Automobile body part constraint relation analysis method based on three-dimensional digital model

Abstract

The invention discloses an automobile body part constraint relation analysis method based on a three-dimensional digital model, and relates to the technical field of computer aided design and manufacturing. The method comprises the following steps: S1, identifying a minimum part unit of a final assembly process; s2, a vehicle body is automatically partitioned, and parts are mapped to corresponding final assembly stations; s3, analyzing a constraint relationship between the partition parts; and S4, performing hierarchical extraction on the parts based on the constraint relationship analyzed in the step S3, and generating an assembly sequence. According to the method, through automatic partitioning, multi-direction space relation analysis and cyclic constraint processing, efficient and accurate derivation of the assembly sequence of the parts of the vehicle body is achieved.

Description

Technical Field

[0001] This invention relates to the field of computer-aided design and manufacturing technology, and in particular to a method for analyzing constraint relationships of automotive body components based on a three-dimensional digital model. Background Technology

[0002] In the final assembly process planning of automobile manufacturing, determining the assembly sequence (i.e., constraints) of internal vehicle components is a crucial step. Traditional methods rely on the step-by-step disassembly and analysis of the actual vehicle, which is inefficient, costly, and cannot be done in advance during the design phase.

[0003] Currently, there is no digital method for extracting the assembly sequence of body parts. Therefore, there is an urgent need in this field for a technical solution that can automatically, accurately, and efficiently analyze the constraint relationships of body parts and provide reliable input for final assembly process planning during the design phase. Summary of the Invention

[0004] In view of this, the present invention aims to propose a method for analyzing the constraint relationships of automotive body components based on a three-dimensional digital model, in order to overcome the shortcomings of the prior art.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A method for analyzing constraint relationships of automotive body components based on a three-dimensional digital model includes the following steps:

[0007] Step S1: Identify the smallest part unit in the final assembly process;

[0008] Step S2: The vehicle body is automatically partitioned, and the parts are mapped to the corresponding final assembly stations;

[0009] Step S3: Analyze the constraint relationships between the parts in each partition;

[0010] Step S4: Extract the part hierarchy based on the constraint relationships analyzed in step S3 and generate an assembly sequence.

[0011] Furthermore, in step S1, the model nodes are reorganized into the smallest part units corresponding to the final assembly line through manual adjustment or automatic software analysis. The number of parts in the model is denoted as... The parts list is recorded as .

[0012] Furthermore, in step S2, the vehicle body is divided into an engine front compartment, a rear compartment, a passenger compartment, a chassis, and four tire areas.

[0013] The specific mapping relationship is as follows:

[0014] Engine front compartment → Front work station;

[0015] Rear cabin → Rear workstation;

[0016] Crew compartment → Determine whether it is the left or right workstation based on the part's center of gravity;

[0017] Chassis → Bottom work station;

[0018] Four tires → bottom work station.

[0019] Furthermore, step S2 includes the following steps:

[0020] Step 2.1: Determining the partition boundaries and determining part ownership:

[0021] Selecting partition boundary parts: Selecting a portion of the parts located at the outer boundary of the partition as the boundary reference;

[0022] Constructing the partitioned convex hull: Using the 3D convex hull algorithm in the Qhull library, calculate the bounding volume of the boundary part, obtain its triangular mesh data, and denot it as... ;

[0023] calculate The axial bounding box is denoted as:

[0024] ;

[0025] ;

[0026] in, Indicates the minimum and maximum vertices of the bounding box;

[0027] Package relationship determination:

[0028] The entire model is then processed into three-dimensional voxels.

[0029] Analyze along the positive directions of the X, Y, and Z axes respectively. Other parts The occlusion relationship;

[0030] If the observations from all three directions indicate Obstruction Then determine pack and will It should be assigned to this partition;

[0031] Step 2.2 Automatic partition analysis and optimization;

[0032] To further accurately determine the boundaries between parts and partitions The following judgment process is used to determine the relationship:

[0033] Obtain the bounding box:

[0034] Parts enclosure:

[0035] Bounding box:

[0036] Preliminary comparison:

[0037] If the part's bounding box is completely inside the boundary bounding box, it is considered an enclosing relationship;

[0038] If the part bounding box is completely outside the boundary bounding box, it is considered unrelated;

[0039] If the part bounding box intersects with the boundary bounding box, proceed to step S3 for detailed analysis.

[0040] Furthermore, the part constraint relationship analysis in step S3 includes the following steps:

[0041] Step 3.1 Extraction of multi-directional constraint relationships;

[0042] Step 3.2 Fine projection analysis, used for coplanar cases within the same voxel;

[0043] Step 3.3: Processing loop constraints.

[0044] Furthermore, the process for extracting multi-directional constraint relationships in step 3.1 is as follows:

[0045] Based on the defined partitions, analyze the constraint relationships between all parts in a unified manner;

[0046] By analyzing the voxels of the entire model, two workpieces are analyzed in a specified direction. and ;

[0047] Obstruction :Record ;

[0048] pack :Record ;

[0049] collision Record collision relationships Users need to manually specify the constraint relationship between the two parts;

[0050] Analysis direction setting:

[0051] Front area: The main direction is the negative X-axis, and the auxiliary direction is the Y-axis, from both sides to the middle;

[0052] Rear area: The main direction is the positive X-axis direction;

[0053] Left zone: The main direction is the Z-axis, from both sides to the middle;

[0054] Right zone: The main direction is the Z-axis, from both sides to the middle;

[0055] Bottom region: The main direction is the negative Z-axis direction;

[0056] Constraint Relationship Fusion Algorithm:

[0057] set up For a collection of partitioned parts, The occlusion coefficient threshold is used as a variable parameter and is an external input.

[0058] Remove parts belonging to the body-in-white and obtain... List;

[0059] For each part If in Skip if it's in the middle:

[0060] a. Analyze the main direction constraints;

[0061] b. Analyze auxiliary direction constraints;

[0062] c. Record the number of occluded voxels, denoted as q;

[0063] d. Calculate the shading coefficient Then record the occlusion relationship;

[0064] Merge constraints:

[0065] When the primary and secondary directions are inconsistent, the primary direction shall prevail.

[0066] When the primary direction is a package and other directions are not packages, the package relationship is deleted in the primary direction;

[0067] If there is mutual occlusion, but only a single occlusion relationship exists in a certain direction, then record that single relationship.

[0068] Furthermore, step 3.2, fine projection analysis, is used for the case of coplanarity within the same voxel;

[0069] When the triangular facets of two parts appear in the same voxel, a detailed projection analysis is required.

[0070] set up:

[0071] : Analyze the direction vector;

[0072] : Projected plane point, default is ;

[0073] Two parts to be analyzed;

[0074] They are respectively The triangular sets of the two parts respectively contain A triangle;

[0075] Vertex projection:

[0076] The triangles Its vertex , Its projection point is:

[0077] ;

[0078] ;

[0079] ;

[0080] The The triangle in B Its vertex , Its projection point is:

[0081] ;

[0082] ;

[0083] ;

[0084] Point containment detection and depth comparison:

[0085] Use the centroid coordinate method to check Is it in Inside the triangle formed:

[0086] ;

[0087] Calculate the location and depth of the intersection point in the original space:

[0088] ;

[0089] in, This represents a depth value, used to compare relationships between different points.

[0090] like Then determine Obstruction ;right Repeat this test;

[0091] If none of the vertices are inside the other triangle, then edge-to-edge intersections are detected, and the relationship between the edges is compared based on the depth of the intersection points.

[0092] Furthermore, step 3.3 involves handling cyclic constraints:

[0093] Detect cycles in all constraints;

[0094] The loop is untied by identifying all nodes in the loop and manually or automatically deleting some constraints according to preset rules.

[0095] Furthermore, in step S4, the hierarchy of the internal parts of the five partitions (front, back, left, right, and bottom) is calculated and the hierarchy is assigned.

[0096] By integrating the hierarchical relationships of all partitions, a graph structure describing the overall constraint relationships of body parts is constructed, providing accurate assembly sequence input for final assembly process planning.

[0097] Compared with the prior art, the present invention has the following advantages:

[0098] The method for analyzing the constraint relationship of automotive body parts based on a three-dimensional digital model, as described in this invention, achieves efficient and accurate derivation of the assembly sequence of body parts through automatic partitioning, multi-directional spatial relationship analysis, and cyclic constraint processing. Attached Figure Description

[0099] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0100] Figure 1 This is a flowchart of the method for analyzing the constraint relationships of automotive body components based on a three-dimensional digital model, as described in an embodiment of the present invention. Detailed Implementation

[0101] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0102] In addition, the X direction, Y direction, and Z direction mentioned in the embodiments of the present invention refer to the X-axis direction of the input 3D model coordinate system, the Y direction of the input 3D model coordinate system, and the Z direction of the input 3D model coordinate system.

[0103] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "back," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0104] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0105] A method for analyzing constraint relationships of automotive body components based on a three-dimensional digital model includes the following steps:

[0106] Step S1: Identify the smallest part unit in the final assembly process;

[0107] Step S2: The vehicle body is automatically partitioned, and the parts are mapped to the corresponding final assembly stations;

[0108] Step S3: Analyze the constraint relationships between the parts in each partition;

[0109] Step S4: Extract the part hierarchy based on the constraint relationships analyzed in step S3 and generate the assembly sequence.

[0110] In step S1, the model nodes are reorganized into the smallest part units corresponding to the final assembly line through manual adjustment or automatic software analysis. The number of parts in the model is denoted as... The parts list is recorded as .

[0111] In step S2, the vehicle body is divided into the front engine compartment, rear compartment, passenger compartment, chassis, and four tire areas;

[0112] The specific mapping relationship is as follows:

[0113] Engine front compartment → Front work station;

[0114] Rear cabin → Rear workstation;

[0115] Crew compartment → Determine whether it is the left or right workstation based on the part's center of gravity;

[0116] Chassis → Bottom work station;

[0117] Four tires → bottom work station.

[0118] Step S2 includes the following steps:

[0119] Step 2.1: Determining the partition boundaries and determining part ownership:

[0120] Selecting partition boundary parts: Selecting a portion of the parts located at the outer boundary of the partition as the boundary reference;

[0121] Constructing the partitioned convex hull: Using the 3D convex hull algorithm in the Qhull library, calculate the bounding volume of the boundary part, obtain its triangular mesh data, and denot it as... ;

[0122] calculate The axial bounding box, i.e., the AABB bounding box, is denoted as:

[0123] ;

[0124] ;

[0125] in, Indicates the minimum and maximum vertices of the bounding box;

[0126] Package relationship determination:

[0127] The entire model is then processed into three-dimensional voxels.

[0128] Analyze along the positive directions of the X, Y, and Z axes respectively. Other parts The occlusion relationship;

[0129] If the observations from all three directions indicate Obstruction Then determine pack and will It should be assigned to this partition;

[0130] Step 2.2 Automatic partition analysis and optimization;

[0131] To further accurately determine the boundaries between parts and partitions The following judgment process is used to determine the relationship:

[0132] Obtain the bounding box:

[0133] Parts enclosure:

[0134] Bounding box:

[0135] Preliminary comparison:

[0136] If the part's bounding box is completely inside the boundary bounding box, it is considered an enclosing relationship;

[0137] If the part bounding box is completely outside the boundary bounding box, it is considered unrelated;

[0138] If the part bounding box intersects with the boundary bounding box, proceed to step S3 for detailed analysis.

[0139] Step S3, the part constraint relationship analysis, includes the following steps:

[0140] Step 3.1 Extraction of multi-directional constraint relationships;

[0141] Step 3.2 Fine projection analysis, used for coplanar cases within the same voxel;

[0142] Step 3.3: Processing loop constraints.

[0143] Step 3.1 The process for extracting multi-directional constraint relationships is as follows:

[0144] Based on the defined partitions, analyze the constraint relationships between all parts in a unified manner;

[0145] By analyzing the voxels of the entire model, two workpieces are analyzed in a specified direction. and ;

[0146] Obstruction :Record ;

[0147] pack :Record ;

[0148] collision Record collision relationships Users need to manually specify the constraint relationship between the two parts;

[0149] Analysis direction setting:

[0150] Front area: The main direction is the negative X-axis, and the auxiliary direction is the Y-axis, from both sides to the middle;

[0151] Rear area: The main direction is the positive X-axis direction;

[0152] Left zone: The main direction is the Z-axis, from both sides to the middle;

[0153] Right zone: The main direction is the Z-axis, from both sides to the middle;

[0154] Bottom region: The main direction is the negative Z-axis direction;

[0155] Constraint Relationship Fusion Algorithm:

[0156] set up For a collection of partitioned parts, The occlusion coefficient threshold is used as a variable parameter and is an external input.

[0157] Remove parts belonging to the body-in-white and obtain... List;

[0158] For each part If in Skip if it's in the middle:

[0159] a. Analyze the main direction constraints;

[0160] b. Analyze auxiliary direction constraints;

[0161] c. Record the number of occluded voxels, denoted as q;

[0162] d. Calculate the shading coefficient Then record the occlusion relationship;

[0163] Merge constraints:

[0164] When the primary and secondary directions are inconsistent, the primary direction shall prevail.

[0165] When the primary direction is a package and other directions are not packages, the package relationship is deleted in the primary direction;

[0166] If there is mutual occlusion, but only a single occlusion relationship exists in a certain direction, then record that single relationship.

[0167] Step 3.2 Fine projection analysis, i.e., for the case of coplanarity within the same voxel;

[0168] When the triangular facets of two parts appear in the same voxel, a detailed projection analysis is required.

[0169] set up:

[0170] : Analyze the direction vector;

[0171] : Projected plane point, default is ;

[0172] Two parts to be analyzed;

[0173] They are respectively The triangular sets of the two parts respectively contain A triangle;

[0174] Vertex projection:

[0175] triangles Its vertex , Its projection point is:

[0176] ;

[0177] ;

[0178] ;

[0179] The triangle in B Its vertex , Its projection point is:

[0180] ;

[0181] ;

[0182] ;

[0183] Point containment detection and depth comparison:

[0184] Use the centroid coordinate method to check Is it in Inside the triangle formed:

[0185] ;

[0186] Calculate the location and depth of the intersection point in the original space:

[0187] ;

[0188] in, This represents a depth value, used to compare relationships between different points.

[0189] like Then determine Obstruction ;right Repeat this test;

[0190] If none of the vertices are inside the other triangle, then edge-to-edge intersections are detected, and the relationship between the edges is compared based on the depth of the intersection points.

[0191] Step 3.3 Cyclic constraint handling:

[0192] Detect cycles in all constraints, such as By identifying all nodes in the loop and manually or automatically deleting some constraints according to preset rules, such as deleting... To break the loop.

[0193] Step S4 calculates the hierarchy of the internal parts for each of the five partitions: front, back, left, right, and bottom, and assigns the hierarchy accordingly.

[0194] By integrating the hierarchical relationships of all partitions, a graph structure describing the overall constraint relationships of body parts is constructed, providing accurate assembly sequence input for final assembly process planning.

[0195] This embodiment relates to a method for analyzing the constraint relationships of automotive body parts based on a three-dimensional digital model. By automatically partitioning the three-dimensional model, judging spatial relationships in multiple directions, and processing cyclic constraints, it can efficiently generate assembly sequences during the design phase, completely eliminating the reliance on physical disassembly and significantly improving the efficiency and digitalization level of process planning.

[0196] 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 within the protection scope of the present invention.

Claims

1. A method for analyzing constraint relationships of automobile body parts based on a three-dimensional digital model, characterized by: The method comprises the following steps: Step S1: identifying the minimum part unit of the assembly process; Step S2: automatically partitioning the vehicle body and mapping the parts to corresponding assembly stations; Step S3: analyzing the constraint relationship between parts in each partition; Step S4: extracting the part hierarchy based on the constraint relationship analyzed in step S3 and generating an assembly sequence.

2. The method according to claim 1, wherein: The model nodes are reorganized into minimum part units corresponding to the general assembly production line by manual adjustment or software automatic analysis in the step S1, and the number of parts in the model is recorded as , and the part list is recorded as .

3. The method according to claim 2, wherein: In step S2, the vehicle body is divided into an engine front compartment, a rear compartment, a passenger compartment, a chassis, and four tire areas; The specific mapping relationship is as follows: Engine front compartment→front station; Rear compartment→rear station; Passenger compartment→left station or right station according to the part centroid; Chassis→bottom station; Four tires→bottom station.

4. The method according to claim 3, wherein: Step S2 comprises the following steps: Step 2.1: partition boundary determination and part attribution judgment: Selecting partition boundary parts: selecting some parts located on the peripheral boundary of the partition as boundary references; Constructing the partitioned convex hull: using the three-dimensional convex hull algorithm in the Qhull library, the bounding volume of the boundary part is calculated, and the triangular mesh data thereof is obtained, denoted as ; Computing the axial bounding box, denoted as: ； ； wherein represent the bounding box minimum and maximum vertices; Enclosure relationship judgment: Performing three-dimensional voxelization processing on the entire model, Analysis along the positive direction of the X, Y, Z axes, respectively Blocking relationship with other parts ; If the observations from all three directions indicate occlusion , then determine wrapping , and classify into the partition; Step 2.2: automatic analysis and optimization of the partition; To further accurately determine the relationship between the part and the partition boundary the following determination process is adopted: Obtaining a bounding box: Part bounding box: ; Bounding box: ; Preliminary comparison: If the part bounding box is completely inside the boundary bounding box, it is determined to have an enclosure relationship; If the part bounding box is completely outside the boundary bounding box, it is determined to have no relationship; If the part bounding box intersects with the boundary bounding box, proceed to step S3 for detailed analysis.

5. The method according to claim 4, wherein: Step S3: part constraint relationship analysis comprises the following steps: Step 3.1: multi-direction constraint relationship extraction; Step 3.2: detailed projection analysis for coplanar cases in the same voxel; Step 3.3: cyclic constraint processing.

6. The method according to claim 5, wherein: The step 3.1 multi-direction constraint relationship extraction process is as follows: According to the divided partition, uniformly analyze the constraint relationship between all parts; By analyzing voxels of the entire model, two workpieces are analyzed in a specified direction and ; occlusion : record ; parcel : record ; collision : record collision relationship , user has to manually specify constraint relationship of two parts; Analysis direction setting: Front area: main direction is X-axis negative direction, auxiliary direction is Y-axis, from both sides to the middle; Rear area: main direction is X-axis positive direction; Left area: main direction is Z-axis, from both sides to the middle; Right area: main direction is Z-axis, from both sides to the middle; Bottom area: main direction is Z-axis negative direction; Constraint relationship fusion algorithm: Set For partitioned parts collection, For the shielding coefficient threshold, as a variable parameter, external input; obtaining a list of parts belonging to the body-in-white ; For each part , if in skip: a. Analyze the main direction constraint; b. Analyze the auxiliary direction constraint; c. Record the number of occluded voxels, denoted as q; d. Computing the occlusion coefficient then record the occlusion relationship; Merge constraint relationship: When the main and auxiliary directions are inconsistent, the main direction is used as the reference; When the main direction is occluded and other directions are not occluded, the main direction is deleted; If there is mutual occlusion, but there is only a single occlusion relationship in a certain direction, record the single relationship.

7. The method of claim 5, wherein: the step 3.2 is a fine projection analysis for coplanar cases in the same voxel; when the triangular facets of two parts appear in the same voxel, the fine projection analysis is needed; let: : analyze direction vector; : projection plane point, default is ; : two parts to be analyzed; : are respectively a triangle set of two parts, respectively containing triangles; vertex projection: The triangle in whose vertices , whose projection points are: ； ； ； The Triangle in B , whose vertex , , whose projection point is: ； ； ； point inclusion detection and depth comparison: Using the barycentric coordinate method to check whether or not a point is inside a triangle ； calculating the intersection position and depth in the original space: ； wherein represents a depth value, used to compare the before and after relationship; If then determine occlusion ; to repeat this detection; if none of the vertices is inside the opposite triangle, edge-edge intersection is detected, and the front and back relationship is compared according to the intersection depth.

8. The method of claim 5, wherein: the step 3.3 is a loop constraint processing: detecting loops in all constraint relationships; by identifying all nodes in the loop, some constraints are manually or automatically deleted according to preset rules to break the loop.

9. The method of claim 1, wherein: the step S4 calculates the level of the parts in each of the front, rear, left, right and bottom partitions and performs level allocation; integrating the level relationships of all partitions, a graph structure is constructed to describe the overall constraint relationship of the body parts, and accurate assembly sequence input is provided for the assembly process planning.

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