A method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel

Abstract

A method for measuring the deployment angle of a folding rudder for a high-speed wind tunnel belongs to the field of high-speed aerodynamic technology. The present invention includes S1, system construction, selecting the camera installation position according to the actual measurement requirements and the test section window; S2, optical path adjustment, determining the laser installation position, so that the laser plane is vertically irradiated on the model to be measured area; S3, camera parameter calibration, through the chessboard calibration plate to different positions in the space, obtain different homography matrices H, and estimate the internal and external parameters of the camera through different homography matrices combined with the iterative optimization technology of Zhang Zhengyou calibration method; S4, obtain the laser plane equation; S5, calibration parameter calculation; S6, rudder surface deployment angle measurement, the research and development purpose of the present invention is to solve the problem of complex system in the existing stereoscopic vision photogrammetry technology, the present invention is suitable for the deployment angle measurement of any wind tunnel folding rudder model under a high-speed wind tunnel, and an accurate rudder surface deployment angle can be obtained during the test.

Description

Technical Field

[0001] The invention relates to a method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel, belonging to the technical field of high-speed aerodynamics. Background Art

[0002] High-speed aircraft are the main strategic development direction of future aircraft due to their speed advantage. Their working capabilities will cover a wide speed range and a large airspace range. In order to meet the requirements of modern military operations for maneuverability and adaptability of launch platforms, folding rudders have gradually become a new design trend. Whether the folding rudder can be smoothly deployed is related to the stability and safety of the missile, and is the decisive factor in the success or failure of the missile flight. Therefore, dynamic measurement of the deployment angle of the folding rudder in a hypersonic wind tunnel plays an important role in establishing an understanding of the aerodynamic characteristics of the folding rudder deployment process, improving wind tunnel test capabilities, and supporting missile design and development.

[0003] Missiles generally have four rudders, and the deployment angle of the folding rudder is usually large, ranging from 100° to 160°. The use of a disc encoder usually requires sufficient space to be reserved in the missile body and a special structural design. However, the conventional stereoscopic optical photogrammetry method has a large angle range, which causes problems such as excessive tilt of the field of view and parallelism of the line of sight with the rudder during the deployment of the rudder angle. In addition, at least one system (two cameras) is used for monitoring one rudder surface. This means that if you want to fully measure the four folding rudders, you need to use at least eight cameras for photogrammetry, which makes the existing stereoscopic photogrammetry technology complicated.

[0004] Therefore, it is urgent to propose a method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of complicated systems in the existing stereoscopic vision photogrammetry technology. The present invention proposes a method for measuring the deployment angle of a folding rudder for a high-speed wind tunnel. The present invention is suitable for measuring the deployment angle of any wind tunnel folding rudder model in a high-speed wind tunnel. During the test, an accurate deployment angle of the rudder surface can be obtained. A brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0006] The technical solution of the present invention:

[0007] A method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel, comprising:

[0008] S1. System construction: select the camera installation position according to the actual measurement requirements and the test section window, and select the camera layout position according to the folding and unfolding state of the folding rudder. The camera orientation is the same as the orientation when the rudder is folded;

[0009] S2. Adjust the optical path and determine the installation position of the laser so that the laser plane can vertically illuminate the model test area. Arrange a straight line laser on the same side of the camera so that the laser plane can vertically illuminate the model test area, forming a clear and bright laser line on the model rudder surface.

[0010] S3, camera parameter calibration, by placing a checkerboard calibration plate at different positions in the space, obtain different homography matrices H, and estimate the internal and external parameters of the camera through different homography matrices combined with the iterative optimization technology of Zhang Zhengyou calibration method;

[0011] S4, obtaining the laser plane equation, fixing the checkerboard calibration plate, turning off the straight line laser, turning on the white light source in the test section, taking an image of the calibration plate, keeping the calibration plate still, turning on the straight line laser, turning off the white light source in the test section, taking the corresponding calibration plate image with the laser projection line as a set of calibration images, collecting at least three sets of calibration images with the calibration plate at different positions, calculating the plane equation of the calibration plate, and further obtaining the plane equation of the laser plane in the camera coordinate system;

[0012] S5, calibration parameter calculation, turn off the white light source of the test section, turn on the straight line laser, collect laser line images of the model surface in corresponding states when the rudder is fully folded and fully unfolded, and convert each point on the laser line in the image into the corresponding spatial straight line in combination with the camera matrix. Substitute it into the laser plane equation in step S4, and the three-dimensional coordinates of each point on the laser line in the camera matrix image in the camera coordinate system can be obtained, and then the spatial coordinate set of the projection line of the laser line on the model surface can be obtained.

[0013] Then, the calibration coefficient between the image solution angle and the design angle is calculated based on the spatial coordinates and design angle of the laser line in the folded and unfolded state. , realize laser line image reconstruction;

[0014] S6, Measure the rudder surface deployment angle. Turn off the white light source in the test section, turn on the straight line laser, and start the hypersonic wind tunnel blowing test. After the flow field is judged to be stable, the system receives an external trigger signal to start image acquisition, and obtains the image of the laser plane projected on the rudder surface during the whole process of the folding rudder surface deployment. Through image processing and three-dimensional reconstruction, the spatial coordinates corresponding to the laser line on the rudder surface in each time series are obtained. , the corresponding straight line direction vector is obtained by fitting , calculate its Image resolution angle , according to the calibration coefficient obtained in step S5 , calculate the actual angle of the rudder at the current moment:

[0015] Formula (1)

[0016] Thus, the time series of all angles during the full deployment of the folding rudder is obtained.

[0017] Preferably, when selecting the camera arrangement position in step S1, if there is no optical window on the side corresponding to the test section, the camera is arranged inside the test section by means of a camera protection device.

[0018] Preferably: the camera protection device includes a protection cabin, optical glass, a front cover plate of the protection device, a clamping bracket and an L-shaped block, the L-shaped block is fixedly installed inside the test section, the protection cabin is placed on the L-shaped block, a front cover plate of the protection device is arranged on the front side of the protection cabin, the optical glass is arranged on the front cover plate of the protection device, a clamping bracket is arranged inside the protection cabin, and the camera is fixedly mounted inside the protection cabin by the clamping bracket.

[0019] Preferably, the rear side of the protection cabin is processed with a protection cabin air inlet, a protection cabin air outlet and a protection cabin threading hole.

[0020] Preferably, when determining the laser installation position in step S2, if the laser line cannot irradiate the measurement area through the optical window, the laser is placed in a straight line laser protection device installed inside the test section.

[0021] Preferably, the line laser protection device comprises a line laser protection cabin, wherein a front cover plate and a rear cover plate are respectively arranged on the front and rear sides of the line laser protection cabin, an optical glass window is arranged on the front cover plate, and threading and ventilation holes are processed on the rear cover plate.

[0022] Preferably: the step S3 comprises:

[0023] S3.1. Turn off the straight line laser, place the checkerboard calibration plate at different positions in the space where the model is located, and take images of it to ensure that the calibration plate is at different positions and postures within the camera's field of view;

[0024] S3.2. For each image captured, use the corner detection algorithm (Harris corner detection) to extract the corner points of the chessboard;

[0025] S3.3. Using the extracted corner image coordinates and known world coordinates , the homography matrix H from the calibration plate plane to the image plane is calculated by combining the formula with the linear solution method, as follows:

[0026] =H Formula (2)

[0027] H= Formula (3)

[0028] Each image of the calibration plate corresponds to a homography matrix H, and each homography matrix H is decomposed into , K is the camera internal parameter, R and T are the rotation matrix and translation vector from the world coordinate system to the camera coordinate system, R= ;

[0029] S3.4. For all homography matrices H, the camera internal parameters are consistent, but R and T will change due to different positions of the calibration plate. Specifically, K is estimated by the iterative optimization technique in Zhang Zhengyou's calibration method, as shown in the following formula:

[0030] Formula (4)

[0031] in is the focal length of the camera, is the radial distortion parameter, As the main label.

[0032] Preferably, the step of calculating the plane equation of the calibration plate and the plane equation of the laser plane in the camera coordinate system in step S4 includes:

[0033] S4.1. Assume that the plane equation of the calibration plate is as follows:

[0034] + =0 Formula (5)

[0035] In the camera coordinate system, the normal vector of the calibration plate is the third column of R , according to the known homography matrix H and the solved intrinsic parameter K, the following formula can be obtained:

[0036] = Formula (6)

[0037] because , Must be orthogonal, so we can get the following formula:

[0038] = ;

[0039] in represents the vector cross product, and , are all unit vectors;

[0040] S4.2. In the camera coordinate system, the normal vector of the calibration plate plane is the third column of R. , so the plane equation of the calibration plate can be obtained as follows:

[0041] = ;

[0042] =- Formula (7)

[0043] S4.3. Each calibration plate position will intersect with the line laser plane to form a laser line. The image coordinates of the laser line on the current calibration plate are extracted through the line center detection algorithm. According to the camera model, we know that the pixel coordinates of any point on the image correspond to a straight line, so the image coordinates of any point on the laser line are expressed as:

[0044] Formula (8)

[0045] in, , =K[R|t], K represents the camera internal parameter, from which the straight line equation of any point on the laser line is obtained, which intersects with the corresponding calibration plate plane, and At the same time, the plane equation is satisfied, so the spatial coordinates of the points on the laser line under different calibration plate postures can be obtained, and the plane equation of the laser plane in the camera coordinate system can be estimated as follows:

[0046] Formula (9).

[0047] Preferably, in step S5, the laser line image is three-dimensionally reconstructed, and the image coordinates of the center of the laser line are extracted by image processing. ;

[0048] Get the image point coordinates according to the camera matrix The corresponding space straight line is substituted into the formula in S4 to obtain the coordinates of the image point The corresponding spatial point coordinates in the camera coordinate system , and then obtain the spatial coordinate set of the projection line of the laser line on the model surface;

[0049] Thus, the spatial coordinates of the laser line on the rudder when the rudder surface is fully folded are obtained and the spatial coordinates of the laser line on the rudder when fully deployed ,in Indicates the first Laser line imaging corresponding to each rudder surface;

[0050] Extract the laser line coordinates when the two control surfaces are fully deployed , , calculate the angle bisector vector of the plane constructed by the two laser lines at this time , so that the angle bisector vector in the plane The straight line is the bisector of the angle between the two laser lines;

[0051] Fitting laser line space coordinates and The corresponding straight line direction vector and , calculate its Image resolution angle and , the design angles of the rudder surface in the folded state and the fully extended state are known and , obtained by straight line fitting Calibration coefficient between the design angle of the control surface and the image solution angle , satisfying the following formula:

[0052] Formula (10)

[0053] Formula (11)

[0054] The present invention has the following beneficial effects:

[0055] 1. In the field of high-speed wind tunnel test, the present invention proposes a method for accurately measuring the angle of the folding rudder during the deployment process based on the principle of laser triangulation, thereby realizing accurate measurement of the deployment angle of the folding rudder;

[0056] 2. The present invention solves the problem of large angle calculation errors caused by conventional stereoscopic optical photogrammetry, which has a large angle range and may lead to excessive tilt of the field of view, parallelism of the line of sight with the rudder surface, etc. during the rudder angle deployment process;

[0057] 3. The present invention simplifies and optimizes the system layout, effectively reduces the space occupied by the equipment, and can be widely used in the deployment angle measurement of various deployment rudders in high-speed wind tunnel tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of the use state of the present invention;

[0059] Figure 2 It is a schematic diagram of a laser protection device for a word line of the present invention;

[0060] Figure 3 is a schematic diagram of a camera protection device of the present invention;

[0061] Figure 4 A schematic diagram of the angle bisector in the plane constructed by the laser line construction of the present invention;

[0062] In the figure, 1-camera, 2-schematic diagram of images collected by the camera, 3-line laser, 4-laser plane, 5-left rudder in fully extended state, 6-left rudder in fully folded state, 7-right rudder in fully folded state, 8-right rudder in fully extended state, 11-line laser protection cabin, 12-front cover, 13-rear cover, 14-optical glass window, 15-protection cabin, 16-optical glass, 17-front cover of protection device, 18-position bracket, 19-L-shaped block, 21-air inlet of protection cabin, 22-air outlet of protection cabin, 23-wire threading hole of protection cabin. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0064] The connection mentioned in the present invention is divided into fixed connection and detachable connection. The fixed connection (i.e., non-detachable connection) includes but is not limited to conventional fixed connection methods such as folding connection, rivet connection, bonding connection and welding connection. The detachable connection includes but is not limited to conventional detachable methods such as threaded connection, snap connection, pin connection and hinge connection. When the specific connection method is not clearly defined, it is assumed that at least one connection method can always be found in the existing connection methods to achieve the function. Those skilled in the art can choose according to their needs. For example: welding connection is selected for fixed connection, and hinge connection is selected for detachable connection.

[0065] Embodiment 1: Combination Figure 1-Figure 4 The present embodiment is described. A method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel comprises:

[0066] S1. System construction: Select the installation position of camera 1 according to the actual measurement requirements and the test section window. Select the layout position of camera 1 according to the folding and unfolding state of the folding rudder. The orientation of camera 1 is the same as that of the rudder when it is folded.

[0067] If the folding rudder is located on the left and right sides of the model, the camera is placed on the left and right sides of the test section, and the camera and the model are at the same height to view the rudder area of ​​the model from the side; if the folding rudder is located on the upper and lower sides of the model, the camera is placed on the upper and lower sides of the test section, and the camera is located directly below and above the model to view the rudder area of ​​the model from the side.

[0068] If there is an optical window at the central axis of the side corresponding to the test section, the camera can be considered to be arranged outside the optical window.

[0069] The folding rudder includes a rudder surface, which is divided into a left rudder surface and a right rudder surface. Figure 1 As shown, when the rudder surfaces of the model of the folding rudder are in the folded and unfolded state, the left rudder surface 6 in the fully folded state and the right rudder surface 7 in the fully folded state are unfolded into the left rudder surface 5 in the fully unfolded state and the right rudder surface 8 in the fully unfolded state respectively.

[0070] The camera 1 collects images of the control surface from the fully extended state to the fully closed state, that is, Figure 1 The image captured by the camera shown Figure 2 , it can be clearly seen that the laser plane generated by the line laser irradiates the laser line on the rudder surface. The line laser 3 emits a laser plane to irradiate the test rudder surface.

[0071] S2. Adjust the optical path and determine the installation position of the laser so that the laser plane can vertically illuminate the model test area. Arrange a straight line laser 3 on the same side of the camera 1 so that the laser plane 4 can vertically illuminate the model test area, forming a clear and bright laser line on the model rudder surface. If necessary, white matte paint can be sprayed on the model rudder surface to enhance the reflection brightness of the laser line.

[0072] S3, calibration of camera 1 parameters, by placing a checkerboard calibration plate at different positions in the space, obtaining different homography matrices H, and estimating the internal and external parameters of camera 1 by combining different homography matrices with the iterative optimization technology of Zhang Zhengyou calibration method;

[0073] S4, obtain the laser plane equation, fix the checkerboard calibration plate, turn off the straight line laser 3, turn on the white light source in the test section, take an image of the calibration plate, keep the calibration plate still, turn on the straight line laser 3, turn off the white light source in the test section, and take the corresponding calibration plate image with the laser projection line as a set of calibration images. In this way, at least three sets of calibration images with the calibration plate at different positions are collected, and the plane equation of the calibration plate and the plane equation of the laser plane 4 in the coordinate system of the camera 1 are calculated;

[0074] S5, calibration parameter calculation, turn off the white light source of the test section, turn on the straight line laser 3, collect the laser line images of the model surface in the corresponding state when the rudder is fully folded and fully unfolded, and convert each point on the laser line in the camera matrix image into the corresponding spatial straight line. Substitute it into the laser plane equation in step S4, and the three-dimensional coordinates of each point on the laser line in the camera matrix image in the camera 1 coordinate system can be obtained, and then the spatial coordinate set of the projection line of the laser line on the model surface can be obtained. Then, the calibration coefficient between the image solution angle and the design angle is calculated through the spatial coordinates and design angle of the laser line in the folded and unfolded states. , realize laser line image reconstruction;

[0075] S6, measurement of the rudder surface deployment angle, closing the white light source of the test section, opening the straight line laser 3, starting the hypersonic wind tunnel blowing test, after the flow field is judged to be stable, the system receives an external trigger signal to start image acquisition, and obtains the image of the laser plane 4 projected on the rudder surface during the whole process of the folding rudder surface deployment, and obtains the spatial coordinates corresponding to the laser line on the rudder surface in each time series through image processing and three-dimensional reconstruction. , the corresponding straight line direction vector is obtained by fitting , calculate its Image resolution angle , according to the calibration coefficient obtained in step S5 , calculate the actual angle of the rudder at the current moment:

[0076] Formula (1)

[0077] Thus, the time series of all angles during the full deployment of the folding rudder is obtained.

[0078] This embodiment is based on a straight line laser and a high-speed camera, based on the principle of laser triangulation, and taking into account that the interior of the high-speed wind tunnel test section is a vacuum environment, in order to ensure the normal operation of the camera 1 and the straight line laser 3, a protection device for the camera 1 and the straight line laser 3 is designed to enable the system to work normally in a high-speed test environment and capture the laser line image on the rudder surface; the homography matrix is ​​obtained by calibrating the parameters of the camera 1, and the plane equation of the laser line is obtained in combination with the calibration plate, and the three-dimensional coordinates of the laser line are obtained in combination with the image coordinates of the laser line; the calibration parameters for angle calculation are constructed through accurate angle information in the fully expanded and fully closed states; finally, the calibration parameters and the measured three-dimensional coordinates of the laser line are combined to obtain the real-time and accurate rudder surface expansion angle.

[0079] When selecting the placement position of the camera 1 in step S1, if there is no optical window on the corresponding side of the test section, the camera 1 is placed inside the test section through the camera protection device. The posture of the camera 1 or the camera protection device, the aperture and focal length of the lens are adjusted so that the model to be tested area is located in the middle of the field of view of the camera 1 and is clearly imaged. Each camera 1 can measure two rudder surfaces at the same time.

[0080] The camera protection device includes a protection cabin 15, an optical glass 16, a protection device front cover 17, a clamping bracket 18 and an L-shaped block 19. The L-shaped block 19 is fixedly installed inside the test section. The protection cabin 15 is placed on the L-shaped block 19. The protection cabin 15 is provided with a protection device front cover 17 on the front side. The optical glass 16 is provided on the protection device front cover 17. The protection cabin 15 is provided with a clamping bracket 18. The camera 1 is fixedly clamped inside the protection cabin 15 by the clamping bracket 18 to fix the camera 1 and prevent the camera 1 from vibrating during the test. The L-shaped block is placed at the bottom of the camera protection device to adjust the position of the protection device, thereby adjusting the position of the camera 1.

[0081] The rear side of the protection cabin 15 is processed with a protection cabin air inlet 21, a protection cabin air outlet 22 and a protection cabin threading hole 23. The protection cabin air inlet 21 is used to connect the ventilation valve; the protection cabin air outlet 22 is used to insert the near-air valve; the protection cabin air inlet 21 and the protection cabin air outlet 22 realize the air flow inside the camera protection device, ensuring that the internal pressure is normal and plays a role in cooling the camera 1; the protection cabin threading hole 23 is used for threading the power cord, BNC cable, network cable, etc. of the camera 1;

[0082] When determining the laser installation position in step S2, if the laser line cannot irradiate the measurement area through the optical window, the line laser 3 is placed in a line laser protection device installed inside the test section.

[0083] The straight-line laser protection device comprises a straight-line laser protection cabin 11, and a front cover plate 12 and a rear cover plate 13 are respectively arranged on the front and rear sides of the straight-line laser protection cabin 11. An optical glass window 14 is arranged on the front cover plate 12 for transmitting the laser plane, and threading and ventilation holes are processed on the rear cover plate 13 for threading the laser line power line and ventilating with the external atmospheric pressure, so that the straight-line laser protection device is always in a normal atmospheric pressure environment during the test, so that the straight-line laser 3 can work normally.

[0084] The step S3 comprises:

[0085] S3.1, turn off the straight line laser 3, and place the checkerboard calibration plate at different positions in the space where the model is located, and take images thereof, so as to ensure that the calibration plate is at different positions and postures within the field of view of the camera 1;

[0086] S3.2, for each captured image, use a corner detection algorithm to extract the corner points of the chessboard;

[0087] S3.3. Using the extracted corner image coordinates and known world coordinates , the homography matrix H from the calibration plate plane to the image plane is calculated by combining formula (2) with the linear solution method, as follows:

[0088] =H Formula (2)

[0089] H= Formula (3)

[0090] Each image of the calibration plate corresponds to a homography matrix H, and each homography matrix H is decomposed into , K is the internal parameter of camera 1, R and T are the rotation matrix and translation vector from the world coordinate system to the camera 1 coordinate system, R= ;

[0091] S3.4. For all homography matrices H, the internal parameters of camera 1 are consistent, while R and T will change due to different positions of the calibration plate. Specifically, K is estimated by the iterative optimization technique in Zhang Zhengyou's calibration method, as shown in the following formula:

[0092] Formula (4)

[0093] in is the focal length of camera 1, is the radial distortion parameter, As the main label.

[0094] The step of calculating the plane equation of the calibration plate and the plane equation of the laser plane 4 in the camera 1 coordinate system in step S4 includes:

[0095] S4.1. Assume that the plane equation of the calibration plate is as follows:

[0096] + =0 Formula (5)

[0097] In the camera 1 coordinate system, the normal vector of the calibration plate is the third column of R , according to the known homography matrix H and the solved intrinsic parameter K, the following formula can be obtained:

[0098] = Formula (6)

[0099] because , Must be orthogonal, so we can get the following formula:

[0100] =

[0101] in represents the vector cross product, and , are all unit vectors;

[0102] S4.2. In the camera 1 coordinate system, the normal vector of the calibration plate plane is the third column of R. , so the plane equation of the calibration plate can be obtained as follows:

[0103] = ;

[0104] =- Formula (7)

[0105] S4.3. Each calibration plate position will intersect with the line laser plane 4 to form a laser line. The image coordinates of the laser line on the current calibration plate are extracted through the line center detection algorithm. According to the camera 1 model, we know that the pixel coordinates of any point on the image correspond to a straight line, so the image coordinates of any point on the laser line are expressed as:

[0106] Formula (8)

[0107] in, , =K[R|t], K represents the internal parameter of camera 1, from which the equation of the straight line at any point on the laser line is obtained, which intersects with the corresponding calibration plate plane, and At the same time, the plane equation is satisfied, so the spatial coordinates of the points on the laser line under different calibration plate postures can be obtained, and the plane equation of the laser plane 4 in the camera 1 coordinate system can be estimated as follows:

[0108] Formula (9).

[0109] In step S5, the laser line image is three-dimensionally reconstructed, and the image coordinates of the center of the laser line are extracted by image processing. ;

[0110] Get the image point coordinates according to the camera 1 matrix Substituting the corresponding space straight line into formula (9) in S4, we can obtain the coordinates of the image point The corresponding spatial point coordinates in the camera 1 coordinate system , and then obtain the spatial coordinate set of the projection line of the laser line on the model surface.

[0111] Thus, the spatial coordinates of the laser line on the rudder when the rudder surface is fully folded are obtained and the spatial coordinates of the laser line on the rudder when fully deployed ,in Indicates the first Laser line imaging corresponding to each rudder surface;

[0112] like Figure 4 As shown in the figure, the schematic diagram of the angle bisector in the plane constructed by the laser line is constructed, and the coordinates of the laser line when the two rudder surfaces are fully deployed are extracted. , , calculate the angle bisector vector of the plane constructed by the two laser lines at this time , so that the angle bisector vector in the plane The straight line is the bisector of the angle between the two laser lines;

[0113] Fitting laser line space coordinates and The corresponding straight line direction vector and , calculate its Image resolution angle and , the design angles of the rudder surface in the folded state and the fully extended state are known and , obtained by straight line fitting Calibration coefficient between the design angle of the control surface and the image solution angle , satisfying the following formula:

[0114] Formula (10)

[0115] Formula (11).

[0116] Embodiment 2: Combination Figure 1-Figure 4 This embodiment is described. A method for measuring the deployment angle of a folding rudder for a high-speed wind tunnel in this embodiment is implemented based on an electronic device. The electronic device includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, the method for measuring the deployment angle of a folding rudder for a high-speed wind tunnel described in the first embodiment is implemented. In addition, the electronic device can be a single-chip microcomputer including a central processing unit. Moreover, when the processor is used to execute the computer program stored in the memory, the method for measuring the deployment angle of a folding rudder for a high-speed wind tunnel described above is implemented.

[0117] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0118] The memory may mainly include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area may store data created according to the use of the mobile phone (such as audio data, a phone book, etc.), etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0119] Example 3: Combination Figure 1-Figure 4 To illustrate the present embodiment, a method for measuring the deployment angle of a folding rudder for a high-speed wind tunnel in the present embodiment is implemented based on a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for measuring the deployment angle of a folding rudder for a high-speed wind tunnel described in the first specific embodiment is implemented.

[0120] The computer-readable storage medium of this embodiment can be any form of storage medium that can be read by the processor of a computer device, including but not limited to non-volatile memory, volatile memory, ferroelectric memory, etc. The computer-readable storage medium stores a computer program. When the processor of the computer device reads and executes the computer program stored in the memory, the above-mentioned method steps for measuring the deployment angle of a folding rudder for a high-speed wind tunnel can be implemented.

[0121] The computer program includes computer program code, which may be in source code form, object code form, executable file or some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer readable medium may be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer readable media do not include electric carrier signals and telecommunication signals.

[0122] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel, characterized in that: include: S1. System construction: Select the installation position of the camera (1) according to the actual measurement requirements and the test section window, and select the layout position of the camera (1) according to the folding and unfolding state of the folding rudder. The orientation of the camera (1) is the same as the orientation when the rudder is folded; S2, adjusting the optical path, determining the installation position of the laser, so that the laser plane is vertically irradiated on the model to be tested area, and simultaneously arranging a line laser (3) on the same side of the camera (1), so that the laser plane (4) is vertically irradiated on the model to be tested area, forming a clear and bright laser line on the model rudder surface; S3, calibration of camera (1) parameters, by placing a checkerboard calibration plate at different positions in space, obtaining different homography matrices H, and estimating the internal and external parameters of camera (1) by combining different homography matrices with the iterative optimization technique of Zhang Zhengyou calibration method; S4, obtaining the laser plane equation, fixing the checkerboard calibration plate, turning off the straight line laser (3), turning on the white light source in the test section, taking an image of the calibration plate, keeping the calibration plate still, turning on the straight line laser (3), turning off the white light source in the test section, taking a corresponding image of the calibration plate with the laser projection line as a set of calibration images, collecting at least three sets of calibration images with the calibration plate at different positions, calculating the plane equation of the calibration plate, and obtaining the plane equation of the laser plane (4) in the camera (1) coordinate system; S5, calibration parameter calculation, turn off the white light source of the test section, turn on the straight line laser (3), collect laser line images of the model surface in the corresponding state when the rudder is fully folded and fully unfolded, and convert each point on the laser line in the camera matrix image into the corresponding spatial straight line. Substitute it into the laser plane equation in step S4 to obtain the three-dimensional coordinates of each point on the laser line in the camera matrix image in the camera (1) coordinate system, and then obtain the spatial coordinate set of the projection line of the laser line on the model surface. Then, the calibration coefficient between the image solution angle and the design angle is calculated based on the spatial coordinates and design angle of the laser line in the folded and unfolded states. , realize laser line image reconstruction; S6, measurement of the rudder surface deployment angle, closing the white light source of the test section, turning on the straight line laser (3), starting the hypersonic wind tunnel blowing test, and after the flow field is judged to be stable, the system receives an external trigger signal to start image acquisition, and obtains the image of the laser plane (4) projected on the rudder surface during the entire process of the folding rudder surface deployment. The spatial coordinates corresponding to the laser line on the rudder surface at each time series are obtained through image processing and three-dimensional reconstruction. , the corresponding straight line direction vector is obtained by fitting , calculate its Image resolution angle , according to the calibration coefficient obtained in step S5 , calculate the actual angle of the rudder at the current moment: Formula (1) Thus, the time series of all angles during the full deployment of the folding rudder is obtained.

2. A method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel according to claim 1, characterized in that: When selecting the placement position of the camera (1) in step S1, if there is no optical window on the corresponding side of the test section, the camera (1) is placed inside the test section by means of a camera protection device.

3. The method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel according to claim 2, characterized in that: The camera protection device comprises a protection cabin (15), an optical glass (16), a protection device front cover plate (17), a clamping bracket (18) and an L-shaped block (19); the L-shaped block (19) is fixedly mounted inside the test section; the protection cabin (15) is placed on the L-shaped block (19); a protection device front cover plate (17) is arranged on the front side of the protection cabin (15); the optical glass (16) is arranged on the protection device front cover plate (17); a clamping bracket (18) is arranged inside the protection cabin (15); and the camera (1) is fixedly clamped inside the protection cabin (15) by the clamping bracket (18).

4. The method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel according to claim 3, characterized in that: The rear side of the protection cabin (15) is processed with a protection cabin air inlet (21), a protection cabin air outlet (22) and a protection cabin threading hole (23).

5. The method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel according to claim 4, characterized in that: When determining the laser installation position in step S2, if the laser line cannot irradiate the measurement area through the optical window, the straight-line laser (3) is placed in a straight-line laser protection device installed inside the test section.

6. A method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel according to claim 5, characterized in that: The line laser protection device comprises a line laser protection cabin (11), wherein a front cover plate (12) and a rear cover plate (13) are respectively arranged on the front and rear sides of the line laser protection cabin (11), an optical glass window (14) is arranged on the front cover plate (12), and threading and ventilation holes are processed on the rear cover plate (13).

7. A method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel according to claim 6, characterized in that: The step S3 comprises: S3.

1. Turn off the straight line laser (3), place the checkerboard calibration plate at different positions in the space where the model is located, and take images of the plate to ensure that the calibration plate is at different positions and postures within the field of view of the camera (1); S3.2, for each captured image, use a corner detection algorithm to extract the corner points of the chessboard; S3.

3. Using the extracted corner image coordinates and known world coordinates , the homography matrix H from the calibration plate plane to the image plane is calculated by combining formula (2) with the linear solution method, as follows: =H Formula (2) H= Formula (3) Each image of the calibration plate corresponds to a homography matrix H, and each homography matrix H is decomposed into , K is the internal parameter of the camera (1), R and T are the rotation matrix and translation vector from the world coordinate system to the camera (1) coordinate system, R = ; S3.

4. For all homography matrices H, the internal parameters of the camera (1) are consistent, while R and T will change due to different positions of the calibration plate. Specifically, K is estimated using the iterative optimization technique in Zhang Zhengyou's calibration method, as shown in the following formula: Formula (4) in is the focal length of camera (1), is the radial distortion parameter, As the main label.

8. The method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel according to claim 7, characterized in that: The step of calculating the plane equation of the calibration plate and the plane equation of the laser plane (4) in the camera (1) coordinate system in step S4 comprises: S4.

1. Assume that the plane equation of the calibration plate is as follows: + =0 Formula (5) In the camera (1) coordinate system, the normal vector of the calibration plate is the third column of R , according to the known homography matrix H and the solved intrinsic parameter K, we get the following formula: = Formulas (6) because , Must be orthogonal, so we get the following formula: = ； in represents the vector cross product, and , are all unit vectors; S4.

2. In the camera (1) coordinate system, the normal vector of the calibration plate plane is the third column of R. , so the plane equation of the calibration plate is obtained as follows: = =- Formulas (7) S4.

3. Each calibration plate position will intersect with the line laser plane (4) to form a laser line. The image coordinates of the laser line on the current calibration plate are extracted through the line center detection algorithm. According to the camera (1) model, we know that the pixel coordinates of any point on the image correspond to a straight line, so the image coordinates of any point on the laser line are expressed as: Formulas (8) in, = K[R|t], where K represents the internal parameter of the camera (1), from which the equation of the straight line at any point on the laser line is obtained, which intersects the corresponding calibration plate plane, and At the same time, the plane equation is satisfied, thereby obtaining the spatial coordinates of the points on the laser line under different calibration plate postures, and thus estimating the plane equation of the laser plane (4) in the camera (1) coordinate system, as follows: Official(9).

9. The method for measuring the deployment angle of a folding rudder used in a high-speed wind tunnel according to claim 8, characterized in that: In step S5, the laser line image is three-dimensionally reconstructed, and the image coordinates of the center of the laser line are extracted by image processing. ; Get the image point coordinates according to the camera matrix Substituting the corresponding space straight line into formula (9) in S4, we can obtain the coordinates of the image point The corresponding spatial point coordinates in the camera (1) coordinate system , and then obtain the spatial coordinate set of the projection line of the laser line on the model surface; Thus, the spatial coordinates of the laser line on the rudder when the rudder surface is fully folded are obtained and the spatial coordinates of the laser line on the rudder when fully deployed ,in Indicates the first Laser line imaging corresponding to each rudder surface; Extract the laser line coordinates when the two control surfaces are fully deployed , , calculate the angle bisector vector of the plane constructed by the two laser lines at this time , so that the angle bisector vector in the plane The straight line is the bisector of the angle between the two laser lines; Fitting laser line space coordinates and The corresponding straight line direction vector and , calculate its Image resolution angle and , the design angles of the rudder in the folded state and the fully extended state are known and , obtained by straight line fitting The calibration coefficient between the design angle of the control surface and the image solution angle , satisfying the following formula: Formula (10): Official(11).

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