KR20160136086A

KR20160136086A - Reverse engineering method using photo for aircraft

Info

Publication number: KR20160136086A
Application number: KR1020150069802A
Authority: KR
Inventors: 김재원
Original assignee: 한국항공우주산업 주식회사
Priority date: 2015-05-19
Filing date: 2015-05-19
Publication date: 2016-11-29

Abstract

The present invention relates to an aircraft shape reverse engineering method using photographs. The purpose of the present invention is to provide the aircraft shape reverse engineering method using a photograph, which can realize an aircraft shape through a two-dimensional indirect measuring method using photographs for designing the aircraft shape whose real object exists, but is not obtained. In addition, another purpose of the present invention is to provide the aircraft shape reverse engineering method using photographs, which can obtain two-dimensional photographs that are the most useful to be used for three-dimensional shape reverse engineering so as to maximally prevent inaccuracy of a finally obtained three-dimensional shape due to distortion of information inherent in photographs itself in the two-dimensional indirect measuring method. In order to achieve these purposes, the aircraft shape reverse engineering method using photographs, comprises: a step of obtaining a plurality of photographs; a step of scaling; a step of obtaining information; and a step of calculating a shape.

Description

[0001] The present invention relates to a reverse engineering method using photo,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of reverse designing an aircraft shape using photographs. More specifically, in designing the shape of an aircraft covering various types of aircraft such as an airplane, a glider, a helicopter, an airship, and the like, And a method for inverse shape design of an aircraft.

Aircraft refers to a variety of vehicles such as airplanes, gliders, helicopters, airships, etc., and is widely used in the air as a reaction to the air other than the reaction of the air to the machine, or more precisely to the surface, It includes all machines capable of obtaining bearing capacity. In other words, it is very important to design the shape of the aircraft so that launching of the aircraft into the atmosphere is realized by the force generated by the flow of air surrounding the aircraft, so that the airflow around the aircraft is formed as desired.

When designing the shape of an aircraft, the optimum shape is designed in accordance with various conditions such as the weight or volume of the aircraft, the flight altitude, and the speed required in consideration of aerodynamics, as described above. Generally, the simulation is performed by using a three-dimensionally modeled virtual model to obtain a measurement value by performing an experiment on a wind tunnel by producing an actual model for various shapes formed by changing shape design parameters Obtain an estimate and analyze these data to determine the optimal shape.

However, the principles used for such shape design are also very difficult, and the environmental conditions and design variables to be considered are also very complex and diverse, and it is important to understand how to control the design variables to obtain the optimal shape It is a fact that this design process itself is a very difficult task. Therefore, such a shape design requires a lot of time, cost, and manpower.

On the other hand, reverse engineering techniques collectively refer to engineering techniques for estimating data that are difficult or impossible to obtain realistically and for using for specific purposes. The origins of reverse engineering originate from commercial or military hardware analysis, inferring the design process with the final product with little knowledge of the original production process. Currently, the concept of reverse engineering also includes analyzing the detailed behavior of an object to maintain the finished device, or to make a new device that does the same function without using part of the original.

As described above, it is very difficult to realize an optimized design because the elements and design parameters to consider are various. On the other hand, if there is an actual aircraft that has already been designed and manufactured and has excellent performance in actual operation, the design is designed in such a manner that the design is partially changed or improved to meet the needs based on the shape of the aircraft. It saves resources such as time, cost, and manpower.

However, in case of not having such an original aircraft design data source, "Comparative study on aerodynamic characteristics of airfoil using reverse engineering technique" (Jae-Hwan Sai, KAIS Fall 2007 Conference (I), 2007) A method of obtaining three-dimensional data of an airplane shape using an inverse design technique as described above has been used (see FIG. 11).

There are three main methods that are mainly used to acquire three - dimensional data of aircraft shape using the inverse design technique. First, there are direct measurement methods using a 3D scanner. Second, there are triangulation methods using a 3D laser coordinate system. Third, there is a two-dimensional indirect measurement method using photographs. Among them, the contact measurement method can obtain the most accurate data because it can measure the data as it is in the real shape, and the stereo three-dimensional measurement method in non-contact measurement method can estimate highly accurate data. However, these two methods are not applicable to the case where the object is not secured because the object to which the data is to be acquired is indispensable.

On the other hand, in the case of photogrammetry using the last method, which is a photographic method, it is possible to acquire data with only a photograph without a real object, so that this technique can be applied even when the object is not secured. More specifically, a photograph of an object to be reverse-designed or all shape information appearing in a two-dimensional form is scaled using known specifications, and then the unknown information is simulated and data is converted.

However, in the case of the two-dimensional indirect measurement method using photographs, there is a considerable possibility that the shape reproduction may be inaccurate due to factors such as the fact that the photograph itself does not contain accurate information due to lens distortion during photographing. Nevertheless, since there is only one technique that can be used to reverse the design of a real object, there is a constant need among those skilled in the art to solve such a problem.

1. "A Study on Aerodynamic Characteristics of Airfoil Using Reverse Engineering Technique", Jung-Hwan Sae, Ji-Woong Kim, Yoo-Hyung Park, Yoo Young-Hoon, Chang- Ju Kim, Sung-Nam Chung, Proceedings of the Korean Society for Aeronautical & Space Sciences ), 2007 2. Doh, Hee-Hee, "Measurements of 3D Model Shapes for Reverse Designs," Journal of the Korean Society of Visualization, Vol. 10, No. 1, pp. 55-59. , 2012 3. Kim, Jae-Won "A Case Study on the Rotational-Wise Application of Photographic Reverse Engineering Technique", Journal of the Korean Society of Aeronautical and Space Science Autumn, pp. 737 ~ 740 2014. 11. 4. Kim, Jae-Won "Reverse design study using photographs for prediction of RCS characteristics", Gyeongsang National University Master's thesis 2015.2

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a method and apparatus for designing a shape of an aircraft, So that it is possible to reproduce the shape of the aircraft. It is another object of the present invention to provide a method and apparatus for use in a three-dimensional contour design, in order to prevent the inaccuracy in a three-dimensional shape ultimately obtained by distorting information contained in a photograph itself in such a two- Dimensional image of the airplane in which the most effective two-dimensional photograph can be obtained.

According to another aspect of the present invention, there is provided a method of inverse aircraft design using a photograph, comprising: acquiring a plurality of photographs of an object of an airplane to obtain three-dimensional shape data; A scaling step of scaling the plurality of photographs to correct the aspect ratio and to synchronize scales among the photographs; A coordinate alignment step of aligning the plurality of scaled pictures in a three-dimensional spatial coordinate system; An information acquiring step of acquiring shape-specific information from an image of the photographs arranged in a three-dimensional spatial coordinate system; A shape calculating step of calculating three-dimensional shape data by calculating two-dimensional curves by estimating a path between the obtained shape singularities and constructing a three-dimensional surface by the calculated two-dimensional curves; And a control unit.

At this time, it is preferable that the photographing step is performed to photograph a photograph with a telephoto lens having a focal length of 100 mm or more, or to take a photograph taken in the above-mentioned manner, so as to reduce a difference between a photograph and a real image due to distortion.

Alternatively, the photographing step may include photographing a photograph at a distance that the area occupied by the object with respect to the viewfinder screen area is 80% to 100% at the time of zoom maximum zooming of the photographing apparatus so as to reduce a photograph- Or to obtain a photograph taken in the above-described manner.

Alternatively, the photographing step may include photographing a photograph in a direction perpendicular to the object so as to correspond to at least one of a front surface, a rear surface, an upper surface, a bottom surface, a seat surface, or a right surface of the object, Or to obtain a photograph taken in the above-described manner.

Alternatively, the photograph acquiring step is preferably performed so as to photograph a square object or a grid together with the object so as to reduce a difference between a photograph and a real object due to distortion, or obtain a photograph taken in the above-described manner.

According to the present invention, in designing the shape of an aircraft in which a real object exists, even when the object is not secured, photographs of the object are obtained and the three-dimensional shape of the object is transformed It is possible to design and reproduce it. In addition, by using the methods according to the present invention which can minimize errors in photographing, it is possible to prevent the problem that the inaccuracy in the three-dimensional shape ultimately obtained by the distortion of the information contained in the photograph itself in the two- There is an effect that can be done.

Particularly in the military / aerospace field, shape information is mostly non-public in nature, but in order to analyze competitiveness of the enemy / competitor, it is often necessary to acquire aircraft shape information of the enemy / competitor. However, according to the present invention, it is possible to reproduce three-dimensional shape data of a target airplane by obtaining or photographing a large number of photographs without using a real object, and using an inverse design technique. Or reverse, it is possible to know to what extent the reverse design using such photographs is possible, so that if the airplane shape photographs are disclosed, there is no danger of exposing them to the enemy / competitor There is also an effect that can be done.

In addition, it is not easy to achieve three-dimensional coordinate by actual measurement due to the characteristics of the aircraft shape itself. In the case of performing an improvement design for modifying a part of the aircraft rather than designing the whole body of the aircraft, It is possible to perform the design work very effectively and efficiently by utilizing the reverse design technique.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart of a method of inverse aircraft shape design using photographs of the present invention. FIG.
2 is a flow chart showing an example of each step of an aircraft shape reverse design method using the photograph of the present invention.
FIGS. 3 to 5 illustrate various embodiments of an error reduction photographing method in the aircraft shape reverse design method using the photograph of the present invention.
FIGS. 6 to 10 illustrate various examples of the method of reverse designing an aircraft using photographs of the present invention.

Hereinafter, a method of reversing an aircraft shape using a photograph according to the present invention having the above-described configuration will be described in detail with reference to the accompanying drawings.

FIG. 1 is a flow chart of an aircraft shape reverse design method using the photograph of the present invention, and FIG. 2 is an illustration of each step of the method. As shown in FIGS. 1 and 2, the method of reverse designing an aircraft using the photograph of the present invention includes a photograph acquiring step, a coordinate aligning step, an information acquiring step, and a shape calculating step. 1 and 2, the method of reverse designing an aircraft using the photograph of the present invention will be described in detail.

First, when an object to be calculated is selected and determined, a plurality of photographs of the object of the airplane to obtain the three-dimensional shape data are acquired in the photograph acquiring step. The method of acquiring the photograph may be to take a photograph of the object directly, but in the case where it is impossible to obtain the real object, the already taken photograph may be obtained and used by searching through the Internet or the like. As described above, the method of reverse designing an aircraft using the photograph of the present invention performs a reverse design of a three-dimensional shape based on a photograph of an object, not a real object itself. Therefore, in the case of the direct measurement method using a three-dimensional scanner or the stereo three-dimensional measurement method using two cameras, it is possible to realize the reverse design of the three-dimensional shape even when the real object is not possessed,

In the scaling step, a plurality of photographs obtained in the photograph acquiring step are scaled to correct the aspect ratio for each photograph, and the scales of the plurality of photographs are synchronized with each other. When a three-dimensional object is photographed with a two-dimensional photograph, inevitably, the distortion due to the perspective is generated. In addition, there are distortions caused by the wide angle of the lens. . Because of this problem, it is necessary to correct the aspect ratio basically for each photograph. Also, with respect to a plurality of photographs, since the objects in the photograph are large and small and the photographs themselves are large and small, it is necessary to align them with each other, which is scale synchronization. All of these tasks are ultimately the task of scaling the object image shown in each of the photographs, and these operations are collectively referred to as scaling.

In the coordinate alignment step, a plurality of the scaled scaled pictures are arranged on a three-dimensional spatial coordinate system. That is, for example, the photographic images taken from the upper side are arranged side by side in the XY plane, the photographic images taken from the side are arranged side by side on the YZ plane, the photographic images taken from the front side are arranged side by side on the ZX plane, Dimensional image to be a projected image on each plane with respect to the dimensional shape. In order to reproduce the three-dimensional shape as accurately as possible, it is preferable to acquire photographs photographed in at least three directions in the photograph acquiring step, considering the concrete method of the coordinate aligning step.

In the information acquisition step, the shape-specific information is obtained from the images of the photographs arranged in the three-dimensional spatial coordinate system in the coordinate alignment step. The shape-specific-point information refers to the coordinates of a point necessary for calculating the shape data. For example, the shape-specific-point information may be the coordinates of the points forming the outline basically. In addition, if there is a part such as a protruding part or a depressed part which is particularly projected on the body, which influences the overall shape, the coordinates of the points constituting the outline of this part may also be the shape specific information. Of course, it is needless to say that the present invention is not limited to these examples, and that any coordinates of a point necessary for calculating shape data are included in the shape singularity information.

In the shape calculating step, the path between the shape singularities obtained in the information obtaining step is estimated to calculate the two-dimensional curves. By constructing the three-dimensional surface with the two-dimensional curves thus calculated, ultimately, Dimensional shape data. In the schematic description of the inverse design technique, it is explained that in the reverse design technique, the photograph of the object to be back-designed or all the shape information displayed in the two-dimensional form is scaled using known specifications, The shape-specific-point information is a 'photograph information or a shape information in a two-dimensional shape,' and a step of calculating a two-dimensional curve by path estimation between the shape-specific points and a step of forming a three-dimensional surface with the two- Information is simulated and converted into data.

As a result, the three-dimensional shape data of the desired aircraft object can be calculated and secured. By using the three-dimensional shape data, the object original can be reproduced as it is, , Various design work such as virtual or actual production of the improvement model can be freely performed by further performing the improvement design on the three-dimensional shape data. Accordingly, it is possible to carry out simulation or actual experiments such as aerodynamic analysis or the like on a three-dimensional shape model which is variously changed while adjusting a desired design parameter, thereby deriving a more optimized design or deriving an improved design Can be freely performed.

On the other hand, according to the present invention, since a reverse design process is performed based on a photograph as described above, when there is an error in the photograph itself, a large error occurs in the finally formed three-dimensional shape. However, as described above, when a three-dimensional object is photographed in a two-dimensional photograph, inevitably distortion is caused by the perspective, and distortion caused by the wide angle of the lens occurs. many. Therefore, it is necessary to make efforts to reduce the error between the photograph and the real image due to the distortion in the photograph obtained in the photograph acquiring step. FIGS. 3 to 5 illustrate various embodiments of the error reduction photographing method in the aircraft contour reverse design method using the photograph of the present invention, and various error reduction methods in the photograph obtaining step will be described.

In one embodiment, it is desirable to take a photograph with a telephoto lens having a focal length of 100 mm or more, or obtain a photograph taken in the above-described manner. As is generally well known, in the case of a fisheye lens or a wide-angle lens, since the focal length of the lens itself is considerably short by design, distortion of the photographed image due to the lens itself is considerably large. On the other hand, since the telephoto lens is designed in consideration of the long distance photographing from the original, the focal length is long, and the image distortion tendency is relatively smaller than that of the wide angle lens. Fig. 3 (A) shows an aircraft body photographed near by using a general wide-angle lens, and Fig. 3 (B) shows the same aircraft body photographed by using a telephoto lens. 3 (A) and 3 (B) are all the same, the helicopter blade portion is conspicuously bent in Fig. 3 (A), whereas in Fig. 3 (B) . Fig. 3 (C) is a front view of the object shown in Figs. 3 (A) and 3 (B), that is, actual design data. Compared with FIG. 3 (C), it can be seen that the photograph of FIG. 3 (B) provides an image that is fairly close to the actual design data. Fig. 4 (A) is a photograph taken at a long distance, Fig. 4 (B) is a photograph taken at a close distance, and Fig. 4 You can see that the photographs are much less distorted by the perspective.

As another embodiment, it is preferable to take a photograph at a distance where the area occupied by the object is 80% to 100% with respect to the viewfinder screen area at the zoom maximum zooming of the photographing apparatus, or obtain a photograph taken in the above-described manner Do. As described above, even if a telephoto lens is used, it is inevitable that distortion errors due to perspective can not be ignored unless photographs are taken sufficiently far away. On the other hand, if you shoot too far away, the object image may appear small enough to make it difficult to obtain shape information, which of course can not be used for reverse engineering. However, it is difficult to set a certain reference distance in a collective manner since how far away is preferable depends on the size of the object itself. On the other hand, on the screen confirmed by the viewfinder of the photographing apparatus itself, the photographing distance may become longer as the zooming of the photographing apparatus is enlarged. That is, in a state in which the zoom of the photographing apparatus is maximized, the object image shown by the viewfinder is sufficiently visible in the screen (in the present invention, the area occupied by the object with respect to the viewfinder screen area is 80 To 100%), it is possible to simultaneously achieve the above-mentioned condition [distance far enough to minimize the tendency of perspective distortion] and [adequately large image on the screen to be available for reverse design] can do.

As another embodiment, it is preferable to take a picture in a direction perpendicular to the object or to obtain a picture photographed in the above-described manner so as to correspond to at least one of the front, rear, top, bottom, left or right side of the object Do. Ultimately, the data to be obtained is three-dimensional data, and most of the general designs are in the form of a front view, a top view, and a side view. The most commonly used three-dimensional coordinate system is the XYZ coordinate system. Therefore, using the front or rear (ZX plane projection image), top or bottom (XY plane projection image), and seating or right side (YZ plane projection image) can be used to achieve the most efficient three-dimensional shape.

As another embodiment, it is preferable to take a photograph so that a square object or a grid is taken with the object, or obtain a photograph taken in the above-described manner. As described above, the photographs obtained by the photograph acquiring step are subjected to the scaling step before the coordinate aligning step. In this case, synchronous scaling to match the sizes of a plurality of pictures is relatively easy since one suitable one of the pictures is selected as a reference picture and then adjusted. However, for a single photograph, it is practically impossible to correct the aspect ratio in the photograph with only the object image in the image that may be distorted. To avoid this problem, a grid or square object is taken with the object so that it can be used as a reference for aspect ratio correction when photographing. By correcting the aspect ratio of the photographed photographic grid or the square object image, the aspect ratio of the object image can also be corrected naturally. FIG. 5 shows an actual example of such a process. In FIG. 5 (A), a grating 2 is placed behind the object 1, and then the image is used for scaling and coordinates An example of a series of processes in which the shape calculation is performed as shown in Fig. 5 (C) is shown.

6 to 9 illustrate various examples of the method of inverting the shape of an aircraft using the photograph of the present invention.

FIG. 6 shows an example in which photographs of various types of helicopters are acquired and their shapes are inversely designed to make three-dimensional models, and then the modified three-dimensional models are used to analyze the remodeling plan. FIG. 7 shows an example of analyzing aerodynamic characteristics and performing performance prediction by performing simulation or the like using these three-dimensional models. If you have to develop a new helicopter completely, you will need a huge amount of time, manpower, and cost resources if you design from scratch. However, as shown in FIGS. 6 and 7, when the three-dimensional shape information is acquired through the reverse design for various candidate models used for the purpose similar to the desired purpose, the desired optimal helicopter shape can be obtained more efficiently It is possible to achieve remarkable resource saving.

FIGS. 8 to 10 show examples of a model that exists in the real world but does not have three-dimensional shape information because it is a spherical model or a foreign / third-party model. FIG. 8 is an example of utilizing an inverse design to find an optimum position for mounting a radio antenna in a helicopter. The three-dimensional shape data obtained through the reverse design is used to obtain thermal analysis data for the radio high temperature operation, The aerodynamic load data of the external antennas, and so on, and successfully selected the optimum mounting position. FIG. 9 is an example of improving the shape by applying the shape conditions obtained by the original prior research after the 3D shape data is created through the reverse design for the foreign / third-party model, and the improved shape The actual production of the improvement type as shown in the lower part of FIG. 9 has also been successfully accomplished. FIG. 10 shows an example in which three-dimensional shape information of a ship is obtained through a reverse design in order to study a loading plan for a ship which is also a real product but does not have a three-dimensional drawing, It is possible to apply a variety of loading methods while easily changing the condition in the virtual space having the three-dimensional shape data, and thus it is possible to remarkably improve the user's convenience.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It goes without saying that various modifications can be made.

1: object 2: Grid

Claims

A photograph acquiring step of acquiring a plurality of photographs of an object of an airplane to obtain three-dimensional shape data;
A scaling step of scaling the plurality of photographs to correct the aspect ratio and to synchronize scales among the photographs;
A coordinate alignment step of aligning the plurality of scaled pictures in a three-dimensional spatial coordinate system;
An information acquiring step of acquiring shape-specific information from an image of the photographs arranged in a three-dimensional spatial coordinate system;
A shape calculating step of calculating three-dimensional shape data by calculating two-dimensional curves by estimating a path between the obtained shape singularities and constructing a three-dimensional surface by the calculated two-dimensional curves;
Wherein the step of designing the shape of the aircraft includes the steps of:

2. The method of claim 1,
In order to reduce errors due to distortion and photographs,
A photograph is taken with a telephoto lens having a focal length of 100 mm or more, or a photograph taken in the above-described manner is obtained.

2. The method of claim 1,
In order to reduce errors due to distortion and photographs,
Wherein a photograph is taken at a distance such that the area occupied by the object is 80% to 100% with respect to the viewfinder screen area when zooming the photographing apparatus to the maximum zoom position, or a photograph taken in the above-described manner is obtained Method of reverse shape design of aircraft.

2. The method of claim 1,
In order to reduce errors due to distortion and photographs,
Wherein photographing is performed in a direction perpendicular to the object, or photographs photographed in the above-described manner are obtained so as to correspond to at least one of front, rear, top, bottom, left or right sides of the object Method of reverse shape design of aircraft.

2. The method of claim 1,
In order to reduce errors due to distortion and photographs,
Wherein a photograph is taken so that a square object or a grid is photographed together with the object, or a photograph taken in the above-described manner is obtained.