Self-checking measurement system for separation characteristic of hypersonic wind tunnel component

Abstract

The invention discloses a hypersonic wind tunnel component separation characteristic self-checking measurement system comprising a multi-view vision system which has three view angles and collects image information from an upper window and two side windows of a wind tunnel experiment section; light rays emitted by a light source of the schlieren system are incident through an optical assembly of the schlieren system in a manner of being vertical to two side windows of the wind tunnel experiment section, are reflected by the optical assembly, and are received by an imaging assembly of the schlieren system to acquire image information; wherein the image information collected by the schlieren system is used for verifying the image information collected by the multi-view vision system, so that the reliability of the motion characteristic measurement result of the separation part is analyzed and obtained. According to the invention, a contrast verification mode is adopted, the multi-view vision system and the schlieren system are arranged in the wind tunnel experiment section, and the measurement result of the multi-view vision system is verified by using the information collected by the schlieren system, so that the verification of the measurement result of the multi-view vision measurement system is realized, and the reliability of the measurement result of the motion characteristics of the separation part is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of hypersonic experimental techniques, and particularly to a self-checking measurement system for the separation characteristics of hypersonic wind tunnel components. Background Art

[0002] The flight corridor of hypersonic vehicles features a wide speed range and a wide airspace. To achieve the best aerodynamic performance, the vehicle needs to complete the component separation process after reaching the specified flight conditions to change its shape. Common component separations include: fairing separation, booster stage and cruise stage separation, cabin-wing separation, etc., and their separation processes are quite different from those of rocket fairing separations. For the separation of rocket fairings, since the separation process occurs in the outer layer of the atmosphere, the numerical simulation and ground tests of the fairing ejection process are relatively simple. However, under hypersonic flight conditions, the oncoming dynamic pressure is high, and the component separation process is significantly affected by aerodynamic forces. The separation process involves complex shock / shock, shock / boundary layer interference, and fluid-structure coupling problems among multiple bodies, resulting in the separation components being prone to collide with the vehicle body, seriously affecting the flight safety of the vehicle.

[0003] The separation characteristics of hypersonic vehicle components are complex, and it is difficult to predict the motion process of the separation components. Moreover, actual flight tests are costly, risky, and difficult to observe. Conducting hypersonic component separation experiments in a ground wind tunnel 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 hypersonic component separation theory.

[0004] In hypersonic wind tunnel separation experiments, the separation characteristics of components generally utilize the principle of multi-view vision. Multiple high-speed cameras are arranged to capture the motion process of the separation components, and later, information such as the motion trajectory and attitude angle of the separation components is obtained through digital image processing methods. Due to factors such as the short effective time of the hypersonic wind tunnel and the limited camera observation positions, it is difficult to evaluate the reliability of the measurement results. Summary of the Invention

[0005] The purpose of the present invention is to provide a self-checking measurement system for the separation characteristics of hypersonic wind tunnel components 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 positions.

[0006] To solve the above technical problem, the present invention specifically provides the following technical solutions:

[0007] A self-checking measurement system for the separation characteristics of hypersonic wind tunnel components, comprising:

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

[0009] A schlieren system, the light emitted by the light source of the schlieren system enters vertically through two side windows of the wind tunnel test section by means of the optical components of the schlieren system, and after being reflected by the optical components, is received by the imaging component of the schlieren system to collect image information;

[0010] Among them, the image information collected by the schlieren system is used to verify the image information collected by the multi-view vision system, so as to analyze and obtain the reliability of the measurement results of the motion characteristics of the separated components.

[0011] As a preferred solution 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 outside the wind tunnel test section, and their acquisition ends face the inside of the test section through the two side windows of the wind tunnel test section;

[0012] The third vision camera is arranged above the outside of the wind tunnel test section, and its acquisition end faces the inside of the test section through the top window of the wind tunnel test section.

[0013] As a preferred solution of the present invention, the schlieren system includes a first concave mirror and a second concave mirror, and the first concave mirror and the second concave mirror are respectively arranged outside both sides of the wind tunnel test section;

[0014] The schlieren system further includes a first plane mirror and a second plane mirror. The first plane mirror is arranged outside the wind tunnel test section deviating from the first concave mirror, and the second plane mirror is arranged outside the wind tunnel test section deviating from the second concave mirror;

[0015] Among them, the first plane mirror, the first concave mirror, the second concave mirror and the second plane mirror constitute the optical components of the schlieren system, and after 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, it is received by the imaging component of the schlieren system.

[0016] As a preferred solution of the present invention, the schlieren system further includes a light shield. The light shield is arranged close to the first plane mirror and is located at the focal plane position of the first concave mirror. The light shield has a light-transmitting slit, and a lamp group is arranged on the other side of the light shield. The light generated by the lamp group passes through the slit on the light shield and then enters the first plane mirror;

[0017] Among them, the lamp group 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 plane mirror and located at the focal plane position of the second concave mirror. The schlieren imaging camera serves as the imaging component of the schlieren system to receive the light reflected by the second plane mirror.

[0019] As a preferred embodiment of the present invention, the first vision camera and the second vision camera form a fixed angle with the optical axis between the first concave mirror and the second concave mirror, and the first vision camera and the second vision 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 beneficial effects:

[0021] The present invention adopts a control and verification method, sets a multi-view vision system and a schlieren system in the wind tunnel test section, and uses the information collected by the schlieren system to verify the measurement results of the multi-view vision system, so as to realize the verification of the measurement results of the multi-view vision measurement system, thereby ensuring the reliability of the measurement results of the motion characteristics of the separated components. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, other implementation drawings can be obtained according to the provided drawings without creative efforts.

[0023] Figure 1 Schematic structural diagram of a hypersonic wind tunnel component separation characteristic self-verifying measurement system provided by an embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the binocular vision measurement principle of a hypersonic wind tunnel component separation characteristic self-verifying measurement system provided by an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the multi-view vision measurement principle of a hypersonic wind tunnel component separation characteristic self-verifying measurement system provided by an embodiment of the present invention;

[0026] Figure 4 Schematic diagram of the calibration plate in the wind tunnel test section of a hypersonic wind tunnel component separation characteristic self-verifying measurement system provided by an embodiment of the present invention;

[0027] Figure 5 Schematic diagram of the imaging results of three cameras of the multi-view vision system of a hypersonic wind tunnel component separation characteristic self-verifying measurement system provided by an embodiment of the present invention;

[0028] Figure 6 Schematic diagram of the separation model landmark points of the self-checking measurement system for the separation characteristics of hypersonic wind tunnel components provided by the embodiments of the present invention;

[0029] Figure 7 Schematic diagram of the shooting results at typical moments of the self-checking measurement system for the separation characteristics of hypersonic wind tunnel components provided by the embodiments of the present invention;

[0030] Figure 8 Schematic diagram of the movement trajectory of the separation model of the self-checking measurement system for the separation characteristics of hypersonic wind tunnel components provided by the embodiments of the present invention;

[0031] Figure 9 Schematic diagram of the model edge detection results of the self-checking measurement system for the separation characteristics of hypersonic wind tunnel components provided by the embodiments of the present invention;

[0032] Figure 10 Schematic diagram of the comparison structure of the multi-view vision and schlieren measurement results of the self-checking measurement system for the separation characteristics of hypersonic wind tunnel components provided by the embodiments of the present invention.

[0033] The reference numerals in the figure are respectively represented as follows:

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

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] As Figure 1 shown, the present invention provides a self-checking measurement system for the separation characteristics of hypersonic wind tunnel components, including:

[0037] A multi-view vision system, which has three perspectives and collects image information from the upper window and two side windows of the wind tunnel test section respectively;

[0038] A schlieren system, the light emitted by the light source of the schlieren system enters vertically through the two side windows of the wind tunnel test section through the optical components of the schlieren system, and is received by the imaging components of the schlieren system after being reflected by the optical components to collect image information;

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

[0040] The self-checking measurement system of the present invention mainly sets a multi-view vision system and a schlieren system in the wind tunnel test section respectively, and uses the angle information of the measurement results photographed by the schlieren system to verify the measurement results photographed by the multi-view vision system, so as to realize the verification of the measurement results of the multi-view vision measurement system and ensure the reliability of the measurement results of the motion characteristics of the separated components.

[0041] Compared with the existing measurement by a single multi-view vision system, the present invention adopts a comparison and verification method, sets a multi-view vision system and a schlieren system in the wind tunnel test section, and uses the information collected by the schlieren system to verify the measurement results of the multi-view vision system, so as to realize the verification of the measurement results of the multi-view measurement system, thereby ensuring the reliability of the measurement results of the motion characteristics of the separated components.

[0042] Based on the above 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 arranged on both sides outside the wind tunnel test section, and their acquisition ends face the inside of the test section from two side windows of the wind tunnel test section;

[0043] The third vision camera 3 is arranged above the outside of the wind tunnel test section, and its acquisition end faces the inside of the test section from the top window of the wind tunnel test section.

[0044] The multi-view vision measurement system is a three-view vision measurement system. The basis of its measurement principle is the binocular measurement principle. The first vision camera 1, the second vision camera 2, and the third vision camera 3 are pairwise combined into three groups of binocular measurement systems. Using the binocular measurement principle, the three groups of binocular measurement systems calculate the three-dimensional coordinates of the target object through parallax, and then fuse the three groups of coordinate information to obtain the final model coordinate measurement result.

[0045] The binocular vision measurement principle is as Figure 2 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, and the projection matrices of the cameras are M1 and M2. Then the relationship between P1, P2 and P can be described as:

[0046]

[0047] Among them, (u1, v1, 1), (u2, v2, 1) and (X w , Y w , Z w, 1) They are respectively the pixel coordinates of point P in the pixel coordinate system where camera C1 is located, the pixel coordinates of point P in the pixel coordinate system where camera C2 is located, and the three-dimensional coordinates of point P in the world coordinate system. (k = 1, 2; i = 1, 2, 3; j = 1, 2, 3, 4) are respectively the elements in the i-th row and j-th column of matrix Mk; Z C1 and Z C2 are the z-direction coordinate values in the camera coordinates corresponding to cameras C1 and C2 for point P. By solving the system of equations, four equations about the coordinates (X w , Y w , Z w ) of point P can be obtained:

[0048]

[0049] By solving, the world coordinates (X w , Y w , Z w ) of point P can be obtained.

[0050] As Figure 3 shown, in the three-eye measurement system, the projection points of point P on the imaging planes of cameras C1, C2, and C3 are P1, P2, and P3 respectively. The measurement values of the binocular measurement systems formed by any two cameras should coincide at one point, that is, the measured point P. That is, 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 systems formed by any two cameras give three sets of measurement values, that is, 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. The coordinate values (X w12 , Y w12 , Z w12 ) of P12 in the world coordinate system, the coordinate values (X w13 , Y w13 , Z w13 ) of P13 in the world coordinate system, and the coordinate values (X w32 , Y w32 , Z 32w ) of P32 in the world coordinate system have a certain deviation from the true P point. In order to estimate the optimal value of point P, its coordinate values 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:

[0053]

[0054]

[0055] According to the above principle, when performing multi-view vision measurement, fiducial points are made on the separated model, and then three cameras synchronously photograph the movement process of the separated model. For each of the three images obtained at each moment, the pixel coordinates of the feature points on the model are extracted, and the spatial position of the model at that moment can be obtained by processing according to the above principle. By sequentially processing all the images obtained by photographing, the movement trajectory of the separated model can be obtained.

[0056] Based on the above 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 arranged outside both sides of the wind tunnel test section;

[0057] The schlieren system further includes a first plane mirror 6 and a second plane mirror 9. The first plane mirror 6 is arranged outside the wind tunnel test section deviating from the first concave mirror 7, and the second plane mirror 9 is arranged outside the wind tunnel test section deviating from the second concave mirror 8;

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

[0059] Based on the above schlieren system, a preferred embodiment is provided. The schlieren system further includes a light shield 5. The light shield 5 is arranged close to the first plane mirror 6 and is located at the focal plane position of the first concave mirror 7, and the light shield 5 has a light-transmitting slit. On the other side of the light shield 5, a lamp group 4 is arranged. The light generated by the lamp group 4 passes through the slit on the light shield 5 and then enters the first plane mirror 6;

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

[0061] Based on the above schlieren system, a preferred embodiment is provided. The schlieren system further includes a schlieren imaging camera 10. The schlieren imaging camera 10 is arranged close to the second plane mirror 9 and is located at the focal plane position 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 plane mirror 9.

[0062] Schlieren measurement principle: The schlieren instrument utilizes the principle that the refractive index gradient of light in the measured flow field is proportional to the air density of the flow field. When light passes through the flow field, due to the different densities in different regions of the flow field, the light will undergo different degrees of refraction, resulting in the deviation of the light. It is mainly used to observe the wave system structure of the flow field around the aircraft. This patent mainly utilizes the characteristic that the parallel light of the schlieren instrument passes through the flow field. There is a fixed spatial correspondence relationship between the imaging results of the schlieren system camera. The schlieren imaging result is the projection of the separated model in the plane perpendicular to the schlieren optical axis. Digital image processing technology is used to obtain the attitude angle of the separated model projection in this plane for calibrating the results of multi-view vision measurement.

[0063] The system working process is as follows:

[0064] 1) Install the first, second, and third vision cameras, adjust the schlieren system to the working state, ensure that the light 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 board in the wind tunnel test section, as Figure 4 shown, and complete the calibration of the matrices of the first, second, and third vision cameras M1, M2, and M3. During the calibration process, the first, second, and third vision cameras synchronously capture the images of the calibration board. The typical captured results are as Figure 5 shown. Change the placement position and angle of the calibration board, and synchronously capture its images multiple times. The placement position of the calibration board needs to cover the entire movement range of the separated model.

[0066] 3) Make marking points on the separated model. The imaging gray value of the marking points has a significant difference from the separated model body. The marking points can be square or circular. The typical marking points are as Figure 6 shown. For the square marking points, the requirement for the size is that the number of pixels occupied by the marking points in the image area in the camera capture result is not less than 10*10. For the circular marking points, the requirement is that the number of pixels in the diameter direction of the marking points occupied by the marking points in the capture result is not less than 10 pixels. Record the positions of the marking points on the model.

[0067] 4) Prepare the wind tunnel and make the first, second, and third vision cameras and the schlieren camera in the waiting trigger state. Start the experiment. When starting the wind tunnel, the synchronous trigger module outputs trigger signals to the first, second, and third vision cameras and the schlieren camera to ensure that each camera synchronously records the model separation process. Each camera captures the complete movement process of the separated model. The capture results of each camera at typical moments are as Figure 7 shown.

[0068] 5) Extract the pixel coordinates of the corresponding identification points in the three images captured by the multi-view vision system at each moment, and identify the true coordinates of the identification points in the world coordinate system according to the multi-view vision principle. Process all the identification points in sequence to obtain the coordinate values of all the identification points, and calculate the motion trajectory and attitude angles (angle of attack, sideslip angle) of the model centroid in combination with the geometric characteristics of the model shape. Typical results are as Figure 8 shown.

[0069] 6) Process the results captured by the schlieren camera, and use the edge detection method to determine the edge of the model, as Figure 9 shown. Determine the projection angle of the model according to the model edge coordinate values and the geometric characteristics of the model shape.

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

[0071] As Figure 1 shown, the optical axes between the first vision camera 1 and the second vision camera 2 and the first concave mirror 7 and the second concave mirror 8 form a fixed angle, and the first vision camera 1 and the second vision 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 only exemplary embodiments of the present application and are not used to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements within the essence and protection scope of the present application, and such modifications or equivalent replacements should also be regarded as falling within the protection scope of the present application.

Claims

1. A self-checking measurement system for the separation characteristics of hypersonic wind tunnel components, characterized in that Comprising: A multi-view vision system having three perspectives for collecting image information from the upper window and two side windows of the wind tunnel test section respectively. A schlieren system, wherein the light emitted by the light source of the schlieren system enters vertically through the two side windows of the wind tunnel test section through the optical components of the schlieren system, and after being reflected by the optical components, is received by the imaging components of the schlieren system to collect image information. 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 motion characteristics of the separation component.

2. A self-verifying measurement system for the separation characteristics of hypersonic wind tunnel components according to claim 1, wherein 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 outside 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. The third vision camera is arranged above the outside of the wind tunnel test section, and its acquisition end faces the inside of the test section from the top window of the wind tunnel test section.

3. A self-verifying measurement system for the separation characteristics of hypersonic wind tunnel components according to claim 2, wherein The schlieren system includes a first concave mirror and a second concave mirror, which are respectively arranged outside both sides of the wind tunnel test section. The schlieren system further includes a first plane mirror and a second plane mirror. The first plane mirror is arranged outside the wind tunnel test section deviating from the first concave mirror, and the second plane mirror is arranged outside the wind tunnel test section deviating from the second concave mirror. Among them, the first plane mirror, the first concave mirror, the second concave mirror and the second plane mirror constitute the optical components 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 components of the schlieren system.

4. A self-verifying measurement system for the separation characteristics of hypersonic wind tunnel components according to claim 3, wherein The schlieren system further includes a light shield, which is arranged close to the first plane mirror and is located at the focal plane position of the first concave mirror, and the light shield has a light-transmitting slit. On the other side of the light shield, there is a lamp group, and the light generated by the lamp group passes through the slit on the light shield and then enters the first plane mirror. Wherein, the lamp group and the light shield constitute the light source of the schlieren system.

5. A self-verifying measurement system for the separation characteristics of hypersonic wind tunnel components according to claim 4, wherein The schlieren system further includes a schlieren imaging camera, which is arranged close to the second plane mirror and is located at the focal plane position of the second concave mirror. The schlieren imaging camera is the imaging component of the schlieren system to receive the light reflected by the second plane mirror.

6. The self-checking measurement system for the separation characteristics of hypersonic wind tunnel components according to claim 3, characterized in that the first vision camera and the second vision camera form a fixed angle with the optical axes between the first concave mirror and the second concave mirror, and the first vision camera and the second vision 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.

Images