Free-form surface direct-ruling reconstruction method, device and product based on step-form surface
By using a STEP-based method for reconstructing ruled surfaces, the problems of long conversion time and insufficient accuracy in converting freeform surfaces into ruled surfaces are solved, achieving efficient and smooth ruled surface reconstruction, which is suitable for side milling.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEFEI UNIV OF TECH
- Filing Date
- 2026-03-13
- Publication Date
- 2026-06-09
Smart Images
Figure CN122174489A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of computer-aided manufacturing (CAM) processing technology, specifically to: 1. a method for reconstructing the ruled surface of a free-form surface based on STEP-form surfaces; 2. a device for reconstructing the ruled surface of a free-form surface based on STEP-form surfaces; and 3. a computer program product. Background Technology
[0002] Side milling is a line contact machining method with advantages such as short machining time, low cost, good cutting conditions, and the ability to form part surfaces in a single operation. It is an important method for machining the surfaces of narrow and elongated parts such as turbine blades, bulk impeller blades, and aerospace structural components. Due to its inherent characteristics, side milling is mostly used for machining developable ruled surfaces. However, for non-developable surfaces, side milling has unavoidable inherent errors. In other words, conventional freeform surfaces cannot be machined using the side milling process.
[0003] Therefore, research on converting freeform surfaces into ruled surfaces for side milling is of great importance. However, current methods for converting freeform surfaces into ruled surfaces have drawbacks such as long processing time and insufficient shape accuracy. Summary of the Invention
[0004] Therefore, it is necessary to address the problems of long time consumption and insufficient shape accuracy in existing methods for converting freeform surfaces into ruled surfaces, and to provide a method and apparatus for freeform surface ruled reconstruction based on STEP-form surfaces.
[0005] This invention is achieved using the following technical solution: In a first aspect, the present invention discloses a method for reconstructing ruled freeform surfaces based on STEP-form surfaces, comprising: Step 1: First, import the freeform surface in STEP format and use it as the original STEP surface. Then, discretize it into a point cloud and locate the centroid of the original STEP surface based on the point cloud. Finally, obtain the ruled line corresponding to the centroid as a reference direction. Step two: First, expand the UV parameter range of the original STEP surface to obtain the expanded STEP surface. Then, based on the centroid of the original STEP surface, select a search path in the expanded STEP surface according to the surface trend and assign parameters on the search path. X Each sampling point is used to obtain the ridge line corresponding to each sampling point; Step 3: Filter out those whose deviation angle from the reference direction is within a preset angle range. Y The straight lines corresponding to each sampling point; Y ≤ X ; Step four, based on retentionY The target ruled surface is constructed by fitting the endpoints of the ruled lines corresponding to each sampling point and combining them with the UV parameter range of the original STEP surface.
[0006] This freeform surface ruling reconstruction method based on STEP-form surfaces implements the method or process according to embodiments of this disclosure.
[0007] Secondly, the present invention discloses a free-form surface ruling reconstruction device based on STEP-form surfaces, which uses the free-form surface ruling reconstruction method based on STEP-form surfaces of the first aspect.
[0008] The freeform surface ruling reconstruction device based on STEP-form surfaces includes: original surface processing module, extended surface processing module, ruling line screening module, and ruling surface construction module.
[0009] The original surface processing module is used to: first import the freeform surface in STEP form and use it as the original STEP surface, then discretize it into a point cloud, locate the centroid of the original STEP surface based on the point cloud, and then obtain the ruled line corresponding to the centroid as a reference direction.
[0010] The extended surface processing module is used to: first, extend the UV parameter range of the original STEP surface to obtain an extended STEP surface; then, based on the centroid of the original STEP surface, select a search path in the extended STEP surface according to the surface trend, and allocate parameters on the search path. X Each sampling point is used to obtain the ridge line corresponding to each sampling point.
[0011] The straight-line filtering module is used to filter lines whose deviation angle from the reference direction is within a preset angle range. Y The straight lines corresponding to each sampling point.
[0012] The ruled surface construction module is used for: based on preservation Y The target ruled surface is constructed by fitting the endpoints of the ruled lines corresponding to each sampling point and combining them with the UV parameter range of the original STEP surface.
[0013] This STEP-based freeform surface ruling reconstruction apparatus implements the method or process according to embodiments of this disclosure.
[0014] Secondly, the present invention discloses a computer program product, including a computer program. When executed by a processor, the computer program implements the steps of the freeform surface ruling reconstruction method based on STEP formal surfaces disclosed in the first aspect.
[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention first imports the freeform surface in STEP form to obtain a digitized original STEP surface. Then, on the one hand, it obtains the ruled lines corresponding to the centroid of the original STEP surface as a reference direction. On the other hand, it expands the parameters of the original STEP surface, selects a search path, and assigns sampling points to obtain the ruled lines corresponding to each sampling point while ensuring the integrity of the information. Then, it selects the ruled lines corresponding to the sampling points that meet the deviation requirements according to the reference direction to achieve smooth optimization. Finally, based on the ruled lines corresponding to the retained sampling points and combined with the UV parameter range of the original STEP surface, it quickly constructs a target ruled surface with simple geometric expression, smooth result, and high accuracy through endpoint fitting. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.
[0017] Figure 1 A flowchart of the freeform surface ruling reconstruction method based on STEP-formed surfaces provided in Embodiment 1 of the present invention; Figure 2 for Figure 1 A flowchart of the method for finding the ruled lines corresponding to the centroid of the original STEP surface in step one; Figure 3 for Figure 1 A flowchart illustrating the method for obtaining the straight lines corresponding to each sampling point in step two; Figure 4 for Figure 1 Flowchart of the first operation in step four; Figure 5 for Figure 1 The flowchart for the second operation in step four. Detailed Implementation
[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0019] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.
[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.
[0021] Example 1 This embodiment 1 provides a freeform surface ruled surface reconstruction method based on STEP form surfaces, which aims to quickly reconstruct a smooth and highly accurate target ruled surface from a freeform surface with minimal computational efficiency while ensuring data integrity.
[0022] See Figure 1 It presents a flowchart of a freeform surface ruling reconstruction method based on STEP-form surfaces, which includes the following steps: Step 1: First, import the freeform surface in STEP format and use it as the original STEP surface. Then, discretize it into a point cloud and locate the centroid of the original STEP surface based on the point cloud. Finally, obtain the ruled line corresponding to the centroid as a reference direction.
[0023] Among them, freeform surfaces are digitized through STEP-form surfaces (which are standardized data structures used in industrial software such as CAD and CAE to describe three-dimensional geometric shapes), which supports the identification of key features such as UV parameter range and surface trend, facilitating a series of subsequent processing.
[0024] Any curved surface can be represented by the following general formula: S ( u , v )=[ x ( u , v ), y ( u , v ), z ( u , v )]; In the formula, S Represents a curved surface;x , y , z Representing the three-dimensional rectangular coordinate system respectively X Axis coordinates Y Axis coordinates Z Axis coordinates; u , v They represent U To parameters, V To parameters.
[0025] Therefore, for the original STEP surface, its UV range is: u ∈[ u min , u max ]; v ∈[ v min , v max ]; u min , u max These are the original STEP surfaces. U The upper and lower bounds of the parameter; v min , v max These are the original STEP surfaces. V The upper and lower bounds of the parameter.
[0026] Since the original STEP surface is a geometric surface, it is difficult to evaluate and has a large computational load. Therefore, it is chosen to discretize it into a point cloud to form a set of surface points. Then, the centroid of the original STEP surface is located by calculating the centroid of the set of surface points.
[0027] It should be noted that the density of the point cloud can be preset—the higher the value, the closer it fits the original STEP surface, but the greater the computational cost. Therefore, the density of the point cloud should be selected within an appropriate range to ensure a balance between computational accuracy and computation time.
[0028] Furthermore, since the ruled lines need to be smooth and directionally consistent, it is necessary to first obtain the ruled lines corresponding to the centroid of the original STEP surface as a reference direction—see [link to STEP surface]. Figure 2 The specific steps are as follows: S101, randomly construct an original reference vector that is not parallel to the average normal of the original STEP surface, and eliminate its normal component by vector projection to obtain its initial original direction vector in the tangent plane.
[0029] S102, based on Rodrigues rotation, rotates the initial original direction vector around the surface average normal of the original STEP surface to generate a circumferentially uniformly distributed vector. Z One original scan direction vector.
[0030] It is important to note that Z Each original scan direction vector should cover an angle range of 0 to 180° and avoid repetition.
[0031] for Z Generally speaking, the larger the value, the smaller the rotation step size, and the more accurate the result, but the computation time will increase significantly. Therefore, it is important to select a value within an appropriate range. Z The value of is chosen to ensure a balance between calculation accuracy and computation time. Generally, the recommended value is... Z Take 180 (that is, rotate once every 1°).
[0032] S103, construct the local normal vector at the centroid of the original STEP surface and connect it with the first... z The original scanning direction vectors are tensed by the first... z The first original plane, then the second z The intersection of the original plane and the original STEP surface is used to obtain the first... z The original intersection line; z ∈[1, Z ]; Traversal Z The original scan direction vectors are obtained accordingly. Z The original intersection line.
[0033] It should be noted that the original intersection line is a line segment limited by the UV parameter range of the original STEP surface.
[0034] S104, using PCA principal component analysis from Z Select the original intersection line that is closest to the target line from the original intersection lines, and fit it into a straight line form to serve as the ruled line corresponding to the centroid of the original STEP surface.
[0035] Since the original intersection lines, as geometric line segments, also suffer from difficulties in evaluation and high computational costs, a method similar to that used for the original STEP surface is employed: the original intersection lines are discretized into point clouds to form line-point clouds (similarly, the density of the line-point clouds must be selected within an appropriate range to ensure a balance between computational accuracy and computational time) to facilitate processing by the PCA principal component analysis method. First, the centroid of the line-point cloud corresponding to each original intersection line is calculated, and the line-point cloud is translated to the centroid coordinate system based on this centroid. Then, the principal component directions of the line-point cloud are obtained through eigenvalue decomposition to achieve straight line fitting, and the RMS root mean square error of the fitted line is calculated as the core error index for screening. If the RMS root mean square error of a fitted line is less than the error threshold (selected based on empirical values), it indicates that its linearity meets the standard and is retained; otherwise, it is discarded. Among the several fitted lines that meet the standard, the fitted line with the smallest RMS root mean square error is selected as the ruled line corresponding to the centroid of the original STEP surface.
[0036] Step two: First, expand the UV parameter range of the original STEP surface to obtain the expanded STEP surface. Then, based on the centroid of the original STEP surface, select a search path in the expanded STEP surface according to the surface trend and assign parameters on the search path. X Each sampling point is used to obtain the ridge line corresponding to each sampling point.
[0037] It should be noted that the ruled lines obtained by fitting only the intersection with the original STEP surface are obviously insufficient to cover all the complete information of the original plane. Therefore, more parameter information needs to be obtained in a larger spatial range to ensure that all the complete information of the original plane can be covered.
[0038] Therefore, step two requires expanding the UV parameter range of the original STEP surface to obtain the expanded STEP surface.
[0039] Therefore, for an extended STEP surface, its UV range is: u ∈[ k 1 u min , k 1 u max ]; v ∈[ k 2 v min , k 2 v max ]; u min , u max These are the original STEP surfaces. U The upper and lower bounds of the parameter;v min , v max These are the original STEP surfaces. V The upper and lower bounds of the parameter; k 1. k 2 are respectively U The scaling factor of the parameter, V The scaling factor of the parameter.
[0040] It is important to note that the multiplier for expanding the UV parameter range should be selected within an appropriate range to ensure a balance between calculation accuracy and computation time. Generally, k 1. k 2∈[1.2,1.5].
[0041] Since the extended STEP surface is based on the original STEP surface, the centroid of the original STEP surface can be found at a corresponding position on the extended STEP surface. Therefore, based on this position, a search path is selected within the extended STEP surface according to the surface's curvature, and allocation is performed along this search path. X One sampling point.
[0042] The search path can be either an iso-V parameter line or an iso-U parameter line. Generally, two rounds of processing are performed, one using iso-V parameter lines and the other using iso-U parameter lines, to retain the better results from the target ruled surface.
[0043] And for X Generally speaking, the larger the value, the smaller the search interval and the more accurate the results, but this will significantly increase the computation time. Therefore, it is important to select a value within an appropriate range. X The value of is chosen to ensure a balance between calculation accuracy and calculation time.
[0044] For each sampling point, the goal is to obtain its corresponding ridge line—see [link / reference] Figure 3 The specific steps are as follows: S201, randomly construct and extend the STEP surface with non-parallel surface average normals, and eliminate its normal components by vector projection to obtain its initial extension direction vector in the tangent plane. S202, based on Rodrigues rotation, rotates the original direction vector around the surface average normal of the extended STEP surface to generate a circumferentially uniformly distributed vector. Z One extended scan direction vector; S203, Constructing an extended STEP surface in the... x The local normal vector at the sampling point and its relation to the first sampling point z The extended scanning direction vector is tensed by the first... z The first extended plane, then the second zThe intersection of the extended plane and the extended STEP surface is used to obtain the first... z Extend the intersection line; x ∈[1, X ]; z ∈[1, Z ]; Traversal Z The extended scan direction vector is obtained to obtain the first... x Each sampling point corresponds to Z Extend the intersection line; S204, using PCA principal component analysis from the first... x sampling points Z Select the extended intersection line that is closest to the target line from the extended intersection lines, and fit it into a straight line form as the first extended intersection line. x The straight lines corresponding to each sampling point; Traversal X Each sampling point is used to obtain the ridge line corresponding to each sampling point.
[0045] Compared to the operation in step one of obtaining the ruling lines corresponding to the centroid of the original STEP surface, the only difference here is that the object being processed has been adjusted, but the operation is similar and will not be described again.
[0046] Step 3: Filter out those whose deviation angle from the reference direction is within a preset angle range. Y The straight lines corresponding to each sampling point; Y ≤ X .
[0047] As mentioned above, to ensure the overall smoothness and directional consistency of the ruled lines, the deviation angle between the ruled lines corresponding to each sampling point and the reference direction is compared to select the ruled lines that meet the error requirements. This provides a more reliable basis for the generation of ruled surfaces and can reduce the total number of ruled lines to a certain extent, thereby reducing the time required for subsequent reconstruction.
[0048] It should be noted that the preset angle range is inversely correlated with the accuracy requirements of the target ruled surface and can be adjusted according to the actual situation.
[0049] Step four, based on retention Y The target ruled surface is constructed by fitting the endpoints of the ruled lines corresponding to each sampling point and combining them with the UV parameter range of the original STEP surface.
[0050] The construction of ruled surfaces is based on their geometric definition, namely, satisfying: S' ( u , v )=(1- v )P( u )+ v Q(u ); In the formula, S' ( u , v ) represents ruled surface; P( u ), Q( u ) indicates a cross-section conductor.
[0051] The existing method directly uses the connection of discrete endpoints to form a polyline for construction, which has obvious drawbacks: the polyline, as a guide wire, generates a ruled surface, which will have bends at discrete points, failing to meet the smoothness requirements of high-precision parts; the polyline does not have parametric characteristics, making it difficult to perform subsequent geometric optimization (such as adjusting the surface shape and correcting errors).
[0052] Step four employs a combination of endpoint fitting and range clipping, which can be achieved using either of the following two operations: I. First, crop the range, then fit the endpoints – see Figure 4 Specifically, it includes the following steps: S401, based on reservation Y The straight lines corresponding to each sampling point are trimmed according to the UV parameter range of the original STEP surface to obtain... Y The corrected straight lines; S402, Y By fitting B-spline curves to the endpoints of the corrected ruled lines on the same side (least squares method is recommended), two instantaneous generatrices are obtained—that is, P(in the above formula). u ), Q( u ); S403 constructs the target ruled surface based on two instantaneous busbars using linear interpolation.
[0053] II. First, fit the endpoints, then crop the range – see [link / reference] Figure 5 Specifically, it includes the following steps: S401, will be retained Y B-spline curve fitting is performed on the endpoints of the ruled lines corresponding to the sampling points on the same side (least square method is recommended) to obtain two instantaneous generatrices—that is, P(in the above formula). u ), Q( u ); S402, an extended ruled surface is constructed based on two instantaneous busbars using linear interpolation; S403 cuts the extended ruled surface according to the UV parameter range of the original STEP surface to obtain the target ruled surface.
[0054] Regardless of whether it's the first or second operation: the selected endpoints on the same side are one-to-one corresponding, which ensures that the fitted instantaneous bus is within the parameters. uThe consistency of the surface is achieved by fitting the endpoints on the same side with B-spline curves, which precisely satisfies the requirement of continuity of the ruled surface with the conductor, avoiding the surface roughness caused by direct splicing of discrete busbars, and balancing accuracy and engineering practicality. In terms of accuracy: using B-spline to fit discrete endpoints can optimally approximate the distribution of all busbar endpoints through the least squares method; at the same time, the locality and smoothness of B-splines ensure the smoothness of the instantaneous busbars, thereby ensuring the shape accuracy of the final ruled surface. In terms of engineering practicality: it is tolerant to small deviations of the endpoints (because the fitting process smooths out local invalid noise), and the resulting target ruled surface is still a STEP-form surface, compatible with mainstream industrial software, and has practical application value.
[0055] Of course, after obtaining the target ruled surface, error analysis can be performed to verify the results: The target ruled surface is compared with the original STEP surface in terms of error. Generally, the Euclidean distance between a point on the target ruled surface and its nearest projection point on the original STEP surface is calculated as the error at that point. Then, the maximum point error, average point error, and RMS root mean square error can be calculated. Typically, the average point error or RMS root mean square error is used as the error index.
[0056] If the error index is less than the preset error threshold, the target ruled surface is retained; otherwise, a message indicating a large error is displayed, and you can return to step one to readjust the parameters and recalculate.
[0057] It should be noted that the free-form surface ruling reconstruction method based on STEP-form surfaces provided in this embodiment 1 can be implemented based on the Python + OpenCASCADE geometry engine. The specific operation is completed through the ReadSTEP custom parser and a series of geometry processing functions, resulting in a high-precision target ruled surface.
[0058] Example 2 This embodiment 2 provides a freeform surface ruling reconstruction device based on STEP-form surfaces, which uses the freeform surface ruling reconstruction method based on STEP-form surfaces in the first aspect.
[0059] The freeform surface ruling reconstruction device based on STEP-form surfaces includes: original surface processing module, extended surface processing module, ruling line screening module, and ruling surface construction module.
[0060] The original surface processing module is configured as follows: first, the freeform surface is imported in STEP form and used as the original STEP surface; then, it is discretized into a point cloud; and the centroid of the original STEP surface is located based on the point cloud; then, the ruled line corresponding to the centroid is obtained as a reference direction.
[0061] The extended surface processing module is configured as follows: first, the UV parameter range of the original STEP surface is extended to obtain an extended STEP surface; then, based on the centroid of the original STEP surface, a search path is selected in the extended STEP surface according to the surface trend, and allocation is performed on the search path. X Each sampling point is used to obtain the ridge line corresponding to each sampling point.
[0062] The straight-line filtering module is configured to filter lines whose deviation angle from the reference direction is within a preset angle range. Y The straight lines corresponding to each sampling point.
[0063] The ruled surface construction module is configured as follows: based on reserved Y The target ruled surface is constructed by fitting the endpoints of the ruled lines corresponding to each sampling point and combining them with the UV parameter range of the original STEP surface.
[0064] Since this device uses the free-form surface ruling reconstruction method based on STEP-form surfaces in Example 1, it also has the same effect, which will not be repeated here.
[0065] Example 3 This embodiment 3 discloses a computer device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the free-form surface ruling reconstruction method based on STEP formal surface disclosed in embodiment 1.
[0066] The computer equipment can be either a mobile terminal or a fixed terminal. Examples of the former include mobile phones, laptops, digital radio receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Description), PMPs (Portable Media Players), and in-vehicle terminals (such as in-vehicle navigation terminals); examples of the latter include digital TVs and desktop computers.
[0067] This embodiment 3 also discloses a readable storage medium that stores computer program instructions. When the computer program instructions are read and run by a processor, the steps of the free-form surface ruling reconstruction method based on STEP-form surfaces disclosed in embodiment 1 are executed.
[0068] The readable storage medium may include, but is not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination of the above.
[0069] This embodiment 3 also discloses a computer program product, including a computer program. When executed by a processor, the computer program implements the steps of the freeform surface ruling reconstruction method based on STEP-form surfaces disclosed in embodiment 1.
[0070] It should be noted that the computer program used to execute the above can be written in one or more programming languages or a combination thereof. These programming languages include object-oriented programming languages—such as Java, Smalltalk, and C++—as well as conventional procedural programming languages—such as C or similar languages. The computer program can be executed entirely on the user's computer, partially on the user's computer, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer through any type of network—including a Local Area Network (LAN) or a Wide Area Network (WAN).
[0071] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0072] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A method for reconstructing ruled freeform surfaces based on STEP-form surfaces, characterized in that, It includes: Step 1: First, import the freeform surface in STEP format and use it as the original STEP surface. Then, discretize it into a cloud of facets and locate the centroid of the original STEP surface based on the cloud of facets. Then, obtain the ruled line corresponding to the centroid as a reference direction. Step two: First, expand the UV parameter range of the original STEP surface to obtain the expanded STEP surface. Then, based on the centroid of the original STEP surface, select a search path in the expanded STEP surface according to the surface trend and assign parameters on the search path. X Each sampling point is used to obtain the ridge line corresponding to each sampling point; Step 3: Filter out those whose deviation angle from the reference direction is within a preset angle range. Y The straight lines corresponding to each sampling point; Y ≤ X ; Step four, based on retention Y The target ruled surface is constructed by fitting the endpoints of the ruled lines corresponding to each sampling point and combining them with the UV parameter range of the original STEP surface.
2. The method for reconstructing ruled freeform surfaces based on STEP-form surfaces according to claim 1, characterized in that, In step one, the method for obtaining the ruled lines corresponding to the centroid of the original STEP surface includes: S101, randomly construct an original reference vector that is not parallel to the average normal of the original STEP surface, and eliminate its normal component by vector projection to obtain its initial original direction vector in the tangent plane. S102, based on Rodrigues rotation, rotates the initial original direction vector around the surface average normal of the original STEP surface to generate a circumferentially uniformly distributed vector. Z One original scan direction vector; S103, construct the local normal vector at the centroid of the original STEP surface and connect it with the first... z The original scanning direction vectors are tensed by the first... z The first original plane, then the second z The intersection of the original plane and the original STEP surface is used to obtain the first... z The original intersection line; z ∈[1, Z ]; Traversal Z The original scan direction vectors are obtained accordingly. Z The original intersection line; S104, using PCA principal component analysis from Z Select the original intersection line that is closest to the target line from the original intersection lines, and fit it into a straight line form to serve as the ruled line corresponding to the centroid of the original STEP surface.
3. The method for reconstructing ruled freeform surfaces based on STEP-form surfaces according to claim 1, characterized in that, In step two, the search path includes: iso-V parameter lines and / or iso-U parameter lines.
4. The method for reconstructing ruled freeform surfaces based on STEP-form surfaces according to claim 3, characterized in that, In step two, the method for obtaining the straight lines corresponding to each sampling point includes: S201, randomly construct and extend the STEP surface with non-parallel surface average normals, and eliminate its normal components by vector projection to obtain its initial extension direction vector in the tangent plane. S202, based on Rodrigues rotation, rotates the original direction vector around the surface average normal of the extended STEP surface to generate a circumferentially uniformly distributed vector. Z One extended scan direction vector; S203, Constructing an extended STEP surface in the... x The local normal vector at the sampling point and its relation to the first sampling point z The extended scanning direction vector is tensed by the first... z The first extended plane, then the second z The intersection of the extended plane and the extended STEP surface is used to obtain the first... z Extend the intersection line; x ∈[1, X ]; z ∈[1, Z ]; Traversal Z The extended scan direction vector is obtained to obtain the first... x Each sampling point corresponds to Z Extend the intersection line; S204, using PCA principal component analysis from the first... x sampling points Z Select the extended intersection line that is closest to the target line from the extended intersection lines, and fit it into a straight line form as the first extended intersection line. x The straight lines corresponding to each sampling point; Traversal X Each sampling point is used to obtain the ridge line corresponding to each sampling point.
5. The method for reconstructing ruled freeform surfaces based on STEP-form surfaces according to any one of claims 2-4, characterized in that, Within a suitable range, select the density of the dot cloud and the multiplier for expanding the UV parameter range. X , Z The value of is chosen to ensure a balance between calculation accuracy and calculation time.
6. The method for reconstructing ruled freeform surfaces based on STEP-form surfaces according to claim 5, characterized in that, Step four includes: S401, based on reservation Y The straight lines corresponding to each sampling point are trimmed according to the UV parameter range of the original STEP surface to obtain... Y The corrected straight lines; S402, Y Two instantaneous generatrices are obtained by fitting B-spline curves to the endpoints of the corrected straight lines on the same side. S403 constructs the target ruled surface based on two instantaneous busbars using linear interpolation.
7. The method for reconstructing ruled freeform surfaces based on STEP-form surfaces according to claim 5, characterized in that, Step four includes: S401, will be retained Y B-spline curve fitting is performed on the endpoints of the straight lines corresponding to the sampling points that are on the same side to obtain two instantaneous generatrices; S402, an extended ruled surface is constructed based on two instantaneous busbars using linear interpolation; S403 cuts the extended ruled surface according to the UV parameter range of the original STEP surface to obtain the target ruled surface.
8. The method for reconstructing ruled freeform surfaces based on STEP-form surfaces according to claim 5, characterized in that, Step four also includes: Compare the error between the target ruled surface and the original STEP surface; If the error index is less than the preset error threshold, the target ruled surface is retained; otherwise, a large error is indicated.
9. A device for reconstructing ruled surfaces of freeform surfaces based on STEP-form surfaces, characterized in that, It uses the free-form surface ruling reconstruction method based on STEP-form surfaces as described in any one of claims 1-8; The free-form surface ruling reconstruction device based on STEP-form surfaces includes: The original surface processing module is used to: first import the freeform surface in STEP form and use it as the original STEP surface, then discretize it into a point cloud, locate the centroid of the original STEP surface based on the point cloud, and then obtain the ruled line corresponding to the centroid as a reference direction. The extended surface processing module is used to: first, extend the UV parameter range of the original STEP surface to obtain an extended STEP surface; then, based on the centroid of the original STEP surface, select a search path in the extended STEP surface according to the surface trend, and allocate parameters on the search path. X Each sampling point is used to obtain the ridge line corresponding to each sampling point; The straight-line filtering module is used to filter lines whose deviation angle from the reference direction is within a preset angle range. Y The straight lines corresponding to each sampling point; and The ruled surface construction module is used for: based on preservation Y The target ruled surface is constructed by fitting the endpoints of the ruled lines corresponding to each sampling point and combining them with the UV parameter range of the original STEP surface.
10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the freeform surface ruling reconstruction method based on STEP-form surfaces as described in any one of claims 1-9.