A wheel hub bore polishing control method and system

Abstract

This invention discloses a method for controlling wheel hub hole grinding, comprising: receiving a wheel hub to be tested; obliquely illuminating the inner wall of the hub hole; detecting the characteristics of the reflected light spot, including the position, outline, and brightness of the spot; determining whether the wheel hub needs grinding based on the spot characteristics; if the determination result is that grinding is required, marking the wheel hub as a wheel hub to be ground and generating a grinding command; responding to the grinding command, calculating the defect parameters of the wheel hub to be ground; generating grinding compensation data based on the defect parameters; and performing a grinding operation on the wheel hub to be ground based on the grinding compensation data. This invention uses a relatively lower-cost solution, by obliquely illuminating the inner wall of the hub hole and then capturing the reflected light spot with a camera to obtain the parameters of the defects in the inner wall of the hub hole, achieving more comprehensive and accurate defect detection, thus making the calculation of compensation parameters for the grinding process more accurate.

Description

Technical Field

[0001] This invention relates to the field of wheel hub grinding technology, and in particular to a method and system for controlling wheel hub hole grinding. Background Technology

[0002] In modern wheelset pressing production lines, wheel hubs are typically stored in automated storage and retrieval systems (AS / RS). When a new order is triggered, the AS / RS uses a stacker crane to automatically transport the wheel hubs to the warehouse exit, and then a conveyor line transfers them to the pressing station; the warehousing process is completed via a reverse path.

[0003] However, wheel hubs stored for extended periods may develop rust or dust accumulation, and some finished products entering the warehouse may have residual burrs, streaks, or oil stains due to oversights in quality inspection. Although the geometric dimensions of these wheel hubs meet tolerance requirements, the micron-level assembly precision requirements will directly affect the coaxiality and dynamic balance performance of the wheelset assembly, thereby threatening the safety of train operation and passenger comfort.

[0004] Therefore, each wheel hub needs to be inspected before being transported to the press assembly line, and wheel hubs that fail the inspection need to undergo a precision grinding process.

[0005] During the inspection phase, the hub hole is typically imaged using a monocular fixed vision camera on the top of the machine cover. After locating the defect, three-dimensional data of the defect is generated, and then feed compensation and grinding head speed compensation are calculated.

[0006] During the polishing stage, existing methods typically involve a robotic arm moving along a preset spiral path, dynamically compensating for the feed rate and rotation speed based on detection data.

[0007] However, this solution has significant limitations. First, it has blind spots in the field of view. When vertical defects overlap, the camera's view will be blocked and the defects will be missed. Second, the vision system cannot distinguish such small defects (which may be difficult to see with the naked eye). The physical properties of rust, burrs, oil stains, and dust are different. Using a uniform compensation strategy can easily reduce polishing efficiency and affect production capacity. Third, most cameras on the market have insufficient resolution to identify small attachments, and using high-precision cameras is extremely expensive.

[0008] Therefore, this application proposes a wheel hub hole grinding control method and system with more accurate defect identification. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by proposing a wheel hub hole grinding control method and system. This method uses a relatively low-cost approach, which involves tilting and polishing the inner wall of the hub hole and then capturing the reflected light spot with a camera to obtain parameters of defects in the inner wall of the hub hole. This results in more comprehensive and accurate defect detection, and thus more accurate calculation of compensation parameters for the grinding process.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A method for controlling the grinding of wheel hub holes includes:

[0012] Receive the wheel hub to be tested;

[0013] The inner wall of the hub bore of the wheel hub to be tested is polished at an angle;

[0014] Detect the characteristics of the reflected light spot, including the position, outline, and brightness of the spot;

[0015] Determine whether the wheel hub under test needs to be polished based on the characteristics of the light spot.

[0016] If the determination result is that grinding is required, the wheel hub to be tested is marked as a wheel hub to be ground, and a grinding command is generated;

[0017] In response to a grinding command, the defect parameters of the wheel hub to be ground are calculated;

[0018] Grinding compensation data is generated based on the defect parameters;

[0019] The grinding operation is performed on the wheel hub to be ground based on the grinding compensation data.

[0020] The above method provides a relatively low-cost solution. By tilting and lighting the inner wall of the hub hole and then capturing the reflected light spot with a camera, the parameters of the defects in the inner wall of the hub hole can be obtained. This makes the defect detection more comprehensive and accurate, and thus the calculation of compensation parameters for the grinding process is more accurate.

[0021] Preferably, before obliquely polishing the inner wall of the hub bore of the wheel hub to be tested, the process further includes:

[0022] The upper and / or lower surfaces of the wheel hub under test are illuminated at an angle by a first light source.

[0023] The first reflected light spot of the first light source is received by a first light plate located on the same side or opposite side of the first light source;

[0024] Acquire an image of the first reflected light spot;

[0025] Retrieve the first standard light spot image and compare the actual light spot position and actual light spot shape of the first reflected light spot;

[0026] After successful comparison, the inner wall of the hub bore of the wheel hub to be tested is tilted and polished.

[0027] The above method allows for the detection of the placement of the wheel hub before detecting defects on the inner wall of the hub bore. The method of using tilted lighting and comparing the reflected light spot with the standard light spot to determine whether the wheel hub is level is also quite accurate. This avoids the problem that the wheel hub may have a slight tilt, which is so small that it is difficult to detect by conventional methods, but still has a significant impact on the accuracy of the subsequent defect detection process.

[0028] Preferred options also include:

[0029] If the comparison fails, it will be marked as an abnormal wheel hub;

[0030] The abnormal wheel hub is output to the abnormal workstation, and the abnormality count is accumulated;

[0031] When the proportion of the abnormal count to the total number of detections exceeds a set threshold, a workstation positioning abnormality alarm is triggered.

[0032] Using the above method, if a problem occurs at the detection station (such as the loading and unloading conveyor line or the lifting and positioning mechanism), an alarm can be triggered when the problem reaches a certain level, thus initiating the manual verification process and preventing the entire warehousing or output process from collapsing.

[0033] Preferably, the first light source includes at least three, the illumination angle of the first light source is 0-90°, and the illumination angle of each first light source is different. The first light source includes a narrow-band line light source and / or a point light source. The image of the first reflected light spot is acquired by taking a picture with a first camera located on the opposite side or the same side of the first light source.

[0034] The above method improves the accuracy of detecting whether the wheel hub under test is in a horizontal position, making it less likely to misjudge or miss the test.

[0035] Preferably, the tilted illumination of the inner wall of the hub hole is: the inner wall of the hub hole of the wheel hub to be tested is tilted and illuminated by a plurality of second light sources;

[0036] In this context, the second light source is a point light source;

[0037] The second light source is distributed in a ring along the center line of the hub hole;

[0038] At least one of the second light sources has a different emitted light height, an angle between the emitted light and the center line of the hub hole, and / or an emitted light radial angle than the other second light sources;

[0039] Each of the second light sources is illuminated instantaneously in sequence;

[0040] The second light source is positioned above the wheel hub to be tested via a lifting mechanism and / or a rotating mechanism.

[0041] The above method enables sampling inspection of the inner wall of the hub hole, balancing inspection efficiency and accuracy. It ensures the accuracy of grinding compensation parameters while avoiding dragging down the overall efficiency of warehousing or press-fitting production.

[0042] Preferably, the emitted light rays from each of the second light sources pass through the center line of the hub hole.

[0043] By using the above method, it is ensured that each illumination of each second light source is directed at only one detection area, thus avoiding errors in the calculation of compensation parameters caused by interference from additional defects.

[0044] Preferably, the spot characteristics of the detected reflected light include:

[0045] The second reflected light spot is received by a second light plate located below the wheel hub under the test;

[0046] The second spot image of each second reflected light spot is acquired by the second camera located on the same side as the second light source;

[0047] The second spot image is subjected to flat field correction and non-local mean filtering in sequence;

[0048] Extract all spot regions from the second spot image;

[0049] The actual center position of each light spot region is determined by a Gaussian fitting algorithm and is taken as the actual light spot position.

[0050] An ellipse fitting algorithm is used to extract the contour parameters of each light spot region as the actual light spot shape.

[0051] Calculate the average grayscale value of each of the light spot regions as the actual brightness value.

[0052] Preferably, extracting all spot regions in the second spot image includes:

[0053] Binarization of the filtered second spot image:

[0054] The binary image B(x,y) is obtained;

[0055] Traverse the binary image B(x,y), and perform 8-neighborhood connectivity labeling on pixels with a value of 1, with each connected region being a spot region;

[0056] Output the set R of all the light spot regions. k (k = 1, 2, ..., K), where each of the light spot regions contains a set of pixel coordinates;

[0057] Among them: I 滤波后(x, y) represents the pixel gray value at coordinates (x, y) in the image after nonlocal mean filtering; T is the segmentation threshold, which represents the adaptive threshold based on the image histogram or the set threshold; B(x, y) represents the value at coordinates (x, y) in the binary image (1 represents the spot area, 0 represents the background).

[0058] Preferably, calculating the average gray level of each of the light spot regions includes:

[0059]

[0060] Where, μ 灰度 N represents the average grayscale value of the light spot area, i.e., the actual brightness value; R represents the light spot area. k The total number of pixels in; I 滤波后 (x, y) represents the pixel gray value at coordinates (x, y) in the image after nonlocal mean filtering.

[0061] Preferably, determining whether the wheel hub to be tested needs polishing based on the light spot characteristics includes:

[0062] Retrieve a second standard spot image from the standard library at the same incident angle as the second light source, including the standard center position, standard spot shape, and standard brightness value;

[0063] Compare the actual spot position with the standard center position, the actual spot shape with the standard spot shape, and the actual brightness value with the standard brightness value;

[0064] If the comparison result does not exceed the set threshold, it is determined that the wheel hub under test does not need to be polished; if the comparison result exceeds the set threshold, it is determined that the wheel hub under test needs to be polished, the wheel hub under test is marked as a wheel hub that needs to be polished, and a polishing command is triggered.

[0065] Preferably, the calculation of the defect parameters of the wheel hub to be polished includes:

[0066] Calculate the deviation distance between each actual center position and the standard center position;

[0067] Calculate the contour deformation of each actual spot shape compared to the standard spot shape;

[0068] The defect type is determined by matching the actual brightness value against a defect type threshold library.

[0069] The three-dimensional coordinates of the defect and the required grinding thickness of the defect are mapped based on the deviation distance and the contour deformation amount.

[0070] Preferably, the defect type τ includes burrs, rust, oil stains, and protrusions, and the three-dimensional coordinates D of the defect are... i Including the horizontal coordinate value x dVertical coordinate value y d and axial depth value z d .

[0071] Preferably, the calculation of the deviation distance includes:

[0072]

[0073] Among them, D 偏差 Indicates the deviation distance; x 实际 y 实际 This represents the actual center coordinates of the light spot output by the Gaussian fitting; x 标准 y 标准 This represents the center coordinates of the standard spot corresponding to the incident angle of the light source in the standard library.

[0074] Preferably, the calculation of the contour deformation includes:

[0075] S 变形 =α|a 实际 -a 标准 |+β|b 实际 -b 标准 |+γ|θ 实际 -θ 标准 |;

[0076] Among them, S 变形 Indicates the amount of contour deformation; a 实际 b 实际 θ 实际 These represent the actual major axis, minor axis, and rotation angle of the ellipse fitting output, respectively, i.e., the actual contour parameters; a 标准 b 标准 θ 标准 Then, it represents the standard profile parameter corresponding to the incident angle of the light source in the standard library; α, β, and γ represent the weighting coefficients based on the geometric characteristics of the wheel hub to be polished (usually α = 0.4, β = 0.4, and γ = 0.2).

[0077] Preferably, the three-dimensional coordinates of the mapped defect include:

[0078] Let the 3D position of the i-th second light source be (X). Si Y Si Z Si The actual position of the second reflected light spot on the second light plate is (x) i y i The equation of the second smooth plate is Z = Z 光板 The total number of second light sources is M; the three-dimensional coordinates of the defect point (X... d Y d Z d The formula for calculating ) is:

[0079]

[0080] in, This indicates an iterative solution, with the average value used as the initial value.

[0081] Preferably, the thickness T to be polished for the mapped defect is... 打磨 include:

[0082] T 打磨 =λS 变形 +ηD 偏差 ;

[0083] Among them, S 变形 D represents the amount of contour deformation. 偏差 The deviation distance is represented by λ and η, which represent the proportionality coefficients obtained based on experimental data of the wheel hub material (typically λ = 0.6 and η = 0.4).

[0084] Preferably, generating grinding compensation data based on the defect parameters of the wheel hub under test includes:

[0085] Match the defect type influence function according to the defect type;

[0086] Input the three-dimensional coordinates and the thickness to be ground into the function to generate feed rate compensation, rotation speed compensation and radial pressure compensation.

[0087] Preferably, the defect type influence function is:

[0088] C 进给 =α i *T 打磨 +β i *Z d ;

[0089]

[0090] C 径向压力 =α i *T 打磨 +β i *Z d ;

[0091] Where, α i With β i Each represents a type of defect, and is expressed as a different coefficient for the same defect type; please refer to the type coefficient table; X d Y d Z d These represent the three-dimensional coordinates of the defect point.

[0092] Using the above method, the brightness of the second reflected spot is calculated to infer the type of defect, and the deviation distance and contour deformation relative to the standard reflected spot are calculated to determine the actual three-dimensional coordinates of the defect and the thickness to be polished. Finally, the compensation parameters required for polishing the defect area are calculated, so that the final polishing process is both efficient and accurate, ensuring the precision assembly of the pressing process and guaranteeing the production efficiency of the pressing process.

[0093] To achieve the above objectives, the present invention also provides the following technical solution:

[0094] A wheel hub hole grinding control system, comprising:

[0095] The loading and unloading conveyor line includes a roller conveyor line. The bottom of the loading and unloading conveyor line is equipped with a lifting and positioning mechanism, and the loading and unloading conveyor line at the lifting and positioning mechanism is designed with a hollow structure.

[0096] The enclosed machine cover has an inlet and an outlet at both ends of the loading and unloading conveyor line, and a flexible light-blocking curtain is provided at both the inlet and the outlet. The top of the enclosed machine cover is provided with a second camera and a second light source for tilting and lighting the inner wall of the hub hole. When the hub to be inspected is positioned by the lifting and positioning mechanism, the shooting direction of the second camera is aligned with the center line of the hub hole of the hub to be inspected.

[0097] The second light plate is located below the cutout position of the loading and unloading conveyor line and faces the second camera.

[0098] An image processing unit, wherein the input terminal of the image processing unit is electrically connected to the output terminal of the second camera;

[0099] The control unit has its input terminal electrically connected to the output terminal of the image processing unit, and its output terminal electrically connected to the input terminals of the loading and unloading conveying unit, the lifting and positioning mechanism, the second light source, and the camera.

[0100] A storage unit is used to store a second standard light spot image when a defect-free wheel hub is polished. The storage unit is electrically connected to the image processing unit and the control unit, respectively.

[0101] The control unit is configured to execute the wheel hub hole grinding control method described above.

[0102] Compared with the prior art, the beneficial effects of this invention are as follows: by using a relatively low-cost solution, the parameters of the defects in the inner wall of the hub hole are obtained by tilting and lighting the inner wall of the hub hole and then capturing the reflected light spot with a camera, thus achieving more comprehensive and accurate defect detection. Therefore, the calculation of compensation parameters for the grinding process is more accurate. Attached Figure Description

[0103] Figure 1 This is a flowchart of a wheel hub hole grinding control method proposed in this invention;

[0104] Figure 2 A three-dimensional structural diagram of an existing wheel hub hole grinding control system;

[0105] Figure 3 A front view of the existing wheel hub hole grinding control system;

[0106] Figure 4 This is a schematic diagram of the polishing system in a wheel hub hole grinding control system proposed in this invention;

[0107] Figure 5 This is a schematic diagram of another lighting method in a wheel hub hole grinding control system proposed in this invention;

[0108] Figure 6 This is a schematic diagram of the wheel hub hole grinding control system proposed in this invention.

[0109] In the diagram: 1. Loading and unloading conveyor line; 2. Lifting and positioning mechanism; 3. Enclosed machine cover; 4. Second light plate; 5. Second camera; 6. Image processing unit; 7. Control unit; 8. Storage unit; 9. First camera; 10. First light plate; 11. Lifting mechanism; 12. Rotating mechanism; 13. First light source; 14. Second light source. Detailed Implementation

[0110] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0111] Before being stored or shipped, existing wheel hubs may have defects that are difficult to observe with the naked eye due to different storage times and sources. These defects may include dust, oil stains, rust, streaks, and burrs (which have fallen off but are still attached to the hub). For defects located in the hub bore, this generally leads to insufficient assembly precision in subsequent assembly, making it difficult to meet the micron-level press-fit requirements.

[0112] Existing methods for handling defects in hub bores primarily involve using a fixed monocular vision camera aligned with the hub bore's centerline to photograph the bore. After image processing, parameters for each defect are calculated. These defects are then removed through continuous spiral grinding (the inspection and grinding stations are the same). The grinding path is generated based on the hub dimensions, and these defect parameters provide compensation during the grinding stage, such as compensation for rotational speed, feed rate, and radial pressure, as illustrated by the RMI intelligent machining method disclosed in Chinese Invention Patent Application No. 202411850845X.

[0113] However, in the defect detection stage, the micron-level precision requirement necessitates a very high-resolution camera, which is extremely costly. Moreover, there is still the issue of field of view obstruction: defects located below may be obscured by defects above, making the calculation of compensation parameters inaccurate. Furthermore, since these defects are very small, usually a very thin layer, it is easy to misjudge conditions such as dust and oil stains, but the compensation parameters required for them are also different.

[0114] It should be understood that this technical solution aims to address the problems of insufficient accuracy and high cost in existing hub hole detection methods, and can achieve the functions of defect type judgment and accurate identification of defect parameters at a slightly lower cost. The image processing algorithm involved should be considered as existing publicly available technology that has already been applied to surface defect detection.

[0115] Example 1:

[0116] Please see Figure 1-6 The present invention provides the following technical solution: a method for controlling the grinding of wheel hub holes, comprising:

[0117] Receive the wheel hub to be tested;

[0118] The inner wall of the hub bore of the wheel hub to be tested is polished at an angle;

[0119] Detect the characteristics of the reflected light spot, including the position, outline, and brightness of the spot;

[0120] Determine whether the wheel hub under test needs to be polished based on the characteristics of the light spot.

[0121] If the determination result is that grinding is required, the wheel hub to be tested is marked as a wheel hub to be ground, and a grinding command is generated;

[0122] In response to a grinding command, the defect parameters of the wheel hub to be ground are calculated;

[0123] Grinding compensation data is generated based on the defect parameters;

[0124] The grinding operation is performed on the wheel hub to be ground based on the grinding compensation data.

[0125] As an optional implementation of this invention, after the wheel hub to be tested is loaded into place, when the inner wall of the hub hole is illuminated at an angle, if there is a defect on the surface of the inner wall of the hub hole, then the reflected light with defects will show a different reflection angle compared with the reflected light without defects. The light spot formed on the light plate will also be different. At this time, the image of the light spot is captured by the camera and compared with the reflected light spot at the same detection position, the same incident angle, and the same power, so that the defect situation at the detection position can be determined. Compared with directly capturing the image of the defect with the camera, since the light is reflected differently on different defects, even if the defect is slightly raised, the angle of the reflected light may not deviate much, but the distance between the light spot formed on the light plate at a certain distance and the distance formed on the light plate under the condition of no defects is very obvious (principle: the height of the light plate and the detection position is a constant h, the angle of the reflected light is θ, and the minimum distance from the light spot to the inner wall of the hub hole is d, then d=h*tanα. Therefore, according to the first quadrant, △d tends to increase exponentially with the change of △θ, and it is more obvious when the incident light angle is close to perpendicular to the inner wall of the hub hole).

[0126] Therefore, compared to directly capturing images of defects on the inner surface of the hub bore using a camera, the method of obliquely illuminating the inner wall of the hub bore and then photographing the reflected light spots for defect detection amplifies the appearance of defects. The defect parameters reflected in the photographed reflected light spots are also magnified, leading to more accurate acquisition of the defect parameters. Furthermore, this oblique lighting method allows for a reduction in the precision requirements of the camera, thus lowering hardware costs. Moreover, compared to the existing method of directly photographing the hub bore from above using a camera aligned with the center line, the oblique lighting method also directly illuminates defects below the hub bore, solving the problem of field-of-view obstruction and resulting in more accurate and comprehensive defect detection.

[0127] The lighting parameters, such as the number of light sources, the type of light sources, and the lighting angle, are not specifically limited. Any method that amplifies the appearance of defects by using oblique lighting should be considered within the scope of protection of this oblique lighting.

[0128] The above method provides a relatively low-cost solution. By tilting and lighting the inner wall of the hub hole and then capturing the reflected light spot with a camera, the parameters of the defects in the inner wall of the hub hole can be obtained. This makes the defect detection more comprehensive and accurate, and thus the calculation of compensation parameters for the grinding process is more accurate.

[0129] Furthermore, the tilted illumination of the inner wall of the hub hole is: the inner wall of the hub hole of the wheel hub to be tested is tilted and illuminated by a number of second light sources 14.

[0130] Among them, the second light source 14 are all point light sources;

[0131] The second light source 14 is distributed in a ring along the center line of the hub hole;

[0132] At least one of the second light sources 14 has a different emitted light height, an angle between the emitted light and the center line of the hub hole, and / or an emitted light radial angle than the other second light sources 14.

[0133] Each of the second light sources 14 is lit up instantaneously in sequence;

[0134] The second light source 14 is positioned above the wheel hub to be tested via a lifting mechanism 11 and / or a rotating mechanism 12.

[0135] As an optional implementation of the present invention, since the types and locations of defects on the inner wall of the hub bore to be tested are random, if the entire inner wall needs to be scanned completely, the detection time will be too long, which will easily cause backlog on the loading and unloading conveyor line 1, thus dragging down the efficiency of the pressing production line or warehousing.

[0136] To address this, this solution employs a ring-shaped distribution of point light sources to provide differentiated tilted illumination to the inner wall of the hub hole: at the zero-point station, each point light source sequentially illuminates a region at the same depth but different angles or a region at the same angle but different depths, with each illumination triggering a single photograph; after all point light sources have been illuminated, the entire system is moved by the lifting mechanism 11 or the rotating mechanism 12 to the next target illumination area to repeat the process.

[0137] The lifting mechanism 11 or the rotating mechanism 12 is preferably a servo or stepper driven power component, such as a servo cylinder or a servo motor, which has high precision and thus reduces the interference of the structure itself on the detection accuracy. As for the distribution of the point light source, it can be directly installed aligned with the center line of the hub hole (the emission point is not required to be aligned with the center line), or it can be installed aligned with the edge of the hub hole or even outside the edge of the hub hole, as long as the reflected light after tilting the light can be captured by the camera.

[0138] In this process, the division of the target illumination area can be defined by the number, distribution position, and angle of the lifting mechanism, rotating mechanism, and the second light source itself. That is, when the rotating mechanism and lifting mechanism are in a non-moving state (assuming that the system contains both rotating and lifting mechanisms), the area illuminated by all the second light sources in this state is the i-th target illumination area. The point illuminated by each second light source in this target illumination area is a part of the hub hole surface (that is, each second light source illuminating a point in a certain area of ​​the hub hole surface means that the area has been illuminated). Adjacent parts of the area correspond to adjacent second light sources, and adjacent parts of the area are connected. The area illuminated by all the second light sources forms the i-th target illumination area. When the lifting mechanism or rotating mechanism moves to the next position, the i+1 target illumination areas are illuminated instantaneously in sequence.

[0139] A sampling inspection method is developed to sample and inspect key areas of the inner wall of the hub bore, achieving a balance between efficiency and accuracy. Given that typical defects such as oil stains, dust, and rust are usually millimeter-sized, any abnormality found in any inspection area indicates that the entire hub needs to be polished. Defect parameter calculations are categorized by the divided inspection areas (i.e., all areas involved in polishing), requiring only compensation for the polishing parameters of that area, without needing to pinpoint the microscopic three-dimensional parameters of each defect. After all, while these types of defects affect assembly accuracy, they are relatively easy to polish, offering a high degree of tolerance for error.

[0140] The above method enables sampling inspection of the inner wall of the hub hole, balancing inspection efficiency and accuracy. It ensures the accuracy of grinding compensation parameters while avoiding dragging down the overall efficiency of warehousing or press-fitting production.

[0141] Furthermore, the emitted light rays from each of the second light sources 14 all pass through the center line of the hub hole.

[0142] As an optional implementation of the present invention, if the point light source is not aligned with the center line of the hub hole and shines light onto the inner wall of the hub hole, then even if the hub under test itself is defect-free, the reflected light may first pass through other positions on the inner wall of the hub hole. In this way, the reflected light may pass through additional defects, thereby interfering with the detection effect.

[0143] By using the above method, it is ensured that each illumination of each second light source 14 is directed only to one detection area, thus avoiding errors in the calculation of compensation parameters caused by interference from additional defects.

[0144] Furthermore, the spot characteristics of the detected reflected light include:

[0145] The second reflected light spot is received by the second light plate 4 located below the wheel hub to be tested;

[0146] The second light spot image of each second reflected light spot is acquired by the second camera 5 located on the same side as the second light source 14;

[0147] The second spot image is subjected to flat field correction and non-local mean filtering in sequence;

[0148] Extract all spot regions from the second spot image;

[0149] The actual center position of each light spot region is determined by a Gaussian fitting algorithm and is taken as the actual light spot position.

[0150] An ellipse fitting algorithm is used to extract the contour parameters of each light spot region as the actual light spot shape.

[0151] Calculate the average grayscale value of each of the light spot regions as the actual brightness value.

[0152] As an optional implementation of the present invention, although the test hub involved in this technical solution is generally a relatively large train hub with a large hub hole size, it can also be applied to hubs with a smaller hub hole size. Furthermore, the inspection station, grinding station and loading / unloading conveyor line 1 are integrated within the enclosed machine cover 3. Therefore, in order to enable the camera to have a sufficient field of view to capture the second light spot image, the second light source 14 and the camera can only be set in the upper space of the machine cover, and the second light plate 4 can only be arranged in the space below the loading / unloading conveyor line 1.

[0153] The second polished plate 4 can be a flat plate or a concave shape; this technical solution does not specifically limit it. Of course, since the polishing process involves the removal of impurities, a flat plate is preferred. Furthermore, an automatic shielding structure can be designed for the second polished plate 4, such as a translation mechanism to move the second polished plate 4 out of the hub hole, or a telescopic plate to extend during the polishing process to prevent impurities from adhering to the second polished plate 4.

[0154] The flat field correction and nonlocal mean filtering processes are well-known techniques that have been widely applied in existing technologies. As functions used in this technical solution to correct image uniformity and denoise the image, they are direct applications of existing algorithms without any improvement. Therefore, they will not be elaborated on here.

[0155] The Gaussian fitting algorithm for extracting the actual center position of the spot region, the ellipse fitting algorithm for extracting the contour parameters of each spot region, and the calculation of the average gray value of the region are all common algorithms in existing image processing. This technical solution does not involve any improvement to these algorithms. Those skilled in the art can directly refer to the existing applications of these algorithms, and will not elaborate further here.

[0156] Using the above method, light is projected downwards from above the wheel hub, and the reflected light is received by the second light plate 4 to form a second reflected light spot on the second light plate 4. This facilitates the second camera 5 to take pictures, and further facilitates the output of various parameters of the second reflected light spot as a basis for comparison with the second standard light spot image.

[0157] Furthermore, the extraction of all spot regions in the second spot image includes:

[0158] Binarization of the filtered second spot image:

[0159] The binary image B(x,y) is obtained;

[0160] Traverse the binary image B(x,y), and perform 8-neighborhood connectivity labeling on pixels with a value of 1, with each connected region being a spot region;

[0161] Output the set R of all the light spot regions. k (k = 1, 2, ..., K), where each of the light spot regions contains a set of pixel coordinates;

[0162] Among them: I 滤波后 (x, y) represents the pixel gray value at coordinates (x, y) in the image after nonlocal mean filtering; T is the segmentation threshold, which represents the adaptive threshold based on the image histogram or the set threshold; B(x, y) represents the value at coordinates (x, y) in the binary image (1 represents the spot area, 0 represents the background).

[0163] As an optional implementation of the present invention, the method for extracting the spot region is further defined, that is, the spot region in each second spot image is extracted by binarization and neighborhood connectivity, so as to provide a basis for subsequent judgment of the actual position, contour deformation amount and defect type of the spot.

[0164] Furthermore, calculating the average grayscale value of each of the light spot regions includes:

[0165]

[0166] Where, μ 灰度 N represents the average grayscale value of the light spot area, i.e., the actual brightness value; R represents the light spot area. k The total number of pixels in; I 滤波后 (x, y) represents the pixel gray value at coordinates (x, y) in the image after nonlocal mean filtering.

[0167] Furthermore, determining whether the wheel hub needs polishing based on the light spot characteristics includes:

[0168] Retrieve a second standard spot image from the standard library at the same incident angle as the second light source 14, including the standard center position, standard spot shape, and standard brightness value;

[0169] Compare the actual spot position with the standard center position, the actual spot shape with the standard spot shape, and the actual brightness value with the standard brightness value;

[0170] If the comparison result does not exceed the set threshold, it is determined that the wheel hub under test does not need to be polished; if the comparison result exceeds the set threshold, it is determined that the wheel hub under test needs to be polished, the wheel hub under test is marked as a wheel hub that needs to be polished, and a polishing command is triggered.

[0171] As an optional implementation of this invention, to ensure the accuracy of the light spot calculation, the light spot formed on the second light plate 4 by light with the same parameters as the second light source 14 is required as a comparison basis to ensure accurate calculation results. It is worth noting that if any comparison result exceeds a set threshold, the wheel hub is directly output as needing polishing. The comparison of each light spot area ensures that when multiple defects occur, polishing compensation can be applied to each defective area. The specific set threshold varies depending on the lighting and imaging architecture, mainly based on how small the defect is to warrant not polishing. However, this parameter also varies depending on the wheel hub; the assembly requirements for each wheel hub can be referenced, generally at the micrometer level.

[0172] Furthermore, the calculation of the defect parameters of the wheel hub to be polished includes:

[0173] Calculate the deviation distance between each actual center position and the standard center position;

[0174] Calculate the contour deformation of each actual spot shape compared to the standard spot shape;

[0175] The defect type is determined by matching the actual brightness value against a defect type threshold library.

[0176] The three-dimensional coordinates of the defect and the required grinding thickness of the defect are mapped based on the deviation distance and the contour deformation amount.

[0177] Furthermore, the defect type τ includes burrs, rust, oil stains, and protrusions, and the three-dimensional coordinates D of the defect are... i Including the horizontal coordinate value x d Vertical coordinate value y d and axial depth value z d .

[0178] Furthermore, the calculation of the deviation distance includes:

[0179]

[0180] Among them, D 偏差 Indicates the deviation distance; x 实际 y 实际 This represents the actual center coordinates of the light spot output by the Gaussian fitting; x 标准 y 标准 This represents the center coordinates of the standard spot corresponding to the incident angle of the light source in the standard library.

[0181] Furthermore, the calculation of the contour deformation includes:

[0182] S 变形 =α|a 实际 -a 标准 |+β|b实际 -b 标准 |+γ|θ 实际 -θ 标准 |;

[0183] Among them, S 变形 Indicates the amount of contour deformation; a 实际 b 实际 θ 实际 These represent the actual major axis, minor axis, and rotation angle of the ellipse fitting output, respectively, i.e., the actual contour parameters; a 标准 b 标准 θ 标准 Then, it represents the standard profile parameter corresponding to the incident angle of the light source in the standard library; α, β, and γ represent the weighting coefficients based on the geometric characteristics of the wheel hub to be polished (usually α = 0.4, β = 0.4, and γ = 0.2).

[0184] Furthermore, the three-dimensional coordinates of the mapping defect include:

[0185] Let the 3D position of the i-th second light source 14 be (X Si Y Si Z Si The actual position of the second reflected light spot on the second light plate 4 is (x i y i The equation of the second light plate 4 plane is Z = Z 光板 The total number of second light sources 14 is M; the three-dimensional coordinates of the defect point (X d Y d Z d The formula for calculating ) is:

[0186]

[0187] in, This indicates an iterative solution, with the average value used as the initial value.

[0188] Furthermore, the required grinding thickness T of the mapped defect 打磨 include:

[0189] T 打磨 =λS 变形 +ηD 偏差 ;

[0190] Among them, S 变形 D represents the amount of contour deformation. 偏差 The deviation distance is represented by λ and η, which represent the proportionality coefficients obtained based on experimental data of the wheel hub material (typically λ = 0.6 and η = 0.4).

[0191] Furthermore, generating grinding compensation data based on the defect parameters of the wheel hub under test includes:

[0192] Match the defect type influence function according to the defect type;

[0193] Input the three-dimensional coordinates and the thickness to be ground into the function to generate feed rate compensation, rotation speed compensation and radial pressure compensation.

[0194] Furthermore, the defect type influence function is:

[0195] C 进给 =α i *T 打磨 +β i *Z d ;

[0196]

[0197] C 径向压力 =α i *T 打磨 +β i *Z d ;

[0198] Where, α i With β i Each represents a type of defect, and is expressed as a different coefficient for the same defect type; please refer to the type coefficient table; X d Y d Z d These represent the three-dimensional coordinates of the defect point.

[0199] As an optional implementation of this invention, the specific calculation process of the defect parameters of the wheel hub to be ground is defined to provide a basis for mapping the compensation parameters. The defect type threshold library, also known as the type coefficient table, indicates that different defect types are suitable for different influence coefficients, as shown in the table below:

[0200] Table 1: Category Coefficient Table

[0201]

[0202]

[0203] Using the above method, the brightness of the second reflected spot is calculated to infer the type of defect, and the deviation distance and contour deformation relative to the standard reflected spot are calculated to determine the actual three-dimensional coordinates of the defect and the thickness to be polished. Finally, the compensation parameters required for polishing the defect area are calculated, so that the final polishing process is both efficient and accurate, ensuring the precision assembly of the pressing process and guaranteeing the production efficiency of the pressing process.

[0204] Example 2:

[0205] In Example 1, various inspection and polishing processes are completed by tilting and polishing the hub hole. However, in actual operation, there are other problems that interfere with the accuracy of the inspection. In particular, when the hub itself is not accurately positioned, it is unreliable to rely on real-time comparison of the reflected light spot of the defect with the standard light spot. Therefore, it is also necessary to verify the positioning of the hub to be tested after loading.

[0206] This embodiment is based on Embodiment 1, and further details can be found in the following references. Figure 4-5 Before obliquely polishing the inner wall of the hub bore of the wheel hub to be tested, the process also includes:

[0207] The upper and / or lower surfaces of the wheel hub under test are illuminated at an angle by the first light source 13.

[0208] The first reflected light spot of the first light source 13 is received by the first light plate 10 located on the same side or opposite side of the first light source 13;

[0209] Acquire an image of the first reflected light spot;

[0210] Retrieve the first standard light spot image and compare the actual light spot position and actual light spot shape of the first reflected light spot;

[0211] After successful comparison, the inner wall of the hub bore of the wheel hub to be tested is tilted and polished.

[0212] As an optional implementation of the present invention, since the upper or lower surface of the wheel hub is flat, or at least has a flat surface, the flatness of the wheel hub under test can be reflected by tilting the light and comparing the reflected light spot with the standard light spot, thereby reflecting whether the wheel hub under test is placed horizontally, thus avoiding affecting the accuracy of subsequent detection of hub hole defects.

[0213] The above method allows for the detection of the placement of the wheel hub before detecting defects on the inner wall of the hub bore. The method of using tilted lighting and comparing the reflected light spot with the standard light spot to determine whether the wheel hub is level is also quite accurate. This avoids the problem that the wheel hub may have a slight tilt, which is so small that it is difficult to detect by conventional methods, but still has a significant impact on the accuracy of the subsequent defect detection process.

[0214] Furthermore, it also includes:

[0215] If the comparison fails, it will be marked as an abnormal wheel hub;

[0216] The abnormal wheel hub is output to the abnormal workstation, and the abnormality count is accumulated;

[0217] When the proportion of the abnormal count to the total number of detections exceeds a set threshold, a workstation positioning abnormality alarm is triggered.

[0218] As an optional implementation of the present invention, in some cases, multiple wheel hubs to be tested cannot be placed horizontally, which is likely due to a problem with the testing station (including the loading and unloading conveyor line 1 and the lifting and positioning mechanism 2). When such problems occur to a certain extent, a manual verification process needs to be initiated to avoid the collapse of the entire warehousing or output process.

[0219] The aforementioned method for detecting whether the wheel hub under test is placed horizontally can easily lead to exceptions if the number of first light sources 13 is small. For example, a reflected light spot may not deviate from the standard light spot, but this could be due to rust, dust, oil, or other contaminants at that location. Alternatively, most reflected light spots may conform to the standard light spot, but one spot may not, and the reason for this discrepancy could be a surface defect, even though the wheel hub under test is actually placed horizontally. This can result in misjudgment. Therefore, it is necessary to design more first light sources 13, which can be used in conjunction with point light sources and narrow-band line light sources, and then determine whether the wheel hub under test is horizontal using threshold matching.

[0220] Therefore, the first light source 13 further includes at least three, the lighting angle of the first light source 13 is 0-90°, and the lighting angle of each first light source is different. The first light source 13 includes narrow-band line light source and / or point light source. The image of the first reflected light spot is acquired by taking a picture by the first camera 9 located on the opposite side or the same side of the first light source 13.

[0221] As an optional implementation of this invention, the aforementioned tilting method for illuminating the hub hole is also applicable in this technical solution, but since the surface of the wheel hub is being inspected, the inspection angle can be expanded to a range of 45-90°. Furthermore, using a narrow-band line light source provides better reflection of the upper surface of the wheel hub, making it easier to determine whether it differs from a standard light spot.

[0222] The above method improves the accuracy of detecting whether the wheel hub under test is in a horizontal position, making it less likely to misjudge or miss the test.

[0223] Example 3:

[0224] To achieve the above objectives, the present invention also provides the following technical solution:

[0225] Please see Figure 2-6 A wheel hub hole grinding control system, comprising:

[0226] The loading and unloading conveyor line 1 includes a roller conveyor line. The bottom of the loading and unloading conveyor line 1 is provided with a lifting and positioning mechanism 2, and the loading and unloading conveyor line 1 at the lifting and positioning mechanism 2 is designed with a hollow structure.

[0227] The enclosed machine cover 3 is located at both ends of the loading and unloading conveyor line 1 and has an inlet and an outlet, and both the inlet and the outlet are equipped with flexible light-blocking curtains; the top of the enclosed machine cover 3 is equipped with a second camera 5 and a second light source 14 for tilting and lighting the inner wall of the hub hole. When the hub to be inspected is positioned by the lifting and positioning mechanism 2, the shooting direction of the second camera 5 is aligned with the center line of the hub hole of the hub to be inspected.

[0228] The second light plate 4 is located below the cutout position of the loading and unloading conveyor line 1 and faces the second camera 5.

[0229] Image processing unit 6, the input end of which is electrically connected to the output end of the second camera 5;

[0230] Control unit 7, the input terminal of which is electrically connected to the output terminal of image processing unit 6, and the output terminal of control unit 7 is electrically connected to the input terminal of loading and unloading conveying unit, lifting and positioning mechanism 2, second light source 14, and camera;

[0231] Storage unit 8 is used to store the second standard light spot image when the defect-free wheel hub is polished. The storage unit 8 is electrically connected to the image processing unit 6 and the control unit 7 respectively.

[0232] The control unit 7 is configured to execute the wheel hub hole grinding control method described above.

[0233] As an optional implementation of the present invention, the wheel hub to be tested enters the enclosed machine cover 3 through the loading and unloading conveyor line 1. After it is in place, the lifting and positioning mechanism 2 rises to position the wheel hub to be tested, and then the defect detection of the hub hole can be performed as described above.

[0234] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the grinding of wheel hub holes, characterized in that, include: Receive the wheel hub to be tested; The inner wall of the hub bore of the wheel hub to be tested is polished at an angle; Detect the characteristics of the reflected light spot, including the position, outline, and brightness of the spot; Determine whether the wheel hub under test needs to be polished based on the characteristics of the light spot. If the determination result is that grinding is required, the wheel hub to be tested is marked as a wheel hub to be ground, and a grinding command is generated; In response to a grinding command, the defect parameters of the wheel hub to be ground are calculated; Grinding compensation data is generated based on the defect parameters; The grinding operation is performed on the wheel hub to be ground according to the grinding compensation data; The polishing compensation data includes: Match the defect type influence function according to the defect type; Input the three-dimensional coordinates and the thickness to be ground into the function to generate feed rate compensation, rotation speed compensation and radial pressure compensation; The defect type influence function is: C 进给 =a i *T 打磨 +b i *Z d ; ； C 径向压力 =a i *T 打磨 +b i *Z d ; Where, α i With β i Each represents a type of defect, and is represented by different coefficients for the same defect type. Please refer to the type coefficient table. X d , Y d , Z d These represent the three-dimensional coordinates of the defect point.

2. The wheel hub hole grinding control method according to claim 1, characterized in that, Before obliquely polishing the inner wall of the hub bore of the wheel hub to be tested, the process also includes: The upper and / or lower surfaces of the wheel hub under test are illuminated at an angle by a first light source. The first reflected light spot of the first light source is received by a first light plate located on the same side or opposite side of the first light source; Acquire an image of the first reflected light spot; Retrieve the first standard light spot image and compare the actual light spot position and actual light spot shape of the first reflected light spot; After successful comparison, the inner wall of the hub bore of the wheel hub to be tested is tilted and polished.

3. The wheel hub hole grinding control method according to claim 2, characterized in that, Also includes: If the comparison fails, it will be marked as an abnormal wheel hub; The abnormal wheel hub is output to the abnormal workstation, and the abnormality count is accumulated; When the proportion of the abnormal count to the total number of detections exceeds a set threshold, a workstation positioning abnormality alarm is triggered.

4. The wheel hub hole grinding control method according to claim 2, characterized in that, The first light source includes at least three, the illumination angle of the first light source is 0-90°, and the illumination angle of each first light source is different. The first light source includes narrow-band line light source and / or point light source. The image of the first reflected light spot is acquired by taking a picture with a first camera located on the opposite side or the same side of the first light source.

5. The wheel hub hole grinding control method according to claim 2, characterized in that, The method of obliquely illuminating the inner wall of the hub hole of the wheel hub to be tested is: obliquely illuminating the inner wall of the hub hole of the wheel hub to be tested through several second light sources. In this context, the second light source is a point light source; The second light source is distributed in a ring along the center line of the hub hole; At least one of the second light sources has a different emitted light height, an angle between the emitted light and the center line of the hub hole, and / or an emitted light radial angle than the other second light sources; Each of the second light sources is illuminated instantaneously in sequence; The second light source is positioned above the wheel hub to be tested via a lifting mechanism and / or a rotating mechanism.

6. The wheel hub hole grinding control method according to claim 5, characterized in that, The light spot characteristics of the detected reflected light include: The second reflected light spot is received by a second light plate located below the wheel hub under the test; The second spot image of each second reflected light spot is acquired by the second camera located on the same side as the second light source; The second spot image is subjected to flat field correction and non-local mean filtering in sequence; Extract all spot regions from the second spot image; The actual center position of each light spot region is determined by a Gaussian fitting algorithm and is taken as the actual light spot position. An ellipse fitting algorithm is used to extract the contour parameters of each light spot region as the actual light spot shape. Calculate the average grayscale value of each of the light spot regions as the actual brightness value.

7. The wheel hub hole grinding control method according to claim 6, characterized in that, The step of determining whether the wheel hub under test needs to be polished based on the light spot characteristics includes: Retrieve a second standard spot image from the standard library at the same incident angle as the second light source, including the standard center position, standard spot shape, and standard brightness value; Compare the actual spot position with the standard center position, the actual spot shape with the standard spot shape, and the actual brightness value with the standard brightness value; If the comparison result does not exceed the set threshold, it is determined that the wheel hub under test does not need to be polished; if the comparison result exceeds the set threshold, it is determined that the wheel hub under test needs to be polished, the wheel hub under test is marked as a wheel hub that needs to be polished, and a polishing command is triggered.

8. The wheel hub hole grinding control method according to claim 7, characterized in that, The calculation of the defect parameters of the wheel hub to be polished includes: Calculate the deviation distance between each actual center position and the standard center position; Calculate the contour deformation of each actual spot shape compared to the standard spot shape; The defect type is determined by matching the actual brightness value against a defect type threshold library. The three-dimensional coordinates of the defect and the required grinding thickness of the defect are mapped based on the deviation distance and the contour deformation amount.

9. The wheel hub hole grinding control method according to claim 8, characterized in that, The grinding compensation data generated based on the defect parameters of the wheel hub under test includes: Match the defect type influence function according to the defect type; Input the three-dimensional coordinates and the thickness to be ground into the function to generate feed rate compensation, rotation speed compensation and radial pressure compensation.

10. A wheel hub hole grinding control system, characterized in that, include: The loading and unloading conveyor line includes a roller conveyor line. The bottom of the loading and unloading conveyor line is equipped with a lifting and positioning mechanism, and the loading and unloading conveyor line at the lifting and positioning mechanism is designed with a hollow structure. The enclosed machine cover has an inlet and an outlet at both ends of the loading and unloading conveyor line, and a flexible light-blocking curtain is provided at both the inlet and the outlet. The top of the enclosed machine cover is provided with a second camera and a second light source for tilting and lighting the inner wall of the hub hole. When the hub to be inspected is positioned by the lifting and positioning mechanism, the shooting direction of the second camera is aligned with the center line of the hub hole of the hub to be inspected. The second light plate is located below the cutout position of the loading and unloading conveyor line and faces the second camera. An image processing unit, wherein the input terminal of the image processing unit is electrically connected to the output terminal of the second camera; The control unit has its input terminal electrically connected to the output terminal of the image processing unit, and its output terminal electrically connected to the input terminals of the loading and unloading conveying unit, the lifting and positioning mechanism, the second light source, and the camera. A storage unit is used to store a second standard light spot image when a defect-free wheel hub is polished. The storage unit is electrically connected to the image processing unit and the control unit, respectively. The control unit is configured to perform the wheel hub hole grinding control method according to any one of claims 1-9.

Images