A hull curved surface fairing inspection system and method based on a ship CAD system

Abstract

This invention relates to a system and method for inspecting the smoothness of ship hull surfaces based on a ship CAD system. The system includes a data interface module, a judgment module, a general smoothness inspection module, a ship-specific smoothness inspection module, and an output module. The system opens or imports the ship hull surface model to be inspected. If it is a hull outer shell surface, it is inspected using the ship-specific smoothness inspection module; otherwise, it is inspected using the general smoothness inspection module. Finally, the output module outputs the inspection results. This invention improves the accuracy of surface smoothness inspection by distinguishing hull surfaces according to whether they are hull outer shell surfaces and by inspecting single surfaces and multiple adjacent surfaces separately. It meets the needs of inspecting various types of surfaces and can efficiently achieve smoothness quality inspection of hull surface models, reducing rework for designers and improving work efficiency.

Description

Technical Field

[0001] This invention relates to the field of digital ship design, and specifically to a system and method for inspecting the smoothness of hull surfaces based on a ship CAD system. Background Technology

[0002] The Ship CAD System is a 3D CAD graphics platform developed based on OpenGL. It features functions such as hull surface design, structural design, piping system design, duct design, electrical design, iron outfitting design, and painting production design. The Ship CAD System was developed to meet the requirements of complex surface representation, calculation, and accuracy in ship product and process design, significantly enhancing hull surface modeling capabilities. It also provides hull surface modeling and calculation technology for overall design and structural design.

[0003] In the preliminary design phase of a ship, designers obtain the hull surface by lofting the ship's design lines to meet smoothness quality standards. Since the hull surface plays a crucial role in ship performance calculations and manufacturing, its smoothness quality is closely related to the digital design of the ship. Ensuring the rational and efficient design of a hull surface that meets the requirements of the hull itself is a common challenge for designers. Therefore, developing a smoothness check method for hull surfaces to help designers quickly and accurately identify surfaces that do not meet design requirements is of great significance. This can reduce the workload of designers in designing and checking surfaces in different software, thereby improving their work efficiency.

[0004] Existing CAD software such as AM, FORAN, CATIA, and TRIBON all have their own methods for checking surface smoothness. However, some software such as AM, FORAN, and TRIBON have relatively simple inspection methods and are less efficient when faced with complex situations. CATIA has relatively comprehensive general surface inspection methods, but it lacks professional inspection methods related to marine-related disciplines. Summary of the Invention

[0005] To address the issues existing in CAD software regarding surface smoothness inspection, this invention provides a system and method for inspecting hull surface smoothness based on a ship CAD system, enabling the smoothness inspection of hull surfaces and identifying surfaces and areas that do not meet smoothness quality requirements.

[0006] The technical objective of this invention is achieved through the following technical solution: A method for inspecting the smoothness of hull surfaces based on a ship CAD system, the method comprising: S1. Open or import the hull surface model to be inspected in the ship CAD system, and then proceed to step S2. S2. Determine whether the surface in the hull surface model is the hull shell surface. If it is the hull shell surface, proceed to step S3; otherwise, proceed to step S4. S3. If the surface in the hull surface model is the hull shell surface, check the consistency of the smoothness quality between the hull shell surface and the corresponding hull shell surface design line, and identify the surfaces and areas where the smoothness quality of the hull shell surface and the design line does not match. S4. Visually inspect the hull surface model using the zebra stripe inspection method. Determine the smoothness quality of individual surfaces and multiple surfaces of the hull surface model by the shape of the zebra stripe lines projected onto the surface. Identify surfaces that do not meet the smoothness requirements and proceed to step S5. S5. If the surface that does not meet the smoothness requirement is a single surface, then perform a cross-sectional curvature comb analysis on the surface to determine the local areas on the surface that do not meet the smoothness requirement. If the surfaces that do not meet the smoothness requirements are multiple adjacent surfaces, and the multiple surfaces include at least two adjacent surfaces, then a smoothness quality analysis is performed between the multiple adjacent surfaces to determine the local boundaries of the multiple surfaces that do not meet the smoothness requirements.

[0007] Furthermore, the method also includes checking for areas of abnormal curvature direction and curvature data, based on the zebra stripe inspection method.

[0008] Furthermore, in step S4, if the edge of the zebra stripe on a single surface has a gap, a bend, or a serration, then the smoothness quality of the surface does not meet the smoothness requirements.

[0009] Furthermore, in step S4, when checking the smoothness quality between multiple surfaces: If the zebra stripes of multiple adjacent surfaces are broken or not connected at the surface junction, then the positional continuity standard is not met between the multiple adjacent surfaces. If the zebra stripes at the junction of multiple adjacent surfaces are not broken but misaligned, then the tangential continuity standard is not met between the multiple adjacent surfaces. If the zebra stripes at the junction of multiple adjacent surfaces do not have breaks or misalignments but have sharp corners or deformations, then the curvature continuity standard is not met between the multiple adjacent surfaces.

[0010] Furthermore, when examining the curvature data area, calculate the Gaussian curvature, minimum curvature, maximum curvature, or average curvature values ​​at different points on the surface, set numerical steps, and render different colors for values ​​located on different numerical steps.

[0011] Furthermore, in step S5, when performing cross-sectional curvature comb analysis on the surface, different cross-sectional lines are selected in the U and V directions of the surface, and the curvature combs and envelopes on the cross-sectional lines are analyzed. The locations of smoothness quality defects on the surface are determined by the differences on the curvature combs or the cusps and non-characteristic undulations on the envelopes.

[0012] Furthermore, in step S5, when performing the smoothness quality analysis between surfaces, the analysis includes checking for non-intersection between surfaces, continuity of position between surfaces, continuity of tangency between surfaces, and continuity of curvature between surfaces. Based on the continuity of surface position, the analysis further checks for continuity of tangency between surfaces and continuity of curvature between surfaces, and returns the maximum value of the checks for non-intersection between surfaces, continuity of position between surfaces, continuity of tangency between surfaces, and continuity of curvature between surfaces.

[0013] Furthermore, when performing positional continuity checks between surfaces, adjacent surfaces are topologically stitched according to the set continuity conditions. If the stitching is successful, the smoothness quality between adjacent surfaces meets the requirements; if the stitching is unsuccessful, the smoothness quality between surfaces does not meet the requirements. When performing a tangent continuity check between surfaces, several sampling points are selected on the common boundary of adjacent surfaces, and the angle between the tangent vectors of the sampling points on the boundary of adjacent surfaces is calculated. If the angle between the tangent vectors of all sampling points is less than the set angle, then the adjacent surfaces are tangent continuity under the set angle; otherwise, the adjacent surfaces are not tangent continuity under the set angle. When performing curvature continuity checks between surfaces, several sampling points are selected on the common boundary of adjacent surfaces. The Gaussian curvature of the sampling points on the adjacent surfaces is calculated, and the difference ratio of the Gaussian curvature of each sampling point on the adjacent surfaces is calculated. If the difference ratio of all sampling points is less than the set difference ratio threshold, then the curvature of the adjacent surfaces is continuous under the set difference ratio threshold condition; otherwise, the curvature of the adjacent surfaces is discontinuous under the set difference ratio threshold condition.

[0014] Furthermore, in step S3, the hull shell surface and the design line are both expressed using the same type of NURBS. Several sampling points are selected on the hull shell surface, and the minimum distance between the sampling points on the hull shell surface and the design line is calculated. The minimum distance is represented by pixels of different colors. By checking the minimum distance between the sampling points and the design line, surfaces and areas where the smoothness of the hull shell surface does not match that of the design line are identified.

[0015] This invention also provides a hull surface smoothness inspection system based on a ship CAD system, comprising: The data interface module is used to connect to the ship CAD system to open or import hull surface models; The judgment module is used to determine whether the opened or imported hull surface model is a hull shell surface; The general smoothness check module performs a surface smoothness check on the hull surface model when the judgment result of the judgment module is not the hull outer shell surface. The ship-specific smoothness inspection module performs surface smoothness inspection on the hull surface model when the judgment structure of the judgment module is the hull outer shell curved surface. The output module is used to output the inspection results of the general smoothness inspection module and / or the ship-specific smoothness inspection module.

[0016] Compared with the prior art, the beneficial effect of the present invention is that, compared with using the same detection method for all, the hull surface smoothness inspection method of the present invention improves the accuracy of hull surface smoothness inspection by distinguishing whether the hull surface is a hull shell surface; and by detecting the smoothness of a single surface and multiple adjacent surfaces separately, and by combining zebra stripe detection and curvature detection, the accuracy of surface smoothness detection is further improved.

[0017] The method of this invention enables smoothness inspection of hull outer shell surfaces, non-hull outer shell surfaces, single surfaces, and multiple adjacent surfaces, meeting the needs of various types of surface inspection. It can efficiently achieve smoothness quality inspection of hull surface models, which helps reduce rework by designers and improve work efficiency. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process of the hull surface smoothness inspection method based on the ship CAD system of the present invention.

[0019] Figure 2 This is a schematic diagram of the hull surface smoothness inspection system based on the ship CAD system of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to specific embodiments: A method for inspecting the smoothness of hull surfaces based on a ship CAD system, such as Figure 1 As shown, the method includes: S1. Open the hull surface model to be inspected in the ship CAD system, or open a blank file and import the hull surface model to be inspected into the ship CAD system through a neutral format file (IGES / STEP), and then proceed to step S2. S2. Determine whether the surface in the hull surface model is a hull shell surface. The hull shell surface is a complex surface constructed using the ship's design lines as modeling parameters. The degree of fit between the surface and the original lines is an important indicator for the smoothness quality inspection of the hull shell surface. A higher degree of fit means that the hull shell surface meets the design requirements for smoothness quality. This includes determining whether the imported or opened hull surface model is a hull shell surface and whether it contains hull shell surfaces. If it is a hull shell surface, proceed to step S3. If it contains hull shell surfaces, proceed to step S3 for the portion of the hull shell surface. If it is not a hull shell surface, proceed to step S4. If it contains both hull shell surfaces and non-hull shell surfaces, proceed to step S4 for the portion of the non-hull shell surface.

[0021] S3. If the surface in the hull surface model is the hull shell surface, check the consistency of the smoothness quality between the hull shell surface and the corresponding hull shell surface design line, and identify the surfaces and areas where the smoothness quality of the hull shell surface and the design line does not match. Both the hull outer shell surface and the design line are represented using the same type of NURBS. Several sampling points are selected on the hull outer shell surface, and the minimum distance between the sampling points on the hull outer shell surface and the design line is calculated. The minimum distance is represented by pixels of different colors. By checking the minimum distance between the sampling points and the design line, surfaces and areas where the smoothness of the hull outer shell surface does not match that of the design line are identified.

[0022] For example, sampling points are set every 500 mm on the curved surface of the hull, with a sampling step size of 500 mm. The sampling point density can be selected as needed. The minimum distance between each sampling point and the design profile at the same location is denoted as . , where i is the number of sampling points on the curved surface of the ship's hull, and several color gradients are defined. Display the corresponding color within the corresponding color gradient. The number exceeds the set threshold range (generally, the absolute value of the minimum distance between any sampling point on the curved surface of the hull and the design line should not exceed 5mm, that is, the prefabrication range specified in the design code is...). If the color exceeds the threshold range and is red / yellow (positive value) or blue / purple (negative value), it indicates that the smoothness of the hull surface at the sampling point does not match the design profile.

[0023] S4. Visually inspect the hull surface model using the zebra stripe inspection method. Judge the smoothness quality of individual surfaces and multiple surfaces of the hull surface model by the shape of the zebra stripe lines projected on the surface, and identify surfaces that do not meet the smoothness requirements. The zebra stripe inspection method is a technique widely used in surface design and quality inspection. It utilizes alternating light and dark light to illuminate the surface of an object, and the light is reflected to produce different texture changes. The zebra stripe inspection method can provide a relatively intuitive observation of the geometric characteristics and continuity of the surface, but it has a certain degree of subjectivity.

[0024] As a preferred option, to avoid omissions or deviations during the zebra stripe inspection process, based on the zebra stripe inspection method, check for areas with abnormal curvature direction and curvature data; proceed to step S5; More specifically, when performing step S4, for a single surface, if the zebra stripe edge of the single surface has gaps, bends, or jagged edges, then the smoothness quality of the surface does not meet the smoothness requirements.

[0025] For multiple adjacent surfaces, it should be noted that multiple adjacent surfaces must include at least two adjacent surfaces. When checking the smoothness quality between multiple surfaces: If the zebra stripes of multiple adjacent surfaces are broken or not connected at the surface junction, then the positional continuity standard is not met between the multiple adjacent surfaces. If the zebra stripes at the junction of multiple adjacent surfaces are not broken but misaligned, then the tangential continuity standard is not met between the multiple adjacent surfaces. If multiple adjacent surfaces have zebra stripes at their junctions that are not broken or misaligned but have sharp corners or deformations, then the curvature continuity standard is not met between the adjacent surfaces. When determining the presence of sharp corners, a corner angle less than 90° can be considered a sharp corner. When inspecting curvature data, the Gaussian curvature, minimum curvature, maximum curvature, or average curvature values ​​at different points on the surface are calculated. A numerical step is set, and values ​​at different numerical steps are rendered with different colors. The calculation can be performed by sampling according to the surface's UV parameter threshold of 1000*1000. This process can be achieved using curvature contour mapping, a visualization analysis tool based on the curvature values ​​or radii of curvature at points on the surface. By calculating the Gaussian curvature, minimum curvature, maximum curvature, or average curvature at different points on the surface and rendering them with different colors according to their magnitude, the curvature contour map allows for a direct observation of the locations of abnormal curvature changes. It should be noted that one or more of these parameters can be selected when calculating Gaussian curvature, minimum curvature, maximum curvature, or average curvature, depending on the needs.

[0026] S5. If the surface that does not meet the smoothness requirement is a single surface, then perform a cross-sectional curvature comb analysis on the surface to further narrow down the scope and determine the local area on the surface that does not meet the smoothness requirement. Specifically, when performing cross-sectional curvature comb analysis on a curved surface, different cross-sectional lines are selected in the U and V directions of the surface, and curvature combs and envelopes are analyzed on the cross-sectional lines. The U and V directions are two mutually perpendicular directions on the projection plane of the surface. The surface with the smallest angle to the orthogonal base plane is selected as the projection plane, and the projected area of ​​the surface on this projection plane should be the largest. The location of smoothness quality defects on the curved surface is determined by the differences on the curvature comb or the cusps and non-characteristic undulations on the envelope.

[0027] If the surfaces that do not meet the smoothness requirements are multiple adjacent surfaces, and the multiple surfaces include at least two adjacent surfaces, then perform a smoothness quality analysis between the multiple adjacent surfaces to narrow down the scope and determine the local boundaries of the multiple surfaces that do not meet the smoothness requirements. Specifically, the smoothness quality analysis between surfaces includes checking for non-intersection, positional continuity, tangential continuity, and curvature continuity between surfaces. Based on the positional continuity, further checks for tangential and curvature continuity are performed. The smoothness check system returns the continuity check results, including the non-intersection judgment result, the maximum values ​​of the positional continuity, tangential continuity, and curvature continuity checks. The maximum value of the positional continuity check result refers to the maximum distance between two adjacent surfaces. The maximum value of the tangential continuity check result refers to the maximum angle between the tangents at any point on the common boundary of two adjacent surfaces. The maximum value of the curvature continuity check result refers to the maximum curvature difference at any point on the common boundary of two adjacent surfaces.

[0028] More specifically, when performing a positional continuity check between surfaces, adjacent surfaces are topologically stitched according to the set continuity conditions. If the stitching is successful, the smoothness quality between adjacent surfaces meets the requirements; if the stitching is unsuccessful, the smoothness quality between surfaces does not meet the requirements. When performing a tangent continuity check between surfaces, several sampling points are selected on the common boundary of adjacent surfaces, with a step size of about 200mm between the sampling points. The tangent vectors of the sampling points on the common boundary of adjacent surfaces are calculated, and then the angle between the two tangent vectors is calculated. If the angle between the tangent vectors of all sampling points is less than the set angle (usually set to 1°), then the adjacent surfaces are tangent continuity under the set angle; otherwise, the adjacent surfaces are not tangent continuity under the set angle. When performing continuous curvature checks between surfaces, several sampling points are selected on the common boundary of adjacent surfaces, with a sampling point step size of approximately 200 mm. The Gaussian curvature values ​​a and b of the sampling points on the adjacent surfaces are calculated. The difference ratio of the Gaussian curvature of each sampling point on the adjacent surfaces is calculated. If the difference ratio of all sampling points is less than the set difference ratio threshold ( If the curvature of adjacent surfaces is continuous under the set difference ratio threshold, then the curvature of adjacent surfaces is continuous under the set difference ratio threshold; otherwise, the curvature of adjacent surfaces is discontinuous under the set difference ratio threshold.

[0029] This embodiment also provides a hull surface smoothness inspection system based on a ship CAD system, such as... Figure 2 As shown, it includes: The data interface module is used to connect to the ship CAD system to open or import the hull surface model and execute step S1; The judgment module determines whether the opened or imported hull surface model is a hull shell surface through user identification, and then executes step S2; The general smoothness check module performs a surface smoothness check on the hull surface model when the judgment result of the judgment module is not the hull shell surface, and executes steps S4 and S5. The ship-specific smoothness inspection module performs a surface smoothness inspection on the hull surface model when the judgment structure of the judgment module is the hull outer shell curved surface, and executes step S3. The output module is used to output the inspection results of the general smoothness inspection module and / or the ship-specific smoothness inspection module.

[0030] This embodiment is merely a further explanation of the present invention and is not intended to limit the present invention. Those skilled in the art can make non-inventive modifications to this embodiment as needed after reading this specification, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for inspecting the smoothness of hull surfaces based on a ship CAD system, characterized in that, The method includes: S1. Open or import the hull surface model to be inspected in the ship CAD system, and then proceed to step S2. S2. Determine whether the surface in the hull surface model is the hull shell surface. If it is the hull shell surface, proceed to step S3; otherwise, proceed to step S4. S3. If the surface in the hull surface model is the hull shell surface, check the consistency of the smoothness quality between the hull shell surface and the corresponding hull shell surface design line, and identify the surfaces and areas where the smoothness quality of the hull shell surface and the design line does not match. S4. Visually inspect the hull surface model using the zebra stripe inspection method. Determine the smoothness quality of individual surfaces and multiple surfaces of the hull surface model by the shape of the zebra stripe lines projected onto the surface. Identify surfaces that do not meet the smoothness requirements and proceed to step S5. S5. If the surface that does not meet the smoothness requirement is a single surface, then perform a cross-sectional curvature comb analysis on the surface to determine the local areas on the surface that do not meet the smoothness requirement. If the surfaces that do not meet the smoothness requirements are multiple adjacent surfaces, and the multiple surfaces include at least two adjacent surfaces, then a smoothness quality analysis is performed between the multiple adjacent surfaces to determine the local boundaries of the multiple surfaces that do not meet the smoothness requirements.

2. The method for inspecting the smoothness of hull surfaces based on a ship CAD system according to claim 1, characterized in that, This method also includes checking for areas with abnormal curvature direction and curvature data, based on the zebra stripe inspection method.

3. The method for inspecting the smoothness of hull surfaces based on a ship CAD system according to claim 2, characterized in that, In step S4, if the edge of the zebra stripe on a single curved surface has a gap, a bend, or a serration, then the smoothness of the curved surface does not meet the smoothness requirements.

4. The method for inspecting the smoothness of hull surfaces based on a ship CAD system according to claim 2, characterized in that, In step S4, when checking the smoothness quality between multiple curved surfaces: If the zebra stripes of multiple adjacent surfaces are broken or not connected at the surface junction, then the positional continuity standard is not met between the multiple adjacent surfaces. If the zebra stripes at the junction of multiple adjacent surfaces are not broken but misaligned, then the tangential continuity standard is not met between the multiple adjacent surfaces. If the zebra stripes at the junction of multiple adjacent surfaces do not have breaks or misalignments but have sharp corners or deformations, then the curvature continuity standard is not met between the multiple adjacent surfaces.

5. The method for inspecting the smoothness of hull surfaces based on a ship CAD system according to claim 2, characterized in that, When examining the curvature data area, calculate the Gaussian curvature, minimum curvature, maximum curvature, or average curvature values ​​at different points on the surface, set numerical steps, and render different colors for values ​​located on different numerical steps.

6. The method for inspecting the smoothness of hull surfaces based on a ship CAD system according to claim 1, characterized in that, In step S5, when performing cross-sectional curvature comb analysis on the surface, different cross-sectional lines are selected in the U and V directions of the surface, and the curvature combs and envelopes on the cross-sectional lines are analyzed. The locations of smoothness quality defects on the surface are determined by the differences on the curvature combs or the cusps and non-characteristic undulations on the envelopes.

7. The method for inspecting the smoothness of hull surfaces based on a ship CAD system according to claim 1, characterized in that, In step S5, when performing smoothness quality analysis between surfaces, the following steps are taken: checking for non-intersection between surfaces, continuity of position between surfaces, continuity of tangency between surfaces, and continuity of curvature between surfaces. Based on the continuity of surface position, the continuity of tangency between surfaces and continuity of curvature between surfaces are then checked, and the maximum values ​​of the checks for non-intersection between surfaces, continuity of position between surfaces, continuity of tangency between surfaces, and continuity of curvature between surfaces are returned.

8. The method for inspecting the smoothness of hull surfaces based on a ship CAD system according to claim 7, characterized in that, When performing positional continuity checks between surfaces, adjacent surfaces are topologically stitched according to the set continuity conditions. If the stitching is successful, the smoothness quality between adjacent surfaces meets the requirements; if the stitching is unsuccessful, the smoothness quality between surfaces does not meet the requirements. When performing a tangent continuity check between surfaces, several sampling points are selected on the common boundary of adjacent surfaces, and the angle between the tangent vectors of the sampling points on the boundary of adjacent surfaces is calculated. If the angle between the tangent vectors of all sampling points is less than the set angle, then the adjacent surfaces are tangent continuity under the set angle; otherwise, the adjacent surfaces are not tangent continuity under the set angle. When performing curvature continuity checks between surfaces, several sampling points are selected on the common boundary of adjacent surfaces. The Gaussian curvature of the sampling points on the adjacent surfaces is calculated, and the difference ratio of the Gaussian curvature of each sampling point on the adjacent surfaces is calculated. If the difference ratio of all sampling points is less than the set difference ratio threshold, then the curvature of the adjacent surfaces is continuous under the set difference ratio threshold condition; otherwise, the curvature of the adjacent surfaces is discontinuous under the set difference ratio threshold condition.

9. The method for inspecting the smoothness of hull surfaces based on a ship CAD system according to claim 1, characterized in that, In step S3, the hull shell surface and the design line are both expressed using the same type of NURBS. Several sampling points are selected on the hull shell surface, and the minimum distance between the sampling points on the hull shell surface and the design line is calculated. The minimum distance is represented by pixels of different colors. By checking the minimum distance between the sampling points and the design line, surfaces and areas where the smoothness of the hull shell surface does not match that of the design line are identified.

10. A hull surface smoothness inspection system based on a ship CAD system, characterized in that, include: The data interface module is used to connect to the ship CAD system to open or import hull surface models; The judgment module is used to determine whether the opened or imported hull surface model is a hull shell surface; The general smoothness check module performs a surface smoothness check on the hull surface model when the judgment result of the judgment module is not the hull outer shell surface. The ship-specific smoothness inspection module performs surface smoothness inspection on the hull surface model when the judgment structure of the judgment module is the hull outer shell curved surface. The output module is used to output the inspection results of the general smoothness inspection module and / or the ship-specific smoothness inspection module.

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