Universal flange plate ball socket radius measuring device and method based on 3D vision

Abstract

The invention provides a universal flange plate ball socket radius measuring device and method based on 3D vision. The device comprises a material conveying and transferring device, a 3D measuring device and a grading device. The universal flange plate ball socket is arranged on the tray and sequentially passes through the material conveying and transferring device, the 3D measuring device and the grading device; the material conveying and transferring device comprises a first workbench, an industrial robot is arranged on the first workbench, a roller conveying belt and an automatic feeding and discharging mechanism are arranged on the side face of the first workbench, a first aluminum profile support is arranged above the roller conveying belt, and an industrial camera is connected to the surface of the first aluminum profile support. The device is mainly composed of a material conveying and transferring device, a 3D measuring device, a grading device and the like, and multiple functions of automatic feeding and discharging, sorting, measuring, grading and the like of universal flange plate ball sockets can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of mechanical measurement technology, and in particular to a 3D vision-based universal flange ball socket radius measurement device and method. Background Art

[0002] With the development of modern industrial technology, the demand for high-precision and high-efficiency measurement technology is becoming more and more urgent. Especially in the field of mechanical manufacturing, the geometric shape and dimensional accuracy of many parts directly affect the performance and life of the mechanical system. As an important connection and support component, the accurate measurement of the ball socket radius of the universal flange is of great significance to ensure its assembly quality and working performance.

[0003] The traditional method of measuring the ball socket radius of a universal flange mainly relies on contact measurement technology, usually using contact measurement equipment such as a coordinate measuring machine to obtain measurement data by physically contacting the surface of the part. However, the contact measurement method has limitations such as low efficiency, limited accuracy, and possible minor damage to the surface of the object being measured. In addition, contact measurement equipment such as a coordinate measuring machine usually requires manual operation, and the measurement process is cumbersome and time-consuming, which is difficult to meet the needs of mass production inspection. Summary of the invention

[0004] In view of the above problems, the present invention proposes a 3D vision-based universal flange ball socket radius measurement device and method. This method not only realizes non-contact high-precision automatic measurement of the flange ball socket radius, but also significantly improves the measurement efficiency and has good application prospects.

[0005] The technical means adopted by the present invention are as follows:

[0006] A 3D vision-based universal flange ball socket radius measuring device, comprising a material conveying and transferring device, a 3D measuring device and a grading device; the universal flange ball socket is arranged on a pallet, and passes through the material conveying and transferring device, the 3D measuring device and the grading device in sequence;

[0007] The material conveying and transferring device comprises a first workbench, an industrial robot is arranged on the first workbench, a roller conveyor belt and an automatic loading and unloading mechanism are arranged on the side of the first workbench, a first aluminum profile bracket is arranged above the roller conveyor belt, and an industrial camera is connected to the surface of the first aluminum profile bracket;

[0008] The 3D measuring device is arranged on the side of the material conveying and transferring device, and the 3D measuring device includes a first conveyor belt, a gantry is arranged above the first conveyor belt, two sides of the gantry are fixed to two sides of the first conveyor belt, a laser three-dimensional profiler is arranged at the lower part of the top bar of the gantry, first infrared sensors are arranged on both sides of the first conveyor belt at the front of the gantry, and second infrared sensors are arranged on both sides of the first conveyor belt at the rear of the gantry;

[0009] The grading device is arranged behind the 3D measuring device, and comprises a second workbench, a second conveyor belt and a third conveyor belt are respectively arranged on the left and right sides of the upper surface of the second workbench, and a transfer mechanism is arranged in the middle of the upper surface of the second workbench.

[0010] Furthermore, the automatic loading and unloading mechanism includes a telescopic cylinder that penetrates longitudinally and is fixed on a telescopic cylinder support plate, the lower surface of the telescopic cylinder support plate is connected to an aluminum profile bracket, the upper part of the telescopic cylinder is connected to the lower surface of the first metal plate, the second metal plate and the third metal plate are fixed to the upper surface of the telescopic cylinder support plate, the second metal plate is arranged on the front side of the telescopic cylinder, and the third metal plate is arranged on the rear side of the telescopic cylinder, the two sides of the synchronous belt conveyor are respectively fixed to the second metal plate and the third metal plate, and a roller conveyor belt is fixed above the first metal plate.

[0011] Furthermore, the transfer mechanism includes a bracket, a single-axis electric guide rail is fixed on the bracket, a slider of the single-axis electric guide rail is fixed to the upper end of the bracket plate, the lower end of the bracket plate is fixed to the guide cylinder, and the lower end of the guide cylinder is fixed to the pneumatic clamp.

[0012] The present invention also provides a method for measuring the radius of a universal flange ball socket based on 3D vision, which is implemented based on any one of the above-mentioned universal flange ball socket radius measuring devices based on 3D vision, and comprises the following steps:

[0013] S1. Place the universal flange ball socket to be tested on a tray, and convey the universal flange ball socket to be tested to a small roller conveyor belt via a roller conveyor belt;

[0014] S2, the industrial camera collects image data of the universal flange ball socket to be tested in the pallet, and the industrial robot sorts the universal flange ball socket to be tested in the pallet to the first conveyor belt;

[0015] S3, the universal flange ball socket to be tested is transported on the first conveyor belt. When the universal flange ball socket to be tested is transported to the position of the first infrared sensor, the laser three-dimensional profiler is triggered to collect point cloud data on the surface of the universal flange ball socket to be tested, and its radius is measured by an algorithm to determine whether it is qualified;

[0016] S4, when the universal flange ball socket passes the second infrared sensor position, the pneumatic clamp is triggered to clamp the universal flange ball socket;

[0017] S5. The transfer mechanism moves the qualified universal flange ball socket to the second conveyor belt, and the transfer mechanism moves the unqualified universal flange ball socket to the third conveyor belt.

[0018] Further, it also includes: S6. When all the universal flange sockets to be tested in the pallet are sorted, the telescopic cylinder drives the small roller conveyor to move vertically downward, and the empty pallet above the small roller conveyor is placed on the left end of the synchronous belt conveyor. The synchronous belt conveyor conveys the empty pallet to the unloading end on the right. The telescopic cylinder drives the small roller conveyor to reset upward, and the roller conveyor conveys the pallet with the universal flange sockets to be tested to the small roller conveyor of the automatic loading and unloading device to automatically measure the radius of the next batch of universal flange sockets.

[0019] Furthermore, S3 specifically includes the following steps:

[0020] S31, collecting point clouds of the universal flange ball socket surface by using a laser 3D profilometer, and removing outlier noise and sparse noise in the point clouds by using statistical filtering and radius filtering;

[0021] S32, calculating the centroid of the surface point cloud of the universal flange ball socket after filtering, and estimating the direction vectors of each principal axis of the ball socket point cloud by using the principal component analysis method;

[0022] S33, calculating the rotation matrix between each main axis direction vector of the flange ball socket and the spatial coordinate system, performing rotational translation transformation on the bevel gear to be measured, so that its center of mass coincides with the origin of the spatial coordinate system, and each main axis direction vector of the flange ball socket is parallel to the X-axis, Y-axis and Z-axis of the spatial coordinate system respectively;

[0023] S34, set the Z-axis threshold [z min ,z max ], traverse each point in the point cloud, retain the points whose Z-axis coordinates are within the threshold range, remove the points outside the threshold range, and extract the point cloud of the ball socket area;

[0024] S35, generating a spatial cutting plane, uniformly slicing and sampling the point cloud of the flange ball socket area along the Z axis of the coordinate system, and projecting the cross-sectional circle contour points of the intersection line of the ball socket point cloud extracted by each sampling and the spatial cutting plane onto a two-dimensional plane;

[0025] S36, performing circle fitting on each cross-sectional circle contour point set after being projected onto the two-dimensional plane, and re-projecting each fitted cross-sectional circle back into the three-dimensional space;

[0026] S37, setting a tolerance value, removing the set of fitted contour points with large errors, and adding the fitting points that meet the tolerance value setting to the set G;

[0027] S38, using a differential evolution algorithm to perform spatial sphere fitting on the fitting points in the set G to obtain the radius value of the flange socket;

[0028] S39. Compare the measured flange socket radius value with the specified value to determine whether it is qualified.

[0029] Further, S32 specifically includes the following steps:

[0030] S321. Assume that the flange ball socket point cloud after filtering is P, and calculate the point cloud centroid:

[0031]

[0032] Where N is the total number of points in the point cloud P, x i ,y i 、z i are the coordinates of the i-th point in the point cloud P respectively.

[0033] S322. Construct the covariance matrix of point cloud P:

[0034]

[0035] S323. Calculate the eigenvalue λ and eigenvector V of the covariance matrix T:

[0036] (T-λI)V=0

[0037] Where I is the unit matrix; λ is the eigenvalue of the covariance matrix, λ = (λ1, λ2, λ3), and the eigenvalue represents the distribution degree of the ball point cloud data in the main direction; V is the eigenvector corresponding to the eigenvalue, V = (V1, V2, V3), and the eigenvector represents the main component direction of the tooth surface point cloud data.

[0038] Furthermore, S35 specifically includes the following steps:

[0039] S351, construct the minimum bounding box of the ball socket area point cloud, calculate the height D3 of the minimum bounding box and the center point coordinates (x c ,y c ,z c );

[0040] S352, generate a spatial plane parallel to the XOY plane of the spatial coordinate system and tangent to the bottom of the ball and socket area point cloud. The spatial plane is expressed as:

[0041]

[0042] In the formula, i is the sampling number index;

[0043] S353, extract the cross-section circle contour points of the intersection line between the ball socket area point cloud and the space tangent plane, and add them to the set m i middle;

[0044] S354, move the spatial plane along the Z axis of the coordinate system at a fixed step length d, and repeat step S353 after each tangent plane movement until the sampling number N is reached, and all fitting contour points are extracted to obtain a sampling point set M = {m1, m2, ..., m N};

[0045] S355, project all subset cross-section circle contour points in the set M onto a plane parallel to the XOY coordinate system in sequence, and obtain a sample cross-section circle contour point set K = {k1, k2, ..., k N}.

[0046] Furthermore, the fitting circle in S36 specifically includes the following steps:

[0047] S361, using the RANSAC algorithm to fit the cross-sectional circle fitting points projected onto the two-dimensional plane, and screening out the relatively optimal inner point set T and the relatively optimal fitting circle parameters (a0, b0, r0);

[0048] S362, taking (a0, b0, r0) as initial parameters;

[0049] S363, establish error function:

[0050]

[0051] S364. Traverse the relative optimal point set T and calculate the Jacobian matrix J:

[0052]

[0053] S365. Calculate the parameter update amount using the Gauss-Newton method and update the parameters:

[0054] (Δa, Δb, Δr) = -(J T J) -1 J T f

[0055]

[0056] S366, repeat S362 to S365 until the parameter change between two consecutive iterations is less than the preset threshold or the maximum number of iterations is reached, the algorithm ends, and the optimal fitting cross-sectional circle is obtained.

[0057] Furthermore, the specific process of removing the fitting contour point set with large error by setting the tolerance value in S37 is as follows:

[0058] S371, converting the centers of all the fitting cross-section circles from the two-dimensional projection to the three-dimensional space, and performing spatial straight line fitting using the center points of these spatial fitting circles;

[0059] S372. Calculate the distance from the center of each spatial fitting circle to the fitting spatial straight line. If the distance is less than a threshold value L, discretize the spatial fitting circle and add the discrete points to the set G.

[0060] Compared with the prior art, the present invention has the following advantages:

[0061] The present invention integrates automatic loading, unloading, sorting, measuring and grading of universal flanges, realizes fully automated operations from loading to grading of universal flange ball sockets, and effectively reduces labor costs.

[0062] The present invention can realize non-contact automatic measurement of the flange ball socket radius, greatly improves the measurement efficiency, and avoids the damage to the flange ball socket that may be caused by traditional contact measurement.

[0063] The present invention is not only suitable for high-precision measurement of flange socket radius, but also has wide application potential. Its technical solution can be extended to the radius measurement of other hemispherical workpieces in the field of mechanical measurement, providing a universal and reliable solution for the size measurement of various hemispherical workpieces. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0065] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0066] Figure 2 It is a schematic diagram of the material conveying and transferring device of the present invention.

[0067] Figure 3 It is a schematic diagram of the automatic loading and unloading device of the present invention.

[0068] Figure 4 This is an exploded view of the automatic loading and unloading device of the present invention.

[0069] Figure 5 Schematic diagram of the 3D measurement device of the present invention.

[0070] Figure 6 It is a schematic diagram of the classification device of the present invention.

[0071] Figure 7 It is a schematic diagram of the transfer mechanism of the present invention.

[0072] Figure 8 It is an exploded view of the transfer mechanism of the present invention.

[0073] Fig. 9 This is a flow chart of the measurement algorithm of the present invention.

[0074] Fig.10 It is a schematic diagram of the starting and final positions of the cutting plane of the present invention.

[0075] Fig.11 It is a schematic diagram of the contour points of the circle projected onto a two-dimensional plane cross section according to the present invention.

[0076] Fig.12 It is a schematic diagram of the cross-section circle after fitting of the present invention.

[0077] In the figure: 1. Universal flange ball socket; 2. Pallet; 3. Material conveying and transferring device; 4. 3D measuring device; 5. Grading device; 31. First workbench; 32. Industrial robot; 33. Industrial camera; 34. First aluminum profile bracket; 35. Roller conveyor belt; 36. Automatic loading and unloading mechanism; 41. First conveyor belt; 42. Gantry; 43. Laser 3D profiler; 44. First infrared sensor; 45. Second infrared sensor; 51. Second conveyor belt; 52. Third conveyor belt; 5 3. Second workbench; 54. Transfer mechanism; 361. Screw; 362. First metal plate; 363. Telescopic cylinder; 364. Second metal plate; 365. Second aluminum profile bracket; 366. Third metal plate; 367. Synchronous belt conveyor; 368. Roller conveyor; 541. Single-axis electric guide rail; 542. Bracket; 543. First hexagon socket screw; 544. Slider; 545. Bracket plate; 546. Second hexagon socket screw; 547. Guide cylinder; 548. Pneumatic clamp. DETAILED DESCRIPTION

[0078] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0079] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0080] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0081] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0082] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0083] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0084] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0085] like Figure 1 As shown, the present invention provides a 3D vision-based universal flange ball socket radius measuring device, including: a universal flange ball socket 1, a tray 2, a material conveying and transferring device 3, a 3D measuring device 4, and a grading device 5.

[0086] The universal flange socket 1 to be tested is placed in the pallet 2 and is transferred to the small roller conveyor 368 by the roller conveyor 31 in the material conveying and transferring device 3. The industrial camera 33 is used to collect image data of the universal flange socket to be tested in the pallet, and guide the industrial robot 32 to sort the universal flange socket to be tested in the pallet to the conveyor 41 in the 3D measuring device 4. When the universal flange socket sorted on the conveyor 41 is transferred to the position of the first infrared sensor 44, the laser three-dimensional profiler 43 is triggered to collect point cloud data on the surface of the universal flange socket, and its radius is measured by the algorithm. When the universal flange socket after measurement is transferred to the position of the second infrared sensor 45 in the 3D measuring device 4, the pneumatic clamp 548 is triggered to clamp it, and the qualified universal flange socket is moved to the second conveyor 51 by the transfer mechanism 54, and the unqualified universal flange socket is moved to the third conveyor 52.

[0087] Furthermore, when all the sockets of the universal flanges to be tested in the tray 2 are sorted, the telescopic cylinder 363 in the material conveying and transferring device 1 drives the small roller conveyor 368 to move vertically downward, and the empty tray above the small roller conveyor 368 is placed on the left end of the synchronous belt conveyor 367. Subsequently, the synchronous belt conveyor 367 conveys the empty tray to the unloading end on the right. At the same time, the telescopic cylinder 363 drives the small roller conveyor 368 to reset upward, and the roller conveyor 31 re-transmits the tray with the sockets of the universal flanges to be tested to the small roller conveyor 368 of the automatic loading and unloading device 36, and the next batch of universal flange socket radii are automatically measured.

[0088] like Figure 2 As shown, the material conveying and transferring device mainly includes: a first workbench 31, an industrial robot 32, an industrial camera 33, a first aluminum profile bracket 34, a roller conveyor belt 35, and an automatic loading and unloading mechanism 36; the industrial robot 32 is fixed above the workbench 31; the industrial camera 33 is fixed on the first aluminum profile bracket; the automatic loading and unloading mechanism 36 is placed below the industrial camera; the roller conveyor belt 35 is connected to the automatic loading and unloading mechanism 36.

[0089] like Figure 3 and Figure 4 As shown, the automatic loading and unloading device in the material conveying and transferring device 3 mainly includes: screws 361, a first metal plate 362, a telescopic cylinder 363, a second metal plate 364, an aluminum profile bracket 365, a third metal plate 366, a synchronous belt conveyor 367, and a roller conveyor belt 368; the first metal plate 362 is fixed above the telescopic cylinder 363 by screws 361, and the aluminum profile bracket 365 is fixed below the telescopic cylinder 363 to support the telescopic cylinder 363; the second metal plate 364 and the third metal plate 366 are respectively installed on the front and rear sides of the telescopic cylinder 363, the synchronous belt conveyor 367 is fixed in the middle position between the second metal plate 364 and the third metal plate 366, and the roller conveyor belt 368 is fixed above the first metal plate 362.

[0090] like Figure 5 As shown, the 3D measuring device mainly includes: a first conveyor belt 41, a gantry 42, a laser three-dimensional profiler 43, a first infrared sensor 44, and a second infrared sensor 45.

[0091] like Figure 6 As shown, the grading device mainly includes: a second conveyor belt 51, a third conveyor belt 52, a second workbench 53, and a transfer mechanism 54; the second conveyor belt 51 and the second conveyor belt 52 are respectively fixed on the left and right sides of the second workbench 53, and the transfer mechanism 54 is fixed between the second conveyor belt 51 and the third conveyor belt 52.

[0092] like Figure 7 and Figure 8 As shown, the transfer mechanism mainly includes: a single-axis electric guide rail 541, a bracket 542, a first hexagon socket screw 543, a slider 544, a bracket plate 545, a second hexagon socket screw 546, a guide cylinder 547, and a pneumatic clamp 548; the single-axis electric guide rail 541 is fixed on the top of the bracket 542 by the first hexagon socket screw 543; the upper end of the bracket plate 545 is fixed to the slider 544 of the single-axis electric guide rail 541 by the second hexagon socket screw 546; the guide cylinder 547 is fixed to the bottom of the bracket plate 545 by the third hexagon socket screw 549, and the pneumatic clamp 548 is installed at the lower end of the guide cylinder 547; the single-axis electric guide rail 541 can drive the guide cylinder 547 and the pneumatic clamp 548 to move horizontally to the left and right; the guide cylinder 547 can drive the pneumatic clamp 548 to move vertically up and down.

[0093] The present invention also provides a method for measuring the radius of a universal flange ball socket based on 3D vision, comprising the following steps:

[0094] S1. Place the universal flange ball socket to be tested on a tray, and convey the universal flange ball socket to be tested to a small roller conveyor belt via a roller conveyor belt;

[0095] S2, the industrial camera collects image data of the universal flange ball socket to be tested in the pallet, and the industrial robot sorts the universal flange ball socket to be tested in the pallet to the first conveyor belt;

[0096] S3, the universal flange ball socket to be tested is transported on the first conveyor belt. When the universal flange ball socket to be tested is transported to the position of the first infrared sensor, the laser three-dimensional profiler is triggered to collect point cloud data on the surface of the universal flange ball socket to be tested, and its radius is measured by an algorithm to determine whether it is qualified;

[0097] S31: The surface point cloud of the universal flange ball socket is collected by a laser 3D profilometer, and the outlier noise and sparse noise in the point cloud are removed by statistical filtering and radius filtering;

[0098] S32: Calculate the centroid of the surface point cloud of the universal flange socket after filtering, and estimate the direction vectors of each principal axis of the socket point cloud by using principal component analysis (PCA);

[0099] S321. Assume that the flange ball socket point cloud after filtering is P, and calculate the point cloud centroid:

[0100]

[0101] Where N is the total number of points in the point cloud P, x i ,y i 、z i are the coordinates of the i-th point in the point cloud P respectively.

[0102] S322. Construct the covariance matrix of point cloud P:

[0103]

[0104] S323. Calculate the eigenvalue λ and eigenvector V of the covariance matrix T:

[0105] (T-λI)V=0

[0106] Where I is the unit matrix; λ is the eigenvalue of the covariance matrix, λ = (λ1, λ2, λ3), and the eigenvalue represents the distribution degree of the ball point cloud data in the main direction; V is the eigenvector corresponding to the eigenvalue, V = (V1, V2, V3), and the eigenvector represents the main component direction of the tooth surface point cloud data.

[0107] S33: Calculate the rotation matrix between the main axis direction vectors of the flange ball socket and the spatial coordinate system, perform rotational translation transformation on the bevel gear to make its center of mass coincide with the origin of the spatial coordinate system, and make the main axis direction vectors of the flange ball socket parallel to the X-axis, Y-axis and Z-axis of the spatial coordinate system respectively.

[0108] S331. Sort the eigenvectors from large to small according to the eigenvalues ​​of the flange ball socket point cloud covariance matrix. Where λ1≥λ2≥λ3, V1, V2, and V3 are the main axis direction vectors of the corresponding universal flange ball sockets. It can be expressed in matrix form as:

[0109]

[0110] S332. The direction vectors of the X, Y, and Z axes of the spatial coordinate system can be expressed as:

[0111]

[0112] S333. In order to align the main axis direction vector of the flange ball socket with the standard basis vector of the space coordinate system, the rotation matrix R can be expressed as:

[0113] R=I·V -1

[0114] S34: Set the Z-axis threshold [z min ,z max ], traverse each point in the point cloud, retain the points whose Z-axis coordinates are within the threshold range, remove the points outside the threshold range, and extract the point cloud of the ball socket area.

[0115] S35: Generate a spatial cutting plane, uniformly slice and sample the point cloud of the flange socket area along the Z axis of the coordinate system, and project the cross-sectional circle contour points of the intersection line of the socket point cloud extracted by each sampling and the spatial cutting plane onto a two-dimensional plane;

[0116] S351, construct the minimum bounding box of the ball socket area point cloud, calculate the height D3 of the minimum bounding box and the center point coordinates (x c ,y c ,z c );

[0117] S352, generate a spatial plane parallel to the XOY plane of the spatial coordinate system and tangent to the bottom of the ball and socket area point cloud. The spatial plane is expressed as:

[0118]

[0119] In the formula, i is the sampling number index;

[0120] S353, extract the cross-section circle contour points of the intersection line between the ball socket area point cloud and the space tangent plane, and add them to the set m i middle.

[0121] S354, move the spatial tangent plane along the Z axis of the coordinate system at a fixed step length d, and repeat step S53 after each tangent plane movement until the sampling number N is reached, and all fitting contour points are extracted to obtain a sampling point set M = {m1, m2, ..., m N}, the starting and final positions of the cutting plane are as follows Fig.10 shown.

[0122] S355. In order to further simplify the calculation and reduce the dimension of the data, all subset cross-section circle contour points in the set M are sequentially projected onto a plane parallel to the XOY coordinate system to obtain a sample cross-section circle contour point set K = {k1, k2, ..., k N}, the contour points of each cross-section circle projected onto the two-dimensional plane are as follows Fig.11 shown.

[0123] S36: performing circle fitting on each cross-sectional circle contour point set after being projected onto the two-dimensional plane, and re-projecting each fitted cross-sectional circle back to the three-dimensional space;

[0124] S61, using the RANSAC algorithm to fit the cross-sectional circle fitting points projected onto the two-dimensional plane, and screening out the relatively optimal inner point set T and the relatively optimal fitting circle parameters (a0, b0, r0);

[0125] S62, taking (a0, b0, r0) as initial parameters;

[0126] S63. Establish an error function:

[0127]

[0128] S64. Traverse the relative optimal point set T and calculate the Jacobian matrix J:

[0129]

[0130] S65. Calculate the parameter update amount using the Gauss-Newton method and update the parameters:

[0131] (Δa, Δb, Δr) = -(J T J) -1 J T f

[0132]

[0133] S66, repeat steps S62 to S65 until the parameter change between two consecutive iterations is less than the preset threshold or the maximum number of iterations is reached, the algorithm ends, and the optimal fitting cross-sectional circle is obtained. Fig.12 shown.

[0134] S37: Setting a tolerance value, removing the set of fitted contour points with large errors, and adding the fitted points that meet the tolerance value setting to the set G;

[0135] S71, converting the centers of all the fitting cross-section circles from the two-dimensional projection to the three-dimensional space, and performing spatial straight line fitting using the center points of these spatial fitting circles;

[0136] S72. Calculate the distance from the center of each spatial fitting circle to the fitting spatial straight line. If the distance is less than a threshold value L, discretize the spatial fitting circle and add the discrete points to the set G.

[0137] S38: performing spatial sphere fitting on the fitting points in the set G using a differential evolution algorithm to obtain a flange socket radius value;

[0138] S4, when the universal flange ball socket passes the second infrared sensor position, the pneumatic clamp is triggered to clamp the universal flange ball socket;

[0139] S5. The transfer mechanism moves the qualified universal flange ball socket to the second conveyor belt, and the transfer mechanism moves the unqualified universal flange ball socket to the third conveyor belt.

[0140] S6. When all the sockets of the universal flanges to be tested in the pallet are sorted, the telescopic cylinder drives the small roller conveyor to move vertically downward, and the empty pallet above the small roller conveyor is placed on the left end of the synchronous belt conveyor. The synchronous belt conveyor conveys the empty pallet to the unloading end on the right. The telescopic cylinder drives the small roller conveyor to reset upward, and the roller conveyor conveys the pallet with the sockets of the universal flanges to be tested to the small roller conveyor of the automatic loading and unloading device to automatically measure the radius of the sockets of the next batch of universal flanges.

[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A 3D vision-based universal flange ball socket radius measurement device, characterized in that: It comprises a material conveying and transferring device (3), a 3D measuring device (4) and a grading device (5); the universal flange ball socket (1) to be measured is arranged on a tray (2) and passes through the material conveying and transferring device (3), the 3D measuring device (4) and the grading device (5) in sequence; The material conveying and transferring device (3) comprises a first workbench (31), an industrial robot (32) is arranged on the first workbench (31), a roller conveyor belt (35) and an automatic loading and unloading mechanism are arranged on the side of the first workbench (31), a first aluminum profile bracket (34) is arranged above the roller conveyor belt (35), and an industrial camera (33) is connected to the surface of the first aluminum profile bracket (34); The 3D measuring device (4) is arranged on the side of the material conveying and transferring device (3), and the 3D measuring device (4) comprises a first conveyor belt (41), a gantry (42) is arranged above the first conveyor belt (41), two sides of the gantry (42) are fixed to two sides of the first conveyor belt (41), a laser three-dimensional profiler (43) is arranged at the lower part of the top bar of the gantry (42), first infrared sensors (44) are arranged on both sides of the first conveyor belt (41) at the front of the gantry (42), and second infrared sensors (45) are arranged on both sides of the first conveyor belt (41) at the rear of the gantry (42); The grading device (5) is arranged behind the 3D measuring device (4), and comprises a second workbench (53). A second conveyor belt (51) and a third conveyor belt (52) are respectively arranged on the left and right sides of the upper surface of the second workbench (53), and a transfer mechanism (54) is arranged in the middle of the upper surface of the second workbench (53).

2. The 3D vision-based universal flange ball socket radius measuring device according to claim 1, characterized in that: The automatic loading and unloading mechanism comprises a telescopic cylinder (363) which penetrates longitudinally and is fixed on a telescopic cylinder support plate; the lower surface of the telescopic cylinder support plate is connected to a second aluminum profile bracket (365); the upper part of the telescopic cylinder (363) is connected to the lower surface of a first metal plate (362); a second metal plate (364) and a third metal plate (366) are fixed on the upper surface of the telescopic cylinder support plate; the second metal plate (364) is arranged on the front side of the telescopic cylinder (363); the third metal plate (366) is arranged on the rear side of the telescopic cylinder (363); both sides of a synchronous belt conveyor (367) are respectively fixed to the second metal plate (364) and the third metal plate (366); a roller conveyor belt (368) is fixed above the first metal plate (362).

3. The 3D vision-based universal flange ball socket radius measuring device according to claim 1, characterized in that: The transfer mechanism (54) comprises a bracket (542), a single-axis electric guide rail (541) is fixed on the bracket (542), a slider (544) of the single-axis electric guide rail (541) is fixed to the upper end of a bracket plate (545), the lower end of the bracket plate (545) is fixed to a guide cylinder (547), and the lower end of the guide cylinder (547) is fixed to a pneumatic clamp (548).

4. A method for measuring the ball socket radius of a universal flange based on 3D vision, which is implemented based on the device for measuring the ball socket radius of a universal flange based on 3D vision according to any one of claims 1 to 3, characterized in that: The steps include: S1. Place the universal flange ball socket to be tested on a tray, and convey the universal flange ball socket to be tested to a small roller conveyor belt via a roller conveyor belt; S2, the industrial camera collects image data of the universal flange ball socket to be tested in the pallet, and the industrial robot sorts the universal flange ball socket to be tested in the pallet to the first conveyor belt; S3, the universal flange ball socket to be tested is transported on the first conveyor belt. When the universal flange ball socket to be tested is transported to the position of the first infrared sensor, the laser three-dimensional profiler is triggered to collect point cloud data on the surface of the universal flange ball socket to be tested, and its radius is measured by an algorithm to determine whether it is qualified; S4, when the universal flange ball socket passes the second infrared sensor position, the pneumatic clamp is triggered to clamp the universal flange ball socket; S5. The transfer mechanism moves the qualified universal flange ball socket to the second conveyor belt, and the transfer mechanism moves the unqualified universal flange ball socket to the third conveyor belt.

5. The method for measuring the ball socket radius of a universal flange based on 3D vision according to claim 4, characterized in that: Also includes: S6. When all the sockets of the universal flanges to be tested in the pallet are sorted, the telescopic cylinder drives the small roller conveyor to move vertically downward, and the empty pallet above the small roller conveyor is placed on the left end of the synchronous belt conveyor. The synchronous belt conveyor conveys the empty pallet to the unloading end on the right. The telescopic cylinder drives the small roller conveyor to reset upward, and the roller conveyor conveys the pallet with the sockets of the universal flanges to be tested to the small roller conveyor of the automatic loading and unloading device to automatically measure the radius of the sockets of the next batch of universal flanges.

6. The method for measuring the ball socket radius of a universal flange based on 3D vision according to claim 4, characterized in that: S3 specifically includes the following steps: S31, collecting point clouds of the universal flange ball socket surface by using a laser 3D profilometer, and removing outlier noise and sparse noise in the point clouds by using statistical filtering and radius filtering; S32, calculating the centroid of the surface point cloud of the universal flange ball socket after filtering, and estimating the direction vectors of each principal axis of the ball socket point cloud by using the principal component analysis method; S33, calculating the rotation matrix between each main axis direction vector of the flange ball socket and the spatial coordinate system, performing rotational translation transformation on the bevel gear to be measured, so that its center of mass coincides with the origin of the spatial coordinate system, and each main axis direction vector of the flange ball socket is parallel to the X-axis, Y-axis and Z-axis of the spatial coordinate system respectively; S34, set the Z-axis threshold [z min ,z max ], traverse each point in the point cloud, retain the points whose Z-axis coordinates are within the threshold range, remove the points outside the threshold range, and extract the point cloud of the ball socket area; S35, generating a spatial cutting plane, uniformly slicing and sampling the point cloud of the flange ball socket area along the Z axis of the coordinate system, and projecting the cross-sectional circle contour points of the intersection line of the ball socket point cloud extracted by each sampling and the spatial cutting plane onto a two-dimensional plane; S36, performing circle fitting on each cross-sectional circle contour point set after being projected onto the two-dimensional plane, and re-projecting each fitted cross-sectional circle back into the three-dimensional space; S37, setting a tolerance value, removing the set of fitted contour points with large errors, and adding the fitting points that meet the tolerance value setting to the set G; S38, using a differential evolution algorithm to perform spatial sphere fitting on the fitting points in the set G to obtain the radius value of the flange socket; S39. Compare the measured flange socket radius value with the specified value to determine whether it is qualified.

7. The method for measuring the ball socket radius of a universal flange based on 3D vision according to claim 5, characterized in that: S32 specifically includes the following steps: S321. Assume that the flange ball socket point cloud after filtering is P, and calculate the point cloud centroid: Where N is the total number of points in the point cloud P, x i ,y i 、z i are the coordinates of the i-th point in the point cloud P respectively; S322. Construct the covariance matrix of point cloud P: S323. Calculate the eigenvalue λ and eigenvector V of the covariance matrix T: (T-λI)V=0 Where I is the unit matrix; λ is the eigenvalue of the covariance matrix, λ = (λ1, λ2, λ3), and the eigenvalue represents the distribution degree of the ball point cloud data in the main direction; V is the eigenvector corresponding to the eigenvalue, V = (V1, V2, V3), and the eigenvector represents the main component direction of the tooth surface point cloud data.

8. The method for measuring the ball socket radius of a universal flange based on 3D vision according to claim 5, characterized in that: S35 specifically includes the following steps: S351, construct the minimum bounding box of the ball socket area point cloud, calculate the height D3 of the minimum bounding box and the center point coordinates (x c ,y c ,z c ); S352, generate a spatial plane parallel to the XOY plane of the spatial coordinate system and tangent to the bottom of the ball and socket area point cloud. The spatial plane is expressed as: In the formula, i is the sampling number index; S353, extract the cross-section circle contour points of the intersection line between the ball socket area point cloud and the space tangent plane, and add them to the set m i middle; S354, move the spatial plane along the Z axis of the coordinate system at a fixed step length d, and repeat step S353 after each tangent plane movement until the sampling number N is reached, and all fitting contour points are extracted to obtain a sampling point set M = {m1, m2, ..., m N }; S355, project all subset cross-section circle contour points in the set M onto a plane parallel to the XOY coordinate system in sequence, and obtain a sample cross-section circle contour point set K = {k1, k2, ..., k N }.

9. The method for measuring the ball socket radius of a universal flange based on 3D vision according to claim 5, characterized in that: The fitting circle in S36 specifically includes the following steps: S361, using the RANSAC algorithm to fit the cross-sectional circle fitting points projected onto the two-dimensional plane, and screening out the relatively optimal inner point set T and the relatively optimal fitting circle parameters (a0, b0, r0); S362, taking (a0, b0, r0) as initial parameters; S363, establish error function: S364. Traverse the relative optimal point set T and calculate the Jacobian matrix J: S365. Calculate the parameter update amount using the Gauss-Newton method and update the parameters: (Δa,Δb,Δr)=-(J T J) -1 J T f S366, repeat S362 to S365 until the parameter change between two consecutive iterations is less than the preset threshold or the maximum number of iterations is reached, the algorithm ends, and the optimal fitting cross-sectional circle is obtained.

10. The method for measuring the ball socket radius of a universal flange based on 3D vision according to claim 5, characterized in that: The specific process of removing the fitting contour point set with large error by setting the tolerance value in S37 is as follows: S371, converting the centers of all the fitted cross-section circles from the two-dimensional projection to the three-dimensional space, and performing spatial straight line fitting using the center points of these spatial fitting circles; S372. Calculate the distance from the center of each spatial fitting circle to the fitting spatial straight line. If the distance is less than a threshold value L, discretize the spatial fitting circle and add the discrete points to the set G.

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