Automatic particle image velocity measurement equipment and control method

Abstract

The invention provides automatic particle image velocity measurement equipment and a control method. The automatic particle image velocity measurement equipment comprises a three-axis lead screw open T-shaped sliding table, a four-axis lead screw closed gantry sliding table, a machine vision system, a PIV system, a controller and an automatic equipment control system, the machine vision system collects an image of the experimental model, the controller compares the image of the experimental model with a database, when the matching rate is larger than or equal to a preset percentage, feature matching is completed, a measurement result and a decision instruction are generated, and the automatic equipment control system controls the sliding table to move according to a given motion path. And meanwhile, the high-speed camera is controlled to trigger double-frame exposure according to given exposure parameters, and real-time cross-correlation analysis is carried out to obtain velocity field data, so that automatic PIV measurement is realized. According to the method, the problems of long time consumption, low efficiency and high operation repeatability caused by frequent manual calibration of PIV equipment in the experiment process are solved, a large amount of manpower and time cost is saved, and the research speed is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of particle image velocimetry, and in particular relates to an automated particle image velocimetry device and a control method. Background Art

[0002] Particle image velocimetry (PIV) is a transient, multi-point, non-contact method for measuring fluid velocity. It involves scattering tracer particles with good tracking and reflective properties in a flow field. Laser sheet light is then used to illuminate a cross-section of the flow field being measured. An imaging recording system captures two or more consecutive particle images. The captured PIV images are then analyzed using image cross-correlation techniques to determine the average displacement of the particle images within each small region, thereby determining the two-dimensional velocity distribution across the entire cross-section of the flow field.

[0003] Before conducting PIV measurements, it is necessary to accurately calibrate the camera and laser to ensure that the camera's focal plane completely coincides with the laser sheet light position to avoid image distortion, thereby achieving accurate conversion of pixel coordinates to physical coordinates. However, the measurement range of PIV is limited by the camera's field of view and the area illuminated by the laser sheet light. When measuring large-scale flow fields, it is usually necessary to synchronize multiple cameras and lasers, or use a group of cameras and lasers for frequent movement and precise calibration, which greatly increases the complexity and time cost of PIV testing. However, current research on improving the efficiency of PIV measurements of large-scale flow fields by scholars at home and abroad mainly focuses on high-quality hardware equipment, the performance of tracer particles, image processing algorithms, etc. There has been no in-depth research on the efficient calibration of cameras and lasers, and there is currently no relevant automated auxiliary equipment for quickly and accurately calibrating the relative positions of PIV cameras and lasers. Summary of the Invention

[0004] In response to the above technical problems, the present invention provides an automated particle image velocimetry device, which improves the measurement efficiency and measurement range of PIV, solves the problems of long time consumption, low efficiency, and high operation repeatability caused by the frequent manual calibration of PIV equipment during the experiment, and saves a lot of manpower and time costs.

[0005] Note that the inclusion of these objectives does not preclude the existence of other objectives. One embodiment of the present invention does not necessarily achieve all of the above objectives. Objectives other than the above objectives may be extracted from the description of the specification, drawings, and claims.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] An automated particle image velocimetry device, comprising a three-axis lead screw open T-type slide, a four-axis lead screw closed gantry slide, a machine vision system, a PIV system, a controller, and an automated equipment control system;

[0008] The machine vision system is arranged on one side of the experimental section, the three-axis screw open T-type slide is arranged on the other side of the experimental section, and the four-axis screw closed gantry slide is arranged below the experimental section; the three-axis screw open T-type slide and the four-axis screw closed gantry slide are respectively connected to the stepper motor, and the stepper motor is respectively connected to the stepper motor driver;

[0009] The PIV system includes a high-speed camera and a laser source; the high-speed camera is mounted on a three-axis screw open T-type slide, and the laser source is mounted on a four-axis screw closed gantry slide;

[0010] The automation equipment control system is connected to the stepper motor driver and the machine vision system respectively;

[0011] The controller is connected to the machine vision system, the PIV system and the automation equipment control system respectively;

[0012] The experimental section is used to place the experimental model; the machine vision system is used to collect images of the experimental model in the experimental section and transmit them to the controller. The controller compares the experimental model image with the database. When the matching rate is greater than or equal to a preset percentage, the feature matching is completed, and the measurement results and decision instructions are generated and transmitted to the automation equipment control system. The automation equipment control system controls the three-axis lead screw open T-type slide and the four-axis lead screw closed gantry slide to move according to the given motion path. The controller also controls the high-speed camera to trigger double-frame exposure according to the given exposure parameters, obtains the particle image of the flow around the experimental model, and performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

[0013] In the above solution, the machine vision system includes an illumination light source, a CMOS camera and an image acquisition card; the CMOS camera is connected to the controller via the image acquisition card.

[0014] Further, the controller includes an image processing unit and a particle image processing unit;

[0015] A database is provided in the image processing unit; the database includes a basic feature library, a flow field type library, a calibration feature library and a historical strategy library; the data type stored in the basic feature library is the three-dimensional point cloud or contour feature of the experimental model; the data type stored in the flow field type library is the flow field pattern feature vector; the data type stored in the calibration feature library is the calibration plate image template and distortion parameter, and the calibration feature library pre-stores reference images of calibration plates of different sizes and supports automatic distortion correction function; the historical strategy library stores motion path planning schemes of multiple successful experiments of three-axis screw open T-type slides and four-axis screw closed gantry slides, and the historical strategy library records the verified motion paths of the three-axis screw open T-type slides and four-axis screw closed gantry slides, as well as the exposure parameter combination of the high-speed camera, to support similar scene calls;

[0016] The particle image processing unit is used to perform real-time cross-correlation analysis on the particle images of the experimental model to obtain velocity field data.

[0017] Furthermore, the image processing unit is used to compare the experimental model image with the database, identify the basic features, flow field type and calibration features of the experimental model, and find the corresponding three-axis screw open T-type slide and four-axis screw closed gantry slide from the historical strategy library according to the basic features, flow field type and calibration features of the experimental model to obtain the motion path and exposure parameter combination of the high-speed camera, generate measurement results and decision instructions and transmit them to the automation equipment control system. The automation equipment control system controls the three-axis screw open T-type slide to perform an automatic calibration process. The high-speed camera on the three-axis screw open T-type slide calibrates and collects the calibration plate in the center of the measurement area and performs real-time distortion correction before transmitting the relevant data to the PIV system. The PIV system generates a coordinate mapping table. After the automatic calibration process is completed, the automation equipment control system controls the four-axis screw closed gantry slide to move according to the preset grid according to the measurement results and decision instructions. The controller controls the high-speed camera to synchronously trigger double-frame exposure to obtain particle images of the flow around the experimental model. The particle image processing unit performs real-time cross-correlation analysis to obtain corresponding velocity field data, thereby realizing automated PIV measurement.

[0018] In the above scheme, the experimental section is rectangular; the length of the experimental section is L, the width is D, and the height is H.

[0019] Furthermore, the X-axis stroke of the three-axis screw open T-type slide is set to L, the Z-axis stroke of the three-axis screw open T-type slide is set to H for all-round shooting of the flow field in the experimental section, and the Y-axis stroke of the three-axis screw open T-type slide is set to D for focusing of the high-speed camera.

[0020] Furthermore, the X-axis stroke of the four-axis screw closed gantry slide is set to D, the Y-axis stroke of the four-axis screw closed gantry slide is set to L for all-round laser irradiation of the flow field in the experimental section, and the Z-axis stroke of the four-axis screw closed gantry slide is set to L for lifting the laser source.

[0021] In the above solution, the automation equipment control system is provided with a touch screen.

[0022] A control method according to the automated particle image velocimetry device comprises the following steps:

[0023] The machine vision system is arranged on one side of the test section, the three-axis screw open T-type slide is arranged on the other side of the test section, and the four-axis screw closed gantry slide is arranged below the test section; the high-speed camera is installed on the three-axis screw open T-type slide, and the laser source is installed on the four-axis screw closed gantry slide; the experimental model is placed in the experimental section; the machine vision system collects the image of the experimental model in the experimental section and transmits it to the controller, which compares the experimental model image with the database. When the matching rate is greater than or equal to the preset percentage, the feature matching is completed, and the measurement results and decision instructions are generated and transmitted to the automation equipment control system. The automation equipment control system controls the three-axis screw open T-type slide and the four-axis screw closed gantry slide to move according to the given motion path. The controller also controls the high-speed camera to trigger double-frame exposure according to the given exposure parameters, obtains the particle image of the experimental model, and performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

[0024] In the above solution, the machine vision system collects images of the experimental model in the experimental section and compares the experimental model images with the database, specifically including the following steps:

[0025] The basic features, flow field type and calibration features of the experimental model are identified. Based on the basic features, flow field type and calibration features of the experimental model, the corresponding three-axis screw open T-type slide and four-axis screw closed gantry slide are found from the historical strategy library to obtain the motion path and exposure parameter combination of the high-speed camera. The measurement results and decision instructions are generated and transmitted to the automation equipment control system. The automation equipment control system controls the three-axis screw open T-type slide to perform an automatic calibration process. The high-speed camera on the three-axis screw open T-type slide calibrates and collects the calibration plate in the center of the measurement area and performs real-time distortion correction before transmitting the relevant data to the PIV system. The system generates a coordinate mapping table. After the automatic calibration process is completed, the automation equipment control system controls the four-axis screw closed gantry slide to move according to the preset grid according to the measurement results and decision instructions. The controller controls the high-speed camera to synchronously trigger double-frame exposure to obtain particle images of the flow around the experimental model. The particle image processing unit performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The image processing unit of the present invention compares the experimental model image with the database, identifies the basic features, flow field type and calibration features of the experimental model, finds the corresponding slide motion path and exposure parameter combination of the high-speed camera from the historical strategy library according to the basic features, flow field type and calibration features of the experimental model, generates measurement results and decision instructions and transmits them to the automation equipment control system, the automation equipment control system controls the high-speed camera to calibrate and collect the calibration plate in the center of the measurement area and performs real-time distortion correction before transmitting the relevant data to the PIV system, and the PIV system generates a coordinate mapping table. After the automatic calibration process is completed, the automation equipment control system controls the slide to move according to the preset grid according to the measurement results and decision instructions, the controller controls the high-speed camera to synchronously trigger double-frame exposure to obtain particle images of the experimental model flow field, and the particle image processing unit performs cross-correlation analysis in real time to obtain velocity field data, thereby realizing automated PIV measurement.

[0028] The automated PIV measurement equipment of the present invention adopts a high-precision three-axis lead screw open T-type slide and a four-axis lead screw closed gantry slide, which can achieve high positioning accuracy. Usually, the positioning error can reach the sub-millimeter level, and the calibration work can be completed quickly and accurately. Multi-axis linkage is achieved through the automated equipment control system, that is, movement in different directions is carried out simultaneously, and more complex motion tasks can be completed, thereby improving production efficiency. By adjusting the parameters in the automated equipment control system, the parameters such as the movement speed, acceleration and position of the module can be changed, so that it has greater flexibility and adjustability in different application scenarios. The present invention is also equipped with safety devices, such as limit switches, emergency stop buttons, etc., to ensure the safe operation of the equipment.

[0029] The X, Y, and Z axes of the three-axis screw-type open T-type slide and the four-axis screw-type closed gantry slide of the present invention are adjusted according to the experimental section length (L), width (D), and height (H), enabling both small-scale and large-scale measurements with wide adaptability. By integrating automated equipment into traditional PIV systems, the present invention further enhances the auxiliary role of PIV equipment in fluid testing technology. This invention has important engineering application value and application prospects for improving fluid testing technology and enriching fluid testing methods.

[0030] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of the above effects. Effects other than the above can be clearly seen and extracted from the description of the specification, drawings, claims, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an overall schematic diagram of an automated particle image velocimetry device operating in an embodiment of the present invention;

[0032] Figure 2 Schematic diagram of an automated particle image velocimetry device according to one embodiment of the present invention;

[0033] Figure 3 Schematic diagram of a three-axis screw open T-type slide according to one embodiment of the present invention;

[0034] Figure 4 Schematic diagram of a four-axis screw-type closed gantry slide according to one embodiment of the present invention;

[0035] Figure 5 is a schematic diagram of a machine vision system and a controller according to one embodiment of the present invention;

[0036] Figure 6 A schematic diagram of the control method principle of one embodiment of the present invention;

[0037] Figure 7 A schematic diagram of an Audi A7 1:24 model according to an embodiment of the present invention;

[0038] Figure 8 A schematic diagram of an Audi A4 1:24 model according to an embodiment of the present invention;

[0039] Figure 9 A schematic diagram of a 1:24 scale model of an Audi A6 Avant according to an embodiment of the present invention;

[0040] Figure 10 This is a schematic diagram of image preprocessing according to one embodiment of the present invention;

[0041] Figure 11A schematic diagram of length calibration according to an embodiment of the present invention;

[0042] Figure 12 Schematic diagram of PIVlab analysis according to one embodiment of the present invention;

[0043] Figure 13 Schematic diagram of PIVlab post-analysis processing according to one embodiment of the present invention.

[0044] In the figure, 1. Light source; 2. CMOS camera; 3. Image acquisition card; 4. Computer and control system; 5. Experimental; 6. Three-axis lead screw open T-type slide; 7. Four-axis lead screw closed gantry slide; 8. High-speed camera; 9. Laser source; 10. Stepper motor driver; 11. Automation equipment control system. DETAILED DESCRIPTION

[0045] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0046] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "front", "back", "left", "right", "up", "down", "axial", "radial", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0047] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0048] like Figure 1-4 As shown, a preferred embodiment of the automated particle image velocimetry device of the present invention is shown, which includes a three-axis screw open T-type slide 6, a four-axis screw closed gantry slide 7, a machine vision system, a PIV system, a controller 4 and an automated equipment control system 11;

[0049] The machine vision system is arranged on one side of the experimental section 5, the three-axis screw open T-type slide 6 is arranged on the other side of the experimental section 5, and the four-axis screw closed gantry slide 7 is arranged below the experimental section 5; the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 are respectively connected to the stepper motor, and the stepper motor is respectively connected to the stepper motor driver, so as to provide the load with a movement speed and accuracy that meets the experimental requirements; the application of the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 improves the scalability and flexibility of the equipment;

[0050] The PIV system includes a high-speed camera 8 and a laser source 9; the high-speed camera 8 is mounted on a three-axis screw open T-type slide 6, and the laser source 9 is mounted on a four-axis screw closed gantry slide 7;

[0051] The automation equipment control system 11 is connected to the stepper motor driver and the machine vision system respectively;

[0052] The controller 4 is connected to the machine vision system, the PIV system and the automation equipment control system 11 respectively;

[0053] The experimental section 5 is used to place the experimental model; the machine vision system is used to collect images of the experimental model in the experimental section 5 and transmit them to the controller 4. The controller 4 compares the experimental model image with the database. When the matching rate is greater than or equal to the preset percentage, the feature matching is completed, and the measurement results and decision instructions are generated and transmitted to the automation equipment control system 11. The automation equipment control system 11 controls the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 to move according to the given motion path. The controller 4 also controls the high-speed camera 8 to trigger double-frame exposure according to the given exposure parameters, obtains the particle image of the experimental model, and performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

[0054] like Figure 5 As shown, the machine vision system includes an illumination light source 1 , a CMOS camera 2 and an image acquisition card 3 ; the CMOS camera 2 is connected to a controller 4 via the image acquisition card 3 .

[0055] The controller 4 includes an image processing unit and a particle image processing unit; a database is provided in the image processing unit; the database includes a basic feature library, a flow field type library, a calibration feature library and a historical strategy library; the data type stored in the basic feature library is the three-dimensional point cloud or contour feature of the experimental model; the data type stored in the flow field type library is the flow field pattern feature vector; the data type stored in the calibration feature library is the calibration plate image template and distortion parameter, and the calibration feature library pre-stores the reference images of calibration plates of different sizes and supports the automatic distortion correction function; the historical strategy library stores the motion path planning schemes of the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 of multiple successful experiments, and the historical strategy library records the verified motion paths of the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7, as well as the exposure parameter combination of the high-speed camera 8, to support similar scene calls; the particle image processing unit is used to perform real-time cross-correlation analysis of the particle image of the experimental model and obtain velocity field data.

[0056] The image processing unit is used to compare the experimental model image with the database, identify the basic features, flow field type and calibration features of the experimental model, and find the corresponding three-axis screw open T-type slide 6 and four-axis screw closed gantry slide 7 from the historical strategy library according to the basic features, flow field type and calibration features of the experimental model to obtain the motion path and exposure parameter combination of the high-speed camera 8, generate measurement results and decision instructions and transmit them to the automation equipment control system 11, the automation equipment control system 11 controls the three-axis screw open T-type slide 6 to perform an automatic calibration process, the high-speed camera 8 on the three-axis screw open T-type slide 6 calibrates and collects the calibration plate in the center of the measurement area and performs real-time distortion correction before transmitting the relevant data to the PIV system, and the PIV system generates a coordinate mapping table. After the automatic calibration process is completed, the automation equipment control system 11 controls the four-axis screw closed gantry slide 7 to move according to the preset grid according to the measurement results and decision instructions, the controller 4 controls the high-speed camera 8 to synchronously trigger double-frame exposure to obtain particle images of the flow around the experimental model, and the particle image processing unit performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

[0057] The experimental section 5 is rectangular; the length of the experimental section 5 is L, the width is D, and the height is H.

[0058] The X-axis stroke of the three-axis screw open T-type slide 6 is set to L, the Z-axis stroke of the three-axis screw open T-type slide 6 is set to H for all-round shooting of the flow field in the experimental section 5, and the Y-axis stroke of the three-axis screw open T-type slide 6 is set to D for focusing of the high-speed camera 8. At the same time, the camera can be retracted to facilitate the placement of the measurement object in the experimental section.

[0059] The X-axis stroke of the four-axis screw closed gantry slide 7 is set to D, the Y-axis stroke of the four-axis screw closed gantry slide 7 is set to L for all-round laser irradiation of the flow field in the experimental section, and the Z-axis stroke of the four-axis screw closed gantry slide 7 is set to L for lifting the laser source 9 to better irradiate the measurement object in the experimental section.

[0060] The automation equipment control system 11 is provided with a touch screen.

[0061] The controller 4 is connected to the automation equipment control system 11, and can start and stop, and control the position and speed of the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7, and display the position and speed information in real time.

[0062] like Figure 6 As shown, a control method according to the automated particle image velocimetry device comprises the following steps:

[0063] The machine vision system is set on one side of the test section 5, the three-axis screw open T-type slide 6 is set on the other side of the test section 5, and the four-axis screw closed gantry slide 7 is set below the test section 5; the high-speed camera 8 is installed on the three-axis screw open T-type slide 6, and the laser source 9 is installed on the four-axis screw closed gantry slide 7; the experimental model is placed in the experimental section 5; the machine vision system collects the image of the experimental model in the experimental section 5 and transmits it to the controller 4, the controller 4 compares the experimental model image with the database, and when the matching rate is greater than or equal to the preset percentage, the feature matching is completed, and the measurement results and decision instructions are generated and transmitted to the automation equipment control system 11, the automation equipment control system 11 controls the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 to move according to the given motion path, and the controller 4 simultaneously controls the high-speed camera 8 to trigger double-frame exposure according to the given exposure parameters, obtains the particle image of the experimental model, and performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

[0064] The machine vision system collects images of the experimental model in experimental section 5 and compares the experimental model images with the database, specifically including the following steps:

[0065] The basic features, flow field type and calibration features of the experimental model are identified. According to the basic features, flow field type and calibration features of the experimental model, the corresponding three-axis screw open T-type slide 6 and four-axis screw closed gantry slide 7 are found from the historical strategy library to obtain the motion path and the exposure parameter combination of the high-speed camera 8. The measurement results and decision instructions are generated and transmitted to the automation equipment control system 11. The automation equipment control system 11 controls the three-axis screw open T-type slide 6 to perform an automatic calibration process. The high-speed camera 8 on the three-axis screw open T-type slide 6 calibrates and collects the calibration plate in the center of the measurement area and performs real-time distortion correction before transmitting the relevant data to the PIV system. The system generates a coordinate mapping table. After the automatic calibration process is completed, the automation equipment control system 11 controls the four-axis screw closed gantry slide 7 to move according to the preset grid according to the measurement results and decision instructions. The controller 4 controls the high-speed camera 8 to synchronously trigger double-frame exposure to obtain particle images of the flow around the experimental model. The particle image processing unit performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

[0066] The present invention is based on the automation transformation and innovation of the two-dimensional PIV measurement equipment. Through the three-axis screw open T-type slide 6, the four-axis screw closed gantry slide 7 and the machine vision system, a better experimental application effect is achieved. When using the device of the present invention to perform PIV experiments, it should be carried out indoors to reduce the impact of changes in the ambient light environment.

[0067] The experimental section 5 of the present invention is located in the middle of the automated equipment. The experimental section 5 is used to place experimental models, and can conduct research on aerodynamic characteristics, boundary layer characteristics, and other aspects. In a specific embodiment of the present invention, the air flow velocity range of the experimental section 5 is (0.1-60) m / s, the velocity stability coefficient is ≤0.5%, the velocity uniformity coefficient is ≤1%, and the wind speed resolution is 0.1 m / s. In a specific embodiment of the present invention, the overall dimensions of the experimental section 5 are length L = 800 mm * width D = 300 mm * height H = 300 mm. According to the dimensions of the experimental section 5, an appropriate experimental model is placed.

[0068] The stroke and layout of the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 in the present invention are set according to the size and shape of the experimental section 5. In a specific embodiment of the present invention, the three-axis screw open T-type slide 6 for loading the high-speed camera 8 of the PIV system is arranged on the right side of the experimental section 5. Figure 3As shown, because the area available for filming on the right side of the experimental section 5 is a 300mm*800mm rectangle, the X-axis stroke of the three-axis screw open T-type slide 6 is set to 800mm, and the Z-axis stroke is set to 300mm to capture the flow field in the experimental section 5 in all directions. The Y-axis stroke is set to 300mm for focusing of the high-speed camera 8. At the same time, the camera can be withdrawn to facilitate the placement of the measurement object in the experimental section 5. The material of the three-axis screw open T-type slide 6 is high-carbon chromium bearing steel, and the drive system uses a stepper motor and a stepper motor driver to form a stepper motor drive system. The drive system has an accuracy of ±0.05mm, a running speed of 90mm / s, and a load capacity of 20kg. The X, Y, and Z axes of the three-axis screw open T-type slide 6 are all installed with normally open NPN limit switches to limit the slide.

[0069] The four-axis screw-type closed gantry slide 7 carrying the laser source 9 in the PIV system is arranged below the experimental section 5, as shown in FIG. Figure 4 As shown, because the area below the experimental section available for laser irradiation is a 300mm*800mm rectangle, the four-axis screw-type enclosed gantry slide 7 is set with an X-axis stroke of 300mm and a Y-axis stroke of 800mm to provide full laser irradiation of the flow field in the experimental section. The experimental section is placed at a height of 830mm from the ground, so the Z-axis stroke is set to 800mm to lift the laser source 9 to better illuminate the measurement object within the experimental section. The four-axis screw-type enclosed gantry slide 7 is made of high-carbon chromium bearing steel, and the drive system uses a stepper motor and stepper motor driver to form a stepper motor drive system. This drive system has an accuracy of ±0.05mm, an operating speed of 90mm / s, and a load capacity of 20kg. Two sets of identical slides are set in the Y direction of the four-axis screw-type enclosed gantry slide 7 to stabilize the large-mass laser source, and normally open NPN limit switches are installed on the X, Y, and Z axes to provide limit protection for the slides.

[0070] The weight of the high-speed camera and laser source in the PIV system are 5.6kg and 18.9kg respectively. The three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 are placed at the bottom and right side of the experimental section respectively to ensure that their motion range can cover the experimental section. The machine vision system is arranged on the left side to scan and identify the entire experimental section, thereby improving the accuracy and reliability of the experimental data. In the present invention, a machine vision system is arranged on the left side of the experimental section 5, and its structure is as follows: Figure 5As shown, when the measurement starts, the light source 1 of the machine vision system is first turned on to provide good illumination for the experimental section 5 and its measured object, and then the CMOS camera 2 is used to collect the information. The collected information is input to the controller 4 through the image acquisition card 3 for processing and analysis. After comparison with the database in the controller 4, when the feature matching rate is greater than 90%, the matching is completed, and the measurement results and decision instructions are generated and transmitted to the automation equipment control system 11. The automation equipment control system 11 controls the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 to move according to the given motion path. The controller 4 simultaneously controls the high-speed camera 8 to trigger double-frame exposure according to the given exposure parameters, obtains the particle image of the flow around the experimental model, and performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

[0071] The schematic diagram of the experimental control system of the present invention is as follows: Figure 6 As shown. The controller 4 is a computer. The machine vision system collects images of the experimental model in the experimental section 5 and transmits them to the controller 4. The controller 4 compares the experimental model image with the database. When the matching rate is greater than or equal to a preset percentage, the feature matching is completed, and the measurement results and decision instructions are generated and transmitted to the automation equipment control system 11. The automation equipment control system 11 controls the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 to move according to the given motion path. The controller 4 also controls the high-speed camera 8 to trigger double-frame exposure according to the given exposure parameters, obtain particle images of the flow around the experimental model, and perform real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

[0072] The automated equipment control system 11 is equipped with a touch screen that can realize independent control of the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7, which is used for manual operation in special circumstances. After the three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 are calibrated in place according to the established control scheme, they stop moving. The operator checks the automatic calibration results. If they are qualified, the operator clicks the "Continue" button on the computer system control page. The three-axis screw open T-type slide 6 and the four-axis screw closed gantry slide 7 continue to perform subsequent measurement experiments according to the established control program. After the measurement is completed, the measurement results are checked to see if they meet the predetermined requirements. If not, the control scheme can be modified on the computer or the touch screen of the automated equipment control system 11 to continue measuring until the requirements are met. The controller 4 automatically checks whether the experimental data has been collected. If the experimental data records are complete, the data and images will be automatically saved to the corresponding files on the computer; otherwise, the experiment is invalid and needs to be restarted. After the experiment is completed, the "Stop" button is clicked on the computer to stop all components. After turning off the power, the connection can be disconnected to end the experiment. After handling the experimental equipment and site, you can analyze and process the experimental data.

[0073] In a specific embodiment of the present invention, the controller 4 stores a database, which adopts a hierarchical design and is divided into four levels: 1. Basic feature library, which stores data types: three-dimensional point cloud / contour features of experimental models. It can store geometric features of some standard models such as wings and cylinders, and realize object recognition through point cloud matching. 2. Flow field type library, which stores data types: flow field pattern feature vectors. It can store some classifications based on Reynolds number / turbulence intensity, such as laminar / turbulent boundary layer, vortex street, etc., and associate corresponding PIV parameter schemes. 3. Calibration feature library, which stores data types: calibration plate image templates and distortion parameters. The library pre-stores reference images of calibration plates of different sizes and supports automatic distortion correction function. 4. Historical strategy library, which stores trajectory planning schemes of some successful experiments. The library supports similar scene calls by recording verified slide motion paths and exposure parameter combinations.

[0074] When the user uses the system, the experimental model should be placed first. At this time, the CMOS camera 2 in the machine vision system triggers the scanning of the experimental model. After the scanning is completed, the model image is input into the image processing unit, and then the image processing unit compares the model image with the database. Preferably, when the matching rate is greater than 90%, the feature matching is completed, and the measurement results and decision instructions are generated and transmitted to the automation equipment control system 11. The automation equipment control system 11 controls the three-axis screw open T-type slide 6 to perform an automatic calibration process. The high-speed camera 8 on the three-axis screw open T-type slide 6 calibrates and collects the calibration plate in the center of the measurement area and performs real-time distortion correction before transmitting the relevant data to the PIV system. The system generates a coordinate mapping table. After the automatic calibration process is completed, the automation equipment control system 11 controls the four-axis screw closed gantry slide 7 to move according to the preset grid according to the measurement results and decision instructions. The controller 4 controls the high-speed camera 8 to synchronously trigger double-frame exposure to obtain particle images of the flow around the experimental model. The particle image processing unit uses GPU accelerated calculation to obtain velocity field data through real-time cross-correlation analysis, thereby realizing automated PIV measurement.

[0075] By using automated equipment and tailoring the structural design and layout to the experimental section size, this invention significantly improves the efficiency of PIV measurement, reduces the time and labor costs of PIV measurement, and increases the accuracy and measurement range of PIV measurement. Fast, efficient, and accurate automated PIV measurement can significantly accelerate research progress.

[0076] In a specific embodiment of the present invention, the flow around the car model is studied based on the automated particle image velocimetry equipment, especially the wake field, which is conducive to promoting the improvement of the theoretical framework of automobile aerodynamics. On this basis, the PIV technology is further used to intuitively analyze the entire flow around the car model, which has relatively strong practical value and is conducive to further research on drag reduction and energy saving in the automotive industry.

[0077] like Figure 7-9 As shown, experimental objects: Audi A7 1:24 model, Audi A4 1:24 model, Audi A6 Avant 1:24 model.

[0078] The DrivAer model, due to its standardized and modular design, has become an important reference model in the field of international automotive aerodynamics research. The database contains three different DrivAer vehicle models: Fastback, Notchback, and Estateback. Automotive aerodynamic performance directly impacts energy consumption and driving stability. Studying the complex flow characteristics of the flow field around a vehicle is crucial for improving its aerodynamic performance. This embodiment utilizes particle image velocimetry (PIV) to effectively measure the motion paths of a high-speed camera and laser source while measuring the flow characteristics of the tail structure at a wind speed of 10 m / s.

[0079] This example studies the flow fields around the tails of three car models. Specifically, the images are collected using automated particle image velocimetry equipment and processed using PIVlab (a particle image processing unit) to obtain a velocity vector field matrix for each frame. The data is then further integrated and processed to produce a clear cloud map of the average flow field and turbulence structure. This allows for intuitive observation of the flow state at each location before and after the car model, including the location of airflow separation and the location and extent of turbulence and vortex formation. This allows for intuitive analysis and description of the structure and mechanism, and subsequently provides a theoretical solution for vehicle drag reduction.

[0080] Taking the measurement of the Audi A6 Avant 1:24 model as an example, the model is placed in the experimental section 5, and the model contour image is collected by the CMOS camera 2. After the image processing unit recognizes the model, Figure 10 As shown, the car model image matches the DrivAer model FastBack configuration in the database at a rate of 92.7%, indicating a successful match. Furthermore, the exposure parameters of the high-speed camera 8 corresponding to the DrivAer model EstateBack configuration laminar / turbulent and vortex street were matched in the flow field type library in the system database. The image template and distortion parameters used in the calibration experiment for this configuration were matched in the calibration feature library in the database, as shown in the following example: Figure 11As shown, the motion trajectory planning scheme for high-speed camera 8 and laser source 9, which was successfully tested in this configuration, was matched to the historical strategy library in the system database. This scheme, namely the motion path planning scheme for the three-axis screw-type open T-type slide 6 and the four-axis screw-type closed gantry slide 7, was retrieved and transmitted to the automated equipment control system 11. The automated equipment control system 11 controlled the three-axis screw-type open T-type slide 6 and the four-axis screw-type closed gantry slide 7 to move according to the given motion path. Simultaneously, the controller 4 controlled the high-speed camera 8 to trigger double-frame exposure according to the given exposure parameters, capturing tens of thousands of flow images captured by the high-speed camera 8 and clearly recording the velocity vector of each pixel in the flow field at each moment. Based on this, the controller 4 analyzed and filtered the corresponding parameters and imported 509 consecutive images into PIVlab (Particle Image Processing Unit). Detailed settings were performed in PIVlab: pre-analysis filter channel setting, mask drawing, analysis channel size and number setting, reference length setting, post-analysis velocity vector screening and missing data interpolation. All image analysis was then performed, and the analyzed data was finally exported as a .mat file. The measurement results are as follows Figure 12 and 13 As shown in the figure, the high turbulence intensity areas at the rear of the model body are mainly concentrated in the roof separation shear layer, the rear recirculation area, and the tail vortex area. The areas with higher turbulence intensity are in the wake and the lower edge recirculation area, where the turbulent mixing intensity is relatively high.

[0081] The present invention uses a machine vision system to preprocess the object being measured by PIV and compares the processing results with a database. By identifying the measurement object and experiment type, the present invention automatically formulates and transmits a control strategy to the automated equipment control system 11. This strategy controls the three-axis screw-type open T-type slide 6, the four-axis screw-type closed gantry slide 7, and the high-speed camera 8 to perform predetermined actions, thereby achieving automated PIV measurement. This invention has significant engineering application value and promising prospects for improving fluid testing technology and enriching fluid testing methods.

[0082] The present invention utilizes the precise and stable characteristics of automation technology to quickly and accurately complete a large amount of repetitive work, reduce the errors and delays of manual operations, and thus improve the overall research speed. Automation technology also has the characteristic of flexibility. The X-axis, Y-axis and Z-axis of the three-axis screw open T-type slide and the four-axis screw closed gantry slide are adjusted according to the length L, width D and height H of the experimental section. Small-scale and large-scale measurements can be performed, and can be flexibly adjusted according to different production needs. Through programming and setting, the equipment's travel trajectory, equipment specifications and other parameters can be easily changed to adapt to changes in different experimental requirements during actual measurement, thereby improving the practicality and scalability of the present invention.

[0083] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0084] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. An automated particle image velocimetry device, characterized in that: It includes a three-axis screw open T-type slide (6), a four-axis screw closed gantry slide (7), a machine vision system, a PIV system, a controller (4) and an automation equipment control system (11); The machine vision system is arranged on one side of the experimental section (5), the three-axis screw open T-type slide (6) is arranged on the other side of the experimental section (5), and the four-axis screw closed gantry slide (7) is arranged below the experimental section (5); the three-axis screw open T-type slide (6) and the four-axis screw closed gantry slide (7) are respectively connected to the stepper motor, and the stepper motor is respectively connected to the stepper motor driver; The PIV system includes a high-speed camera (8) and a laser source (9); the high-speed camera (8) is mounted on a three-axis screw open T-type slide (6), and the laser source (9) is mounted on a four-axis screw closed gantry slide (7); The automation equipment control system (11) is connected to the stepping motor driver and the machine vision system respectively; The controller (4) is connected to the machine vision system, the PIV system and the automation equipment control system (11) respectively; The experimental section (5) is used to place the experimental model; the machine vision system is used to collect the image of the experimental model in the experimental section (5) and transmit it to the controller (4); the controller (4) compares the experimental model image with the database; when the matching rate is greater than or equal to a preset percentage, the feature matching is completed, and the measurement results and decision instructions are generated and transmitted to the automation equipment control system (11); the automation equipment control system (11) controls the three-axis screw open T-type slide (6) and the four-axis screw closed gantry slide (7) to move according to the given motion path; the controller (4) simultaneously controls the high-speed camera (8) to trigger double-frame exposure according to the given exposure parameters, obtains the particle image of the experimental model, and performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

2. The automated particle image velocimetry device according to claim 1, characterized in that: The machine vision system comprises an illumination light source (1), a CMOS camera (2) and an image acquisition card (3); the CMOS camera (2) is connected to a controller (4) via the image acquisition card (3).

3. The automated particle image velocimetry device according to claim 2, characterized in that: The controller (4) includes an image processing unit and a particle image processing unit; The image processing unit is provided with a database; the database includes a basic feature library, a flow field type library, a calibration feature library and a historical strategy library; the data type stored in the basic feature library is a three-dimensional point cloud or contour feature of an experimental model; the data type stored in the flow field type library is a flow field pattern feature vector; the data type stored in the calibration feature library is a calibration plate image template and distortion parameters, and the calibration feature library pre-stores reference images of calibration plates of different sizes and supports an automatic distortion correction function; the historical strategy library stores motion path planning schemes of a plurality of successful experiments of a three-axis screw open T-type slide (6) and a four-axis screw closed gantry slide (7), and the historical strategy library records the verified motion paths of the three-axis screw open T-type slide (6) and the four-axis screw closed gantry slide (7) and the exposure parameter combination of the high-speed camera (8), so as to support similar scene calls; The particle image processing unit is used to perform real-time cross-correlation analysis on the particle images of the experimental model to obtain velocity field data.

4. The automated particle image velocimetry device according to claim 3, characterized in that: The image processing unit is used to compare the experimental model image with the database, identify the basic features, flow field type and calibration features of the experimental model, find the corresponding three-axis screw open T-type slide (6) and four-axis screw closed gantry slide (7) from the historical strategy library according to the basic features, flow field type and calibration features of the experimental model, obtain the motion path and the exposure parameter combination of the high-speed camera (8), generate measurement results and decision instructions and transmit them to the automation equipment control system (11), the automation equipment control system (11) controls the three-axis screw open T-type slide (6) to perform an automatic calibration process, and the three-axis screw open T-type slide The high-speed camera (8) on (6) calibrates and collects the calibration plate at the center of the measurement area and performs real-time distortion correction before transmitting the relevant data to the PIV system. The PIV system generates a coordinate mapping table. After the automatic calibration process is completed, the automation equipment control system (11) controls the four-axis screw closed gantry slide (7) to move according to the preset grid based on the measurement results and decision instructions. The controller (4) controls the high-speed camera (8) to synchronously trigger double-frame exposure to obtain particle images of the experimental model. The particle image processing unit performs real-time cross-correlation analysis to obtain corresponding velocity field data, thereby realizing automated PIV measurement.

5. The automated particle image velocimetry device according to claim 1, wherein: The experimental section (5) is rectangular; the length of the experimental section (5) is L, the width is D, and the height is H.

6. The automated particle image velocimetry device according to claim 5, characterized in that: The X-axis travel of the three-axis screw open T-type slide (6) is set to L, the Z-axis travel of the three-axis screw open T-type slide (6) is set to H for all-around shooting of the flow field in the experimental section (5), and the Y-axis travel of the three-axis screw open T-type slide (6) is set to D for focusing of the high-speed camera (8).

7. The automated particle image velocimetry device according to claim 5, characterized in that: The X-axis travel of the four-axis screw closed gantry slide (7) is set to D, the Y-axis travel of the four-axis screw closed gantry slide (7) is set to L for all-round laser irradiation of the flow field in the experimental section, and the Z-axis travel of the four-axis screw closed gantry slide (7) is set to L for lifting the laser source (9).

8. The automated particle image velocimetry device according to claim 1, wherein: The automation equipment control system (11) is provided with a touch screen.

9. A method for controlling the automated particle image velocimetry device according to any one of claims 1 to 8, characterized in that: The following steps are involved: The machine vision system is arranged on one side of the test section (5), the three-axis screw open T-type slide (6) is arranged on the other side of the test section (5), and the four-axis screw closed gantry slide (7) is arranged below the test section (5); the high-speed camera (8) is mounted on the three-axis screw open T-type slide (6), and the laser source (9) is mounted on the four-axis screw closed gantry slide (7); the experimental model is placed in the experimental section (5); the machine vision system collects the image of the experimental model in the experimental section (5) and transmits it to the controller (4), and the controller (4) The image is compared with the database. When the matching rate is greater than or equal to a preset percentage, feature matching is completed, and measurement results and decision instructions are generated and transmitted to the automation equipment control system (11). The automation equipment control system (11) controls the three-axis screw open T-type slide (6) and the four-axis screw closed gantry slide (7) to move according to the given motion path. The controller (4) simultaneously controls the high-speed camera (8) to trigger double-frame exposure according to the given exposure parameters, obtains the particle image of the experimental model, and performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

10. The control method of the automated particle image velocimetry device according to claim 9, characterized in that: The machine vision system collects an image of the experimental model in the experimental section (5) and compares the image of the experimental model with the database, specifically comprising the following steps: Identify the basic features of the experimental model, the flow field type and the calibration features, find the corresponding three-axis screw open T-type slide (6) and four-axis screw closed gantry slide (7) from the historical strategy library according to the basic features of the experimental model, the flow field type and the calibration features, obtain the motion path and the exposure parameter combination of the high-speed camera (8), generate the measurement results and decision instructions and transmit them to the automation equipment control system (11), the automation equipment control system (11) controls the three-axis screw open T-type slide (6) to perform the automatic calibration process, and the high-speed camera on the three-axis screw open T-type slide (6) (8) The calibration plate at the center of the measurement area is calibrated and collected, and the relevant data is transmitted to the PIV system after real-time distortion correction. The system generates a coordinate mapping table. After the automatic calibration process is completed, the automation equipment control system (11) controls the four-axis screw closed gantry slide (7) to move according to the preset grid based on the measurement results and decision instructions. The controller (4) controls the high-speed camera (8) to synchronously trigger double-frame exposure to obtain particle images of the experimental model. The particle image processing unit performs real-time cross-correlation analysis to obtain velocity field data, thereby realizing automated PIV measurement.

Images