CN114218665A - Method and device for marking back datum line of engine hood - Google Patents

Abstract

The invention discloses a method and a device for scribing a datum line behind an engine hood, wherein the method comprises the following steps: intersecting the plurality of XZ planes with the engine hood model to obtain a plurality of engine hood intersecting lines; the XZ plane is parallel to a plane formed by the length of the whole vehicle corresponding to the engine cover model and the height direction of the whole vehicle; decomposing the engine hood intersecting lines aiming at each engine hood intersecting line to obtain a plurality of unit nodes; positioning the ball on the front windshield according to the diameter of a preset ball, the normal vector of the front windshield of the engine hood model and the intersection line of the engine hood to obtain the positioning coordinate of the ball; obtaining a target tangent point according to the plurality of unit nodes and the positioning coordinates; the target tangent point is the point with the minimum distance from the sphere center of the sphere in the plurality of unit nodes; and obtaining a back datum line of the engine hood according to the target tangent points of the multiple engine hood intersecting lines. The invention can realize automatic marking, and can obviously improve marking precision and marking efficiency.

Description

Method and device for marking back datum line of engine hood

Technical Field

The invention relates to the technical field of vehicle engineering, in particular to a method and a device for scribing a datum line behind an engine hood.

Background

Pedestrian protection is an important consideration in the field of automobile development and safety. In pedestrian collision simulation analysis, accurate division of collision regions is a key technology. The engine hood back datum line is an important component of a regulation definition datum line, and in the prior art, a marking method for the engine hood back datum line is implemented by introducing a whole vehicle model into corresponding mechanical design software and then manually marking according to corresponding standards and regulations, namely 'automobile-pedestrian collision protection' (GBT 245024502009). The marking mode needs manual work to determine the marking position according to the standard, and has low operation efficiency and high cost.

Disclosure of Invention

In view of the above problems, the invention provides a method and a device for scribing a datum line behind an engine hood, which can realize automatic scribing and can remarkably improve scribing precision and scribing efficiency.

In a first aspect, the present application provides the following technical solutions through an embodiment:

a method for scribing a datum line behind an engine hood comprises the following steps:

intersecting the plurality of XZ planes with the engine hood model to obtain a plurality of engine hood intersecting lines; the XZ plane is parallel to a plane formed by the length direction of the whole vehicle and the height direction of the whole vehicle corresponding to the engine hood model; for each engine hood intersection line, decomposing the engine hood intersection line to obtain a plurality of unit nodes; positioning a ball on a front windshield according to the diameter of a preset ball, the normal vector of the front windshield of the engine hood model and the engine hood intersection line to obtain the positioning coordinate of the ball; obtaining a target tangent point according to the unit nodes and the positioning coordinates; the target tangent point is a point with the smallest distance from the sphere center of the ball in the unit nodes; and obtaining the back datum line of the engine hood according to the target tangent points of the multiple engine hood intersecting lines.

Optionally, the ball has a diameter of 165 mm.

Optionally, the obtaining a target tangent point according to the plurality of unit nodes and the positioning coordinate includes:

and determining a point with the minimum distance from the center of the sphere from the unit nodes by adopting a beating method to obtain a target tangent point.

Optionally, the intersecting the plurality of XZ planes with the engine hood model to obtain a plurality of engine hood intersecting lines includes:

dividing the engine hood model along a target XZ plane passing through the width midpoint of the engine hood model to obtain a first sub-model and a second sub-model which are mutually mirrored; and intersecting the plurality of XZ planes with the first sub-model to obtain a plurality of engine hood intersecting lines.

Optionally, the obtaining the reference line behind the engine hood according to the target tangent points of the multiple engine hood intersecting lines includes:

mirroring the target tangent point according to the target XZ plane to obtain a mirror image tangent point on the second sub-model; and obtaining the back datum line of the engine hood according to the target tangent point and the mirror image tangent point.

In a second aspect, based on the same inventive concept, the present application provides the following technical solutions through an embodiment:

an engine hood back datum line marking device comprising:

the first decomposition module is used for intersecting the plurality of XZ planes with the engine hood model to obtain a plurality of engine hood intersecting lines; the XZ plane is parallel to a plane formed by the length direction of the whole vehicle and the height direction of the whole vehicle corresponding to the engine hood model; the second decomposition module is used for decomposing the engine hood intersecting lines to obtain a plurality of unit nodes; the positioning module is used for positioning the ball on the front windshield according to the preset diameter of the ball, the normal vector of the front windshield of the engine hood model and the intersection line of the engine hood to obtain the positioning coordinate of the ball; the tangent point acquisition module is used for acquiring a target tangent point according to the unit nodes and the positioning coordinates; the target tangent point is a point with the smallest distance from the sphere center of the ball in the unit nodes; and the scribing module is used for obtaining the back datum line of the engine hood according to the target tangent points of the multiple engine hood intersecting lines.

Optionally, the ball has a diameter of 165 mm.

Optionally, the tangent point obtaining module is specifically configured to:

and determining a point with the minimum distance from the center of the sphere from the unit nodes by adopting a beating method to obtain a target tangent point.

Optionally, the first decomposition module is specifically configured to:

dividing the engine hood model along a target XZ plane passing through the width midpoint of the engine hood model to obtain a first sub-model and a second sub-model which are mutually mirrored; and intersecting the plurality of XZ planes with the first sub-model to obtain a plurality of engine hood intersecting lines.

In a third aspect, based on the same inventive concept, the present application provides the following technical solutions through an embodiment:

an electronic device comprising a processor and a memory coupled to the processor, the memory storing instructions that, when executed by the processor, cause the electronic device to perform the steps of the method of any of the first aspects above.

The method and the device for scribing the rear datum line of the engine hood provided by the embodiment of the invention can automatically finish the whole scribing process of the rear datum line of the engine hood, and can be applied to scribing the rear datum line of the pedestrian protection engine hood of different vehicle types. By applying the method of the embodiment, the marking time of the back datum line of the engine hood can be greatly reduced, and the working efficiency is improved; the variable definition of related parameters during the decomposition of the XZ plane and the intersecting line of the engine hood is dynamically adjustable according to the actual condition and the precision requirement, so that the precision of marking a datum line behind the engine hood is adjustable, and high-efficiency and high-precision marking is ensured; variables such as the distance between the variables and the intersecting plane of the engine hood model and the like are defined through the variables of relevant parameters, so that the technology has strong adaptability and expansibility.

The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts. In the drawings:

FIG. 1 illustrates a schematic diagram of a hood back datum line definition in accordance with existing regulations;

FIG. 2 illustrates a flow chart of a method of marking a baseline behind a hood in an embodiment of the present invention;

FIG. 3 shows a schematic reference coordinate diagram of a hood model in an embodiment of the invention;

FIG. 4 is a schematic view showing the structure of a hood model in an embodiment of the present invention;

FIG. 5 illustrates a schematic diagram of a scribing method in an embodiment of the invention;

FIG. 6 is a schematic diagram showing the structure of a first sub-model and a second sub-model in an embodiment of the present invention;

FIG. 7 shows an enlarged schematic view of section A, B of FIG. 4;

fig. 8 is a schematic structural diagram showing functional modules of the hood back datum line marking device in the embodiment of the invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

The invention provides a method and a device for scribing a datum line behind an engine hood, which can carry out and realize the executed method steps or the realized functions based on a developed program. Specifically, the envelope curve of the pedestrian protection engine hood can be automatically divided based on a Tcl/Tk secondary development tool provided by Hypermesh finite element analysis software and through Tcl script development. The definition of the reference line behind the hood under the regulation "automobile pedestrian impact protection" (GBT 24502009) is the geometrical trajectory that the ball makes with the last contact point of the vehicle front structure when it, with a diameter of 165mm, rolls laterally on the vehicle front structure, keeping in contact with the front windscreen, as shown in fig. 1. During this process, the wiper blade and the oscillating arm should be removed. The concept of the invention is explained in detail below by means of a specific embodiment.

Referring to fig. 2, a flowchart of a method for marking a reference line behind an engine hood according to an embodiment of the present invention is shown, where the method includes:

step S10: intersecting the plurality of XZ planes with the engine hood model to obtain a plurality of engine hood intersecting lines; the XZ plane is parallel to a plane formed by the length direction of the whole vehicle and the height direction of the whole vehicle corresponding to the engine hood model;

step S20: for each engine hood intersection line, decomposing the engine hood intersection line to obtain a plurality of unit nodes;

step S30: positioning a ball on a front windshield according to the diameter of a preset ball, the normal vector of the front windshield of the engine hood model and the engine hood intersection line to obtain the positioning coordinate of the ball;

step S40: obtaining a target tangent point according to the unit nodes and the positioning coordinates; the target tangent point is a point with the smallest distance from the sphere center of the ball in the unit nodes;

step S50: and obtaining the back datum line of the engine hood according to the target tangent points of the multiple engine hood intersecting lines.

In the present embodiment, through steps S10-S50, a plurality of defined XZ planes are intersected with the engine hood model to obtain a plurality of engine hood intersection lines; then, decomposing the intersecting line of the engine cover to obtain a unit node; then, finding out the minimum distance between the unit node and the predefined positioning coordinate to determine target tangent points, wherein the target tangent points are all points on a datum line behind the engine hood; therefore, the hood back datum line can be obtained according to the target tangent points. The whole processing process can be automatically completed, a ball for reference does not need to be really used in the processing process, and only the coordinates of the ball need to be positioned; the method does not need manual participation in the scribing process of the datum line behind the engine hood, has high scribing treatment efficiency, obviously reduces the production cost and improves the production efficiency. Specific implementations of each step are set forth and described in detail below.

Step S10: intersecting the plurality of XZ planes with the engine hood model to obtain a plurality of engine hood intersecting lines; the XZ plane is parallel to a plane formed by the length direction of the whole vehicle corresponding to the engine hood model and the height direction of the whole vehicle.

In step S10, a coordinate system may be defined for convenience, as shown in fig. 3; the length direction of the whole vehicle corresponding to the engine hood model is an X axis of a coordinate system, the width direction of the whole vehicle corresponding to the engine hood model is a Y axis of the coordinate system, and the height direction of the whole vehicle corresponding to the engine hood model is a Z axis of the coordinate system; wherein the XZ plane is a plane parallel to the Y-reference plane, and the YZ plane is a plane parallel to the X-reference plane, as shown in fig. 3. Of course, in other implementations, other reference coordinate systems may be defined, and are not limited.

The engine cover model can be a CAD (Computer Aided Design) model, then is guided into Hypermesh finite element analysis software, and is subjected to geometric cleaning (cleaning redundant points, lines, surfaces, bodies and the like) to obtain a model; the engine cover model may include only component information of the engine cover of the vehicle and the front windshield portion of the vehicle, as shown in fig. 4, and does not include information such as mesh division, material, attribute, and the like, so as to improve processing efficiency.

Further, the plurality of XZ planes may be equally spaced planes or unequally spaced planes; in the embodiment, planes with equal spacing can be adopted, so that the calculation precision is ensured and the processing complexity is reduced; the size of the equidistant space is an adjustable variable, and during specific implementation, the size can be adjusted according to the precision requirement so as to improve the adaptability and the expandability. The smaller the distance setting, the higher the precision, but the calculation amount and the time consumed by calculation are multiplied; too large distance setting will result in that the marking accuracy can't be guaranteed. Therefore, in the present embodiment, the distance between two adjacent XZ planes can be set to be between 10mm and 50mm, for example, 10mm, 20mm, 50mm, etc. The number of the engine cover intersecting lines is equal to the engine cover width/two adjacent XZ plane intervals. If manual processing is adopted, the minimum distance is set to 100mm, and the workload is very huge for a simulation worker; however, for automatic division, only the distance variable needs to be changed, and the time consumption and cost are far less than those of manual operation.

After the plurality of XZ planes are intersected with the engine hood model, an intersection line formed on the upper surface of the engine hood model is an engine hood intersection line. When the plurality of XZ planes are equally spaced planes, the number of intersecting lines is the width of the intersecting hood model divided by the spacing between the plurality of XZ planes, and the number of intersecting lines of the hood can be changed by adjusting the spacing.

Step S20: and decomposing the engine hood intersection lines aiming at each engine hood intersection line to obtain a plurality of unit nodes.

In step S20, the following process may be performed for each of the hood intersections to determine a unit node: and carrying out unary linear meshing on the intersecting line of the engine cover to obtain a plurality of unit nodes, as shown in figure 4. When linear grid division is performed, the size of the grid unit can be a dynamically adjustable parameter, and can be set according to actual conditions and precision requirements, for example, in some implementations, the size can be set to 0.5mm, and the intersecting line of the engine can be dispersed into a plurality of unit nodes at equal intervals.

Step S30: positioning the ball on the front windshield according to the preset diameter of the ball, the normal vector of the front windshield of the engine hood model and the engine hood intersection line, and obtaining the positioning coordinate of the ball.

In step S30, the diameter of the ball may be determined to be 165mm, i.e. 82.5mm radius, according to the current corresponding legislative requirements. It is understood that, when the legal requirements change, the diameter of the ball in this embodiment may also be adjusted accordingly, without limitation.

After a normal vector on the front windshield is determined, a distance with the length of 82.5mm along the normal vector direction is taken as a possible position of a spherical center of the ball, and then the spherical center is limited on an XZ plane corresponding to an engine hood intersection line; thus positioning the ball on the front windshield, the position where the center of the ball may be located is the positioning coordinates of the ball, as shown in fig. 5. In this way, manual operation and the use of a physical sphere to roll on the engine cover model are avoided.

Step S40: obtaining a target tangent point according to the unit nodes and the positioning coordinates; the target tangent point is a point of the plurality of unit nodes having a smallest distance from the center of the sphere.

In step S40, since the coordinates of each unit node in the hood model are obtained, they may be represented as (x, y, z), and the coordinates of the location of the ball corresponding to the intersection of the hood may also be obtained, which may be represented as (x0, y0, z 0). Thus, the distance of a unit node from the center of sphere can be expressed as:

and then, determining a point with the minimum distance from the center of the sphere from the plurality of unit nodes by using a beating method, wherein the minimum point is also the target tangent point. If each of the split units is sufficiently small when the engine hood intersection is split, the minimum distance from the center of the sphere among the plurality of unit nodes is 82.5 mm. In addition, other algorithms can be adopted to find the node with the minimum distance from the center of the sphere, for example, the sphere is positioned at a position far away from the engine hood, the iteration step length is set, the sphere moves along the surface of the windshield along the X-axis negative direction according to the iteration step length, and when the intersection point or the tangent point is generated between the sphere and the engine hood model, the unit node between the two intersection points is used as the target tangent point; or taking the generated tangent point as a target tangent point; or taking the unit node closest to the two intersection points as the target tangent point. The target tangent point is a point on a datum line behind the engine hood.

Step S50: and obtaining the back datum line of the engine hood according to the target tangent points of the multiple engine hood intersecting lines.

In step S50, when the hood back datum line is obtained through the target tangent point, there may be at least two implementations:

one is that when the target tangent point is a point in the width direction of the whole engine hood model, the target tangent point can be connected or fitted to obtain the engine hood back datum line.

Secondly, when the target tangent point is a point in the width direction of the half hood model, that is, when step S10 is executed, the hood model is first divided along the target XZ plane passing through the width midpoint of the hood model, and a first sub-model and a second sub-model which are mirror images of each other are obtained, as shown in fig. 6, wherein one side is the first sub-model M1, and the other side is the second sub-model M2. Then, the plurality of XZ planes are intersected with the first sub-model to obtain a plurality of engine hood intersection lines. That is, the rear of the engine hood of a general vehicle is in a symmetrical structure about an XZ plane at the position of an over-width midpoint, so that only a part (1/2) of the engine hood model is required to be processed in the implementation means, and the consumption of computing resources can be greatly reduced.

Further, when step S50 is executed, the target tangent point may be mirrored according to the target XZ plane to obtain a mirrored tangent point on the second sub-model; obtaining a back datum line of the engine hood according to the target tangent point and the mirror image tangent point; for example, the target tangent point and the mirror image tangent point are connected or fitted in sequence, and then the engine hood back datum line can be obtained.

Referring to fig. 7 for a comparison, fig. 7 shows the difference between the manual scribing at A, B and the automatic scribing using the method of the present embodiment. From the enlarged schematic diagrams at A, B, it can be seen that when manual marking is adopted, the rear datum line of the engine hood is suspended at the turning point and separated from the model, and the marking accuracy is poor; and the automatic marking-out performed by the method of the embodiment can still keep the datum line behind the engine hood on the engine hood model at the turning part, and the precision is high.

In summary, according to the engine hood back datum line scribing method provided in this embodiment, a plurality of engine hood intersecting lines are obtained by intersecting a plurality of XZ planes with an engine hood model; the XZ plane is parallel to a plane formed by the length direction of the whole vehicle and the height direction of the whole vehicle corresponding to the engine cover model; then, decomposing the engine hood intersecting lines aiming at each engine hood intersecting line to obtain a plurality of unit nodes; secondly, positioning the ball on the front windshield according to the diameter of the preset ball, the normal vector of the front windshield of the engine hood model and the intersection line of the engine hood to obtain the positioning coordinate of the ball; then obtaining a target tangent point according to the plurality of unit nodes and the positioning coordinates; the target tangent point is the point with the minimum distance from the sphere center of the sphere in the plurality of unit nodes; and finally, obtaining a back datum line of the engine hood according to the target tangent points of the multiple engine hood intersecting lines. The whole scribing process of the method can be automatically completed, and the method can be applied to scribing the rear datum line of the pedestrian protection engine hood of different vehicle types. By applying the method of the embodiment, the marking time of the back datum line of the engine hood can be greatly reduced, and the working efficiency is improved; through variable definition of related parameters, the marking accuracy of the datum line behind the engine hood is adjustable dynamically according to actual conditions and accuracy requirements; variables such as the distance between the variables and the intersecting plane of the engine hood model and the like are defined through the variables of relevant parameters, so that the technology has strong adaptability and expansibility.

Referring to fig. 8, based on the same inventive concept, in another embodiment of the present invention, there is provided a hood back datum line marking device 300, wherein the hood back datum line marking device 300 includes:

the first decomposition module 301 is used for intersecting the plurality of XZ planes with the engine hood model to obtain a plurality of engine hood intersecting lines; the XZ plane is parallel to a plane formed by the length direction of the whole vehicle and the height direction of the whole vehicle corresponding to the engine hood model; a second decomposition module 302, configured to decompose each of the engine hood intersection lines to obtain a plurality of unit nodes; the positioning module 303 is configured to position the ball on the front windshield according to a preset diameter of the ball, a normal vector of a front windshield of the engine hood model, and the engine hood intersection line, so as to obtain a positioning coordinate of the ball; a tangent point obtaining module 304, configured to obtain a target tangent point according to the plurality of unit nodes and the positioning coordinate; the target tangent point is a point with the smallest distance from the sphere center of the ball in the unit nodes; the scribing module 305 is configured to obtain the hood back datum line according to the target tangent points of the multiple hood intersection lines.

As an alternative embodiment, the ball has a diameter of 165 mm.

As an optional implementation manner, the tangent point obtaining module 304 is specifically configured to:

and determining a point with the minimum distance from the center of the sphere from the unit nodes by adopting a beating method to obtain a target tangent point.

As an optional implementation manner, the first decomposition module 301 is specifically configured to:

dividing the engine hood model along a target XZ plane passing through the width midpoint of the engine hood model to obtain a first sub-model and a second sub-model which are mutually mirrored; and intersecting the plurality of XZ planes with the first sub-model to obtain a plurality of engine hood intersecting lines.

As an optional implementation manner, the scribing module 305 is specifically configured to:

mirroring the target tangent point according to the target XZ plane to obtain a mirror image tangent point on the second sub-model; and obtaining the back datum line of the engine hood according to the target tangent point and the mirror image tangent point.

It should be noted that the specific implementation and technical effects of the hood back datum line marking device 300 provided by the embodiment of the present invention are the same as those of the foregoing method embodiment, and for the sake of brief description, reference may be made to corresponding contents in the foregoing method embodiment to the extent that no part of the embodiment of the device is mentioned.

Based on the same inventive concept, in yet another embodiment of the present invention, there is also provided an electronic device comprising a processor and a memory coupled to the processor, the memory storing instructions that, when executed by the processor, cause the electronic device to perform the steps of the method of any of the preceding embodiments.

It should be noted that, in the electronic device provided in the embodiment of the present invention, when the instructions are executed by the processor, the specific implementation of each step and the generated technical effect are the same as those of the foregoing method embodiment, and for the sake of brief description, for the sake of brevity, reference may be made to the corresponding contents in the foregoing method embodiment for the non-mentioned part of the present embodiment.

The term "and/or" appearing herein is merely one type of associative relationship that describes an associated object, meaning that three relationships may exist, e.g., a and/or B, may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship; the word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words may be interpreted as names.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (10)

1. A method for marking a datum line behind an engine hood is characterized by comprising the following steps:

intersecting the plurality of XZ planes with the engine hood model to obtain a plurality of engine hood intersecting lines; the XZ plane is parallel to a plane formed by the length direction of the whole vehicle and the height direction of the whole vehicle corresponding to the engine hood model;

for each engine hood intersection line, decomposing the engine hood intersection line to obtain a plurality of unit nodes;

positioning a ball on a front windshield according to the diameter of a preset ball, the normal vector of the front windshield of the engine hood model and the engine hood intersection line to obtain the positioning coordinate of the ball;

obtaining a target tangent point according to the unit nodes and the positioning coordinates; the target tangent point is a point with the smallest distance from the sphere center of the ball in the unit nodes;

and obtaining the back datum line of the engine hood according to the target tangent points of the multiple engine hood intersecting lines.

2. The method of claim 1, wherein the ball has a diameter of 165 mm.

3. The method of claim 1, wherein obtaining a target tangent point from the plurality of unit nodes and the location coordinates comprises:

and determining a point with the minimum distance from the center of the sphere from the unit nodes by adopting a beating method to obtain a target tangent point.

4. The method of claim 1, wherein said intersecting a plurality of XZ planes with a hood model to obtain a plurality of hood intersections comprises:

dividing the engine hood model along a target XZ plane passing through the width midpoint of the engine hood model to obtain a first sub-model and a second sub-model which are mutually mirrored;

and intersecting the plurality of XZ planes with the first sub-model to obtain a plurality of engine hood intersecting lines.

5. The method of claim 4, wherein said obtaining the hood rearward datum line based on the target tangent points of the plurality of hood intersections comprises:

mirroring the target tangent point according to the target XZ plane to obtain a mirror image tangent point on the second sub-model;

and obtaining the back datum line of the engine hood according to the target tangent point and the mirror image tangent point.

6. An engine hood back datum line marking device, characterized by comprising:

the first decomposition module is used for intersecting the plurality of XZ planes with the engine hood model to obtain a plurality of engine hood intersecting lines; the XZ plane is parallel to a plane formed by the length direction of the whole vehicle and the height direction of the whole vehicle corresponding to the engine hood model;

the second decomposition module is used for decomposing the engine hood intersecting lines to obtain a plurality of unit nodes;

the positioning module is used for positioning the ball on the front windshield according to the preset diameter of the ball, the normal vector of the front windshield of the engine hood model and the intersection line of the engine hood to obtain the positioning coordinate of the ball;

the tangent point acquisition module is used for acquiring a target tangent point according to the unit nodes and the positioning coordinates; the target tangent point is a point with the smallest distance from the sphere center of the ball in the unit nodes;

and the scribing module is used for obtaining the back datum line of the engine hood according to the target tangent points of the multiple engine hood intersecting lines.

7. The device of claim 6, wherein the ball has a diameter of 165 mm.

8. The apparatus of claim 6, wherein the tangent point obtaining module is specifically configured to:

and determining a point with the minimum distance from the center of the sphere from the unit nodes by adopting a beating method to obtain a target tangent point.

9. The apparatus of claim 6, wherein the first decomposition module is specifically configured to:

dividing the engine hood model along a target XZ plane passing through the width midpoint of the engine hood model to obtain a first sub-model and a second sub-model which are mutually mirrored;

and intersecting the plurality of XZ planes with the first sub-model to obtain a plurality of engine hood intersecting lines.

10. An electronic device comprising a processor and a memory coupled to the processor, the memory storing instructions that, when executed by the processor, cause the electronic device to perform the steps of the method of any of claims 1-5.

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