Two-dimensional irregular defective leather layout method and computer readable storage medium

Abstract

The invention relates to a two-dimensional irregular defective leather layout method and a computer readable storage medium. The stock layout method comprises the following steps: under all allowable rotation angles, according to input parts, leather plates and defect area information thereof, calculating to obtain critical polygons between the parts, critical polygons between the parts and the defect area of the leather plates, and internal critical polygons between the parts and the leather plates; the method comprises the following steps of: performing pretreatment of outwards expanding all parts for a certain distance, and calculating to obtain a pre-constructed angle library according to a critical polygon between the parts and a part fitting degree index; and in combination with the critical polygon, the internal critical polygon, the pre-constructed angle library and the local fitness index, performing layout by using a local greedy search algorithm, and when no feasible placement area exists in the leather board, ending layout and outputting to obtain a final layout result. According to the method, a high-quality layout scheme is provided, the layout time is saved, and the actual production requirements of leather production enterprises are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional irregular nesting, and particularly relates to a two-dimensional irregular defective leather nesting method based on greedy search and a computer-readable storage medium. Background Art

[0002] The two-dimensional irregular nesting technology is widely used in many fields such as clothing manufacturing, metal processing, tile cutting, leather cutting, etc. Its core goal is to efficiently and reasonably arrange parts of specific shapes in a given two-dimensional sheet to maximize the utilization rate of the sheet. Especially in the leather industry, as a high-value resource, the efficient utilization of leather is particularly important. Due to the irregular shape and material characteristics of leather, traditional nesting methods are difficult to apply, often resulting in serious material waste and high production costs. Therefore, researching and developing an efficient two-dimensional irregular leather nesting method has important practical significance for improving leather utilization rate and reducing production costs.

[0003] Existing research on two-dimensional irregular nesting problems mainly considers nesting in regular sheets or defect-free irregular sheets, and there is little research on nesting irregular parts in defective irregular leather sheets. Moreover, the methods proposed in existing research often have randomness and long nesting time, making it difficult to meet the requirements in the actual production process of the leather industry. Therefore, there is an urgent need in this field to develop a more efficient and stable two-dimensional irregular leather nesting method. Summary of the Invention

[0004] Based on the above-mentioned drawbacks and deficiencies in the prior art, one of the objectives of the present invention is to at least solve one or more of the above problems in the prior art. In other words, one of the objectives of the present invention is to provide a two-dimensional irregular defective leather nesting method based on greedy search and a computer-readable storage medium that meet one or more of the foregoing requirements.

[0005] To achieve the above invention objective, the present invention adopts the following technical solutions:

[0006] A two-dimensional irregular defective leather nesting method includes the following steps:

[0007] S1. At all allowed rotation angles, according to the input part, leather sheet and its defect area information, calculate the critical polygons between parts, the critical polygons between parts and the defect areas of the leather sheet, and the internal critical polygons between parts and the leather sheet;

[0008] S2. Perform preprocessing on all parts by expanding them outward by a certain distance, and then calculate the pre-constructed angle library according to the critical polygons between parts and the part fitting degree index;

[0009] S3. Combine the critical polygon, the internal critical polygon, the pre-built angle library, and the local fitting degree index, and use the local greedy search algorithm for nesting. When there is no more feasible placement area in the leather sheet, the nesting ends, and the final nesting result is output.

[0010] As a preferred solution, the step S2 specifically includes the following steps:

[0011] S21. At all allowed rotation angles, perform an operation of expanding the boundary of the part outward by a certain distance to obtain the expanded part;

[0012] S22. Set the fixed part The expanded part moving Call to obtain the critical polygon at this time According to the part fitting degree index f 1 Calculate the When moving to Each vertex on the boundary and the fixed part The part fitting degrees are obtained, and the maximum fitting degree value and the average fitting degree of each vertex are saved to the maximum value list And the average value list respectively, update the rotation angle r and the expanded part of the fixed part Moving Where i ∈ [1, n], j ∈ [1, n], and n is the number of part types. Repeat this process until the calculation between parts at all allowed rotation angles is completed;

[0013] S23. Respectively find the maximum fitting degree index In the maximum value list and the average value list And And And extract the parts with fitting index values greater than In the two lists and the corresponding angles, perform a union operation to obtain the pre-built angle library of part i For i ∈ [1, n], repeat this process, and then combine all To obtain the final pre-built angle library T pre ; where β is a hyperparameter, and β ∈ (0, 1).

[0014] As a preferred solution, the calculation formula of the part fitting degree index f 1 Is as follows:

[0015]

[0016] Among them, A 1 Represents the area of the outer expansion area of the moving part, A 2Represents the overlapping area between the outer expansion area of the moving part and the fixed part.

[0017] As an optimal solution, step S3 specifically includes the following steps:

[0018] S31. For the first placed part, it is necessary to search all allowed rotation angles of all parts to determine. First, obtain the internal critical polygon IFP of the part and the leather sheet, and the critical polygon NFP of the part and the defect area of the leather sheet. Perform a two-dimensional Boolean difference operation on these two areas to obtain the collision-free area CFR of the part with respect to the leather sheet at this time. Extract the boundary vertices of this area and use the local fitting index f 2 Evaluate the fitting degree of placing the part at each vertex, and select the vertex with the maximum local fitting index and the corresponding angle among all parts at all allowed rotation angles as the placement position and rotation state of the first part;

[0019] S32. According to the rotation angle of the previously placed part and the pre-constructed angle library, calculate the part angle library to be searched in the current round to obtain the current part angle library. Search for the current part angle library. First, obtain the internal critical polygon IFP of the current part and the leather sheet, and then calculate the critical polygon NFP of the current part with respect to all previously arranged parts and the defect area of the leather sheet inside the leather sheet. Perform a two-dimensional Boolean difference operation on IFP and all NFPs to obtain the collision-free area CFR of the current part. When CFR is not empty, extract its vertices and use the local fitting index f 2 Evaluate the fitting degree of placing the part at each of its vertices, and select the vertex with the maximum local fitting index and the corresponding angle under the current part angle library as the placement position and rotation state of the part in this round;

[0020] S33. Repeat step S32 until all CFRs under the current part angle library are empty and stop, indicating that there is no feasible placement area on the leather sheet for the current part angle library;

[0021] S34. Take the full part angle library composed of all allowed rotation angles of the part, perform a difference set operation on the current part angle library to obtain the filtered angle library, continue to search the filtered angle library, select the vertex with the maximum local fitting index and the corresponding angle under the filtered angle library as the placement position and rotation state of the placed part, supplement the nesting until the leather sheet is completely placed, the nesting ends, and the final nesting result is output.

[0022] As a preferred solution, each angle value in the current part angle library is the sum of the rotation angle value of the previous part that has been placed and each angle value in the pre-built angle library; wherein, if the sum of the rotation angle value of the previous part that has been placed and each angle value in the pre-built angle library is greater than 360°, the value is taken as subtracting 360°.

[0023] As a preferred solution, the local fitting degree index f 2 is calculated as follows:

[0024]

[0025] where A 1 represents the area of the outer expansion region of the part to be arranged, A 3 represents the intersection area of the outer expansion region of the part to be arranged and all the arranged parts, A 4 represents the intersection area of the outer expansion region of the part to be arranged and the defective region of the leather sheet, A 5 represents the area of the part of the outer expansion region of the part to be arranged that exceeds the leather boundary.

[0026] The present invention also provides a computer-readable storage medium, in which instructions are stored. When the instructions run on a computer, the computer is made to execute the two-dimensional irregular leather nesting method with defects described in any one of the above solutions.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The present invention calculates the critical polygons between parts, the critical polygons between parts and the defective region of the leather sheet, and the internal critical polygons of parts at all allowed rotation angles; secondly, preprocesses all parts by expanding them outward by a certain distance, and then calculates the pre-built angle library by means of the critical polygons between parts and the part fitting degree index; finally, combines the critical polygons, internal critical polygons, pre-built angle library, and local fitting degree index, and uses the local greedy search algorithm for nesting to complete the entire nesting process.

[0029] The present invention can not only give a high-quality nesting scheme, but also greatly save the nesting time and meet the actual production needs of leather production-related enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flowchart of the two-dimensional irregular leather nesting method with defects according to an embodiment of the present invention;

[0031] Figure 2 is an example diagram of the critical polygon between parts according to an embodiment of the present invention;

[0032] Figure 3 It is an example diagram of the internal critical polygon of the parts and the leather sheet in the embodiment of the present invention;

[0033] Figure 4 It is an example diagram for calculating the fitting degree index of the parts in the embodiment of the present invention;

[0034] Figure 5 It is an example diagram for calculating the local fitting degree index in the embodiment of the present invention;

[0035] Figure 6 It is an example diagram for calculating the collision-free area in the embodiment of the present invention;

[0036] Figure 7 It is the nesting result diagram of test cases 1-1 to 6-3 in the embodiment of the present invention;

[0037] Figure 8 It is the nesting result diagram of test cases 1-4 to 6-6 in the embodiment of the present invention. Detailed implementation manners

[0038] In order to more clearly illustrate the embodiments of the present invention, the specific implementation manners of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings, and other implementation manners can also be obtained.

[0039] As Figure 1 shown, the two-dimensional irregular leather nesting method with defects in the embodiment of the present invention includes the following steps:

[0040] S1: At all allowed rotation angles, according to the input data, namely part data, leather sheet data with defects (leather sheet and its defect area data information), calculate the critical polygon between parts, the critical polygon between the part and the defect area of the leather sheet, and the internal critical polygon of the part and the leather sheet;

[0041] The above step S1 specifically includes the following steps:

[0042] S11: Calculate the critical polygon between parts at all allowed rotation angles. As Figure 2 shown, specifically: Given two polygon parts A and B, where part A remains fixed and part B makes a rigid body movement around A without rotation and slides along its edge until it returns to the starting position. During this process, a point c on part B is selected as a reference point, and the trajectory formed by this point during the movement constitutes the critical polygon NFP AB ;

[0043] S12: Calculate the critical polygons of the part and the defective area of the leather sheet at all allowed rotation angles. The calculation process is similar to that of S11, except that the defective area of the leather sheet is regarded as a fixed part, and the actually nested part is regarded as a moving part for calculation;

[0044] S13: Calculate the internal critical polygons of the part and the leather sheet at all allowed rotation angles. The calculation process is similar to that of S11, except that the boundary of the leather sheet is regarded as a fixed part, and the actually nested part is regarded as a moving part. Let the moving part slide around the inside of the boundary of the leather sheet to obtain the movement trajectory of the reference point, specifically as Figure 3 shown.

[0045] S2: Perform preprocessing on all parts by expanding them outward by a certain distance, and then calculate the pre-constructed angle library by means of the critical polygons between parts and the part fitting degree index;

[0046] The above step S2 specifically includes the following steps:

[0047] S21: At all allowed rotation angles, perform an operation of expanding the boundary of the part outward by a certain distance to obtain the expanded part;

[0048] S22: Set the fixed part the moving expanded part Call to obtain the critical polygon at this time According to the part fitting degree index f 1 Calculate the when moving to each vertex on the boundary and the fixed part of the part fitting degree, obtain the maximum fitting degree value and the average fitting degree of each vertex, and save them to the maximum value list and the average value list respectively, update the rotation angle r and the fixed part the moving expanded part where i ∈ [1, n], j ∈ [1, n], and n is the number of part types. Repeat this process until the calculation between all parts at all allowed rotation angles is completed;

[0049] Among them, the calculation example diagram of the part fitting degree index f 1 is as shown in Figure 4 shown, and the calculation formula is as follows:

[0050]

[0051] Among them, A 1 represents the area of the outer expansion area of the moving part, and A 2 represents the overlapping area between the outer expansion area of the moving part and the fixed part;

[0052] S23: Find the maximum value list respectively and the average value list for the maximum value of the fitting index and extract the parts included in the two lists where the fitting index value is greater than and the corresponding angles, perform a union operation, and obtain the pre-built angle library of part i For i ∈ [1, n], repeat this process, and then combine all to obtain the final pre-built angle library T pre .

[0053] S3: Combine the critical polygon, internal critical polygon, pre-built angle library, and local fitting index, and use the local greedy search algorithm for nesting. When there is no more feasible placement area in the leather sheet, the nesting ends, and the final nesting result is output;

[0054] The above step S3 specifically includes the following steps:

[0055] S31: For the first part to be placed, it needs to be determined by searching all allowed rotation angles of all parts. First, obtain the internal critical polygon IFP of the part and the leather sheet, and the critical polygon NFP of the part and the defect area of the leather sheet. Perform a two-dimensional Boolean difference operation on these two areas to obtain the collision-free area CFR of the part with the leather sheet at this time. Extract the boundary vertices of this area and use the local fitting index f 2 to evaluate the fitting degree of placing the part at each vertex, and select the vertex with the maximum local fitting index of all parts at all allowed rotation angles and the corresponding angle as the placement position and rotation state of the first part;

[0056] Among them, the local fitting index f 2 is shown in the calculation example diagram as Figure 5 shown, and the calculation formula is as follows:

[0057]

[0058] Among them, A 1 represents the area of the expanded area of the part to be nested, A 3 represents the intersection area of the expanded area of the part to be nested and all the parts that have been nested, A 4 represents the intersection area of the expanded area of the part to be nested and the defect area of the leather sheet, A 5 represents the area of the part of the expanded area of the part to be nested that exceeds the leather boundary.

[0059] S32: According to the rotation angle of the last placed part and the pre-built angle table, calculate the part angle library to be searched in the current round to obtain the current part angle library. Search for the current part angle library. First, obtain the internal critical polygon IFP of the current part and the leather sheet. Then, calculate the critical polygon NFP of the current part with respect to all the placed parts and defects inside the leather sheet. Perform a two-dimensional Boolean difference operation on the IFP and all the NFPs to obtain the collision-free region CFR of the current part. The calculation example diagram of the CFR is as shown in Figure 6 shown. When the CFR is not empty, extract its vertices and use the local fitting degree index f 2 to evaluate the fitting degree of placing the part at each of its vertices, and select the vertex with the maximum local fitting degree index and the corresponding angle in the current part angle library as the placement position and rotation state of the part in this round;

[0060] Among them, each angle value in the current part angle library of the embodiment of the present invention is the sum of the rotation angle value of the last placed part and each angle value in the pre-built angle library. Among them, if the sum of the rotation angle value of the last placed part and each angle value in the pre-built angle library is greater than 360°, the value is taken as minus 360°;

[0061] S33: Repeat S32 until all the CFRs in the current part angle library are empty and stop, indicating that there is no feasible placement area for the leather sheet in the current part angle library;

[0062] S34: Take the full part angle library composed of all the allowed rotation angles of the part, perform a difference set operation on the current part angle library to obtain the filtered angle library, continue to search for the filtered angle library, and select the vertex with the maximum local fitting degree index and the corresponding angle in the filtered angle library as the placement position and rotation state of the placed part, and supplement the nesting until the leather sheet is fully placed, that is, when there is no feasible placement area in the leather sheet, the nesting ends and the final nesting result is output.

[0063] The embodiment of the present invention is tested with the data collected in actual production. These data include six parts with irregular shapes and six leather sheets with defective areas, a total of 36 test cases, to evaluate the nesting effect.

[0064] Table 1: Comparison table of nesting results of two algorithms

[0065]

[0066]

[0067] In the embodiments of the present invention, the nesting results of two algorithms, namely local greedy search without using a pre-built angle library and local greedy search based on a pre-built angle library, are compared, and the comparison results are shown in Table 1. In Table 1, the test case number "2-1" represents an experiment of placing a part numbered 1 on a leather sheet numbered 2. The embodiments of the present invention use the sheet utilization rate, the number of parts in the final nesting scheme, the average time-consuming for running 10 times, and the time improvement rate as evaluation indicators to evaluate these two algorithms. The bold data in Table 1 represents the best results obtained in the two algorithms. Further, Figure 7 and Figure 8 intuitively shows the nesting effect diagram of the local greedy search algorithm based on the pre-built angle library.

[0068] As can be seen from Table 1, for a total of 36 test cases, in the two key indicators of sheet utilization rate and the number of nested parts, the local greedy search algorithm based on the pre-built angle library achieved the optimal results in 27 cases. Among them, 18 cases achieved individual optimality, and 9 cases reached the consistent optimality with the local greedy search algorithm without using the pre-built angle library, which shows the nesting performance of the algorithm in this paper. For the remaining 9 test cases that did not reach the optimal solution, except for "2-5" and "4-5", the other 7 cases only had a slight difference in the number of nested parts compared with the unoptimized algorithm, which also confirmed the stability of the algorithm. In terms of time performance, compared with the unoptimized algorithm, there is a significant improvement. The time improvement rate generally ranges from 77.22% to 97.09%, and the average value is as high as 90.46%, reflecting the high operating speed of the algorithm. Generally speaking, the algorithm proposed by the present invention not only performs excellently in nesting quality, but also has obvious advantages in nesting efficiency, and can meet the actual production requirements.

[0069] The above description only elaborates on the preferred embodiments and principles of the present invention in detail. For those of ordinary skill in the art, according to the idea provided by the present invention, there will be changes in the specific implementation manners, and these changes should also be regarded as the protection scope of the present invention.

Claims

1. A two-dimensional irregular defective leather arrangement method, characterized in that: The steps include: S1. Under all allowed rotation angles, according to the input information of parts, leather plates and their defective areas, calculate the critical polygons between parts, the critical polygons of the defective areas of parts and leather plates, and the internal critical polygons of parts and leather plates; S2. Preprocess all parts by expanding them outwards for a certain distance, and then calculate the pre-built angle library based on the critical polygons between the parts and the part fit index; S3. Combining critical polygons, internal critical polygons, pre-built angle library, and local fit index, the local greedy search algorithm is used for layout. When there is no feasible placement area in the leather plate, the layout ends and the final layout result is output.

2. The method for arranging two-dimensional irregular defective leather according to claim 1, characterized in that: The step S2 specifically includes the following steps: S21, at all allowed rotation angles, the part is expanded outward by a certain distance from the boundary to obtain an expanded part; S22. Set fixed parts Expanded parts of the movement Call to get the critical polygon at this time According to the part fit index f1, the Move to Each vertex on the boundary is connected to the fixed part The maximum value of the fit and the average value of the fit of each vertex are obtained and saved in the maximum value list respectively. and mean list In the example above, update the rotation angle r and the fixed parts Expanded parts of the movement Where i∈[1,n], j∈[1,n], n is the number of part types, and this process is repeated until all parts under all allowed rotation angles are calculated; S23. Find the maximum value list respectively and mean list The maximum value of the fit index in and And the values ​​of the fitting index in the two lists are greater than The included parts and corresponding angles are extracted, and a union operation is performed to obtain the pre-built angle library of part i For i∈[1,n], repeat this process and then Combine to get the final pre-built angular library T pre ; Among them, β is a hyperparameter, β∈(0,1).

3. The method for arranging two-dimensional irregular defective leather according to claim 2, characterized in that: The calculation formula of the part fit index f1 is as follows: Among them, A1 represents the area of ​​the expanded area of ​​the moving part, and A2 represents the overlapping area of ​​the expanded area of ​​the moving part and the fixed part.

4. The method for arranging two-dimensional irregular defective leather according to any one of claims 1 to 3, characterized in that: The step S3 specifically comprises the following steps: S31. For the first part to be placed, it is necessary to search all the allowable rotation angles of all parts to determine, first obtain the internal critical polygon IFP between the part and the leather plate, and the critical polygon NFP between the part and the defective area of ​​the leather plate, perform a two-dimensional Boolean difference operation on these two areas, obtain the collision-free area CFR of the part with the leather plate at this time, extract the boundary vertices of the area, use the local fit index f2 to evaluate the fit of the parts placed on each vertex, select the vertex with the maximum value of the local fit index of all parts at all allowable rotation angles and the corresponding angle as the placement point and rotation state of the first part; S32. According to the rotation angle of the last part that has been placed and the pre-built angle library, the part angle library that should be searched in the current round is calculated to obtain the current part angle library. The current part angle library is searched to first obtain the internal critical polygon IFP of the current part and the leather plate, and then the critical polygon NFP of the current part to all the arranged parts and defective areas inside the leather plate is calculated. The IFP is subjected to a two-dimensional Boolean difference operation with all the NFPs to obtain the collision-free region CFR of the current part. When the CFR is not empty, its vertices are extracted, and the local fit index f2 is used to evaluate the fit of the parts placed on each of its vertices. The vertex with the maximum value of the local fit index under the current part angle library and the corresponding angle are selected as the placement point and rotation state of the part to be placed in this round. S33, repeating step S32 until all CFRs under the current part angle library are empty, which means that there is no feasible placement area for the leather plate in the current part angle library; S34. Take the full part angle library consisting of all allowable rotation angles of the parts, make a difference set on the current part angle library, obtain the angle library after elimination, continue searching the angle library after elimination, select the vertex with the maximum value of the local fit index under the angle library after elimination and the corresponding angle as the placement point and rotation state of the part, supplement the nesting, until the leather plate is completely placed, the nesting is completed, and the final nesting result is output.

5. The method for arranging two-dimensional irregular defective leather according to claim 4, characterized in that: The angle values ​​in the current part angle library are the sum of the rotation angle value of the last part that has been placed and the angle values ​​in the pre-built angle library; if the sum of the rotation angle value of the last part that has been placed and the angle values ​​in the pre-built angle library is greater than 360°, the value is taken minus 360°.

6. The method for arranging two-dimensional irregular defective leather according to claim 4, characterized in that: The calculation formula of the local fit index f2 is as follows: Among them, A1 represents the area of ​​the expanded area of ​​the parts to be arranged, A3 represents the intersection area of ​​the expanded area of ​​the parts to be arranged and all the arranged parts, A4 represents the intersection area of ​​the expanded area of ​​the parts to be arranged and the defective area of ​​the leather plate, and A5 represents the area of ​​the part of the expanded area of ​​the parts to be arranged that exceeds the leather boundary.

7. A computer-readable storage medium, wherein instructions are stored in the computer-readable storage medium, characterized in that: When the instructions are executed on a computer, the computer is enabled to execute the two-dimensional irregular defective leather arrangement method as described in any one of claims 1 to 6.

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