Knowledge-driven die surface design method for automobile panel

Abstract

The present invention provides a knowledge-driven automobile panel die surface design method, which relates to the field of intelligent design technology and includes the following steps: S1: construct a template library; S2: obtain a panel, search in the template library according to the panel, and obtain a target template; S3: combine the target template to design the die surface of the panel, including stamping direction design, pressing surface design and process supplement design: S31: stamping direction design is designed according to the stamping direction in the target template; S32: pressing surface design is designed according to the stamping direction and the boundary and contour information of the panel; S33: process supplement design is designed according to the boundary, parting line and section line of the panel. The present invention can solve the problem that the automobile panel die surface design is heavily dependent on design experience and the enterprise data reuse rate is low.

Description

Technical Field

[0001] The invention relates to the technical field of intelligent design, and in particular to a knowledge-driven automobile cover die surface design method. Background Art

[0002] Body research and development is an important part of automobile manufacturing and a key factor affecting the manufacturing cycle and quality of automobiles. The key content is the design and optimization of the die surface of the cover stamping process. Die surface design relies heavily on the experience of designers and usually refers to similar products for analog design. However, the engineering expertise in this field is empirical, uncertain and vague, lacks effective induction and organization, and the reuse and sharing of knowledge are poor. Knowledge Based Engineering (KBE) is a computer integrated processing technology for the entire product process. It takes knowledge as the core and solves practical engineering problems by expanding, multiplying, managing and applying knowledge. KBE breaks the barriers to the exchange and inheritance of domain expertise and can achieve domain expertise-driven design.

[0003] Regarding the research and application of KBE technology in the field of panel design, there are a large number of literatures that provide different solutions from the theoretical and practical application levels. As the core part of KBE, knowledge reasoning plays an important role in dynamically maintaining and expanding the knowledge base and realizing the automatic accumulation and reuse of knowledge. It can be mainly divided into case-based reasoning (CBR) and rule-based reasoning (RBR). CBR focuses on the use of instances and solves problems by analogy with previous instances, while RBR focuses on the use of rules and pays attention to reasoning based on pre-defined rules. Instances provide specific case support, and rules summarize and conclude instances. In KBE practice, instances and rules often complement each other. As the basis for the formation of knowledge, they provide underlying support for knowledge reasoning.

[0004] At present, the main design methods in the industry for simultaneous engineering include the use of general 3D design software (such as UG / CATIA) and special design software (such as AutoForm / DynaForm / IDF) for design, but these design methods and software generally lack knowledge-driven intelligent design methods. In addition, the existing automotive panel die surface design has the problem of heavy reliance on design experience and low enterprise data reuse rate. Summary of the invention

[0005] In view of this, the present invention provides a knowledge-driven automobile panel die surface design method, which extracts the knowledge in the die surface design process, forms an intelligent template library with a three-layer knowledge architecture of "abstract template-instance template-partition template", uses keyword retrieval and geometric similarity retrieval for intelligent template matching, and realizes the automatic accumulation and reuse of knowledge templates. The knowledge-driven design method summarizes the manual experience in the die surface design process, forms knowledge expressed in the form of rules and formulas, and combines with intelligent templates to realize the automatic design of the die surface.

[0006] The technical purpose of the present invention is achieved in this way:

[0007] The present invention provides a knowledge-driven automobile panel die surface design method, comprising the following steps:

[0008] S1: build template library;

[0009] S2: Obtain the cover, search in the template library according to the cover, and obtain the target template;

[0010] S3: Combined with the target template, the die surface design of the cover is carried out, including stamping direction design, pressing surface design and process supplementary design:

[0011] S31: The stamping direction design is designed according to the stamping direction in the target template;

[0012] S32: The blanking surface is designed according to the stamping direction and the boundary and contour information of the cover;

[0013] S33: Process supplementary design is designed according to the boundary, parting line and section line of the cover.

[0014] On the basis of the above solution, preferably, the template library includes abstract templates, instance templates and partition templates, wherein the partition templates are obtained by dividing the instance templates according to regions.

[0015] Based on the above solution, preferably, step S32 includes:

[0016] S321: determining a stamping coordinate system according to the stamping direction, and projecting the boundary of the cover onto the yoz plane along the x-axis of the stamping coordinate system to obtain a first projection line YPC;

[0017] S322: equally divide the first projection line YPC, obtain the middle part of the first projection line YPC, search for the lowest point on the first projection line YPC, and determine whether the lowest point is in the middle part of the first projection line YPC, if so, execute step S328, if not, execute step S323;

[0018] S323: Find two target low points P1 and P2 on the first projection line YPC, connect P1 and P2 to obtain a first straight line L1, and use the line segment between P1 and P2 on the first projection line YPC as a first curve S1;

[0019] S324: Calculate the vertical distance between every two points on the first straight line L1 and the first curve S1, and select the largest first vertical distance D1;

[0020] S325: Projecting the boundary of the cover onto the xoz plane along the y-axis of the stamping coordinate system to obtain a second projection line XPC;

[0021] S326: Obtain the symmetry plane of the second projection line XPC, and calculate the minimum second vertical distance D2 from the lowest point on the second projection line XPC to the intersection of the second projection line XPC and the symmetry plane;

[0022] S327: Determine whether D1≤D2. If yes, execute step S328; if no, execute step S329;

[0023] S328: determining that the cover is bent in the X direction, and generating an X-direction bent pressing surface;

[0024] S329: Determine that the cover is bent in the Y direction, and generate a Y-direction bent pressing surface.

[0025] Based on the above solution, preferably, step S328 includes:

[0026] Determine the product surface, boundary, symmetry surface and height value of the cover;

[0027] Draw a second straight line perpendicular to the symmetry plane at the intersection of the boundary and the symmetry plane respectively, determine the front side of the cover according to the number of intersections of the second straight line and the boundary, and take the most convex point of the front side as point C;

[0028] Make a minimum enclosing box of the boundary on the top view of the cover, take the side of the minimum enclosing box corresponding to the front side as the first side, take the side adjacent to the first side as the second side, select the edge points of the boundary located on the front side as the first candidate points, calculate the vertical distances between the first candidate points and the first side and the second side respectively, obtain the first distance and the second distance, select the corresponding first candidate points whose first distance is less than the second distance as the second candidate points, calculate the distance between the second candidate point and point C, and select the second candidate point with the farthest distance as point D;

[0029] Discrete the points on the boundary and search for the two points with the lowest z coordinates as points A and B;

[0030] Create an initial pressing surface with preset length and width and 0 height;

[0031] Create a first control line perpendicular to the symmetry plane. The first control line is tangent to the front side, and the tangent point is point C.

[0032] Create a second control line parallel to the symmetry plane, the second control line intersects the first control line, and point D is located on the second control line;

[0033] Adjust the shape and size of the binder surface according to the first control line and the second control line;

[0034] Calculate the current distance between the pressing surface and the cover, move the pressing surface to below the cover, set the distance between the pressing surface and the cover to x, and update the moved distance value to the height of the pressing surface.

[0035] Based on the above solution, preferably, step S329 includes:

[0036] The two endpoints of the first projection line YPC are used as the first endpoint and the second endpoint;

[0037] Traverse the first projection line YPC, remove its invalid line segments, and obtain a new first projection line YPC';

[0038] Select five candidate points on YPC' with equal width, and connect the five candidate points in sequence to obtain the first curve segment C1;

[0039] Linearly extend C1 in a direction close to the second end point until it reaches the boundary of the binder surface to obtain an extended line segment;

[0040] Determine whether the extended line segment is upturned:

[0041] If so, adjust the two ends of the extended line segment to the same height;

[0042] If not, determining whether the extended line segment is inclined downward by more than a predetermined angle, and if so, adjusting the downwardly inclined end of the extended line segment to the predetermined angle;

[0043] Calculate the surface tangent line V1 of the cover according to the intersection of the cover boundary and the symmetry plane;

[0044] Extend the extended line segment in a direction close to the first end point and parallel to V1, and adjust the extended line segment again according to the relative position relationship between V1 and the Y axis to obtain a cross-sectional line of the binder surface;

[0045] Calculate the current distance between the pressing surface and the cover, move the pressing surface to below the cover, set the distance between the pressing surface and the cover to x, and update the moved distance value to the height of the pressing surface.

[0046] On the basis of the above solution, preferably, the first projection line YPC is traversed, and its invalid line segments are removed to obtain a new first projection line YPC', including:

[0047] Starting from the first end point of the first projection line YPC, search for a line segment whose tangent direction forms an obtuse angle with the X-axis, take it as the first invalid line segment, and remove it from the first projection line YPC to obtain YPC1;

[0048] Start searching from the first endpoint, find the first downward cusp, calculate the distance between the cusp and the first endpoint, and if the distance is less than a predetermined value, remove the second invalid line segment between the cusp and the first endpoint to obtain YPC2;

[0049] Start searching from the second endpoint, find the first downward cusp, calculate the horizontal distance between the cusp and the second endpoint, if the horizontal distance is less than 1 / 8 YPC horizontal width, remove the third invalid line segment between the cusp and the second endpoint, and get YPC3;

[0050] YPC3 is smoothed to obtain a new first projection line YPC'.

[0051] Based on the above solution, preferably, step S33 includes:

[0052] S331: extracting boundary feature points using a feature extraction algorithm to obtain a first boundary feature point set P1 of the cover, selecting the middle point of two first boundary feature points from adjacent feature points of the first boundary feature point set P1 as a new feature point to be added to the set, and obtaining a second boundary feature point set P2;

[0053] S332: partitioning the second boundary feature point set P2 based on a boundary partitioning method to obtain five boundary partitions, namely, a front bumper area, a headlight area, a fender area, a transition area, and a windshield area;

[0054] S333: Calculate a parting line position point set P3 for five boundary partitions according to a parting line calculation method;

[0055] S334: traversing the boundary partitions, generating a partition curve group based on the second boundary feature points in the boundary partitions and the shape features of the boundary partitions, offsetting outwards in sequence to obtain a biased curve group, performing transition connection and corner smoothing on sequentially connected curves in the biased curve group, and obtaining a parting line;

[0056] S335: Expand the second boundary feature point set P2 with empirical points to form a candidate insertion point set P4 for section lines, arrange section lines according to the candidate insertion point set P4 for section lines, construct a grid according to the section lines and parting lines, and create a process supplementary surface according to the grid.

[0057] Based on the above solution, preferably, the boundary partitioning method includes:

[0058] Starting from the second boundary feature point, look for the turning point of curvature change on both sides as the partition point;

[0059] The two end points of the boundary are connected with the nearest partition point to form a front protection zone and a windshield zone;

[0060] Find the next two nearest partition points from the front protection area toward the border to form the headlight area;

[0061] Find the next nearest partition point from the headlight area toward the boundary as an end point of the fender area;

[0062] Find a point along the boundary whose tangent direction is parallel to the symmetry plane, and use this point as the partition endpoint between the fender area and the windshield area, that is, the other endpoint of the fender area;

[0063] The fender area is formed according to the two end points of the fender area, and a transition area is between the fender area and the windshield area.

[0064] Based on the above solution, preferably, the parting line calculation method includes:

[0065] According to the side of the cover member located in the windshield area as the windshield side, and according to the curvature of the windshield side and the boundary of the cover member, a first arc and a second arc are constructed;

[0066] Constructing a covering line of the covering member according to the first arc and the second arc, wherein the first arc, the second arc and the covering line form a closed figure and completely cover the covering member;

[0067] Rounding the first arc, the second arc and the covering line;

[0068] The tail points of the cross-section line at the second boundary feature point set P2 are calculated according to the cross-section line rule, and the parting line is located outside all the tail points.

[0069] On the basis of the above solution, preferably, the cross-section line rule is: the windshield area uses the Bar type cross-section line, and other areas use the platform type cross-section line.

[0070] The method of the present invention has the following beneficial effects compared with the prior art:

[0071] (1) The present invention adopts a knowledge-driven approach that is a hybrid of instance-based and rule-based, aiming to allow the two intelligent design methods, instance-based and rule-based, to promote and complement each other, making more comprehensive use of domain expertise and improving the intelligence level of cover die surface design;

[0072] (2) The present invention extracts knowledge from the die surface design process, forms an intelligent template library with a three-layer knowledge architecture of "abstract template-instance template-partition template", uses keyword retrieval and geometric similarity retrieval for intelligent template matching, and realizes the automatic accumulation and reuse of knowledge templates. The knowledge-driven design method summarizes the manual experience in the die surface design process, forms knowledge expressed in the form of rules and formulas, and combines it with intelligent templates to realize the automated design of the die surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0074] Figure 1 It is a schematic diagram of the design of an embodiment of the present invention;

[0075] Figure 2 A schematic diagram of a template library design according to an embodiment of the present invention;

[0076] Figure 3 A schematic diagram of a full-parameter cross-section line template according to an embodiment of the present invention;

[0077] Figure 4 A supplementary schematic diagram of the process of an embodiment of the present invention;

[0078] Figure 5 A schematic diagram of boundary partitioning according to an embodiment of the present invention;

[0079] Figure 6 A schematic diagram of calculation of parting line position points according to an embodiment of the present invention;

[0080] Figure 7 A schematic diagram of constructing a parting line according to an embodiment of the present invention;

[0081] Figure 8 It is a cross-sectional schematic diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0082] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0083] like Figure 1As shown, the present invention provides a knowledge-driven automobile panel die surface design method, comprising the following steps:

[0084] S1: build template library;

[0085] S2: Obtain the cover, search in the template library according to the cover, and obtain the target template;

[0086] S3: Combined with the target template, the die surface design of the cover is carried out, including stamping direction design, pressing surface design and process supplementary design:

[0087] S31: The stamping direction design is designed according to the stamping direction in the target template;

[0088] S32: The blanking surface is designed according to the stamping direction and the boundary and contour information of the cover;

[0089] S33: Process supplementary design is designed according to the boundary, parting line and section line of the cover.

[0090] Specifically, the template library collects successful design cases from the past and stores them in categories and partitions. The design ideas are as follows: Figure 2 As shown. The intelligent template library is a collection of templates that summarize the existing cover die surface design data. These templates can include cover die surface design data of different shapes, sizes and characteristics and related process parameters, processing requirements and cover feature information. Intelligence is mainly reflected in: after the die surface design of the cover is completed, it can be automatically accumulated into the template library; the matching template is selected by similarity matching for template-driven design; template accumulation and reuse of templates with different data granularities are supported; the template library performs lightweight expression and storage of die surface design data.

[0091] Since the same type of covers have certain similarities, but some partitions are different in most cases, it is unreasonable to reuse the instance template in its entirety during the process of using templates for process supplementation, so the concept of partition template is proposed. The instance template contains the process supplementation design knowledge of previous instances. On this basis, another layer of division is performed, and the instance template is divided into partition templates based on partitions. In this way, in the scenario of process supplementation reuse templates, the current part can be in different partitions, based on the partition similarity, to retrieve and match the partition template with high similarity, so as to achieve smaller granularity and better design data inheritance. It is finally represented as a three-layer template structure of abstract template-instance template-partition template.

[0092] In this embodiment, after obtaining a new cover, if a template with high similarity is retrieved, it is recommended to use the template library; if the retrieved template has low similarity, it is recommended to use the rule. For parts with "common faces", the rule effect is even better than the template library. The specific implementation process is as follows:

[0093] (a) Keyword matching: The system automatically searches for abstract templates matching the input keywords in the template library based on keywords such as product name, material, and product features.

[0094] The following conditions are often used to classify parts and obtain abstract templates:

[0095] Type, such as side panels, fenders, etc.

[0096] Materials, such as steel, aluminum, etc.;

[0097] Integrity, such as whole, parts, etc.;

[0098] Position, such as front, back, etc.;

[0099] Vehicle type, such as hatchback, sedan, etc.

[0100] Each abstract template integrates the rules of process mode and stamping coordinate system, which are automatically inherited in the subsequent design process.

[0101] (b) Similarity retrieval and matching: The main evaluation indicators of similarity are: first, the similarity of the discrete point set of the three-dimensional contour curve of the cover, which expresses the similarity of the boundary of the cover product; second, the similarity of the external tangent set of the cover contour surface, which expresses the similarity of the surface at the contour of the cover product. The weighted average of the two is the overall similarity. This embodiment proposes a similarity retrieval and matching method based on different granularities (instance templates, partition templates), and reasonably selects the adaptive granularity for similarity retrieval and matching according to the overall or local similarity of the cover. The similarity is calculated using the Dynamic Time Warping (DTW) algorithm.

[0102] The similarity search rules include:

[0103] Similarity = boundary similarity * weight 1 + boundary tangent similarity * weight 2.

[0104] The template is rotated, translated, and scaled to best fit the new product, and then the similarity is calculated.

[0105] Discretely match the boundaries of the template and the new product respectively, and calculate the boundary similarity.

[0106] Calculate the boundary tangent similarity based on the tangent at discrete points of the template and new product boundaries. Assign weights based on importance.

[0107] (c) Stamping direction design: The rationality of the stamping direction is related to whether the material can flow fully and whether it will cause quality problems such as cracking and wrinkling. The intelligent design of stamping direction mainly adopts the design method of matching abstract templates to inherit the stamping direction, which can better utilize the similarity of product surface features.

[0108] (d) Blanking surface design: The main content of blanking surface design is to design a three-dimensional surface that is conducive to material flow and plastic deformation based on the determined stamping direction and the boundary and contour information of the cover model itself. The intelligent design of the blanking surface adopts a hybrid design method driven by examples and rules, combining the two methods of matching instance templates to inherit the blanking surface data and automatically generating the blanking surface based on empirical rules, comprehensively evaluating the template similarity and automatic generation effect and making a selection.

[0109] (e) Process supplement design: The design content of process supplement mainly includes the design of parting line and the design of process supplement surface. Parting line refers to the three-dimensional curve used to separate the mold and cut the pressing surface. The purpose of adding process supplement surface is to smoothly draw out qualified parts. The geometric shape of the qualified parts is mainly determined by the wireframe composed of the cover part boundary, parting line and section line. The intelligent design of process supplement also adopts a design method driven by instances and rules. It combines the three methods of matching instance templates to inherit process supplement data, matching partition templates to inherit process supplement data and automatically generating process supplements based on empirical knowledge. It comprehensively evaluates the template inheritance granularity, similarity and automatic generation effect and makes a selection.

[0110] Specifically, in one embodiment of the present invention, step S32 includes:

[0111] S321: determining a stamping coordinate system according to the stamping direction, and projecting the boundary of the cover onto the yoz plane along the x-axis of the stamping coordinate system to obtain a first projection line YPC;

[0112] S322: equally divide the first projection line YPC, obtain the middle part of the first projection line YPC, search for the lowest point on the first projection line YPC, and determine whether the lowest point is in the middle part of the first projection line YPC, if so, execute step S328, if not, execute step S323;

[0113] S323: Find two target low points P1 and P2 on the first projection line YPC, connect P1 and P2 to obtain a first straight line L1, and use the line segment between P1 and P2 on the first projection line YPC as a first curve S1;

[0114] Specifically, if the number of lowest points is 0, the two points with the largest absolute value of the Y coordinate on the line are taken as the target points. If the number of lowest points is 1, the other point is the point farther from the existing lowest point among the two points with the largest absolute value of the Y coordinate on the line. If both lowest points are on the front side (or windshield side), remove the higher lowest point and find the second downward sharp point on the windshield side (or front side) (if it cannot be found, take the point with the largest absolute value of the Y coordinate).

[0115] S324: Calculate the vertical distance between every two points on the first straight line L1 and the first curve S1, and select the largest first vertical distance D1;

[0116] S325: Projecting the boundary of the cover onto the xoz plane along the y-axis of the stamping coordinate system to obtain a second projection line XPC;

[0117] S326: Obtain the symmetry plane of the second projection line XPC, and calculate the minimum second vertical distance D2 from the lowest point on the second projection line XPC to the intersection of the second projection line XPC and the symmetry plane;

[0118] S327: Determine whether D1≤D2. If yes, execute step S328; if no, execute step S329;

[0119] S328: determining that the cover is bent in the X direction, and generating an X-direction bent pressing surface;

[0120] S329: Determine that the cover is bent in the Y direction, and generate a Y-direction bent pressing surface.

[0121] In this embodiment, step S328 includes:

[0122] Determine the product surface, boundary, symmetry surface and height value of the cover;

[0123] Draw a second straight line perpendicular to the symmetry plane at the intersection of the boundary and the symmetry plane respectively, determine the front side of the cover according to the number of intersections of the second straight line and the boundary, and take the most convex point of the front side as point C;

[0124] Make a minimum enclosing box of the boundary on the top view of the cover, take the side of the minimum enclosing box corresponding to the front side as the first side, take the side adjacent to the first side as the second side, select the edge points of the boundary located on the front side as the first candidate points, calculate the vertical distances between the first candidate points and the first side and the second side respectively, obtain the first distance and the second distance, select the corresponding first candidate points whose first distance is less than the second distance as the second candidate points, calculate the distance between the second candidate point and point C, and select the second candidate point with the farthest distance as point D;

[0125] Discrete the points on the boundary and search for the two points with the lowest z coordinates as points A and B;

[0126] Create an initial pressing surface with preset length and width and 0 height;

[0127] Create a first control line perpendicular to the symmetry plane. The first control line is tangent to the front side, and the tangent point is point C.

[0128] Create a second control line parallel to the symmetry plane, the second control line intersects the first control line, and point D is located on the second control line;

[0129] Adjust the shape and size of the binder surface according to the first control line and the second control line;

[0130] Calculate the current distance between the pressing surface and the cover, move the pressing surface to below the cover, set the distance between the pressing surface and the cover to x, and update the moved distance value to the height of the pressing surface.

[0131] Take the outer panel of the cover as an example:

[0132] First, select the points. Select the two lowest convex points on the side to determine the side direction trend. Select the front side on the product boundary where the front of the vehicle is located, a point on the symmetry plane, the outermost edge point on the main side and its symmetric point. The Z coordinates of the three points constitute the front trend.

[0133] Draw a straight line perpendicular to the symmetry plane at the intersection of the product boundary and the symmetry plane. The side where the straight line has fewer intersections with the product boundary in the top view is the side where the front of the vehicle is located. If the number of intersections is equal, it will prompt that it cannot be automatically created. The most convex point on the side where the front of the vehicle is located is point C.

[0134] Among the edge points on the product boundary, find a point that meets the requirements: make the smallest enclosing box of the product boundary on the top view, and select the point closer to the corresponding enclosing box edge on the front side; select the point farthest from point C. Then you can get point D.

[0135] Discretize the product boundary and find all points whose Z coordinates of the preceding and following points are larger than their own Z coordinates. Take the two points with the lowest Z coordinates, namely point A and point B.

[0136] Create the initial pressing surface with default length and width and 0 height;

[0137] The top view position uses the X / Y coordinates of point C. The control point on the symmetry plane uses the Z coordinate of point C. The main side control point uses the Z coordinate of point D. Line segment CD is a curve. The outer line segment is tangent. This creates the first control line perpendicular to the symmetry plane.

[0138] Use the X / Y coordinates of point D for the position. The point that intersects the first control line does not move. Calculate the Z coordinate of one of the boundary points based on the vector and set that line segment as a straight line. Set the other side of the line segment to be tangent. This creates a second control line parallel to the symmetry plane.

[0139] Calculate the distance between the pressing surface and the product at this time. Move the pressing surface to the bottom of the product with a fixed distance X from the product, and synchronize the moving value to the height of the pressing surface. The design of the X-direction bending pressing surface is completed.

[0140] In this embodiment, step S329 includes:

[0141] The two endpoints of the first projection line YPC are used as the first endpoint and the second endpoint;

[0142] Traversing the first projection line YPC, removing its invalid line segments, and obtaining a new first projection line YPC'; specifically comprising:

[0143] Starting from the first end point of the first projection line YPC, search for a line segment whose tangent direction forms an obtuse angle with the X-axis, take it as the first invalid line segment, and remove it from the first projection line YPC to obtain YPC1;

[0144] Start searching from the first endpoint, find the first downward cusp, calculate the distance between the cusp and the first endpoint, and if the distance is less than a predetermined value, remove the second invalid line segment between the cusp and the first endpoint to obtain YPC2;

[0145] Start searching from the second endpoint, find the first downward cusp, calculate the horizontal distance between the cusp and the second endpoint, if the horizontal distance is less than 1 / 8 YPC horizontal width, remove the third invalid line segment between the cusp and the second endpoint, and get YPC3;

[0146] YPC3 is smoothed to obtain a new first projection line YPC'.

[0147] Select five candidate points on YPC' with equal width, and connect the five candidate points in sequence to obtain the first curve segment C1;

[0148] Linearly extend C1 in a direction close to the second end point until it reaches the boundary of the binder surface to obtain an extended line segment;

[0149] Determine whether the extended line segment is upturned:

[0150] If so, adjust the two ends of the extended line segment to the same height;

[0151] If not, determining whether the extended line segment is inclined downward by more than a predetermined angle, and if so, adjusting the downwardly inclined end of the extended line segment to the predetermined angle;

[0152] Calculate the surface tangent line V1 of the cover according to the intersection of the cover boundary and the symmetry plane;

[0153] Extend the extended line segment in a direction close to the first end point and parallel to V1, and adjust the extended line segment again according to the relative position relationship between V1 and the Y axis to obtain a cross-sectional line of the binder surface;

[0154] Calculate the current distance between the pressing surface and the cover, move the pressing surface to below the cover, set the distance between the pressing surface and the cover to x, and update the moved distance value to the height of the pressing surface.

[0155] Take the outer panel of the cover as an example:

[0156] Starting from the windshield end point of the YPC, there is an invalid line segment whose tangent is at an obtuse angle to the +X axis. This segment is removed. That is, the reverse part of the windshield end of the YPC is removed to obtain the YPC1.

[0157] Starting from the windshield end point of YPC1, find the first downward-pointing point. Calculate the distance between the point and the two end points of YPC1. If the point is close to the windshield end point, remove the invalid line segment between the point and the windshield end point. In other words, remove the upturned part of the windshield end of YPC1 to get YPC2.

[0158] Find the first downward point from the end point of the YPC2 front side. Calculate the horizontal distance between the point and the end point of the YPC2 front side. If the distance is less than 1 / 8 of the YPC horizontal width, remove the invalid line segment between the point and the end point of the front side. That is, remove the upturned part of the YPC2 front end to get the YPC3.

[0159] YPC3 is smoothed to obtain YPC'.

[0160] Select 5 points of equal width on the YPC', record the point closest to the windshield end as point3, and the point closest to the front end as point4.

[0161] Connect the five points in sequence to obtain curve C1.

[0162] Extend the C1 head end linearly to the boundary of the pressing surface to obtain point 5.

[0163] Connect points point4 and point5 to form a line segment, and determine whether the line segment is upturned:

[0164] If yes, adjust point4 and point5 to be equal in height.

[0165] If not, determine whether the line segment slopes downward by more than a specified angle? For example, 10°:

[0166] If so, adjust the height of point5 so that the downward slope of the line segment is the specified angle.

[0167] If not, calculate the product surface tangent V1 at the intersection of the product boundary and the symmetry plane on the windshield side.

[0168] Determine the relationship between V1 and the Y axis:

[0169] If V1 is not tilted upward or downward, copy point3 and move it along V1 to the boundary of the pressing surface to obtain point6.

[0170] If V1 slopes downward by more than 10°, the line segments point3point6 are made tangent.

[0171] If V1 is tilted upward, then V1=-Y.

[0172] The cross-section line of the pressing surface is formed based on 5 points and point5 and point6.

[0173] Adjust the height of the pressing surface and find out the distance between the pressing surface and the product. Move the pressing surface to the bottom of the product with a fixed distance X from the product, and synchronize the moving value to the height of the pressing surface. The design of the Y-axis curved pressing surface is completed.

[0174] Specifically, in this embodiment, the full parameter section line template is as follows Figure 3 As shown in the figure, it is mainly divided into the product attachment area connected to the product surface, the concave rib area and the convex rib area that play a transition role, and the pressing extension area connected to the pressing surface. Based on the full parameter template and combined with the production process design requirements, several types of sub-section line templates are derived. The process supplement design process is as follows Figure 4 As shown, it mainly includes arranging section lines, building grids, and creating process supplementary surfaces.

[0175] In this embodiment, when performing process supplementary design, the product boundary is first partitioned, and then the cross-sectional lines are shaped according to the partition characteristics and process requirements.

[0176] Specifically, in one embodiment of the present invention, step S33 includes:

[0177] S331: extracting boundary feature points using a feature extraction algorithm to obtain a first boundary feature point set P1 of the cover, selecting the middle point of two first boundary feature points from adjacent feature points of the first boundary feature point set P1 as a new feature point to be added to the set, and obtaining a second boundary feature point set P2;

[0178] S332: partitioning the second boundary feature point set P2 based on a boundary partitioning method to obtain five boundary partitions, namely, a front bumper area, a headlight area, a fender area, a transition area, and a windshield area;

[0179] S333: Calculate a parting line position point set P3 for five boundary partitions according to a parting line calculation method;

[0180] S334: traversing the boundary partitions, generating a partition curve group based on the second boundary feature points in the boundary partitions and the shape features of the boundary partitions, offsetting outwards in sequence to obtain a biased curve group, performing transition connection and corner smoothing on sequentially connected curves in the biased curve group, and obtaining a parting line;

[0181] S335: Expand the second boundary feature point set P2 with empirical points to form a candidate insertion point set P4 for section lines, arrange section lines according to the candidate insertion point set P4 for section lines, construct a grid according to the section lines and parting lines, and create a process supplementary surface according to the grid.

[0182] Boundary partitioning methods include:

[0183] Starting from the second boundary feature point, look for the turning point of curvature change on both sides as the partition point;

[0184] The two end points of the boundary are connected with the nearest partition point to form a front protection zone and a windshield zone;

[0185] Find the next two nearest partition points from the front protection area toward the border to form the headlight area;

[0186] Find the next nearest partition point from the headlight area toward the boundary as an end point of the fender area;

[0187] Find a point along the boundary whose tangent direction is parallel to the symmetry plane, and use this point as the partition endpoint between the fender area and the windshield area, that is, the other endpoint of the fender area;

[0188] The fender area is formed according to the two end points of the fender area, and a transition area is between the fender area and the windshield area.

[0189] Parting line calculation methods include:

[0190] According to the side of the cover member located in the windshield area as the windshield side, and according to the curvature of the windshield side and the boundary of the cover member, a first arc and a second arc are constructed;

[0191] Constructing a covering line of the covering member according to the first arc and the second arc, wherein the first arc, the second arc and the covering line form a closed figure and completely cover the covering member;

[0192] Rounding the first arc, the second arc and the covering line;

[0193] The tail points of the cross-section line at the second boundary feature point set P2 are calculated according to the cross-section line rule, and the parting line is located outside all the tail points.

[0194] See also Figure 5 , Figure 6 and Figure 7 Taking the cover outer panel as an example, the process supplement design process includes:

[0195] (1) Searching for boundary feature points: The Douglas–Peucke (DP) algorithm is used to search for boundary feature points of the product. The DP algorithm uses polygons to approximate contour lines. A discrete point set with a certain precision on the boundary of the current product is input, and an approximate polygon is constructed for the input discrete point set in a recursive manner, such as Figure 5 The original boundary shown in a, the recursive termination condition is that all Euclidean distances from the current approximate polygon to the discrete point set of the product boundary are less than the given error value, and the output is the boundary feature point set P1 of the product, as shown in Figure 5As shown in b. Since the feature point sets found by the DP algorithm are mostly located at the places with large curvature of the boundary curve and at the corners, the length of the flange surface line is usually short, which has an impact on the subsequent process, the intermediate curve parameter points of the adjacent feature points are added as new feature points to the set, and the new feature point set P2 is output, as shown in Figure 5 As shown in c.

[0196] (2) Boundary partitioning: partition the feature point set based on product feature rules. The partitioning method is to project the boundary curve along the stamping direction onto a two-dimensional plane perpendicular to the stamping direction, and then obtain the two-dimensional enclosing box of the projection line. Then, using the required enclosing box as a reference, find the partition points based on the coordinate features of the feature point set to determine the boundary partition. Figure 5 As shown in Figure d, the product boundary is divided into five areas: front guard area, headlight area, fender area, transition area and windshield area.

[0197] The rule for finding the partition points is: find the turning point of curvature change on both sides according to the feature points. According to the feature points, find points parallel to the tangent and symmetry planes along the product boundary as the partition endpoints close to the windshield area of ​​the fender area.

[0198] (3) Calculate the position of the parting line: According to the empirical rules, the modeling rules are given to each partition, and the template section line type that meets the process requirements of the partition is preset. Some key parameters, such as the punch radius and the die radius, are assigned empirical values. Then, the characteristic points in each partition are traversed. The starting constraint is that the starting direction of the section line is consistent with the tangent direction of the product surface here. The intermediate constraint is the assembly and constraint relationship between the pre-assigned parameter values. The end constraint is that the point falls on the pressing surface, such as Figure 6 As shown, the parting line position point set P3 is calculated.

[0199] (4) Constructing the parting line: Traverse the partitions, generate a partition curve group based on the characteristic points and shape features of the partitions, and offset them outwards to obtain the offset curve group. It is required that each offset curve in the offset curve group is just outside the parting line position point calculated in (3), which is beneficial to reduce the process supplementary surface area and improve material utilization. The curves that are connected sequentially in the offset curve group are transitionally connected and the corners are smoothed to obtain the parting line.

[0200] like Figure 7 As shown, Figure 7 A1, B1, A2, and B2 are all feature points. According to the curvature of the windshield side, the upper and lower arcs are obtained. The left and right straight line segments are parallel to the symmetry plane within the range of ±2°, and the closed area formed by the upper and lower arcs is the smallest. Chamfer the upper and lower arcs and the left and right straight line segments. According to the cross-section line rule, calculate the end point of the cross-section line at the feature point to ensure that the parting line is just outside all the end points.

[0201] (5) Constructing process supplementary surfaces: The point set P2 obtained by the DP algorithm and parameter interpolation can partially represent the geometric features of the product boundary. In order to construct a process supplement with better effect, some experience points are added and screened based on the empirical rules on the basis of the point set P2 to form the candidate insertion point set P4 of the section line. The process supplement is created according to the above-mentioned process of arranging the section line-building the grid-creating the process supplementary surface.

[0202] In this embodiment, the types of cross-section lines include Bar cross-section lines and platform cross-section lines. Both the platform cross-section line and the Bar cross-section line are derived from Figure 3 The full-parameter section line template uses a platform type section line to better maintain the continuity of the process supplementary surface and the product boundary surface, which is beneficial to material flow; the use of a Bar section line can make the drawing more complete.

[0203] Specifically, Figure 8 As shown, the windshield area uses the Bar type section line, and other areas use the platform type section line. The platform type section line must ensure that the length of the side wall straight line segment is ≥5. If there is not enough space, it will become Figure 8 Upper right shape.

[0204] It should be noted that when the instance mold surface design is extracted as an instance template and stored in the library, in order to optimize the template reuse effect, the instance mold surface design will be extracted as an instance template and split into several partition templates according to the partition, and stored in the template library at different data granularities. In subsequent use, the instance template can be used as a whole or in part or all of the instance template in the form of partitions. This design method makes the use and reuse of templates more flexible. The templates with high similarity in the template library are automatically retrieved and calculated based on instances and partitions, and the similarity between the instance template and the partition template is comprehensively evaluated, and the template with higher similarity and more suitable inheritance granularity is selected.

[0205] If a matching template can be retrieved in the template library for process supplement design, after the template granularity is determined and the template is bound, the current process supplement template-driven design will be carried out with reference to the bound template. The template mainly stores three types of data: section line parameters, product boundary parameters, and parting line parameters. These data are divided into relative data that depends on coordinate expression and absolute data that does not depend on coordinate system expression. Before template inheritance, the relative coordinates of points and vectors in the template need to be transformed based on the bound template and the coordinate system of the current product, and then template inheritance is performed. The input data of template inheritance is the transformed relative data and the original absolute data, and the output is the parting line and section line constructed based on the intermediate data. The process supplement is created according to the process of arranging section lines-building grids-creating process supplement surfaces described above. After the design of the new instance die surface is completed, it will be automatically extracted as a new instance template and subordinate partition templates, and automatically accumulated in the template library to complete the automatic reuse and accumulation of knowledge.

[0206] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A knowledge-driven automobile panel die surface design method, characterized in that: The steps include: S1: build template library; S2: Obtain the cover, search in the template library according to the cover, and obtain the target template; S3: Combined with the target template, the die surface design of the cover is carried out, including stamping direction design, pressing surface design and process supplementary design: S31: The stamping direction design is designed according to the stamping direction in the target template; S32: The blanking surface is designed according to the stamping direction and the boundary and contour information of the cover; S33: Process supplementary design is designed according to the boundary, parting line and section line of the cover; The template library includes abstract templates, instance templates and partition templates, where the partition template is obtained by dividing the instance template into regions. After the die surface design of the cover is completed, it is automatically accumulated in the template library; the matching template is selected through similarity matching for template-driven design; template accumulation and reuse of templates with different data granularities are supported; the template library performs lightweight expression and storage of die surface design data; After obtaining the new cover, if a template with high similarity is retrieved, the template library is used; if the retrieved template is not similar, the rule is used. The specific implementation process is as follows: (a) Keyword matching: The system automatically searches for abstract templates matching the input keywords in the template library based on product name, material, and product feature keywords. The abstract templates are obtained by classifying parts. Each abstract template integrates the rules of process mode and stamping coordinate system and is automatically inherited in the subsequent design process. (b) Similarity retrieval and matching: The main evaluation indicators of similarity are: first, the similarity of the discrete point set of the three-dimensional contour curve of the cover, which expresses the similarity of the boundary of the cover product; second, the similarity of the external tangent set of the cover contour surface, which expresses the similarity of the surface at the contour of the cover product; based on the similarity retrieval and matching methods of different granularities, according to the overall or local similarity of the cover, the adaptive granularity is reasonably selected for similarity retrieval and matching; (c) Intelligent design of stamping direction adopts the design method of matching abstract templates to inherit stamping direction and utilizes the similarity of product surface features; (d) Intelligent design of the blanking surface adopts a hybrid example- and rule-driven design approach, combining the matching example template to inherit the blanking surface data with the automatic generation of the blanking surface based on empirical rules, comprehensively evaluating the template similarity and the automatic generation effect and making a selection; (e) The intelligent design of process supplement also adopts a hybrid design method driven by instances and rules, combining three methods: matching instance templates to inherit process supplement data, matching partition templates to inherit process supplement data, and automatically generating process supplements based on experience knowledge.

2. The knowledge-driven automobile panel die surface design method according to claim 1, characterized in that: Step S32 includes: S321: determining a stamping coordinate system according to the stamping direction, and projecting the boundary of the cover onto the yoz plane along the x-axis of the stamping coordinate system to obtain a first projection line YPC; S322: equally divide the first projection line YPC, obtain the middle part of the first projection line YPC, search for the lowest point on the first projection line YPC, and determine whether the lowest point is in the middle part of the first projection line YPC, if so, execute step S328, if not, execute step S323; S323: Find two target low points P1 and P2 on the first projection line YPC, connect P1 and P2 to obtain a first straight line L1, and use the line segment between P1 and P2 on the first projection line YPC as a first curve S1; S324: Calculate the vertical distance between every two points on the first straight line L1 and the first curve S1, and select the largest first vertical distance D1; S325: Projecting the boundary of the cover onto the xoz plane along the y-axis of the stamping coordinate system to obtain a second projection line XPC; S326: Obtain the symmetry plane of the second projection line XPC, and calculate the minimum second vertical distance D2 from the lowest point on the second projection line XPC to the intersection of the second projection line XPC and the symmetry plane; S327: Determine whether D1≤D2. If yes, execute step S328; if no, execute step S329; S328: determining that the cover is bent in the X direction, and generating an X-direction bent pressing surface; S329: Determine that the cover is bent in the Y direction, and generate a Y-direction bent pressing surface.

3. The knowledge-driven automobile panel die surface design method according to claim 2, characterized in that: Step S328 includes: Determine the product surface, boundary, symmetry surface and height value of the cover; Draw a second straight line perpendicular to the symmetry plane at the intersection of the boundary and the symmetry plane respectively, determine the front side of the cover according to the number of intersections of the second straight line and the boundary, and take the most convex point of the front side as point C; Make a minimum enclosing box of the boundary on the top view of the cover, take the side of the minimum enclosing box corresponding to the front side as the first side, take the side adjacent to the first side as the second side, select the edge points of the boundary located on the front side as the first candidate points, calculate the vertical distances between the first candidate points and the first side and the second side respectively, obtain the first distance and the second distance, select the corresponding first candidate points whose first distance is less than the second distance as the second candidate points, calculate the distance between the second candidate point and point C, and select the second candidate point with the farthest distance as point D; Discrete the points on the boundary and search for the two points with the lowest z coordinates as points A and B; Create an initial pressing surface with preset length and width and 0 height; Create a first control line perpendicular to the symmetry plane. The first control line is tangent to the front side, and the tangent point is point C. Create a second control line parallel to the symmetry plane, the second control line intersects the first control line, and point D is located on the second control line; Adjust the shape and size of the binder surface according to the first control line and the second control line; Calculate the current distance between the pressing surface and the cover, move the pressing surface to below the cover, set the distance between the pressing surface and the cover to x, and update the moved distance value to the height of the pressing surface.

4. The knowledge-driven automobile panel die surface design method according to claim 2, characterized in that: Step S329 includes: The two endpoints of the first projection line YPC are used as the first endpoint and the second endpoint; Traverse the first projection line YPC, remove its invalid line segments, and obtain a new first projection line YPC'; Select five candidate points on YPC' with equal width, and connect the five candidate points in sequence to obtain the first curve segment C1; Linearly extend C1 in a direction close to the second end point until it reaches the boundary of the binder surface to obtain an extended line segment; Determine whether the extended line segment is upturned: If so, adjust the two ends of the extended line segment to the same height; If not, determining whether the extended line segment is inclined downward by more than a predetermined angle, and if so, adjusting the downwardly inclined end of the extended line segment to the predetermined angle; Calculate the surface tangent line V1 of the cover according to the intersection of the cover boundary and the symmetry plane; Extend the extended line segment in a direction close to the first end point and parallel to V1, and adjust the extended line segment again according to the relative position relationship between V1 and the Y axis to obtain a cross-sectional line of the binder surface; Calculate the current distance between the pressing surface and the cover, move the pressing surface to below the cover, set the distance between the pressing surface and the cover to x, and update the moved distance value to the height of the pressing surface.

5. The knowledge-driven automobile panel die surface design method according to claim 4, characterized in that: The first projection line YPC is traversed, and its invalid line segments are removed to obtain a new first projection line YPC', including: Starting from the first end point of the first projection line YPC, search for a line segment whose tangent direction forms an obtuse angle with the X-axis, take it as the first invalid line segment, and remove it from the first projection line YPC to obtain YPC1; Start searching from the first endpoint, find the first downward cusp, calculate the distance between the cusp and the first endpoint, and if the distance is less than a predetermined value, remove the second invalid line segment between the cusp and the first endpoint to obtain YPC2; Start searching from the second endpoint, find the first downward cusp, calculate the horizontal distance between the cusp and the second endpoint, if the horizontal distance is less than 1 / 8 YPC horizontal width, remove the third invalid line segment between the cusp and the second endpoint, and get YPC3; YPC3 is smoothed to obtain a new first projection line YPC'.

6. The knowledge-driven automobile panel die surface design method according to claim 1, characterized in that: Step S33 includes: S331: extracting boundary feature points using a feature extraction algorithm to obtain a first boundary feature point set P1 of the cover, selecting the middle point of two first boundary feature points from adjacent feature points of the first boundary feature point set P1 as a new feature point to be added to the set, and obtaining a second boundary feature point set P2; S332: partitioning the second boundary feature point set P2 based on a boundary partitioning method to obtain five boundary partitions, namely, a front bumper area, a headlight area, a fender area, a transition area, and a windshield area; S333: Calculate a parting line position point set P3 for five boundary partitions according to a parting line calculation method; S334: traversing the boundary partitions, generating a partition curve group based on the second boundary feature points in the boundary partitions and the shape features of the boundary partitions, offsetting outwards in sequence to obtain a biased curve group, performing transition connection and corner smoothing on sequentially connected curves in the biased curve group, and obtaining a parting line; S335: Expand the second boundary feature point set P2 with empirical points to form a candidate insertion point set P4 for section lines, arrange section lines according to the candidate insertion point set P4 for section lines, construct a grid according to the section lines and parting lines, and create a process supplementary surface according to the grid.

7. The knowledge-driven automobile panel die surface design method according to claim 6, characterized in that: Boundary partitioning methods include: Starting from the second boundary feature point, look for the turning point of curvature change on both sides as the partition point; The two end points of the boundary are connected with the nearest partition point to form a front protection zone and a windshield zone; Find the next two nearest partition points from the front protection area toward the border to form the headlight area; Find the next nearest partition point from the headlight area toward the boundary as an end point of the fender area; Find a point along the boundary whose tangent direction is parallel to the symmetry plane, and use this point as the partition endpoint between the fender area and the windshield area, that is, the other endpoint of the fender area; The fender area is formed according to the two end points of the fender area, and a transition area is between the fender area and the windshield area.

8. The knowledge-driven automobile panel die surface design method according to claim 6, characterized in that: Parting line calculation methods include: According to the side of the cover member located in the windshield area as the windshield side, and according to the curvature of the windshield side and the boundary of the cover member, a first arc and a second arc are constructed; Constructing a covering line of the covering member according to the first arc and the second arc, wherein the first arc, the second arc and the covering line form a closed figure and completely cover the covering member; Rounding the first arc, the second arc and the covering line; The tail points of the cross-section line at the second boundary feature point set P2 are calculated according to the cross-section line rule, and the parting line is located outside all the tail points.

9. The knowledge-driven automobile panel die surface design method according to claim 8, characterized in that: The section line rule is: the windshield area uses the Bar type section line, and other areas use the platform type section line.

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