A hypersonic wind tunnel component separation characteristic self-checking measurement system

Abstract

The application discloses a kind of high supersonic wind tunnel component separation characteristic self-checking measurement systems, including multi-view vision system, multi-view vision system has three visual angles, respectively from wind tunnel test section upper window and two side windows collection image information;Schlieren system, the light emitted by the light source of Schlieren system is vertically wind tunnel test section two side windows by the optical assembly of Schlieren system and is received after being reflected by optical assembly by the imaging assembly of Schlieren system and collection image information;Wherein, the image information of Schlieren system is checked the image information of multi-view vision system, to analyze and obtain the reliability of separation component motion characteristic measurement result.The application adopts contrast checking mode, sets multi-view vision system and Schlieren system in wind tunnel test section, verifies the measurement result of multi-view vision system using the information collected by Schlieren system, realizes the checking of the measurement result of multi-view vision measurement system, to guarantee the reliability of separation component motion characteristic measurement result.

Description

Technical Field

[0001] This invention relates to the field of hypersonic experimental technology, specifically to a self-verification measurement system for the separation characteristics of hypersonic wind tunnel components. Background Technology

[0002] Hypersonic vehicles have a wide flight corridor with broad speed and airspace characteristics. To achieve optimal aerodynamic performance, the vehicle needs to undergo component separation after reaching designated flight conditions to alter its shape. Common component separations include shield separation, booster-to-cruise stage separation, and wing separation, which differ significantly from rocket fairing separation. While rocket fairing separation is relatively simple in terms of numerical simulation and ground testing because it occurs in the outer atmosphere, hypersonic flight conditions, with their high inflow pressure, significantly affect component separation due to aerodynamic influences. The separation process involves complex shock wave / shock wave, shock wave / boundary layer interference, and multibody fluid-structure interaction problems, making it prone to collisions with the vehicle body and severely impacting flight safety.

[0003] Hypersonic vehicle component separation characteristics are complex, and the motion process of separated components is difficult to predict. Actual flight testing is costly, risky, and difficult to observe. Conducting hypersonic component separation experiments in ground wind tunnels is the main way to verify the feasibility of component separation schemes. At the same time, the experimental results are of great significance for improving the simulation accuracy of component separation and perfecting the theory of hypersonic component separation.

[0004] In hypersonic wind tunnel separation experiments, the separation characteristics of components are generally determined using multi-view vision principles. Multiple high-speed cameras are deployed to capture the motion process of the separating components, and subsequent digital image processing methods are used to obtain information such as the motion trajectory and attitude angles of the separated components. However, due to factors such as the short effective time of the hypersonic wind tunnel and the limited camera observation positions, it is difficult to assess the reliability of the measurement results. Summary of the Invention

[0005] The purpose of this invention is to provide a self-verification measurement system for the separation characteristics of hypersonic wind tunnel components, so as to solve the technical problem in the prior art that it is difficult to evaluate the reliability of measurement results due to factors such as the short effective time of the hypersonic wind tunnel and the limited camera observation position.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0007] A self-verification measurement system for the separation characteristics of hypersonic wind tunnel components includes:

[0008] A multi-view vision system, which has three perspectives, acquiring image information from the top window and two side windows of the wind tunnel test section respectively;

[0009] The schlieren system is a system in which light emitted from a light source enters through two side windows of the vertical wind tunnel experimental section of the optical component of the schlieren system, and after being reflected by the optical component, is received and acquired by the imaging component of the schlieren system to collect image information.

[0010] Specifically, the image information acquired by the schlieren system is used to verify the image information acquired by the multi-view vision system in order to analyze the reliability of the measurement results of the motion characteristics of the separated components.

[0011] As a preferred embodiment of the present invention, the multi-view vision system includes a first vision camera, a second vision camera and a third vision camera. The first vision camera and the second vision camera are respectively arranged on both sides of the outside of the wind tunnel test section, and their acquisition ends face the inside of the test section from the two side windows of the wind tunnel test section.

[0012] The third vision camera is positioned above and outside the wind tunnel test section, with its acquisition end facing inward from the top window of the wind tunnel test section.

[0013] As a preferred embodiment of the present invention, the schlieren system includes a first concave mirror and a second concave mirror, wherein the first concave mirror and the second concave mirror are respectively disposed on the outer sides of the wind tunnel test section.

[0014] The schlieren system also includes a first planar mirror and a second planar mirror. The first planar mirror is offset from the first concave mirror and is located outside the wind tunnel test section. The second planar mirror is offset from the second concave mirror and is located outside the wind tunnel test section.

[0015] The first planar mirror, the first concave mirror, the second concave mirror, and the second planar mirror constitute the optical components of the schlieren system, and the light source of the schlieren system is received by the imaging components of the schlieren system after being reflected by the first planar mirror, the first concave mirror, the second concave mirror, and the second planar mirror.

[0016] As a preferred embodiment of the present invention, the schlieren system further includes a light-shielding plate, which is disposed close to the first planar reflector and located at the focal plane of the first concave mirror. The light-shielding plate has a light-transmitting slit, and a lamp group is disposed on the other side of the light-shielding plate. The light generated by the lamp group passes through the slit on the light-shielding plate and then enters the first planar reflector.

[0017] The lamp assembly and the light shield constitute the light source of the schlieren system.

[0018] As a preferred embodiment of the present invention, the schlieren system further includes a schlieren imaging camera, which is disposed close to the second planar mirror and located at the focal plane of the second concave mirror. The schlieren imaging camera is an imaging component of the schlieren system to receive the light reflected by the second planar mirror.

[0019] As a preferred embodiment of the present invention, the first visual camera and the second visual camera are at a fixed angle to the optical axis between the first concave mirror and the second concave mirror, and the first visual camera and the second visual camera are far away from the wind tunnel test section so as not to block the optical path between the first concave mirror and the second concave mirror.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention employs a comparative verification method, setting up a multi-view vision system and a schlieren system in the wind tunnel test section. The information collected by the schlieren system is used to verify the measurement results of the multi-view vision system, thereby verifying the measurement results of the multi-view vision measurement system and ensuring the reliability of the measurement results of the motion characteristics of the separated components. Attached Figure Description

[0022] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of the self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the binocular vision measurement principle of the self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the multi-view vision measurement principle of the self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention.

[0026] Figure 4 A schematic diagram of a calibration plate in the wind tunnel test section of a self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention.

[0027] Figure 5 A schematic diagram of the imaging results of three cameras in a multi-view vision system of a self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of the separation model marker points of the self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention.

[0029] Figure 7 A schematic diagram of typical moment capture results of the self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention;

[0030] Figure 8 This is a schematic diagram of the motion trajectory of the separation model of the self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention.

[0031] Figure 9 This is a schematic diagram of the model edge detection results of the self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention;

[0032] Figure 10 This is a schematic diagram showing the comparison of multi-view vision and schlieren measurement results of the self-verification measurement system for the separation characteristics of hypersonic wind tunnel components provided in an embodiment of the present invention.

[0033] The labels in the diagram represent the following:

[0034] 1-First vision camera; 2-Second vision camera; 3-Third vision camera; 4-Lamp assembly; 5-Light shield; 6-First plane mirror; 7-First concave mirror; 8-Second concave mirror; 9-Second plane mirror; 10-Schizophonic imaging camera. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] like Figure 1 As shown, this invention provides a self-verification measurement system for the separation characteristics of hypersonic wind tunnel components, comprising:

[0037] The multi-view vision system has three perspectives, acquiring image information from the top window and two side windows of the wind tunnel test section.

[0038] The schlieren system emits light through two side windows of the vertical wind tunnel experimental section of the schlieren system's optical components. After being reflected by the optical components, the light is received and acquired by the imaging components of the schlieren system.

[0039] Among them, the image information acquired by the schlieren system is used to verify the image information acquired by the multi-view vision system in order to analyze and verify the reliability of the measurement results of the motion characteristics of the separated components.

[0040] The self-calibration measurement system of this invention mainly involves setting up a multi-view vision system and a schlieren system in the wind tunnel test section. The schlieren system is used to capture the angle information of the measurement results to verify the measurement results captured by the multi-view vision system, thereby verifying the measurement results of the multi-view vision system and ensuring the reliability of the measurement results of the motion characteristics of the separated components.

[0041] Compared to existing single multi-view vision system measurements, this invention adopts a comparative verification method. A multi-view vision system and a schlieren system are set up in the wind tunnel test section. The information collected by the schlieren system is used to verify the measurement results of the multi-view vision system, thereby verifying the measurement results of the multi-view measurement system and ensuring the reliability of the measurement results of the motion characteristics of the separated components.

[0042] Based on the above-described multi-view vision system, a preferred embodiment is provided. The multi-view vision system includes a first vision camera 1, a second vision camera 2, and a third vision camera 3. The first vision camera 1 and the second vision camera 2 are respectively disposed on the outer sides of the wind tunnel test section, and their acquisition ends face inward from the two side windows of the wind tunnel test section.

[0043] The third vision camera 3 is positioned above and outside the wind tunnel test section, with its acquisition end facing inward from the top window of the wind tunnel test section.

[0044] The multi-view vision measurement system is a tri-view vision measurement system. Its measurement principle is based on the binocular measurement principle. The first vision camera 1, the second vision camera 2, and the third vision camera 3 form three sets of binocular measurement systems in pairs. Using the principle of binocular measurement, the three sets of binocular measurement systems calculate the three-dimensional coordinates of the target object through parallax. Then, the three sets of coordinate information are fused to obtain the final model coordinate measurement result.

[0045] The principle of binocular vision measurement is as follows: Figure 2 As shown, the points corresponding to a point P in space in the camera coordinate systems of two cameras C1 and C2 are P1 and P2, respectively. The projection matrices of the cameras are M1 and M2. The relationship between P1, P2 and P can be described as follows:

[0046]

[0047] Among them, (u1,v1,1), (u2,v2,1) and (X) w ,Y w Z w,1) are the pixel coordinates of point P in the pixel coordinate system of camera C1, the pixel coordinates of point P in the pixel coordinate system of camera C2, and the three-dimensional coordinates of point P in the world coordinate system, respectively. (k = 1, 2; i = 1, 2, 3; j = 1, 2, 3, 4) are the elements in the i-th row and j-th column of matrix Mk; Z C1 and Z C2 Let P be the z-coordinate of point P in the camera coordinate system corresponding to C1 and C2. Solving the system of equations, we can obtain the coordinates (X, Z) of point P. w ,Y w Z w The four equations:

[0048]

[0049] Solving this problem yields the world coordinates (X) of point P. w ,Y w Z w ).

[0050] like Figure 3 As shown, in a trinocular measurement system, the projection points of point P onto the imaging planes of cameras C1, C2, and C3 are P1, P2, and P3, respectively. The measurement values ​​of a binocular measurement system composed of two cameras should coincide at a single point, namely the measured point P. This means that the three lines O1P1, O2P2, and O3P3 intersect at the same point P (O1, O2, and O3 are the origins of the camera coordinate systems corresponding to the three cameras). In actual use, due to measurement errors, the binocular measurement system composed of two cameras provides three sets of measurement values: the intersection point P12 of lines O1P1 and O2P2, the intersection point P13 of lines O1P1 and O3P3, and the intersection point P32 of lines O3P3 and O2P2, corresponding to the coordinates (X, Y, φ) of P12 in the world coordinate system. w12 ,Y w12 Z w12 P13 coordinates in the world coordinate system (X) w13 ,Y w13 Z w13 The coordinates of P32 in the world coordinate system (X) w32 ,Y w32 Z 32w There is a slight deviation between the coordinates of point P and the true point P. To estimate the optimal value of point P, its coordinates should satisfy the following objective function:

[0051]

[0052] By optimizing the objective function F, the optimal spatial coordinates of point P can be obtained as follows:

[0053]

[0054]

[0055] Based on the above principles, in multi-view vision measurement, marker points are created on the separated model, and then three cameras simultaneously capture the movement of the separated model. For the three images acquired at each moment, the pixel coordinates of the feature points on the model are extracted, and processed according to the above principles to obtain the spatial position of the model at that moment. By processing all the captured images sequentially, the motion trajectory of the separated model can be obtained.

[0056] Based on the above-described schlieren system, a preferred embodiment is provided. The schlieren system includes a first concave mirror 7 and a second concave mirror 8, which are respectively disposed on the outer sides of the wind tunnel test section.

[0057] The schlieren system also includes a first plane mirror 6 and a second plane mirror 9. The first plane mirror 6 is offset from the first concave mirror 7 and is located outside the wind tunnel test section. The second plane mirror 9 is offset from the second concave mirror 8 and is located outside the wind tunnel test section.

[0058] The first planar reflector 6, the first concave mirror 7, the second concave mirror 8, and the second planar reflector 9 constitute the optical components of the schlieren system. The light source of the schlieren system is reflected by the first planar reflector 6, the first concave mirror 7, the second concave mirror 8, and the second planar reflector 9 and then received by the imaging components of the schlieren system.

[0059] Based on the above-described schlieren system, a preferred embodiment is provided. The schlieren system further includes a light-shielding plate 5, which is disposed near the first planar reflector 6 and located at the focal plane of the first concave mirror 7. The light-shielding plate 5 has a light-transmitting slit, and a lamp group 4 is disposed on the other side of the light-shielding plate 5. The light generated by the lamp group 4 passes through the slit on the light-shielding plate 5 and then enters the first planar reflector 6.

[0060] Among them, the lamp group 4 and the light shield 5 constitute the light source of the schlieren system.

[0061] Based on the above-described schlieren system, a preferred embodiment is provided. The schlieren system further includes a schlieren imaging camera 10, which is disposed close to the second planar reflector 9 and located at the focal plane of the second concave mirror 8. The schlieren imaging camera 10 is the imaging component of the schlieren system to receive the light reflected by the second planar reflector 9.

[0062] Schlieren measurement principle: Schlieren utilizes the principle that the refractive index gradient of light in the measured flow field is proportional to the airflow density. When light passes through the flow field, due to the different densities in different regions, the light undergoes varying degrees of refraction, causing the light rays to deflect. It is mainly used to observe the wave system structure of the flow field around an aircraft. This patent primarily utilizes the characteristic of parallel light passing through the flow field in a schlieren instrument. The imaging results of the schlieren system camera have a fixed spatial correspondence. The schlieren imaging result is the projection of the separated model onto the plane perpendicular to the schlieren optical axis. Digital image processing technology is used to obtain the attitude angle of the separated model projected onto this plane for calibration of multi-view vision measurement results.

[0063] The system workflow is as follows:

[0064] 1) After installing the first, second, and third vision cameras, adjust the schlieren system to the working state to ensure that the beam passes through the flow field in the form of parallel light, and turn on the first, second, and third vision cameras and the schlieren camera.

[0065] 2) Place a calibration plate inside the wind tunnel test section, such as... Figure 4 As shown, the calibration of the first, second, and third visual camera matrices M1, M2, and M3 was completed. During the calibration process, the first, second, and third visual cameras simultaneously captured images of the calibration board. Typical capture results are shown below. Figure 5 As shown. Change the placement and angle of the calibration plate, and take images of it simultaneously multiple times. The placement of the calibration plate must cover the entire range of motion of the separated model.

[0066] 3) Create marker points on the separated model. The grayscale values ​​of the marker points should have a significant difference from those of the separated model itself. The marker points can be square or circular. Typical marker points include... Figure 6 As shown, the size requirement for square markers is that the marker occupies at least 10*10 pixels in the image area captured by the camera. For circular markers, the requirement is that the marker occupies at least 10 pixels in the diameter direction of the image area captured by the camera. Record the position of the markers on the model.

[0067] 4) Prepare the wind tunnel and put the first, second, and third visual cameras and the schlieren camera into a trigger-ready state. Start the experiment. Simultaneously, the wind tunnel activation module outputs trigger signals to the first, second, and third visual cameras and the schlieren camera, ensuring that each camera synchronously records the model separation process. Each camera captures the complete motion process of the separated model. Typical camera capture results at each moment are shown below. Figure 7 As shown.

[0068] 5) For each moment, extract the pixel coordinates of the corresponding marker points in the three images captured by the multi-view vision system. Identify the true coordinates of the marker points in the world coordinate system according to the principles of multi-view vision. Process all marker points sequentially to obtain their coordinate values. Combine these coordinates with the geometric features of the model's shape to calculate the motion trajectory and attitude angles (angle of attack, sideslip angle) of the model's center of mass. Typical results are shown below. Figure 8 As shown.

[0069] 6) Process the schlieren camera images and use edge detection methods to determine the edges of the model, such as... Figure 9 As shown. The projection angle of the model is determined based on the model's edge coordinates and geometric features.

[0070] 7) Repeat the above process for images captured at all times, and compare the schlieren results with the multi-view vision results to verify the reliability of the multi-view measurement results. Typical results are as follows: Figure 10 As shown.

[0071] like Figure 1 As shown, the optical axes of the first visual camera 1 and the second visual camera 2 are at a fixed angle to the first concave mirror 7 and the second concave mirror 8, and the first visual camera 1 and the second visual camera 2 are far away from the wind tunnel test section so as not to block the optical path between the first concave mirror 7 and the second concave mirror 8.

[0072] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A hyper-sonic wind tunnel component separation characteristics self-checking measurement system, characterized by, Comprise: A multi-view vision system with three view angles, respectively collecting image information from the upper window and two side windows of the wind tunnel test section; A schlieren system, the light emitted by the light source of the schlieren system is vertically incident on the two side windows of the wind tunnel test section through the optical assembly of the schlieren system, and after being reflected by the optical assembly, the image information is collected by the imaging assembly of the schlieren system; Wherein, the image information collected by the schlieren system is used to verify the image information collected by the multi-view vision system to analyze the reliability of the measurement results of the separation component motion characteristics.

2. The hyper-speed wind tunnel component separation characteristic self-checking measurement system according to claim 1, characterized in that: The multi-view vision system comprises a first vision camera, a second vision camera and a third vision camera, the first vision camera and the second vision camera are respectively arranged on the two sides outside the wind tunnel test section, and the collecting end thereof faces the inside of the test section from the two side windows of the wind tunnel test section; The third vision camera is arranged on the top of the outside of the wind tunnel test section, and the collecting end thereof faces the inside of the test section from the top window of the wind tunnel test section.

3. The hyper-speed wind tunnel component separation characteristic self-checking measurement system according to claim 2, characterized in that: The schlieren system comprises a first concave mirror and a second concave mirror, and the first concave mirror and the second concave mirror are respectively arranged on the two sides outside the wind tunnel test section; The schlieren system further comprises a first plane mirror and a second plane mirror, the first plane mirror is arranged outside the wind tunnel test section and deviates from the first concave mirror, and the second plane mirror is arranged outside the wind tunnel test section and deviates from the second concave mirror, wherein the first plane mirror, the first concave mirror, the second concave mirror and the second plane mirror constitute the optical assembly of the schlieren system, and the light source of the schlieren system is reflected by the first plane mirror, the first concave mirror, the second concave mirror and the second plane mirror, and then received by the imaging assembly of the schlieren system.

4. The hyper-speed wind tunnel component separation characteristic self-checking measurement system according to claim 3, characterized in that: The schlieren system further comprises a light shield, the light shield is arranged close to the first plane mirror and located at the focal plane position of the first concave mirror, and the light shield has a light-transmitting slit, and a lamp group is arranged on the other side of the light shield, and the light emitted by the lamp group is incident on the first plane mirror through the slit on the light shield; Wherein, the lamp group and the light shield constitute the light source of the schlieren system.

5. The hyper-speed wind tunnel component separation characteristic self-checking measurement system according to claim 4, characterized in that: The schlieren system further comprises a schlieren imaging camera, the schlieren imaging camera is arranged close to the second plane mirror and located at the focal plane position of the second concave mirror, and the schlieren imaging camera is the imaging assembly of the schlieren system to receive the light reflected by the second plane mirror.

6. The system of claim 3, wherein the first visual camera and the second visual camera are fixed angle from the optical axis between the first concave mirror and the second concave mirror, and the first visual camera and the second visual camera are distanced from the test section of the hypersonic wind tunnel so as not to block the optical path between the first concave mirror and the second concave mirror. ​

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