Automobile exterior three-view automatic generation and calibration method based on engineering constraints

Abstract

The application discloses an automotive exterior three-view automatic generation and calibration method based on engineering constraints, relates to the technical field of exterior views, and is used for solving the problem that the stability of a calibration process is reduced after three-view automatic generation, and through the acquisition of exterior contour data and the demarcation of contour sections, the engineering constraint type is marked at the contour section level, the constraint coverage coefficient and the view change feature are calculated under multi-view contour projection, the target contour section is screened, the contour adjustment direction change in the continuous calibration round is counted in the calibration iteration process, the direction stability index is generated and the contour conflict state is dynamically corrected, different contour calibration methods are selected according to the contour conflict state, the exterior contour data is updated after the calibration processing and the contour convergence amplitude is analyzed, whether the contour view checking mechanism is re-entered or the contour checking result is generated is judged by using the contour convergence amplitude, and the adaptive calibration of the exterior contour data under the multi-view condition is realized.

Description

Technical Field

[0001] This invention relates to the field of exterior view technology, and more specifically, to a method for automatic generation and calibration of three-view drawings of automotive exteriors based on engineering constraints. Background Technology

[0002] In the field of automotive exterior engineering design, the three views, namely the front view, side view, and top view, are important basic data for confirming the shape of exterior parts, engineering verification, and manufacturing delivery. With the platformization of the whole vehicle and the continuous increase in the complexity of exterior styling, exterior parts not only need to meet the requirements of styling continuity and aesthetics during the design process, but are also affected by a variety of engineering constraints such as assembly clearance, tolerance matching, symmetry relationship, structural interface and regulatory boundaries.

[0003] The existing technology has the following shortcomings:

[0004] Currently, existing technologies mostly employ unified projection rules or fixed weight constraint strategies based on 3D modeling data to automatically generate and verify the three-view drawings of automotive exteriors. These technologies lack segmented modeling of local contours at the exterior outline level and differentiated marking and management of different engineering constraint types. They also ignore the fact that the importance of engineering constraints borne by the same exterior contour varies in the front, side, and top views. As a result, after the three-view drawings are automatically generated, the local contours may not be able to simultaneously meet the requirements of multiple engineering constraints such as styling, assembly, and interfaces in different views, which can easily lead to reduced stability and decreased convergence efficiency in the calibration process. Therefore, this paper proposes an automatic generation and calibration method for automotive exterior three-view drawings based on engineering constraints.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide an automatic generation and calibration method for three-view drawings of automotive exterior based on engineering constraints. This method addresses the problems mentioned in the background art by employing a contour segmentation analysis method oriented towards multiple engineering constraints and a multi-view adaptive calibration mechanism based on directional stability.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for automatic generation and calibration of three-view drawings of automotive exterior based on engineering constraints, comprising the following steps:

[0008] Step S1: Obtain the exterior contour data of the vehicle exterior drawing to be tested and enter the contour view verification mechanism. In the contour view verification mechanism, the contour segment is defined based on the exterior contour data of the vehicle exterior drawing to be tested. The exterior constraint information of the vehicle exterior drawing to be tested is retrieved and the constraint type of the contour segment is marked.

[0009] Step S2: When performing view contour projection verification on the exterior drawing of the vehicle to be tested, obtain the projection boundary positioning results of the contour segments under each view contour projection, collect the projection position data of the contour segments in each marked constraint type, and calculate the constraint coverage coefficient.

[0010] Step S3: Evaluate the view change features and filter the target contour segments by combining the comprehensive constraint coverage coefficient and projection boundary positioning results. Detect the number of reversals of the contour calibration direction of the target contour segments and generate the direction stability index. Generate the contour conflict state based on the direction stability index.

[0011] Step S4: Select different contour calibration methods based on the contour conflict state to calibrate the target contour segment. After calibration, update the exterior contour data and analyze the contour convergence amplitude. Use the contour convergence amplitude to determine whether to re-enter the contour view verification mechanism or generate contour verification results.

[0012] In a preferred embodiment, in step S1, the exterior contour data of the vehicle exterior drawing to be tested is obtained through a three-dimensional exterior library. The exterior contour data is a set of contour point coordinates obtained after extracting the contour of the exterior component under a preset view direction.

[0013] After obtaining the exterior outline data, the outline view verification mechanism is entered, and the exterior outline is segmented in the outline view verification mechanism.

[0014] For any current contour point in the set of contour point coordinates, obtain the first contour line segment formed by the current contour point and the previous contour point, and the second contour line segment formed by the current contour point and the next contour point.

[0015] The angle between the first contour line segment and the second contour line segment is determined as the directional change of the current contour point.

[0016] In a preferred embodiment, in step S1, the exterior component contour corresponding to the exterior contour data is divided into multiple contour segments based on the directional change of the contour points.

[0017] The exterior constraint information of the vehicle exterior drawing under test is retrieved from the exterior constraint database, including the engineering constraint type of the vehicle exterior drawing under test and the contour action range corresponding to the engineering constraint type.

[0018] In a preferred embodiment, in step S1, the number of contour points in the contour segment that fall within the contour action range corresponding to the engineering constraint type is counted, and the ratio of this number to the total number of contour points in the contour segment is taken as the proportion of contour points of the engineering constraint type.

[0019] When the proportion of contour points of engineering constraint type is greater than the preset proportion threshold, the engineering constraint type is marked as the constraint type of contour segment.

[0020] Conversely, engineering constraint types are not used as constraint types for contour segments.

[0021] In a preferred embodiment, in step S2, the exterior drawing of the vehicle to be tested is projected under the outline projection of the front view, side view and top view respectively, and the projection boundary positioning results of the outline segment under the outline projection of each view are obtained.

[0022] The projection boundary positioning result includes the scalar value of the boundary position corresponding to the outermost projected boundary line of the contour segment under the view contour projection;

[0023] For each contour segment in the mark constraint type, collect the projection position data of each contour point in the contour segment under the contour projection of each view. The projection position data is the coordinate position of the contour point in the view plane after the view projection transformation.

[0024] The maximum and minimum projection position values ​​of the contour points corresponding to the contour segments in the statistical mark constraint type on the view contour projection;

[0025] The constraint coverage coefficient of the contour segment is calculated based on the maximum and minimum projection position values.

[0026] In a preferred embodiment, in step S3, for the constraint coverage coefficient of the contour segment under the projection of each view contour, the difference between the maximum and minimum values ​​of the constraint coverage coefficient is used as the engineering constraint range of the contour segment.

[0027] In the projection boundary positioning results corresponding to the contour segment, the difference between the maximum and minimum values ​​of the boundary position scalar value of the contour segment is taken as the boundary position offset of the contour segment.

[0028] The view change characteristics are obtained by calculating the combined engineering constraint range and boundary position offset range;

[0029] When the view change feature value of the outline segment is greater than the preset view change threshold, the outline segment will be selected as the target outline segment.

[0030] Conversely, contour segments are not considered as target contour segments.

[0031] In a preferred embodiment, in step S3, when the contour view verification mechanism is entered for the first time, after the target contour segment is selected, the contour conflict status of the target contour segment is recorded as conflict.

[0032] After completing the contour calibration process and re-entering the contour view verification mechanism, the contour conflict state is corrected based on the changes in the contour adjustment direction of the target contour segment in consecutive calibration rounds.

[0033] Extract the spatial coordinates of all contour points within the target contour segment in the current round and the previous round, and construct a set of calibration displacement vectors for the contour segment.

[0034] The calibration displacement vector set of each round is normalized, and the calibration direction vector of the target contour segment in the current calibration round is calculated from the normalized calibration displacement vector set.

[0035] The direction reversal event is obtained by calculating the inner product of the calibration direction vectors of two adjacent rounds.

[0036] In a preferred embodiment, in step S3, the number of times the target contour segment reverses direction during the entire calibration process is accumulated by statistically analyzing the direction reversal events in each consecutive calibration round;

[0037] The proportion of target contour segments that do not undergo directional reversal during the calibration process is used as the core metric. The directional stability index is obtained by normalizing the number of directional reversals with the total number of calibration rounds.

[0038] When the directional stability index is less than the preset directional stability threshold, the generated contour conflict state is determined to be conflict.

[0039] When the directional stability index is greater than or equal to the preset directional stability threshold, the generated contour conflict state is determined to be non-conflict.

[0040] In a preferred embodiment, in step S4, when the contour conflict state is conflict, a constraint-dominant calibration method is used for calibration processing. The constraint-dominant calibration method aims at constraint convergence and restrictively controls the contour adjustment direction and adjustment range of the target contour segment.

[0041] When the contour conflict state is non-conflict, the conventional smoothing calibration method is used for calibration. The conventional smoothing calibration method aims at continuous smoothness and performs conventional contour calibration on the target contour segment.

[0042] When performing contour calibration, the exterior contour data within the target contour segment is used as the calibration input data. The exterior contour data consists of the spatial coordinates of each contour point in the target contour segment in the current calibration round.

[0043] The exterior contour data is updated by calculating the calibration displacement of each contour point in the target contour segment and applying the calibration displacement to the corresponding contour point.

[0044] In a preferred embodiment, in step S4, after updating the exterior contour data, the contour convergence amplitude is obtained by statistically summarizing the spatial displacement of each contour point in the target contour segment between the current calibration round and the previous calibration round.

[0045] When the contour convergence amplitude is greater than the preset contour convergence threshold, it is determined to re-enter the contour view verification mechanism and execute the next round of contour verification process based on the updated exterior contour data.

[0046] When the contour convergence amplitude is less than or equal to the preset contour convergence threshold, the corresponding contour verification result is generated, and the contour view verification process for the target contour segment ends.

[0047] The technical effects and advantages of this invention are as follows:

[0048] This invention acquires exterior contour data and delineates contour segments, marks engineering constraint types at the contour segment level, calculates constraint coverage coefficients and view change characteristics under multi-view contour projection, filters target contour segments, generates a direction stability index and dynamically corrects contour conflict states by statistically analyzing contour adjustment direction changes in consecutive calibration rounds during the calibration iteration process, selects different contour calibration methods based on contour conflict states, updates exterior contour data after calibration processing and analyzes contour convergence amplitude, and uses contour convergence amplitude to determine whether to re-enter the contour view verification mechanism or generate contour verification results, thus achieving adaptive calibration and stable convergence of exterior contour data under multi-view conditions. Attached Figure Description

[0049] Figure 1 This is a flowchart illustrating the implementation of an automatic generation and calibration method for three-view drawings of automotive exterior based on engineering constraints, according to the present invention.

[0050] Figure 2 This is a schematic diagram illustrating the steps of an automatic generation and calibration method for three-view drawings of automotive exterior based on engineering constraints, according to the present invention. Detailed Implementation

[0051] 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.

[0052] This invention acquires exterior contour data and delineates contour segments, marks engineering constraint types at the contour segment level, calculates constraint coverage coefficients and view change characteristics under multi-view contour projection, filters target contour segments, generates a direction stability index and dynamically corrects contour conflict states by statistically analyzing contour adjustment direction changes in consecutive calibration rounds during the calibration iteration process, selects different contour calibration methods based on contour conflict states, updates exterior contour data after calibration processing and analyzes contour convergence amplitude, and uses contour convergence amplitude to determine whether to re-enter the contour view verification mechanism or generate contour verification results.

[0053] Example 1, such as Figures 1 to 2 As shown, a method for automatically generating and calibrating three-view drawings of automotive exterior trim based on engineering constraints includes the following steps:

[0054] Step S1: Obtain the exterior contour data of the vehicle exterior drawing to be tested and enter the contour view verification mechanism. In the contour view verification mechanism, the contour segment is defined based on the exterior contour data of the vehicle exterior drawing to be tested. The exterior constraint information of the vehicle exterior drawing to be tested is retrieved and the constraint type of the contour segment is marked.

[0055] Step S2: When performing view contour projection verification on the exterior drawing of the vehicle to be tested, obtain the projection boundary positioning results of the contour segments under each view contour projection, collect the projection position data of the contour segments in each marked constraint type, and calculate the constraint coverage coefficient.

[0056] Step S3: Evaluate the view change features and filter the target contour segments by combining the comprehensive constraint coverage coefficient and projection boundary positioning results. Detect the number of reversals of the contour calibration direction of the target contour segments and generate the direction stability index. Generate the contour conflict state based on the direction stability index.

[0057] Step S4: Select different contour calibration methods based on the contour conflict state to calibrate the target contour segment. After calibration, update the exterior contour data and analyze the contour convergence amplitude. Use the contour convergence amplitude to determine whether to re-enter the contour view verification mechanism or generate contour verification results.

[0058] The specific implementation is as follows:

[0059] In step S1, automotive exterior parts are subject to multiple engineering constraints during the design phase. The emphasis of constraints on the exterior contour varies in different views, making it difficult for the local contours of the same exterior part to remain consistent in different views. By segmenting the exterior contour and marking the effect of engineering constraints at the segment level, a data basis is provided for subsequent contour difference identification and calibration.

[0060] The exterior contour data of the vehicle exterior drawing to be tested is obtained by using a 3D exterior library. The exterior contour data refers to the set of contour point coordinates obtained after extracting the contour of the exterior component under a preset view direction.

[0061] Among them, the exterior view of the vehicle to be tested refers to the two-dimensional exterior view generated in a preset view direction for the exterior parts of the vehicle; the exterior parts refer to the body parts set on the outside of the vehicle body, used to form the vehicle's outline and participate in the assembly design, including bumpers, fenders, engine hoods and trunk lids; the preset view direction is the observation direction used to generate views and project outlines of the exterior parts, which can be set according to the installation posture of the exterior parts and engineering design specifications.

[0062] After obtaining the exterior outline data, the outline view verification mechanism is entered. The outline view verification mechanism is used to uniformly manage and iteratively update the outline of the exterior components during subsequent multi-view verification and calibration.

[0063] In the outline view verification mechanism, the external outline is segmented according to the changes in the outline direction between adjacent outline points;

[0064] Specifically, based on any current contour point in the set of contour point coordinates, the first contour line segment formed by the current contour point and the previous contour point and the second contour line segment formed by the current contour point and the next contour point are obtained respectively, and the angle between the first contour line segment and the second contour line segment is determined as the directional change of the current contour point.

[0065] When the directional change of adjacent contour points is less than the preset directional change threshold, the corresponding contour points are assigned to the same contour segment; when the directional change is greater than or equal to the preset directional change threshold, it serves as the starting point of a new contour segment, thereby dividing the exterior component contour corresponding to the exterior contour data into multiple contour segments.

[0066] The exterior constraint information of the vehicle exterior drawing under test is retrieved by the exterior constraint database. The exterior constraint information refers to the engineering constraint rules formed in the assembly design of the exterior components, including the engineering constraint type of the vehicle exterior drawing under test and the contour action range corresponding to the engineering constraint type.

[0067] Among them, engineering constraint type refers to the constraint category in the exterior constraint information according to the nature of the constraint action, and contour action range refers to the contour position range used to limit the engineering constraint type to take effect;

[0068] Based on the constraint types of each project, the contour segments are marked with constraint types;

[0069] For any contour segment, count the number of contour points in the contour segment that fall within the corresponding contour action range of the engineering constraint type, and use the ratio of this number to the total number of contour points in the contour segment as the proportion of contour points of the engineering constraint type.

[0070] When the proportion of contour points of engineering constraint type is greater than the preset proportion threshold, the corresponding engineering constraint type will be marked as the constraint type of contour segment.

[0071] Conversely, engineering constraint types are not used as constraint types for contour segments.

[0072] It should be noted that the 3D exterior library is a database used to store the set of contour points of automotive exterior parts; the preset direction change threshold can be set according to the sampling density of contour points of exterior parts or the requirements for contour continuity in engineering design; the exterior constraint database is a database used to store engineering constraint information related to exterior parts; the preset proportion threshold can be set according to the length of contour segments, the distribution of the number of contour points, or the requirements for constraint coverage in engineering design.

[0073] In step S2, the exterior design of the vehicle under test is checked by view contour projection. The exterior design of the vehicle under test is projected under the contour projection of the front view, side view and top view respectively, and the projection boundary positioning results of the contour segment under each view contour projection are obtained. The projection boundary positioning results refer to the boundary information of the contour segment reaching the extreme position in the projection direction, including the boundary position scalar value corresponding to the outermost projection boundary line of the contour segment under the view contour projection. The boundary position scalar value refers to the extreme coordinate of the outermost projection boundary line on the view coordinate axis in the corresponding view contour projection direction.

[0074] For each contour segment in the mark constraint type, collect the projection position data of each contour point in the contour segment under the contour projection of each view. The projection position data is the coordinate position of the contour point in the view plane after the view projection transformation.

[0075] Under the contour projection of each view, the maximum and minimum projection position values ​​of the contour points corresponding to the contour segments in the projection direction are statistically marked, and the difference between the two is used as the projection distribution span value of the engineering constraint type under the contour projection of that view.

[0076] After standardizing the projection distribution span value, the constraint coverage coefficient is obtained. The larger the constraint coverage coefficient, the more concentrated the distribution of the contour points under the corresponding engineering constraint type is in the projection direction of the view, and the stronger the control effect of the engineering constraint on the contour segment under the view.

[0077] For a contour segment, the maximum value of the constraint coverage coefficient of its marked engineering constraint type is taken as the constraint coverage coefficient of the contour segment.

[0078] It should be noted that the standardization methods include, but are not limited to, standard linear transformation based on interval scaling, statistical Z-Score standardization, or normalization based on nonlinear mapping functions. The application methods of standardization will not be elaborated here.

[0079] In step S3, for the constraint coverage coefficient of the contour segment under the projection of each view contour, the difference between the maximum and minimum values ​​of the constraint coverage coefficient is used as the engineering constraint range of the contour segment.

[0080] In the projection boundary positioning results corresponding to the contour segment, the difference between the maximum and minimum values ​​of the boundary position scalar value of the contour segment is taken as the boundary position offset of the contour segment.

[0081] The product of the standardized engineering constraint magnitude and the boundary position offset magnitude is used as the view change feature;

[0082] The view change feature value is compared with the preset view change threshold. When the view change feature value of the outline segment is greater than the preset view change threshold, the outline segment is selected as the target outline segment.

[0083] Conversely, contour segments are not considered as target contour segments.

[0084] The larger the view change feature value, the more likely the contour segment will have changes in engineering constraint emphasis and geometric boundary response under different views. The contour segment is more likely to generate engineering constraint conflicts during the multi-view generation process.

[0085] It should be explained that the preset view change threshold can be set based on the requirements for consistency of engineering constraints for exterior components during the multi-view generation process and the statistical results of historical design calibration.

[0086] When the contour view verification mechanism is first entered, after the target contour segment is selected, the contour conflict status of the target contour segment is recorded as a conflict, triggering subsequent contour calibration processing.

[0087] After completing the contour calibration process and re-entering the contour view verification mechanism, the direction reversal statistics and direction stability index calculation are performed based on the changes in the contour adjustment direction of the target contour segment in consecutive calibration rounds, and the contour conflict state is corrected again according to the direction stability index.

[0088] Using the continuous calibration rounds in the contour view verification mechanism as the time series benchmark, the contour changes of the target contour segment before and after two adjacent calibration rounds are aligned. Specifically, after calibration, the spatial coordinates of all contour points in the target contour segment in the current round and the previous round are extracted, and the calibration displacement vector set of the contour segment is constructed by matching the corresponding contour points one by one.

[0089] Subsequently, the calibration displacement vector set of each round is normalized, and the normalized calibration displacement vector set is summed and averaged to obtain the calibration direction vector representing the target contour segment in the current calibration round, in order to eliminate the influence of local point-level noise on direction judgment.

[0090] After obtaining the calibration direction vectors corresponding to consecutive calibration rounds, the angle between the calibration direction vectors of adjacent rounds is used as the basis for direction reversal detection. Specifically, by calculating the inner product of the calibration direction vectors of two adjacent rounds, when the inner product result is less than zero, it indicates that the contour calibration direction of the current round has reversed relative to the previous round; when the inner product result is greater than or equal to zero, it is determined that the contour calibration direction remains consistent or only the amplitude has changed without direction reversal.

[0091] By statistically analyzing the direction reversal events in each consecutive calibration round, the number of direction reversals of the target contour segment throughout the entire calibration process is accumulated, which is used to quantify the degree of directional sway of the contour segment under the constraints of multi-view engineering.

[0092] After counting the number of directional reversals, the directional stability index is calculated to characterize the overall stability of the profile calibration direction. The directional stability index uses the proportion of the target profile segment that did not experience directional reversal during the calibration process as the core metric. The number of directional reversals is normalized to the total number of calibration rounds, resulting in a directional stability index with dimensions between zero and one.

[0093] The closer the directional stability index is to one, the more consistent the adjustment direction of the contour segment remains during multiple calibration processes, and the clear direction of the engineering constraints. The closer the directional stability index is to zero, the more frequent the calibration direction reversal occurs in the contour segment under the alternating dominance of different view constraints, reflecting a significant risk of engineering constraint conflict in the contour segment.

[0094] Through the above implementation process, the objective detection of the reversal characteristics of the contour calibration direction of the target contour segment and the generation of the direction stability index are realized, providing a quantitative basis for subsequent contour conflict state determination and calibration strategy selection.

[0095] The directional stability index corresponding to the target contour segment is compared with the preset directional stability threshold:

[0096] When the directional stability index is less than the directional stability threshold, it indicates that the target contour segment has a high proportion of calibration direction reversal behavior in continuous calibration rounds, and exhibits obvious directional instability characteristics under the alternating dominance of different view engineering constraints. Based on this, the generated contour conflict state is determined to be conflict.

[0097] When the directional stability index is greater than or equal to the directional stability threshold, it indicates that the calibration direction of the target contour segment remains consistent or only changes in amplitude during multiple calibration processes, and the calibration behavior has good directional convergence. Based on this, the generated contour conflict state is determined to be non-conflict.

[0098] It should be noted that the directional stability threshold characterizes the upper limit of allowable calibration direction reversal behavior in a target contour segment during multiple rounds of automatic calibration, and serves as the criterion for distinguishing between contour conflict states and non-conflict states. Specifically, the calibration rounds in the contour view verification mechanism are used as the statistical interval, and the directional stability threshold is configured according to the maximum allowable direction reversal ratio in the automatic calibration process. That is, the directional stability threshold is set to one minus the maximum allowable reversal ratio. For example, when engineering allows a certain proportion of direction reversal rounds to occur at most during the entire calibration process, the corresponding directional stability threshold is set to a value higher than the complement of that proportion, thus ensuring that conflict determination is only triggered when direction reversal behavior is frequent and exceeds the engineering tolerance range.

[0099] In step S4, after determining the contour conflict state of the target contour segment, the contour calibration process based on the contour conflict state is initiated.

[0100] Based on the contour conflict state corresponding to the target contour segment, a contour calibration method matching the conflict state is selected from a pre-configured set of contour calibration methods. Specifically, when the contour conflict state is conflicting, a constraint-dominant calibration method is used. This method aims at constraint convergence and restricts the adjustment direction and magnitude of the target contour segment to suppress contour direction reversal caused by alternating dominance of engineering constraints in different views. When the contour conflict state is non-conflicting, a conventional smoothing calibration method is used. This method aims for continuous smoothness and performs conventional contour calibration on the target contour segment, gradually approximating the engineering constraint requirements while maintaining consistency in the current adjustment direction.

[0101] During contour calibration, the exterior contour data within the target contour segment is used as the calibration input data. The exterior contour data consists of the spatial coordinates of each contour point in the target contour segment in the current calibration round. The exterior contour data is updated by calculating the calibration displacement of each contour point in the target contour segment and applying the calibration displacement to the corresponding contour point.

[0102] The updated exterior profile data is used to replace the exterior profile data in the previous calibration round and serves as a unified data source for subsequent analysis and judgment.

[0103] After updating the exterior contour data, the contour convergence amplitude of the target contour segment is analyzed. The contour convergence amplitude is used to characterize the overall change of the target contour segment before and after two adjacent calibration cycles. Based on the spatial displacement of each contour point in the target contour segment between the current calibration cycle and the previous calibration cycle, the contour convergence amplitude is obtained by statistically summarizing the spatial displacement to reflect whether the contour adjustment tends to be stable.

[0104] The smaller the contour convergence magnitude, the weaker the contour change of the target contour segment in the current calibration round, and the more stable the contour shape gradually becomes; the larger the contour convergence magnitude, the more the contour is still in a significant adjustment phase.

[0105] The contour convergence magnitude is compared with the preset contour convergence threshold:

[0106] When the contour convergence amplitude is greater than the contour convergence threshold, it is determined that the target contour segment has not yet reached a stable state and multi-view contour verification and calibration processing needs to continue. At this time, the contour view verification mechanism is re-entered, and the next round of contour verification process is executed based on the updated exterior contour data.

[0107] When the contour convergence amplitude is less than or equal to the contour convergence threshold, it is determined that the target contour segment has reached the contour stability state, the corresponding contour verification result is generated, and the contour view verification process for the target contour segment ends.

[0108] It should be noted that the contour convergence threshold is used to characterize the maximum degree of contour change allowed when a target contour segment is determined to be morphologically stable during the automatic calibration iteration process. It serves as the criterion for terminating the contour view verification mechanism and outputting the contour verification result. Specifically, based on the calculation method of the contour convergence amplitude, the contour convergence threshold is set as a displacement tolerance value that matches the accuracy requirements of the exterior contour design. The displacement tolerance value can be derived from the minimum control scale of the allowable deviation of the contour in the exterior engineering design.

[0109] Through the above process, the target contour segment gradually converges under the constraint of contour conflict, thereby realizing the automatic calibration and result output of the exterior contour data.

[0110] Finally, it should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0111] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0112] In this document, the singular forms “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that terms such as “comprising / including” or “having” specify the presence of the stated features, integrals, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integrals, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0113] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0114] The above description of the disclosed embodiments will enable those skilled in the art to make or use various modifications to these embodiments. It will be readily apparent to those skilled in the art that the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for automatic generation and calibration of three-view drawings of automotive exterior trim based on engineering constraints, characterized in that: Includes the following steps: Step S1: Obtain the exterior contour data of the vehicle exterior drawing to be tested and enter the contour view verification mechanism. In the contour view verification mechanism, the contour segment is defined based on the exterior contour data of the vehicle exterior drawing to be tested. The exterior constraint information of the vehicle exterior drawing to be tested is retrieved and the constraint type of the contour segment is marked. Step S2: When performing view contour projection verification on the exterior drawing of the vehicle to be tested, obtain the projection boundary positioning results of the contour segments under each view contour projection, collect the projection position data of the contour segments in each marked constraint type, and calculate the constraint coverage coefficient. In step S2, the exterior drawing of the vehicle under test is projected under the outline projection of the front view, side view and top view respectively, and the projection boundary positioning results of the outline segment under the outline projection of each view are obtained. The projection boundary positioning result includes the scalar value of the boundary position corresponding to the outermost projected boundary line of the contour segment under the view contour projection; For each contour segment in the mark constraint type, collect the projection position data of each contour point in the contour segment under the contour projection of each view. The projection position data is the coordinate position of the contour point in the view plane after the view projection transformation. The maximum and minimum projection position values ​​of the contour points corresponding to the contour segments in the statistical mark constraint type on the view contour projection; The constraint coverage coefficient of the contour segment is calculated based on the maximum and minimum projection position values. Step S3: Evaluate the view change features and filter the target contour segments by combining the comprehensive constraint coverage coefficient and projection boundary positioning results. Detect the number of reversals of the contour calibration direction of the target contour segments and generate the direction stability index. Generate the contour conflict state based on the direction stability index. Step S4: Select different contour calibration methods based on the contour conflict state to calibrate the target contour segment. After calibration, update the exterior contour data and analyze the contour convergence amplitude. Use the contour convergence amplitude to determine whether to re-enter the contour view verification mechanism or generate contour verification results.

2. The method for automatic generation and calibration of three-view drawings of automotive exterior based on engineering constraints according to claim 1, characterized in that: In step S1, the exterior contour data of the vehicle exterior drawing to be tested is obtained through the three-dimensional exterior library. The exterior contour data is the set of contour point coordinates obtained after extracting the contour of the exterior parts under the preset view direction. After obtaining the exterior outline data, the outline view verification mechanism is entered, and the exterior outline is segmented in the outline view verification mechanism. For any current contour point in the set of contour point coordinates, obtain the first contour line segment formed by the current contour point and the previous contour point, and the second contour line segment formed by the current contour point and the next contour point. The angle between the first contour line segment and the second contour line segment is determined as the directional change of the current contour point.

3. The method for automatic generation and calibration of three-view drawings of automotive exterior based on engineering constraints according to claim 2, characterized in that: In step S1, the exterior component contour corresponding to the exterior contour data is divided into multiple contour segments based on the directional change of the contour points. The exterior constraint information of the vehicle exterior drawing under test is retrieved from the exterior constraint database, including the engineering constraint type of the vehicle exterior drawing under test and the contour action range corresponding to the engineering constraint type.

4. The method for automatic generation and calibration of three-view drawings of automotive exterior based on engineering constraints according to claim 3, characterized in that: In step S1, the number of contour points in the contour segment that fall within the contour action range corresponding to the engineering constraint type is counted, and the ratio of this number to the total number of contour points in the contour segment is taken as the proportion of contour points of the engineering constraint type. When the proportion of contour points of engineering constraint type is greater than the preset proportion threshold, the engineering constraint type is marked as the constraint type of contour segment. Conversely, engineering constraint types are not used as constraint types for contour segments.

5. The method for automatic generation and calibration of three-view drawings of automotive exterior based on engineering constraints according to claim 1, characterized in that: In step S3, for the constraint coverage coefficient of the contour segment under the projection of each view contour, the difference between the maximum and minimum values ​​of the constraint coverage coefficient is used as the engineering constraint range of the contour segment. In the projection boundary positioning results corresponding to the contour segment, the difference between the maximum and minimum values ​​of the boundary position scalar value of the contour segment is taken as the boundary position offset of the contour segment. The view change characteristics are obtained by calculating the combined engineering constraint range and boundary position offset range; When the view change feature value of the outline segment is greater than the preset view change threshold, the outline segment will be selected as the target outline segment. Conversely, contour segments are not considered as target contour segments.

6. The method for automatic generation and calibration of three-view drawings of automotive exterior based on engineering constraints according to claim 1, characterized in that: In step S3, when the contour view verification mechanism is entered for the first time, after the target contour segment is selected, the contour conflict status of the target contour segment is recorded as conflict. After completing the contour calibration process and re-entering the contour view verification mechanism, the contour conflict state is corrected based on the changes in the contour adjustment direction of the target contour segment in consecutive calibration rounds. Extract the spatial coordinates of all contour points within the target contour segment in the current round and the previous round, and construct a set of calibration displacement vectors for the contour segment. The calibration displacement vector set of each round is normalized, and the calibration direction vector of the target contour segment in the current calibration round is calculated from the normalized calibration displacement vector set. The direction reversal event is obtained by calculating the inner product of the calibration direction vectors of two adjacent rounds.

7. The method for automatic generation and calibration of three-view drawings of automotive exterior based on engineering constraints according to claim 6, characterized in that: In step S3, the number of times the target contour segment reverses direction during the entire calibration process is accumulated by statistically analyzing the direction reversal events in each consecutive calibration round. The proportion of target contour segments that do not undergo directional reversal during the calibration process is used as the core metric. The directional stability index is obtained by normalizing the number of directional reversals with the total number of calibration rounds. When the directional stability index is less than the preset directional stability threshold, the generated contour conflict state is determined to be conflict. When the directional stability index is greater than or equal to the preset directional stability threshold, the generated contour conflict state is determined to be non-conflict.

8. The method for automatic generation and calibration of three-view drawings of automotive exterior based on engineering constraints according to claim 7, characterized in that: In step S4, when the contour conflict state is conflict, the constraint-dominant calibration method is used for calibration processing. The constraint-dominant calibration method aims at constraint convergence and restrictively controls the contour adjustment direction and adjustment range of the target contour segment. When the contour conflict state is non-conflict, the conventional smoothing calibration method is used for calibration. The conventional smoothing calibration method aims at continuous smoothness and performs conventional contour calibration on the target contour segment. When performing contour calibration, the exterior contour data within the target contour segment is used as the calibration input data. The exterior contour data consists of the spatial coordinates of each contour point in the target contour segment in the current calibration round. The exterior contour data is updated by calculating the calibration displacement of each contour point in the target contour segment and applying the calibration displacement to the corresponding contour point.

9. The method for automatic generation and calibration of three-view drawings of automotive exterior based on engineering constraints according to claim 1, characterized in that: In step S4, after updating the exterior contour data, the contour convergence amplitude is obtained by statistically summarizing the spatial displacement of each contour point in the target contour segment between the current calibration round and the previous calibration round. When the contour convergence amplitude is greater than the preset contour convergence threshold, it is determined to re-enter the contour view verification mechanism and execute the next round of contour verification process based on the updated exterior contour data. When the contour convergence amplitude is less than or equal to the preset contour convergence threshold, the corresponding contour verification result is generated, and the contour view verification process for the target contour segment ends.

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