Error grid generation method, device and equipment

Abstract

The present application provides a method, apparatus, and device for generating an error grid. When generating an error grid, the method first obtains an ideal three-dimensional model for a specified assembly and meshes the ideal three-dimensional model. The method then extracts the node coordinate values ​​of the contact surface nodes from the meshed ideal three-dimensional model. Point cloud data measured for the contact surface of the specified assembly is obtained. Interpolation fitting is performed on the point cloud data to obtain node sag values ​​for the fitted point cloud data. Finally, the node coordinate values ​​are replaced with the node sag values, so that a meshed solid model with geometric errors is generated using the replaced nodes. This shows that the technical solution provided by this embodiment can avoid the loss of precision that occurs when a three-dimensional solid model with geometric errors is imported into finite element simulation software, thereby improving the accuracy of finite element calculation results.

Description

Technical Field

[0001] The present application relates to the field of aviation assembly technology, and in particular to an error grid generation method, device and equipment. Background Art

[0002] Aircraft are high-tech products that integrate modern manufacturing technologies and the latest achievements in multidisciplinary fields. They are characterized by complex structures, large assembly scales, high assembly precision requirements, long assembly cycles, and the involvement of vast resources. Therefore, to ensure the reliability of aircraft assembly and shorten assembly cycles, assembly simulation is essential. In the field of aircraft assembly, existing simulation methods often use ideal three-dimensional models to simulate assembly mechanics based on design tolerance theory. These simulation models do not consider the impact of geometric errors in the product during the manufacturing process on the assembly posture and contact surface stress distribution. This often results in significant discrepancies between the simulation results and the actual assembly results.

[0003] To address these technical issues, the following implementation method is currently used to establish a finite element simulation model with geometric errors. This method, which fully considers the actual physical information and assembly processes during the assembly process, allows for finite element simulation calculations that simulate actual part assembly. The specific implementation method is as follows: Because CAE focuses on numerical calculations, 3D modeling is often performed using CAD during finite element analysis, and the resulting 3D model is then imported into the CAE application. However, this implementation method often results in unavoidable loss of accuracy during data exchange, especially for 3D solid models with geometric errors. These geometric errors inevitably lead to loss of accuracy during data exchange, ultimately affecting the accuracy of the finite element calculation results. Summary of the Invention

[0004] The present application provides a method, apparatus and device for generating an error grid to improve the accuracy of finite element calculation results.

[0005] An embodiment of the present application provides a method for generating an error grid, the method comprising:

[0006] Obtaining an ideal three-dimensional model for a specified assembly and meshing the ideal three-dimensional model;

[0007] Extracting node coordinate values ​​of contact surface nodes from the meshed ideal three-dimensional model;

[0008] Obtaining point cloud data of the specified assembly measured on a contact surface;

[0009] Performing interpolation fitting on the point cloud data to obtain node sagittal values ​​of the fitted point cloud data;

[0010] The node coordinate values ​​are replaced with the node sag values, so as to generate a meshed solid model with geometric errors using the replaced nodes.

[0011] As an embodiment, performing interpolation fitting on the point cloud data to obtain node sag values ​​of the fitted point cloud data includes:

[0012] Fitting the point cloud data using a specified surface fitting algorithm to obtain an interpolated surface with geometric errors;

[0013] Performing Bezier clipping on the interpolation surface to obtain a Bezier surface;

[0014] Performing control polygon vertex detection on the Bezier surface to obtain a valid Bezier surface;

[0015] Determining a candidate Bezier surface for the point to be projected based on the coordinate value of the point to be projected and a valid Bezier surface; the point to be projected is a contact surface node extracted from the gridded ideal three-dimensional model;

[0016] Obtaining an approximate point of the point to be projected on the Bezier surface according to a correspondence between the point to be projected and the candidate Bezier surface, and determining the approximate point as an initial value for iteration;

[0017] The iterative initial value is used to iteratively solve the set iterative equation to obtain the node sag value of the fitted point cloud data.

[0018] As an embodiment, performing Bezier clipping on the interpolation surface to obtain a Bezier surface includes:

[0019] Acquiring endpoint parameters forming the interpolation surface from the interpolation surface, and calculating the repeatability of the endpoint parameters;

[0020] Perform node insertion and refinement processing on the nodes of the interpolation surface. If the repetition of the nodes in the interpolation surface after interpolation reaches a set threshold, the interpolation surface after interpolation is clipped into a Bezier surface; if the repetition of the nodes in the interpolation surface after interpolation does not reach the set threshold, return to the step of performing node insertion and refinement processing on the nodes of the interpolation surface.

[0021] As an embodiment, performing control polygon vertex detection on the Bezier surface to obtain a valid Bezier surface includes:

[0022] Acquire multiple control polygons from the Bezier surface, sort the multiple control polygon vertices, and determine the sorted control polygon vertices as initial control polygon vertices;

[0023] For each initial polygon vertex, the initial control polygon vertex is used as the current control polygon vertex, and a dot product calculation is performed on the current control polygon vertex to obtain a vector dot product result. If the vector dot product result is a negative number, the step of performing Bezier clipping on the interpolation surface is returned to execution; if the vector dot product result is a positive number, it is determined whether the current control polygon vertex is the last initial control polygon vertex in the sorting; if not, the next initial control polygon vertex is used as the new current control polygon vertex, and the step of performing dot product calculation on the current control polygon vertex is returned to execution; if so, each initial control polygon is determined as a valid control polygon, so as to form a valid Bezier surface using the valid control polygon.

[0024] As an embodiment, determining a candidate Bezier surface for the point to be projected based on the coordinate value of the point to be projected and a valid Bezier surface includes:

[0025] For each valid Bezier surface, determine whether the valid control polygon in the valid Bezier surface meets the set candidate surface condition of the feature polygon. If so, the valid Bezier surface is determined as a candidate Bezier surface; if not, the valid Bezier surface is eliminated; wherein, the candidate surface condition of the feature polygon is that the point to be projected falls within the range of the control polygon but does not include falling on the boundary of the control polygon.

[0026] As an embodiment, obtaining an approximate point of the point to be projected on the Bezier surface according to a correspondence between the point to be projected and the candidate Bezier surface includes:

[0027] The candidate Bezier surface corresponding to each point to be projected is subdivided recursively to obtain the control points of the candidate Bezier surface;

[0028] Determine whether the control grid composed of the control points reaches the recursive limit threshold. If so, determine the control points as approximate points of the points to be projected. If not, return to the step of performing node insertion and refinement on the nodes of the interpolation surface.

[0029] In a second aspect, an embodiment of the present application further provides an error grid generation device, the error grid generation device comprising:

[0030] A meshing processing unit, configured to obtain an ideal three-dimensional model for a specified assembly and mesh the ideal three-dimensional model;

[0031] A node coordinate extraction unit is used to extract node coordinate values ​​of contact surface nodes from the gridded ideal three-dimensional model;

[0032] A point cloud data obtaining unit, configured to obtain point cloud data of the specified assembly measured on the contact surface;

[0033] A node sag value obtaining unit is used to perform interpolation fitting on the point cloud data to obtain node sag values ​​of the fitted point cloud data;

[0034] The grid entity model generating unit is used to replace the node coordinate values ​​with the node sag values, so as to generate a grid entity model with geometric errors using the replaced nodes.

[0035] As an embodiment, the node sag value obtaining unit includes:

[0036] An interpolation surface obtaining subunit is used to fit the point cloud data using a specified surface fitting algorithm to obtain an interpolation surface with geometric errors;

[0037] A Bezier surface obtaining subunit is used to perform Bezier clipping on the interpolation surface to obtain a Bezier surface;

[0038] A valid Bezier surface obtaining subunit, configured to perform control polygon vertex detection on the Bezier surface to obtain a valid Bezier surface;

[0039] A candidate Bezier surface obtaining subunit is used to determine a candidate Bezier surface of the point to be projected based on the coordinate value of the point to be projected and the valid Bezier surface; the point to be projected is a contact surface node extracted from the gridded ideal three-dimensional model;

[0040] an iteration initial value determination subunit, configured to obtain an approximate point of the point to be projected on the Bezier surface according to a correspondence between the point to be projected and the candidate Bezier surface, and determine the approximate point as an iteration initial value;

[0041] The node sag value obtaining subunit is used to iteratively solve the set iterative equation using the iterative initial value to obtain the node sag value of the fitted point cloud data.

[0042] As an embodiment, the Bezier surface subunit is used to:

[0043] Acquiring endpoint parameters forming the interpolation surface from the interpolation surface, and calculating the repeatability of the endpoint parameters;

[0044] Perform node insertion and refinement processing on the nodes of the interpolation surface. If the repetition of the nodes in the interpolation surface after interpolation reaches a set threshold, the interpolation surface after interpolation is clipped into a Bezier surface; if the repetition of the nodes in the interpolation surface after interpolation does not reach the set threshold, return to the step of performing node insertion and refinement processing on the nodes of the interpolation surface.

[0045] As can be seen from the above technical solution, in this application, when generating an error grid, an ideal three-dimensional model for a specified assembly is first obtained, and the ideal three-dimensional model is meshed. Then, the node coordinate values ​​of the contact surface nodes are extracted from the meshed ideal three-dimensional model; the point cloud data measured for the contact surface of the specified assembly is obtained; the point cloud data is interpolated and fitted to obtain the node sag values ​​of the fitted point cloud data; finally, the node coordinate values ​​are replaced with the node sag values, so that a meshed solid model with geometric errors is generated using the replaced nodes. It can be seen that the technical solution provided by this embodiment is to directly map the measured data with geometric errors to the contact surface of the ideal three-dimensional mesh model, thereby realizing the automatic update of the finite element mesh model with geometric errors, and avoiding the loss of accuracy of the three-dimensional solid model with geometric errors due to importing it into the finite element simulation software. It can be seen that the application of the technical solution provided by this embodiment can improve the accuracy of the finite element calculation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0047] Figure 1 A flowchart of an error grid generation method provided in this application;

[0048] Figure 2 A schematic structural diagram of an error grid generation device provided in this application;

[0049] Figure 3 This is a schematic diagram of the structure of the electronic device provided in this application. DETAILED DESCRIPTION

[0050] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] See also Figure 1 , Figure 1 This is a flowchart of a method for generating an error grid provided in an embodiment of the present application. The method is applied to an electronic device and includes the following steps:

[0052] Step 101: obtain an ideal three-dimensional model of a specified assembly and mesh the ideal three-dimensional model.

[0053] In this embodiment, the ideal three-dimensional model may be a model drawn by three-dimensional software CAD, or a model drawn by simulation software CAE, and this embodiment does not limit this.

[0054] For example, if the CAD software uses PROE and the CAE software uses ABAQUS software, one implementation method is: first draw an ideal three-dimensional model of the specified assembly in PROE, save it in a file format that can be recognized by ABAUS software, and import it into ABAQUS software in this file format.

[0055] The ideal three-dimensional model can be considered as a three-dimensional model without geometric errors.

[0056] Step 102: extracting node coordinate values ​​of contact surface nodes from the gridded ideal three-dimensional model.

[0057] The meshed ideal 3D model can be considered to be composed of different nodes. In this embodiment, only the node coordinates of the contact surface nodes are obtained from the ideal 3D model. The contact surface nodes can be considered as the assembly surface nodes used for assembling various components in the ideal 3D model.

[0058] In some embodiments, step 102 is implemented as follows, specifically:

[0059] Select the mesh node to be edited, create a target set to store the mesh node, and number these mesh nodes; use the specified loop statement to traverse the node numbers in the target set and query the target node coordinate values ​​that only represent the contact surface nodes; store these target node coordinate values ​​in the specified array.

[0060] Step 103: Obtain point cloud data of the contact surface of the designated assembly.

[0061] The point metadata in this embodiment may be point cloud data input by a user, or may be point cloud data acquired from a local electronic device or other electronic devices, and this embodiment is not limited thereto.

[0062] The point cloud data of this embodiment is obtained by actually measuring each contact surface in a specified assembly, and is data with geometric errors.

[0063] Step 104 : performing interpolation fitting on the point cloud data to obtain node sag values ​​of the fitted point cloud data.

[0064] In this step, the minimum distance method can be used to determine the node height value of each fitted point cloud data.

[0065] Step 105: Replace the node coordinate value with the node sag value, so as to generate a meshed solid model with geometric errors using the replaced node.

[0066] In this embodiment, the node vector height value has geometric errors. By replacing the node coordinate value with the node vector height value, the obtained meshed solid model can be a meshed solid model with geometric errors, which is closer to the real solid three-dimensional model. When the meshed solid model with geometric errors is used for subsequent simulation, it is closer to the actual assembly and the simulation results are more accurate.

[0067] It should be noted that this embodiment only replaces the node sag values ​​for nodes on the contact surface. In other words, the nodes on the non-contact surface retain their node coordinates in the ideal 3D model. Nodes on these non-contact surfaces do not need to be processed because they do not participate in assembly. This means they have no effect on the assembly of parts within the specified assembly, and therefore do not affect the assembly accuracy of the parts within the assembly.

[0068] So far, completed Figure 1 Description shown.

[0069] It can be seen that the technical solution provided by this embodiment, in this application, when generating an error grid, first obtains an ideal three-dimensional model for a specified assembly, and meshes the ideal three-dimensional model, then extracts the node coordinate values ​​of the contact surface nodes from the meshed ideal three-dimensional model; obtains the point cloud data measured for the contact surface of the specified assembly; interpolates and fits the point cloud data to obtain the node sag values ​​of the fitted point cloud data; finally, replaces the node coordinate values ​​with the node sag values, and uses the replaced nodes to generate a meshed solid model with geometric errors. It can be seen that the technical solution provided by this embodiment is to directly map the measured data with geometric errors to the contact surface of the ideal three-dimensional mesh model, thereby realizing the automatic update of the finite element mesh model with geometric errors, avoiding the loss of accuracy of the three-dimensional solid model with geometric errors due to importing it into the finite element simulation software. It can be seen that the application of the technical solution provided by this embodiment can improve the accuracy of the finite element calculation results.

[0070] After completing the above Figure 1 Following the flowchart, as an embodiment, the implementation of step 104 may include the following steps:

[0071] Step A: Fitting the point cloud data using a specified surface fitting algorithm to obtain an interpolated surface with geometric errors.

[0072] In this embodiment, the specified surface fitting algorithm may be a Newton-Raphson interpolation algorithm, a Granger interpolation algorithm, or a polynomial interpolation algorithm, which is not limited in this embodiment.

[0073] Step B: performing Bezier clipping on the interpolation surface to obtain a Bezier surface.

[0074] Bezier clipping involves multiple insertions and node refinement of the interpolated surface's node vector, clipping the original interpolated surface into multiple Bezier subsurfaces. This allows for faster iteration by leveraging the superior geometric properties of Bezier surfaces. Based on this, Bezier clipping of the interpolated surface yields multiple Bezier subsurfaces, each of which serves as the Bezier surface for this step.

[0075] Step C: performing control polygon vertex detection on the Bezier surface to obtain a valid Bezier surface.

[0076] The control polygon formed by the Bezier surface has multiple solution domains in certain areas. By detecting the vertex of the control polygon and using the vector dot product, we can determine whether each Bezier surface has a unique solution domain, and further obtain a valid Bezier surface with a unique solution domain, so that the initial value of the iteration can be solved more efficiently.

[0077] Step D: determining a candidate Bezier surface for the point to be projected based on the coordinate value of the point to be projected and the valid Bezier surfaces.

[0078] The points to be projected are the contact surface nodes extracted from the meshed ideal three-dimensional model.

[0079] In this embodiment, a candidate Bezier surface must be a valid Bezier surface, but a valid Bezier surface is not necessarily a candidate Bezier surface.

[0080] The closer the coordinate value of the point to be projected is to the effective Bezier surface, the closer the coordinate value is to the initial value of the iteration.

[0081] Step E: obtaining an approximate point of the point to be projected in the Bezier surface according to the correspondence between the point to be projected and the candidate Bezier surface, and determining the approximate point as an initial value of iteration.

[0082] In this embodiment, the correspondence between the point to be projected and the candidate Bezier surface refers to the correspondence between the point to be projected and the Bezier surface, that is, the point to be projected is on the Bezier surface, but not on the boundary of the surface.

[0083] Step F, using the iterative initial value, iteratively solves the set iterative equation to obtain the node sag value of the fitted point cloud data.

[0084] In some embodiments, the implementation of step B may include the following steps:

[0085] Step B1: Obtain endpoint parameters forming the interpolation surface from the interpolation surface, and calculate the repetition of the endpoint parameters. The repetition can be understood as the number of times the endpoint parameters appear.

[0086] Step B2: Perform node insertion and refinement processing on the nodes of the interpolation surface. If the repetition of the nodes in the interpolation surface after interpolation reaches a set threshold, the interpolation surface after interpolation is clipped into a Bezier surface. If the repetition of the nodes in the interpolation surface after interpolation does not reach the set threshold, return to the step of performing node insertion and refinement processing on the nodes of the interpolation surface.

[0087] In this embodiment, the node insertion and refinement process can be understood as inserting multiple nodes between each node of the interpolation surface and the nodes adjacent to the node.

[0088] When the repetition of nodes in the interpolated surface reaches the set threshold, it means that the Bezier surfaces into which the original interpolated surface is divided are all valid Bezier surfaces. In other words, the original interpolated surface is divided into a group of surfaces composed of valid Bezier surfaces. At this time, the interpolated surface is degenerated into pieced Bezier sub-surface patches.

[0089] When the repetition of the nodes in the interpolated surface after interpolation does not reach the set threshold, it means that the Bezier surfaces into which the original interpolated surface is divided may contain invalid Bezier surfaces, and the interpolated surface needs to be repeatedly inserted. By repeatedly inserting all the nodes in the interpolated surface node vector multiple times, the repetition of the nodes in the interpolated surface after interpolation reaches the set threshold, so that the original interpolated surface is divided into a group of surfaces composed of valid Bezier surfaces.

[0090] As an embodiment, the implementation of step C may include the following steps:

[0091] Step C1: obtaining a plurality of control polygons from the Bezier surface, sorting the plurality of control polygons, and determining the sorted control polygon vertices as initial control polygon vertices.

[0092] In this embodiment, the sorted control polygons are all initial control polygons.

[0093] In step C2, the first initial control polygon vertex is used as the current control polygon vertex, and a dot product calculation is performed on the current control polygon vertex to obtain a vector dot product result. If the vector dot product result is a negative number, the process returns to step B; if the vector dot product result is a positive number, the process proceeds to step C3.

[0094] This step is executed one by one according to steps C2 to C3 in the sorting order of the initial control polygon vertices. If the vector dot product result obtained by calculating the vector dot product of the initial control polygon vertices is negative, there is no need to continue the dot product calculation, and directly return to step B to re-perform Bezier clipping on the interpolation surface to obtain a new Bezier surface.

[0095] As an embodiment, a vector dot product method is used to perform dot product calculation on the vertices of the current control polygon to obtain a vector dot product result.

[0096] Step C3, determining whether the current control polygon vertex is the last initial control polygon vertex in the sorting, if not, executing step C4; if so, executing step C5.

[0097] If not, it can be determined that the dot product results of the vectors corresponding to the initial control polygon vertices that are arranged before the current control polygon vertex are all positive numbers.

[0098] If so, it can be determined that the vector dot product results corresponding to all initial control polygon vertices are positive.

[0099] Step C4: Use the next initial control polygon vertex as the new current control polygon vertex, and return to the step of performing dot product calculation on the current control polygon vertex in step C2.

[0100] This step requires determining whether the next initial control polygon vertex is a valid control polygon.

[0101] Step C5: determining each initial control polygon as a valid control polygon, and using the valid control polygon to form a valid Bezier surface.

[0102] In this step, each initial control polygon is a valid control polygon. Thus, it can be considered that a valid Bezier surface can be constructed using the initial control polygons.

[0103] As another embodiment, the implementation of step C may include the following steps:

[0104] Multiple control polygons are obtained from the Bézier surface, and the vertices of each control polygon are determined as initial control polygon vertices. For each initial control polygon vertex, a dot product is calculated for the current control polygon vertex to obtain a vector dot product result. It is then determined whether the vector dot product results obtained from the dot product calculations for all the initial control polygon vertices are all positive. If any of the vector dot product results are negative, the process returns to step B. If all of the vector dot product results are positive, the current control polygon is determined as a valid control polygon, and the valid control polygon is used to form a valid Bézier surface.

[0105] In some embodiments, the implementation of step D may include the following steps:

[0106] Step D1, for each valid Bezier surface, determine whether the valid control polygon in the valid Bezier surface meets the set candidate surface conditions of the feature polygon. If yes, execute step D2; if not, execute step D3.

[0107] In this embodiment, the candidate curved surface condition of the feature polygon is that the to-be-projected point falls within the range of the control polygon but does not fall on the boundary of the control polygon.

[0108] Step D2: Determine the valid Bezier surface as a candidate Bezier surface.

[0109] Step D3: Eliminate the valid Bezier surface.

[0110] In this embodiment, the remaining valid Bezier surfaces after eliminating valid Bezier surfaces are candidate Bezier surfaces. Since valid Bezier surfaces have already been tested for control polygon vertices, a unique solution domain is guaranteed. This means that the technical solution proposed in this embodiment can identify candidate Bezier surfaces without eliminating all valid Bezier surfaces.

[0111] In some other embodiments, the method for implementing step E of obtaining an approximate point of the point to be projected on the Bezier surface according to the correspondence between the point to be projected and the candidate Bezier surface includes the following steps:

[0112] In step E1, nodes are inserted and thinned for each candidate Bezier surface corresponding to the point to be projected, to obtain control points of the candidate Bezier surface.

[0113] In step E2, it is determined whether the control grid composed of the control points reaches the recursion limit threshold. If so, step E3 is executed. If not, the process returns to step B2.

[0114] The recursion limit threshold can be determined based on the measurement accuracy of the point cloud data. A smaller recursion limit threshold means more iterations and more accurate initial values, but the calculation time will increase. A larger recursion limit threshold means fewer iterations and less accurate initial values, but the calculation time will decrease. How to determine the appropriate recursion limit threshold can be determined based on multiple empirical values.

[0115] Step E3: Use the control point to determine the approximate point of the point to be projected.

[0116] See also Figure 2 , Figure 2A schematic structural diagram of an automatic error grid generation device 200 is provided, wherein the error grid generation device comprises:

[0117] A meshing processing unit 201 is used to obtain an ideal three-dimensional model for a specified assembly and mesh the ideal three-dimensional model;

[0118] A node coordinate extraction unit 202 is used to extract node coordinate values ​​of contact surface nodes from the gridded ideal three-dimensional model;

[0119] A point cloud data obtaining unit 203 is used to obtain point cloud data of the specified assembly measured on the contact surface;

[0120] The node sag value obtaining unit 204 is used to perform interpolation fitting on the point cloud data to obtain the node sag values ​​of the fitted point cloud data;

[0121] The meshed solid model generating unit 205 is configured to replace the node coordinate values ​​with the node sag values, so as to generate a meshed solid model with geometric errors using the replaced nodes.

[0122] As an embodiment, the node sag value obtaining unit 204 includes:

[0123] An interpolation surface obtaining subunit is used to fit the point cloud data using a specified surface fitting algorithm to obtain an interpolation surface with geometric errors;

[0124] A Bezier surface obtaining subunit is used to perform Bezier clipping on the interpolation surface to obtain a Bezier surface;

[0125] A valid Bezier surface obtaining subunit, configured to perform control polygon vertex detection on the Bezier surface to obtain a valid Bezier surface;

[0126] A candidate Bezier surface obtaining subunit is used to determine a candidate Bezier surface of the point to be projected based on the coordinate value of the point to be projected and the valid Bezier surface; the point to be projected is a contact surface node extracted from the gridded ideal three-dimensional model;

[0127] an iteration initial value determination subunit, configured to obtain an approximate point of the point to be projected on the Bezier surface according to a correspondence between the point to be projected and the candidate Bezier surface, and determine the approximate point as an iteration initial value;

[0128] The node sag value obtaining subunit is used to iteratively solve the set iterative equation using the iterative initial value to obtain the node sag value of the fitted point cloud data.

[0129] As an embodiment, the Bezier surface subunit is used to:

[0130] Acquiring endpoint parameters forming the interpolation surface from the interpolation surface, and calculating the repeatability of the endpoint parameters;

[0131] Perform node insertion and refinement processing on the nodes of the interpolation surface. If the repetition of the nodes in the interpolation surface after interpolation reaches a set threshold, the interpolation surface after interpolation is clipped into a Bezier surface; if the repetition of the nodes in the interpolation surface after interpolation does not reach the set threshold, return to the step of performing node insertion and refinement processing on the nodes of the interpolation surface.

[0132] As an embodiment, the effective Bezier surface obtaining subunit is used to:

[0133] Acquire multiple control polygons from the Bezier surface, sort the multiple control polygon vertices, and determine the sorted control polygon vertices as initial control polygon vertices;

[0134] For each initial polygon vertex, the initial control polygon vertex is used as the current control polygon vertex, and a dot product calculation is performed on the current control polygon vertex to obtain a vector dot product result. If the vector dot product result is a negative number, the step of performing Bezier clipping on the interpolation surface is returned to execution; if the vector dot product result is a positive number, it is determined whether the current control polygon vertex is the last initial control polygon vertex in the sorting; if not, the next initial control polygon vertex is used as the new current control polygon vertex, and the step of performing dot product calculation on the current control polygon vertex is returned to execution; if so, each initial control polygon is determined as a valid control polygon, so as to form a valid Bezier surface using the valid control polygon.

[0135] As an embodiment, the candidate Bezier surface obtaining subunit is used to:

[0136] For each valid Bezier surface, determine whether the valid control polygon in the valid Bezier surface meets the set candidate surface condition of the feature polygon. If so, the valid Bezier surface is determined as a candidate Bezier surface; if not, the valid Bezier surface is eliminated; wherein, the candidate surface condition of the feature polygon is that the point to be projected falls within the range of the control polygon but does not include falling on the boundary of the control polygon.

[0137] As an embodiment, the iterative initial value determination subunit is used to:

[0138] The candidate Bezier surface corresponding to each point to be projected is subdivided recursively to obtain the control points of the candidate Bezier surface;

[0139] Determine whether the control grid composed of the control points reaches the recursive limit threshold. If so, determine the control points as approximate points of the points to be projected. If not, return to the step of performing node insertion and refinement on the nodes of the interpolation surface.

[0140] It can be seen that in the technical solution of the embodiment of the present application, when generating the error grid, the ideal three-dimensional model for the specified assembly is first obtained, and the ideal three-dimensional model is meshed. Then, the node coordinate values ​​of the contact surface nodes are extracted from the meshed ideal three-dimensional model; the point cloud data of the specified assembly measured for the contact surface is obtained; the point cloud data is interpolated and fitted to obtain the node sag values ​​of the fitted point cloud data; finally, the node coordinate values ​​are replaced with the node sag values, so that the replaced nodes are used to generate a meshed solid model with geometric errors. It can be seen that the technical solution provided by this embodiment is to directly map the measured data with geometric errors to the contact surface of the ideal three-dimensional mesh model, thereby realizing the automatic update of the finite element mesh model with geometric errors, avoiding the loss of accuracy of the three-dimensional solid model with geometric errors due to importing it into the finite element simulation software. It can be seen that the application of the technical solution provided by this embodiment can improve the accuracy of the finite element calculation results.

[0141] The implementation process of the functions and effects of each unit in the above-mentioned device is specifically described in the implementation process of the corresponding steps in the above-mentioned method, and will not be repeated here.

[0142] The electronic device provided in the embodiment of the present application, from the hardware level, can be seen in the hardware architecture diagram. Figure 3 The invention comprises: a machine-readable storage medium and a processor, wherein: the machine-readable storage medium stores machine-executable instructions that can be executed by the processor; the processor is configured to execute the machine-executable instructions to implement the error grid generation operation disclosed in the above example.

[0143] The machine-readable storage medium provided in an embodiment of the present application stores machine-executable instructions. When the machine-executable instructions are called and executed by a processor, the machine-executable instructions prompt the processor to implement the error grid generation operation disclosed in the above example.

[0144] Here, the machine-readable storage medium can be any electronic, magnetic, optical or other physical storage device that can contain or store information, such as executable instructions, data, etc. For example, the machine-readable storage medium can be: RAM (Random Access Memory), volatile memory, non-volatile memory, flash memory, storage drive (such as hard disk drive), solid state drive, any type of storage disk (such as CD, DVD, etc.), or similar storage media, or a combination thereof.

[0145] The systems, devices, modules, or units described in the above embodiments may be implemented by computer chips or entities, or by products having certain functions. A typical implementation device is a computer, which may be in the form of a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email transceiver, game console, tablet computer, wearable device, or any combination of these devices.

[0146] For the convenience of description, the above devices are described as being divided into various units according to their functions. Of course, when implementing this application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0147] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the embodiments of the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0148] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0149] Furthermore, these computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0150] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for executing on the computer or other programmable device to implement the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0151] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to the partial description of the method embodiments. The device embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present application scheme. A person of ordinary skill in the art can understand and implement it without paying any creative work.

[0152] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for generating an error grid, characterized in that: The error grid generation method comprises: Obtaining an ideal three-dimensional model for a specified assembly and meshing the ideal three-dimensional model; Extract node coordinate values ​​of designated contact surface nodes from the meshed ideal three-dimensional model; Obtaining point cloud data with geometric errors of actual measurement of the designated contact surface; Performing interpolation fitting on the point cloud data to obtain a node sagittal value with geometric error on the specified contact surface after fitting; The node coordinate values ​​are replaced with the node sag values, so as to generate a meshed solid model with geometric errors using the replaced nodes.

2. The error grid generation method according to claim 1, characterized in that: The interpolation fitting is performed on the point cloud data to obtain node sag values ​​of the fitted point cloud data, including: Fitting the point cloud data using a specified surface fitting algorithm to obtain an interpolated surface with geometric errors; Performing Bezier clipping on the interpolation surface to obtain a Bezier surface; Performing control polygon vertex detection on the Bezier surface to obtain a valid Bezier surface; Determining a candidate Bezier surface for the point to be projected based on the coordinate value of the point to be projected and a valid Bezier surface; the point to be projected is a contact surface node extracted from the gridded ideal three-dimensional model; Obtaining an approximate point of the point to be projected on the Bezier surface according to a correspondence between the point to be projected and the candidate Bezier surface, and determining the approximate point as an initial value for iteration; The iterative initial value is used to iteratively solve the set iterative equation to obtain the node sag value of the fitted point cloud data.

3. The error grid generation method according to claim 2, characterized in that: The step of performing Bezier clipping on the interpolation surface to obtain a Bezier surface includes: Acquiring endpoint parameters forming the interpolation surface from the interpolation surface, and calculating the repeatability of the endpoint parameters; Perform node insertion and refinement processing on the nodes of the interpolation surface. If the repetition of the nodes in the interpolation surface after interpolation reaches a set threshold, the interpolation surface after interpolation is clipped into a Bezier surface; if the repetition of the nodes in the interpolation surface after interpolation does not reach the set threshold, return to the step of performing node insertion and refinement processing on the nodes of the interpolation surface.

4. The error grid generation method according to claim 2, characterized in that: The step of performing control polygon vertex detection on the Bezier surface to obtain a valid Bezier surface includes: Acquire multiple control polygons from the Bezier surface, sort the multiple control polygon vertices, and determine the sorted control polygon vertices as initial control polygon vertices; For each initial control polygon vertex, use the initial control polygon vertex as the current control polygon vertex, perform dot product calculation on the current control polygon vertex, and obtain a vector dot product result. If the vector dot product result is a negative number, return to execute the step of performing Bezier clipping on the interpolation surface; if the vector dot product result is a positive number, determine whether the current control polygon vertex is the last initial control polygon vertex in the sorting; if not, use the next initial control polygon vertex as the new current control polygon vertex, and return to execute the step of performing dot product calculation on the current control polygon vertex; if so, determine each initial control polygon as a valid control polygon, and use the valid control polygon to form a valid Bezier surface.

5. The error grid generation method according to claim 2, characterized in that: The step of determining a candidate Bezier surface for the point to be projected based on the coordinate value of the point to be projected and the valid Bezier surface comprises: For each valid Bezier surface, determine whether the valid control polygon in the valid Bezier surface meets the set candidate surface condition of the feature polygon. If so, the valid Bezier surface is determined as a candidate Bezier surface; if not, the valid Bezier surface is eliminated; wherein, the candidate surface condition of the feature polygon is that the point to be projected falls within the range of the control polygon but does not include falling on the boundary of the control polygon.

6. The error grid generation method according to claim 2, characterized in that: The obtaining an approximate point of the point to be projected on the Bezier surface according to the correspondence between the point to be projected and the candidate Bezier surface includes: The candidate Bezier surface corresponding to each point to be projected is subdivided recursively to obtain the control points of the candidate Bezier surface; Determine whether the control grid composed of the control points reaches the recursive limit threshold. If so, determine the control points as approximate points of the points to be projected. If not, return to the step of performing node insertion and refinement on the nodes of the interpolation surface.

7. An error grid generation device, characterized in that: The error grid generating device comprises: A meshing processing unit, configured to obtain an ideal three-dimensional model for a specified assembly and mesh the ideal three-dimensional model; A node coordinate extraction unit is used to extract node coordinate values ​​of designated contact surface nodes from the gridded ideal three-dimensional model; A point cloud data acquisition unit, configured to obtain point cloud data with geometric errors actually measured on the designated contact surface; A node sag value obtaining unit is used to perform interpolation fitting on the point cloud data to obtain a node sag value with geometric error of the specified contact surface after fitting; The grid entity model generating unit is used to replace the node coordinate values ​​with the node sag values, so as to generate a grid entity model with geometric errors using the replaced nodes.

8. The error grid generating device according to claim 7, characterized in that: The node sag value obtaining unit includes: An interpolation surface obtaining subunit is used to fit the point cloud data using a specified surface fitting algorithm to obtain an interpolation surface with geometric errors; A Bezier surface obtaining subunit is used to perform Bezier clipping on the interpolation surface to obtain a Bezier surface; A valid Bezier surface obtaining subunit, configured to perform control polygon vertex detection on the Bezier surface to obtain a valid Bezier surface; A candidate Bezier surface obtaining subunit is used to determine a candidate Bezier surface of the point to be projected based on the coordinate value of the point to be projected and the valid Bezier surface; the point to be projected is a contact surface node extracted from the gridded ideal three-dimensional model; an iteration initial value determination subunit, configured to obtain an approximate point of the point to be projected on the Bezier surface according to a correspondence between the point to be projected and the candidate Bezier surface, and determine the approximate point as an iteration initial value; The node sag value obtaining subunit is used to iteratively solve the set iterative equation using the iterative initial value to obtain the node sag value of the fitted point cloud data.

9. The error grid generating device according to claim 8, characterized in that: The Bezier surface subunit is used to: Acquiring endpoint parameters forming the interpolation surface from the interpolation surface, and calculating the repeatability of the endpoint parameters; Perform node insertion and refinement processing on the nodes of the interpolation surface. If the repetition of the nodes in the interpolation surface after interpolation reaches a set threshold, the interpolation surface after interpolation is clipped into a Bezier surface; if the repetition of the nodes in the interpolation surface after interpolation does not reach the set threshold, return to the step of performing node insertion and refinement processing on the nodes of the interpolation surface.

10. An electronic device, characterized in that: The invention comprises a processor and a machine-readable storage medium, wherein the machine-readable storage medium stores machine-executable instructions that can be executed by the processor; the processor is used to execute the machine-executable instructions to implement the error grid generation method according to any one of claims 1 to 6.

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