CN115307865A - Model deformation measurement method for high-temperature hypersonic flow field - Google Patents
Model deformation measurement method for high-temperature hypersonic flow field Download PDFInfo
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Abstract
The invention discloses a model deformation measurement method facing a high-temperature hypersonic flow field, which relates to the field of wind tunnel experiments and is characterized in that a calibration plate and a front light are used for imaging, manual marking points are not required to be arranged, a test model boundary can be directly obtained, and the test model boundary is used for realizing or modeling model head positioning so as to realize or model displacement and deformation measurement; the problem that the existing vision measurement method cannot be used for pain points in a high-temperature flow field under the condition that no manual marking points are arranged is solved; the method can be used for high supersonic velocity flow field scenes, and solves the problem of shock wave interference existing in the existing schlieren measuring method.
Description
Technical Field
The invention relates to the field of wind tunnel experiments, in particular to a model deformation measurement method for a high-temperature hypersonic flow field.
Background
In a wind tunnel experiment, a test model can deform or displace a head under the action of pneumatic load. In a normal-temperature and low-speed wind tunnel, a vision measurement method is generally adopted for measuring the attitude and the deformation of a wind tunnel model. In the prior art, manual marking points are usually pasted on the surface of a test model, the manual marking points are shot by a camera, three-dimensional coordinates of the manual marking points are calculated, and deformation of the test model is calculated through the three-dimensional coordinates.
The method is difficult to use in a high-temperature/hypersonic wind tunnel, because the temperature of the wind tunnel is very high and reaches 1000 ℃, the stuck artificial mark points are easy to burn. In addition, in order to realize the measurement of the head displacement of the test model, a schlieren measurement system is generally adopted at present. Under the condition of no shock wave, a model boundary image can be obtained, and under the condition of laser, the head is covered by the shock wave, so that the subsequent measurement cannot be carried out.
Disclosure of Invention
The invention aims to realize the measurement of the deformation of a test model in a hypersonic wind tunnel or a high-temperature wind tunnel and overcome the influence of shock wave interference.
In order to achieve the above object, the present invention provides a method for measuring model deformation facing a high-temperature hypersonic flow field, the method comprising:
step 1: installing a test model in a wind tunnel, wherein the wind tunnel is a hypersonic wind tunnel or a high-temperature wind tunnel;
and 2, step: installing a light source and image acquisition equipment on the same side of the test model;
and 3, step 3: defining a first measurement plane coordinate system of the test model based on a calibration plate;
and 4, step 4: testing a test model in the wind tunnel, and shooting a plurality of images with time sequence by using the image acquisition equipment to obtain an image set;
and 5: selecting a reference image from the image set, selecting a preset point position to be measured from the reference image, and calculating first position coordinate information of the preset point position in the first measurement plane coordinate system according to a calibration result of image acquisition equipment;
step 6: selecting a first image after the reference image in the image set, finding the preset point position in the first image;
and 7: calculating second position coordinate information of the preset point position in the first image in the first measurement plane coordinate system;
and 8: and calculating to obtain the displacement of the preset point position based on the first position coordinate information and the second position coordinate information, and obtaining the deformation of the test model based on the displacement.
The method comprises the following steps: in order to solve the problems in the background technology, the invention provides a front light illumination imaging method, through front light illumination, an image with clear model boundaries can be obtained by using the prior of strong reflection on the surface of a test model, and the method can be used for model deformation measurement according to the model edges.
Front light illumination imaging: the camera and the light source are positioned at the same side, the light source projects strong light to the surface of the measured object, the measured object reflects light to the camera, and the camera receives the light on the surface of the measured object, so that the brightness of the measured object is separated from the brightness of the background, and the image acquired by people can be shot; compared with a schlieren imaging method: the light source is positioned on the back of the measured object, the camera is positioned in front of the measured object, and the light source and the camera are not positioned on the same side; therefore, after the light source passes through the flow field, the light source is interfered by shock waves; on the contrary, the front light illumination imaging is directly reflected by the measured object after being projected from the measurement, and the energy of reflected light is stronger and is not interfered by shock waves; further: compared with the traditional method for pasting the artificial marking points, the method for pasting the artificial marking points on the surface of the measured object does not need to paste the artificial marking points on the surface of the measured object in the manner of using the calibration plate, and is not interfered by high-temperature air flow; therefore, on the basis, the acquired high-contrast target image is utilized to complete feature matching and positioning by utilizing the contour information of the target, and measurement of model displacement, deformation, posture and the like is realized.
Preferably, the method obtains a transformation relation between the spatial coordinates and the pixel coordinates in the image by using a vision measurement principle, and then calculates the first position coordinate information and the second position coordinate information based on the transformation relation between the spatial coordinates and the pixel coordinates in the image.
Preferably, the conversion relationship between the spatial coordinates and the pixel coordinates in the image is:
wherein z is c Is a scale factor, u is the image abscissa, v is the image ordinate, c x As the abscissa of the optical center, c y Is the optical center ordinate, x w Is the abscissa, y, of the wind tunnel coordinate system w Is the lower ordinate, z, of the wind tunnel coordinate system w Is a vertical coordinate, M, in a wind tunnel coordinate system 1 For internal reference of image acquisition equipment, M 2 For the external parameter of the image acquisition equipment, M is a projection matrix, R is a rotation matrix, T is a translation vector, f u ＝f·s x And f v ＝f·s y Respectively representing the equivalent pixel focal length of the image acquisition equipment in the u and v directions, f is the equivalent focal length, s x And s y Is a scale factor.
Preferably, the calibration plate comprises a plate body, and a plurality of calibration points are uniformly distributed on the plate body. The plate body can be used in a hypersonic wind tunnel or a high-temperature wind tunnel, and the establishment and calibration of a coordinate system can be realized by utilizing a plurality of distributed calibration points.
Preferably, in order to efficiently and accurately find the preset point position in the subsequent image, the method finds the preset point position in the first image by an image content matching method or an image shape matching method.
Preferably, the method calculates the corresponding displacement amount by changing the coordinate information of the preset point position in the front and back images, and the method calculates the displacement amount of the preset point position by adopting the following method:
the first position coordinate is (X) 0 ，Y 0 ) And the second position coordinate is (X) t ，Y t )；
Wherein D is y Is the displacement in the y direction, D, of the wind tunnel coordinate system x Is the displacement in the x direction, D, of the wind tunnel coordinate system xy Is the displacement in the x and y planes of the wind tunnel coordinate system.
Preferably, the method adopts a direct linear transformation method or an RAC two-step method or a Zhang friend calibration method to calibrate the image acquisition equipment.
Preferably, in order to eliminate image noise, after the image is acquired by the image acquisition device, the method processes the image by using an image processing method:
carrying out median filtering denoising on the image, carrying out sub-pixel precision image edge extraction on the denoised image, and fitting the extracted edge image to find the measurement target position of the test model.
Preferably, the method finds the preset point position image in the first image by the following image matching method: and taking the measuring point as a center, setting a rectangle along the axial direction of the test model, selecting an image block from the reference image as a reference module based on the rectangle, and then searching for an optimal matching image by using a criterion of the reference module in the image to be matched, namely a center-removing normalized cross-correlation criterion.
The adopted criterion is the de-center normalized cross-correlation criterion-ZNCC criterion which can better solve the problem of image brightness change, so that the image brightness is darkened due to water mist in the test process, and the matching can be realized. Under the ZNCC criterion, the best matching pixel has a larger correlation coefficient.
Preferably, in order to realize the measurement of the bending deformation of the test model, a plurality of preset point positions distributed along the axial direction of the test model are selected from a reference image, first angle information of a connecting line between two adjacent preset point positions is obtained in the reference image through calculation, second angle information of a connecting line between two adjacent preset point positions is obtained in the first image through calculation, a corresponding connecting line angle variation is obtained through calculation based on the second angle information and the corresponding first angle information, and the bending deformation of the test model is obtained based on the connecting line angle variation.
One or more technical schemes provided by the invention at least have the following technical effects or advantages:
compared with the prior art, the method has the advantages that manual marking points are not required to be arranged, the boundary of the test model can be directly obtained, the head of the test model is positioned by utilizing the boundary of the test model, and the displacement and deformation measurement of the test model is further realized; the problem that the existing vision measurement method cannot be used for pain points in a high-temperature flow field under the condition that no manual marking point is arranged is solved;
the method can be used for high supersonic flow field scenes, and solves the problem of shock wave interference existing in the conventional schlieren measurement method.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention;
FIG. 1 is a schematic flow diagram of a model deformation measurement method for a high-temperature hypersonic flow field;
FIG. 2 is a schematic view of the principle of vision measurement in the present invention;
FIG. 3 is a schematic view of the construction of the calibration plate of the present invention;
FIG. 4 is a schematic view of the present invention with the calibration plate placed parallel to the measurement side of the test model;
FIG. 5 is a schematic representation of extracted experimental model boundary results;
FIG. 6 is a schematic diagram illustrating a method for calculating an angle between two points AB.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments of the present invention and features of the embodiments may be combined with each other without conflicting with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described and thus the scope of the present invention is not limited by the specific embodiments disclosed below.
Example one
Referring to fig. 1, fig. 1 is a schematic flow chart of a model deformation measurement method for a high-temperature hypersonic flow field, and an embodiment of the present invention provides a model deformation measurement method for a high-temperature hypersonic flow field, where the method includes:
step 1: installing the test model in a wind tunnel, wherein the wind tunnel is a hypersonic wind tunnel or a high-temperature wind tunnel;
and 2, step: installing a light source and image acquisition equipment on the same side of the test model;
and step 3: defining a first measurement plane coordinate system of the test model based on a calibration plate;
and 4, step 4: testing a test model in the wind tunnel, and shooting a plurality of images with time sequence by using the image acquisition equipment to obtain an image set;
and 5: selecting a reference image from the image set, selecting a preset point position to be measured from the reference image, and calculating first position coordinate information of the preset point position in the first measuring plane coordinate system according to a calibration result of the image acquisition equipment;
step 6: selecting a first image after the reference image in the image set, finding the preset point position in the first image;
and 7: calculating second position coordinate information of the preset point position in the first image in the first measuring plane coordinate system;
and step 8: and calculating to obtain the displacement of the preset point position based on the first position coordinate information and the second position coordinate information, and obtaining the deformation of the test model based on the displacement.
The displacement in different directions and positions represents the deformation of the test model in different positions or different directions, corresponding deformation can be calculated according to specific different displacements, and the calculation of which position or displacement in which direction can be designed according to specific deformation calculation requirements is not specifically limited.
In the embodiment of the present invention, the light source may be a corresponding lighting device or apparatus, such as an LED lighting lamp, and the image capturing device may be a video camera or a camera, and the present invention is not limited specifically.
The hypersonic wind tunnel is a wind tunnel with a flow field speed exceeding 5Ma, and the high-temperature wind tunnel is a wind tunnel exceeding normal temperature.
In the embodiment of the invention, the test model is tested in the wind tunnel, the test model can be a model in any shape, and the invention is not limited specifically.
The basic principle of the test model deformation measurement in the invention is as follows:
the vision measurement is to measure the 3-dimensional or 2-dimensional space position and displacement of the measured object by a vision imaging method according to a camera pinhole imaging model. In the invention, a vision measurement method is adopted for realizing the 2-dimensional in-plane deformation measurement of the model.
Briefly describing the principle of vision measurement, as shown in FIG. 2, a point P in physical space is imaged as P' in the camera imaging plane. Then the point P and the corresponding point P' in the image need to undergo three coordinate transformations:
(1) Conversion of world coordinates to camera coordinates
The world coordinate system is used as a space reference frame and is generally selectedEasy to describe the geometrical dimensions of the object in space, with world coordinates O w X w Y w Z w Wherein, O w Is an origin, X w 、Y w 、Z w Three axes of a coordinate system, and the world coordinate of any point in space is marked as (x) w ,y w ,z w ) Wherein x is w X-coordinate, y, being world coordinates w Y-coordinate, z, being world-coordinate w Is the z coordinate of the world coordinate. The camera coordinate system is the optical center O of the camera lens c Is the origin of coordinates, X c O c Y c Plane parallel to the image plane, Z c The axis coincides with the optical axis direction. The spatial points can be expressed in camera coordinates as:
wherein X c As x-coordinate, y-coordinate in the camera coordinate system c As the y-coordinate, z, of the camera coordinate system c Is the z coordinate of the camera coordinate system, R is the rotation matrix, and T is the translation vector.
Secondly, transforming the camera coordinate system into an image physical coordinate system
Midpoint (x) of camera coordinate system c ,y c ,z c ) The projection in image coordinates is (x, y), the perspective transformed by the camera projection has:
f is the equivalent focal length, i.e., the distance between the camera plane and the interest, and converts the above equation into the following matrix relation:
conversion of image physical coordinates to a computer pixel coordinate system
The coordinate unit of the physical coordinates of the image is generally mmThe unit, the origin of coordinates also called the image principal point coordinates, is usually at the center of the image, and is represented by (c) x ,c y ) In computer images, the coordinate origin is generally at the upper left corner of the image, and the pixel coordinates represent the row and column positions of the image points and are marked as (u, v). Conversion relationship between image physical coordinates and pixel coordinates:
(s x ,s y ) The scale factors respectively represent the number of pixels in unit distance in x and y directions in image coordinates.
By combining the coordinate transformation, the direct conversion relation between the space coordinate and the pixel coordinate can be obtained as follows:
wherein z is c Is a scale factor, u is the image abscissa, v is the image ordinate, c x As the abscissa of the optical center, c y Is the optical center ordinate, x w Is the abscissa, y, of the wind tunnel coordinate system w Is the lower ordinate, z, of the wind tunnel coordinate system w Is a vertical coordinate, M, in a wind tunnel coordinate system 1 For the internal reference of the image acquisition device, M 2 For the external parameter of the image acquisition equipment, M is a projection matrix, R is a rotation matrix, T is a translation vector, f u ＝f·s x And f v ＝f·s y Respectively representing the equivalent pixel focal length of the image acquisition equipment in the u and v directions, wherein f is the equivalent focal length, s x And s y Is a scale factor.
The above is a linear imaging model in an ideal state, and an optical imaging system in practice has errors due to design and assembly of a lens. Corresponding optical distortion is inevitably brought, mainly radial distortion, eccentric distortion and thin prism distortion are brought, the radial distortion and the eccentric distortion are considered under the general condition, and a radial distortion model is adopted in the invention.
Therefore, through the above-mentioned 3 times coordinate transformation, a connection between a point P in space and a point P' in the image is established. As can be seen from equation 5, only 1 point in the image is used, and the spatial three-dimensional coordinates cannot be determined, because two cameras are generally required to obtain the real three-dimensional coordinates, 2 sets of image coordinates are provided, and then the three-dimensional coordinates in the world coordinate system are estimated according to the least squares. For the application of the invention, it is assumed that the wind tunnel model is displaced in the observation plane, that is to say in spatial three-dimensional coordinates (x) w ,y w ,z w ) In z w Is a known term and is constant, so that the displacement measurement of the measured object in a two-dimensional plane can be realized by utilizing image coordinates (u, v).
Principle of model deformation measurement:
the calibration plate shown in fig. 3 is characterized in that 1 in fig. 3 is a plate body of the calibration plate, and 2 is a marking point, wherein the calibration plate can be made of transparent glass, the marking point can be black and circular, and the marking plate can be added on the calibration plate in a smearing mode. The marking plate is used for defining a world coordinate system (x) w ,y w ,z w ). The origin may be a center point in the marking board when defining the world coordinate system based on the marking board. For two-dimensional deformation measurement, setting a measurement object z w =0, the model measurement coordinate system (X, Y) is thus defined.
In order to reduce the perspective distortion interference, as shown in fig. 4, a in fig. 4 is the distance between the mark points, before the test, the calibration plate and the measurement side of the test model are placed in parallel, the camera takes the current calibration plate image as far as possible in a front view, and the calibration plate image is used for defining a model measurement plane coordinate system (X, Y).
The basic method for measuring the deformation of the test model comprises the following steps:
selecting the position of the point to be measured in the image of a reference frame (such as a first frame image), such as the center of a circle of a model head, calculating the position (X) of the measuring point in a defined measuring plane according to the calibration result of the camera and the equation of the formula (5) 0 ，Y 0 )；
Then, through image processing algorithms, such as image content matching, image shape matching and other methods, finding the position of the selected measuring point in subsequent frames;
according to the camera calibration result and the equation of the formula (5), the position (X) of the measuring point in the defined measuring plane is obtained t ， Y t )；
And calculating the displacement amount on the time axis according to the position result:
wherein D is y Is the displacement in the y direction under the wind tunnel coordinate system, D x Is the displacement in the x direction, D, of the wind tunnel coordinate system xy The displacement in the x and y planes of the wind tunnel coordinate system.
Calibrating a vision measuring system:
camera calibration
The camera calibration is used to determine internal and external parameters in the camera projection equation through a series of reference points whose spatial locations are known. Common camera calibration methods include a direct linear transformation method, an RAC two-step method and a Zhang Zhengyou calibration method. The Zhang Zhengyou calibration method utilizes the corresponding relation between the world coordinates of the characteristic points on the calibration plate at a plurality of different visual angle positions and the image coordinates of the image points on the image to calibrate the camera, and has the advantages of simple use, high calibration precision and the like. Therefore, the invention adopts the Zhangyingyou-based calibration method to calibrate the camera and carries out nonlinear distortion correction on the image shot by the camera.
The calibration precision analysis can be used for measuring system calibration precision evaluation, and can adopt a plurality of calibration plate images to carry out test calibration precision evaluation, and the specific test evaluation mode is not specifically limited in the embodiment of the invention.
Wherein, fig. 3 is the calibration plate image of gathering, and calibration plate size is 10 × 10cm, has contained 49 centre of a circle mark points altogether of 7 × 7, and the distance is 6.25mm between the mark point, and calibration plate machining precision is 1um. The size of the calibration plate, the number of circle center marking points and the distance between the circle center marking points can be adjusted according to actual needs, and the embodiment of the invention is not specifically limited.
And (3) deformation measurement of a test model:
the invention relates to a method for measuring the displacement of the center of a circle of a head of a test model, which takes the center of the circle of the head of the test model as a reference and is used for measuring the displacement of the head of the test model.
The adopted image processing method comprises the following steps: the method comprises the steps of firstly carrying out median filtering denoising on an image to eliminate image noise, then carrying out sub-pixel precision image edge extraction, and then finding the center position of a head circle through circle fitting to realize head circle center tracking and measurement.
The sub-pixel edge extraction method adopted by the invention is used for determining the model boundary, and FIG. 5 shows the extracted test model boundary result. The sub-pixel edge positioning can be realized by performing function fitting on the image pixels at the edge, including Gaussian, polynomial, orthogonal basis fitting and the like, and the general precision is superior to 0.1 pixel.
After the model edge image is obtained, the circle center of the head can be obtained by performing least square-based circle fitting on the edge, so that the coordinate of the measurement point image is obtained, and the position of the measurement point in the model measurement plane can be calculated according to the calibration result.
In the invention, the number of the preset point positions can be multiple, for example, 5, the axial displacement of 5 points of the test model is measured, 5 measurement points are selected along the axial direction of the model, and the image matching method comprises the following steps: setting a rectangle by taking a measuring point as a center along the axial direction of a model, selecting an image block as a reference module, and searching an optimal matching image in an image to be matched by using the template image, wherein the adopted matching criterion is as follows: ZNCC (decentered normalized cross-correlation criterion):
wherein C is a correlation coefficient metricThe values, I (u, v) are template image pixel values, I' (u, v) are pixel values within the search area of the image to be matched, I m Is template image mean, I' m The problem of image brightness change can be solved well by adopting a ZNCC model for pixel values in the image search area to be matched, so that the image brightness is darkened due to water mist in the test process, and the matching can be realized. Under the ZNCC criterion, the best matching pixel has a larger correlation coefficient.
And estimating the angle change of every two according to the connecting line of the 5 measuring points. The method for calculating the angle of the connecting line of the two points AB is shown in FIG. 6, and the included angle between the connecting line AB and the horizontal axis is calculated, wherein the counterclockwise direction is positive and the unit is radian.
Data de-noising processing
Because the available texture information on the surface of the shooting model is small, mismatching is inevitable in the matching and measuring process, and a wrong measuring result is generated.
The invention basically realizes the displacement measurement of the test model in the special wind tunnel by comprehensively selecting and optimizing the image processing algorithm.
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 model deformation measurement method facing a high-temperature hypersonic flow field is characterized by comprising the following steps:
step 1: installing the test model in a wind tunnel, wherein the wind tunnel is a hypersonic wind tunnel or a high-temperature wind tunnel;
step 2: installing a light source and image acquisition equipment on the same side of the test model;
and step 3: defining a first measurement plane coordinate system of the test model based on a calibration plate;
and 4, step 4: testing a test model in the wind tunnel, and shooting a plurality of images with time sequence by using the image acquisition equipment to obtain an image set;
and 5: selecting a reference image from the image set, selecting a preset point position to be measured from the reference image, and calculating first position coordinate information of the preset point position in the first measurement plane coordinate system according to a calibration result of image acquisition equipment;
and 6: selecting a first image after the reference image in the image set, finding the preset point position in the first image;
and 7: calculating second position coordinate information of the preset point position in the first image in the first measurement plane coordinate system;
and 8: and calculating to obtain the displacement of the preset point position based on the first position coordinate information and the second position coordinate information, and obtaining the deformation of the test model based on the displacement.
2. The method for measuring the deformation of the model facing the high-temperature hypersonic flow field according to claim 1, wherein the method calculates the first position coordinate information and the second position coordinate information based on the conversion relation between the space coordinates and the pixel coordinates in the image.
3. The method for measuring the model deformation facing to the high-temperature hypersonic flow field according to claim 2, wherein the conversion relationship between the space coordinates and the pixel coordinates in the image is as follows:
wherein z is c Is a scale factor, u is the image abscissa, v is the image ordinate, c x As the abscissa of the optical center, c y Is the optical center ordinate, x w Is the abscissa, y, of the wind tunnel coordinate system w Is the vertical coordinate, z, of the wind tunnel coordinate system w Is a vertical coordinate, M, in a wind tunnel coordinate system 1 For the internal reference of the image acquisition device, M 2 For the external parameter of the image acquisition equipment, M is a projection matrix, R is a rotation matrix, T is a translation vector, f u ＝f·s x And f v ＝f·s y Respectively representing the equivalent pixel focal length of the image acquisition equipment in the u and v directions, f is the equivalent focal length, s x And s y Is a scale factor.
4. The method for measuring model deformation facing a high-temperature hypersonic flow field according to claim 1, wherein the calibration plate comprises a plate body, and a plurality of calibration points are uniformly distributed on the plate body.
5. The method for measuring model deformation facing to a high-temperature hypersonic flow field according to claim 1, wherein the method finds the preset point position in the first image by an image content matching method or an image shape matching method.
6. The method for measuring the model deformation facing the high-temperature hypersonic flow field according to claim 1, characterized in that the method calculates the displacement of the preset point position by adopting the following method:
the first position coordinate is (X) 0 ，Y 0 ) And the second position coordinate is (X) t ，Y t )；
Wherein D is y Is the displacement in the y direction, D, of the wind tunnel coordinate system x Is the displacement in the x direction, D, of the wind tunnel coordinate system xy Is the displacement in the x and y planes of the wind tunnel coordinate system.
7. The method for measuring the deformation of the model facing the high-temperature hypersonic flow field according to claim 1, wherein the method adopts a direct linear transformation method, an RAC two-step method or a Zhang-Yongyou calibration method to calibrate the image acquisition equipment.
8. The method for measuring model deformation facing to the high-temperature hypersonic flow field according to claim 1, characterized in that after the image acquisition device acquires the image, the method adopts an image processing mode to process the image:
performing median filtering denoising on the image, performing sub-pixel precision image edge extraction on the denoised image, and fitting the extracted edge image to find the measurement target position of the test model.
9. The method for measuring model deformation facing to the high-temperature hypersonic flow field according to claim 5, wherein the method finds the preset point position image in the first image by the following image matching method: and taking the measuring point as a center, setting a rectangle along the axial direction of the test model, selecting an image block from the reference image as a reference module based on the rectangle, and then searching for an optimal matching image by using a criterion of the reference module in the image to be matched, namely a center-removing normalized cross-correlation criterion.
10. The method as claimed in claim 1, wherein a plurality of preset point positions distributed along an axial direction of the test model are selected from a reference image, first angle information of a connection line between two adjacent preset point positions is calculated and obtained in the reference image, second angle information of a connection line between two adjacent preset point positions is calculated and obtained in the first image, a corresponding connection line angle variation is calculated and obtained based on the second angle information and the corresponding first angle information, and a bending deformation amount of the test model is obtained based on the connection line angle variation.
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| CN118032264A (en) * | 2024-04-09 | 2024-05-14 | 中国航空工业集团公司沈阳空气动力研究所 | Deformation measurement method and device suitable for high-speed wind tunnel at high temperature and high speed |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN118032264A (en) * | 2024-04-09 | 2024-05-14 | 中国航空工业集团公司沈阳空气动力研究所 | Deformation measurement method and device suitable for high-speed wind tunnel at high temperature and high speed |
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