A method and system for generating double random machining paths with adjustable surface shape threshold

Abstract

The present invention discloses a method and system for generating a dual random processing path with adjustable surface shape threshold, which belongs to the field of processing technology. First, a mapping relationship between surface shape data height and grayscale value is set, so that the surface shape height information of the workpiece is mapped to the grayscale value of the grayscale image; then, by autonomously setting the expected processing surface shape threshold, the area to be modified is delineated within the entire workpiece surface shape range, and the area to be modified delineated based on the target surface shape threshold is extracted to generate a random resident point cloud; finally, through a heuristic algorithm, a random processing path is generated in the area to be modified that passes through all the resident points, has a short distance, is continuous and does not cross. The present invention can delineate the area to be modified by setting the surface shape threshold, and efficiently generate a dual random processing path with random point cloud and random trajectory, has a strong ability to suppress intermediate frequency errors, avoids further deterioration of local surface shape low points, significantly improves the modification accuracy and efficiency, and helps to improve the convergence efficiency of surface shape errors of large-aperture optical elements.

Description

Technical Field

[0001] The invention belongs to the field of machining technology, and in particular relates to a method and system for generating a double random machining path with adjustable surface threshold. Background Art

[0002] As the development of CNC equipment gradually matures, the trend of using intelligent equipment to replace traditional manual processing is gradually emerging at home and abroad, and the research on CNC equipment processing path generation is also deepening. At present, there are two main methods for CNC equipment processing path generation: one is to plan the processing trajectory on the surface of the workpiece entity first, and then match the three-dimensional point cloud with the surface shape data through visual calibration to obtain the processing coordinates of each dwell point, but due to the existence of point cloud gaps and matching errors, it is difficult to achieve more accurate matching for large-sized workpieces and thin-walled workpieces that are easily deformed; another commonly used method is to reversely reconstruct the scanned physical point cloud into an entity and perform path planning on the reconstructed entity, but it takes a long time and is inefficient to achieve high-precision reconstruction. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a dual random processing path generation method and system with adjustable surface shape threshold, which can delineate the area to be modified by setting the target surface shape threshold, and efficiently generate a dual random processing path with random point cloud and random trajectory, thereby improving the generation efficiency and accuracy of the random processing path, and having stronger randomness, strong ability to suppress medium-frequency surface shape errors, and being able to improve the modification accuracy and efficiency.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A method for generating a double random machining path with adjustable surface threshold comprises the following steps:

[0006] Step 1: Obtain the surface data matrix of the workpiece through the interferometer;

[0007] Step 2: Preprocess the surface data matrix and set the mapping relationship between the surface data height and grayscale value;

[0008] Step 3: Convert the face data matrix into a grayscale image;

[0009] Step 4: Input the target surface threshold through the human-computer interaction module, obtain the gray value range of the area to be modified, determine the area to be modified, and extract the area to be modified to generate a random point cloud;

[0010] Step 5: Use a heuristic algorithm to traverse each random point and generate an acceptable approximate solution of a random path with the shortest distance and no intersection;

[0011] Step 6: Use the coordinate points in the random path as the residence points of the processing path in sequence, and finally generate the processing path.

[0012] The present invention also provides a dual random processing path generation system with adjustable surface threshold, which comprises a human-computer interaction module, a point cloud generation module and a path generation module.

[0013] The human-computer interaction module displays the current face shape data and the peak-to-valley value PV for the user, and provides a window for inputting the target face shape threshold value, and the target face shape threshold value is selected according to different processing requirements;

[0014] The point cloud generation module is used to obtain the surface data matrix of the workpiece surface by using an interferometer, set the mapping relationship between the surface data height and the grayscale value, convert the surface data matrix into a grayscale image, and extract the area to be modified according to the mapping relationship between the surface data height and the grayscale value to generate a random point cloud;

[0015] The path generation module uses a heuristic algorithm to traverse each random point, quickly generates an acceptable approximate solution of the shortest random path without crossing, and uses the point cloud on the random path as the resident points of the processing path in sequence to generate a processing path executable by the CNC device.

[0016] Compared with the existing random processing path generation method, the beneficial effects of the present invention are:

[0017] The present invention is based on surface data, and can flexibly define the area to be modified by setting the target surface threshold, and efficiently generate a dual random processing path of random point cloud and random trajectory. It has a strong ability to suppress intermediate frequency surface errors, and uses a heuristic algorithm to generate an acceptable approximate solution of the shortest path, which saves processing time while avoiding further deterioration of local surface low points, significantly improves the modification accuracy and efficiency, and avoids the problems of long time and difficulty in ensuring accuracy of entity reconstruction. In addition, point clouds are extracted based on surface thresholds, and the generated path has a high degree of matching with the entity, which can meet the processing requirements of large-size workpieces and thin-walled workpieces. Compared with traditional four-way and eight-way random paths, the dual random processing path generated by the present invention has stronger randomness, can effectively suppress intermediate frequency surface errors, and improve the convergence efficiency of surface errors of large-aperture optical components. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a dual random processing path generation system with adjustable surface shape threshold according to the present invention;

[0019] Figure 2 It is the grayscale image of the interferometer detection surface data result;

[0020] Figure 3 It is a schematic diagram of the result of mapping the height of the surface data into a grayscale image;

[0021] Figure 4 To extract the schematic diagram of random point cloud of the area to be processed;

[0022] Figure 5 It is a schematic diagram of the solution process of the simulated annealing algorithm;

[0023] Figure 6 Schematic diagram of an acceptable approximate solution for generating a shortest non-intersecting dual random path. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] like Figure 1 As shown, the present invention provides a dual random processing path generation system with adjustable surface threshold, including a human-computer interaction module, a point cloud generation module and a path generation module.

[0026] The human-computer interaction module displays the current face shape data and the peak-to-valley value PV for the user, and provides a window for inputting the target face shape threshold value, and the target face shape threshold value is selected according to different processing requirements;

[0027] The point cloud generation module is used to obtain the surface data matrix of the workpiece surface by using an interferometer, set the mapping relationship between the surface data height and the grayscale value, convert the surface data matrix into a grayscale image, and extract the area to be modified according to the mapping relationship between the surface data height and the grayscale value to generate a random point cloud;

[0028] The path generation module uses a heuristic algorithm to traverse each area to be modified to generate a random point cloud, and then quickly generates an acceptable approximate solution of the shortest and non-intersecting random path, and uses the point cloud on the random path as the resident points of the processing path in sequence to generate a processing path executable by the CNC equipment.

[0029] The present invention also provides a method for generating a double random processing path with adjustable surface threshold, comprising the following steps:

[0030] Step 1: Obtain the surface data matrix of the workpiece through the interferometer;

[0031] Step 2: Preprocess the surface data matrix and set the mapping relationship between the surface data height and grayscale value;

[0032] Step 3: Convert the face data matrix into a grayscale image;

[0033] Step 4: Input the target surface shape threshold after modification through the human-computer interaction module, obtain the gray value range of the area to be modified, determine the area to be modified, and extract the area to be modified to generate a random point cloud;

[0034] Step 5: Use a heuristic algorithm to traverse each random point and generate an acceptable approximate solution of a random path with the shortest distance and no intersection;

[0035] Step 6: Use the coordinate points in the random path as the residence points of the processing path in sequence, and finally generate the processing path.

[0036] Preferably, in step 1, the error between the surface shape data matrix obtained by the interferometer and the actual surface shape of the workpiece can reach the sub-wavelength level, and is suitable for large-size workpieces with a diameter greater than 500 mm. The surface shape data height distribution obtained by interferometer measurement is as follows: Figure 2 As shown, the original measurement result is the height matrix of the surface data, and the value range of the matrix is ​​approximately [-PV / 2, PV / 2], so Figure 2 The high points and low points of the mid-face shape all occupy a certain grayscale.

[0037] Preferably, in step 2, the preprocessing of the face data matrix is ​​data point translation, which translates the data along the positive direction of the Z axis until the Z coordinate of the lowest point of the face data is 0.

[0038] Preferably, in step 2, setting the mapping relationship between the height of the surface data and the grayscale value includes: after preprocessing, the Z-axis coordinate of the highest point in the surface data represents the peak-to-valley value PV of the workpiece surface, and setting the grayscale value range to 0-255, then the grayscale value corresponding to a point A in the surface data is , where a is the Z-axis coordinate of point A.

[0039] Preferably, in step 3, the grayscale image generation method is based on the mapping relationship between the surface data height and the grayscale value in step 2, maps the surface data matrix obtained by the interferometer into a grayscale value matrix, and uses each element in the matrix as a pixel point at the corresponding grayscale value to generate the mapped grayscale image.

[0040] Preferably, in step 4, the target surface shape threshold refers to the peak-to-valley value PV convergence effect of the workpiece surface shape after the random path processing. Since only the high points of the surface shape are processed, that is, after determining the peak-to-valley value PV of the target, the height range to be modified can be determined. According to the mapping relationship in step 2, the grayscale value range of the area to be modified can be obtained, such as Figure 3 As shown in the figure, when the target surface shape threshold input by the user is 20%PV, the gray value The pixels are removed (i.e. the grayscale value is set to the brightest 255), and the remaining grayscale values ​​in the grayscale image The area where the pixel points are located is identified as the area to be modified. The area to be modified is extracted to generate a random point cloud such as Figure 4 shown.

[0041] Preferably, in step 5, the heuristic algorithm refers to an algorithm that guides the search through heuristic information, and has a stable effect on efficiently generating a short and non-intersecting random path in a point cloud, mainly including one or more combinations of greedy algorithms, particle swarm algorithms, simulated annealing algorithms, and genetic algorithms, which are used to quickly solve an acceptable approximate solution to the optimal random path.

[0042] Preferably, the present invention adopts a simulated annealing algorithm, the principle of which is that according to the physical annealing process, the solid gradually lowers its temperature from a high temperature to reach a stable state with minimum energy, and the acceptable approximate solution of the optimal random path is quickly solved by adjusting the minimum temperature limit, cooling parameters, and changing the number of solutions. The simulated annealing algorithm solution first needs to set the algorithm parameters, then cool down, enter the next cooling temperature, add disturbances to the current solution to generate a new solution, judge whether the objective function is reduced, if it is reduced, accept the new solution, otherwise accept the new solution according to the Metropolis criterion probability, and cyclically disturb and update the solution according to the set number of iterations. After the number of iterations is reached, it is judged whether the termination temperature has been reached. If the termination temperature has been reached, the solution is output, that is, the acceptable approximate solution of the random path with the shortest distance and no intersection is output, otherwise cooling is performed again, entering the next cooling temperature, and the calculation is cyclically calculated until the termination temperature is reached. The solution process is as follows: Figure 5 As shown, the solution result is Figure 6 shown.

[0043] Preferably, in step 6, the process of generating the random processing path is as follows: the data points on the random path generated in step 5 are sequentially used as the dwell points of the random processing path, and the multiple separated data clusters presented by the random point cloud generated in step 4 are used as the areas to be modified. There may be non-processed low point areas between these areas to be modified, and the number of times that the adjacent dwell points of the generated random processing path cross the low point areas of the surface is as small as possible, such as Figure 6 The crossing lines L1 and L2 in the figure are connected by accelerating the speed of the polishing tool crossing the low point area of ​​the surface shape, or lifting the polishing tool so that the polishing tool does not contact the workpiece surface. This avoids further deterioration of the local low point of the surface shape and significantly improves the shaping accuracy and efficiency.

Claims

1. A method for generating a double random machining path with adjustable surface threshold, characterized in that: The steps include: Step 1: Obtain the surface data matrix of the workpiece through the interferometer; Step 2: Preprocess the surface data matrix and set the mapping relationship between the surface data height and grayscale value; Step 3: Convert the face data matrix into a grayscale image; Step 4: Input the target surface shape threshold through the human-computer interaction module, obtain the gray value range of the area to be modified, determine the area to be modified, and extract the area to be modified to generate a random point cloud; the target surface shape threshold refers to the convergence effect of the peak-to-valley value PV of the workpiece surface shape expected after processing. After determining the peak-to-valley value PV, determine the height range of the area to be modified, obtain the gray value range of the area to be modified according to the mapping relationship in step 2, and extract the area to be modified to generate a random point cloud; Step 5: Use a heuristic algorithm to traverse each random point and generate an acceptable approximate solution of a random path with the shortest distance and no intersection; Step 6: Use the coordinate points in the random path as the residence points of the processing path in sequence, and finally generate the processing path.

2. The method for generating a double random machining path with adjustable surface threshold according to claim 1, characterized in that: In step 1, the error between the surface shape data matrix obtained by the interferometer and the actual surface shape of the workpiece reaches the sub-wavelength level. The interferometer is suitable for obtaining the surface shape data matrix of a large-size workpiece surface with a diameter of more than 500 mm.

3. The method for generating a double random processing path with adjustable surface threshold according to claim 1, characterized in that: In step 2, the preprocessing is data point translation, which translates the data along the positive direction of the Z axis until the Z axis coordinate value of the lowest point of the surface data is 0.

4. The method for generating a double random machining path with adjustable surface threshold according to claim 3, characterized in that: In step 2, the mapping relationship between the height of the surface data and the grayscale value is set as follows: after data preprocessing, the Z-axis coordinate value of the highest point in the surface data represents the peak-to-valley value PV of the workpiece surface, and the grayscale value range is set to 0-255, then the grayscale value corresponding to a point A in the surface data is , where a is the Z-axis coordinate value of point A.

5. The method for generating a double random machining path with adjustable surface threshold according to claim 4, characterized in that: In step 3, the method for generating the grayscale image includes: based on the mapping relationship between the surface data height and the grayscale value in step 2, mapping the surface data matrix obtained by the interferometer into a grayscale value matrix, and using each element in the grayscale value matrix as a pixel point at the corresponding grayscale value to generate a mapped grayscale image.

6. The method for generating a double random machining path with adjustable surface threshold according to claim 1, characterized in that: In step 5, the heuristic algorithm guides the search through heuristic information, including a greedy algorithm, a particle swarm algorithm or a simulated annealing algorithm.

7. The method for generating a double random machining path with adjustable surface threshold according to claim 1, characterized in that: In step 6, generating a processing path includes: using the data points on the random path generated in step 5 in sequence as the dwell points of the random processing path, generating a plurality of separated data clusters presented by random point clouds of the area to be modified generated in step 4 as the area to be modified, there are non-processed surface low point areas between the areas to be modified, and the polishing tool is accelerated to cross the surface low point area or the polishing tool is lifted so that the polishing tool and the workpiece surface are connected to adjacent dwell points in a non-contact manner.

8. A dual random processing path generation system with adjustable surface threshold, characterized in that: Including human-computer interaction module, point cloud generation module and path generation module; The human-computer interaction module displays the current surface shape data and the peak-to-valley value PV for the user, and provides a window for inputting the target surface shape threshold value, and the target surface shape threshold value is selected according to different processing requirements; the target surface shape threshold value refers to the convergence effect of the peak-to-valley value PV of the workpiece surface shape expected after processing, after determining the peak-to-valley value PV, the height range of the area to be modified is determined, and the gray value range of the area to be modified is obtained according to the mapping relationship in step 2, and the area to be modified is extracted to generate a random point cloud; The point cloud generation module is used to obtain the surface data matrix of the workpiece surface by using an interferometer, set the mapping relationship between the surface data height and the grayscale value, convert the surface data sentence into a grayscale image, and extract the area to be modified according to the mapping relationship between the surface data height and the grayscale value to generate a random point cloud; The path generation module uses a heuristic algorithm to traverse each random point, quickly generates an acceptable approximate solution of the shortest random path without crossing, and uses the point cloud on the random path as the resident points of the processing path in sequence to generate a processing path executable by the CNC device.

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