Multi-position splicing measurement calibration method and device based on laser tracker guidance

Abstract

The present invention discloses a multi-position splicing measurement and calibration method based on laser tracker guidance, comprising: constructing a first transformation matrix for converting between the laser tracker measurement coordinate system and the processing site coordinate system based on the on-site ERS point; obtaining the center point coordinates of each target sphere seat through the laser tracker, and constructing a second transformation matrix between the calibration plate coordinate system and the processing site coordinate system based on the first transformation matrix; placing the target splicing block on the calibration plate, determining the second coordinate value of each feature point of the target splicing block in the calibration plate coordinate system, and converting the second coordinate value to the processing site coordinate system; obtaining the third coordinate value in the laser profiler coordinate system; and constructing a third transformation matrix between the laser profiler coordinate system and the processing site coordinate system based on the second coordinate value and the third coordinate value. The present invention also provides a multi-position splicing measurement and calibration device. The method provided by the present invention can effectively solve the problem that complex curved surfaces, large-area surfaces and gaps cannot be measured and mapped.

Description

Technical Field

[0001] The present invention belongs to the field of intelligent manufacturing, and in particular relates to a multi-position splicing measurement calibration method and device based on laser tracker guidance. Background Art

[0002] In the fields of aviation and shipbuilding engineering, laser trackers are usually required to construct large-scale measurement fields during measurement. However, although laser trackers have high measurement accuracy, they can only measure single-point coordinates and cannot measure continuous point clouds. Robot-portable line laser profilers can measure complex surfaces and large-area surfaces and obtain continuous point cloud data, but due to the influence of the robot's six degrees of freedom, the positioning accuracy is poor.

[0003] Patent document CN119334272A discloses a 3D laser profiler coordinate system conversion and calibration method. First, a calibration device is built; the calibration device has four calibration balls with adjustable spatial positions. Through adjustment, the four calibration balls are all intersected with the laser surface emitted by the profiler, and the centers of the balls are not coplanar. Subsequently, a world coordinate system is established using a laser tracker, and the coordinates of the centers of each calibration ball in the world coordinate system are obtained. Furthermore, the center coordinates and arc radius corresponding to the arc on the calibration ball surface are obtained by collecting images using the profiler, and then the center coordinates of each positioning ball under the profiler are obtained. Finally, the transformation matrix parameters are solved based on the coordinates of the obtained center in the two coordinate systems to obtain the transformation matrix, and the optimal result is selected.

[0004] Patent document CN117989977A discloses a method and device for measuring the installation position of the stator locating ribs of a large hydro-turbine generator, including: calibrating a positioning mark for the locating rib to be measured; calibrating the transformation relationship between the positioning mark and the coordinate system of a laser profiler or a laser scanner; measuring the spatial position of the positioning mark by a laser profiler or a laser scanner; obtaining the point cloud spatial coordinates of the contour or shape of the locating rib to be measured relative to the coordinate system of a laser tracker or a laser radar based on the contour or shape of the locating rib to be measured; and obtaining the installation measurement parameters of the locating rib to be measured based on the point cloud spatial coordinates. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-position splicing measurement and calibration method and system based on laser tracker guidance, which can effectively solve the problem that complex surfaces, large-area surfaces and gaps cannot be measured and mapped.

[0006] In order to achieve the first object of the present invention, the following technical solution is provided: a multi-position stitching measurement and calibration method based on laser tracker guidance, comprising the following steps:

[0007] Constructing a first transformation matrix for converting between a laser tracker measurement coordinate system and a machining site coordinate system based on the ERS points at the machining site;

[0008] Set four target sphere seats on the selected calibration plate and obtain the center point coordinates of each target sphere seat by using a laser tracker, and use the first transformation matrix to generate the first coordinate value corresponding to each target sphere in the processing site coordinate system;

[0009] A calibration plate coordinate system is constructed with a point on the calibration plate as the base point, and the theoretical coordinate values ​​of each target sphere seat on the calibration plate coordinate system are obtained;

[0010] Based on the first coordinate value and the theoretical coordinate value, point set matching is performed by using a singular value decomposition method to construct a second transformation matrix between the calibration plate coordinate system and the processing site coordinate system;

[0011] Placing a target splicing block on the calibration plate, and calibrating feature points along the splicing seam of the target splicing block to determine a second coordinate value of each feature point of the target splicing block in the calibration plate coordinate system, and transforming the second coordinate value into a processing site coordinate system using the second transformation matrix;

[0012] The laser profiler is used to collect characteristic points of the joint seam on the target joint block to obtain the third coordinate value in the laser profiler coordinate system;

[0013] Point set matching is performed based on the second coordinate value and the third coordinate value in the machining site coordinate system by using a singular value decomposition method to construct a third transformation matrix between the laser profiler coordinate system and the machining site coordinate system.

[0014] The present invention uses the target ball seat and the splicing block on the calibration plate to establish a conversion relationship between the laser profiler coordinate system in the current processing site and the processing site coordinate system, effectively improving the accuracy of data acquisition, thereby solving the problems of poor positioning accuracy of the robot-carried laser profiler and the inability of the laser tracker to measure complex surfaces, large-area surfaces and gaps.

[0015] Specifically, the feature points are obtained by extracting vertices at turning points of the seams on the target splicing block.

[0016] Specifically, four target ball seats are arranged in an array on the calibration plate, and the center point of a closed area formed by connecting the four target ball seats is used as the base point of the calibration plate coordinate system.

[0017] Specifically, the first transformation matrix, the second transformation matrix and the third transformation matrix all include a rotation matrix and a translation matrix.

[0018] Specifically, a projection point of the center point of the target splicing block projected onto the calibration plate coincides with a base point in the calibration plate coordinate system.

[0019] Specifically, the conversion formula between the two coordinate systems is as follows: ;in, represents the rotation matrix in the transformation matrix, and Indicates the coordinate values ​​of the same point in two coordinate systems.

[0020] Specifically, it also includes a calibration process of the third transformation matrix. The calibration process is to rotate the calibration plate by a predetermined angle in a fixed direction, re-collect the feature points of the current target splicing block through the laser profiler, and generate the corresponding first correction matrix with the re-collected feature points. The third transformation matrix before rotation is compared with the generated first correction matrix. If the two are inconsistent, it is necessary to rotate the predetermined angle again and repeat the operation. The second correction matrix obtained after the second rotation is used. If the second correction matrix is ​​consistent with the third transformation matrix before rotation, no correction processing is performed. If the second correction matrix is ​​consistent with the first correction matrix, the first correction matrix or the second correction matrix is ​​output as the corrected third transformation matrix.

[0021] In order to achieve the second object of the present invention, the following technical solution is provided: a multi-position splicing measurement and calibration device, comprising:

[0022] The robot system includes a fixed base, a multi-degree-of-freedom robotic arm provided on the fixed base, and a motion controller, wherein the end of the multi-degree-of-freedom robotic arm is provided with a line laser profiler interface;

[0023] A line laser profiler, used to collect profile data of the surface of the splicing block, which is fixed to the end effector of the robot and is used to emit a linear laser beam and receive reflected light;

[0024] The calibration plate comprises a base plate, a target ball seat and a splicing block arranged on the base plate;

[0025] The laser tracker is used to collect the position coordinate information of the target ball seat. It is placed at the processing site to emit a point laser beam and receive reflected light.

[0026] Specifically, the splicing blocks are triangular splicing blocks with base angles of 60°. The base of the triangular splicing blocks is parallel to two sides of the calibration plate, and the other two sides are perpendicular.

[0027] Specifically, the triangular splicing block is arranged at the center of the square flat plate, and is fixed to the square flat plate with the end surface where the bottom edge of the triangular splicing block is located serving as a fixing surface.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] A simple calibration plate can be used to realize the conversion between the coordinate system of the line laser profiler and the coordinate system of the laser tracker, which facilitates the data stitching of multiple positions; unlike the traditional hand-eye calibration method, it avoids the error caused by the six degrees of freedom of the robot and greatly improves the accuracy; no external detection equipment is required for auxiliary measurement; it provides a new measurement method for stitching laser profiler measurement data in large-scale measurement fields and realizing the measurement of large-scale flatness, roundness and verticality parameters based on the line laser profiler, which has engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flowchart of the multi-position stitching measurement and calibration method based on laser tracker guidance provided in this embodiment;

[0031] Figure 2 A schematic diagram of the calibration plate provided in this embodiment;

[0032] Figure 3 A schematic diagram of the multi-position splicing measurement and calibration device provided in this embodiment;

[0033] In the figure, 1. Line laser profiler; 2. Laser tracker; 3. Calibration plate; 4. Line laser profiler coordinate system; 5. Calibration plate coordinate system; 6. Laser tracker coordinate system. DETAILED DESCRIPTION

[0034] 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 components of the embodiments of the present invention generally described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] like Figure 1 As shown in FIG, a multi-position stitching measurement and calibration method based on laser tracker guidance provided in this embodiment includes the following steps:

[0036] The laser tracker measures the ERS points on site and makes the tracker measurement coordinate system consistent with the site coordinate system through station transfer calculation, mainly to provide a larger coverage, higher accuracy and more complete data during the measurement process.

[0037] The laser tracker measures the four target spheres on the calibration plate and obtains the coordinates of the center points of the four target spheres in the on-site coordinate system (hereinafter referred to as target sphere points). The coordinates are matched with the theoretical coordinate values ​​of the center points of the four target spheres (i.e., the coordinate values ​​of the four target sphere points in the calibration plate coordinate system) by the singular value decomposition (SVD) method to obtain the rotation matrix r and translation matrix t from the calibration plate coordinate system to the on-site coordinate system. The coordinates of the three feature points in the calibration plate coordinate system are converted to the on-site coordinate system through the rotation matrix r and the translation matrix t. The point set matching is and By using the singular value decomposition (SVD) method, the rotation matrix r and translation matrix t from the calibration plate coordinate system to the field coordinate system are obtained, that is, , the data of the three feature points in the field coordinate system are recorded as , the coordinate value in the calibration plate coordinate system is recorded as , then the formula , to obtain .

[0038] like Figure 2 As shown in the figure, the calibration plate mainly consists of two parts. The first part is a square surface with through holes at the four corners for installing the target seat and the target ball, and the center of the target ball is the target ball point to be measured; the second part is a square surface with two identical triangular blocks tightly spliced ​​together in the center, and the three vertices of the tightly spliced ​​blocks are feature points; the calibration plate as a whole is centrally symmetrical, and the splicing blocks selected in this embodiment are triangular splicing blocks with a base angle of 60°.

[0039] Keeping the calibration plate in position, the robot is guided by the position of the target ball measured by the tracker. The robot clamps the line laser profiler, aligns the line laser with the three feature points of the triangular splicing block, and extracts the coordinate values ​​of the feature points in the line laser profiler coordinate system.

[0040] The singular value decomposition (SVD) method is used to perform point set matching on the coordinates of the three feature points in the line laser profiler coordinate system and the coordinates of the three feature points in the field coordinate system. The rotation matrix R and translation matrix T from the line laser profiler coordinate system to the field coordinate system can be obtained.

[0041] In addition, the measurement and calibration process also includes an inspection process, that is, the calibration plate is rotated around the center of gravity by a certain angle, the line laser profiler is aligned with the gap, and the data of the three feature points are scanned. The coordinates of the three feature points in the laser tracker coordinate system are obtained through the posture transformation matrices R and T obtained above, and compared with the coordinates of the three feature points obtained by inversely measuring the target sphere point with the laser tracker, so as to perform a calibration inspection.

[0042] This embodiment also provides a multi-position splicing measurement calibration device, such as Figure 3 Shown, including:

[0043] The robot system includes a fixed base, a multi-degree-of-freedom robotic arm provided on the fixed base, and a motion controller, wherein the end of the multi-degree-of-freedom robotic arm is provided with a line laser profiler interface;

[0044] A line laser profiler 1 is used to collect profile data of the surface of the splicing block. It is fixed to the end effector of the robot and is used to emit a linear laser beam and receive reflected light. The collected profile data is located in the line laser profiler coordinate system 4;

[0045] The calibration plate 3 includes a base plate, a target ball seat and a splicing block arranged on the base plate, and the objects on the base plate are all in the calibration plate coordinate system 5;

[0046] The laser tracker 2 is used to collect the position coordinate information of the target ball seat and is placed at the processing site to emit a point laser beam and receive reflected light. The collected position coordinate information is located in the laser tracker coordinate system 6.

[0047] More specifically, the robot is guided by the position of the target ball measured by the laser tracker 2 , and the robot clamps the line laser profiler 1 , aligning the line laser with the three feature points of the triangular splicing block, and extracting the coordinate values ​​of the feature points in the line laser profiler coordinate system 4 .

[0048] The line laser profiler 1 is installed at the end of the robot flange, so that the robot can carry the line laser profiler 1 to align the tight splicing position of the triangular splicing blocks to ensure that the laser line and the splicing seam gap coincide.

[0049] The scanning data of the line laser profiler 1 needs to be processed. It is necessary to perform straight line fitting on the point cloud data and extract feature points, that is, to find the three intersection points corresponding to the connection of four continuous straight lines. The point set is recorded as .

[0050] The singular value decomposition (SVD) method is used to match the coordinates of the three feature points in the line laser profiler coordinate system 4 with the coordinates of the three feature points in the field coordinate system, that is, and By performing point set matching, the rotation matrix R and translation matrix T can be obtained, which are used to realize the conversion between the line laser profiler coordinate system and the field coordinate system. After measuring multiple positions, the data converted to the field coordinate system can be spliced.

[0051] In the inspection step, based on the design of the calibration plate triangle block, it can be rotated around the center of gravity by a certain angle. The line laser profiler 1 is aligned with the gap and scanned to obtain the data of the three feature points. The coordinates of the three feature points in the laser tracker coordinate system 6 are obtained through the posture transformation matrices R and T obtained above. They are compared with the coordinates of the three feature points obtained by inversely measuring the target sphere point with the laser tracker 2 to perform a calibration inspection.

[0052] In addition, the terms "upper", "lower", "inner", "outer", "front", and "back" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. Unless otherwise specifically stated, the relative steps, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the present invention.

[0053] Of course, the above description is only a specific embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. Any equivalent changes or modifications made based on the structure, features and principles described in the scope of the patent application of the present invention should be included in the scope of the patent application of the present invention.

[0054] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A multi-position stitching measurement and calibration method based on laser tracker guidance, characterized in that: The following steps are involved: Constructing a first transformation matrix for converting between a laser tracker measurement coordinate system and a machining site coordinate system based on the ERS points at the machining site; Four target spheres are set on the selected calibration plate and the center point coordinates of each target sphere are obtained by measuring with a laser tracker, and the first coordinate value corresponding to each target sphere in the machining site coordinate system is generated using a first transformation matrix; A calibration plate coordinate system is constructed with a point on the calibration plate as the base point, and the theoretical coordinate values ​​of each target ball on the calibration plate coordinate system are obtained; Based on the first coordinate value and the theoretical coordinate value, point set matching is performed by using a singular value decomposition method to construct a second transformation matrix between the calibration plate coordinate system and the processing site coordinate system; Placing a target splicing block on the calibration plate, and calibrating feature points along the splicing seam of the target splicing block to determine a second coordinate value of each feature point of the target splicing block in the calibration plate coordinate system, and transforming the second coordinate value into a processing site coordinate system using the second transformation matrix; The laser profiler is used to collect characteristic points of the joint seam on the target joint block to obtain the third coordinate value in the laser profiler coordinate system; performing point set matching based on the second coordinate value and the third coordinate value in the machining site coordinate system by a singular value decomposition method to construct a third transformation matrix between the laser profiler coordinate system and the machining site coordinate system; It also includes a calibration process for the third transformation matrix, which is to rotate the calibration plate in a fixed direction by a predetermined angle, re-collect the feature points of the current target splicing block through the laser profiler, and generate the corresponding first correction matrix with the re-collected feature points, and compare the third transformation matrix before rotation with the generated first correction matrix. If the two are inconsistent, it is necessary to rotate the predetermined angle again and repeat the operation, and obtain the second correction matrix after the second rotation. If the second correction matrix is ​​consistent with the third transformation matrix before rotation, no correction processing is performed. If the second correction matrix is ​​consistent with the first correction matrix, the first correction matrix or the second correction matrix is ​​output as the corrected third transformation matrix.

2. The multi-position stitching measurement and calibration method based on laser tracker guidance according to claim 1, characterized in that: The feature points are obtained by extracting vertices at turning points of the seams on the target splicing blocks.

3. The multi-position stitching measurement and calibration method based on laser tracker guidance according to claim 1, characterized in that: Four target ball seats are arranged in an array on the calibration plate, and the center point of a closed area formed by connecting the four target ball seats is used as the base point of the calibration plate coordinate system.

4. The multi-position stitching measurement and calibration method based on laser tracker guidance according to claim 1, characterized in that: The first transformation matrix, the second transformation matrix and the third transformation matrix all include a rotation matrix and a translation matrix.

5. The multi-position stitching measurement and calibration method based on laser tracker guidance according to claim 1, characterized in that: The projection point of the center point of the target splicing block on the calibration plate coincides with the base point in the calibration plate coordinate system.

6. The multi-position stitching measurement calibration method based on laser tracker guidance according to claim 1, characterized in that: The conversion formula between the two coordinate systems is as follows: ;in, r represents the rotation matrix in the transformation matrix, t Represents the translation matrix in the transformation matrix, P 1 and P 2 To represent the coordinate values ​​of the same point in two coordinate systems.

7. A multi-position splicing measurement and calibration device, characterized in that: The steps for performing the multi-position stitching measurement calibration based on laser tracker guidance according to any one of claims 1 to 6 include: The robot system includes a fixed base, a multi-degree-of-freedom robotic arm provided on the fixed base, and a motion controller, wherein the end of the multi-degree-of-freedom robotic arm is provided with a line laser profiler interface; Line laser profiler, used to collect profile data of the surface of the spliced ​​blocks; The calibration plate comprises a base plate, a target ball seat and a splicing block arranged on the base plate; Laser tracker, used to collect the position coordinate information of the target sphere.

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