Aluminum plate strip surface defect detection device and method

Abstract

The application discloses an aluminum plate strip surface defect detection device and method. The device comprises a placing table, driving mechanisms symmetrically arranged on both sides, a limiting mechanism, an image acquisition mechanism and a light source emitting mechanism. The driving mechanism adopts a belt circulating rotation with V-shaped groove protrusions to realize non-destructive locking driving of the edge of the aluminum plate strip; the placing table is provided with a trapezoidal guide table to assist the connection of the end of the plate. The core feature is that the light source emitting mechanism utilizes a lead screw transmission to drive the lighting lamp to reciprocate linearly along the advancing direction of the aluminum plate strip, thereby providing dynamic and multi-angle illumination, so that the mirror reflection feature produces physical displacement with the change of the light source position. The application effectively solves the environmental light misjudgment problem in the detection of high reflectivity materials by using the physical light and shadow displacement law, and significantly improves the accuracy, reliability and automation level of industrial online detection.

Description

Technical Field

[0001] This invention relates to the field of aluminum processing and inspection technology, specifically to an apparatus and method for detecting surface defects in aluminum sheets and strips. Background Technology

[0002] In the production and processing of aluminum sheets and strips, surface quality is an important indicator for measuring their grade. Due to the high reflectivity of the aluminum sheet and strip surface, when using machine vision for surface defect detection, ambient light or illumination light can easily form speckled reflection spots on the aluminum surface.

[0003] Existing inspection equipment often uses fixed-angle light sources. When reflected spots coincide with surface defects, image acquisition equipment struggles to distinguish between actual physical defects and light interference, easily leading to misjudgments. Furthermore, during automated conveying processes, excessive pressure from the drive mechanism on the aluminum surface can easily cause secondary scratches. Therefore, eliminating reflection interference and achieving non-destructive, stable drive is a problem that needs to be solved in the field of aluminum inspection. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a device and method for detecting surface defects in aluminum plates and strips.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a surface defect detection device for aluminum sheet and strip, comprising: A placement platform for supporting the aluminum sheet / strip to be tested; A drive mechanism is provided on the left and right sides of the placement platform to drive the aluminum strip to move along the travel direction; The limiting mechanism has two sets, which are respectively set at the entry end and exit end of the aluminum strip on the placement platform, for guiding and pressing the aluminum strip; An image acquisition mechanism is mounted directly above the two sets of limiting mechanisms to acquire image information of the surface of the aluminum strip. A light source emitting mechanism is disposed on at least one side of the aluminum plate strip and is used to emit detection light onto the aluminum plate strip; The light source emitting mechanism includes a lead screw transmission mechanism and a lighting lamp installed on the movable end of the lead screw transmission mechanism. The lead screw transmission mechanism drives the lighting lamp to reciprocate linearly along the traveling direction of the aluminum strip to provide multi-angle illumination light to the aluminum strip that varies along the traveling direction, so that the specular reflection characteristics of the aluminum strip surface are displaced as the position of the lighting lamp changes.

[0006] Furthermore, the light source emitting mechanism is provided in two sets, and the two sets of light source emitting mechanisms are symmetrically arranged on both sides of the aluminum plate strip.

[0007] Furthermore, the upper surface of the placement platform is provided with an upwardly raised guide platform, which includes a platform in the middle and ramps at both ends of the platform, and the cross-section of the guide platform is trapezoidal.

[0008] Furthermore, the drive mechanism includes a motor, a drive wheel, a driven wheel, a belt, and multiple protrusions; The motor drives the drive wheel to rotate, and the belt is taut between the drive wheel and the driven wheel; The multiple protrusions are equidistantly distributed along the rotation direction of the belt, and each protrusion has a V-shaped groove at the end away from the belt, which is used to engage with the edge of the aluminum strip.

[0009] Furthermore, the limiting mechanism includes a lifting mechanism and a roller disposed on the movable end of the lifting mechanism. The lifting mechanism is used to adjust the height of the roller to adapt to aluminum strips of different thicknesses.

[0010] Furthermore, the image acquisition mechanism includes an industrial camera, the shutter sampling frequency of which corresponds to the reciprocating motion state of the lighting lamp.

[0011] The present invention also provides a method for detecting surface defects in aluminum plates and strips based on the above-mentioned device, comprising the following steps: Step S1: Place the aluminum strip to be tested on the placement platform, and use the V-groove of the protrusion in the driving mechanism to engage the edge of the aluminum strip, and use the limiting mechanism to press and limit it. Step S2: The driving mechanism moves the aluminum plate strip to the inspection station; Step S3: Start the light source emitting mechanism, use the lead screw transmission mechanism to drive the lighting lamp to move back and forth within a preset stroke, and at the same time use the image acquisition mechanism to continuously acquire multiple frames of original images when the lighting lamp is at different spatial coordinates; Step S4: Perform spatiotemporal difference fusion processing on the multiple original images and compare the displacement patterns of feature points in the images under different illumination angles; Step S5: Identify and remove specular reflection interference points that are displaced or disappear as the lighting lamp moves, wherein the displacement direction of the specular reflection interference points is related to the movement direction of the lighting lamp; retain feature points with fixed physical positions as real surface defects, and output the detection results.

[0012] Furthermore, in step S4, the surface defect is reconstructed in three dimensions, either in depth or height, by calculating the change in shadow length of the same feature point under different illumination angles.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention drives the lighting lamp to reciprocate linearly along the direction of travel through a lead screw transmission mechanism, realizing the acquisition of multiple frames of images of the same detection area under different lighting angles. It uses the light and shadow displacement law to distinguish physical defects from environmental interference, and solves the problem of misjudgment caused by specular reflection on highly reflective surfaces.

[0014] 2. By setting a drive belt with V-groove protrusions, the present invention achieves lateral locking drive of the aluminum strip edge, avoiding direct contact and squeezing of the aluminum strip surface by the drive mechanism, and reducing the risk of secondary surface scratches during the conveying process.

[0015] 3. By setting a trapezoidal guide platform, the present invention achieves pre-tilting of the ends of the aluminum strip, which helps the edge of the aluminum strip to smoothly enter the V-groove of the drive mechanism and improves the smoothness of automated loading and unloading.

[0016] 4. This invention adjusts the height of the limiting rollers through a lifting mechanism, thereby achieving stable positioning of aluminum strips of different thicknesses, preventing the strips from deviating or shaking during travel, and ensuring the stability of image acquisition.

[0017] 5. This invention achieves automatic filtering of pseudo-defect features that dynamically change with the movement of the light source by performing spatiotemporal difference fusion processing on multiple frames of images, thereby improving the accuracy of the detection system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall three-dimensional structure of an aluminum plate and strip surface defect detection device according to the present invention; Figure 2 This is a schematic diagram of the placement platform in this invention; Figure 3 This is a three-dimensional structural diagram of the driving mechanism in this invention; Figure 4 This is a three-dimensional structural diagram of the limiting mechanism in this invention; Figure 5 This is a three-dimensional structural diagram of the image acquisition mechanism in this invention; Figure 6 This is a three-dimensional structural diagram of the light source emitting mechanism in this invention.

[0019] In the diagram: 1. Placement platform; 2. Drive mechanism; 201. Motor; 202. Drive wheel; 203. Driven wheel; 204. Belt; 205. Protrusion; 3. Limiting mechanism; 301. Lifting mechanism; 302. Roller; 4. Image acquisition mechanism; 401. Industrial camera; 5. Light source emission mechanism; 501. Screw transmission mechanism; 502. Lighting lamp. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0023] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] Reference Figures 1 to 6 This invention discloses a surface defect detection device for aluminum strip, the main structure of which is built on a placement platform 1. Before the detection operation begins, the aluminum strip is placed at the starting end of the placement platform 1. To solve the problem of the initial end of the aluminum strip being difficult to smoothly connect with the subsequent driving components, the upper surface of the placement platform 1 is machined with an upwardly raised guide platform. The guide platform has a trapezoidal cross-section, consisting of a horizontal platform in the middle and symmetrical ramps at both ends. When the aluminum strip is pushed in, its front end first slides along the front ramp of the guide platform to the middle platform. This trapezoidal structure slightly raises the edge of the aluminum strip to a specific height, so that its sides can be accurately aligned and engaged with the corresponding position of the driving mechanism 2. This method of guiding by physical slope realizes the automatic alignment of the aluminum strip end without manual intervention, ensuring the smoothness of subsequent continuous conveying.

[0025] The drive mechanism 2 is symmetrically distributed on the left and right sides of the placement platform 1, responsible for providing power for the aluminum strip to move forward. The core power source of the drive mechanism 2 is a motor 201. The output end of the motor 201 is connected to the drive wheel 202, which drives the driven wheels 203, which are spaced apart, to rotate through the tensioned belt 204. Multiple protrusions 205 are fixed to the outer surface of the belt 204 at equal intervals, and each protrusion 205 has a V-groove engraved on the end away from the belt. When the aluminum strip is lifted by the guide platform, its left and right edges are respectively embedded in the V-grooves of the protrusions 205 on the two sides of the belt 204. After the motor 201 starts, it drives the belt 204 to rotate cyclically, and the protrusions 205 apply a horizontal tension to the aluminum strip through the side wall support of the V-groove. Since the driving force acts on the edge of the aluminum strip rather than the upper and lower surfaces, this structure realizes lateral locking drive, avoiding the indentations or scratches that may be caused by the direct pressing of the aluminum strip surface by the traditional pressure roller mechanism, and meeting the requirements of high-precision aluminum strip for surface-loss-free transmission.

[0026] At the entry and exit ends of the aluminum strip's running path, a set of limiting mechanisms 3 are provided. Each limiting mechanism 3 includes a lifting mechanism 301 and a roller 302 connected to its movable end. During the inspection process, the lifting mechanism 301 drives the roller 302 downward, pressing it against the upper surface of the aluminum strip. The main function of the roller 302 is to provide vertical downward limiting pressure, ensuring that the edge of the aluminum strip is firmly secured within the V-groove of the protrusion 205, preventing lateral deviation or vertical jolting of the strip during travel. By adjusting the stroke of the lifting mechanism 301, the device can adapt to aluminum strips of different thicknesses. After the aluminum strip enters the inspection station, the motor 201 continues to move or pauses briefly according to the inspection command. At this time, the limiting mechanism 3 maintains a pressing state, providing a stable focal plane for subsequent image acquisition and reducing image blurring caused by strip vibration.

[0027] Image acquisition mechanism 4 is positioned directly above the inspection station, and its core component is an industrial camera 401 that shoots vertically downwards. Simultaneously operating with image acquisition are light source emitting mechanisms 5 located on both sides of the sheet metal. Illumination lamps 502 in the light source emitting mechanism 5 are mounted on sliders of a lead screw drive mechanism 501. During the acquisition phase, the lead screw drive mechanism 501 drives the illumination lamps 502 to perform high-frequency reciprocating linear motion along the aluminum strip's travel direction. Because the spatial position of the illumination lamps 502 is constantly changing, when the light emitted by them illuminates the highly reflective surface of the aluminum strip, the resulting specular reflection area will produce significant displacement or brightness abrupt changes in the image frame. The sampling frequency of the industrial camera 401 is correlated with the movement state of the illumination lamps 502, ensuring that multiple frames of original images are captured when the illumination lamps 502 are at different spatial coordinate points. This dynamic light source setup transforms the fixed interference under static lighting into dynamic light and shadow, providing a data foundation for subsequent logical judgment.

[0028] After acquiring multiple frames of image data, the detection system first performs grayscale conversion and noise reduction preprocessing on the image sequence to improve the clarity of feature extraction. During processing, the system initially locates suspected feature points using edge detection or texture extraction algorithms and establishes a pixel coordinate system. The system compares the feature performance of the same detection area under different illumination angles: For real physical defects, such as pits, cracks, or scratches, their physical position remains unchanged on the aluminum strip surface. Therefore, in the spatial coordinates corresponding to multiple consecutive frames of images, the coordinate offset of the feature center point is within a preset minimum threshold range, mainly manifested as fine adjustment of grayscale values ​​or movement of shadow areas with changes in illumination angle. Conversely, for ambient stray light or specular reflection spots formed by illumination lamp 502, their imaging position strictly follows the optical reflection law and will produce significant, directional displacement in the pixel coordinate system with the linear movement of the illumination lamp 502 position, or disappear directly at certain angles because the light no longer enters the field of view of the industrial camera 401. The system identifies and eliminates interference points whose displacement vectors are related to the trajectory of the light source by comparing the motion vectors of suspected feature points with the motion parameters of the lighting lamp 502, thereby locking the coordinates of the real defects with fixed positions.

[0029] For the identified defects, the system further utilizes photometric stereo vision principles for analysis. For example, by comparing the changes in shadow length L and shadow direction formed by the same defect under different known light source positions, combined with the real-time spatial coordinates of the lighting lamp 502 on the lead screw drive mechanism 501, the system analyzes the defects. By using a trigonometric geometric model, the local normal vector of the defect surface is derived. Therefore, the system can not only identify the planar location of the defect but also deduce its microscopic depth information, thereby achieving three-dimensional morphological reconstruction of defects on the aluminum sheet / strip surface. This provides objective and accurate data for subsequent quality grading and production process traceability.

[0030] In summary, this device, through the coordinated operation of the placement platform 1, driving mechanism 2, limiting mechanism 3, image acquisition mechanism 4, and light source emitting mechanism 5, achieves automatic alignment of aluminum strips using a trapezoidal guide platform, utilizes protrusions 205 with V-grooves for non-destructive driving of the strip edges, and employs reciprocating illumination lamps 502 combined with image processing algorithms to eliminate specular reflection interference from highly reflective surfaces, ensuring the accuracy and reliability of defect detection. This invention not only identifies surface defects but also performs three-dimensional morphology analysis through multi-angle illumination features, meeting the high-standard inspection requirements for aluminum strip surface quality in industrial production.

[0031] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A device for detecting surface defects in aluminum plates and strips, characterized in that, include: Placement platform (1) is used to support the aluminum strip to be tested; The driving mechanism (2) is provided on the left and right sides of the placement platform (1) and is used to drive the aluminum strip to move along the traveling direction; The limiting mechanism (3) is provided with two sets and is respectively set on the entry end and exit end of the aluminum strip on the placement platform (1) to guide and press the aluminum strip; The image acquisition mechanism (4) is mounted directly above the two sets of limiting mechanisms (3) and is used to acquire image information of the surface of the aluminum strip. A light source emitting mechanism (5) is disposed on at least one side of the aluminum plate strip and is used to emit detection light onto the aluminum plate strip; The light source emitting mechanism (5) includes a lead screw transmission mechanism (501) and a lighting lamp (502) installed on the movable end of the lead screw transmission mechanism (501). The lead screw transmission mechanism (501) drives the lighting lamp (502) to reciprocate linearly along the traveling direction of the aluminum strip to provide the aluminum strip with multi-angle illumination light that varies along the traveling direction, so that the specular reflection characteristics of the aluminum strip surface are displaced as the position of the lighting lamp (502) changes.

2. The aluminum plate and strip surface defect detection device according to claim 1, characterized in that: The light source emitting mechanism (5) is provided in two sets, and the two sets of light source emitting mechanisms (5) are symmetrically arranged on both sides of the aluminum plate strip.

3. The aluminum plate and strip surface defect detection device according to claim 1, characterized in that: The upper surface of the placement platform (1) is provided with an upwardly raised guide platform, which includes a platform in the middle and slopes at both ends of the platform. The cross-section of the guide platform is trapezoidal.

4. The aluminum plate and strip surface defect detection device according to claim 1, characterized in that: The drive mechanism (2) includes a motor (201), a drive wheel (202), a driven wheel (203), a belt (204), and a plurality of protrusions (205); The motor (201) drives the drive wheel (202) to rotate, and the belt (204) is tensioned between the drive wheel (202) and the driven wheel (203); Multiple protrusions (205) are equidistantly distributed along the rotation direction of the belt (204). Each protrusion (205) has a V-shaped groove at one end away from the belt (204), which is used to engage with the edge of the aluminum strip.

5. The aluminum plate and strip surface defect detection device according to claim 1, characterized in that: The limiting mechanism (3) includes a lifting mechanism (301) and a roller (302) disposed on the movable end of the lifting mechanism (301). The lifting mechanism (301) is used to adjust the height of the roller (302) to adapt to aluminum strips of different thicknesses.

6. The aluminum plate and strip surface defect detection device according to claim 1, characterized in that: The image acquisition mechanism (4) includes an industrial camera (401), the shutter sampling frequency of which corresponds to the reciprocating motion state of the lighting lamp (502).

7. A method for detecting surface defects in aluminum strips based on the apparatus described in any one of claims 1-6, characterized in that, Includes the following steps: Step S1: Place the aluminum strip to be tested on the placement table (1), and use the V-groove of the protrusion (205) in the driving mechanism (2) to engage the edge of the aluminum strip, and use the limiting mechanism (3) to press and limit it. Step S2: The driving mechanism (2) moves the aluminum plate to the inspection station; Step S3: Start the light source emitting mechanism (5), use the lead screw transmission mechanism (501) to drive the lighting lamp (502) to move back and forth within a preset stroke, and at the same time use the image acquisition mechanism (4) to continuously acquire multiple frames of original images when the lighting lamp (502) is in different spatial coordinates; Step S4: Perform spatiotemporal difference fusion processing on the multiple original images and compare the displacement patterns of feature points in the images under different illumination angles; Step S5: Identify and remove specular reflection interference points that are displaced or disappear as the lighting lamp (502) moves, wherein the displacement direction of the specular reflection interference points is related to the movement direction of the lighting lamp (502); retain feature points with fixed physical positions as real surface defects, and output the detection results.

8. The method for detecting surface defects in aluminum strips according to claim 7, characterized in that: In step S4, the surface defect is reconstructed in three dimensions, either depth or height, by calculating the change in shadow length of the same feature point under different illumination angles.

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