JP-7856795-B2 - Calibration method, apparatus, electronic equipment, and computer-readable storage medium for external parameters of a linear shape measuring machine.

Inventors

• 龍 学雄
• 常 旭
• ▲デン▼ 志輝

Assignees

• 杭州海康机器人股▲ふん▼有限公司

Dates

Publication Date

20260511

Application Date

20230524

Priority Date

20220526

Claims (15)

1. A method for calibrating the external parameters of a linear shape measuring machine , performed by a calibration device , During the movement of the calibration block on the measuring stand, a contour point cloud of multiple frames collected from the calibration block by a linear shape measuring machine is obtained. Point cloud segmentation is performed on each contour point cloud to obtain surface point clouds belonging to different measurement surfaces. For each surface point group, a constraint relationship is constructed based on each feature point in the surface point group and the surface features of the measurement surface to which the surface point group belongs, wherein the surface features of each measurement surface are features that indicate the geometric attributes of the measurement surface. Based on the inferred transformation relationship between the linear shape measuring machine coordinate system and the measuring table coordinate system, and the constraint relationship of each surface point cloud, a target optimization function is constructed for the said inferred transformation relationship. The method is characterized by including optimizing the target optimization function and using the optimized transformation parameters between the linear shape measuring machine coordinate system and the measuring table coordinate system as external parameters between the linear shape measuring machine and the measuring table. Calibration method for external parameters of a linear shape measuring machine.
2. Performing point cloud division on each of the aforementioned contour point groups to obtain surface point groups belonging to different measurement surfaces is, The method is characterized by including, for each contour point cloud, performing point cloud division based on a division policy corresponding to the type of calibration block, to obtain surface point clouds belonging to different measurement surfaces. A method for calibrating the external parameters of a linear shape measuring machine according to claim 1.
3. Based on the division policy corresponding to the type of calibration block, point cloud division is performed on the contour point cloud to obtain surface point clouds belonging to different measurement surfaces. If the calibration block is a cone, curve fitting and linear fitting are performed on each feature point in the contour point cloud, and the feature points corresponding to the curves obtained by fitting are determined as the conical surface point cloud, and the feature points corresponding to the linear lines obtained by fitting are determined as the base surface point cloud. If the calibration block is a sphere, circular fitting and linear fitting are performed on each feature point in the contour point cloud, the feature points corresponding to the curves obtained by fitting are made into a spherical point cloud, and the feature points corresponding to the straight lines obtained by fitting are made into a base point cloud. If the calibration block is a frustum, the method includes performing linear fitting on each feature point in the contour point cloud to obtain multiple fitting lines, dividing the multiple fitting lines into endpoint lines including the endpoints and midpoint lines not including the endpoints, forming the upper point cloud with the feature points corresponding to the midpoint lines and the lower point cloud with the feature points corresponding to the endpoint lines. A method for calibrating the external parameters of a linear shape measuring machine according to claim 2.
4. Before constructing a target optimization function for the inferred transformation relationship based on the inferred transformation relationship between the linear shape measuring machine coordinate system and the measuring table coordinate system, and the constraint relationship of each surface point cloud, the calibration method for the external parameters of the linear shape measuring machine is as follows: The method further includes determining the coordinate system transformation relationship between the linear shape measuring machine coordinate system and the measuring table coordinate system as an inferred transformation relationship based on the contour point cloud of multiple frames obtained, A method for calibrating the external parameters of a linear shape measuring machine according to any one of claims 1 to 3.
5. Based on the contour point cloud of the multiple frames obtained, determining the coordinate system transformation relationship between the linear shape measuring machine coordinate system and the measuring table coordinate system as an inferred transformation relationship is: Based on the contour point cloud of the multiple frames, the initial transformation parameters between the linear shape measuring machine coordinate system and the measuring table coordinate system are determined. The method is characterized by obtaining an estimated transformation relationship by using the initial transformation parameters as estimated values for each parameter in the transformation equation between the linear shape measuring machine coordinate system and the measuring table coordinate system. A method for calibrating the external parameters of a linear shape measuring machine according to claim 4.
6. The aforementioned initial transformation parameters include initial rotation parameters, Determining the initial transformation parameters between the linear shape measuring machine coordinate system and the measuring table coordinate system based on the contour point cloud of the multiple frames is: The inclination of the fitting line corresponding to each bottom feature point in the contour point cloud of the plurality of frames is determined, and the first rotation angle of the linear shape measuring machine coordinate system relative to the measuring table coordinate system is determined based on the inclination, wherein the bottom feature point is a feature point belonging to the measuring table, The feature point with the maximum height in the contour point cloud of the multiple frames is determined as the maximum feature point, the ratio of the height of the maximum feature point to the actual height of the calibration block is calculated, and the second rotation angle of the linear shape measuring machine coordinate system relative to the measurement table coordinate system is determined based on this ratio. The method is characterized by including determining the initial rotation parameters based on the first rotation angle and the second rotation angle, A method for calibrating the external parameters of a linear shape measuring machine according to claim 5.
7. The aforementioned initial transformation parameters include initial translation parameters, Determining the initial transformation parameters between the linear shape measuring machine coordinate system and the measuring table coordinate system based on the contour point cloud of the multiple frames is: For any two adjacent frame contour point clouds, this includes determining a first height difference of the feature point with the maximum height in the contour point clouds of the two frames; determining the curved arc length corresponding to the first height difference and the horizontal displacement within each sampling interval of the calibration block based on the surface features of the calibration block; determining a first displacement in a first direction of the linear shape measuring machine coordinate system relative to the measuring table coordinate system based on the curved arc length and the horizontal displacement; determining a second displacement in a second direction of the linear shape measuring machine coordinate system relative to the measuring table coordinate system based on the curved arc length and the first height difference, wherein the first and second directions are orthogonal; and determining the initial translation parameter based on the first and second displacements, or When the calibration block is a frustum, the method includes determining the transverse coordinate of a designated point on the frustum as a third displacement based on the contour point cloud of each frame, wherein the designated point is any point on the frustum; determining the height of the frustum as a fourth displacement based on the surface point cloud belonging to the apex of the frustum and the base point cloud belonging to the measuring platform; and determining the initial translation parameter based on the third and fourth displacements. A method for calibrating the external parameters of a linear shape measuring machine according to claim 5.
8. Optimizing the aforementioned target optimization function and obtaining the optimized transformation parameters between the linear shape measuring machine coordinate system and the measuring table coordinate system as external parameters between the linear shape measuring machine and the measuring table is, The transformation parameters in the target optimization function are iteratively optimized until the residuals of the target optimization function become smaller than a preset threshold. The present invention is characterized in that, when the residual of the target optimization function is smaller than a preset threshold, the transformation parameter in the target optimization function is set to an external parameter between the linear shape measuring machine and the measuring stand. A method for calibrating the external parameters of a linear shape measuring machine according to any one of claims 1 to 3.
9. A point cloud acquisition module that obtains contour point clouds of multiple frames collected on the calibration block by a linear shape measuring machine while the calibration block is being moved on a measuring stand, A point cloud division module that performs point cloud division on each contour point cloud to obtain surface point clouds belonging to different measurement surfaces, For each surface point group, a relation building module is used to construct constraint relationships for that surface point group based on each feature point in that surface point group and the surface features of the measurement surface to which the surface point group belongs, wherein the surface features of each measurement surface are features that indicate the geometric attributes of that measurement surface , A function construction module constructs a target optimization function for the inferred transformation relationship between the linear shape measuring machine coordinate system and the measuring table coordinate system, based on the constraint relationship of each surface point cloud, The system includes a function optimization module that optimizes the target optimization function and uses the optimized transformation parameters between the linear shape measuring machine coordinate system and the measuring table coordinate system as external parameters between the linear shape measuring machine and the measuring table. Calibration device for external parameters of a linear shape measuring machine.
10. The point cloud division module is characterized in that, for each contour point cloud, it is used to perform point cloud division on the contour point cloud based on a division policy corresponding to the type of calibration block, and to obtain surface point clouds belonging to different measurement surfaces. Calibration device for external parameters of a linear shape measuring machine according to claim 9.
11. The point cloud division module is characterized in that, when the calibration block is a cone, it performs curve fitting and linear fitting on each feature point in the contour point cloud, determining each feature point corresponding to the fitted curve as a conical surface point cloud and each feature point corresponding to the fitted linear as a base point cloud; when the calibration block is a sphere, it performs circular fitting and linear fitting on each feature point in the contour point cloud, determining each feature point corresponding to the fitted curve as a spherical point cloud and each feature point corresponding to the fitted linear as a base point cloud; when the calibration block is a frustum, it performs linear fitting on each feature point in the contour point cloud to obtain multiple fitting lines, and divides the multiple fitting lines into endpoint lines including the endpoints and midpoint lines not including the endpoints, determining each feature point corresponding to the midpoint lines as an upper point cloud and each feature point corresponding to the endpoint lines as a base point cloud. Calibration device for external parameters of a linear shape measuring machine according to claim 10.
12. The function construction module further includes a relationship estimation module that, before constructing a target optimization function for the estimated transformation relationship based on the estimated transformation relationship between the linear shape measuring machine coordinate system and the measuring table coordinate system and the constraint relationship of each surface point cloud, determines the coordinate system transformation relationship between the linear shape measuring machine coordinate system and the measuring table coordinate system as an estimated transformation relationship based on the contour point clouds of multiple frames obtained, Calibration device for external parameters of a linear shape measuring machine according to any one of claims 9 to 11.
13. The relationship estimation module is characterized by being used to determine initial transformation parameters between the linear shape measuring machine coordinate system and the measuring table coordinate system based on the contour point cloud of the multiple frames, and to obtain an estimated transformation relationship by using the initial transformation parameters as estimated values for each parameter in the transformation formula between the linear shape measuring machine coordinate system and the measuring table coordinate system. Calibration device for external parameters of a linear shape measuring machine according to claim 12.
14. An electronic device comprising a processor, a communication interface, memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus. Memory is used to store computer programs. The processor is characterized in that, upon executing a program stored in memory, it is used to realize the steps of the calibration method for external parameters of a linear shape measuring machine described in any one of claims 1 to 3. electronic equipment.
15. The processor stores a computer program that, when executed, implements the steps of the calibration method for external parameters of a linear shape measuring machine according to any one of claims 1 to 3. Computer-readable storage medium.

Description

(Cross-reference of related applications) This application claims priority based on the Chinese patent application filed with the State Intellectual Property Administration of China on May 26, 2022, application number 202210582401.7, with the title of invention "Method, apparatus and electronic device for calibrating external parameters of a linear shape measuring machine." All of the contents of the present application are incorporated herein by reference. This application relates to the field of measurement technology, and more particularly to a calibration method, apparatus, and electronic equipment for the external parameters of a linear shape measuring machine. A linear shape measuring machine is a precision instrument used to measure the contour line shape and cross-sectional contour shape of various machine parts. Generally, when measuring an object with a linear shape measuring machine, the object is placed on a measuring platform. The platform can usually be moved by rotation or translation, and the linear shape measuring machine continuously collects contour point clouds of the object as it moves. Based on these collected contour point clouds, the contour information of the object is determined. In the process described above, it is necessary to determine the contour information of the object to be measured using the contour point cloud collected by the linear shape measuring machine. Since the process of determining the contour information of the object to be measured requires the use of external parameters between the linear shape measuring machine and the measuring table, it is necessary to calibrate these external parameters before determining the contour information. Therefore, how to calibrate the external parameters between the linear shape measuring machine and the measuring table is an urgent technical challenge that needs to be resolved. This embodiment aims to provide a method, apparatus, and electronic device for calibrating the external parameters of a linear shape measuring machine. The specific technical proposal is as follows: In a first embodiment, the present invention provides a calibration method for the external parameters of a linear shape measuring machine. This calibration method includes: obtaining a contour point cloud of multiple frames collected from the calibration block by the linear shape measuring machine while the calibration block is moving on the measuring stand; performing point cloud division on each contour point cloud to obtain surface point clouds belonging to different measuring surfaces; constructing a constraint relationship for each surface point cloud based on each feature point in the surface point cloud and the surface features of the measuring surface to which the surface point cloud belongs, wherein the surface features of each measuring surface are features indicating the geometric attributes of the measuring surface; constructing a target optimization function for the inferred transformation relationship based on the inferred transformation relationship between the linear shape measuring machine coordinate system and the measuring stand coordinate system and the constraint relationship of each surface point cloud; optimizing the target optimization function and obtaining the optimized transformation parameters between the linear shape measuring machine coordinate system and the measuring stand coordinate system as external parameters between the linear shape measuring machine and the measuring stand. Preferably, performing point cloud division on each contour point group to obtain surface point groups belonging to different measurement surfaces includes performing point cloud division on each contour point group based on a division policy corresponding to the type of calibration block, thereby obtaining surface point groups belonging to different measurement surfaces. Preferably, performing point cloud division on the contour point cloud based on a division policy corresponding to the type of calibration block to obtain surface point clouds belonging to different measurement surfaces includes, if the calibration block is conical, performing curve fitting and linear fitting on each feature point in the contour point cloud, defining each feature point corresponding to the fitted curve as a conical surface point cloud, and defining the feature points corresponding to the fitted linear as a base surface point cloud; and if the calibration block is spherical, performing circular fitting and linear fitting on each feature point in the contour point cloud, defining each feature point corresponding to the fitted curve as a spherical point cloud, and defining each feature point corresponding to the fitted linear as a base surface point cloud. Preferably, before constructing a target optimization function for the inferred transformation relationship between the linear shape measuring machine coordinate system and the measuring table coordinate system, based