Positioner precision rectification and zero calibration system and method

Abstract

The invention belongs to the technical field of steam generator heat transfer tube nondestructive testing, and discloses a positioner precision deviation rectification and zero calibration system and method.The system comprises a positioner and a water chamber camera which are arranged in a water chamber, and an upper computer and a control box which are arranged outside the water chamber. The method comprises the following steps: establishing a coordinate system with a pipe hole at the upper left corner as an original point, resolving the pose of a positioner, obtaining the actual space coordinates of the pipe hole of the heat transfer pipe, obtaining the two-dimensional coordinates of the circle center of the pipe hole, and feeding back the two-dimensional coordinates to a control center for error analysis; collecting an image by a camera of the positioner, and accurately identifying the position of the circle center after graying, filtering and edge detection preprocessing and interference elimination; and final precision compensation is completed. Through double-camera calibration, tube hole image denoising, image edge detection, heat transfer tube hole identification, heat transfer tube hole positioning and the like, automatic identification of the tube hole of the evaporator tube plate is realized, so that the positioner can automatically perform zero calibration, and the positioning precision of the positioner is improved.

Description

Technical Field

[0001] This application belongs to the technical field of non-destructive testing of heat transfer tubes in steam generators, and particularly relates to a positioner accuracy correction and zero position calibration system and method. Background Art

[0002] Nuclear power plants have a wide variety of heat exchangers and pressure-bearing equipment. These equipment must be subjected to non-destructive testing in accordance with certain specifications before and after being put into operation. Due to the characteristics of the nuclear industry itself, these equipment operate either under radioactive conditions or under high temperature and high pressure (tensile force) with relatively frequent fluctuations. Therefore, their inspection cycles are more frequent than those in other industries. The number of heat transfer tubes in the evaporator is numerous, and it is inevitable that they will come into contact with each other. As a result, damage to the heat transfer tubes is inevitable due to heat exchange. At the same time, considering that the liquid inside the heat transfer tubes of the evaporator has corrosiveness or even radioactivity, the above factors all lead to the degradation of the heat transfer tubes. Therefore, it is necessary to perform eddy current testing on the heat transfer tubes. Eddy current testing systems are generally used to inspect the heat transfer tubes of nuclear power plant steam generators.

[0003] The eddy current testing process for the heat transfer tubes of the evaporator is as follows: The tube sheet positioner carries the probe door and crawls on the tube sheet. The positioner adjusts its own position by moving on the tube sheet. After reaching the target position, it fixes itself, adjusts the maintenance tool to align with the tube hole to be inspected and extends the corresponding maintenance tool, and uses a matching pushing device to transmit the eddy current testing probe into the heat transfer tube to be tested to complete the eddy current testing. Therefore, the positioning of the tube sheet positioner is crucial. Inaccurate positioning will seriously affect the results of eddy current testing.

[0004] The usual way to judge the position of the positioner is to place a high-resolution camera inside the water chamber of the evaporator. The high-resolution camera takes pictures of the tube holes, and then transmits the taken pictures to a computer dedicated to image processing through optical fibers. The operator observes the display screen to judge whether the current position of the positioner is consistent with the position of the positioner on the control software. The operator has low position accuracy, slow speed, and low real-time performance when observing the position of the positioner. At the same time, it requires the scientific research personnel to have similar work experience, which has high requirements for personnel. Moreover, once the position check is inaccurate this time, it will not only affect the next position check but also invalidate the previous position check results, which will greatly waste manpower and time and increase the radiation dose received by personnel. Summary of the Invention

[0005] The purpose of this application is to overcome the defects of the prior art and provide a positioner accuracy correction and zero position calibration system and method to realize automatic identification of the tube holes on the evaporator tube sheet, enable the positioner to automatically perform zero position calibration and accuracy correction, and improve the positioning accuracy of the positioner.

[0006] To achieve the above purpose, this application provides the following technical solutions:

[0007] In a first aspect, the present application provides a system for correcting the accuracy and calibrating the zero position of a locator, including a locator, a water chamber camera arranged in a water chamber, and a host computer and a control box arranged outside the water chamber;

[0008] The locator includes a slide table, a turntable, a base, a tool, a locator camera, and a tool camera. The turntable is installed on the base, and the base is installed on the slide table. The locator camera is used to photograph the tube holes of the evaporator heat transfer tubes, and the tool camera is used to observe the alignment of the tool and the heat transfer tubes;

[0009] The water chamber camera includes an LED lamp, a lens, and a pan-tilt head. The LED lamp is arranged below the fixed seat of the pan-tilt head, and the lens and the pan-tilt head are installed on the fixed seat of the pan-tilt head.

[0010] In some embodiments, the control box includes a controller, a driver, a lower computer, an I / O module, a power supply, and a video server.

[0011] In some embodiments, the locator camera includes an embedded LED lamp and a locator camera lens. The locator camera lens is located at the center, and the embedded LED lamps are evenly distributed circumferentially around the locator camera lens.

[0012] In some embodiments, the LED lamp is installed on a fixed seat of the LED lamp, an LED lamp cover is provided on the LED lamp, and a camera cover is provided on the lens.

[0013] In some embodiments, the number of the LED lamps is 3, and they are arranged in a triangle.

[0014] In a second aspect, the present application provides a method for correcting the accuracy and calibrating the zero position of a locator, including:

[0015] Step 1: Install the locator on the tube sheet, and install the water chamber camera in the water chamber. The water chamber camera is fixed in the water chamber by an electromagnet, and the water chamber camera photographs the entire tube sheet and the locator;

[0016] Step 2: Fix the water chamber camera based on the electromagnet and calibrate its relative position with the locator. Collect images from multiple angles through the pan-tilt head, extract the distribution of tube holes through grayscale conversion, binarization, corrosion, and contour detection, establish a coordinate system with the upper left tube hole as the origin, and calculate the pose of the locator by combining the spatial relationships of the three 120° straight lines of the inner toes, the tool straight line, and the straight line outside the tail end;

[0017] Step 3: The two cameras determine the relative coordinates through laser positioning and pan-tilt head adjustment, and use the parallax of images at different angles combined with three-dimensional reconstruction technology to obtain the actual spatial coordinates of the tube holes of the heat transfer tubes;

[0018] Step 4: Install the water chamber camera vertically, obtain the two-dimensional coordinates of the center of the pipe hole and feed them back to the control center for error analysis;

[0019] Step 5: The image captured by the locator camera needs to be pre-processed by grayscale, filtering and edge detection. After eliminating interference, the center position of the circle is accurately identified to complete the final accuracy compensation.

[0020] In some embodiments, step 2 specifically includes:

[0021] Step 2.1: The water chamber camera is fixed inside the water chamber by the electromagnet, and the pan / tilt head is used to realize 360° horizontal rotation and 90° vertical swing of the lens to cover the field of view of all tube sheet holes, and the random initial relative position of the lens and the locator is determined by calibration;

[0022] Step 2.2: Grayscale and binarize the collected color image based on the lighting conditions. After the hole features are enhanced through corrosion, small black areas are detected and screened to identify the distribution of pores. Large shadow interference is eliminated to extract the locations of most pores.

[0023] Step 2.3: Using the unobstructed pore in the upper left corner as the coordinate origin, remove abnormal contour points using the 3σ criterion and analyze the geometric center spacing to determine the pore distribution type. Select the optimal straight line to determine the x-axis direction. Combine the distribution pattern and the x-axis spacing dx to derive the y-axis spacing dy, completing the image coordinate system construction.

[0024] Step 2.4: The three positioning lines and tool lines emitted by the inner toe of the crawler, which are at an angle of 120° to each other, are combined with the straight line painted on the outer side of the tail end to detect the spatial angle and position relationship of each light, and solve the inner positioning coordinates, inner and outer deflection angles, and tool angles of the locator 2 to determine its position.

[0025] In some embodiments, step 2.2 includes:

[0026] Determine the distribution of pores based on the brightness and darkness of the image;

[0027] Convert the collected color image into a grayscale image, set a grayscale value as a threshold, perform binarization on the image, and turn the tube sheet into a binary image;

[0028] Use the erosion operation to expand the black area, and use the contour detection algorithm provided by OpenCV to select all the black areas on the image;

[0029] The contours with larger areas are eliminated, and the contours with smaller areas are retained as pores.

[0030] In some embodiments, step 2.3 includes:

[0031] Establish an image coordinate system with the top-leftmost point as the coordinate origin;

[0032] Calculate the geometric centers of all contours on the image, calculate the shortest distance from each point to other points and save them;

[0033] Using the 3σ criterion, delete the abnormal distance values and the corresponding contours; among the remaining points, determine the distribution type of the tube holes on the tube sheet based on the relative positions of the surrounding points;

[0034] Select the point with the minimum row value and column value as the coordinate origin (the same point as the above-mentioned coordinate origin. The above indicates that the top-leftmost point is used as the coordinate origin, and later it refers to how to determine the top-leftmost point and its geometric center), draw a straight line passing through this point with an angle between -5 degrees and +5 degrees, calculate the number of tube holes that each straight line can pass through, select the straight line that can pass through the most tube holes as the x-axis of the image, and infer the relative distance dy of each point on the y-axis based on the relative distance dx of each point on the x-axis and the distribution type of the tube holes.

[0035] In some embodiments, step 2.4 includes:

[0036] Determine the pose of the locator. Use light to determine the inner position, angle, and tool angle of the crawler. Use the outer straight line coated on the surface of the crawler to determine the outer angle. Three straight lines are emitted at the inner toes of the crawler, namely inner toe straight line one, inner toe straight line two, and inner toe straight line three, with an included angle of 120° to each other. The tool emits one tool straight line, and an outer straight line is coated at the tail end of the crawler;

[0037] Determine the inner toe position of the locator. Using the straight line detection algorithm, the analytical expressions of the three inner toe straight lines are obtained as follows:

[0038] Inner toe straight line one: A b x + B b y + C b = 0;

[0039] Inner toe straight line two: A g x + B g y + C g = 0;

[0040] Inner toe straight line three: A r x + B r y + C r = 0;

[0041] The intersection of the three inner toe straight lines satisfies:

[0042]

[0043] Wherein, (x1, y1) are the coordinates of the center point of the inner toe. Combining with the coordinate origin (x0, y0), the row number n of the inner toe at this time is calculated. row and the column number n col :

[0044]

[0045] Determine the inner angle θ. According to the slopes of the analytical formulas of the three straight lines emitted by the inner toe, solve the inner angle θ. Taking the upward direction of the first inner toe straight line as 0°, counterclockwise as positive, and the value range is [0°, 360°);

[0046] Taking the first inner toe straight line as an example, record the coordinates of any point on the first inner toe straight line as (xb, yb);

[0047]

[0048] Among them, α b ∈(-90°, 90°);

[0049] Calculate θ b , θ g and θ r , θ b is the inner angle θ of the first inner toe straight line, θ g is the inner angle θ of the second inner toe straight line, θ r The inner angle θ of the third inner toe straight line. Take the average value of the three values as the inner angle Select the angle value closest to as the final inner angle θ;

[0050] Determine the tool angle β. The straight line analytical formula of the tool straight line emitted by the tool:

[0051] A p x + B p y + C p = 0

[0052] Taking the horizontal right direction of the tool straight line as 0°, record the coordinates of any point on the tool straight line as (x p , y p ), and calculate the tool angle β:

[0053]

[0054] Among them, α p ∈(-90°, 90°);

[0055] Determine the outer angle α, draw an outer straight line at the end of the crawler, identify the outer straight line, take the midpoint of the outer straight line, with coordinates (x2, y2), and use the coordinates (x1, y1) of the toe center point to calculate and obtain:

[0056]

[0057] In the formula, α is the outer angle of the crawler.

[0058] Compared with the prior art, the positioner accuracy correction and zero position calibration system and method provided by this application have the following beneficial effects:

[0059] This application performs double camera calibration, tube hole image denoising, image edge detection, heat transfer tube hole recognition, heat transfer tube hole positioning, etc., to realize automatic recognition of the tube holes on the evaporator tube sheet, enabling the positioner to automatically perform zero position calibration and improve the positioning accuracy of the positioner.

[0060] This application uses a positioner. The positioner takes two images of the same heat transfer tube hole at different angles through a double camera of a water chamber camera and a positioner camera. The water chamber camera takes images of the positioner and the tube sheet, and the initial position and attitude of the positioner on the tube sheet can be determined through the position and attitude calibration system of the positioner. The two cameras take two different images of the same target object at different angles at the same time to obtain parallax. The actual spatial coordinates of the target object can be accurately obtained by combining the obtained parallax with the principle of three-dimensional reconstruction. The double-calibrated camera obtains the two-dimensional coordinates of the center of the heat transfer tube hole, and feeds this coordinate back to the control center of the positioner for error analysis. The control center then gives the required compensation value to the motors in the turntable, sliding table, and tool to execute, so that the positioning robot can obtain the required accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions of this application, the following will briefly introduce the drawings required for the technical description.

[0062] Figure 1 It is a schematic structural diagram of the positioner accuracy correction and zero position calibration system provided by this application;

[0063] Figure 2 It is a schematic diagram of zero position calibration and accuracy compensation provided by this application;

[0064] Figure 3 It is a schematic diagram of the position of the water chamber camera and the positioner provided by this application;

[0065] Figure 4 It is a schematic structural diagram of the positioner provided by this application;

[0066] Figure 5 It is a schematic structural diagram of the water chamber camera provided by this application;

[0067] Figure 6 The flow chart of the locator pose calibration provided for this application;

[0068] Figure 7 The simple diagram of the locator straight line provided for this application;

[0069] Figure 8 The structural schematic diagram of the locator camera provided for this application;

[0070] Figure 9 The flow chart of the locator precision deviation correction and zero position calibration method provided for this application.

[0071] Explanation of the reference numerals in the drawings:

[0072] 1, tube sheet; 2, locator; 3, water chamber camera; 4, electromagnet; 5, simple diagram of the locator;

[0073] 21, slide table; 22, turntable; 23, base; 24, tool; 25, locator camera; 26, tool camera;

[0074] 251, embedded LED lamp; 252, locator camera lens;

[0075] 31, LED lamp; 32, LED lamp fixing seat; 33, lens; 34, pan-tilt head; 35, camera cover; 36, LED lamp cover; 37, pan-tilt head fixing seat;

[0076] 51, inner toe straight line 1; 52, inner toe straight line 2; 53, inner toe straight line 3; 54, tool straight line; 55, outer straight line. Detailed implementation manners

[0077] The following is a further detailed description through specific implementation manners.

[0078] As Figures 1 to 8 shown, this application provides a locator precision deviation correction and zero position calibration system, including a host computer outside the water chamber, a control box, and a locator 2 and a water chamber camera 3 inside the water chamber. A locator camera 25 is installed on the locator 2, and a lens 33 is installed on the water chamber camera 3. The host computer can control the locator 2 and the water chamber camera 3 through the control box, and simultaneously transmit the video and image signals of the locator camera and the water chamber camera lens.

[0079] As Figure 1 shown, the control box includes a controller, a driver, a lower computer, an I / O module, a power supply, and a video server. An existing control box can be used for the control box.

[0080] As Figure 3As shown in the figure, the locator 2 is installed on the tube sheet 1, and the water chamber camera 3 is installed in the water chamber. The water chamber camera 3 is fixed in the water chamber by the electromagnet 4 below. The water chamber camera 3 can complete the shooting of the entire tube sheet 1 and the locator 2. The water chamber camera 3 is placed in the water chamber and fixed to the water chamber by the electromagnet 4.

[0081] As Figure 4 shown in the figure, the locator 2 includes a sliding table 21, a turntable 22, a base 23, a tool 24, a locator camera 25, and a tool camera 26. The turntable 22 is installed on the base 23, and the base 23 is installed on the sliding table 21. Through the structures of the sliding table 21, the turntable 22, and the base 23, the locator 2 can crawl on the tube sheet 1. The locator camera 25 can shoot the tube holes of the evaporator heat transfer tubes, and the tool camera 26 is used to observe the alignment situation between the tool 24 and the heat transfer tubes. After the locator 2 is installed on the steam generator tube sheet 1, before the locator 2 crawls automatically on the tube sheet 1, it is necessary to determine the zero position of the locator 2 so that all heat transfer tubes can be inspected 100% through path planning and an effective anti-collision strategy can be planned during the entire positioning process. Before the locator 2 starts to move formally, the initialization settings of its respective motors are carried out first.

[0082] The locator 2 includes two locator cameras 25, and the two locator cameras 25 are respectively arranged on both sides of the turntable 22, showing a symmetrical layout.

[0083] Based on the tube sheet installation method, the motion positioning function requirements of the locator 2 are subdivided into three parts according to the motion principle of the mechanism: the sliding table 21, the turntable 22, and the base 23. To enable the locator 2 to complete continuous multi-angle alternating translation motion, the motion positioning mechanism is designed as a three-degree-of-freedom mechanism. The three motion degrees of freedom are: the rotational degree of freedom between the turntable 22 and the base to achieve multi-angle rotation, the relative translation degree of freedom between the sliding table 21 and the turntable 22 and the base 23 to achieve linear walking, and the relative lifting degree of freedom between the sliding table 21 and the turntable 22 and the base 23 to achieve the alternating lifting of the turntable toes and the sliding table toes. During operation, the turntable 22 and the sliding table 21 alternately perform translation, rotation, and lifting motions and rely on their respective positioning and clamping mechanisms to achieve motion positioning. To improve the positioning accuracy and reliability of the mechanism during motion positioning, three positioning and clamping mechanisms are designed on the turntable 22, and one positioning and clamping mechanism is designed at each end of the sliding table 21.

[0084] As Figure 8 shown in the figure, the locator camera 25 includes an embedded LED lamp 251 and a locator camera lens 252. The locator camera lens 252 is located at the center, and the embedded LED lamps 251 are evenly distributed circumferentially around the locator camera lens 251 to provide a lighting source for the lens.

[0085] AsFigure 5 As shown in the figure, the water chamber camera 3 includes an LED lamp 31, an LED lamp fixing base 32, a lens 33, a pan-tilt 34, and a pan-tilt fixing base 37. The number of LED lamps 31 is 3, which are arranged in a triangle. The LED lamp 31 is installed on the LED lamp fixing base 32. A pan-tilt fixing base 37 is set at the triangular center position of the three LED lamps 31. The lens 33 is fixed on the pan-tilt 34, and the pan-tilt 34 is installed on the pan-tilt fixing base 37.

[0086] The LED lamp 31 is covered with an LED lamp cover 36, and the lens 33 is covered with a camera cover 35. The three LED lamps 31 are evenly distributed around the pan-tilt 34 and the lens 33 to provide a light source for the lens 33, extract accurate features of the target in a complex environment, improve the accuracy of target recognition and positioning, and lay a solid foundation for subsequent target positioning and recognition. The pan-tilt 34 rotates the main body (the pan-tilt main body, the pan-tilt rotates itself, driving the lens 33 on the pan-tilt to rotate), which is used to realize the movement of the entire pan-tilt 34, and can realize 360° horizontal rotation and 90° vertical swing of the lens, ensuring that the lens 33 can cover all tube sheet holes. The initial installation position of the water chamber camera 3 is random. Therefore, it is necessary to determine the relative position between the water chamber camera 3 and the locator 2. The specific process is as Figure 6 shown, including the following steps:

[0087] (1) Camera calibration;

[0088] (2) System startup;

[0089] (3) Positioning origin;

[0090] (4) Determine the pose;

[0091] (5) Judge whether the relative position has changed. If it has changed, return to the positioning origin step. If it has not changed, return to the determine pose step.

[0092] In the identification and positioning of the heat transfer tube holes, the camera can convert the optical signal into an electrical signal. The locator 2 takes two images of the same heat transfer tube hole at different angles through the water chamber camera 3 and the locator camera 25. The two cameras take two different images of the same target object at different angles at the same time to obtain the parallax. The actual spatial coordinates of the target object can be accurately obtained by combining the obtained parallax with the principle of three-dimensional reconstruction. Further, the two-dimensional coordinates of the center of the heat transfer tube hole are obtained by using the double-calibrated camera, and this coordinate is fed back to the control center of the locator for error analysis. The control center then gives the required compensation value to the motors in the turntable 22, the sliding table 21, and the tool to execute, so that the positioning robot obtains the required accuracy.

[0093] There is an electromagnet 4 installed under the pan-tilt fixed base 37. The operating pan-tilt is sent into the evaporator water chamber and placed at a suitable position. After the electromagnet 4 is powered on, the pan-tilt 34 can be fixed. In the visual recognition and positioning system, the obvious features of the object to be measured are distinguished and revealed by the light source. In order to obtain images with high clarity and high contrast, the LED light source can extract accurate features of the target in a complex environment, improve the accuracy of target recognition and positioning, and lay a solid foundation for subsequent target positioning and recognition. The visual positioning system collects the tube hole images for a long time, which is the primary condition for the system to ensure the accuracy of recognition and positioning.

[0094] The water chamber camera 3 takes pictures of the water chamber tube sheet to determine the tube hole distribution and establish a tube sheet coordinate system. Under the tube sheet coordinate system, the initial pose, inner angle, tool angle, and outer angle of the positioner are calculated in sequence.

[0095] The software part mainly includes image processing, round hole recognition, feature extraction, and stereo matching, including grayscale conversion, filtering, feature extraction, and stereo matching. One of the main tasks of the positioner accuracy correction and zero position calibration system is that the internal lighting conditions of the nuclear power plant evaporator are poor and there is not enough light to complete the collection of tube hole images. Therefore, we need to select suitable lighting equipment to meet the requirements of enhancing the edge clarity of the target to be measured, eliminating shadows, and offsetting noise light. The collected images are transmitted to the computer for image processing through the communication interface. The collected images are preprocessed, and the round holes are recognized using the Hough transform. Finally, the center coordinates of the round holes are calculated based on the internal and external parameters of the camera and the principle of three-dimensional reconstruction.

[0096] The positioner camera 25 is installed on the positioner 2. The internal lighting of the nuclear power plant is uneven, and there will be a large difference between the images collected by the positioner camera 25 and the real pictures. If the directly collected pictures are used for processing, inaccurate experimental results will be produced, affecting the accuracy of the recognition and positioning of the final heat transfer tube holes. Therefore, it is necessary to perform grayscale processing, filtering processing, and edge detection on the obtained pictures. Finally, the center position of the circle is determined, and the accuracy compensation work is carried out.

[0097] In addition, as Figure 9 shown, the present application also provides a method for positioner accuracy correction and zero position calibration, including the following steps:

[0098] Step 1: As shown in Figure 3 shown, install the positioner 2 on the tube sheet 1, install the water chamber camera 3 in the water chamber, and the water chamber camera is fixed in the water chamber by the electromagnet 4 below. The water chamber camera can complete the shooting of the entire tube sheet 1 and the positioner 2.

[0099] The locator camera 25 can photograph the holes of the evaporator heat transfer tubes, and the tool camera 26 observes the alignment of the tool 24 with the heat transfer tubes. After the locator is installed on the steam generator tube sheet, before the locator crawls automatically on the tube sheet, it is necessary to determine the zero position of the locator so as to perform 100% full inspection of all heat transfer tubes through path planning and have an effective anti-collision strategy planning during the whole positioning process. Before the locator starts its formal movement, it first performs the initialization settings of its various motors.

[0100] Step 2: Fix the water chamber camera 3 based on the electromagnet 4 and calibrate its relative position with the locator 2. Collect images at multiple angles through the pan-tilt head, perform grayscale conversion, binarization, corrosion, and contour detection to extract the distribution of tube holes, and establish a coordinate system with the upper left tube hole as the origin (determine the x / y axis by screening the contours through the 3σ criterion and analyzing the distribution law). Finally, solve the pose of the locator by combining the spatial relationships of the three 120° straight lines of the inner toes, the tool straight line, and the straight line outside the tail end. Step 2 specifically includes:

[0101] Step 2.1: Place the water chamber camera 3 in the water chamber. Through the electromagnet 4, the water chamber camera 3 is fixed on the water chamber. The pan-tilt head rotates the main body, which is used to realize the movement of the entire pan-tilt head 34, and can realize 360° horizontal rotation and 90° vertical swing of the lens to ensure that the lens can cover all the tube sheet holes. The initial installation position of the water chamber camera 3 is random, so it is necessary to determine the relative position between the water chamber camera 3 and the locator 2. The specific process is as Figure 6 shown.

[0102] Step 2.2: Determine the distribution of tube holes. Determining the distribution of tube holes is the basis for subsequent work. Since this system needs to work in an environment with good lighting conditions, the distribution of tube holes can be determined according to the brightness and darkness of the pictures. First, convert the collected color pictures into grayscale pictures, set a certain grayscale value as the threshold, and perform binarization processing on the images to make the tube sheet 1 become a binarized image. Then use the corrosion operation to expand the black area and make the holes more obvious. Then use the contour detection algorithm provided by OpenCV to select all the black areas on the image. Since there are shadows on the image, it is necessary to remove the contours with larger areas and only retain the contours with smaller areas as tube holes. Although there are a large number of noise points in the detection results and some tube holes are blocked by the robot, most of the tube holes are accurately identified.

[0103] Step 2.3: Establish an image coordinate system. In this system, the point at the upper leftmost corner is taken as the coordinate origin (x0, y0), that is, the point in the first row and first column. Therefore, the robot should not block this point when locating the coordinate origin. First, calculate the geometric centers of all the contours on the image, calculate the nearest distances from each point to other points and save them. Using the 3σ criterion, delete the abnormal distance values and the corresponding contours. Among the remaining points, based on the relative positions with the surrounding points, the distribution types of the tube holes on the tube sheet 1 can be determined, such as regular hexagon distribution, square distribution, triangular distribution, etc. Then, select the point with the smallest row value and column value, that is, the leftmost and uppermost tube hole, as the coordinate origin. Try to draw a straight line passing through this point with an angle between -5 degrees and +5 degrees, calculate the number of tube holes that each straight line can pass through, and select the straight line that can pass through the most tube holes as the x-axis of the image. According to the relative distances dx of the points on the x-axis and the distribution type of the tube holes, the relative distance dy of the points on the y-axis can be inferred.

[0104] Step 2.4: Determine the pose of the locator. Use light to determine the inner position, angle and tool angle of the crawler, and use the outer straight line coated on the surface of the crawler to determine the outer angle. As Figure 7 shown, three straight lines are emitted at the inner toes of the crawler, namely inner toe straight line one 51, inner toe straight line two 52 and inner toe straight line three 53 in sequence, and the included angles are 120° with each other. The tool also emits a tool straight line 54, and an outer straight line 55 is coated at the tail end of the crawler. Figure 7 shows a simplified Figure 5 .

[0105] Determine the inner toe position of the locator. Using the straight line detection algorithm, the analytical expressions of the above three inner toe straight lines are obtained as follows:

[0106] Inner toe straight line one 51: A b x + B b y + C b = 0;

[0107] Inner toe straight line two 52: A g x + B g y + C g = 0;

[0108] Inner toe straight line three 53: A r x + B r y + C r = 0;

[0109] Figure 7 The black point in the figure is the center point of the inner toe, which should be the intersection of the three inner toe straight lines. Therefore, it satisfies the following formula:

[0110]

[0111] In the above formula, (x1, y1) are the coordinates of the center point of the inner toe. Combining with the coordinate origin (x0, y0), the row number n of the inner toe at this time can be calculated. row and the column number n col :

[0112]

[0113] Determine the inner angle θ. According to the slopes of the analytical formulas of the three straight lines emitted by the inner toe, the inner angle θ can be solved. Taking the upward direction of the inner toe straight line 51 as 0°, counterclockwise as positive, and the value range is [0°, 360°).

[0114] Taking the inner toe straight line 51 as an example, record the coordinates of any point on the inner toe straight line 51 as (xb, yb).

[0115]

[0116] Among them, α b ∈(-90°, 90°).

[0117] Similarly, the inner angle θg of the inner toe straight line two and the inner angle θr of the inner toe straight line three can be calculated, and then the average value of the three values is used as the inner angle Since the pipe holes are distributed according to a certain rule and the value of the inner angle belongs to a certain discrete set, the angle value closest to is selected as the final inner angle θ.

[0118] Determine the tool angle β. The straight line analytical formula of the tool straight line emitted by the tool:

[0119] A p x + B p y + C p =0

[0120] Taking the tool straight line horizontally to the right as 0°, record the coordinates of any point on the tool straight line as (x p , y p ), and the tool angle β can be calculated:

[0121]

[0122] Among them, α p ∈(-90°, 90°).

[0123] Determine the outer angle α. Apply an outer straight line at the end of the crawler, use the same method as above to identify the outer straight line, take the midpoint of the outer straight line, with coordinates (x2, y2), and use the coordinates (x1, y1) of the toe center point to calculate the outer angle α of the crawler.

[0124]

[0125] Step 3: Use the double cameras of the water chamber camera and the locator camera to take two images of the same heat transfer tube hole at different angles. The water chamber camera first locates the position of the locator through the main laser emitter. Through the movement of the pan-tilt 34, the camera completes the measurement of the installation position of the locator, and then the relative coordinate position between the locator and the evaporator water chamber can be determined. Then, the locator camera takes two different images of the same target at the same time at different angles to obtain the parallax. Combining the obtained parallax with the principle of three-dimensional reconstruction can accurately obtain the actual spatial coordinates of the target.

[0126] Step 4: Further use the water chamber camera to obtain the two-dimensional coordinates of the center of the heat transfer tube hole. The water chamber camera is installed perpendicular to the tube sheet, and its position relative to the claw of the locator is fixed. The coordinates of the heat transfer tube hole captured by the water chamber camera are fed back to the control center of the locator for error analysis. The control center then gives the required compensation value to the motors in the turntable, the sliding table and the tool to execute, so that the positioning robot can obtain the required accuracy.

[0127] Step 5: The locator camera is installed on the locator. The internal illumination of the nuclear power plant is uneven, and there will be a large difference between the images captured by the locator camera and the real pictures. If the directly captured pictures are used for processing, inaccurate experimental results will be produced, affecting the accuracy of the recognition and positioning of the final heat transfer tube hole image. Therefore, it is necessary to perform grayscale processing, filtering processing, and edge detection on the obtained pictures. Finally, determine the center position and perform the accuracy compensation work.

[0128] The above are only the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered by the protection scope of the present application.

Claims

1. A positioning device accuracy correction and zero position calibration system, characterized in that It includes a locator (2), a water chamber camera (3) arranged in the water chamber, and a host computer and a control box arranged outside the water chamber; The locator (2) includes a slide table (21), a turntable (22), a base (23), a tool (24), a locator camera (25), and a tool camera (26). The turntable (22) is installed on the base (23), and the base (23) is installed on the slide table (21). The locator camera (25) is used to photograph the tube holes of the evaporator heat transfer tubes, and the tool camera (26) is used to observe the hole alignment situation between the tool (24) and the heat transfer tubes; The water chamber camera (3) includes an LED lamp (31), a lens (33), and a pan-tilt head (34). The LED lamp (31) is arranged below the pan-tilt head fixing seat (37), and the lens (33) and the pan-tilt head (34) are installed on the pan-tilt head fixing seat (37).

2. The locator accuracy correction and zero position calibration system according to claim 1, wherein The control box includes a controller, a driver, a lower computer, an I / O module, a power supply, and a video server.

3. The locator accuracy correction and zero position calibration system according to claim 1, characterized in that The locator camera (25) includes an embedded LED lamp (251) and a locator camera lens (252). The locator camera lens (252) is located at the center, and the embedded LED lamps (251) are evenly distributed circumferentially around the locator camera lens (252).

4. The locator accuracy correction and zero position calibration system according to claim 1, characterized in that The LED lamp (31) is installed on an LED lamp fixing seat (32). An LED lamp cover (36) is provided on the LED lamp (31), and a camera cover (35) is provided on the lens (33).

5. The locator accuracy correction and zero position calibration system according to claim 1, characterized in that The number of the LED lamps (31) is 3, and they are arranged in a triangle.

6. A method for correcting the accuracy and calibrating the zero position of a locator, characterized in that, It includes: Step 1: Install the locator (2) on the tube sheet (1), and install the water chamber camera (3) in the water chamber. The water chamber camera (3) photographs the entire tube sheet (1) and the locator (2); Step 2: Fix the water chamber camera (3) based on the electromagnet (4) and calibrate its relative position with the locator (2). Collect images at multiple angles through the pan-tilt head (34). After graying, binarization, corrosion, and contour detection, extract the tube hole distribution. Establish a coordinate system with the upper left tube hole as the origin, and solve the pose of the locator by combining the spatial relationships of the three 120° straight lines of the inner toes, the tool straight line, and the straight line outside the tail end; Step 3: The dual cameras determine the relative coordinates through laser positioning and pan-tilt head adjustment. Utilize the image parallax at different angles and the three-dimensional reconstruction technology to obtain the actual spatial coordinates of the heat transfer tube holes; Step 4: Vertically install the water chamber camera (3) to obtain the two-dimensional coordinates of the tube hole centers and feedback them to the control center for error analysis; Step 5: The images collected by the locator camera (25) need to be preprocessed through graying, filtering, and edge detection. After eliminating interference, accurately identify the center position to complete the final accuracy compensation.

7. The method for correcting the accuracy of the locator and calibrating the zero position according to claim 1, characterized in that, Step 2 specifically includes: Step 2.1: Fix the water chamber camera (3) inside the water chamber through the electromagnet (4). Use the pan-tilt head to achieve 360° horizontal rotation and 90° vertical swing of the lens, covering the entire field of view of the tube sheet holes, and calibrate to determine its random initial relative position with the locator (2); Step 2.2: Based on the lighting conditions, the collected color image is grayscale processed and binarized. After enhancing the hole features through erosion operation, small-area black regions are detected and screened to identify the distribution of tube holes, large shadow interference is excluded, and the positions of most tube holes are extracted; Step 2.3: Taking the unobscured tube hole in the upper left corner as the coordinate origin, abnormal contour points are removed by the 3σ criterion and the geometric center distances are analyzed to determine the type of tube hole distribution. The optimal straight line is selected to determine the x-axis direction, and the y-axis distance dy is deduced in combination with the distribution law and the x-axis distance dx to complete the construction of the image coordinate system; Step 2.4: Through three positioning straight lines and a tool straight line emitted by the inner toes of the crawler, which are mutually at an angle of 120°, and combined with the straight line painted on the outer side of the tail end, the spatial angles and position relationships of the respective light rays are detected, and the inner positioning coordinates, the inner and outer deflection angles, and the tool angles of the positioner 2 are solved, so as to determine its pose.

8. The method for correcting the locator accuracy and calibrating the zero position according to claim 7, characterized in that, Step 2.2 includes: Determine the distribution of tube holes, and determine the distribution of tube holes according to the brightness and darkness on the picture; Convert the collected color picture into a grayscale picture, set a certain grayscale value as the threshold, and perform binarization processing on the image to make the tube sheet (1) become a binarized image; Use erosion operation to expand the black area, and use the contour detection algorithm provided by OpenCV to select all the black regions on the image; Eliminate the contours with larger areas, and retain the contours with smaller areas as tube holes.

9. The method for correcting the accuracy and calibrating the zero position of the locator according to claim 7, characterized in that, Step 2.3 includes: Establish an image coordinate system, and take the point in the upper leftmost corner as the coordinate origin; Calculate the geometric centers of all the contours on the image, calculate the nearest distances from each point to other points and save them; Use the 3σ criterion to delete the abnormal distance values and the corresponding contours; among the remaining points, use the relative positions with the surrounding points to determine the distribution type of the tube holes on the tube sheet; Select the point with the smallest row value and column value as the coordinate origin, draw a straight line passing through this point with an angle between -5 degrees and +5 degrees, calculate the number of tube holes that each straight line can pass through, select the straight line that can pass through the most tube holes as the image x-axis, and infer the relative distance dy of each point on the y-axis according to the relative distances dx of the points on the x-axis and the distribution type of the tube holes.

10. The method for correcting the accuracy of the locator and calibrating the zero position according to claim 7, characterized in that, Step 2.4 includes: Determine the pose of the positioner, use light rays to determine the inner position, angle and tool angle of the crawler, use the outer straight line painted on the surface of the crawler to determine the outer angle, the inner toes of the crawler emit three straight lines, namely inner toe straight line one, inner toe straight line two and inner toe straight line three, and the included angles are 120° with each other, the tool emits a tool straight line, and a straight line is painted on the tail end of the crawler; Determine the inner toe position of the positioner, and use the straight line detection algorithm to obtain the analytical formulas of the three inner toe straight lines as follows: Inner toe straight line one: A b x + B b y + C b = 0; Inner toe straight line two: A g x + B g y + C g = 0; Inner toe straight line three: A r x + B r y + C r = 0; The intersection point of the three inner toe straight lines satisfies: Where (x1, y1) are the coordinates of the center point of the inner toe. Combining with the coordinate origin (x0, y0), the row number n of the inner toe at this time is calculated row and the column number xcol : Determine the inner angle θ, and solve the inner angle θ according to the slopes of the analytical formulas of the three straight lines emitted by the inner toes. Taking the upward direction of the inner toe straight line one as 0°, counterclockwise is positive, and the value range is [0°, 360°); Taking the inner toe straight line one as an example, record the coordinates of any point on the inner toe straight line one as (xb, yb); Among them, α b ∈(-90°, 90°); Calculate θ separately b , θ g and θ r , θ b is the inner toe straight line - inner side angle θ, θ g is the inner toe straight line two inner side angle θ, θ r Inner toe straight line three inner side angle θ, and take the average value of the three values as the inner side angle Select the angle value closest to The final inner side angle θ; Determine the tool angle β, and the straight line analytical formula of the tool straight line emitted by the tool: A p x + B p y + C p = 0 Taking the horizontal right direction of the tool straight line as 0°, and denoting the coordinates of any point on the tool straight line as (x p , y p ), the tool angle β is calculated as follows: wherein, α p ∈(-90°, 90°); Determine the outer angle α, draw an outer straight line at the tail end of the crawler, identify the outer straight line, take the midpoint of the outer straight line, with coordinates (x2, y2), and use the coordinates (x1, y1) of the toe center point to calculate: In the formula, α is the outer angle of the crawler.

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