A method for three-dimensional design and curved surface forming of a shipbuilding constructional component

Abstract

A novel 3D design software and surface forming inspection interface method for shipbuilding components belongs to the technical field of 3D design of ship surfaces. This method generates NURBS curves based on the surface plate information extracted from the ship segment model data, including the boundary and internal points of the surface plate. It also generates NURBS curves based on the discrete points of the welding baselines of the surface profiles extracted from the ship segment model. The method then truncates the NURBS curves generated from the discrete points of the welding baselines based on the planar plate information extracted from the ship segment model. Finally, it refines the point set of the truncated welding baseline NURBS curves to generate intersecting NURBS curves, thus generating the NURBS mesh of the surface plate. Finally, it reconstructs the NURBS surface based on the truncated welding baseline NURBS curves. This invention, based on NURBS curve surface reconstruction, enables the reconstruction of ship segment surface plates, forming a 3D design software and surface forming inspection method for shipbuilding components, realizing the reconstruction of surface plates exported from ship production design software.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional design of ship surfaces, and in particular to a method for three-dimensional design and surface forming of ship construction components. Background Technology

[0002] In shipbuilding, the hull structure's formed components are typically modeled and designed using 3D design software. This design data needs to be transferred to subsequent forming and inspection stages to ensure that the fabrication and installation of components meet design requirements. However, existing data exchange between design software and forming and inspection systems presents several problems, primarily in the following aspects:

[0003] a. Incompatible data formats: Different software systems often use different data formats, which can lead to data loss or format errors during data transmission.

[0004] b. Inaccurate surface forming inspection: Existing inspection systems have difficulty accurately matching design data when detecting surface forming errors, affecting the accuracy of inspection results.

[0005] c. Lack of automated interface: In existing technologies, the interface between design data and test data is mostly manual, which is inefficient and prone to errors.

[0006] Therefore, there is an urgent need for a new method to enable data transmission and interface integration between 3D design software for shipbuilding components and surface forming inspection systems, thereby improving work efficiency and ensuring accurate matching between design and forming.

[0007] Based on the aforementioned technical issues, from the perspective of solving different technical problems, the following types of literature can also be detected, but each of them has various problems, as detailed below:

[0008] Patent CN116091734A discloses a geometric error characterization method based on NURBS surface reconstruction. The technical points of this patent are: determining the degree of the NURBS surface and the weight factors of each type value point; parameterizing the type value points in the row direction u and column direction v using the averaging technique AVG; performing NURBS curve interpolation to obtain the coordinates of all control vertices; establishing a mathematical model of the true geometric shape error of the surface of the part to be processed using NURBS surface interpolation reconstruction technology; and generating a geometric error surface model through forward calculation.

[0009] Patent CN110796735A, NURBS Surface Finite Element Plate and Shell Mesh Generation Method and Computer Implementation System; the technical point of this patent is to obtain the original NURBS surface, select multiple seed points on the boundary of the original NURBS surface, map the natural coordinates of the seed points in the surface to the plane, and perform triangular mesh generation on the plane based on the seed points.

[0010] [1] Li Chuanjun, Wang Liping. Research on B-spline curve fitting algorithm for airfoil blade-like curved surfaces. Computer Integrated Manufacturing Systems, 2024, 30(01): 144-157. The technical point of this paper is to reconstruct the discrete tool path based on the fluid dynamics characteristics using B-spline curves, and fit the equivalent lift tool path under the conditions of minimizing the curvature, endpoint interpolation, endpoint tangent continuity and maximum allowable error.

[0011] Paper [2] Liu Xinkai. Research on trajectory planning of large ship facade painting robot based on parametric surface reconstruction. Southeast University, 2022. The technical point of this paper is to pre-segment the ship facade according to the process requirements of ship segment painting and then reconstruct the ship facade after pre-segmentation using NURBS surface reconstruction.

[0012] Paper [3] Zhang Xu, Hou Maosheng, Liu Zhichao, et al. Algorithm for surface reconstruction of plate and shell structure based on fiber Bragg grating sensor. Progress in Laser & Optoelectronics, 2020, 57(09):74-81. The technical point of this paper is to study the surface reconstruction algorithm of plate and shell structure using fiber Bragg grating (FBG) sensor to address the assembly deformation problem caused by factors such as prestress and dimensional position deviation. The relationship between wavelength offset and curvature was established, the curvature data required for surface reconstruction algorithm was obtained, and the coordinate increment of all measuring points was calculated by applying piecewise fitting algorithm, thereby realizing curve reconstruction.

[0013] In summary, existing technologies typically focus on the generation of curved surfaces, with limited research on the reconstruction of curved surfaces derived from production design software for segmented hull plate structures. Summary of the Invention

[0014] To address the shortcomings of existing technologies, this invention proposes a novel 3D design software and surface forming inspection interface method for shipbuilding components. By analyzing boundary and internal point data of curved sheet metal, discrete point data of profile welding baselines on curved sheet metal, and discrete boundary point data of planar sheet metal in AM-XML files, a novel 3D design software and surface forming inspection interface method for shipbuilding components is proposed. This method innovatively proposes a NURBS curve reconstruction method based on discrete profile welding baseline data, performs bounding box design based on the discrete boundary data of curved sheet metal, and truncates the reconstructed NURBS curve from the discrete profile welding baseline data to generate a realistic NURBS curve of the profile welding baseline attached to the curved sheet metal.

[0015] The three-dimensional design software and surface forming detection interface method for shipbuilding and forming components of the present invention include the following steps:

[0016] Step 1: Methods for structured data parsing and database creation

[0017] Data is extracted from the AM-XML file and a database is created. A database is constructed with the segment name as the database name and the curved plate name as the sub-database name, realizing structured data parsing and database creation.

[0018] Step 2: Data Analysis and Topology Analysis Methods for Multi-Sub-Surface Plates

[0019] The data of the curved sheet material is analyzed to extract the boundary points and internal points of the curved sheet material. The bounding box of the curved sheet material is constructed, and the topological relationship between the boundary point data of the planar sheet material and the curved sheet material is analyzed using the bounding box.

[0020] Step 3: Profile Welding Baseline NURBS Curve Reconstruction Process

[0021] The NURBS curves of the discrete points of the profile welding baseline are reconstructed and saved to the database file.

[0022] Step 4: Optimize the NURBS curve of the profile welding baseline, refine the NURBS curve discrete point set, and generate curve family III.

[0023] The NURBS curve of the profile welding baseline is truncated using a bounding box and then densified to generate a set of densified points. Analysis of this set generates a new family of curves (III) perpendicular to the NURBS curve of the profile welding baseline. This results in a grid-like distribution of the curved sheet material.

[0024] Step 5: Generate NURBS surface from curved sheet material

[0025] The surface is reconstructed using the NURBS curve of the cut profile welding baseline.

[0026] Furthermore, step 2, which involves solving the data analysis and topology analysis method for multi-sub-surface plates, includes the following steps:

[0027] The boundary point information in the curved sheet material data is identified and judged to determine the boundary point information used for NURBS surface generation; and topological analysis is performed on the boundary point information in the planar sheet material data to determine the connected planar sheet materials.

[0028] Furthermore, step S2 specifically includes the following sub-steps:

[0029] S2.1 Data Extraction and Storage

[0030] For a certain curved plate corresponding to the profile welding baseline in step S1, further analyze multiple sub-curved plates; and extract the node data. Each sub-curved plate contains k curves, and each curve corresponds to g spatial points.

[0031] Save the point data for each sub-surface material; the coordinates of the points are represented as follows:

[0032] ;

[0033] S2.2 generates bounding boxes and parses relevant information for each point of the sub-surface material:

[0034]

[0035] Create a bounding box based on the area enclosed by the points mentioned above, and name it: ;

[0036] S2.3 Generate boundary lines: Generate the boundary lines of the curved surface material based on the point data. :

[0037]

[0038]

[0039]

[0040]

[0041] S2.4 Topology Analysis of Planar Panels

[0042] For nodes in the AM-XML file, extract the boundary points of the planar material; for a given boundary point (x, y, z) of the planar material, determine whether it is within the bounding box:

[0043]

[0044] If the conditions are met, it is determined that the planar plate and the sub-curved plate have a topological relationship.

[0045] S2.5 Planar Plate Base Plane Calculation

[0046] For the set of boundary points of a topologically related planar plate Calculate the following parameters:

[0047]

[0048] Determine the minimum value Determine the base plane of the flat panel:

[0049] like Minimum, with the base plane being YOZ;

[0050] like Minimum, with the base plane at XOZ;

[0051] like Minimum, with the base plane being XOY.

[0052] Furthermore, step S3 specifically includes the following sub-steps:

[0053] Based on profile welding baseline discrete point data The cumulative chord length method is used to calculate non-uniform node vectors.

[0054] S3.1 For a given set of points Calculate the Euclidean distance between each pair of adjacent points: ;

[0055] S3.2 Calculate the cumulative chord length. Defined as: ,final It is the total chord length;

[0056] S3.3 Normalize the parameter values, normalize the cumulative chord length, and map it to the interval [0, 1]:

[0057]

[0058] S3.4 Constructing node vectors: For NURBS curves of order p, the node vectors... Constructed as: First and last repeated Next, that is All intermediate node values ​​are parameter values. However, remove the beginning and end;

[0059] S3.5 is obtained from the cumulative chord length method. After constructing the parameter values, calculate the basis function matrix. Use recursion to calculate the B-spline basis functions. Constructing a matrix :

[0060]

[0061] S3.6 Solve the system of linear equations. Based on the interpolation conditions, solve the system of linear equations. ,in Let the column vector of control points be... For square array ;if It's not a square matrix; a least-squares solution is needed. ;

[0062] S3.7 Generate the profile welding baseline according to the NURBS curve formula:

[0063]

[0064] Based on the above definition and formula of NURBS curve, the NURBS curve formula for each profile welding baseline can be calculated.

[0065] Furthermore, using the enclosure box The multiple profile welding baselines in step S3 are cut off to obtain new multiple profile welding baselines;

[0066] The X, Y, and Z values ​​of discrete points on the profile welding baseline are determined, and the corresponding parameters are calculated. , The difference between the maximum and minimum values ​​of "X" The difference between the maximum and minimum values ​​of "Y". The difference between the maximum and minimum values ​​of the "Z" value; [This is the judgment / determination / restriction]. The minimum value in, assuming If the minimum value is reached, then the profile welding baseline is parallel to the YOZ plane, meaning the base plane of the profile welding baseline is the YOZ plane; assuming If the minimum value is reached, then the profile welding baseline is parallel to the XOZ plane, meaning the base plane of the profile welding baseline is the XOZ plane; assuming If the minimum value is reached, then the profile welding baseline is parallel to the XOY plane, meaning the base plane of the profile welding baseline is the XOY plane.

[0067] Based on the base plane of the profile welding baseline, fill in the NURBS curve corresponding to the boundary line; for the discrete point data of the profile welding baseline and the boundary line, arrange them in ascending order of Z value to generate the curve family I of the curved plate.

[0068] For multiple curves in curve family I, the points are refined. Assuming the step size is λ, the "X" value of the refined points in the longitudinal section is: X = Xmin + λs and Xmin ≤ X ≤ Xmax, s = 0, 1, ... Since the NURBS curves in curve family I are known, the points on each NURBS curve can be refined given the X value. That is, the problem is transformed into finding the coordinates of a point given the NURBS curve formula and the X value of that point.

[0069] Encryption points and bounding boxes If the encryption point is found to be within the bounding box, then the encryption point is preserved. Anything outside the boundary is deleted, and then the densification points of the profile that exceed the boundary of the curved plate are deleted; then the NURBS curve of the profile welding baseline is generated again; and merged with the NURBS curve corresponding to the boundary line to form curve family II;

[0070] By connecting corresponding points on multiple NURBS curves with the same X value, discrete points of the curves perpendicular to multiple curves on curve family II are regenerated, and multiple curves of curve family III are reconstructed using the method in step S3.

[0071] Furthermore, the sub-steps of step S5 are as follows:

[0072] S5.1 NURBS Curve Extraction and Information Acquisition: For each NURBS curve in curve family II, extract its control points, weights and node vector information in sequence to construct a complete NURBS parametric description;

[0073] S5.2 Multi-curve fitting based on B-spline: Construct a B-spline mesh composed of curves and map the curve data of curve family II to the surface fitting framework;

[0074] Using the weighted average of control points and geometric constraints between curves, a B-spline surface conforming to curve family II data is initially generated; the constraints include the continuity between curves and the smoothness of the spatial distribution of control points.

[0075] S5.3 Surface Fitting Optimization: The fitting algorithm is used to optimize the surface, reducing the error between the fitted surface and the original family of curves; the control point positions, weight distribution and node vector configuration are adjusted to optimize the surface shape so that it is closer to the geometric characteristics of the original data;

[0076] Recalculate the error index for each curve on the fitted surface to ensure that the deviations of all control points and specified sampling points are within the threshold range;

[0077] S5.4 Dynamic Adjustment and Error Assessment: After the surface is generated, the control points, weights, and node vector distribution are further adjusted through iterative optimization; combined with the error assessment method, the fitting process is dynamically optimized.

[0078] S5.5 Surface Data Storage and Model Reconstruction: The final optimized B-spline surface is parametrically described: control points, weights, node vectors, and surface equations are stored in the database to form standardized data records.

[0079] The beneficial effects of this invention are as follows:

[0080] This method generates NURBS curves based on the curved sheet material information extracted from the ship segment model data, using the boundary and internal points of the curved sheet material. It also generates NURBS curves based on the discrete points of the welding baseline of the curved profiles extracted from the ship segment model. The method then truncates the NURBS curves generated from the discrete points of the welding baseline based on the planar sheet material information extracted from the ship segment model. Finally, it refines the point set based on the truncated welding baseline NURBS curves to generate intersecting NURBS curves, thus creating a NURBS mesh for the curved sheet material. Finally, it reconstructs the NURBS surface based on the truncated welding baseline NURBS curves. This invention, based on NURBS curve surface reconstruction, enables the reconstruction of ship segment curved sheet materials, forming a 3D design software for shipbuilding components and a method for detecting curved surface forming structures. It realizes the reconstruction of curved sheet materials exported from ship production design software. This method effectively solves the problems of large fitting errors and low detection accuracy caused by insufficient discrete points of curved sheets obtained from profile diagrams and insufficient discrete data points of curved sheets extracted from AM models in current technologies.

[0081] This method innovatively proposes a NURBS curve reconstruction method based on discrete data of profile welding baselines. It designs bounding boxes based on discrete data of the curved sheet metal boundary and truncates the reconstructed NURBS curves from the discrete data of the profile welding baselines to generate realistic NURBS curves of the profile welding baselines attached to the curved sheet metal. It also innovatively proposes using the profile welding baseline NURBS curves to generate a dense point set. By processing the dense point set data on multiple NURBS curves, a secondary NURBS curve is generated, resulting in mesh information for the two sets of NURBS curves. Finally, it innovatively uses the profile welding baseline NURBS curves and the NURBS curves of the curved sheet metal boundary to reconstruct the curved surface. Attached Figure Description

[0082] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0083] Figure 1 This is a flowchart of the three-dimensional design software for shipbuilding and forming components and the method for detecting curved surface forming structures in an embodiment of the present invention.

[0084] Figure 2 The welding baseline for the profile in the AM-XML file.

[0085] Figure 3 The surface mesh is fitted to curve family II and curve family III.

[0086] Figure 4 The surface fitted to curve family II. Detailed Implementation

[0087] The technologies described below, with reference to the accompanying drawings of the embodiments of the present invention, will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0088] Figure 1 This is a flowchart of a novel three-dimensional design software for shipbuilding molding components and a method for detecting curved surface molding structures, as described in this invention. Figure 1 As shown, the method includes the following steps:

[0089] Step 1: Based on the XML file of the ship segment AM model, a method for structured data parsing and database creation is proposed for efficient management of information on the curved surface structure of ship segments. Specifically, this includes:

[0090] Based on the XML file of the ship section AM model (hereinafter referred to as AM-XML file), a method for structured data parsing and database creation is proposed for efficient management of ship section construction information. The specific steps are as follows:

[0091] Step 101. Determining Segment Names and Creating the Database

[0092] The "ObjId" attribute of the "Block" child node under the "Ship" node in the AM-XML file is used as the unique identifier of the segment to determine the segment name.

[0093] A corresponding database is created based on the segment name to store all relevant data for that segment.

[0094] Step 102. Determining the Name of the Curved Surface Material and Creating the Sub-database

[0095] The "GroupId" attribute of the "CurvedPanel-PlateGroup" sub-node under the "Block" sub-node is used as the unique identifier of the curved panel material to determine the name of the curved panel material.

[0096] Establish an independent sub-database for each curved surface material to facilitate the classification and management of data related to curved surface materials within each segment.

[0097] Step 103. Extraction of Profile Data

[0098] For the database created above, parse the profile information under each "Ship-Block-CurvedPanel" node.

[0099] Data was extracted from each of the multiple profile nodes in “Ship—Block—CurvedPanel—StiffenerGroup”, including key data of the profile welding baseline.

[0100] Step 104. Analysis of Profile Welding Baseline Data

[0101] The data in “Ship—Block—CurvedPanel—StiffenerGroup—Stiffener--Trace” is extracted as the core of the profile welding baseline data.

[0102] The key is to extract discrete point data from “StartPoint2d” and “Segment2d-Node2d” under the “Trace” sub-node to ensure the integrity of the geometric information of the welding baseline.

[0103] In a Ship-Block-Curved Panel, each profile welding baseline, through its discrete point data, forms a continuous curve in three-dimensional space. Assume that... The welding baseline of each profile is a curve in three-dimensional space, with the discrete points of each profile welding baseline arranged sequentially.

[0104] Step 2 proposes a data analysis and topology analysis method for multi-sub-surface plates. Specifically, it includes:

[0105] Step 201. Data Extraction and Storage

[0106] For a certain curved plate (“Ship—Block—CurvedPanel”) corresponding to the welding baseline of each profile in step 1, multiple sub-curved plates (“Ship—Block—CurvedPanel—PlateGroup”) are further analyzed.

[0107] Extract the data from the “Ship—Block—CurvedPanel—PlateGroup—Plate—FaceSurface” node. Each sub-surface plate contains 9 curves, and each curve corresponds to 9 spatial points.

[0108] Save the data of 81 points for each sub-surface material. The coordinates of the points are represented as follows:

[0109]

[0110] Step 202. Bounding box generation

[0111] For each sub-surface plate, analyze the relevant information for 81 points:

[0112]

[0113] Create a bounding box based on the area enclosed by the points mentioned above, and name it: .

[0114] Step 203. Boundary line generation: Generate the boundary line of the curved surface material based on 81 points. ):

[0115] ①

[0116] ②

[0117] ③

[0118] ④

[0119] Step 204. Planar Panel Topology Analysis

[0120] For the “Ship—Block—PlanePanel—Boundary” node in the AM-XML file, extract the boundary points of the planar board: extract the “StartPoint2d” and “Segment2d—Node2d” information from the “SimpleContour” child node.

[0121] For a given boundary point (x, y, z) of a planar material, determine whether it lies within the bounding box:

[0122]

[0123] If the conditions are met, it is determined that the planar plate and the sub-curved plate have a topological relationship.

[0124] Step 205. Calculation of the base plane of the flat board.

[0125] For the set of boundary points of a topologically related planar plate Calculate the following parameters:

[0126]

[0127] Determine the minimum value Determine the base plane of the flat panel:

[0128] like Minimum, with the base plane being YOZ;

[0129] like Minimum, with the base plane at XOZ;

[0130] like Minimum, with the base plane being XOY;

[0131] Step 3, Profile Welding Baseline NURBS Curve Reconstruction Process. Specifically includes:

[0132] Based on profile welding baseline discrete point data The cumulative chord length method is used to calculate non-uniform nodal vectors. The specific steps are as follows:

[0133] Step 301. For the given set of points Calculate the Euclidean distance between each pair of adjacent points: .

[0134] Step 302. Calculate the cumulative chord length. Defined as: ,final It is the total chord length.

[0135] Step 303. Normalize the parameter values, normalize the cumulative chord length, and map it to the interval [0, 1]:

[0136]

[0137] Step 304. Construct node vectors for curves of order . NURBS curves, node vectors Constructed as: First and last repeated Next, that is All intermediate node values ​​are parameter values. However, remove the beginning and end.

[0138] Step 305. Obtained from the cumulative chord length method After constructing the parameter values, calculate the basis function matrix. Calculate the B-spline basis functions using recursion. Constructing a matrix :

[0139]

[0140] Step 306. Solve the system of linear equations. Based on the interpolation conditions, solve the system of linear equations. ,in Let the column vector of control points be... For square array ;if It's not a square matrix; a least-squares solution is needed. .

[0141] Step 307. Set control point weights

[0142] Step 308. Generate the profile welding baseline according to the NURBS curve formula:

[0143]

[0144] Based on the above definition and formula of NURBS curves, the NURBS curve formula for each profile welding baseline can be calculated. For example... Figure 2 The image shows the profile welding baseline information. Save the NURBS curve information for each profile welding baseline on the curved surface, as well as the discrete point information of the profile welding baseline corresponding to the NURBS curve.

[0145] Step 4: Optimize the NURBS curve of the profile welding baseline, refine the NURBS curve discrete point set, and generate curve family III. Specifically, this includes:

[0146] use The multiple profile welding baselines in step 3 are cut off to obtain new multiple profile welding baselines.

[0147] The X, Y, and Z values ​​of discrete points on the profile welding baseline are determined, and the corresponding parameters are calculated. , The difference between the maximum and minimum values ​​of "X" The difference between the maximum and minimum values ​​of "Y". This is the difference between the maximum and minimum values ​​of "Z". (Judgment) The minimum value in, let If the minimum value is reached, then the profile welding baseline is parallel to the YOZ plane, meaning the base plane of the profile welding baseline is the YOZ plane; assuming If the minimum value is reached, then the profile welding baseline is parallel to the XOZ plane, meaning the base plane of the profile welding baseline is the XOZ plane; assuming If the minimum value is reached, then the profile welding baseline is parallel to the XOY plane, meaning the base plane of the profile welding baseline is the XOY plane.

[0148] When the base plane of the profile welding baseline is XOY (the method is the same for other directions), fill the boundary line. and The corresponding NURBS curves. Based on the discrete point data of the profile welding baseline and boundary line, the Z values ​​are arranged from smallest to largest to generate a family of curves I for the curved sheet material.

[0149] For multiple curves in curve family I, point refinement is performed. Assuming a step size of λ = 100 mm, the "X" value of the refined points in the longitudinal profile is: X = Xmin + λs, where Xmin ≤ X ≤ Xmax, and s = 0, 1, ... Since the NURBS curves in curve family I are known, and given the X value, the points on each NURBS curve can be refined. This transforms the problem into finding the coordinates of a point given its NURBS curve formula and the X value of that point.

[0150] These encryption points and the bounding box If the encryption point is found to be within the bounding box, then the encryption point is preserved. Anything outside the specified area is deleted, and then the denser points of the profile that extend beyond the curved plate boundary are also deleted. Next, the NURBS curve of the profile welding baseline is generated a second time and compared with the boundary line. and The corresponding NURBS curves are merged to form curve family II.

[0151] By connecting corresponding points on multiple NURBS curves with the same X value, discrete points of the curves perpendicular to multiple curves in curve family II are regenerated. Multiple curves in curve family III are then reconstructed using the method described in step 3. This yields curves in both the horizontal and vertical directions (curve family II and curve family III), generating a grid-like piecewise surface structure, such as... Figure 3 As shown.

[0152] Step 5: Generate a NURBS surface from the curved material; specifically including:

[0153] After obtaining data from curve family II and curve family III, curve family II retains the original data characteristics compared to curve family III, and there are no errors or deviations introduced by fitting. Therefore, surface fitting is performed based on curve family II to ensure the geometric accuracy and consistency of the generated surface. First, the control points, weights, and node vector information on each NURBS curve in curve family II are solved.

[0154] Step 501. NURBS Curve Extraction and Information Acquisition:

[0155] For each NURBS curve in curve family II, its control points, weights, and node vector information are extracted sequentially to construct a complete NURBS parametric description.

[0156] Check the continuity between curves and the distribution of nodes, and record the necessary parametric relationships for subsequent surface fitting optimization.

[0157] Step 502. Multi-curve fitting based on B-splines:

[0158] Construct a B-spline mesh composed of curves to map the curve data of curve family II into the surface fitting framework.

[0159] Using the weighted average of control points and geometric constraints between curves, a B-spline surface conforming to curve family II data is initially generated, such as... Figure 4 .

[0160] Constraints include the continuity between curves (such as G0, G1 continuity) and the smoothness of the spatial distribution of control points, ensuring the consistency of the surface in terms of geometry and smoothness.

[0161] Step 503. Surface Fitting Optimization:

[0162] Optimize the surface using the least squares method or other fitting algorithms to reduce the error between the fitted surface and the original family of curves.

[0163] Adjust the control point positions, weight distribution, and node vector configuration to optimize the surface shape and make it closer to the geometric characteristics of the original data.

[0164] The error index is recalculated for each curve on the fitted surface to ensure that the deviations of all control points and specified sampling points are within acceptable limits.

[0165] Step 504. Dynamic Adjustment and Error Assessment:

[0166] After the surface is generated, the control points, weights, and node vector distribution are further adjusted through iterative optimization.

[0167] By combining error assessment methods (such as mean square error and maximum error), the fitting process is dynamically optimized to ensure that the quality of the generated surface meets the design requirements.

[0168] Special attention is paid to the fitting accuracy of the boundary curves and the overall surface smoothness to avoid local distortions caused by boundary effects.

[0169] Step 505. Surface Data Storage and Model Reconstruction:

[0170] The final optimized B-spline surface parametric description (control points, weights, node vectors, surface equations) is stored in the database to form standardized data records.

[0171] In summary, the 3D design software and surface forming inspection interface method for shipbuilding components provided in this embodiment of the invention extracts surface plate data, planar plate data, and surface plate profile data from the AM-XML ship segment model. It then reconstructs NURBS curves using discrete points on the profile welding baseline on the surface plate, supplements two NURBS curves through the discrete boundaries of the surface plate, and truncates the profile welding baseline NURBS curves according to the bounding box. The points on the NURBS curves are then densified, and NURBS curves are generated a second time using multiple corresponding points, thereby generating the surface mesh of the surface plate. Finally, the surface plate is regenerated using multiple NURBS curves.

[0172] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for three-dimensional design and curved surface forming of shipbuilding components, characterized in that, The method includes the following steps: S1: Method for structured data parsing and database creation: Extract data from AM-XML files and create a database. Build the database and sub-databases, using the segment name as the database name and the curved sheet material name as the sub-database name, to achieve structured data parsing and database creation. S2: Data parsing and topology analysis method for multi-sub-curved sheet materials: Parse the data of the curved sheet materials, extract the boundary points and internal points of the curved sheet materials, construct the bounding box of the curved sheet materials, use the bounding box to judge the boundary point data of the planar sheet materials, and analyze the topological relationship between the planar sheet materials and the curved sheet materials accordingly. S3: Profile Welding Baseline NURBS Curve Reconstruction Process: Reconstruct the NURBS curve for the discrete point data of the profile welding baseline and save it to the database file; S4: Optimize the NURBS curve of the profile welding baseline, refine the NURBS curve discrete point set, and generate curve family III; The NURBS curve of the profile welding baseline is extracted using a bounding box and densified to generate a set of densified points. The analysis of the densified point set is then used to generate a new family of curves III that is perpendicular to the NURBS curve of the profile welding baseline, thus making the curved sheet material present a grid-like distribution. S5: NURBS surface generation for curved sheet metal: Reconstruct the surface using the NURBS curve of the cut profile welding baseline.

2. The method for three-dimensional design and curved surface forming of shipbuilding components according to claim 1, characterized in that, In step S2, the steps of the multi-sub-surface plate data parsing and topology analysis method include: The boundary point information in the curved sheet material data is identified and judged to determine the boundary point information used for NURBS surface generation; and topological analysis is performed on the boundary point information in the planar sheet material data to determine the connected planar sheet materials.

3. The method for three-dimensional design and curved surface forming of shipbuilding components according to claim 2, characterized in that: Step S2 specifically includes the following sub-steps: S2.1 Data Extraction and Storage: For a certain curved plate corresponding to the profile welding baseline in step S1, further analyze multiple sub-curved plates; and extract the node data. Each sub-curved plate contains k curves, and each curve corresponds to g spatial points. Save the point data for each sub-surface material; the coordinates of the points are represented as follows: ； S2.2 generates bounding boxes and parses relevant information for each point of the sub-surface material: ； Create a bounding box based on the area enclosed by the points of the parsed subsurface material, and name it: ; S2.3 Generate boundary lines: Generate the boundary lines of the curved surface material based on the point data. : ； ； ； ； S2.4 Planar Plate Topology Analysis: For nodes in the AM-XML file, extract the boundary points of the planar material; for a given boundary point (x, y, z) of the planar material, determine whether it is within the bounding box: ； If the conditions are met, it is determined that the planar plate and the sub-curved plate have a topological relationship; S2.5 flat plate base plane calculation: For the set of boundary points of a topologically related planar plate Calculate the following parameters: ； Determine the minimum value Determine the base plane of the flat panel: like Minimum, with the base plane being YOZ; like Minimum, with the base plane being XOZ; like Minimum, with the base plane being XOY.

4. The method for three-dimensional design and curved surface forming of shipbuilding components according to claim 1, characterized in that: Step S3 specifically includes the following sub-steps: Based on the discrete point dataset of profile welding baseline The cumulative chord length method is used to calculate non-uniform node vectors. S3.1 For a given dataset Calculate the Euclidean distance between each pair of adjacent points: ; S3.2 Calculate the cumulative chord length. Defined as: ,final It is the total chord length; S3.3 Normalize the parameter values, normalize the cumulative chord length, and map it to the interval [0, 1]: ； S3.4 Constructing node vectors: For NURBS curves of order p, the node vectors... Constructed as: First and last repeated Next, that is All intermediate node values ​​are parameter values. However, remove the beginning and end; S3.5 is obtained from the cumulative chord length method. After constructing the parameter values, calculate the basis function matrix. Use recursion to calculate the B-spline basis functions. Constructing a matrix : ； S3.6 Solve the system of linear equations. Based on the interpolation conditions, solve the system of linear equations. ,in Let the control point column vector be... For square array ;if It's not a square matrix; a least-squares solution is needed. ; S3.7 Generate the profile welding baseline according to the NURBS curve formula: ； Based on the definition and formula of NURBS curves, calculate the NURBS curve formula for each profile welding baseline.

5. The method for three-dimensional design and curved surface forming of shipbuilding components according to claim 4, characterized in that: The specific process of step S4 is as follows: Using a bounding box The profile welding baseline in step S3 is cut off to obtain multiple new profile welding baselines; The X, Y, and Z values ​​of discrete points on the profile welding baseline are determined, and the corresponding parameters are calculated. , The difference between the maximum and minimum values ​​of "X". The difference between the maximum and minimum values ​​of "Y". The difference between the maximum and minimum values ​​of "Z"; Determine The minimum value in, assuming If the minimum value is reached, then the profile welding baseline is parallel to the YOZ plane, meaning the base plane of the profile welding baseline is the YOZ plane; assuming If the minimum value is reached, then the profile welding baseline is parallel to the XOZ plane, meaning the base plane of the profile welding baseline is the XOZ plane; assuming If the minimum value is reached, then the profile welding baseline is parallel to the XOY plane, meaning the base plane of the profile welding baseline is the XOY plane. Based on the base plane of the profile welding baseline, fill in the NURBS curve corresponding to the boundary line; for the discrete point data of the profile welding baseline and the boundary line, arrange them in ascending order of Z value to generate the curve family I of the curved plate. For multiple curves in curve family I, point refinement is performed. Assuming the step size is λ, the "X" value of the refined points in the longitudinal profile is: X = X min +λs and X min ≤X≤X max s=0,1,…; Given the NURBS curves in curve family I, and with the X value obtained, refine the points on each NURBS curve; that is, transform it into a problem of finding the coordinates of a point on the curve with a known NURBS curve formula and a known X value. Encryption points and bounding boxes If the encryption point is found to be within the bounding box, then the encryption point is preserved. Delete anything outside the curve, then delete the densification points of the profile that exceed the boundary of the curved plate; then regenerate the NURBS curve of the profile welding baseline; and merge it with the NURBS curve corresponding to the boundary line to form curve family II; By connecting corresponding points on multiple NURBS curves with the same X value, discrete points of the curves perpendicular to multiple curves on curve family II are regenerated, and multiple curves of curve family III are reconstructed using the method in step S3.

6. The method for three-dimensional design and curved surface forming of shipbuilding components according to claim 1, characterized in that, The sub-steps of step S5 are as follows: S5.1 NURBS Curve Extraction and Information Acquisition: For each NURBS curve in curve family II, extract its control points, weights and node vector information in sequence to construct a complete NURBS parametric description; S5.2 Multi-curve fitting based on B-spline: Construct a B-spline mesh composed of curves and map the curve data of curve family II to the surface fitting framework; Using the weighted average of control points and geometric constraints between curves, a B-spline surface conforming to curve family II data is initially generated; the constraints include the continuity between curves and the smoothness of the spatial distribution of control points. S5.3 Surface Fitting Optimization: The fitting algorithm is used to optimize the surface, reducing the error between the fitted surface and the original family of curves; the control point positions, weight distribution and node vector configuration are adjusted to optimize the surface shape so that it is closer to the geometric characteristics of the original data; Recalculate the error index for each curve on the fitted surface to ensure that the deviations of all control points and specified sampling points are within the threshold range; S5.4 Dynamic Adjustment and Error Assessment: After the surface is generated, the control points, weights, and node vector distribution are further adjusted through iterative optimization; combined with the error assessment method, the fitting process is dynamically optimized. S5.5 Surface Data Storage and Model Reconstruction: The final optimized B-spline surface is parametrically described: control points, weights, node vectors, and surface equations are stored in the database to form standardized data records.

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