High-gradient free-form surface measurement and evaluation method and system based on coordinate measurement

Abstract

The invention discloses a coordinate measurement-based high-gradient free-form surface measurement and evaluation method and system. The coordinate measurement-based high-gradient free-form surface measurement and evaluation method comprises the following steps of: dividing a to-be-measured curved surface of an element into a plurality of sub-surface patches with overlapped regions according to surface shape characteristics of the element; searching an optimal measurement point and a measurement path on the curved surface to be measured; adjusting the pose of the coordinate measuring machine by using a pose adjusting mechanism, and sequentially measuring the surface shape of each sub-surface patch through the coordinate measuring machine according to the optimal measuring point and the measuring path; and matching and splicing the overlapped areas of the surface shapes of the adjacent sub-surface patches to obtain a complete surface shape of the to-be-measured curved surface for surface shape precision evaluation of the to-be-measured curved surface. The invention aims to improve the detection precision of the optical element so as to improve the manufacturing precision of an optical system and improve the imaging quality of the optical system, and can be widely applied to the design and manufacturing of a next-generation optical system.

Description

Technical Field

[0001] The present invention relates to ultra-precision measurement technology, and in particular to a method and system for measuring and evaluating a high-steepness (maximum angle of the surface is greater than 30 degrees) free-form surface based on coordinate measurement. Background Art

[0002] Precision physics experiments involve a large number of experimental samples (such as experimental samples for studying material surface / interface characteristics, etc.) and devices (such as high energy density physics experimental devices, etc.). These samples and devices put forward urgent demands and extreme index requirements for manufacturing technology, which are mainly manifested in the extremely special application environment, extremely complex material characteristics, extremely demanding manufacturing quality, and extremely large manufacturing scale. Focusing on the extreme manufacturing needs of precision physics experiments for complex curved surface parts of difficult-to-process metal materials such as tungsten alloys and titanium alloys, and the current problems of difficult-to-process metal materials such as tungsten alloys and titanium alloys in manufacturing accuracy and surface quality control, the detection and evaluation methods of geometric accuracy of complex curved surfaces with high steepness (maximum angle of the surface is greater than 30 degrees) are studied. The high steepness, curvature mutation characteristics and high precision requirements of the experimental surface put forward extremely high requirements for its surface detection and evaluation. High steepness and curvature mutation surfaces exceed the dynamic range and achievable space limit of the measuring instrument, and high precision puts forward extremely demanding uncertainty control requirements for the measuring equipment and methods. Summary of the invention

[0003] Technical problem to be solved by the present invention: In view of the above-mentioned problems in the prior art, a method and system for measuring and evaluating high-steepness free-form surfaces based on coordinate measurement are provided. The present invention aims to improve the detection accuracy of optical elements for improving the manufacturing accuracy of optical systems and improving the imaging quality of optical systems, and can be widely used in the design and manufacture of next-generation optical systems.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for measuring and evaluating a high-steepness free-form surface based on coordinate measurement comprises the following steps: S101, dividing the surface to be measured of the component into a plurality of sub-surface patches with overlapping areas according to the surface features of the component; S102, finding the optimal measuring point and measuring path on the surface to be measured; S103, using a posture adjustment mechanism to adjust the posture of a coordinate measuring machine, and using the coordinate measuring machine to sequentially measure the surface shape of each sub-face patch according to an optimal measurement point and a measurement path; S104, matching and splicing the overlapping areas of the surface shapes of adjacent sub-patches to obtain a complete surface shape of the surface to be measured for use in surface shape accuracy evaluation of the surface to be measured.

[0005] Optionally, step S101 includes: if the surface shape of the component is a regular surface, the uniform area allocation principle is adopted to divide the surface to be measured of the component into multiple sub-patches with overlapping areas, and the maximum relative angle of each sub-patch does not exceed a preset angle; otherwise, the characteristic structure center of the component is determined, and the surface to be measured of the component is divided into multiple sub-patches with overlapping areas with the characteristic structure center as the center, and the maximum relative angle of each sub-patch does not exceed a preset angle.

[0006] Optionally, when the curved surface to be measured of the component is divided into a plurality of sub-surface patches with overlapping areas, the size of the overlapping area between adjacent sub-surface patches is between 10% and 20%.

[0007] Optionally, the function expression for finding the optimal measuring point on the surface to be measured in step S102 is: , In the above formula, For the i The optimal measurement point, for The grid curvature measure of is the jth optimal measurement point, is the measuring point, and: , , In the above formula, is the curvature measure of the measuring point, is the contrast adjustment parameter of the measurement point distribution grid, For location The curvature value of and are the minimum and maximum curvature values ​​of the surface to be measured, respectively. The surface to be measured is S={ x , y , z ( x , y )},in x , y , z ( x , y ) are the x, y and z axis coordinates respectively, z x is the partial derivative in the x direction, z y is the partial derivative in the y direction, z xx is the partial derivative of the X plane, z xy is the partial derivative on the Y plane.

[0008] Optionally, finding the optimal measurement path on the surface to be measured in step S102 refers to finding the optimal measurement path on the surface to be measured using an ant colony algorithm, and the objective function used in finding the optimal measurement path on the surface to be measured using the ant colony algorithm is that the total length of all paths in the grid on the surface to be measured is the shortest, and the calculation function expression of the total length of all paths is: , In the above formula, is the total length of all paths, w is the arrangement between grids; For grid i l-1 i l The distance between.

[0009] Optionally, step S104 includes: S301, converting the surface shape of each sub-facet from the local coordinates of the sub-facet to a unified global coordinate system; S302, determine any adjacent sub-facets according to the following formula and The deviation of the directed distance between the overlapping point pairs and the nominal surface in the overlapping area : , In the above formula, is the coordinate of the overlapping area of ​​sub-patch j and sub-patch k on the nominal surface, is the projection point of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface, is the number of projection points of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface, , is the total number of measurement points in the overlapping area, is the coordinate of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface; S303: based on the directed distance deviation from the overlapping point pairs in the overlapping area to the nominal surface Based on the minimum principle, the following sub-facet synchronous stitching least squares model is established: , In the above formula, is the objective function, is the total number of overlapping point pairs, is the number of sub-patches; S304, by minimizing the objective function defined in the above formula, solving the optimal configuration parameters Thus, the complete shape of the surface to be measured is obtained.

[0010] Optionally, after step S104, the method further includes: using a wavefront interferometer to measure and obtain the surface shape of the surface to be measured, and verifying the complete surface shape of the surface to be measured obtained by splicing according to the surface shape of the surface to be measured obtained by the wavefront interferometer.

[0011] In addition, the present invention also provides a high-steepness free-form surface measurement and evaluation system based on coordinate measurement, including an interconnected microprocessor and a memory, wherein the microprocessor is programmed or configured to execute the high-steepness free-form surface measurement and evaluation method based on coordinate measurement.

[0012] In addition, the present invention also provides a computer-readable storage medium, in which a computer program / instruction is stored. The computer program / instruction is programmed or configured to execute the high-steepness free-form surface measurement and evaluation method based on coordinate measurement through a processor.

[0013] In addition, the present invention also provides a computer program product, including a computer program / instruction, which is programmed or configured to execute the high-steepness free-form surface measurement and evaluation method based on coordinate measurement through a processor.

[0014] Compared with the prior art, the present invention mainly has the following advantages: the high-steepness free-form surface measurement and evaluation method based on coordinate measurement of the present invention comprises dividing the surface to be measured of the component into a plurality of sub-surface patches with overlapping areas according to the surface shape features of the component; finding the optimal measurement point and measurement path on the surface to be measured; using a posture adjustment mechanism to adjust the posture of the coordinate measuring machine, and using the coordinate measuring machine to measure the surface shape of each sub-surface patch in turn according to the optimal measurement point and measurement path; matching and splicing the overlapping areas of the surface shapes of adjacent sub-surface patches to obtain the complete surface shape of the surface to be measured. The present invention can be used for high-precision measurement of high-steepness optical components and other optical components with complex surface shapes, solves the problem that high-steepness components cannot be measured or measured accurately in a coordinate measuring machine environment, can improve the detection accuracy of optical components to improve the manufacturing accuracy of optical systems and improve the imaging quality of optical systems, and can be widely used in the design and manufacture of next-generation optical systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the basic flow of the method of the embodiment of the present invention.

[0016] Figure 2 Schematic diagram of the basic process of the ant colony algorithm used in the embodiment of the present invention.

[0017] Figure 3 The diagram is a schematic diagram of an optimal measurement path obtained by using the ant colony algorithm in an embodiment of the present invention.

[0018] Figure 4 Schematic diagram of the principle of sub-patch measurement in an embodiment of the present invention.

[0019] Figure 5 Schematic diagram of the principle of the point cloud data matching process in an embodiment of the present invention.

[0020] Figure 6 Schematic diagram of two-dimensional calculation of overlapping point pair matching in an embodiment of the present invention.

[0021] Figure 7 This is the complete surface shape of the curved surface to be measured obtained in the embodiment of the present invention.

[0022] Figure 8 This is the measurement result of the Zygo spherical interferometer in the embodiment of the present invention.

[0023] Fig. 9 It is the full-aperture three-coordinate measurement result in the embodiment of the present invention. DETAILED DESCRIPTION

[0024] like Figure 1 As shown, the high-steepness free-form surface measurement and evaluation method based on coordinate measurement in this embodiment includes the following steps: S101, dividing the surface to be measured of the component into a plurality of sub-surface patches with overlapping areas according to the surface features of the component; S102, finding the optimal measuring point and measuring path on the surface to be measured; S103, using a posture adjustment mechanism to adjust the posture of a coordinate measuring machine, and using the coordinate measuring machine to sequentially measure the surface shape of each sub-face patch according to an optimal measurement point and a measurement path; S104, matching and splicing the overlapping areas of the surface shapes of adjacent sub-patches to obtain a complete surface shape of the surface to be measured for use in surface shape accuracy evaluation of the surface to be measured.

[0025] In this embodiment, step S101 includes: if the surface shape of the component is a regular surface, the uniform area allocation principle is adopted to divide the surface to be measured of the component into multiple sub-surface patches with overlapping areas, and the maximum relative angle of each sub-surface patch does not exceed the preset angle; otherwise, the characteristic structure center of the component is determined, and the surface to be measured of the component is divided into multiple sub-surface patches with overlapping areas with the characteristic structure center as the center, and the maximum relative angle of each sub-surface patch does not exceed the preset angle. As an optional implementation, in this embodiment, when the surface to be measured of the component is divided into multiple sub-surface patches with overlapping areas, the size of the overlapping area between adjacent sub-surface patches is between 10% and 20%.

[0026] In step S102 of this embodiment, the function expression for finding the optimal measuring point on the surface to be measured is: , In the above formula, For the iThe optimal measurement point, for The grid curvature measure of is the jth optimal measurement point, is the measuring point, and: , , In the above formula, is the curvature measure of the measuring point, is the contrast adjustment parameter of the measurement point distribution grid, For location The curvature value of and are the minimum and maximum curvature values ​​of the surface to be measured, respectively. The surface to be measured is S={ x , y , z ( x , y )},in x , y , z ( x , y ) are the x, y and z axis coordinates respectively, z x is the partial derivative in the x direction, z y is the partial derivative in the y direction, z xx is the partial derivative of the X plane, z xy is the partial derivative on the Y plane.

[0027] In step S102, the optimal measurement path on the surface to be measured is sought with the goal of reducing the measurement time. The required intelligent optimization algorithm may be adopted as needed, for example, an ant colony algorithm, simulated annealing and other intelligent optimization algorithms. As an optional implementation, in step S102 of this embodiment, the optimal measurement path on the surface to be measured is sought by using an ant colony algorithm to find the optimal measurement path on the surface to be measured, and the objective function used by the ant colony algorithm to find the optimal measurement path on the surface to be measured is that the total length of all paths in the grid on the surface to be measured is the shortest, and the calculation function expression of the total length of all paths is: , In the above formula, is the total length of all paths, w is the arrangement between grids; For grid i l-1 i l The distance between.

[0028] The ant colony algorithm is a well-known optimization algorithm. It is used to simulate the behavior of ants, rely on pheromones to find the shortest path, and quickly adapt to environmental changes. The ant colony algorithm imitates the self-organizing behavior of ants in their march, can quickly find a better solution in the early stage of optimization, and has a good optimization effect in solving path optimization problems. In the ant colony algorithm, each ant will choose a path to search based on the information around it and its own experience. The measurement path generation of the initial solution is the process of generating the initial solution in this way. Specifically, it includes the following steps: Initialization: Set an initial solution and place all ants at the starting point. Path selection: Each ant chooses a path to search based on the information and experience around it. When selecting a path, ants will choose based on factors such as pheromone concentration and path length. Update pheromone: When all ants have selected a path, update the pheromone concentration based on the path length. Generally, paths with shorter path lengths will be subject to higher pheromone concentrations, making them easier to be selected by subsequent ants. Repeat: The above steps will be repeated until a certain stop condition is reached. Such as Figure 2 As shown in the figure, the main process of the ant colony algorithm includes: (1) generating the initial solution path; (2) setting parameter initialization, including the number of iterations n; (3) updating pheromones; (4) using the objective function to evaluate the ant colony; (5) judging whether the termination condition is met. If the termination condition is not met, n is increased by 1, the moving direction is selected according to the probability, and step (3) is skipped; otherwise, the shortest path is output. During initialization, the workpiece is initialized into N grids, the grid coordinates A={i,j|i,j∈N}, and the distance between the grids ( d ij ) n×n , is the pheromone left by the Kth ant on the path from i to j for:

[0029] C K is the total length of the path obtained after the Kth ant walks the entire path. After each iteration, all the ants that have gone out will calculate the route they have taken and update the corresponding pheromone concentration when updating the pheromone. The function expression is:

[0030] In the above formula, m is the number of ants, and ρ is the pheromone evaporation coefficient; is the pheromone concentration before the update. After multiple iterations, the pheromone concentration will accumulate on the better paths, causing more ants to choose these paths. This process gradually guides the ant colony to gather towards the optimal solution. The algorithm usually terminates after reaching a predetermined number of iterations or after no significant improvement within a certain period of time. The termination condition of step (5) is that the number of iterations n is equal to the preset threshold. Finally, the optimal path obtained in this embodiment is as follows Figure 3 As shown, this embodiment can improve measurement efficiency and measurement accuracy by applying the traditional ant colony algorithm to optical surface measurement.

[0031] The posture adjustment mechanism in step S103 is used to convert the high-steepness features of the sub-surface to be measured into conventional low-steepness features for easy measurement. First, based on the gradient features and curvature feature distribution of the high-steepness complex surface, the optimal sub-surface overlap area ratio is analyzed, and the surface to be measured is divided into several sub-surfaces with overlapping areas in combination with constraints such as probe measurability. Figure 4 FIG. 1 is a schematic diagram showing the principle of the sub-surface measurement in this embodiment. Figure 4 When measuring position (a) in Then the workpiece is deflected around the X axis to Figure 4 The measurement position (b) in the sub-patch is then The workpiece is then rotated around the central axis to complete the measurement of all sub-facets evenly distributed on the periphery. Each sub-facet is adjusted to the optimal geometric shape through the adjustment platform so that its steepness at each location in the coordinate system of the measuring machine is small enough to meet the measurement accuracy requirements. There are overlapping areas between the central sub-facet and the peripheral sub-facets and between the peripheral sub-facets. The principle of unchanged surface shape in the overlapping area can be used to determine the six-degree-of-freedom motion error of the measurement process and compensate for the nominal motion of the sub-facet measurement process. In addition, the measurement data of all sub-facets can be accurately converted to the same coordinate system and spliced ​​to obtain the full-aperture surface shape data of the measured workpiece. By comparing the actually measured surface with the designed surface of the workpiece, the surface shape error of the measured workpiece can be obtained.

[0032] like Figure 5 As shown, for each sub-facet, the posture adjustment mechanism is used to adjust the posture of the coordinate measuring machine in step S103, and the coordinate measuring machine measures the surface data in sequence according to the optimal measurement points and measurement paths to obtain the measured point cloud data, which has a deviation from the theoretical model data of the sub-facet. Step S104 is used to match and optimize the deviation between the measured point cloud data and the theoretical model data of the sub-facet. The surface error distribution and algorithm matching error finally obtained are shown in Figure 5 As shown in the right sub-figure.

[0033] In step S302 of this embodiment, the adjacent sub-faces and The method for obtaining the overlapping area is a well-known method. For details, see the reference: Yang Can. Workpiece self-positioning algorithm and system implementation in magnetorheological polishing [D]. Changsha: National University of Defense Technology, 2015, 9~21. Assume that the measured high-steepness complex surface has s sub-surfaces, where The measurement data is , sub-face The measurement data is ,in , Sub-patches and The total number of measurement points in the sub-face. To sub-patch The workpiece to be measured needs to adjust its position and posture relative to the coordinate measuring machine. and It is in the sub-surface and The key to splicing sub-faces is to transform the local coordinates of each sub-face into a unified global coordinate system.

[0034] , in, is a rigid body transformation, including the nominal transformation and error between the local coordinate system of the sub-face and the global coordinate system, that is, the local coordinate system of the sub-face i The configuration relative to the global coordinate system. It can be represented by elements of the special Euclidean group SE(3), which is common in robot learning. It is related to its Lie algebra SE(3) using exponential mapping: , , in, is the motion spinor, are called spinor coordinates, is a unit vector, whose tth component is 1 and the other components are 0. Since there is motion error in the process of posture transformation, it is necessary to determine the overlapping correspondence of each sub-facet in the global coordinate system and further calculate the deviation in the overlapping area. Since the CAD model of the measured surface is known, it can be used to solve the matching problem of overlapping point pairs. Coordinate sampling measurement points Project onto the nominal surface (CAD model of the measured surface) to generate the corresponding projection point set , and you can get points The distance to the nominal surface is the inner product of the vectors: , in The nominal surface The unit normal vector at .

[0035] like Figure 6 As shown, the sub-face k Coordinate sampling measurement points on The projection point on the nominal surface is . Wakako noodles Points in falls within the overlapping area, then its projection point Projection point on the XY plane Located in the point set Projected convex hull on the XY plane Thus, the matching problem of overlapping point pairs is transformed into a two-dimensional geometric problem. Assuming that the overlapping area is in the sub-face The measured data in is recorded as: , In the sub-patch The measured data is recorded as: , in Corresponding to the overlapping points, Indicates the total number of measurement points in the overlapping area. Represents a sub-patch With sub-patches The overlapping area of ​​the overlapped area on the nominal surface is the same, and the resulting projection point set is From the above formula, we can get the surface patch and The deviation of the directed distance from the overlapping point pair to the nominal surface is: , In the above formula, The coordinates of the overlapping area of ​​sub-patch j and sub-patch k on the nominal surface, is the projection point of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface, is the number of projection points of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface, , is the total number of measurement points in the overlapping area, is the coordinate of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface. Therefore, in this embodiment, step S104 includes: S301, converting the surface shape of each sub-facet from the local coordinates of the sub-facet to a unified global coordinate system. The coordinate conversion is performed by an existing well-known method, so its implementation details are not described in detail here; S302, determine any adjacent sub-facets according to the following formula and The deviation of the directed distance between the overlapping point pairs and the nominal surface in the overlapping area : , In the above formula, is the coordinate of the overlapping area of ​​sub-patch j and sub-patch k on the nominal surface, is the projection point of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface, is the number of projection points of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface, , is the total number of measurement points in the overlapping area, is the coordinate of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface; S303: based on the directed distance deviation from the overlapping point pairs in the overlapping area to the nominal surface Based on the minimum principle, the following sub-facet synchronous stitching least squares model is established: , In the above formula, is the objective function, is the total number of overlapping point pairs, is the number of sub-patches; S304, by minimizing the objective function defined in the above formula as the goal, solving the optimal configuration parameters Thus, the complete shape of the surface to be measured is obtained. In this embodiment, the solution process includes: firstly, initializing the initial configuration parameters , the coordinate data set W and the parameters of the termination condition , initialize the number of iterations l is 0; then in each iteration, according to the l Configuration parameters for iterations Determine l Overlapping point pairs of iterations And calculate the objective function Get the first l The objective function value of the iteration , and according to the end condition Whether it is established determines whether to continue iterating. If the end condition is established, the first l Configuration parameters for iterations As the optimal configuration parameter Output.

[0036] As an optional implementation, after step S104, this embodiment further includes: using a wavefront interferometer to measure and obtain the surface shape of the surface to be measured, and verifying the complete surface shape of the surface to be measured obtained by stitching according to the surface shape of the surface to be measured obtained by the wavefront interferometer. The complete surface shape of the surface to be measured obtained by the method of this embodiment is as follows: Figure 7 As shown in the figure, the measurement results of the zygo spherical interferometer are used as the benchmark, and the full-aperture and slice coordinates are used to measure the same surface error, respectively. Figure 8 and Fig. 9 As shown. Figure 7 , Figure 8 and Fig. 9 , which can verify the accuracy of the complete surface shape of the surface to be measured obtained by splicing in this embodiment.

[0037] To summarize, the main steps of the high-steepness free-form surface measurement and evaluation method based on coordinate measurement in this embodiment include: high-steepness surface sub-patch segmentation, splicing measurement, path optimization, surface reconstruction, error compensation and accuracy evaluation. The core is the pre-processing steps of high-steepness surface sub-patch segmentation, splicing measurement, path optimization, surface reconstruction or the complete surface shape of the surface to be measured. Optical components with high steepness are widely used in precision physics experiments. Due to their high steepness and sudden change in curvature, it is difficult to obtain accurate surface data using traditional coordinate measuring machines. Based on the gradient characteristics and curvature characteristic distribution of high-steepness complex surfaces, the optimal sub-surface overlapping area ratio is analyzed, and the surface to be measured is divided into several sub-surfaces with overlapping areas considering constraints such as the measurability of the probe. The measurement steepness of the sub-surfaces is reduced by changing the posture of the workpiece, and matching is performed based on the overlapping areas of the sub-surfaces. Error compensation is performed based on the principle of the same surface shape in the overlapping areas. The surface shape of the high-steepness component is obtained by planning the measuring point path through the ant colony optimization algorithm. Finally, the measurement results of the zygo spherical interferometer are used as a benchmark, and the full-aperture and sliced ​​coordinates are used to measure the same surface error, verifying the correctness of the method in this embodiment.

[0038] In addition, the present embodiment also provides a high-steepness free-form surface measurement and evaluation system based on coordinate measurement, including a microprocessor and a memory connected to each other, and the microprocessor is programmed or configured to execute the high-steepness free-form surface measurement and evaluation method based on coordinate measurement. In addition, the present embodiment also provides a computer-readable storage medium, in which a computer program / instruction is stored, and the computer program / instruction is programmed or configured to execute the high-steepness free-form surface measurement and evaluation method based on coordinate measurement through a processor. In addition, the present embodiment also provides a computer program product, including a computer program / instruction, and the computer program / instruction is programmed or configured to execute the high-steepness free-form surface measurement and evaluation method based on coordinate measurement through a processor.

[0039] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application can take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the process Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0040] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for measuring and evaluating a high-steepness free-form surface based on coordinate measurement, characterized in that: The steps include: S101, dividing the surface to be measured of the component into a plurality of sub-surface patches with overlapping areas according to the surface features of the component; S102, finding the optimal measuring point and measuring path on the surface to be measured; S103, using a posture adjustment mechanism to adjust the posture of a coordinate measuring machine, and using the coordinate measuring machine to sequentially measure the surface shape of each sub-face patch according to an optimal measurement point and a measurement path; S104, matching and splicing the overlapping areas of the surface shapes of adjacent sub-patches to obtain a complete surface shape of the surface to be measured for use in surface shape accuracy evaluation of the surface to be measured.

2. The method for measuring and evaluating a high-steepness free-form surface based on coordinate measurement according to claim 1, characterized in that: Step S101 includes: if the surface shape of the component is a regular surface, the uniform area allocation principle is adopted to divide the surface to be measured of the component into multiple sub-surface patches with overlapping areas, and the maximum relative angle of each sub-surface patch does not exceed the preset angle; otherwise, the characteristic structure center of the component is determined, and the surface to be measured of the component is divided into multiple sub-surface patches with overlapping areas with the characteristic structure center as the center, and the maximum relative angle of each sub-surface patch does not exceed the preset angle.

3. The method for measuring and evaluating a high-steepness free-form surface based on coordinate measurement according to claim 2, characterized in that: When the curved surface to be measured of the component is divided into a plurality of sub-surface patches with overlapping areas, the size of the overlapping areas between adjacent sub-surface patches is between 10% and 20%.

4. The method for measuring and evaluating a high-steepness free-form surface based on coordinate measurement according to claim 1, characterized in that: The function expression for finding the optimal measuring point on the surface to be measured in step S102 is: ， In the above formula, For the i The optimal measurement point, for The grid curvature measure of is the jth optimal measurement point, is the measuring point, and: ， ， In the above formula, is the curvature measure of the measuring point, is the contrast adjustment parameter of the measurement point distribution grid, For location The curvature value of and are the minimum and maximum curvature values ​​of the surface to be measured, respectively. The surface to be measured is S={ x , y , z ( x , y )},in x , y , z ( x , y ) are the x, y and z axis coordinates respectively, z x is the partial derivative in the x direction, z y is the partial derivative in the y direction, z xx is the partial derivative of the X plane, z xy is the partial derivative on the Y plane.

5. The method for measuring and evaluating a high-steepness free-form surface based on coordinate measurement according to claim 1, characterized in that: Finding the optimal measurement path on the surface to be measured in step S102 refers to using an ant colony algorithm to find the optimal measurement path on the surface to be measured, and the objective function used by using the ant colony algorithm to find the optimal measurement path on the surface to be measured is that the total length of all paths in the grid on the surface to be measured is the shortest, and the calculation function expression of the total length of all paths is: ， In the above formula, is the total length of all paths, w is the arrangement between grids; For grid i l-1 i l The distance between.

6. The method for measuring and evaluating a high-steepness free-form surface based on coordinate measurement according to claim 1, characterized in that: Step S104 includes: S301, converting the surface shape of each sub-facet from the local coordinates of the sub-facet to a unified global coordinate system; S302, determine any adjacent sub-facets according to the following formula and The deviation of the directed distance between the overlapping point pairs and the nominal surface in the overlapping area : ， In the above formula, is the coordinate of the overlapping area of ​​sub-patch j and sub-patch k on the nominal surface, is the projection point of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface, is the number of projection points of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface, , is the total number of measurement points in the overlapping area, is the coordinate of the overlapping area of ​​sub-patch i and sub-patch k on the nominal surface; S303: based on the directed distance deviation from the overlapping point pairs in the overlapping area to the nominal surface Based on the minimum principle, the following sub-facet synchronous stitching least squares model is established: ， In the above formula, is the objective function, is the total number of overlapping point pairs, is the number of sub-patches; S304, by minimizing the objective function defined in the above formula, solving the optimal configuration parameters Thus, the complete shape of the surface to be measured is obtained.

7. The method for measuring and evaluating a high-steepness free-form surface based on coordinate measurement according to claim 1, characterized in that: After step S104, the method further includes: using a wavefront interferometer to measure and obtain the surface shape of the surface to be measured, and verifying the complete surface shape of the surface to be measured obtained by splicing according to the surface shape of the surface to be measured obtained by the wavefront interferometer.

8. A high-steepness free-form surface measurement and evaluation system based on coordinate measurement, comprising a microprocessor and a memory connected to each other, characterized in that: The microprocessor is programmed or configured to execute the high-steepness free-form surface measurement and evaluation method based on coordinate measurement as described in any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program / instruction stored therein, characterized in that: The computer program / instruction is programmed or configured to execute the high-steepness free-form surface measurement and evaluation method based on coordinate measurement as claimed in any one of claims 1 to 7 through a processor.

10. A computer program product comprising a computer program / instructions, characterized in that The computer program / instruction is programmed or configured to execute the high-steepness free-form surface measurement and evaluation method based on coordinate measurement as claimed in any one of claims 1 to 7 through a processor.

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