Parametric and direct modeling seamless integrated cad hybrid modeling and manufacturing method

Abstract

The application discloses a CAD hybrid modeling and manufacturing method of parameterization and direct modeling seamless integration. User inputs CAD model information and modification operation, and generates an original CAD model from the CAD model information; geometric-topological inconsistency detection is performed on the CAD model information after the modification operation, and then the detected local geometric information and topological information are sent to a geometric-topological inconsistency processing module for correction and processing; the processed CAD model is received, and then geometric-constraint inconsistency detection and processing are performed; if geometric-constraint inconsistency problems exist, the detected local geometric information and constraint information are sent to a geometric-constraint inconsistency processing module for correction. The method can solve the information inconsistency problem under the hybrid operation of parameterization and direct modeling, and ensures the effectiveness of the CAD model under the hybrid operation of parameterization modeling and direct modeling.

Description

Technical Field

[0001] This invention relates to a modeling and manufacturing method in the field of computer-aided design (CAD) systems. It proposes a manufacturing method for high-end manufacturing products that integrates CAD hybrid modeling and parametric modeling with direct modeling. Background Technology

[0002] Computer-aided design systems have become a primary tool for product design. Their core purpose is to build and edit CAD models of products. CAD modeling technology has undergone three main developmental stages: solid modeling, parametric modeling, and direct modeling. Solid modeling originated in the 1970s and has two main methods: Constructive Solid Geometry (CSG) and Boundary Representation (B-rep). These methods respectively developed into the later dominant parametric modeling and direct modeling techniques.

[0003] Constructive solid geometry represents CAD models as a combination of basic shapes (e.g., cuboids, spheres, cylinders). Parametric modeling inherits this combinatorial approach while introducing the concept of features to replace these basic shapes. Compared to basic shapes, features possess both basic shape information and high-level design semantic information (e.g., symmetry between shapes). This high-level design semantic enables parametric modeling to modify models through parameter-driven mechanisms. However, this high-level design semantic also introduces high complexity and inflexibility into CAD modeling. Ordinary users often find it difficult to effectively edit CAD models, thus perceiving parametric modeling as difficult to learn and use.

[0004] Boundary representation uses the boundaries of the geometric space occupied by the product to construct the CAD model. Direct modeling allows users to directly manipulate this boundary information to modify the CAD model. Through direct modeling, users can flexibly modify boundary information, transforming the CAD model into arbitrary shapes. However, this advantage comes at a significant cost: direct modeling lacks high-level design semantics, thus sacrificing the ability to modify models through parameter-driven methods—a capability essential for the digital design of modern high-end manufactured products.

[0005] Parametric modeling and direct modeling techniques have complementary advantages and disadvantages. Integrating them can combine the strengths of both, offering both parametrically driven model modification capabilities and high modeling flexibility. However, seamless integration is not straightforward: CAD models contain various types of information, and parametric and direct modeling operate on different types of information respectively, leading to inconsistencies between these types of information and ultimately resulting in a failed CAD model.

[0006] Therefore, the problem with existing technologies is that the fundamental issue in seamlessly integrating parametric modeling and direct modeling lies in handling the inconsistencies in information under mixed parametric and direct modeling operations, which cannot ensure the validity of CAD models. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a CAD hybrid modeling and manufacturing method that seamlessly integrates parametric and direct modeling.

[0008] The method of this invention is designed for high-end manufactured products and is a seamless integration of parameterization and direct modeling of high-end manufactured products.

[0009] This invention, guided by the user's input of product CAD model information through the CAD system interface and the hybrid operation of parametric and direct modeling, can intelligently process inconsistent information in the CAD model, ensuring the validity of the CAD model.

[0010] The products described in this invention are all high-end manufactured products.

[0011] To achieve the above objectives, the technical solution adopted by the present invention specifically includes the following three steps:

[0012] 1) Users input CAD model information and modify the CAD model information through the system's CAD user interface, and the original CAD model is generated from the CAD model information;

[0013] 2) Perform geometry-topology inconsistency detection and handling based on the modification operations:

[0014] Step 2) involves first performing geometry-topology inconsistency detection on the modified CAD model information, and then sending the detected local geometry and topology information to the geometry-topology inconsistency processing module for correction.

[0015] 3) Geometric-Constraint Inconsistency Detection and Handling

[0016] Step 3) first accepts the CAD model processed in the previous step, and then performs geometry-constraint inconsistency detection and processing to detect whether there are geometry-constraint inconsistencies. If there are geometry-constraint inconsistencies, the detected local geometry information and constraint information are sent to the geometry-constraint inconsistency processing module for correction.

[0017] 4) Manufacturing of product CAD models

[0018] The CAD model obtained in step 3) is used for actual production and manufacturing. This can be done using CNC machine tools or other manufacturing methods.

[0019] The CAD model information includes geometric information (including geometric elements and geometric parameters), topological information (including connection relationships), and constraint information (including positioning constraints, geometric constraints, and algebraic constraints).

[0020] The modification operation is one of parametric modeling operations and direct modeling operations, or a combination of both.

[0021] The geometric-topological inconsistency detection and processing in step 2) includes repeating the following two steps:

[0022] 2.1) Detect the critical point where geometric-topological inconsistencies are about to occur;

[0023] 2.2) Based on the result of step 2.1), make the following judgment:

[0024] If a critical point is detected, the CAD model is updated at the critical point;

[0025] If no critical point is detected, the CAD model is regenerated based on the user's original topological information and the geometric information of the user's original input is processed using a general surface trimming method to update the geometric and topological information in the CAD model.

[0026] Step 2.1) specifically involves the following three steps:

[0027] 2.1.1) First, extract the local geometric and topological information involved in the modification operations of the CAD model information;

[0028] 2.1.2) Secondly, based on the extracted local geometric and topological information, a heuristic method is used to generate all possible inconsistencies between the information;

[0029] 2.1.3) Finally, for the modification operation, a screening method is used to check which of the above-generated inconsistencies actually occurred, and the time point of the earliest logically occurring inconsistency is selected as the geometric-topological inconsistency critical point.

[0030] In step 2.2), if a critical point is detected, the specific steps are as follows:

[0031] 2.2.1) First, extract the local geometric and topological information closely related to the detected geometric-topological inconsistency critical points (hereinafter referred to as critical points);

[0032] 2.2.2) Secondly, the extracted local geometric and topological information is used to generate an auxiliary CAD model at the critical point using a general surface trimming method;

[0033] 2.2.3) Finally, perform Boolean operations between the user's original input CAD model and the auxiliary CAD model constructed in step 2.2.2) to generate a new CAD model and update the CAD model.

[0034] The geometric-constraint inconsistency detection and processing in step 3) specifically involves the following three steps:

[0035] 3.1) Detect the constraint status of the CAD model and classify it into different types;

[0036] The detection criterion for geometric-constraint inconsistency is that the constraint information no longer exhibits a properly defined constraint state, but instead manifests as an underdefined or overdefined constraint state. This invention first submits the modified CAD model to an analyzer to analyze its constraint state. If the model is in a properly defined constraint state, no inconsistency handling is required; otherwise, the workflow is divided into two processing branches: (1) if the system detects that the model is in an underdefined constraint state, the underdefined constraint handling module is invoked; (2) if the system detects that the model is in an overdefined constraint state, the overdefined constraint handling module is invoked. The outputs of both processing modules are a set of inconsistency handling schemes prioritized by the user, which are then presented to the user for optimization selection.

[0037] 3.2) Optimize and update the CAD model based on its different constraint states:

[0038] If the CAD model is in a well-defined constraint state, no information inconsistency handling is required;

[0039] If the CAD model is in an undetermined constraint state, perform the following two steps:

[0040] If the CAD model is in an underdetermined constraint state, the underdetermined constraint handling module is invoked to update the CAD model.

[0041] If the CAD model is in an over-constraint state, the over-constraint handling module is called to update the CAD model.

[0042] The specific steps of step 3.1) are as follows:

[0043] 3.1.1) First, convert the constraint information in the CAD model into a system of algebraic equations;

[0044] 3.1.2) Next, check and determine the Jacobian matrix of the system of algebraic equations:

[0045] If the rank of the Jacobian matrix is ​​less than the number of its rows, the CAD model is in an over-constrained state.

[0046] If the dimension of the null space of the Jacobian matrix is ​​greater than 6, the CAD model is in an underconstrained state.

[0047] If neither of these conditions falls under over-constraint nor under-constraint, then the CAD model is in a properly constrained state.

[0048] In step 3.2), when the CAD model is in an underdetermined or overdetermined constraint state, it shall be handled in the following manner:

[0049] 3.2.1.1) First, extract the geometric and constraint information under different constraint states;

[0050] 3.2.1.2) Secondly, using the extracted geometric and constraint information, a heuristic method is employed to generate all possible solutions for handling geometric-constraint inconsistencies;

[0051] 3.2.1.3) All generated geometry-constraint inconsistency handling schemes are screened again, and those that contradict the geometry and constraint information in the original CAD model are removed;

[0052] 3.2.1.4) Finally, the remaining geometric-constraint inconsistency handling schemes are sorted, and the sorting method consists of one qualitative sort and one quantitative sort in sequence.

[0053] 3.2.1.5) Output the sorting results and let the user select a geometry-constraint inconsistency handling scheme, or select the first geometry-constraint inconsistency handling scheme from the sorting results, and update the CAD model with the final geometry-constraint inconsistency handling scheme.

[0054] Guided by the product CAD model information (mainly including geometric, topological, and constraint information) input by the user through the CAD system interface and the corresponding model modification operations (which can be parametric modeling operations or direct modeling operations), this invention adopts a method of detection and then processing for inconsistencies between geometric and topological information (referred to as geometric-topological inconsistency) and between geometric and constraint information (referred to as geometric-constraint inconsistency) caused by model modification operations. Ultimately, this ensures that the CAD model remains valid under any modification operation, thereby achieving seamless integration of parametric modeling technology and direct modeling technology.

[0055] The beneficial effects of this invention are:

[0056] This invention addresses information inconsistencies in CAD models in a systematic way, achieving advantages over existing commercial CAD software in terms of CAD model operation flexibility and parameter-driven model modification. Because it enables intuitive interaction between the user and the CAD model, this invention effectively utilizes CAD modeling tools in the early and conceptual stages of engineering design.

[0057] The method of this invention can simultaneously solve the information inconsistency problem under the mixed operation of parametric modeling and direct modeling, ensuring that the CAD model remains effective under the mixed operation of parametric modeling and direct modeling. Attached Figure Description

[0058] Figure 1 This is the overall flowchart of the present invention.

[0059] Figure 2 This is a flowchart of the process for detecting and handling geometric-topological inconsistencies.

[0060] Figure 3 This is a flowchart of the process for detecting and handling geometric-constraint inconsistencies. Detailed Implementation

[0061] The invention will now be further described with reference to the accompanying drawings.

[0062] like Figure 1 As shown, the implementation process and circumstances of this invention according to the complete method described above are as follows:

[0063] 1) Users input CAD model information and modify the CAD model information through the system's CAD user interface, and the original CAD model is generated from the CAD model information;

[0064] Users can also input parametric modeling operations or direct modeling operations to modify this model information. The user interface design is consistent with existing commercial CAD software.

[0065] 2) Perform geometry-topology inconsistency detection and handling based on the modification operations:

[0066] Step 2) First, perform geometry-topology inconsistency detection on the modified CAD model information, and then send the detected local geometry and topology information to the geometry-topology inconsistency processing module for correction.

[0067] like Figure 2 As shown, the geometric-topological inconsistency detection and processing in step 2) adopts a progressive approach, which includes repeating the following two steps:

[0068] 2.1) Detect the critical point where geometric-topological inconsistencies are about to occur;

[0069] A heuristic approach was used to detect the next geometry-topology inconsistency critical point, which involved the following three steps:

[0070] 2.1.1) First, extract the local geometric and topological information involved in the modification operations of the CAD model information;

[0071] 2.1.2) Secondly, based on the extracted local geometric and topological information, a heuristic method is used to generate all possible inconsistencies between the information;

[0072] 2.1.3) Finally, for the modification operation given by the user, the filtering method is used to check which of the above-generated inconsistencies actually occurred, and the time point of the earliest logically occurring inconsistency is selected as the geometric-topological inconsistency critical point as the critical point at which geometric-topological inconsistency will occur.

[0073] 2.2) Based on the result of step 2.1), make the following judgment:

[0074] If a critical point is detected, the detected inconsistency is handled directly at the critical point, i.e., the geometry-topology inconsistency problem, and the CAD model is updated.

[0075] If no critical point is detected, the CAD model is regenerated based on the user's original topological information and the geometric information of the user's original input is processed using a general surface trimming method to update the geometric and topological information in the CAD model, which is then used in step 3).

[0076] In practice, steps 2.1) and 2.2) can be repeated continuously to detect the next critical point and update it, until no critical point can be detected.

[0077] In step 2.2), if a critical point is detected, a Boolean approach is used to handle the inconsistency between geometric and topological information, specifically:

[0078] 2.2.1) First, extract the local geometric and topological information closely related to the detected geometric-topological inconsistency critical points (hereinafter referred to as critical points);

[0079] 2.2.2) Secondly, the extracted local geometric and topological information is used to generate an auxiliary CAD model at the critical point using a general surface trimming method;

[0080] 2.2.3) Finally, Boolean operations are performed between the user's original input CAD model and the auxiliary CAD model constructed in step 2.2.2) to generate a new CAD model and update the CAD model, which is the result model obtained after geometry-topology inconsistency processing.

[0081] 3) Geometric-Constraint Inconsistency Detection and Handling

[0082] Step 3) first accepts the CAD model processed in the previous step, and then performs geometry-constraint inconsistency detection and processing. It detects whether there are geometry-constraint inconsistencies. If there are geometry-constraint inconsistencies, the detected local geometry information and constraint information are sent to the geometry-constraint inconsistency processing module for correction; otherwise, no processing is performed.

[0083] like Figure 3 As shown, the geometric-constraint inconsistency detection and handling in step 3) adopts a divide-and-conquer approach, specifically performing the following three steps:

[0084] 3.1) Detect the constraint status of the CAD model and classify it into different types;

[0085] A linear perturbation method was used to detect inconsistencies in geometric-constraint information and determine the constraint state of the modified CAD model. The specific steps are as follows:

[0086] 3.1.1) First, convert the constraint information in the CAD model into a system of algebraic equations;

[0087] 3.1.2) Next, check and determine the Jacobian matrix of the system of algebraic equations:

[0088] If the rank of the Jacobian matrix is ​​less than the number of its rows, the CAD model is in an over-constrained state.

[0089] If the dimension of the null space of the Jacobian matrix is ​​greater than 6, the CAD model is in an underconstrained state.

[0090] If neither of these conditions falls under over-constraint nor under-constraint, then the CAD model is in a properly constrained state.

[0091] 3.2) Optimize and update the CAD model based on its different constraint states:

[0092] If the CAD model is in a well-defined constraint state, no information inconsistency handling is required, and the process ends.

[0093] If the CAD model is in an undetermined constraint state, perform the following two steps:

[0094] If the CAD model is in an underdetermined constraint state, the underdetermined constraint handling module is invoked to update the CAD model.

[0095] If the CAD model is in an over-constraint state, the over-constraint handling module is called to update the CAD model.

[0096] In step 3.2), the underdetermined constraint processing module and the over-constraint processing module apply a method that combines qualitative and quantitative processing to generate geometric-constraint inconsistency processing schemes and sort them.

[0097] In step 3.2), when the CAD model is in an underdetermined or overdetermined constraint state, it shall be handled in the following manner, executing the following four steps:

[0098] 3.2.1.1) First, extract the geometric and constraint information under different constraint states;

[0099] 3.2.1.2) Secondly, using the extracted geometric and constraint information, a heuristic method is employed to generate all possible solutions for handling geometric-constraint inconsistencies;

[0100] 3.2.1.3) All generated geometry-constraint inconsistency handling schemes are screened again, and those that contradict the geometry and constraint information in the original CAD model are removed;

[0101] 3.2.1.4) Finally, the remaining geometric-constraint inconsistency handling schemes are sorted by a sorting method consisting of one qualitative sort and one quantitative sort in sequence.

[0102] Qualitative sorting refers to sorting schemes based on a set of heuristic sorting processes built into the system.

[0103] Quantitative ranking refers to performing a sensitivity test on treatment schemes with the same priority in qualitative ranking, and sorting them from lowest to highest sensitivity, with the treatment schemes with lower sensitivity ranked first and the ones with higher sensitivity ranked last.

[0104] 3.2.1.5) Output the sorting results and let the user select a geometry-constraint inconsistency handling scheme, or select the first geometry-constraint inconsistency handling scheme from the sorting results, and update the CAD model with the final geometry-constraint inconsistency handling scheme.

[0105] Finally, the above sorted list of processing solutions is output. It can be left to the user for decision-making, or an automated working mode for handling geometric-constraint inconsistencies can be set up. In this mode, the first solution in the sorted list will be automatically selected.

[0106] 4) Manufacturing of product CAD models

[0107] The CAD model obtained in step 3) is used for actual production and manufacturing. This can be done using CNC machine tools or other manufacturing methods.

[0108] The process first accepts the CAD model information processed in the previous steps, then displays it on the user interface for further user operations. The specific display technology is consistent with existing commercial CAD software.

[0109] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A CAD hybrid modeling and manufacturing method that seamlessly integrates parametric and direct modeling, characterized in that: 1) Users input CAD model information and modify the CAD model information through the system's CAD user interface, and the original CAD model is generated from the CAD model information; 2) Geometric-topological inconsistency detection and handling, correction and updating of the CAD model: First, the modified CAD model information is subjected to geometry-topology inconsistency detection. Then, the detected local geometry and topology information is sent to the geometry-topology inconsistency processing module for correction. The geometric-topological inconsistency detection and processing in step 2) includes repeating the following two steps: 2.1) Detect the critical point where geometric-topological inconsistencies are about to occur; 2.2) Based on the result of step 2.1), make the following judgment: If a critical point is detected, the CAD model is updated at the critical point; If no critical point is detected, the CAD model is regenerated based on the user's original topological information and the geometric information of the user's original input is processed using a general surface trimming method to update the geometric and topological information in the CAD model. In step 2.2), if a critical point is detected, the specific steps are as follows: 2.2.1) First, extract the local geometric and topological information closely related to the detected critical points; 2.2.2) Secondly, the extracted local geometric and topological information is used to generate an auxiliary CAD model at the critical point using a general surface trimming method; 2.2.3) Finally, perform Boolean operations between the user's original input CAD model and the auxiliary CAD model constructed in step 2.2.2) to generate a new CAD model and update the CAD model; 3) Based on the CAD model processed in step 2), perform geometry-constraint inconsistency detection and handling, correct the issues, and update the CAD model: First, the CAD model processed in step 2) is accepted, and then geometric-constraint inconsistency detection and processing are performed. If geometric-constraint inconsistency problems exist, the detected local geometric information and constraint information are sent to the geometric-constraint inconsistency processing module for correction. The geometric-constraint inconsistency detection and processing in step 3) specifically involves the following three steps: 3.1) Detect the constraint status of the CAD model and classify it into different types; 3.2) Optimize and update the CAD model based on its different constraint states: If the CAD model is in a well-defined constraint state, no information inconsistency handling is required; If the CAD model is in an underdetermined constraint state, the underdetermined constraint handling module is invoked to update the CAD model. If the CAD model is in an over-constraint state, the over-constraint processing module is called to update the CAD model. 4) Manufacturing of product CAD models The CAD model obtained in step 3) is used for actual production and manufacturing; The CAD model information includes geometric information, topological information, and constraint information; The modification operation is one of parametric modeling operations and direct modeling operations, or a combination of both.

2. The CAD hybrid modeling and manufacturing method that seamlessly integrates parametric and direct modeling according to claim 1, characterized in that: Step 2.1) specifically involves the following three steps: 2.1.1) First, extract the local geometric and topological information involved in the modification operations of the CAD model information; 2.1.2) Secondly, based on the extracted local geometric and topological information, a heuristic method is used to generate all possible inconsistencies between the information; 2.1.3) Finally, for the modification operation, a screening method is used to check which of the above-generated inconsistencies actually occurred, and the time point of the earliest logically occurring inconsistency is selected as the geometric-topological inconsistency critical point.

3. The CAD hybrid modeling and manufacturing method that seamlessly integrates parametric and direct modeling according to claim 1, characterized in that: The specific steps of step 3.1 are as follows: 3.1.1) First, convert the constraint information in the CAD model into a system of algebraic equations; 3.1.2) Next, check and determine the Jacobian matrix of the system of algebraic equations: If the rank of the Jacobian matrix is ​​less than the number of its rows, the CAD model is in an over-constrained state. If the dimension of the null space of the Jacobian matrix is ​​greater than 6, the CAD model is in an underconstrained state. If neither of these conditions falls under over-constraint nor under-constraint, then the CAD model is in a properly constrained state.

4. The CAD hybrid modeling and manufacturing method that seamlessly integrates parametric and direct modeling according to claim 1, characterized in that: In step 3.2), when the CAD model is in an underdetermined or overdetermined constraint state, it shall be handled in the following manner: 3.2.1.1) First, extract the geometric and constraint information under different constraint states; 3.2.1.2) Secondly, using the extracted geometric and constraint information, a heuristic method is employed to generate all possible solutions for handling geometric-constraint inconsistencies; 3.2.1.3) All generated geometry-constraint inconsistency handling schemes are screened again, and those that contradict the geometry and constraint information in the original CAD model are removed; 3.2.1.4) Finally, the remaining geometric-constraint inconsistency handling schemes are sorted, and the sorting method consists of one qualitative sort and one quantitative sort in sequence; 3.2.1.5) Output the sorting results and let the user select a geometry-constraint inconsistency handling scheme, or select the first geometry-constraint inconsistency handling scheme from the sorting results, and update the CAD model with the final geometry-constraint inconsistency handling scheme.

Images