JP2003196326A - Device and method for creating shape model - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate creation of an adjusted CAD model of a prototype. <P>SOLUTION: A case that the shape of the prototype is deviated from a reference CAD model 32 as a result of adjusting the prototype created on the basis of the reference CAD model 32 whenever it is necessary by a worker is considered. The prototype is scanned with a scanner 10 and a CAD model is generated from a group of tomograms obtained as scanning results. An actually measured CAD model obtained by the scanning results does not always express the shape of the prototype completely exactly due to a partial image defect, etc., in a CT tomogram. Thus, an actual CAD model which is more faithful to the shape of the prototype can be created by positioning the actually measured CAD model with the reference CAD model 32 by using a positioning processing part 22 and compensating a defect part of the actually measured CAD model by the shape information of a corresponding part of the reference CAD model 32 by using a model correction processing part 24. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for creating a shape model data corresponding to a manufactured product when the designed product is actually manufactured.

[0002]

2. Description of the Related Art Generally, in product development, a prototype is manufactured based on a design, various tests are performed on the prototype, and the cycle of feeding back the test results to the design is repeated to obtain desired mechanical characteristics. A product design that can secure

In recent years, the design is generally performed using a CAD (Computer Aided Design) system, and the CAD design result can be numerically analyzed on a CAE (Computer Aided Engineering) system. Well done.

In the CAD system, since it is necessary to accurately represent the product shape, NURBS (Non Uniform Rati)
Onal B-Spline) is often used as a data format that can accurately represent high-level free-form surfaces. On the other hand, CAE
In the system, a data format in which a product shape is represented by a polygonal mesh is generally used, such as a FEM (finite element method) mesh model. There is also a system having a mutual data format conversion function for cooperation between CAD and CAE.

Further, when a defective portion is found in the CAE analysis, the CAE model is repeatedly corrected and analyzed to obtain a CAE model having desired characteristics, and this CAE model is often reflected in the CAD model. It is being appreciated. For example, Japanese Patent Laid-Open No. 2001-147950 discloses a system for automatically converting a corrected CAE model into a CAD data format.

[0006]

Thus, although CAE has made it possible to analyze a considerable part of product characteristics without making a prototype, it is difficult to examine all the characteristics by CAE analysis. For these reasons, testing and evaluation using prototypes still have important meanings.

However, the prototype generally has a shape that is separated from the original CAD model while the defective portion is being modified according to the test result.
There are often no CAD models that accurately represent the shape of the prototype. In addition, when a product is created from a CAD model created by the design department, the manufacturing department often makes design changes in consideration of requirements such as manufacturing procedures and costs. The prototype produced has a different shape from the original CAD model.

For this reason, for example, if the prototype is passed the test / evaluation, the product is produced using the paper drawing created by the manufacturing department as the official drawing, and the CAD model and the actual product shape are different. come. C depending on the shape change of the prototype
If you make manual changes to the AD model, CAD
Although it is possible to maintain the agreement between the model and the product shape, it is difficult and very time-consuming to accurately reflect the shape change in the CAD model by manual operation. In addition, CAE analysis is often effective for investigating the cause of defects in prototypes and countermeasures, but as described above, there are often no models that accurately correspond to the prototypes. It took a lot of time to fix the original CAD model according to the prototype.

The present invention has been made in view of the above problems, and represents the shape of an object such as a prototype produced based on a shape model such as CAD after the shape is changed by rework or the like. An object is to provide a device that can easily create a model.

[0010]

In order to achieve the above object, an apparatus according to the present invention stores a reference shape model of a predetermined data format representing a reference shape of an object, or data capable of deriving the reference shape model. A storage means; a measured shape model generation means for obtaining three-dimensional shape information of an object manufactured corresponding to the reference shape model, and converting the shape information into the predetermined data format to create a measured shape model; Complementing means for creating an actual shape model of the predetermined data format representing the shape of the manufactured object by complementing the measured shape model with the reference shape model.

Further, in a preferred aspect of the present invention, the complementing means detects a plurality of predetermined characteristic shapes included in the object from the reference shape model and the actually measured shape model, respectively, and detects the plurality of characteristic shapes in each of the shape models. A means for aligning the shape models with each other based on the positional relationship of the characteristic shapes is provided, and the alignment is performed by the means, and then the complement is performed.

Further, in a preferred aspect of the present invention, the actually measured shape model creating means captures a tomographic image for each of a plurality of different heights of the manufactured object, and the three-dimensional shape of the object is obtained from the tomographic image group. Ask for information.

Further, the shape model generation method according to the present invention comprises a step of preparing a reference shape model of a predetermined data format representing a reference shape of an object, or a data capable of deriving the reference shape model of the predetermined data format; Obtaining three-dimensional shape information of an object manufactured based on the shape model, converting the shape meter information into the predetermined data format to create an actually measured shape model, and complementing the actually measured shape model with the reference shape model. Thereby creating a physical shape model of the predetermined data format that represents the shape of the manufactured object.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

In this embodiment, three-dimensional shape information of a prototype is acquired by X-ray CT (Computer Tomography),
A 3D CAD model of the prototype is generated from this information. However, in a tomographic image obtained by CT, image information may be partially missing depending on the X-ray transmission state (for example, there is a structure but it does not appear in the tomographic image). The three-dimensional CAD model (hereinafter referred to as “measured CAD model”) created from the above has a shape different from that of the prototype in the missing portion and the like. Therefore, in the present embodiment, the measured CAD model is supplemented with the shape information of the three-dimensional CAD model (referred to as “reference CAD model”) that is used as a reference when creating the prototype, so that the shape of the prototype is more faithful. A new CAD model. Less than,
A system and a processing procedure therefor will be described with reference to the drawings.

FIG. 1 is a diagram showing an overall image of a product model management system according to the present invention. In the figure, a CT scanner 10 is a device for capturing a CT tomographic image of a prototype. The CT scan data conversion unit 12 uses the CT scanner 1
It is a processing device that converts the tomographic image group obtained at 0 into a data format that can be accepted by the CAD / CAE system 20. As this data format, the STL (STereo Lithography) format, which has been developed as a shape data format for stereolithography systems and is currently supported by many CAD systems, can be used. In the STL format, the surface shape of an object is represented by a set of triangular minute patches. As a method of generating STL data from the CT tomographic image group, a conventionally known method may be used.

The storage device 30 has a base 3 for the prototype.
It is assumed that the reference CAD model 32, which is a dimensional CAD model, is prepared in advance. Standard CAD model 32
Is a design model that is typically created at the product design stage and used as a reference for the first prototype in the manufacturing department. Further, a CAD model of a prototype created by using this system can be used as the reference CAD model 32 at the stage of repeating trial production. Reference CA in this case
The D model 32 can be used as a reference model for generating a faithful CAD model of a new prototype shape made by modifying (shape correction) the prototype.

The CAD / CAE system 20 is a system that provides a CAD function and a CAE function. This system 20 has a CAD model creation / modification function and an analysis function such as a finite element method analysis, and also creates a CAE model used for CAE analysis processing from the CAD model,
On the contrary, it has a function of creating a CAD model from the CAE model. These model creating functions are conventionally known, and the conventional method can be used in this system. In addition, the CAD / CAE system 20 is C
It has a function of converting the STL data input from the T-scan data conversion unit 12 into a CAD model. In the present embodiment, the CAD model data format is the NURBS format, which has a high curved surface expression capability, but other data formats can also be used. The CAD model converted from the STL data by this function is the actually measured CAD model.

Further, the CAD / CAE system 20 of this embodiment has a registration processing unit 22 and a model correction processing unit 2.
4 is provided.

The alignment processing unit 22 is means for aligning the actually measured CAD model with the reference CAD model 32 stored in the storage device 30. The reason why the actual measurement CAD model and the reference CAD model 32 need to be aligned is as follows. That is, actually measured CAD
The model is the shape measured by the CT scanner 10 (tomographic image group)
Since it is created from, the reference coordinate system of the model is
In general, the reference CAD model 32 is deviated from the coordinate system. When the coordinate systems are displaced in this way, it becomes difficult to associate the same parts in both models.
Therefore, in the present embodiment, the alignment processing unit 22 performs a process of matching the coordinate systems of both models. The contents of this processing will be described later in detail.

The model correction processing unit 24 is means for complementing the actually measured CAD model with the information of the reference CAD model 32 to create a CAD model more faithful to the shape of the prototype. The CAD model generated by the model correction processing unit 24 is called a real CAD model. The model correction processing unit 24 uses the actual CAD model aligned by the alignment processing unit 22 and the reference CAD model 32 for CAD /
It is displayed side by side on the display screen attached to the CAE system 20 so that the user can compare the two. Further, the model correction processing unit 24 has a function of a shape operation included in a general three-dimensional CAD system and a function of receiving an instruction for the shape operation, and actually measures a NURBS surface selected by a user from a reference CAD model. It has a function of replacing or mapping on a part designated by the user on the CAD model. According to this function, the specified part of the actually measured CAD model is replaced with the same shape as the surface selected on the reference CAD model, or the selected surface shape is smoothly joined to the shape around the specified part of the actually measured CAD model. The shape in the vicinity of the designated portion can be converted. The operations used in the existing three-dimensional CAD can be used for the operations of the surface replacement and mapping.

As a user interface for this function, for example, the selection of a surface from the user is accepted on the display screen of the reference CAD model, and the part to which the surface is applied is specified by the user on the display screen of the actually measured CAD model. A mechanism such as acceptance is suitable.

According to this function, the defective portion on the actually measured CAD model due to the missing portion of the CT image or the like is identified as the reference CA.
The shape data of the D model 32 can be supplemented by using the shape data, and an actual CAD model can be generated that is more faithful to the shape of the prototype.

In addition, the model correction processing unit 24 is arranged to perform the adjustment between the registered actual measurement CAD model and the reference CAD model.
It is also preferable to have a function of calculating the positional deviation of each part of the surface, finding the portion with a large positional deviation by comparison with a threshold value, and presenting it to the user. As a result, it is possible to reduce the burden on the user of finding a defective portion due to a CT image missing portion or the like.

It is also conceivable that a slight unevenness or the like, which is not found in the prototype, may be formed on the surface of the actually measured CAD model due to small unevenness in the CT image. In such cases,
For example, the surface of the reference CAD model is mapped to the measurement CAD model with respect to the portion where the positional deviation of the surface between the measurement CAD model and the reference CAD model is minute (for example, it can be obtained by comparison with a threshold value). By providing the model correction processing unit 24 with a function, such irregularities can be removed.

Next, with reference to FIG. 2, a process of generating a real CAD model in this system will be described. FIG. 2 is a flow chart showing the procedure for creating a CAD model in accordance with the shape of the prototype with this system.

First, the prototype is scanned by the CT scanner 10 to capture CT tomographic images for each predetermined height level (S10). Next, the CT scan data conversion unit 12
From the tomographic image group showing the three-dimensional shape of the prototype, STL
Format 3D shape data is created (S12). CAD
The / CAE system 20 receives the STL format data and converts the data into the NURBS format, which is the basic format of the system 20 (S14). As a result, an actually-measured CAD model having the same data format as the reference CAD model 32 which is the basis of the prototype is obtained.

Next, the alignment processing unit 22 causes the actually measured CAD
The model and the reference CAD model 32 are aligned (S
16). This alignment is executed as follows, for example. That is, first of all, the alignment processing unit 22 sets the measured CAD model and the reference CAD model 32 to
The characteristic shape included in the product (prototype) is detected. For example, in the case of a cylinder head of an internal combustion engine, since many circular holes such as bolt holes and water holes exist, a circular shape is adopted as a characteristic shape, and the circular portion is detected on the surface of each model. When the characteristic shape portions are detected from the respective models, the coordinates of the reference points of the respective characteristic shape portions are then obtained on the coordinate system of the respective CAD models. For example, when the characteristic shape is a circle, the center of the circle may be used as the reference point. Then, the coordinate system of the actually measured CAD model is set so that the corresponding reference points have the same position coordinates (they need not be completely the same as long as they are within a predetermined allowable range) between the two CAD models. Align with the coordinate system of the reference CAD model. Characteristic part (reference point) between both CAD models
The CAD can be associated with each other automatically based on the relationship between the characteristic part and the peripheral shape, but both CAD models are displayed on the screen and the user is asked to specify the corresponding characteristic parts on the screen. You may do it. Not collinear 3
If the coordinates of the reference points of one or more characteristic portions are known on both CAD models, both CAD models can be aligned.

In this way, the actually measured CAD model and the reference C
When the alignment with the AD model is completed, the model correction processing unit 24 complements the measured CAD model with the reference CAD model as described above, and the actual CAD model 36 representing the actual shape of the prototype is generated. (S18).

As described above, according to the present embodiment, the three-dimensional shape of the prototype actually measured by the CT scanner 10 is complemented by using the reference CAD model which is the base of the prototype, so that the prototype A CAD model faithful to the shape can be easily created.

Even if the reference CAD model that is the basis of the prototype does not exist, if a shape model such as a CAE model exists, the shape model is converted into a CAD model and this is used as the reference CAD model. It is also possible.

Next, an example of a prototype improvement process using this system will be described with reference to FIG.

It is assumed that a defective part is found by making a prototype, testing and evaluating it (S20). In this case, the user determines whether there is a CAD model that faithfully represents the shape of the prototype (S22). Such C
If an AD model exists, the CAD / CAE system 20 generates a CAE model for a predetermined analysis such as the finite element method from the CAD model (S30), and CA
E Perform analysis processing to investigate the cause of failure and
CAE analysis is performed by appropriately modifying the E model, and work such as finding a CAE model shape that can solve the problem is performed (S32). In this way, if a CAE model that is thought to be able to solve the problem is created, it will be NUR
The CAD model is converted into a BS format or the like (S34). Then, if a further trial test is required, a new prototype is created or the prototype evaluated in S20 is modified according to the CAD model (S36), and the test / evaluation is performed again (S20). When the user determines that there is no problem only by the CAE verification, the CAD model obtained in S34 may be recorded as a model representing the final product shape and the production process may be started.

On the other hand, when it is determined in S22 that the faithful CAD model of the prototype does not exist, a tomographic image group of the prototype is photographed by CT scan processing to generate STL data (S24), and the STL data is NURBS. C such as format
Convert to AD model (actual CAD model) (S26),
The model correction processing unit 24 complements the measured CAD model with the shape information of the reference CAD model 32 that is the base of the prototype, and generates a real CAD model faithful to the shape of the prototype (S28). When an actual CAD model representing a prototype is created, CAE analysis is performed to obtain a shape capable of eliminating a defect, as in the case where such a model exists from the beginning (S30 to S34). In addition, S
When the CAE model is modified in 32, the operator can also modify the prototype based on the CAE model without conversion to the CAD model, and the modification results can be tested. -It is also possible to perform evaluation and generate a real CAD model from the result of rework.

When it is confirmed that there is no defect in the test / evaluation of the prototype or the CAE analysis (or both) by repeating the above cycle, the actual product C representing the prototype at that time is shown.
C generated from the AD model or the CAE model at that time
The AD model can be used as a three-dimensional CAD model that represents the final product shape.

As described above, in this embodiment, since a CAD model faithful to the actual shape of the prototype can be easily created, CAE analysis can be executed quickly. Further, a CAD model of the final product shape that has passed the test or the like can be easily created in the same manner, and it becomes easy to store an accurate CAD model representing the shape of the manufactured product.

Although a CAD model in NURBS format or the like is generated as a model representing the actual shape of the prototype in the above, the method of this embodiment can be used to create a shape model of any basic format. it can.

In the above, the X-ray CT is used to measure the three-dimensional shape of the prototype, but the present invention is not limited to this, and various three-dimensional shape measuring methods can be used. However,
The type of three-dimensional shape measuring method that can be used is limited depending on the shape of the target product. That is, in the case of a product having an internal structure that cannot be seen through, such as a cylinder block, a method of obtaining a tomographic image such as CT is suitable, while in the case of a shape having no internal structure, a stereo image is obtained. The three-dimensional shape can be measured by using an image method or a laser range finder.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of an embodiment.

FIG. 2 is a flowchart showing a procedure of basic processing in this system.

FIG. 3 is a flow chart showing an example of a process for improving a prototype using this system.

[Explanation of symbols]

10 CT scanner, 12 CT scan data conversion unit, 20 CAD / CAE system, 22 alignment processing unit, 24 model correction processing unit, 30 storage device, 3
2 Standard CAD model, 34 CAE model.

Claims (4)

[Claims] 1. A storage means for storing a reference shape model of a predetermined data format representing a reference shape of an object, or data capable of deriving the reference shape model, and an object manufactured corresponding to the reference shape model. The three-dimensional shape information is obtained, and the measured shape model is created by converting the shape information into the predetermined data format to create a measured shape model, and complementing the measured shape model with the reference shape model. A shape model creating apparatus comprising: a complementing unit that creates an actual shape model of the predetermined data format that represents the shape of an object. 2. The shape model creating device according to claim 1, wherein the complementing unit detects a plurality of predetermined characteristic shapes included in the object from the reference shape model and the actually measured shape model, and detects each of them. Forming a shape model characterized by comprising means for aligning the shape models with each other based on the positional relationship of the plurality of characteristic shapes in the shape model, and performing the complement after the alignment by the means. apparatus. 3. The shape model creating apparatus according to claim 1, wherein the actually measured shape model creating means captures tomographic images for each of a plurality of different heights of the manufactured object, and selects the tomographic images from the tomographic image group. A shape model creating apparatus characterized by obtaining three-dimensional shape information of the object. 4. A step of preparing a reference shape model of a predetermined data format representing a reference shape of an object, or data capable of deriving a reference shape model of the predetermined data format, and an object manufactured based on the reference shape model. Obtaining three-dimensional shape information and converting the shape meter information into the predetermined data format to create an actually measured shape model; and complementing the actually measured shape model with the reference shape model, A shape model creating method comprising: creating an actual shape model of the predetermined data format representing a shape.