PIV multiple calibration device and method based on fine positioning board camera reset

Abstract

The present invention discloses a PIV multiple calibration device and method based on fine positioning plate camera resetting. The positioning module and the carrying module are both placed on the ground, the carrying module can be movably mounted on the positioning module, the positioning module is used to position the carrying module and the camera posture, the PIV shooting module is mounted on the carrying module, the object to be detected is set in front of the carrying module, and the camera in the PIV shooting module is used to shoot multiple areas to be tested of the object to be detected; the method includes installing the calibration device and the calibration plate at the area to be tested, the laser head emits laser slices to the calibration plate, adjusts the position of the camera and then performs calibration operation on the area to be tested, records the device position and camera posture, and uses the camera to complete the shooting of the object to be detected. The present invention fixes the relative position of the laser and the camera to ensure that no displacement occurs after calibration, facilitates subsequent shooting, and uses guide rails for camera multi-section shooting tasks, saving time and cost.

Description

Technical Field

[0001] The invention belongs to the field of ship special propeller model testing, and particularly relates to a PIV multiple calibration device and method based on fine positioning plate camera resetting. Background Art

[0002] Currently, domestic ship design primarily utilizes computers for numerical simulation and emulation in fluid dynamics (CFD), structural mechanics, and thermodynamics to optimize ship design and performance prediction. Model tests and actual ship testing are conducted in both laboratory and real-world environments to verify the accuracy of design and theoretical analysis. These tests primarily focus on testing and calibrating parameters such as thrust, cavitation coefficient, and torque during the experiment, while PIV equipment is rarely used to capture internal flow fields. As a transient, multi-point, contactless flow field testing technique, PIV technology is widely used to analyze the internal flow characteristics of complex components. The velocity data processed by PIV can be compared on a block-by-block basis with the flow field data obtained by CFD.

[0003] For example, when conducting thruster PIV experiments in a cavitation water tunnel, the thruster fairing is a transparent curved structure, which causes image distortion during PIV photography, affecting the subsequent velocity field extraction and calculation. In order to obtain the velocity fields of multiple areas within the thruster, multiple calibration operations are required during three-dimensional photography (including but not limited to two-camera and four-camera photography). Since calibration requires placing a calibration plate in the shooting area and then removing it after calibration, the water tunnel needs to be opened multiple times to drain water, remove and install barriers, and store water. This series of operations is time-consuming. In addition, such large-scale experimental sites are rare in China, the schedule is tight, the tracer particles are very expensive, and the water storage capacity of the water tunnel is large, resulting in a significant waste of water resources. Another example is some large wind tunnels. When conducting PIV experiments in wind tunnels, particles need to be released and then velocity field data is obtained through laser irradiation and camera photography. When releasing particles, an evaporator is required to generate high-temperature steam before the particles are released into the wind tunnel. This causes the wind tunnel to be at a high temperature for a short period of time after the photography experiment. If multiple three-dimensional photography experiments are required, it is necessary to wait for the equipment to cool down before calibration, and subsequent experiments require waiting for the evaporator to heat up again, which increases the cycle of the entire experimental process. Reducing the number of times the wind tunnel is opened can form a recycling of tracer particles, which is beneficial to environmental protection and reduces experimental costs. However, the existing technology lacks a PIV multiple calibration device based on fine positioning board camera reset. Summary of the Invention

[0004] In order to solve the problems existing in the background technology, the purpose of the present invention is to provide a PIV multiple calibration device and method based on fine positioning plate camera reset.

[0005] The technical solution adopted in the present invention is:

[0006] 1. A PIV multiple calibration device based on fine positioning board camera reset:

[0007] It is mainly composed of a carrying module, a positioning module and a PIV shooting module. The positioning module and the carrying module are both placed on the ground. The carrying module can be movably installed on the positioning module. The positioning module is used to position the calibration device. The PIV camera in the PIV shooting module is installed on the carrying module. The object to be detected is set in front of the carrying module, and the PIV camera in the PIV shooting module is used to shoot multiple areas to be tested of the object to be detected.

[0008] The carrying module includes an optical platform base, a laser support base, a fixed vertical plate, a camera fixing slide, a camera bracket, a laser connecting slider, a universal wheel, a calibration plate and a water tunnel shell; the optical platform base and the laser support base are fixedly connected, a rolling universal wheel is installed at the bottom end of the laser support base, the optical platform base is movably installed on the guide rail of the positioning module, two fixed vertical plates are symmetrically installed on the top of the optical platform base, the camera fixing rod is detachably connected between the two fixed vertical plates, a camera fixing slide is provided on the camera fixing rod for fixing the camera bracket, the camera bracket can be installed on the camera fixing rod movably along the extension direction of the camera fixing slide, the PIV camera is installed on the camera bracket, the laser connecting slider is movably connected to the laser support base, the water tunnel shell is placed on the ground, the object to be detected is set in the water tunnel shell, the calibration plate is set in the to-be-detected area of ​​the object to be detected, the laser head in the PIV shooting module is installed on the laser connecting slider, and the laser head is used to emit laser slices to the position where the calibration plate is located.

[0009] The positioning module includes a guide rail and a camera positioning plate; the guide rail is placed on the ground and is used to realize the bidirectional movement of the optical platform base. The camera positioning plate is detachably mounted on the side wall of the water tunnel shell, and the camera positioning plate is located between the lens of the PIV camera and the object to be detected. The camera positioning plate is used to locate the posture of the PIV camera.

[0010] The PIV shooting module includes a laser system and a PIV camera. Both the laser system and the PIV camera are connected to an external workstation. The laser head in the laser system is used to emit laser to the location of the calibration plate. The workstation is used to control the shooting parameters of the PIV camera and the laser parameters of the laser emitted by the laser system.

[0011] The camera bracket comprises a roll angle adjustment knob, a pitch angle adjustment knob, a yaw angle adjustment knob, a camera bracket base, a camera bracket locking knob and a camera bracket locking piece; the camera bracket base can be movably installed on the camera fixing rod along the extension direction of the camera fixing slide, the camera bracket locking piece is arranged between the camera bracket base and the camera fixing rod, the camera bracket locking piece is used to lock the position of the camera bracket base, the camera bracket base and the camera bracket locking piece are provided with a knob mounting through hole at the same position, one end of the camera bracket locking knob is passed through the camera bracket locking piece and the knob mounting through hole on the camera bracket base in sequence and then connected to the camera bracket locking piece, the roll angle adjustment knob, the pitch angle adjustment knob, the yaw angle adjustment knob and the PIV camera are all installed on the camera bracket base, the roll angle adjustment knob, the pitch angle adjustment knob and the yaw angle adjustment knob are used to adjust the roll angle, pitch angle and yaw angle of the PIV camera respectively.

[0012] The guide rails include two Y-axis guide rails, two X-axis guide rails and guide rail sliders; the X-axis guide rails and the Y-axis guide rails are all arranged horizontally, and the X-axis guide rails and the Y-axis guide rails are perpendicular to each other. The X-axis guide rail is arranged along the extension direction of the water tunnel shell, and the two Y-axis guide rails are arranged in parallel and spaced apart. Each X-axis guide rail can be installed between the two Y-axis guide rails so as to move forward and backward along the extension direction of the Y-axis guide rail. The optical platform base can be installed between the two X-axis guide rails so as to move forward and backward along the extension direction of the X-axis guide rails through the guide rail sliders, thereby realizing bidirectional movement of the optical platform base.

[0013] 2. A PIV multiple calibration method based on fine positioning board camera resetting includes the following steps:

[0014] Step S1: Install the entire device in front of a test area of ​​the object to be detected, and then install the calibration plate in the test area of ​​the water tunnel housing;

[0015] Step S2: Start the laser system. The laser head in the laser system emits laser slices to the location of the calibration plate. Adjust the position of the PIV camera so that the center of the field of view of each PIV camera coincides with the center of the calibration plate. Then, calibrate the area to be measured.

[0016] Step S3: After the calibration operation is completed, the camera positioning plate is moved between the PIV camera and the object to be detected, and the position of the device at this time is recorded using the guide rail, while the position of the PIV camera is obtained using the camera positioning plate;

[0017] Step S4: Next, move the calibration device to the next area to be tested of the object to be tested, and move the calibration plate so that the calibration plate is located in the current area to be tested. Repeat steps S2 to S3 until the device position and the PIV camera pose in all areas to be tested are recorded.

[0018] Step S5: Remove the camera positioning plate and adjust the device and PIV camera in different test areas according to the device position and PIV camera posture recorded in step S4 until the PIV camera is used to complete the shooting of the objects to be detected at all test area positions.

[0019] The step S2 is specifically as follows:

[0020] Step S2.1, start the laser system, and the laser head in the laser system emits laser light toward the location of the calibration plate;

[0021] Step S2.2: First, move the mounting module to the front of the area to be measured via the guide rail, adjust the position of the laser connection slider so that the laser light sheet emitted by the laser head and the calibration plate are on the same plane, and adjust the camera fixing rod so that the distance between the PIV camera and the laser light sheet is at least 450 mm, and the center of the field of view of each PIV camera coincides with the center position of the calibration plate.

[0022] In step S2, the calibration operation of the test area includes adjusting the roll angle, pitch angle and yaw angle of the PIV camera by adjusting the roll angle adjustment knob, the pitch angle adjustment knob and the yaw angle adjustment knob so that the center of the PIV camera shooting image is located within the calibration plate.

[0023] In step S3, the posture of the PIV camera includes the position of the PIV camera and the roll angle, pitch angle and yaw angle of the PIV camera.

[0024] The principles of the present invention are as follows:

[0025] Since the file obtained by the PIV test calibration operation is only valid for the absolute spatial position during calibration, the validity of the calibration file can be guaranteed by recording and restoring the position data of the fixed laser head and camera. Therefore, for experiments where the test calibration operation is cumbersome and time-consuming, calibration operations can be performed on multiple areas to be tested first. Subsequently, the calibration files of the corresponding areas can be reset to make them valid to correct and distance the images. This can be used to solve the problems of complex flow fields being difficult to calibrate or the cumbersome and time-consuming setting up of the experimental environment.

[0026] Since the calibration file obtained by the PIV test calibration operation is only valid for the absolute spatial position at the time of calibration, that is, the optical platform position and camera pose at that time, the world coordinate system, that is, the calibration plate coordinate system, is recorded by the position of the xy plane of the guide rail under the optical platform, and the camera coordinate system is recorded by the positioning information of the camera positioning plate. Subsequently, the absolute position is restored through this information, that is, the inverse solution of the rigid body transformation can obtain the validity of the calibration file and perform subsequent correction and distance assignment. When the rigid body transformation is inversely solved, the accuracy of the reset can be determined by the mechanical positioning method, that is, the position information of the xy plane of the guide rail under the optical platform and the visual feedback method, that is, the positioning information of the camera positioning plate in each camera lens. This method can also be called absolute pose reproduction.

[0027] The beneficial effects of the present invention are:

[0028] 1. The present invention proposes a PIV multiple calibration method based on fine positioning plate camera resetting and designs and organizes an implementable device. By recording the world coordinate system through the position of the guide rail xy plane, recording the camera coordinate system through the positioning information of the camera positioning plate, and inverse solution of the rigid body transformation, the absolute resetting of the equipment position and camera posture is achieved, ensuring the validity of the calibration file and facilitating subsequent continuous shooting tests.

[0029] 2. The present invention adopts a guide rail mechanism for the camera multi-section shooting task, which records the world coordinate system while ensuring accuracy and speeding up the overall experimental process, saving time and cost.

[0030] 3. The present invention designs a camera reset positioning plate based on the camera calibration principle, which can record the camera coordinate system and reset the camera posture, speeding up the overall calibration process and saving time and cost.

[0031] 4. For PIV experiments in complex flow fields and calibration tests with complicated test steps, the present invention greatly reduces the equipment preparation time added by traditional calibration with one shot per test, and greatly improves calibration efficiency and experimental speed.

[0032] 5. For the PIV experiment inside a complex flow field, since a sufficient amount of tracer particles needs to be placed during the experiment, the velocity field is calculated by shooting the reflected light after the particles are irradiated by the laser. After each individual calibration and shooting, water needs to be drained and recalibrated when shooting the next area. The repeated draining will lead to a waste of water resources and a large loss of test consumables. This test plan solves this problem well. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of a PIV multiple calibration device based on fine positioning plate camera reset according to the present invention;

[0034] Figure 2 This is a schematic diagram of the present invention regarding the up and down adjustment of the laser and the distance adjustment between the laser and the camera;

[0035] Figure 3 This is a schematic diagram of the camera bracket adjustment components of the present invention;

[0036] Figure 4 This is a schematic diagram of the camera cross center alignment during calibration;

[0037] Figure 5 This is a diagram showing the center of the laser slice hitting the center of the calibration plate when adjusting the laser;

[0038] Figure 6 A schematic diagram of the specific components of the guide rail adjustment bracket;

[0039] Figure 7 Schematic diagram of another PIV multiple calibration device based on fine positioning plate camera reset according to the present invention;

[0040] Figure 8 This is a schematic diagram of "block positioning, positioning within a block" when using the camera positioning board;

[0041] Figure 9 Schematic diagram of the camera position change during the entire experiment.

[0042] In the figure: 1-optical platform base; 2-laser support base; 3-fixed vertical plate; 4-camera fixing slide; 5-camera bracket; 6-laser connection slider; 7-universal wheel; 8-calibration plate; 9-water tunnel housing; 10-guide rail; 11-camera positioning plate; 12-PIV camera; 51-roll angle adjustment knob; 52-pitch angle adjustment knob; 53-yaw angle adjustment knob; 54-camera bracket base; 55-camera bracket locking knob; 56-camera bracket locking piece; 101-Y-axis guide rail; 102-X-axis guide rail; 103-guide rail slider. DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to specific implementation cases. The following implementation cases will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0044] like Figure 1 As shown, the device is mainly composed of a carrying module, a positioning module and a PIV shooting module. The positioning module and the carrying module are both placed on the ground. The carrying module can be movably mounted on the positioning module. The positioning module is used to position the calibration device. The PIV camera 12 in the PIV shooting module is mounted on the carrying module. The object to be detected is set in the water hole shell 9 of the carrying module. The PIV camera 12 in the PIV shooting module is used to shoot multiple areas to be tested of the object to be detected.

[0045] Combine Figure 1 、 Figure 2As shown, the mounting module includes an optical platform base 1, a laser support base 2, a fixed vertical plate 3, a camera fixing slide 4, a camera bracket 5, a laser connection slider 6, a universal wheel 7, a calibration plate 8 and a water tunnel housing 9; the optical platform base 1 and the laser support base 2 are fixedly connected by angle irons, and a rolling universal wheel 7 is installed at the bottom end of the laser support base 2. The optical platform base 1 is movably installed on the guide rail 10 of the positioning module. Two fixed vertical plates 3 are symmetrically installed on the top of the optical platform base 1. The camera fixing rod is detachably connected between the two fixed vertical plates 3. The camera fixing rod is detachably connected between the two fixed vertical plates 3. A camera fixing slot 4 for fixing the camera bracket 5 is provided on the fixed rod. The camera bracket 5 can be installed on the camera fixing rod so as to move forward and backward along the extension direction of the camera fixing slot 4. The PIV camera 12 is installed on the camera bracket 5. The laser connecting slider 6 can be connected to the laser support base 2 so as to move up and down. The water tunnel housing 9 is placed on the ground. The object to be detected is set in the water tunnel housing 9. The calibration plate 8 is set in the test area of ​​the object to be detected. The laser head in the PIV shooting module is installed on the laser connecting slider 6. The laser head is used to emit laser slices to the position where the calibration plate 8 is located.

[0046] like Figure 7 As shown, the positioning module includes a guide rail 10 and a camera positioning plate 11; the guide rail 10 is placed on the ground, and the guide rail 10 is used to realize the bidirectional movement of the optical platform base 1; the camera positioning plate 11 is detachably mounted on the side wall of the water tunnel housing 9, and the camera positioning plate 11 is located between the lens of the PIV camera 12 and the object to be detected, and the camera positioning plate 11 is used to position the PIV camera 12.

[0047] The PIV shooting module includes a laser system and a PIV camera 12. Both the laser system and the PIV camera 12 are connected to an external workstation. The laser head in the laser system is used to emit laser to the location of the calibration plate 8. The workstation is used to control the shooting parameters of the PIV camera 12 and the laser parameters of the laser emitted by the laser system.

[0048] The shooting parameters of the PIV camera 12 include shooting cycle, shooting interval and shooting frame size; the laser parameters include laser intensity, laser interval and laser deflection angle.

[0049] like Figure 3As shown, the camera bracket 5 includes a roll angle adjustment knob 51, a pitch angle adjustment knob 52, a yaw angle adjustment knob 53, a camera bracket base 54, a camera bracket locking knob 55 and a camera bracket locking member 56; the camera bracket base 54 can be mounted on the camera fixing rod movably forward and backward along the extension direction of the camera fixing slide 4, and the camera bracket locking member 56 is arranged between the camera bracket base 54 and the camera fixing rod. The camera bracket locking member 56 is used to lock the position of the camera bracket base 54. The camera bracket base 54 and the camera bracket locking member 56 are provided with a knob at the same position. The mounting through hole is used, and one end of the camera bracket locking knob 55 passes through the camera bracket locking piece 56 and the knob mounting through hole on the camera bracket base 54 in sequence and is connected to the camera bracket locking piece 56. The camera bracket base 54 is used to adjust the tightness of the camera bracket locking piece 56. The roll angle adjustment knob 51, the pitch angle adjustment knob 52, the yaw angle adjustment knob 53 and the PIV camera 12 are all installed on the camera bracket base 54. The roll angle adjustment knob 51, the pitch angle adjustment knob 52 and the yaw angle adjustment knob 53 are used to adjust the roll angle, pitch angle and yaw angle of the PIV camera 12 respectively.

[0050] like Figure 6 As shown, the guide rail 10 includes two Y-axis guide rails 101, two X-axis guide rails 102 and a guide rail slider 103; the X-axis guide rails 102 and the Y-axis guide rail 101 are all arranged horizontally, and the X-axis guide rail 102 and the Y-axis guide rail 101 are perpendicular to each other, the X-axis guide rail 102 is arranged along the extension direction of the water tunnel housing 9, and the two Y-axis guide rails 102 are arranged in parallel and spaced apart, and each X-axis guide rail 102 can be installed between the two Y-axis guide rails 102 by means of a guide rail slider 103 so as to be movable forward and backward along the extension direction of the Y-axis guide rail 102. The optical platform base 1 can be installed between the two X-axis guide rails 102 by means of the guide rail slider 103 so as to be movable forward and backward along the extension direction of the X-axis guide rail 102, thereby realizing bidirectional movement of the optical platform base 1.

[0051] The embodiment of the present invention includes the following steps: Figure 9 As shown:

[0052] Step S1, installing the device at a test area of ​​the object to be detected, draining the water in the water tunnel, opening the cover of the water tunnel housing 9 at the test area, and then installing the calibration plate 8 in the test area of ​​the water tunnel housing 9;

[0053] Specifically, the calibration plate 8 is vertically arranged and located in the exact center of the area to be measured;

[0054] Step S2: Start the laser system. The laser head in the laser system emits laser slices to the location of the calibration plate 8. Adjust the position of the PIV camera 12 so that the center of the field of view of each PIV camera 12 coincides with the center of the calibration plate 8. Then, perform calibration on the area to be measured.

[0055] The calibration operation is a conventional operation, which is to achieve the correspondence between the physical spatial positions of different points on the calibration plate 8 and the spatial positions captured by the PIV camera, thereby correcting the captured images;

[0056] Step S3: After the calibration operation is completed, the camera positioning plate 11 is moved between the PIV camera 12 and the object to be detected, and the position of the device at this time is recorded using the guide rail, while the position of the PIV camera 12 is obtained using the camera positioning plate 11;

[0057] Specifically, the position of the guide rail at this time is recorded as the position during camera calibration. During subsequent shooting and moving of the mounting module, the relative position of the camera and the laser, the position of the camera itself, and the camera's pitch angle, roll angle, and horizontal angle must remain unchanged.

[0058] Step S4: Next, move the calibration device to the next area to be tested of the object to be tested, and move the calibration plate 8 so that the calibration plate 8 is located in the current area to be tested. Repeat steps S2 to S3 until the device positions and the poses of the PIV camera 12 in all areas to be tested are recorded.

[0059] Step S5: Remove the camera positioning plate 11, and adjust the device and the PIV camera 12 in different areas to be tested according to the device position and the posture of the PIV camera 12 recorded in step S4, until the PIV camera 12 is used to complete the shooting of the object to be tested at all positions in the areas to be tested.

[0060] Specifically, after all the areas to be tested have been calibrated, the calibration plate 8 is taken out, the upper cover of the water tunnel shell 9 is covered, and water is stored for shooting. When shooting, pay attention to parameter adjustment, aperture size, laser intensity, camera cross-frame time and other parameters; first shoot the area to be tested that was calibrated for the last time, and then reset it through the guide rail and camera bracket based on the previously recorded device position and PIV camera 12 posture data, and then take double-frame images. Each area to be tested is performed in turn, and finally the fine flow field information inside the object to be detected is obtained based on the captured image processing.

[0061] After completing the double-frame image shooting of each working condition in one area to be tested, the position of the carrying module is adjusted by using the guide rail slider 103 so that the carrying module moves to the next area to be tested. The distance between the two areas to be tested can be obtained by recording and measuring the relative position between the two areas to be tested. The camera shooting picture is viewed on a computer. When the camera picture overlaps highly and is clear, multiple double-frame images of working conditions are shot.

[0062] Step S2 is specifically as follows:

[0063] Step S2.1, start the laser system, and the laser head in the laser system emits laser light toward the location of the calibration plate 8;

[0064] Step S2.2: First, move the carrying module to the front of the area to be measured through the guide rail 10, adjust the position of the laser connecting slider 6 so that the laser light sheet emitted by the laser head and the calibration plate 8 are on the same plane, and adjust the camera fixing rod so that the distance between the PIV camera 12 and the laser light sheet is at least 450 mm to ensure that the PIV camera 12 can focus to obtain a clear picture, and the center of the field of view of each PIV camera 12 coincides with the center position of the calibration plate 8.

[0065] In step S2, the calibration operation of the test area includes adjusting the roll angle, pitch angle and yaw angle of the PIV camera 12 by adjusting the roll angle adjustment knob 51, the pitch angle adjustment knob 52 and the yaw angle adjustment knob 53, so that the center of the image captured by the PIV camera 12 is located within the calibration plate 8.

[0066] In step S3 , the posture of the PIV camera 12 includes the position of the PIV camera 12 and the roll angle, pitch angle and yaw angle of the PIV camera 12 . The position of the device is obtained by the position of the mounting module relative to the guide rail 10 .

[0067] Specifically, the laser head mounted on the laser connecting slider 6 emits a laser that hits the middle of the bottom surface of the calibration plate 8. The laser light path is vertical and diffuses along the axial direction of the laser head. The center of the laser light intensity is located at the center of the calibration plate 8. Figure 5 As shown; at the same time, adjust the height of the PIV camera 12 so that the midline position of the upper PIV camera 12 and the lower PIV camera 12 is at the same height as the center of the calibration plate 8, and adjust the position of the two left and right fixed vertical plates 3 so that the distance between the lenses of the left and right two PIV cameras 12 is equal to the distance between the lenses of the upper and lower PIV cameras 12.

[0068] The specific method of calibrating the area to be measured is as follows:

[0069] First, use a strong flashlight to illuminate the front of the calibration plate 8 so that the white dots on the surface of the calibration plate 8 are clearly visible and there are no bubbles or missing parts; use the computer in the workstation to initialize the PIV camera 12 and enter the shooting interface;

[0070] The roll angle, pitch angle and yaw angle of the camera are adjusted respectively by the roll angle adjustment knob 51, the pitch angle adjustment knob 52 and the yaw angle adjustment knob 53 so that the center of the camera shooting image is located in the center square of the calibration plate 8. Figure 4As shown, manually adjust the lens focal length so that the triangle and square images in the camera image are clearly visible; and adjust the camera image pixel size to determine the size of the shooting area and pay attention to the fact that the maximum image acquisition rate is affected by the shooting pixel size; after ensuring that the shooting areas of the four cameras are of the same size, the images are clearly visible, and the center of the images is roughly in the same position, exit the shooting interface and enter the calibration interface. After selecting the corresponding model of the calibration plate 8, calibration can be performed when there is sufficient lighting and all points on the calibration plate are clearly visible.

[0071] The specific method for the camera positioning board 11 to obtain the position and posture of the PIV camera 12 is as follows:

[0072] The camera positioning plate 11 is designed for the water tunnel housing 9. When placing the camera positioning plate 11, align the left side of the camera positioning plate 11 with the left edge wall of the main window of the water tunnel housing 9, and align the bottom surface of the camera positioning plate 11 with the lower edge wall of the main window of the water tunnel housing 9. If there is a gap, use blocks or other supporting components to place them on the upper and right sides of the camera positioning plate 11 to clamp the camera positioning plate 11 to the lower left corner to ensure that the camera positioning plate 11 is placed in the correct position each time. Figure 8 As shown, millimeter-level scales are drawn on the surface of the camera positioning plate 11 in the horizontal and vertical directions, circular marks are drawn periodically within the height and width of a certain position, and triangular marks are drawn at the center position defined by the four circular marks. The purpose of the marking is to divide the entire camera positioning plate 11 into different blocks of a certain size. Specific positioning can be achieved more conveniently and quickly through "block positioning and intra-block positioning". The block positioning in "block positioning and intra-block positioning" is to locate the position of the small block where the center of the cross cursor in the camera shooting screen is located in the entire camera positioning plate 11, and the small block is the area surrounded by four circular marks; the intra-block positioning is the specific position of the center of the cross cursor in the camera shooting screen at the small block, and the reference object is a millimeter-level straight line at this time; the purpose of the camera positioning plate 11 is to record the camera posture by marking the center position of the camera cross in the camera shooting area, and then reset the camera posture by adjusting the position of the camera center line. After each calibration operation is completed, the camera positioning plate is placed on the lower left corner of the wall of the water tunnel shell 9 and clamped to perform "block positioning, positioning within the block", and is removed after recording; after each shooting, the camera positioning plate is placed on the wall of the water tunnel shell 9 after the guide rail position is reset through the guide rail, and the camera positioning plate 11 is removed after resetting the camera position.

[0073] The optical platform base 1 and universal wheels 7 of the present invention primarily support the entire device and ensure that the laser head follows the overall movement of the PIV camera. The fixed riser 3, camera mounting slot 4, and camera bracket 5 enable the camera's spatial position and shooting posture on the optical platform base 1 to be adjusted to meet shooting requirements. The laser connecting slider 6 includes fastening components that enable the vertical movement and fixation of the laser head connected to the laser connecting slider 6. The camera mounting slot 4 adjusts the distance between the laser head, i.e., the laser section, and the PIV camera by adjusting the distance between the PIV camera and the laser section. The calibration plate 8 is a PIV test standard component used for calibrating the test area during PIV three-dimensional testing. The water tunnel housing 9 simulates the water tunnel experimental environment, demonstrating the complexity of shooting and verifying the tedious operations associated with environmental shooting. The guide rails 10 include an X-axis guide rail and a Y-axis guide rail. The X-axis guide rail adjusts the left and right movement of the entire device. The Y-axis guide rail is fixed to the ground and adjusts the X-axis guide rail and the entire device for forward and backward movement. The PIV camera 12 is mounted on a camera bracket and takes dual-frame images of the PIV tracer particles in the test area through the wall of the water tunnel housing 9. The laser system generates laser slices to illuminate the PIV tracer particles in the test area. The workstation transmits data to the PIV camera and laser system respectively, and is used to adjust the laser intensity, receive camera images, and perform PIV experiment calibration, photography, and other operations. Figure 8 As shown, the camera positioning plate 11 includes circular marks and triangular marks. The circular marks divide the entire camera positioning plate 11 into several small pieces, namely blocks. The area surrounded by the four nearest circular marks or the boundaries of the camera positioning plate 11 is positioned and marked for "block positioning" of the cross center position of the PIV camera; the triangular mark is the center position within each block, which is used to identify the block and indirectly provide a reference for "intra-block positioning" of the cross center position of the PIV camera.

[0074] The optical platform base 1 meets the technical requirements in terms of material density, tensile strength, compressive strength, and processing and forming. The material used in the present invention is GB 6262 national standard aluminum profile, which meets the above requirements during the test. The fixed vertical plate 3 meets the technical requirements in terms of material density, tensile strength, compressive strength, and processing and forming. The material used in the experiment is GB 3838 national standard aluminum profile. The angle iron is a supporting fixture for the optical platform base 1. The purpose of the angle iron is to provide support for the connecting rods and ensure the stability of the bracket connection. The camera fixing slide 4 is a supporting device for the camera bracket, which can connect the camera base to the camera fixing rod. The camera bracket is connected to the camera fixing slide and can be moved along the direction of the camera fixing slide by adjusting the camera bracket locking knob. The distance between the camera and the laser slice can be adjusted by adjusting the locking position of the camera fixing slide. The camera bracket 5 is a three-degree-of-freedom camera bracket that can adjust the camera's yaw, pitch, and roll angles. When calibrating a PIV camera, the angles of these three rotating handles must be adjusted to meet calibration requirements. The camera bracket position remains unchanged, and calibration and subsequent resetting are all achieved through these three rotating handles to adjust the camera's posture. The laser connecting slider 6 is an auxiliary device for the laser head of the laser system. It needs to be able to securely fix the laser head. When installed, the laser light outlet faces upward, and a sheet of light is emitted vertically upward. The intensity is determined by debugging the specific scene. The universal wheel is an auxiliary moving means for the optical platform base. While providing support, it can also achieve translation of the optical platform base on the horizontal ground. There is also a locking device that can fix the optical platform in place for shooting experiments.

[0075] The calibration plate 8 is a standard component for PIV testing. Its function is to establish a coordinate mapping relationship from the object plane to the phase plane, which is used for image distortion correction and scale calibration. The center of the calibration plate is a square mark. During calibration, the center of the cross in the camera image overlaps with it. The calibration plate model parameter is located in the lower right corner when viewed from the front. When looking directly at the calibration plate, there are connection holes in all four directions: up, down, left, and right. The water tunnel housing 9 is designed to simulate the test constraints. When testing the internal equipment, the water tunnel must go through the following steps: draining water, removing the cover, removing the blocking member, calibrating the shooting area, assembling the blocking member, installing the cover, and finally filling it with water for shooting. Draining and filling water do not allow for good speed adjustment. The guide rail 10 is installed at the bottom of the entire device. The guide rail mainly consists of two sections. The guide rail can be switched between fixed and movable states by adjusting the knob on the guide rail. When the guide rail is installed, ensure that the X-axis movement direction is parallel to the axis of the object to be tested and the Y-axis direction is perpendicular to the X-axis direction. The X-axis movable rail can move along the entire bracket in the Y-axis direction.

[0076] The camera positioning plate is made of acrylic plate and is designed for the water tunnel shell to ensure that the camera positioning plate is placed in the same position each time. Millimeter-level scales are drawn on its surface in the horizontal and vertical directions, circular marks are drawn periodically within a certain length in the X and Y directions, and triangular marks are drawn at the center position defined by the four circular marks. The purpose of the marking is to divide the entire large plate into different blocks of a certain size. Specific positioning can be achieved through "block positioning, positioning within the block". Block positioning is to locate the position of the block surrounded by the four circular marks closest to the center of the cross cursor in the camera shooting screen in the entire camera positioning plate; positioning within the block is to achieve a more convenient and rapid positioning at the position where the center of the cross cursor in the camera shooting screen is located within the block. The purpose of the camera positioning plate is to mark the center of the camera cross in the camera shooting area. PIV software basically has a way to display the center of the camera chip. The software used in the present invention records the camera posture by displaying a red cross to indicate the middle position of the camera chip, and then resets the camera posture by adjusting the position of the camera cross center line.

[0077] The PIV camera 12 utilizes four CMOS cameras, enabling dual-camera and multi-camera experiments. A variety of camera arrangements are available, including two cameras arranged vertically, horizontally, or side-by-side, or four cameras arranged in a triangular pattern, an arc, or side-by-side. The cameras are positioned at least 450 mm from the imaging section to ensure focus. The left-right spacing of the cameras may vary depending on the actual situation and camera model. The centerline of the upper and lower cameras passes through the center of the imaging area to ensure consistent deflection angles. The laser system includes a laser generator, a laser polarizer, an optical arm, a laser head, and a water cooler. The optical arm length and path must be considered when moving the entire light source positioning experimental setup. The workstation is equipped with velocity processing software and PCC. The PCC software is used to establish a connection address for the cameras, while the velocity processing software is the primary software used, performing calibration, imaging, preprocessing, and data processing. The PIV imaging module meets the basic PIV experimental workflow. Most commercially available PIV systems include a calibration module and can perform targeted processing of distorted images. Laser adjustment includes adjusting the upper and lower positions of the laser to ensure that the laser can hit the calibration plate with the strongest light and the astigmatism is not seriously lost. The light intensity and the distance between the laser and the camera ensure that the camera can focus on the image and clearly see the area to be measured indicated by the laser section:

[0078] The laser is adjusted up and down using a GB 6262 aluminum profile, the same material as the optical platform base, and a GB 3838 aluminum profile, the same material as the fixed riser. The GB 3838 can be placed inside the GB 6262 with a 1mm gap on all sides and can slide and move. It also has fastening components. The laser head moves up and down by sliding and locking. The distance between the laser and the camera is achieved by adjusting the connection position between the camera fixing slot and the fixed riser. When adjusting, pay attention to the consistency of the distance between the upper and lower camera fixing slots and the laser slice.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A PIV multiple calibration device based on fine positioning plate camera reset, characterized by: The device is mainly composed of a carrying module, a positioning module and a PIV shooting module. The positioning module and the carrying module are both placed on the ground. The carrying module can be movably mounted on the positioning module. The positioning module is used to position the calibration device. A PIV camera (12) in the PIV shooting module is mounted on the carrying module. The object to be detected is set in front of the carrying module. The PIV camera (12) in the PIV shooting module is used to shoot multiple areas to be detected of the object to be detected. The mounting module comprises an optical platform base (1), a laser support base (2), a fixed vertical plate (3), a camera fixing slide (4), a camera bracket (5), a laser connection slider (6), a universal wheel (7), a calibration plate (8) and a water tunnel shell (9); the optical platform base (1) and the laser support base (2) are fixedly connected, a rollable universal wheel (7) is installed at the bottom end of the laser support base (2), the optical platform base (1) is movably installed on the guide rail (10) of the positioning module, two fixed vertical plates (3) are symmetrically installed on the top of the optical platform base (1), and the camera fixing rod is detachably connected between the two fixed vertical plates (3). A camera fixing slot (4) for fixing a camera bracket (5) is provided on the camera fixing rod, the camera bracket (5) can be mounted on the camera fixing rod so as to move forward and backward along the extension direction of the camera fixing slot (4), the PIV camera (12) is mounted on the camera bracket (5), the laser connection slider (6) can be connected to the laser support base (2) so as to move up and down, the water hole shell (9) is placed on the ground, the object to be detected is set in the water hole shell (9), the calibration plate (8) is set in the detection area of ​​the object to be detected, the laser head in the PIV shooting module is mounted on the laser connection slider (6), and the laser head is used to emit laser slices to the position where the calibration plate (8) is located; The positioning module includes a guide rail (10) and a camera positioning plate (11); the guide rail (10) is placed on the ground, and the guide rail (10) is used to realize the bidirectional movement of the optical platform base (1); the camera positioning plate (11) is detachably mounted on the side wall of the water tunnel shell (9), and the camera positioning plate (11) is located between the lens of the PIV camera (12) and the object to be detected, and the camera positioning plate (11) is used to position the posture of the PIV camera (12); The PIV multiple calibration device adopts the following PIV multiple calibration method: Step S1, installing the entire device in front of a test area of ​​the object to be detected, and then installing the calibration plate (8) in the test area in the water tunnel housing (9); Step S2, starting the laser system, the laser head in the laser system emits a laser slice to the position of the calibration plate (8), adjusting the position of the PIV camera (12) so that the center of the field of view of each PIV camera (12) coincides with the center position of the calibration plate (8), and then performing a calibration operation on the area to be measured; Step S3: After the calibration operation is completed, the camera positioning plate (11) is moved between the PIV camera (12) and the object to be detected, and the position of the device at this time is recorded using the guide rail, while the position of the PIV camera (12) is obtained using the camera positioning plate (11); Step S4, then, move the calibration device to the next test area of ​​the object to be detected, and move the position of the calibration plate (8) so that the calibration plate (8) is located in the current test area, and repeat steps S2 to S3 until the device positions and the postures of the PIV camera (12) in all test areas are recorded; Step S5: Remove the camera positioning plate (11), and adjust the device and the PIV camera (12) in different areas to be tested according to the device position and the posture of the PIV camera (12) recorded in step S4, until the PIV camera (12) is used to complete the shooting of the object to be tested at all positions in the areas to be tested.

2. The PIV multiple calibration device based on fine positioning plate camera reset according to claim 1, characterized in that: The PIV shooting module includes a laser system and a PIV camera (12), both of which are connected to an external workstation. The laser head in the laser system is used to emit laser light to the location of the calibration plate (8), and the workstation is used to control the shooting parameters of the PIV camera (12) and the laser parameters of the laser emitted by the laser system.

3. The PIV multiple calibration device based on fine positioning plate camera reset according to claim 1, characterized in that: The camera bracket (5) comprises a roll angle adjustment knob (51), a pitch angle adjustment knob (52), a yaw angle adjustment knob (53), a camera bracket base (54), a camera bracket locking knob (55) and a camera bracket locking member (56); the camera bracket base (54) can be mounted on the camera fixing rod so as to move forward and backward along the extension direction of the camera fixing slot (4); the camera bracket locking member (56) is arranged between the camera bracket base (54) and the camera fixing rod; the camera bracket locking member (56) is used to lock the position of the camera bracket base (54); the camera bracket base (54) and the camera bracket locking member (56) A knob mounting through hole is provided at the same position, and one end of the camera bracket locking knob (55) passes through the camera bracket locking member (56) and the knob mounting through hole on the camera bracket base (54) in sequence and is connected to the camera bracket locking member (56). The roll angle adjustment knob (51), the pitch angle adjustment knob (52), the yaw angle adjustment knob (53) and the PIV camera (12) are all installed on the camera bracket base (54). The roll angle adjustment knob (51), the pitch angle adjustment knob (52) and the yaw angle adjustment knob (53) are used to adjust the roll angle, pitch angle and yaw angle of the PIV camera (12) respectively.

4. The PIV multiple calibration device based on fine positioning plate camera reset according to claim 1, characterized in that: The guide rail (10) includes two Y-axis guide rails (101), two X-axis guide rails (102) and a guide rail slider (103); the X-axis guide rail (102) and the Y-axis guide rail (101) are both arranged horizontally, and the X-axis guide rail (102) and the Y-axis guide rail (101) are perpendicular to each other, the X-axis guide rail (102) is arranged along the extension direction of the water tunnel housing (9), the two Y-axis guide rails (101) are arranged in parallel and spaced apart, and each X-axis guide rail (102) can be installed between the two Y-axis guide rails (101) so as to move forward and backward along the extension direction of the Y-axis guide rail (101), and the optical platform base (1) can be installed between the two X-axis guide rails (102) so as to move forward and backward along the extension direction of the X-axis guide rail (102) through the guide rail slider (103), thereby realizing bidirectional movement of the optical platform base (1).

5. A PIV multiple calibration method based on fine positioning board camera resetting applied to the device according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step S1, installing the entire device in front of a test area of ​​the object to be detected, and then installing the calibration plate (8) in the test area in the water tunnel housing (9); Step S2, starting the laser system, the laser head in the laser system emits a laser slice to the position of the calibration plate (8), adjusting the position of the PIV camera (12) so that the center of the field of view of each PIV camera (12) coincides with the center position of the calibration plate (8), and then performing a calibration operation on the area to be measured; Step S3: After the calibration operation is completed, the camera positioning plate (11) is moved between the PIV camera (12) and the object to be detected, and the position of the device at this time is recorded using the guide rail, while the position of the PIV camera (12) is obtained using the camera positioning plate (11); Step S4, then, move the calibration device to the next test area of ​​the object to be detected, and move the position of the calibration plate (8) so that the calibration plate (8) is located in the current test area, and repeat steps S2 to S3 until the device positions and the postures of the PIV camera (12) in all test areas are recorded; Step S5: Remove the camera positioning plate (11), and adjust the device and the PIV camera (12) in different areas to be tested according to the device position and the posture of the PIV camera (12) recorded in step S4, until the PIV camera (12) is used to complete the shooting of the object to be tested at all positions in the areas to be tested.

6. The PIV multiple calibration method based on fine positioning plate camera resetting according to claim 5, characterized in that: The step S2 is specifically as follows: Step S2.1, start the laser system, and the laser head in the laser system emits laser light toward the location of the calibration plate (8); Step S2.2: First, move the mounting module to the front of the area to be measured via the guide rail (10), adjust the position of the laser connecting slider (6) so that the laser light sheet emitted by the laser head and the calibration plate (8) are on the same plane, and adjust the camera fixing rod so that the distance between the PIV camera (12) and the laser light sheet is at least 450 mm, and the center of the field of view of each PIV camera (12) coincides with the center position of the calibration plate (8).

7. The PIV multiple calibration method based on fine positioning plate camera resetting according to claim 5, characterized in that: In step S2, the calibration operation of the area to be measured includes adjusting the roll angle, pitch angle and yaw angle of the PIV camera (12) by adjusting the roll angle adjustment knob (51), the pitch angle adjustment knob (52) and the yaw angle adjustment knob (53), so that the center of the image captured by the PIV camera (12) is located within the calibration plate (8).

8. The PIV multiple calibration method based on fine positioning plate camera resetting according to claim 5, characterized in that: In step S3, the posture of the PIV camera (12) includes the position of the PIV camera (12) and the roll angle, pitch angle and yaw angle of the PIV camera (12).

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