheet and computer storage medium

Abstract

The invention belongs to the technical field of quality inspection analysis, and discloses a surface defect quality inspection method and device of a sintered ferrite sheet and a computer storage medium. The method comprises the following steps: positioning a sintered ferrite sheet, establishing a sheet coordinate system, and performing spatial registration with a magnetic response acquisition coordinate system; after the magnetic state of the sintered ferrite sheet is stable, applying a disturbed magnetic field with a direction change characteristic, and collecting magnetic response data in at least two different directions; extracting magnetic anisotropy characteristic parameters representing the degree of magnetic anisotropy based on the magnetic response data of the same detection position in different disturbing magnetic field directions; and acquiring surface topography information of the sintered ferrite sheet, and performing spatial correlation analysis on the magnetic anisotropy characteristic parameters and the surface topography information of the corresponding spatial position, so as to judge whether a defect that a surface defect is coupled with an in-vivo magnetic structure anomaly exists or not. According to the invention, the detection accuracy of the surface hidden defects of the sintered ferrite sheet can be improved.

Description

Technical Field

[0001] This invention relates to the field of quality inspection and analysis technology, specifically to a method, apparatus, and computer storage medium for inspecting surface defects in sintered ferrite sheets. Background Technology

[0002] Sintered ferrite sheets, as magnetic functional materials, are widely used in motors, electronic components, and magnetic assemblies. Their surface quality not only affects assembly reliability but also directly relates to the stability and consistency of the magnetic properties of the devices. In actual production, sintered ferrite sheets are typically required to have a clean surface and uniform color, and should be free from surface defects such as pits, bumps, edge warping, defects, exposed magnetism, and scratches (see [link to relevant documentation] for details on some defects). Figure 1 As shown in the figure, during subsequent bonding or assembly processes, the upper and lower adhesive layers should not exhibit any abnormalities such as wrinkles or delamination.

[0003] like Figure 2 As shown, existing quality inspection methods for surface defects in sintered ferrite sheets mainly rely on manual visual inspection, supplemented by simple measuring tools such as rulers, straightedges, vernier calipers, and micrometers, to measure and determine the width of pits, the height of protrusions, the warpage size, and the size of scratches. This type of method is effective in identifying larger, more obvious surface defects, but it still has the following shortcomings: (1) Existing methods mainly rely on the size, shape or height difference of visible defects on the surface to make judgments, which are difficult to reflect the internal microstructure of sintered ferrite sheets, such as abnormal grain orientation, local density inhomogeneity, microcracks or hidden pores.

[0004] (2) In practical applications, some sintered ferrite sheets have only tiny pits, minor scratches, or small protrusions on their surface. These defects are often deemed acceptable under existing visual inspection standards, but the magnetic anisotropy in the corresponding area changes abnormally, leading to uneven magnetic property distribution, increased losses, or decreased device consistency, which in turn causes performance failure or reliability problems in subsequent use. Existing visual or dimensional inspection methods are difficult to effectively identify these defects.

[0005] (3) Existing detection methods usually separate surface defects from magnetic property detection, making it impossible to determine whether a certain surface defect is coupled with an abnormal internal magnetic structure, which can easily lead to misjudgment or omission. This problem is particularly prominent in application scenarios with high consistency and high reliability requirements.

[0006] Therefore, there is an urgent need for a new method for inspecting surface defects in sintered ferrite sheets to overcome the shortcomings of the existing technology. Summary of the Invention

[0007] In view of the above-mentioned shortcomings mentioned in the background art, the purpose of this invention is to provide a method, device and computer storage medium for surface defect inspection of sintered ferrite sheets, which can identify internal magnetic structure anomalies coupled with surface defects without relying on obvious geometric defects, and realize effective detection of hidden and high-risk defects, thereby improving the reliability and pertinence of sintered ferrite sheet quality inspection.

[0008] A first aspect of the present invention provides a method for inspecting surface defects in sintered ferrite sheets, the method comprising the following steps: Step S1: Position the sintered ferrite sheet to be tested, establish the sheet coordinate system and spatially register it with the magnetic response acquisition coordinate system; Step S2: Apply magnetic excitation to the sintered ferrite sheet to make its magnetic state reach a stable state. Apply a perturbation magnetic field with direction-changing characteristics to the sintered ferrite sheet that has reached a stable state, so that the perturbation magnetic field acts on the sintered ferrite sheet in at least two different directions in the plane of the sintered ferrite sheet, and collect corresponding magnetic response data at multiple detection positions. Step S3: Based on the magnetic response data of the same detection location under different perturbed magnetic field directions, extract magnetic anisotropy characteristic parameters that characterize the degree of magnetic anisotropy at the detection location. Step S4: Obtain the surface morphology information of the sintered ferrite sheet, and perform spatial correlation analysis between the magnetic anisotropy characteristic parameters and the surface morphology information at the corresponding spatial location. Based on the spatial correlation analysis results, determine whether the sintered ferrite sheet has defects that couple surface defects with abnormal internal magnetic structure.

[0009] As an example, the magnetic anisotropy characteristic parameters include parameters that reflect the degree of difference in magnetic response in different directions, and directional parameters that characterize the trend of change of magnetic response under different perturbed magnetic field directions.

[0010] As an example, spatial correlation analysis is performed between the magnetic anisotropy characteristic parameters and the surface topography information at the corresponding spatial location, including: Based on the spatial overlap or spatial proximity between the spatial positions corresponding to the magnetic anisotropic characteristic parameters and the spatial positions corresponding to the surface morphology information, the degree of correlation between the two is determined.

[0011] As an example, spatial correlation analysis is used to determine whether sintered ferrite sheets have defects where surface defects are coupled with anomalies in the bulk magnetic structure, including: When the magnetic anisotropy characteristic parameters meet the preset abnormal conditions, and the surface morphology information at the corresponding spatial location meets the preset morphology conditions, it is determined that the sintered ferrite sheet has a defect in which surface defects are coupled with abnormal magnetic structure in the bulk.

[0012] As an example, when a PET adhesive layer has been applied to the surface of the sintered ferrite sheet, the method further includes: Magnetic response data are acquired at the same detection location at at least two different excitation frequencies, wherein the excitation frequencies include low-frequency excitation frequency and high-frequency excitation frequency; Based on the magnetic response data at the high-frequency excitation frequency and the low-frequency excitation frequency, an interface influence coefficient characterizing the degree of interface influence is constructed. By combining the interface influence coefficient and the magnetic anisotropy characteristic parameters, the sources of magnetic response anomalies at the detection location are distinguished to exclude magnetic response anomalies introduced by the PET adhesive layer or the adhesive-magnetic interface.

[0013] A second aspect of the present invention provides a surface defect inspection device for sintered ferrite sheets, the device comprising: The positioning and registration module is used to position the sintered ferrite sheet to be tested, establish the sheet coordinate system and spatially register it with the magnetic response acquisition coordinate system; The magnetic excitation and acquisition module is used to apply magnetic excitation to the sintered ferrite sheet to make its magnetic state reach a stable state, apply a perturbation magnetic field with direction-changing characteristics to the sintered ferrite sheet that has reached a stable state, so that the perturbation magnetic field acts on the sintered ferrite sheet in at least two different directions in the plane of the sintered ferrite sheet, and acquire corresponding magnetic response data at multiple detection positions. The magnetic anisotropy feature extraction module is used to extract magnetic anisotropy feature parameters that characterize the degree of magnetic anisotropy at the detection location based on the magnetic response data of the same detection location under different perturbed magnetic field directions. The spatial correlation analysis and judgment module is used to acquire the surface morphology information of the sintered ferrite sheet, and perform spatial correlation analysis between the magnetic anisotropy characteristic parameters and the surface morphology information at the corresponding spatial location. Based on the spatial correlation analysis results, it is determined whether the sintered ferrite sheet has defects that couple with surface defects and abnormal internal magnetic structure.

[0014] As an example, the magnetic anisotropy characteristic parameters include parameters that reflect the degree of difference in magnetic response in different directions, and directional parameters that characterize the trend of change of magnetic response under different perturbed magnetic field directions.

[0015] As an example, the spatial correlation analysis and determination module is specifically used to: determine the degree of correlation between the spatial position corresponding to the magnetic anisotropy characteristic parameters and the spatial position corresponding to the surface morphology information based on the spatial overlap or spatial proximity relationship between the two.

[0016] As an example, the spatial correlation analysis and determination module is also specifically used to: when the magnetic anisotropy characteristic parameters meet the preset abnormal conditions and the surface morphology information of the corresponding spatial position meets the preset morphology conditions, determine that the sintered ferrite sheet has a defect in which surface defects are coupled with an abnormal magnetic structure in the bulk.

[0017] As an example, when a PET adhesive layer has been attached to the surface of the sintered ferrite sheet, the magnetic excitation and acquisition module is configured as follows: Magnetic response data are acquired at the same detection location at at least two different excitation frequencies, wherein the excitation frequencies include low-frequency excitation frequency and high-frequency excitation frequency; Based on the magnetic response data at the high-frequency excitation frequency and the low-frequency excitation frequency, an interface influence coefficient characterizing the degree of interface influence is constructed. By combining the interface influence coefficient and the magnetic anisotropy characteristic parameters, the sources of magnetic response anomalies at the detection location are distinguished to exclude magnetic response anomalies introduced by the PET adhesive layer or the adhesive-magnetic interface.

[0018] A third aspect of the present invention also provides a computer storage medium having a computer program stored thereon, which, when executed by a processor, implements the method as described in any of the preceding claims.

[0019] Compared with the prior art, the present invention has the following significant advantages: 1. This invention describes the internal magnetic structure of sintered ferrite sheets from the perspective of magnetic anisotropy by applying a perturbed magnetic field with directional variation characteristics within the plane of the sintered ferrite sheet and extracting the differences in magnetic response and directional characteristics of the same detection position under different directions. This enables the identification of defects related to abnormal internal magnetic structure even when the surface geometric defects are small or the appearance is basically acceptable, thus overcoming the problem of easy omissions when relying solely on visual inspection or surface morphology detection.

[0020] 2. This invention performs spatial correlation analysis on magnetic anisotropy characteristic parameters and surface morphology information in a unified coordinate system. By analyzing the overlap or proximity of the two in space, it can distinguish between cases where there is only surface morphology abnormality but no accompanying magnetic structure abnormality, and cases where there is only magnetic structure abnormality but no obvious morphological features on the surface. This allows for the identification of defects coupled with internal magnetic structure abnormalities, improving the accuracy of defect determination and engineering applicability.

[0021] 3. For cases where a PET adhesive layer has been attached to the surface of sintered ferrite sheets, this invention collects magnetic response data at at least two different excitation frequencies and constructs an interface influence coefficient to distinguish the magnetic response changes introduced by the PET adhesive layer or adhesive-magnetic interface from the magnetic response changes caused by abnormalities in the bulk magnetic structure. This avoids misjudging the adhesive layer or interface effect as a bulk defect, thereby significantly improving the applicability of this method in actual production processes. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating typical types of surface defects in sintered ferrite sheets; among which, Figure 1 (a) is a pit defect. Figure 1 (b) is a convex defect. Figure 1 (c) is a defect.

[0023] Figure 2 A schematic diagram of existing quality inspection methods for surface defects in sintered ferrite sheets; Figure 3 This is a schematic diagram of the overall process of a surface defect inspection method for sintered ferrite sheets disclosed in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a surface defect inspection device for sintered ferrite sheets disclosed in an embodiment of the present invention. Detailed Implementation

[0024] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0025] Please see Figure 3 This invention provides a method for inspecting surface defects in sintered ferrite sheets, the method comprising the following steps: Step S1: Position the sintered ferrite sheet to be tested, establish the sheet coordinate system and spatially register it with the magnetic response acquisition coordinate system; In this step, the sintered ferrite sheet to be tested is first positioned and fixed. Specifically, the sintered ferrite sheet can be placed on a vacuum adsorption stage or a special fixture, and its translational and rotational degrees of freedom in the plane are constrained by negative pressure adsorption and mechanical limiting, so as to avoid the misalignment of the magnetic map and the morphology map caused by micro-displacement during subsequent magnetic excitation or scanning acquisition.

[0026] In some embodiments, the detection platform may be configured with a rotating mechanism to change the relative angle between the sintered ferrite sheet and the magnetic field direction during subsequent detection processes. The rotating mechanism may be driven by a stepper motor or a servo motor, and its rotation angle range may cover 0°-180°. The angle resolution may preferably be no greater than 0.1° to meet the angle accuracy requirements of magnetic anisotropy detection.

[0027] Subsequently, geometric references such as the edges, corners, or positioning holes of the sintered ferrite sheet were collected to establish a sheet coordinate system. Among them, the sheet coordinate system The center point of the sheet can be used as the origin, and the direction of the long side of the sheet or the direction of a preset reference side can be used as the coordinate axis direction to ensure that the coordinate system definition is consistent for sheets in the same batch under the same clamping method. It is understandable that the sheet coordinate system... This is used to describe the spatial coordinate relationship of any position on the surface of a sintered ferrite sheet within a plane. For example, the center position of the sintered ferrite sheet can be defined as the origin of the coordinate system, and the long side direction or a predetermined direction of the sintered ferrite sheet can be defined as the coordinate axis direction, thereby achieving a unified characterization of the position on the surface of the sintered ferrite sheet.

[0028] At the same time, establish a magnetic response acquisition coordinate system. Among them, the magnetic response acquisition coordinate system The installation reference can be determined by a two-dimensional Hall array or a scanning triaxial magnetic sensor. If necessary, the spatial mapping relationship of the sensor array (or scanning trajectory) in the platform coordinates can be obtained through target calibration or fixture calibration.

[0029] After completion and After establishing the coordinate transformation relationship between the two, the sampling points in the magnetic response acquisition coordinate system are mapped to their corresponding positions in the sheet coordinate system, thus ensuring that the subsequently generated magnetic response feature map and surface morphology / defect map correspond point-by-point (pixel-by-pixel). It should be noted that spatial registration may further include the calibration of the rotary platform's zero position, that is, the mechanical zero position of the rotary platform and the sheet coordinate system. The reference axis direction is aligned so that subsequent angle sweep implementation can drive acquisition with a unified angle reference.

[0030] Step S2: Apply magnetic excitation to the sintered ferrite sheet to make its magnetic state reach a stable state. Apply a perturbation magnetic field with direction-changing characteristics to the sintered ferrite sheet that has reached a stable state, so that the perturbation magnetic field acts on the sintered ferrite sheet in at least two different directions in the plane of the sintered ferrite sheet, and collect corresponding magnetic response data at multiple detection positions. In this step, after completing the spatial registration in step S1, magnetic excitation is applied to the sintered ferrite sheet to stabilize its magnetic state. The purpose of magnetic excitation is to reduce the impact of residual magnetic state differences introduced by historical magnetization, transportation, or assembly processes on the detection results. Specifically, magnetic excitation can be performed using an alternating magnetic field, gradually changing the magnetic field strength or frequency to cause the internal magnetic domain structure of the sintered ferrite sheet to undergo multiple flipping processes, thereby stabilizing the magnetic response; alternatively, a pulsed magnetic field can be used to magnetically excite the sintered ferrite sheet over multiple pulse cycles, gradually converging its magnetic response to a stable state.

[0031] After the sintered ferrite sheet reaches a stable magnetic state, a perturbation magnetic field with directional variation characteristics is applied to it, causing the perturbation magnetic field to act on the sintered ferrite sheet in at least two different directions within the plane of the sintered ferrite sheet. The directional variation perturbation can be achieved through the following two equivalent methods: (1) A rotating magnetic field is used for excitation to generate a perturbation magnetic field with constant amplitude and direction varying with time in the plane of the sheet. Its expression is:

[0032] in: Indicates the amplitude of the disturbing magnetic field; Indicates the angular frequency of the magnetic field rotation; and These represent orthogonal unit vectors located in the plane of the sintered ferrite sheet. Through the aforementioned rotating magnetic field excitation method, a magnetic field with constant amplitude and continuously changing direction over time can be formed within the plane of the sintered ferrite sheet, causing the perturbed magnetic field to act on the sintered ferrite sheet in at least two different directions within the sheet plane.

[0033] (2) The linearly polarized magnetic field maintains a fixed direction, and the relative angle θ between the magnetic field and the geometric axis of the sheet is changed by rotating the platform to achieve an equivalent directional sweep, resulting in a directional perturbation magnetic field that varies with the angle. Its expression is:

[0034] Here, θ represents the relative angle introduced by the rotating platform. The engineering advantage of this method is that the excitation coil can remain fixed in place, and the direction change is provided by the rotating platform, thereby reducing the complexity of excitation coil direction control.

[0035] During the perturbation magnetic field process, corresponding magnetic response data are collected at multiple detection positions of the sintered ferrite sheet. For example, a two-dimensional Hall array or a scanning triaxial magnetic sensor can be arranged above the sheet to collect local magnetic induction intensity; and a reference phase is set in the excitation coil, and the complex response at each position is obtained by phase-locked / synchronous sampling.

[0036] In this embodiment, each detection location The magnetic response is organized in complex form and forms a data cube according to frequency and direction (or angle). The complex representation is:

[0037] And its extended forms in multi-frequency, multi-angle sampling scenarios:

[0038] in, For amplitude terms, For phase terms, For the kth excitation frequency, Let l be the sampling point at the l-th angle. Using the above data organization method, a set of magnetic responses at the same detection location under multiple directions and frequencies can be obtained without changing the spatial mapping relationship of the sheet material.

[0039] Furthermore, to suppress phase offset or reference phase drift, a reference subtraction can be performed on the phase to obtain phase hysteresis characteristics:

[0040] in, The reference phase (which can be determined by the reference phase of the excitation coil or the phase of the reference region). This serves as the characteristic direction for subsequent directional analysis.

[0041] This step enables the acquisition of complex magnetic response data that varies with direction (or angle) at multiple detection locations and can be extended to multiple frequency and harmonic dimensions, which can be used for subsequent extraction of magnetic anisotropic characteristic parameters and surface-to-volume spatial coupling analysis.

[0042] In addition, second / third harmonic components can be collected to characterize magnetic domain nonlinearity and nonlinear magnetization caused by microcracks / pores. The harmonic amplitude ratio characteristic can be calculated for the same point using the following formula:

[0043] in, For fundamental frequency response, This represents the nth harmonic response. To ensure... The repeatability can be achieved by using the same synchronous sampling window for the fundamental and harmonic waves at each detection location, or by averaging multiple periods of data to reduce the impact of random noise.

[0044] To enhance the discriminability of penetration depth and interface effects, at least two different frequencies can be used. , Collect complex magnetic responses and construct interface influence coefficients:

[0045] in, For lower frequencies, At a relatively high frequency. Through The location distribution can provide a data basis for subsequent differentiation between cases dominated by in vivo abnormalities and those dominated by interface / surface influences.

[0046] Step S3: Based on the magnetic response data of the same detection location under different perturbed magnetic field directions, extract magnetic anisotropy characteristic parameters that characterize the degree of magnetic anisotropy at the detection location. In this step, for the same detection location For different perturbed magnetic field directions The magnetic response data acquired below is reorganized in terms of orientation dimension. Specifically, at a fixed spatial location... With fixed excitation frequency Under these conditions, the magnetic response data are indexed according to the direction of the perturbed magnetic field to form a sequence of directional responses at the detection location in multiple directions: .

[0047] To reduce the impact of gain differences, sensor sensitivity differences, or reference phase drift on the directional analysis results, the directional response sequence can be preprocessed, including normalizing the magnetic response amplitude or performing reference alignment on the magnetic response phase. The phase hysteresis characteristic obtained after phase reference alignment can be expressed as:

[0048] in, This is the reference phase, used to eliminate the common phase bias.

[0049] As an example, the magnetic anisotropy characteristic parameters include parameters that reflect the degree of difference in magnetic response in different directions, and directional parameters that characterize the trend of change of magnetic response under different perturbed magnetic field directions.

[0050] Parameters reflecting the degree of difference in magnetic response in different directions can be calculated based on the distribution of magnetic response amplitude along the directional dimension. Specifically, at the same detection location... and the same excitation frequency The maximum and minimum values ​​of the magnetic response amplitude are determined in the directional dimension, respectively:

[0051]

[0052] Based on this, the anisotropy ratio parameter of the magnetic response amplitude is calculated:

[0053] Through the above processing, the anisotropy ratio parameter can quantitatively characterize the non-uniformity of the magnetic response amplitude distribution at the same detection location under the action of different perturbation magnetic field directions.

[0054] Regarding the directional parameter characterizing the variation trend of the magnetic response under different perturbed magnetic field directions, in this embodiment, the magnetic response amplitude or phase can be analyzed in the directional dimension to determine the direction corresponding to when the magnetic response reaches its extreme value. Specifically, the perturbed magnetic field direction corresponding to when the magnetic response amplitude reaches its maximum value can be determined as the characteristic direction of the detection location, which is represented as follows: .in, The magnetic response amplitude reaches its maximum value in this direction. .

[0055] In addition, phase lag characteristics can be combined. To analyze the trend of magnetic response phase variation with the direction of perturbed magnetic field, so as to enhance the characterization ability of directional magnetic response behavior.

[0056] In embodiments involving multi-frequency acquisition, frequency-dimensional features can be introduced based on directional analysis. For example, interface-related frequency contrast features can be calculated based on magnetic response data acquired at different excitation frequencies, as expressed as:

[0057] in, and These represent lower and higher excitation frequencies, respectively.

[0058] In embodiments where harmonic acquisition is present, the harmonic ratio characteristic of the magnetic response can be further calculated, which characterizes the degree of nonlinearity of the magnetic response. It is expressed as:

[0059] After calculating the aforementioned magnetic anisotropy characteristic parameters, the various magnetic anisotropy characteristic parameters are spatially mapped according to the sheet coordinate system established in step S1, so that each detection position corresponds to a set of magnetic anisotropy characteristic parameters. Different types of magnetic anisotropy characteristic parameters can be organized as multi-channel feature data for further spatial correlation analysis in subsequent steps.

[0060] Step S4: Obtain the surface morphology information of the sintered ferrite sheet, and perform spatial correlation analysis between the magnetic anisotropy characteristic parameters and the surface morphology information at the corresponding spatial location. Based on the spatial correlation analysis results, determine whether the sintered ferrite sheet has defects that couple surface defects with abnormal internal magnetic structure.

[0061] In this embodiment, surface morphology information can be obtained through visual imaging, structured light scanning, laser profilometry, or other surface detection methods, and is used to characterize the geometric morphology features of the sintered ferrite sheet surface. The surface morphology information may include, but is not limited to, surface pits, protrusions, scratches, chipping, edge warping, and other morphological anomalies.

[0062] After obtaining the surface morphology information, the surface morphology information is mapped to the sheet coordinate system. In this way, each surface morphology feature corresponds to a specific spatial location in the sheet coordinate system. In some embodiments, geometric attribute parameters of each surface morphology feature, such as size, area, depth, or height, can be further extracted for use in constructing subsequent decision criteria.

[0063] After completing the spatial alignment of magnetic anisotropy characteristic parameters and surface morphology information, spatial correlation analysis is performed on the two to evaluate the spatial correspondence between magnetic response anomalies and surface morphology anomalies.

[0064] As an example, the spatial correlation analysis of the magnetic anisotropy characteristic parameters with the surface topography information of the corresponding spatial location includes: Based on the spatial overlap or spatial proximity between the spatial positions corresponding to the magnetic anisotropic characteristic parameters and the spatial positions corresponding to the surface morphology information, the degree of correlation between the two is determined.

[0065] In this embodiment, each detection location can be targeted. Determine whether it simultaneously meets one of the following spatial conditions: the abnormal position of the magnetic anisotropy characteristic parameter coincides with the abnormal position of a certain surface morphology in space; or the abnormal position of the magnetic anisotropy characteristic parameter is located within a preset neighborhood of the abnormal position of the surface morphology.

[0066] In some embodiments, the spatial coupling consistency parameter between magnetic anomalies and surface anomalies can be calculated based on the above spatial relationship, and it is expressed as follows: .in, Used to characterize spatial location The degree of spatial consistency between magnetic anisotropy anomalies and surface morphology anomalies is considered. The consistency parameter can be constructed by comprehensively considering factors such as spatial overlap ratio, proximity distance, or area of ​​associated regions; however, the specific calculation formula is not limited in this invention.

[0067] After completing the spatial correlation analysis, the magnetic anomaly intensity and the surface anomaly intensity are further jointly characterized. In this embodiment, a magnetic anomaly intensity index can be constructed based on the magnetic anisotropy characteristic parameters obtained in step S3, which is expressed as follows: .in, Used for comprehensive characterization of detection location The significance of the magnetic anisotropy anomaly can be obtained by combining multiple magnetic anisotropy characteristic parameters according to a preset weight, and the specific calculation formula is not limited in this invention.

[0068] At the same time, a surface anomaly intensity index can be constructed based on surface morphology information, which is represented as: .in, Used to characterize the detection location The degree of significance of surface morphology anomalies can be quantified by the size, type, or geometric characteristics of surface defects.

[0069] Obtaining spatial coupling consistency parameters Magnetic anomaly intensity index and surface abnormal strength index Then, a comprehensive analysis of the three factors is conducted to determine whether there is a defect in which surface defects are coupled with abnormal magnetic structures within the body.

[0070] As an example, spatial correlation analysis is used to determine whether sintered ferrite sheets have defects where surface defects are coupled with anomalies in the bulk magnetic structure, including: When the magnetic anisotropy characteristic parameters meet the preset abnormal conditions, and the surface morphology information at the corresponding spatial location meets the preset morphology conditions, it is determined that the sintered ferrite sheet has a defect in which surface defects are coupled with abnormal magnetic structure in the bulk.

[0071] A coupling defect assessment index can be further constructed to comprehensively evaluate the risk of surface-bulk coupling, which is expressed as:

[0072] in, Used to characterize at the detection location The degree of coupling risk between surface defects and anomalies in the bulk magnetic structure. When the... When the value exceeds a preset threshold, it can be determined that there is a surface-to-volume coupling defect at that location that poses a potential risk to functional impact.

[0073] As an example, when a PET adhesive layer has been applied to the surface of the sintered ferrite sheet, the method further includes: Magnetic response data are acquired at the same detection location at at least two different excitation frequencies, wherein the excitation frequencies include low-frequency excitation frequency and high-frequency excitation frequency; Based on the magnetic response data at the high-frequency excitation frequency and the low-frequency excitation frequency, an interface influence coefficient characterizing the degree of interface influence is constructed. By combining the interface influence coefficient and the magnetic anisotropy characteristic parameters, the sources of magnetic response anomalies at the detection location are distinguished to exclude magnetic response anomalies introduced by the PET adhesive layer or the adhesive-magnetic interface.

[0074] After sintering and preliminary processing, PET adhesive layers may be attached to the surface of sintered ferrite sheets. In this case, the PET adhesive layer and the adhesive-magnetic interface may have additional effects on the amplitude and phase of the magnetic response under the action of an alternating magnetic field, thereby interfering with defect determination based on magnetic response anomalies.

[0075] At the same detection location At the low-frequency excitation frequency, respectively With high frequency excitation frequency A perturbation magnetic field was applied to the sintered ferrite sheet, and the corresponding magnetic response data were collected.

[0076] The magnetic response data is expressed in complex form as follows: .in, , Indicates the amplitude of the magnetic response. Indicates the phase of the magnetic response.

[0077] Using the above method, at the same detection location Low-frequency magnetic responses were obtained at the respective locations. With high frequency magnetic response .

[0078] After completing the dual-frequency magnetic response data acquisition, an interface influence coefficient characterizing the degree of interface influence is constructed based on the high-frequency and low-frequency magnetic responses. Its definition is:

[0079] in, This represents the magnitude of the magnetic response.

[0080] In this embodiment, the interface influence coefficient is used to characterize the degree of change in high-frequency magnetic response relative to low-frequency magnetic response at the same spatial location. Since the low-frequency magnetic response has a strong penetrating ability to the magnetic structure within the sintered ferrite sheet, while the high-frequency magnetic response is more easily affected by the PET adhesive layer and the adhesive-magnetic interface conditions, therefore, when... When abnormal changes occur, it indicates that the magnetic response at the detection location may be significantly affected by interface factors.

[0081] In some embodiments, the interface influence coefficient may also be normalized, for example:

[0082] in, This represents the average value of the interface influence coefficient obtained statistically within the reference area or normal area, used to reduce the impact of overall operating condition changes on the judgment results.

[0083] In this embodiment, the interface influence coefficient is jointly analyzed with the magnetic anisotropy characteristic parameters extracted in step S3 to distinguish the sources of magnetic response anomalies. The magnetic anisotropy characteristic parameters may include anisotropy ratio parameters. and directional parameters When one of the following conditions is met, the abnormal magnetic response can be determined to be more likely to be introduced by the PET adhesive layer or the adhesive-magnetic interface: ,and .in, This is the preset threshold for the interface influence coefficient. This is the preset anomaly threshold for the magnetic anisotropy ratio parameter.

[0084] Accordingly, when the following conditions are met, it can be determined that the magnetic response anomaly is more likely to originate from an abnormal magnetic structure within the sintered ferrite sheet: Or under low-frequency excitation conditions, .

[0085] It is understandable that even the interface influence coefficient Simultaneous changes do not affect the determination of abnormal magnetic structures within the body.

[0086] Through the above dual-frequency magnetic response analysis and criterion construction, in the case where a PET adhesive layer has been attached, it is possible to distinguish between magnetic response anomalies introduced by the PET adhesive layer or the adhesive-magnetic interface and magnetic response anomalies caused by abnormalities in the internal magnetic structure.

[0087] In this embodiment, the detection location is included in the subsequent determination process of surface defects coupled with internal magnetic structure anomalies only when the magnetic anisotropy characteristic parameters meet the preset anomaly conditions and the corresponding anomaly still holds under low-frequency excitation conditions; magnetic response anomalies caused solely by interface influence coefficient anomalies are excluded in the defect determination.

[0088] Please see Figure 4 This invention also provides a surface defect inspection device 100 for sintered ferrite sheets, the device comprising: The positioning and registration module 101 is used to position the sintered ferrite sheet to be tested, establish the sheet coordinate system and spatially register it with the magnetic response acquisition coordinate system. The magnetic excitation and acquisition module 102 is used to apply magnetic excitation to the sintered ferrite sheet to make its magnetic state reach a stable state, apply a perturbation magnetic field with direction-changing characteristics to the sintered ferrite sheet that has reached a stable state, so that the perturbation magnetic field acts on the sintered ferrite sheet in at least two different directions in the plane of the sintered ferrite sheet, and acquire corresponding magnetic response data at multiple detection positions. The magnetic anisotropy feature extraction module 103 is used to extract magnetic anisotropy feature parameters that characterize the degree of magnetic anisotropy at the detection location based on the magnetic response data of the same detection location under different perturbed magnetic field directions. The spatial correlation analysis and judgment module 104 is used to acquire the surface morphology information of the sintered ferrite sheet, and perform spatial correlation analysis between the magnetic anisotropy characteristic parameters and the surface morphology information at the corresponding spatial position. Based on the spatial correlation analysis results, it is determined whether the sintered ferrite sheet has defects that couple with surface defects and abnormal magnetic structure in the bulk.

[0089] As an example, the magnetic anisotropy characteristic parameters include parameters that reflect the degree of difference in magnetic response in different directions, and directional parameters that characterize the trend of change of magnetic response under different perturbed magnetic field directions.

[0090] As an example, the spatial correlation analysis and determination module 104 is specifically used to: determine the degree of correlation between the spatial position corresponding to the magnetic anisotropy characteristic parameters and the spatial position corresponding to the surface morphology information based on the spatial overlap or spatial proximity relationship between the two.

[0091] As an example, the spatial correlation analysis and determination module 104 is also specifically used to: when the magnetic anisotropy characteristic parameters meet the preset abnormal conditions and the surface morphology information of the corresponding spatial position meets the preset morphology conditions, determine that the sintered ferrite sheet has a defect in which surface defects are coupled with an abnormal magnetic structure in the bulk.

[0092] As an example, when a PET adhesive layer has been attached to the surface of the sintered ferrite sheet, the magnetic excitation and acquisition module 102 is configured as follows: Magnetic response data are acquired at the same detection location at at least two different excitation frequencies, wherein the excitation frequencies include low-frequency excitation frequency and high-frequency excitation frequency; Based on the magnetic response data at the high-frequency excitation frequency and the low-frequency excitation frequency, an interface influence coefficient characterizing the degree of interface influence is constructed. By combining the interface influence coefficient and the magnetic anisotropy characteristic parameters, the sources of magnetic response anomalies at the detection location are distinguished to exclude magnetic response anomalies introduced by the PET adhesive layer or the adhesive-magnetic interface.

[0093] This invention also provides a computer storage medium storing a computer program thereon, which, when executed by a processor, implements the method described in any of the preceding claims.

[0094] While the spirit and principles of the invention have been described with reference to several specific embodiments, it should be understood that the invention is not limited to the disclosed specific embodiments, and the division of aspects does not imply that features in these aspects cannot be combined for benefit; such division is merely for ease of description. The invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for inspecting surface defects in sintered ferrite sheets, characterized in that, The method includes the following steps: Step S1: Position the sintered ferrite sheet to be tested, establish the sheet coordinate system and spatially register it with the magnetic response acquisition coordinate system; Step S2: Apply magnetic excitation to the sintered ferrite sheet to make its magnetic state reach a stable state. Apply a perturbation magnetic field with direction-changing characteristics to the sintered ferrite sheet that has reached a stable state, so that the perturbation magnetic field acts on the sintered ferrite sheet in at least two different directions in the plane of the sintered ferrite sheet, and collect corresponding magnetic response data at multiple detection positions. Step S3: Based on the magnetic response data of the same detection location under different perturbed magnetic field directions, extract magnetic anisotropy characteristic parameters that characterize the degree of magnetic anisotropy at the detection location. Step S4: Obtain the surface morphology information of the sintered ferrite sheet, and perform spatial correlation analysis between the magnetic anisotropy characteristic parameters and the surface morphology information at the corresponding spatial location. Based on the spatial correlation analysis results, determine whether the sintered ferrite sheet has defects that couple surface defects with abnormal internal magnetic structure.

2. The surface defect inspection method for sintered ferrite sheets according to claim 1, characterized in that: The magnetic anisotropy characteristic parameters include parameters that reflect the degree of difference in magnetic response in different directions, and directional parameters that characterize the trend of change of magnetic response under different perturbed magnetic field directions.

3. The surface defect inspection method for sintered ferrite sheets according to claim 2, characterized in that: Spatial correlation analysis is performed between the magnetic anisotropy characteristic parameters and the surface topography information at the corresponding spatial locations, including: Based on the spatial overlap or spatial proximity between the spatial positions corresponding to the magnetic anisotropic characteristic parameters and the spatial positions corresponding to the surface morphology information, the degree of correlation between the two is determined.

4. The surface defect inspection method for sintered ferrite sheets according to claim 3, characterized in that: Based on the spatial correlation analysis results, it was determined whether the sintered ferrite sheet had defects that coupled with surface defects and abnormal bulk magnetic structure, including: When the magnetic anisotropy characteristic parameters meet the preset abnormal conditions, and the surface morphology information at the corresponding spatial location meets the preset morphology conditions, it is determined that the sintered ferrite sheet has a defect in which surface defects are coupled with abnormal magnetic structure in the bulk.

5. The surface defect inspection method for sintered ferrite sheets according to claim 1, characterized in that: When a PET adhesive layer has been attached to the surface of the sintered ferrite sheet, the method further includes: Magnetic response data are acquired at the same detection location at at least two different excitation frequencies, wherein the excitation frequencies include low-frequency excitation frequency and high-frequency excitation frequency; Based on the magnetic response data at the high-frequency excitation frequency and the low-frequency excitation frequency, an interface influence coefficient characterizing the degree of interface influence is constructed. By combining the interface influence coefficient and the magnetic anisotropy characteristic parameters, the sources of magnetic response anomalies at the detection location are distinguished to exclude magnetic response anomalies introduced by the PET adhesive layer or the adhesive-magnetic interface.

6. A surface defect inspection device for sintered ferrite sheets, characterized in that: The device includes: The positioning and registration module is used to position the sintered ferrite sheet to be tested, establish the sheet coordinate system and spatially register it with the magnetic response acquisition coordinate system; The magnetic excitation and acquisition module is used to apply magnetic excitation to the sintered ferrite sheet to make its magnetic state reach a stable state, apply a perturbation magnetic field with direction-changing characteristics to the sintered ferrite sheet that has reached a stable state, so that the perturbation magnetic field acts on the sintered ferrite sheet in at least two different directions in the plane of the sintered ferrite sheet, and acquire corresponding magnetic response data at multiple detection positions. The magnetic anisotropy feature extraction module is used to extract magnetic anisotropy feature parameters that characterize the degree of magnetic anisotropy at the detection location based on the magnetic response data of the same detection location under different perturbed magnetic field directions. The spatial correlation analysis and judgment module is used to acquire the surface morphology information of the sintered ferrite sheet, and perform spatial correlation analysis between the magnetic anisotropy characteristic parameters and the surface morphology information at the corresponding spatial location. Based on the spatial correlation analysis results, it is determined whether the sintered ferrite sheet has defects that couple with surface defects and abnormal internal magnetic structure.

7. The surface defect inspection device for sintered ferrite sheets according to claim 6, characterized in that: The magnetic anisotropy characteristic parameters include parameters that reflect the degree of difference in magnetic response in different directions, and directional parameters that characterize the trend of change of magnetic response under different perturbed magnetic field directions.

8. The surface defect inspection device for sintered ferrite sheets according to claim 7, characterized in that: The spatial correlation analysis and determination module is specifically used to: determine the degree of correlation between the spatial position corresponding to the magnetic anisotropy characteristic parameters and the spatial position corresponding to the surface morphology information based on the spatial overlap or spatial proximity relationship between the two.

9. A surface defect inspection device for sintered ferrite sheets according to claim 8, characterized in that: The spatial correlation analysis and determination module is further specifically used to: when the magnetic anisotropy characteristic parameters meet the preset abnormal conditions and the surface morphology information of the corresponding spatial position meets the preset morphology conditions, determine that the sintered ferrite sheet has a defect in which surface defects are coupled with abnormal magnetic structure in the bulk.

10. A computer storage medium storing a computer program thereon, characterized in that: When the computer program is executed by a processor, it implements the method as described in any one of claims 1-5.

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