Distributed line laser sensor scanning method for irregular large workpiece defects

Abstract

The invention discloses a distributed line laser sensor scanning method for irregular large workpiece defects, and belongs to the field of line laser sensor scanning methods. In a traditional large workpiece detection method, a laser scanning beam of each line laser sensor can influence cameras of other adjacent line laser sensors, so that images collected by the cameras are distorted. A distributed line laser sensor scanning method for irregular large workpiece defects comprises the following steps: designing a cuboid, and completely covering the to-be-detected surface of an irregular large workpiece and the projection of the irregular large workpiece on the horizontal ground; constructing a three-dimensional coordinate system on a projection plane of the irregular large workpiece on a horizontal plane, and determining a formula expression mode of a new coordinate of the line laser sensor; re-determining the coordinates of each line laser sensor in the three-dimensional coordinate system, and distributing the coordinates into a step shape; a line laser sensor set is used for scanning from the head end of the large workpiece. The method reduces the scanning time cost and economic cost of the line laser sensor, and improves the scanning precision.

Description

Technical Field

[0001] The present invention relates to a scanning method for defects of large workpieces, and particularly to a distributed line laser sensor scanning method for defects of irregular large workpieces. Background Art

[0002] With the development of society, people have higher and higher requirements for product quality. Avoiding defects on the surface of workpieces has become an important step in workpiece production; for example, defect detection is required for the production of automobile skeletons, large industrial machine tool parts, military workpieces, etc. In the process of detecting defects of large workpieces, multiple three-dimensional laser scanners are often required to ensure the accuracy of the detection results. In order to enable users to use perfect products, defects that may affect the detection accuracy must be removed.

[0003] When traditional line laser sensors detect large workpieces, they use a linear arrangement for detection, that is, the line laser sensors are arranged in a row. However, during the detection process, the shooting range of the laser sensor camera is too large, and it can not only shoot the laser scanning beam of this laser sensor, but also has a chance to shoot the laser scanning beam of the laser sensor adjacent to this laser sensor, resulting in distortion of the image captured by the camera of this laser sensor and inaccurate detection of defects of large workpieces.

[0004] Currently, this problem exists in the detection of many material workpieces. Therefore, some manufacturers will conduct sampling inspection after unified inspection, which not only wastes time but also inevitably misses some defects; the present invention introduces a three-dimensional coordinate positioning method and redesigns the coordinates of the laser sensors to avoid the influence of the laser on the camera when the laser sensors scan the workpieces, and improves the workpiece detection accuracy. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem in the traditional large workpiece detection method that the laser scanning beam of each line laser sensor affects the cameras of other adjacent line laser sensors, resulting in distortion of the images captured by the cameras, and to propose a distributed line laser sensor scanning method for defects of irregular large workpieces.

[0006] The above purpose is achieved by the following technical solutions:

[0007] A distributed line laser sensor scanning method for defects of irregular large workpieces, the method is implemented through the following steps:

[0008] Step 1: Design a cuboid to completely cover the surface to be detected of the irregular large workpiece and its projection on the horizontal ground, and the size of the designed cuboid can completely contain the irregular large workpiece; wherein, the irregular large workpiece refers to a large workpiece with a polyhedron that is not a cuboid, including spheres, ellipsoids, and spheroids.

[0009] Step 2: Use a new method to construct a three-dimensional coordinate system on the projection plane of the irregular large workpiece on the horizontal plane, and determine the formula expression of the new coordinates of the line laser sensor;

[0010] Step 3: Use the coordinate origin and coordinate axes of the constructed three-dimensional coordinate system to re-determine the coordinates of each line laser sensor in the three-dimensional coordinate system, and distribute multiple line laser sensors in a stepped shape according to the re-determined coordinates on the projection plane of the irregular large workpiece on the horizontal plane;

[0011] Step 4: Fix all the line laser sensors arranged in the previous step into one body to form a line laser sensor set, and use the line laser sensor set to scan starting from the head end of the large workpiece; then, judge whether the defect detection of the large workpiece is completed according to the scanning length of the line laser sensor; among them, the scanning length of each line laser sensor is fixed, and the specific scanning length of each line laser sensor is:

[0012] ① The scanning length of line laser sensor 1 is b or l;

[0013] ② The scanning length of line laser sensor 2 is 2b + Δl or 2l + Δl;

[0014] ③ The scanning length of line laser sensor N is nb + (n - 1)Δl or nl + (n - 1)Δl;

[0015] Among them, the length of the surface to be detected of the regular geometric large workpiece or the regular large workpiece after geometrization is l, the width is b, and b ≤ l; N represents the sorting of the line laser sensors; n represents the number of line laser sensors; Δl represents the distance maintained between line laser sensor N - 1 and line laser sensor N on the Y axis; if the cameras of any two line laser sensors cannot capture the laser scanning images of each other, then Δl = 0.

[0016] Further, the process of designing the cuboid in Step 1 is specifically:

[0017] (1) Place the irregular large workpiece on the horizontal ground with the part to be detected facing up, and project the part to be detected onto a plane parallel to the horizontal ground;

[0018] (2) Gradually increase the radius with the center of the projection pattern obtained in the previous step as the center of the circle until the drawn circle includes the projection pattern, so that at least one vertex of an angle of the projection pattern is on the circle of the drawn circle;

[0019] (3) Inscribe the circle obtained in the previous step in a square, and the side length of the square is l, and measure the height of the irregular large workpiece placed on the horizontal ground at this time;

[0020] (4) The regular large workpiece after geometrization is a geometric body with a length of l, a width of l, and a height of c, and the surface to be detected is a square with a length of l and a width of l.

[0021] Further, the process of constructing a three-dimensional coordinate system, determining the coordinates of the line laser sensor, and expressing them in a formula in step two is specifically as follows:

[0022] (1) Select the coordinate origin: Select the intersection of two sides of the surface to be detected of the regular large workpiece or the regular large workpiece after geometrization as the three-dimensional coordinate origin;

[0023] (2) Select the coordinate axes: Establish a coordinate system on the surface to be detected, and extend along two sides of the regular large workpiece or the regular large workpiece after geometrization to form the X-axis and the Y-axis respectively; extend the long side to form the X-axis, and extend the wide side to form the Y-axis. Extend in the direction perpendicular to the XY-axis of the surface to be detected of the regular large workpiece or the regular large workpiece after geometrization starting from the three-dimensional coordinate origin to form the Z-axis, then the established Z-axis is perpendicular to the XY-axis;

[0024] (3) The three-dimensional coordinate system is established on the surface to be detected of the regular large workpiece or the regular large workpiece after geometrization.

[0025] Further, the step of arranging multiple line laser sensors side by side in a stepped shape in step three, each line laser sensor is in the xz plane, arranged in a stepped shape, re-determining the coordinates of each line laser sensor in the three-dimensional coordinate system, and arranging the line laser sensors according to the re-determined coordinates is specifically as follows:

[0026] (1) Assume the width of the line laser sensor is x, the length is k, and all line laser sensors are fixed at the same height z, that is, the height of the line laser sensor is z. Then the scanning width of the laser beam of the line laser sensor on the surface to be detected of the regular large workpiece after geometrization is d, the straight-line length of the camera acquisition range of the line laser sensor is f, and f >> k. The length of the surface to be detected of the regular large workpiece is l, the width is l or b, and l >> x, b >> k. Make the laser scanning beam of the line laser sensor parallel to the X-axis;

[0027] ① The length of the surface to be detected of the regular geometric body large workpiece or the regular large workpiece after geometrization is l, the width is l or b, and l >> x, b >> k;

[0028] ② If l / x = n, then n line laser sensors are required;

[0029] ③ If l / x = n.m, when m > 5, n + 1 line laser sensors are required, and when m < 5 or m = 5, n line laser sensors are required;

[0030] (2) In the XZ plane; in order to avoid the laser interference of other 3D laser scanning operations when the line laser sensor acquires images, each line laser sensor needs to have a certain interval in the XZ plane; the scanning width of the laser beam of the line laser sensor on the surface of the large workpiece to be detected is d. Take the projection center coordinates of the line laser sensor in the XZ plane. After the Z coordinate is determined, the X coordinate is 1 / 2 of the scanning width of the line laser sensor. Then:

[0031] The coordinates of line laser sensor 1 are (1 / 2d, z);

[0032] The coordinates of line laser sensor 2 are (3 / 2d, z);

[0033] …

[0034] The coordinates of line laser sensor N are (3(n - 1) / 2d, z);

[0035] (3) In the YZ plane; in the YZ plane, line laser sensor N - 1 and line laser sensor N are kept at a distance of Δl on the Y axis, and N laser sensors are at the same height on the Z axis; among them, the calculation method of Δl is as follows:

[0036] ① The distance between the laser scanning beam of the Nth line laser sensor and the laser scanning beam of the (N - 1)th line laser sensor is e. When the camera of the Nth line laser sensor cannot scan the laser scanning beam of the (N - 1)th line laser sensor, measure the size of e;

[0037] ② Since e is the distance at which the camera of the Nth line laser sensor cannot scan the laser scanning beam of the (N - 1)th line laser sensor, then e ≈ Δl + k;

[0038] ③ It is obtained that Δl = e - k. When the line laser sensors are separated by Δl in the YZ plane, the camera of each line laser sensor will not be interfered by the laser scanning beams of other line laser sensors;

[0039] ④ Keep a distance of Δl between the Nth line laser sensor and the (N - 1)th line laser sensor in the YZ plane. The camera of the Nth line laser sensor cannot scan the laser scanning beam of the (N - 1)th line laser sensor. Thus, the coordinates of the line laser sensor in the YZ plane are obtained. This coordinate is the coordinate of the projection point of the geometric center of the line laser sensor in the YZ plane. The coordinates are as follows:

[0040] The coordinates of the 1st line laser sensor are (1 / 2k, z);

[0041] The coordinates of the 2nd line laser sensor are ((3 / 2 + Δl)k, z);

[0042] The coordinates of the Nth line laser sensor are ((3(n - 1) / 2 + (n - 1)Δl)k, z);

[0043] (4) Finally, the coordinates of the line laser sensor in the three-dimensional coordinate system are:

[0044] The coordinates of the first line laser sensor are (1 / 2d, 1 / 2k, z);

[0045] The coordinates of the second line laser sensor are (3 / 2d, (3 / 2+Δl)k, z);

[0046] …

[0047] The coordinates of the Nth line laser sensor are (3(n-1) / 2d, (3(n-1) / 2+(n-1)Δl)k, z).

[0048] The beneficial effects of the present invention are:

[0049] The present invention introduces a three-dimensional coordinate positioning method and redesigns the coordinates of the laser sensor to avoid the influence of the laser on the camera when the laser sensor scans the workpiece, thereby improving the workpiece detection accuracy.

[0050] When traditional line laser sensors detect large workpieces, they use a linear arrangement detection method that arranges the line laser sensors in a row. However, during the detection process, the shooting range of the laser sensor camera is too large, and it can not only capture the laser scanning beam of the laser sensor, but also has a chance to capture the laser scanning beam of the laser sensor adjacent to the laser sensor, resulting in distortion of the laser sensor camera and inaccurate detection of large workpiece defects. Therefore, the present invention adopts a line laser sensor step distribution structure design method to replace the traditional linear distribution structure design method, and redesigns the position of the line laser sensor. In addition, in order to avoid the interference of the laser scanning beams between adjacent line laser sensors on the camera and affect the image recognition effect, a step layout method is adopted, that is, each line laser sensor is in the same plane, and is arranged in a step-by-step manner.

[0051] In summary, compared with the traditional distribution of line laser sensors, the operation method of the present invention is simpler and easier, the scanning results are more accurate, the efficiency is higher and the image acquisition accuracy is higher; secondly, compared with the traditional method that requires multiple image acquisitions to improve accuracy, the acquisition process of the method of the present invention takes less time, can quickly determine the defects of large workpieces, shorten the construction period, and reduce the inspection cost; finally, the method of the present invention enables adjacent line laser sensors to capture images within the scanning range as much as possible, reducing the phenomenon of repeated capture of targets. In this way, the number of scanning devices used can be reduced, thereby saving scanning costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A flow chart of the method according to the present invention;

[0053] Figure 2 It is a distribution diagram of line laser sensors on the YX plane;

[0054] Figure 3 It is a diagram of the parameters of a regular geometric body and the coordinate system components;

[0055] Figure 4 It is an overview diagram of the distribution of line laser sensors;

[0056] Figure 5 It is a distribution diagram of line laser sensors on the ZX plane;

[0057] Figure 6 It is a distribution diagram of line laser sensors on the ZY plane;

[0058] Figure 7 It is an illustration of the distance Δl between line laser sensors on the YZ plane, where the red area is the laser scanning area and the blue area is the area where the camera captures images;

[0059] Figure 8 It is a diagram of the parameters of an irregular geometric body and the construction of the coordinate system;

[0060] Figure 9 It is an illustration showing an example of the positional relationship between the projection of an irregular large workpiece and a circle drawn by gradually increasing the radius with the center of the projection of the irregular large workpiece on the horizontal plane as the center until the drawn circle just encloses the projection figure, using a trapezoid to represent the projection of the irregular large workpiece;

[0061] Figure 10 It is a schematic diagram of the distance from the top surface of a regular large workpiece after geometrization to the ground. Specific embodiments

[0062] To make the objectives, 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 with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Specific embodiment one:

[0064] Please refer to Figures 1-10 , a distributed line laser sensor scanning method for defects of irregular large workpieces in this embodiment, as shown in Figure 1 . The method is implemented through the following steps:

[0065] Step 1: Design a cuboid to completely cover the surface to be detected of the irregular large workpiece and its projection on the horizontal ground, and the size of the designed cuboid can completely contain the irregular large workpiece; wherein, the irregular large workpiece refers to a large workpiece with a polyhedron that is not a cuboid, including spheres, ellipsoids, spheroids, etc.;

[0066] Step 2: In the present invention, the step of establishing a three-dimensional coordinate system is particularly important, and multiple three-dimensional laser scanners are often required to ensure the accuracy of the detection results during the detection of large workpiece defects. Therefore, a three-dimensional coordinate system is constructed in a new way on the projection plane of the irregular large workpiece on the horizontal plane, and the formula expression for determining the new coordinates of the line laser sensor is obtained. The coordinates of the line laser sensor can be determined simply and quickly by using the method of the present invention;

[0067] Step 3: Use the coordinate origin and coordinate axes of the constructed three-dimensional coordinate system to re-determine the coordinates of each line laser sensor in the three-dimensional coordinate system, and distribute multiple line laser sensors in a stepped manner according to the re-determined coordinates on the projection plane of the irregular large workpiece on the horizontal plane, as Figure 2 shown;

[0068] Step 4: Fix all the line laser sensors arranged in the previous step into one body to form a set of line laser sensors. When detecting the defects of the large workpiece, there is no need to move the large workpiece, and the set of line laser sensors is used to scan from the head end of the large workpiece; then, it is judged whether the detection of the large workpiece defects is completed according to the scanning length of the line laser sensor; wherein, the scanning length of each line laser sensor is fixed, and the specific scanning length of each line laser sensor is:

[0069] ① The scanning length of line laser sensor 1 is b or l;

[0070] ② The scanning length of line laser sensor 2 is 2b + Δl or 2l + Δl;

[0071] ③ The scanning length of line laser sensor N is nb + (n - 1)Δl or nl + (n - 1)Δl;

[0072] wherein, the length of the surface to be detected of the regular geometric large workpiece or the regular large workpiece after geometric transformation is l, the width is b, and b ≤ l. When the width is equal to the length, b = l; N represents the sorting order of the line laser sensors; n represents the number of line laser sensors; Δl represents the distance maintained between line laser sensor N - 1 and line laser sensor N on the Y-axis; if the cameras of any two line laser sensors of this brand cannot capture the laser scanning images of each other when the two line laser sensors are arranged compactly front and back, then Δl = 0, as Figure 2As described above, Δl shown in enables the image capture between adjacent line laser sensors within the scanning range as much as possible, without the phenomenon that the camera between adjacent line laser sensors captures the laser images of adjacent laser sensors, resulting in duplicate capture of the target. In this way, the number of scanning devices can be reduced, thereby saving the scanning cost. Specific Embodiment 2:

[0074] Different from Specific Embodiment 1, in a distributed line laser sensor scanning method for defects of irregular large workpieces in this embodiment, the process of designing the cuboid in Step 1 is specifically as follows:

[0075] (1) Place the irregular large workpiece stably on the horizontal ground with the part to be detected facing upward, and project the part to be detected onto a plane parallel to the horizontal ground;

[0076] (2) With the center of the projected figure obtained in the previous step as the center, gradually increase the radius to draw a circle until the drawn circle just includes the projected figure, and make at least one vertex of an angle of the projected figure on the circle of the drawn circle. For example, if the projected figure is a trapezoid, then one vertex of an angle of the trapezoid is on the circle of the drawn circle; if the projected figure is an isosceles triangle or an equilateral triangle, then three vertices of the angles of the isosceles triangle or the equilateral triangle are on the circle of the drawn circle; as Figure 9 shown;

[0077] (3) Inscribe the circle obtained in the previous step in a square, so that the circle is contained in the square and has four tangent points with the square. The side length of the square is l, and measure the height of the irregular large workpiece stably placed on the horizontal ground at this time, which is C; as Figure 10 shown, the distance from the top surface to the ground is the height C of the tetrahedron;

[0078] (4) The geometrically regular large workpiece is a geometric body with a length of l, a width of l, and a height of c, and the surface to be detected is a square with a length of l and a width of l. In the present invention, when establishing a coordinate system for an actually irregular large workpiece, a coordinate system is established for the geometrically regular large workpiece formed after regularizing the irregular large workpiece. Specific Embodiment 3:

[0080] Different from Specific Embodiment 2, in a distributed line laser sensor scanning method for defects of irregular large workpieces in this embodiment, the process of constructing a three-dimensional coordinate system, determining the coordinates of the line laser sensor, and expressing them in a formula way in Step 2 is specifically as follows:

[0081] (1) Select the coordinate origin: Select the intersection of two sides of the surface to be detected of the regular large workpiece or the geometrically regular large workpiece as the three-dimensional coordinate origin; as Figure 3as shown;

[0082] (2) Select the coordinate axes: Establish a coordinate system on the surface to be detected. Extend along both sides of the regular large workpiece or the geometrically regular large workpiece to form the X-axis and the Y-axis respectively; extend the long side to form the X-axis, and extend the wide side to form the Y-axis. Starting from the origin of the three-dimensional coordinates, extend in the direction perpendicular to the XY plane of the surface to be detected of the regular large workpiece or the geometrically regular large workpiece to form the Z-axis. Then the established Z-axis is perpendicular to the XY axis;

[0083] (3) The three-dimensional coordinate system is established on the surface to be detected of the regular large workpiece or the geometrically regular large workpiece. Specific Embodiment 4:

[0085] Different from Specific Embodiment 3, in a distributed line laser sensor scanning method for detecting defects of irregular large workpieces in this embodiment, in the step of arranging multiple line laser sensors side by side in a stepped shape, each line laser sensor is in the xz plane and is arranged in a stepped shape. The step of re-determining the coordinates of each line laser sensor in the three-dimensional coordinate system and arranging the line laser sensors according to the re-determined coordinates is specifically as follows:

[0086] (1) Assume the width of the line laser sensor is x and the length is k. Fix all the line laser sensors at the same height z, that is, the height of the line laser sensor is z. Then the scanning width of the laser beam of the line laser sensor on the surface to be detected of the geometrically regular large workpiece is d, and the straight-line length of the camera acquisition range of the line laser sensor is f. And according to the working parameters of the line laser sensors on the market, f >> k. The length of the surface to be detected of the regular large workpiece is l, and the width is l or b, and l >> x, b >> k. Make the laser scanning beam of the line laser sensor parallel to the X-axis;

[0087] If l / x is an integer n, then n line laser scanning units are required. If l / x is not an integer but a decimal n.m (since the large workpiece is much larger than the line laser sensor, it is only accurate to one decimal place; n is the integer part, and only one digit is taken for the decimal part, m is the decimal part) and m > 5, then n + 1 line laser sensors are required. If m < 5 or m = 5, then n line laser sensors are required; as Figure 4 , for clear expression, it is represented in the form of a formula;

[0088] ① The length of the surface to be detected of the regular geometric large workpiece or the geometrically regular large workpiece is l, and the width is l or b, and l >> x, b >> k;

[0089] ② If l / x = n, then n line laser sensors are required;

[0090] ③ If l / x = n.m, when m > 5, n + 1 line laser sensors are required; when m < 5 or m = 5, n line laser sensors are required;

[0091] (2) In the XZ plane; to avoid the laser interference of other 3D laser scanners when the line laser sensor collects images, each line laser sensor needs to have a certain interval in the XZ plane; the scanning width of the laser beam of the line laser sensor on the large workpiece to be detected is d. Take the projection center coordinates of the line laser sensor in the XZ plane. After the Z coordinate is determined, the X coordinate is 1 / 2 of the scanning width of the line laser sensor. Then:

[0092] The coordinates of line laser sensor 1 are (1 / 2d, z);

[0093] The coordinates of line laser sensor 2 are (3 / 2d, z);

[0094] …

[0095] The coordinates of line laser sensor N are (3(n - 1) / 2d, z); as Figure 5 shown;

[0096] (3) In the YZ plane; in the YZ plane, line laser sensor N - 1 and line laser sensor N on the Y axis are kept at a distance of Δl, and N laser sensors are at the same height on the Z axis; among them, the calculation method of Δl is as follows:

[0097] ① The distance between the laser scanning beam of the Nth line laser sensor and the laser scanning beam of the (N - 1)th line laser sensor is e. When the camera of the Nth line laser sensor just cannot scan the laser scanning beam of the (N - 1)th line laser sensor, the size of e can be measured under this condition;

[0098] (Since the camera of the line laser sensor scans forward, there is no need to worry that the camera of line laser sensor N - 1 will be affected by the laser scanning beam of line laser sensor N);

[0099] ② Since e is the distance when the camera of the Nth line laser sensor just cannot scan the laser scanning beam of the (N - 1)th line laser sensor, then e ≈ Δl + k;

[0100] ③ It is obtained that Δl = e - k. When the line laser sensors are separated by Δl in the YZ plane, the cameras of each line laser sensor will not be interfered by the laser scanning beams of other line laser sensors; as Figure 6 , Figure 7 shown;

[0101] ④The distance between the Nth line laser sensor and the (N - 1)th line laser sensor in the YZ plane is Δl. The camera of the Nth line laser sensor just cannot scan the laser scanning beam of the (N - 1)th line laser sensor, so as to obtain the coordinates of the line laser sensor in the YZ plane. This coordinate is the coordinate of the projection point of the geometric center of the line laser sensor on the YZ plane, and the coordinates are as follows:

[0102] The coordinates of the 1st line laser sensor are (1 / 2k, z);

[0103] The coordinates of the 2nd line laser sensor are ((3 / 2 + Δl)k, z);

[0104] The coordinates of the Nth line laser sensor are ((3(n - 1) / 2 + (n - 1)Δl)k, z);

[0105] (4) Finally, the coordinates of the line laser sensor in the three-dimensional coordinate system can be obtained as follows:

[0106] The coordinates of the 1st line laser sensor are (1 / 2d, 1 / 2k, z);

[0107] The coordinates of the 2nd line laser sensor are (3 / 2d, (3 / 2 + Δl)k, z);

[0108] …

[0109] The coordinates of the Nth line laser sensor are (3(n - 1) / 2d, (3(n - 1) / 2 + (n - 1)Δl)k, z); as Figure 2 shown.

[0110] The embodiments disclosed in the present invention are preferred embodiments, but not limited thereto. Those of ordinary skill in the art can easily understand the spirit of the present invention according to the above embodiments and make different extensions and changes. However, as long as they do not depart from the spirit of the present invention, they are within the protection scope of the present invention.

Claims

1. A distributed line laser sensor scanning method for defects of irregular large workpieces, characterized in that: The method is implemented through the following steps: Step 1: Design a cuboid to completely cover the surface to be detected of the irregular large workpiece and its projection on the horizontal ground, and the size of the designed cuboid can completely contain the irregular large workpiece; wherein, the irregular large workpiece refers to a large workpiece with a polyhedron that is not a cuboid, including spheres, ellipsoids, and spheroids; Step 2: Use a new method to construct a three-dimensional coordinate system on the projection plane of the irregular large workpiece on the horizontal plane, and determine the formula expression of the new coordinates of the line laser sensor; Step 3: Use the coordinate origin and coordinate axes of the constructed three-dimensional coordinate system to re-determine the coordinates of each line laser sensor in the three-dimensional coordinate system, and distribute multiple line laser sensors in a stepped shape according to the re-determined coordinates on the projection plane of the irregular large workpiece on the horizontal plane; Step 4: Fix all the line laser sensors arranged in the previous step into one body to form a line laser sensor set, and use the line laser sensor set to scan from the head end of the large workpiece; then, determine whether the defect detection of the large workpiece is completed according to the scanning length of the line laser sensor; wherein, the scanning length of each line laser sensor is fixed, and the specific scanning length of each line laser sensor is: ① The scanning length of line laser sensor 1 is b or l; ② The scanning length of line laser sensor 2 is 2b + Δl or 2l + Δl; ③ The scanning length of line laser sensor N is nb + (n - 1)Δl or nl + (n - 1)Δl; wherein, the length of the surface to be detected of the regular geometric large workpiece or the regular large workpiece after geometric transformation is l, the width is b, and b ≤ l; N represents the sorting of the line laser sensors; n represents the number of line laser sensors; Δl represents the distance maintained between line laser sensor N - 1 and line laser sensor N on the Y-axis line; if the cameras of any two line laser sensors cannot capture the laser scanning images of each other, then Δl = 0.

2. A distributed line laser sensor scanning method for defects of irregular large workpieces according to claim 1, characterized in that: The process of designing the cuboid described in Step 1 is specifically: (1) Place the irregular large workpiece on the horizontal ground with the part to be detected facing up, and project the part to be detected onto a plane parallel to the horizontal ground; (2) Gradually increase the radius with the center of the projection pattern obtained in the previous step as the center of the circle until the drawn circle includes the projection pattern, and make at least one vertex of the angle of the projection pattern on the circle of the drawn circle; (3) Inscribe the circle obtained in the previous step in a square, and the side length of the square is l, and measure the height of the irregular large workpiece placed on the horizontal ground at this time; (4) The regular large workpiece after geometric transformation is a geometric body with a length of l, a width of l, and a height of c, and the surface to be detected is a square with a length of l and a width of l.

3. A distributed line laser sensor scanning method for defects of irregular large workpieces according to claim 1 or 2, characterized in that: The process of constructing the three-dimensional coordinate system, determining the coordinates of the line laser sensor, and expressing them in a formula way described in Step 2 is specifically: (1) Select the coordinate origin: Select the intersection of the two sides of the surface to be detected of the regular large workpiece or the regular large workpiece after geometric transformation as the three-dimensional coordinate origin; (2) Select the coordinate axes: Establish a coordinate system on the surface to be detected. Extend along two sides of the regular large workpiece or the geometrically regular large workpiece to form the X-axis and the Y-axis respectively; extend the long side to form the X-axis, and extend the wide side to form the Y-axis. Starting from the origin of the three-dimensional coordinates, extend in the direction perpendicular to the XY plane of the surface to be detected of the regular large workpiece or the geometrically regular large workpiece to form the Z-axis. Then the established Z-axis is perpendicular to the XY axis. (3) The three-dimensional coordinate system is established on the surface to be detected of the regular large workpiece or the geometrically regular large workpiece.

4. A distributed line laser sensor scanning method for defects of irregular large workpieces according to claim 3, characterized in that: The step of arranging multiple line laser sensors side by side in a stepped shape as described in Step 3, with each line laser sensor in the xz plane and arranged in a stepped shape, and re-determining the coordinates of each line laser sensor in the three-dimensional coordinate system and arranging the line laser sensors according to the re-determined coordinates is specifically as follows: (1) Assume the width of the line laser sensor is x and the length is k. Fix all the line laser sensors at the same height z, that is, the height of the line laser sensor is z. Then the scanning width of the laser beam of the line laser sensor on the surface to be detected of the geometrically regular large workpiece is d, and the straight-line length of the camera acquisition range of the line laser sensor is f, and f >> k. The length of the surface to be detected of the regular large workpiece is l, and the width is l or b, and l >> x, b >> k. Make the laser scanning beam of the line laser sensor parallel to the X-axis. ① The length of the surface to be detected of the regular geometric large workpiece or the geometrically regular large workpiece is l, and the width is l or b, and l >> x, b >> k; ② If l / x = n, then n line laser sensors are required; ③ If l / x = n.m, when m > 5, n + 1 line laser sensors are required, and when m < 5 or m = 5, n line laser sensors are required; (2) In the XZ plane; in order to avoid the laser of other three-dimensional laser scanners interfering with the line laser sensor when collecting images, each line laser sensor needs to have a certain interval in the XZ plane; the scanning width of the laser beam of the line laser sensor on the surface to be detected of the large workpiece is d. Take the projection center coordinates of the line laser sensor in the XZ plane. After the Z coordinate is determined, the X coordinate is 1 / 2 of the scanning width of the line laser sensor. Then: The coordinate of line laser sensor 1 is (1 / 2d, z); The coordinate of line laser sensor 2 is (3 / 2d, z); … The coordinate of line laser sensor N is (3(n - 1) / 2d, z); (3) In the YZ plane; in the YZ plane, keep a distance of Δl between line laser sensor N - 1 and line laser sensor N on the Y-axis, and the N line laser sensors are at the same height on the Z-axis; among them, the calculation method of Δl is as follows: ① The distance between the laser scanning beam of the Nth line laser sensor and the laser scanning beam of the (N - 1)th line laser sensor is e. When the camera of the Nth line laser sensor cannot scan the laser scanning beam of the (N - 1)th line laser sensor, measure the size of e; ② Since e is the distance that the camera of the Nth line laser sensor cannot scan the laser scanning beam of the (N - 1)th line laser sensor, then e ≈ Δl + k; ③ It is obtained that Δl = e - k. When the line laser sensors are separated by Δl in the YZ plane, the cameras of each line laser sensor will not be interfered by the laser scanning beams of other line laser sensors; ④ Keep a distance of Δl between the Nth line laser sensor and the (N - 1)th line laser sensor in the YZ plane. The camera of the Nth line laser sensor cannot scan the laser scanning beam of the (N - 1)th line laser sensor, so as to obtain the coordinates of the line laser sensors in the YZ plane. This coordinate is the coordinate of the projection point of the geometric center of the line laser sensor on the YZ plane. The coordinates are as follows: The coordinate of the 1st line laser sensor is (1 / 2k, z); The coordinate of the 2nd line laser sensor is ((3 / 2 + Δl)k, z); The coordinate of the Nth line laser sensor is ((3(n - 1) / 2 + (n - 1)Δl)k, z); (4) Finally, the coordinates of the line laser sensors in the three-dimensional coordinate system are obtained as follows: The coordinate of the 1st line laser sensor is (1 / 2d, 1 / 2k, z); The coordinate of the 2nd line laser sensor is (3 / 2d, (3 / 2 + Δl)k, z); … The coordinate of the Nth line laser sensor is (3(n - 1) / 2d, (3(n - 1) / 2 + (n - 1)Δl)k, z).

Images