Numerical control measuring device and control method for large LNG storage tank gas lift jack

Abstract

The invention relates to a control method of a numerical control measuring device for a large LNG storage tank gas lift top, and the method specifically comprises the steps: (1) a measuring unit is installed on a tank wall, a follow-up camera is installed on the tank top, the measuring unit comprises a horizontal first rotary table, a vertical second rotary table and a laser range finder, and the emission point of the laser range finder is located at the intersection point of the rotation axes of the two rotary tables; the unit origin is measured; (2) the distance between the target point and the original point of the measuring unit can be obtained by using light spots emitted by the laser range finder; (3) shooting the target point and the light spot by using a camera to ensure that the two are within the shooting range of the camera; (4) rotating the first turntable and the second turntable according to the pixel distance between the target point on the image and the light spot to ensure that the light spot is accurately aligned with the target point; (5) along with the rising of the tank top, the position of the target point changes; and (6) repeating the steps (3-4) to ensure that the light spot is continuously aligned with the target point.

Description

Technical Field

[0001] The invention relates to the technical field of engineering measurement, and in particular to a device and a control method for numerically controlling measurement of target points on the tank top surface by using a laser rangefinder during the gas lifting process of a large LNG storage tank. Background Art

[0002] LNG is the abbreviation of liquefied natural gas. As an important energy source, it has received great attention from researchers and developers. With the innovation of new energy technologies and the growing demand for natural gas in the energy field, the demand for the construction of LNG gas tanks is also rising. As a key link in the construction of LNG gas tanks, the tank top installation is completed using gas lifting technology. This technology is difficult and the construction process is risky. When performing gas lifting, a pull rope device is usually used to limit the freedom of the tank top during the lifting process. However, factors that affect the movement of the tank top, such as resistance and air pressure, change continuously as the tank top rises. The combined effect of these factors may cause the tank top to be unbalanced or even fail to gas lift. It can be seen that an accurate detection method is very necessary to obtain the spatial position of the tank top in real time during the gas lifting process.

[0003] To solve this technical problem, a patent document such as Chinese patent application No. 202410260348.8 and publication date 2024.06.14 discloses a tank top balancing device and method for gas lifting of a large LNG cryogenic storage tank, including n pull rope assemblies, n traction machines connected to the n pull rope assemblies in one-to-one correspondence, a balance monitoring module, a communication module and a control module; the n pull rope assemblies are distributed at circumferential angles around the center of gravity of the tank top and are respectively connected to the tank top; the n traction machines are respectively installed on the top of the tank wall; the balance monitoring module is used to monitor the position and posture of the tank top; the control module determines whether the tank top is tilted based on the posture of the tank top, and if it is, calculates the required movement distance of the pull rope assembly near the lowest point of the tank top based on the position and posture of the tank top, outputs a control signal and sends it to the traction machine connected to the pull rope assembly through the communication module, and the traction machine pulls the pull rope assembly connected to it based on the control signal, so that the tank top is restored to a horizontal posture.

[0004] The device described in the above patent document indirectly determines the position of the tank top by measuring the length of the rope. However, since the length of the rope changes when it is subjected to force, the accuracy of the measurement is affected by many factors. In addition, the document does not mention real-time observation of the tank top, so it is impossible to detect slight changes in the tank top in time. During the process of raising the top, the tank top may rotate and deflect, which may cause the position of the target point to change. If the measuring unit device is not adjusted, it is impossible to accurately make the target point and the light spot coincide, which will result in the inability to obtain measurement data of the target point. Summary of the invention

[0005] The purpose of the present invention is to provide a numerical control measuring device and control method for the gas lifting of a large LNG storage tank, which is used to accurately perform numerical control measurement of the target point on the tank top surface by a laser rangefinder during the gas lifting process of a large LNG storage tank. The device adjusts the position and posture of the laser rangefinder in real time to ensure that the light spot emitted by the laser rangefinder coincides with the target point on the tank top surface during the movement of the tank top. Through this method, the spatial position information of the target point can be obtained more accurately, thereby providing a more accurate detection method for the tank top position and movement of the LNG storage tank.

[0006] To achieve the above-mentioned purpose, the present invention proposes a CNC measuring device for the gas lift of a large LNG storage tank, including a measuring unit and a camera. The measuring unit is composed of a two-axis turntable and a laser rangefinder. The two-axis turntable includes a first turntable, a cantilever bracket, a second turntable and a fixed plate. The first turntable is arranged on the top of the tank wall, the cantilever bracket is mounted on the first turntable through a bracket mounting plate, and a second turntable is arranged on the cantilever bracket. The laser rangefinder is mounted on the rotating disk of the second turntable through a fixed plate. The emission point of the laser rangefinder is located at the intersection of the rotation axis of the first turntable and the rotation axis of the second turntable. The first turntable drives the cantilever bracket to rotate in the horizontal direction, and the second turntable drives the laser rangefinder to rotate in the vertical direction. The camera is installed on the tank top and moves with the tank top to take pictures of the light spot and the target point in real time.

[0007] The above structure rotates the first turntable and the second turntable according to the pixel distance between the target point and the light spot on the image captured by the camera, so that the light spot emitted by the laser rangefinder can adjust its position as the target point moves, and always keep the two overlapped.

[0008] Furthermore, a first hollow circular hole is provided at the center of the first turntable, a second hollow circular hole is provided at the center of the second turntable, a measuring hole is provided at the center of the bracket mounting plate, and a measuring rod is provided in the measuring hole. The measuring rod is used to make the rotation axis of the first hollow circular hole coincide with the center axis of the bottom end of the measuring hole; the measuring rod is a cylinder, and the measuring rod is vertically inserted into the measuring hole; the rotation axis of the second hollow circular hole is perpendicular to the center axis of the measuring rod.

[0009] A fine-tuning retaining groove is provided on the bracket mounting plate, and the fine-tuning retaining groove is composed of four elliptical grooves. Four threaded holes are provided on the rotating disk on the first turntable. Bolts pass through the fine-tuning retaining groove and are screwed into the threaded holes, so that the bracket mounting plate is connected to the first turntable, thereby the bracket mounting plate can be adjusted along the length direction of the fine-tuning retaining groove.

[0010] A second fine-tuning retaining groove is also provided on the cantilever bracket, which is composed of three elliptical grooves. Three circular through holes are provided on the second turntable. Bolts pass through the through holes and cooperate with nuts through the fine-tuning retaining grooves, so that the cantilever bracket is connected to the second turntable, so that the cantilever bracket can be adjusted along the length direction of the elliptical groove.

[0011] A fine-tuning retaining groove three is provided on the fixed plate, and the fine-tuning retaining groove is composed of four elliptical grooves. Four threaded holes are provided on the rotating disk on the second turntable. Bolts pass through the fine-tuning retaining groove and are screwed into the threaded holes, so that the fixed plate is connected to the rotating disk on the second turntable, so that the fixed plate can be adjusted along the length direction of the elliptical groove, and a through hole coaxial with the second hollow circular hole is provided on the fixed plate.

[0012] Furthermore, a mounting plate is mounted on the laser rangefinder, on which a fine-tuning retaining groove four is provided, the fine-tuning retaining groove being composed of four elliptical grooves, a mounting hole is provided on the fixed plate, the mounting hole being composed of four threaded holes, a bolt passes through the fine-tuning retaining groove and is screwed into the threaded hole, so that the laser rangefinder is connected to the fixed plate, whereby the laser rangefinder can be adjusted along the length direction of the elliptical groove, and the emission point of the laser rangefinder is located at the intersection of the rotation axis of the second hollow circular hole.

[0013] The above arrangement is to adjust the position of the second turntable in the fine-tuning slot 2 so that its rotation axis intersects with the rotation axis of the first turntable. By adjusting the position of the bracket mounting plate in the fine-tuning slot 1, the position of the fixing plate in the fine-tuning slot 3, and the position of the laser rangefinder in the fine-tuning slot 4, the emission point of the laser rangefinder coincides with the intersection of the first turntable rotation axis and the second turntable rotation axis, ensuring that the position of the emission point does not change when the first turntable and the second turntable rotate.

[0014] The present invention also provides a control method for a numerical control measuring device for gas lift of a large LNG storage tank, the specific steps comprising: (1) A measuring unit is installed on the tank wall, and a camera that moves with the tank top is installed on the tank top. The measuring unit consists of a two-axis turntable and a laser rangefinder, and the laser rangefinder is installed on the two-axis turntable. The two-axis turntable consists of a first turntable that rotates horizontally and a second turntable that rotates vertically. The emission point of the laser rangefinder coincides with the intersection of the rotation axis of the first turntable and the rotation axis of the second turntable.

[0015] (2) The target point is detected by the light spot emitted by the laser rangefinder.

[0016] (3) The target point and the light spot image obtained by the camera are ensured to be within the camera's shooting range. Then, through image processing technology, the coordinates of the light spot and the target point in the pixel coordinate system can be determined from the captured image. In computer graphics, the pixel coordinate system is usually used to describe the position of pixels on the screen. After determining these coordinates, the pixel distance between the light spot and the target point in the pixel coordinate system can be calculated.

[0017] (4) Rotate the first turntable and the second turntable according to the pixel distance between the light spot and the target point.

[0018] (5) When the tank top is lifted, the position of the target point changes as the tank top is lifted.

[0019] (6) Perform steps (3-4) so ​​that the light spot and the target point remain coincident.

[0020] The above method adjusts the emission point of the laser rangefinder to ensure that the emission point of the laser rangefinder is located at the intersection of the rotation axis of the first turntable and the rotation axis of the second turntable, so that the emission point position of the laser rangefinder is not affected by the rotation of the first turntable and the second turntable. Then, according to the image of the light spot emitted by the laser rangefinder and the target point captured by the camera, image processing is performed to obtain the pixel coordinates of the light spot and the target point. Finally, the rotation angle of the first turntable and the second turntable is determined by the hill climbing algorithm, so that the light spot emitted by the laser rangefinder coincides with the target point, thereby completing the detection of the target point on the tank top surface of the LNG gas storage tank.

[0021] Furthermore, step (1) specifically includes adjusting the emission point of the laser rangefinder before setting the measuring unit on the top of the tank wall of the LNG gas storage tank, and the specific steps include: S1 pre-fixes the bracket mounting plate on the rotating disk of the first turntable with bolts, and pre-fixes the second turntable on the cantilever bracket.

[0022] S2 inserts the measuring rod into the measuring hole so that the upper end of the measuring rod corresponds to the second hollow circular hole and the lower end of the measuring rod is located in the first hollow circular hole.

[0023] S3 measures the coaxiality of the cylinder at the bottom end of the measuring rod and the first hollow circular hole by using a measuring tool to ensure that the center axis of the bottom end of the measuring rod coincides with the rotation axis of the first hollow circular hole.

[0024] If the coaxiality is within the allowable deviation range, proceed to step S4.

[0025] S32 If the coaxiality exceeds the allowable deviation range, adjust the bracket mounting plate to ensure that the center axis of the bottom end of the measuring rod coincides with the rotation axis of the first hollow circular hole.

[0026] S4 fixes the bracket mounting plate with bolts.

[0027] S5 measures the measuring rod in the second hollow circular hole by using a measuring tool to ensure that the center axis of the measuring rod is perpendicular to the rotation axis of the second hollow circular hole, and finally ensures that the rotation axis of the first turntable intersects with the rotation axis of the second turntable.

[0028] S51: If the central axis of the measuring rod is perpendicular to the rotation axis of the second hollow circular hole, proceed to step S6.

[0029] S52: if the central axis of the measuring rod is not perpendicular to the rotation axis of the second hollow circular hole, adjusting the second turntable so that the central axis of the measuring rod is perpendicular to the rotation axis of the second hollow circular hole; S6 fixes the second turntable with bolts.

[0030] S7 pre-fixes the fixing plate on the rotating disk of the second turntable.

[0031] S8 measures the through hole and the second hollow circular hole by using a measuring tool to ensure that the axis of the through hole coincides with the axis of rotation of the second hollow circular hole.

[0032] S81 If the through hole axis coincides with the rotation axis of the second hollow circular hole, proceed to step S9.

[0033] S82: If the axis of the through hole does not coincide with the axis of rotation of the second hollow circular hole, the fixing plate is adjusted so that the axis of the through hole coincides with the axis of rotation of the second hollow circular hole.

[0034] S9 fixes the fixing plate with bolts.

[0035] S10 takes out the measuring rod, installs the laser distance meter on the fixing plate and pre-fixes it.

[0036] S101 checks with a measuring tool, and if the emission point of the laser rangefinder is not aligned with the center of the second hollow circular hole and the center of the measuring hole, adjusts the laser rangefinder.

[0037] S102: If the emission point of the laser rangefinder is aligned with the center of the second hollow circular hole and the center of the measuring hole, proceed to step 11.

[0038] S11 fixes the laser rangefinder by means of bolts so that the emission point of the laser rangefinder is located at the intersection of the axis of the first turntable and the axis of the second turntable.

[0039] The above arrangement, by measuring the measuring rod, ultimately ensures that the rotation axis of the first turntable intersects with the rotation axis of the second turntable, so that the emission point of the laser rangefinder is located at the intersection of the two axes.

[0040] Furthermore, step (4) specifically includes: (41) The centroid algorithm is used to calculate the centroid positions of the light spot and the target point to determine the pixel coordinates of the light spot and the target point in the pixel coordinate system.

[0041] (42) A hill climbing algorithm is used to determine the rotation angles of the first turntable and the second turntable so that the pixel distance between the light spot emitted by the laser rangefinder and the target point is less than a given threshold.

[0042] Furthermore, step (41) specifically includes: (411) A camera is used to capture an image containing the light spot and the target point.

[0043] (412) Grayscale processing is performed on the image to convert the image into a grayscale image and remove noise.

[0044] (413) Binarization is applied to the grayscale image to extract the light spot and target point.

[0045] (414) Iterate over each pixel in the binary image.

[0046] (415) The pixel coordinates of the light spot and the target point are determined by a centroid algorithm.

[0047] The above settings facilitate the extraction of pixel coordinates of the light spot and the target point by processing the image captured by the camera.

[0048] Furthermore, the light spot or target point is composed of multiple pixel points, and the centroid algorithm is: .

[0049] Among them, (x i ,y i ) is the x-th row and y-th column coordinate of the pixel point of the light spot or target point in the pixel coordinate system, I i is the grayscale value of the pixel of the light spot or target point, (U, V) is the pixel coordinate of the target point or light spot in the pixel coordinate system, and n is the total number of pixels of the light spot or target point.

[0050] In the above arrangement, the pixel coordinates of the light spot and the target point in the pixel coordinate system are determined by the centroid algorithm, and the first turntable and the second turntable are rotated according to the pixel distance between the light spot and the target point.

[0051] Furthermore, step (42) specifically includes: (421) Establish a pixel coordinate system with the upper left corner as the origin.

[0052] (422) The first turntable and the second turntable are rotated at the minimum step angle of the motor to obtain four light spots.

[0053] (423) Use a camera to capture images of each light spot and target point respectively.

[0054] (424) Calculate the pixel distance between each light spot and the target point respectively.

[0055] (425) Select the light spot with the smallest pixel distance from the target point among the four light spots, and adjust the first turntable and the second turntable according to the position of the light spot so that they reach the predetermined position.

[0056] (426) Repeat steps (422-425) until the pixel distance between the light spot and the target point is less than a set threshold.

[0057] The above arrangement controls the rotation of the first turntable and the second turntable so that the light spot approaches the target point. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a simple schematic diagram of the LNG gas lift measurement system of the present invention.

[0059] Figure 2 It is a schematic diagram of the structure of the measuring unit of the present invention.

[0060] Figure 3 The figure is a schematic diagram of the emission point position of the laser rangefinder of the present invention.

[0061] Figure 4 It is an exploded view of the measuring unit of the present invention.

[0062] Figure 5 This is a flow chart of adjusting the emission point of the laser rangefinder of the present invention.

[0063] Figure 6 It is a schematic diagram of the light spot approaching the target point on the image according to the present invention.

[0064] Figure 7 It is a structural schematic diagram of the laser rangefinder of the present invention.

[0065] Figure 8 This is a flow chart of the light spot control of the present invention. DETAILED DESCRIPTION

[0066] The present invention is further described in detail below in conjunction with specific implementation modes.

[0067] In this embodiment, if Figure 1 As shown, the measuring unit 03 is arranged on the tank wall 01 of the LNG gas storage tank, and the LNG gas storage tank includes the tank wall 01, and a tank top 02 is arranged inside the tank wall 01. The measuring unit 03 is arranged on the top of the tank wall 01, and a camera 04 is arranged on the tank top 02. The camera 04 is aimed at the target point 001 arranged on the tank top 02.

[0068] like Figure 2 and Figure 3 As shown, the measuring unit 03 includes a two-axis turntable and a laser rangefinder 1. The two-axis turntable includes a first turntable 2, a cantilever bracket 3, a second turntable 4 and a fixed plate 5. The first turntable 2 is arranged on the top of the tank wall 01. The cantilever bracket 3 is installed on the first turntable 2 through a bracket mounting plate 31. The second turntable 4 is arranged on the cantilever bracket 3. The laser rangefinder 1 is installed on the rotating disk of the second turntable 4 through a fixed plate 5. The emission point 10 of the laser rangefinder 1 is located at the intersection of the rotation axis 21 of the first turntable 2 and the rotation axis 41 of the second turntable 4. The first turntable 2 drives the cantilever bracket 3 to rotate in the horizontal direction, and the second turntable 4 drives the laser rangefinder 1 to rotate in the vertical direction. In this embodiment, a counterweight block 311 is also included. The counterweight block 311 is arranged at one end of the bracket mounting plate 31 away from the cantilever bracket 3 to prevent the center of the measuring unit 03 from being offset due to the overweight of the cantilever bracket 3.

[0069] The first rotating table 2 and the second rotating table 4 are provided so as to control the laser rangefinder 1 to be adjusted in the horizontal and vertical directions. During the lifting process, the target point 001 moves, and the position of the light spot 002 is adjusted according to the movement.

[0070] like Figure 2 and Figure 4 As shown, a first hollow circular hole 22 is provided at the center of the first turntable 2, a second hollow circular hole 42 is provided at the center of the second turntable 4, a measuring hole 32 is provided at the center of the bracket mounting plate 31, a measuring rod 20 is provided in the measuring hole 32, the rotation axis 21 of the first hollow circular hole 22 coincides with the center axis of the measuring hole 32; the measuring rod 20 is a cylinder, and the center axis of the measuring rod 20 coincides with the center axis of the measuring hole 32; the rotation axis 41 of the second hollow circular hole 42 is perpendicular to the center axis of the measuring rod 20.

[0071] The bracket mounting plate 31 is provided with a fine-tuning retaining groove 33, and the rotating disk of the first turntable 2 is provided with a threaded hole 23. The fine-tuning retaining groove 33 is provided with a bolt 34 (such as Figure 2 As shown in FIG. 1 , the bracket mounting plate 31 is fixed in the threaded hole 23 by a bolt 34. The fine-tuning retaining groove 1 33 is an elliptical groove, and the bracket mounting plate 31 can move along the length direction of the fine-tuning retaining groove 1. In this embodiment, the length direction of the fine-tuning retaining groove 1 is flush with the X-axis direction (as shown in FIG. 1 ). Figure 4 A fine-tuning retaining groove 33 is provided so that the position of the bracket mounting plate 31 can be fine-tuned, thereby ensuring that the center axis of the measuring hole 32 coincides with the rotation axis 21 of the first hollow circular hole 22.

[0072] like Figure 4As shown, the cantilever bracket 3 is further provided with a second fine-tuning retaining groove 35, a circular through hole 44 is provided on the second turntable 4, a bolt 36 is provided in the second fine-tuning retaining groove 35, and the second turntable 4 is connected to the circular through hole 44 by the bolt 36 to achieve fixation, and the second fine-tuning retaining groove 36 is an elliptical groove, and the cantilever bracket 3 can move along the length direction of the elliptical groove. In this embodiment, the length direction of the second fine-tuning retaining groove is flush with the Y-axis direction (such as Figure 4 The second fine-tuning retaining groove 35 is provided so that the position of the second turntable can be fine-tuned, thereby ensuring that the rotation axis 41 of the second hollow circular hole 42 is perpendicular to the center axis of the measuring rod 20.

[0073] like Figure 2 and Figure 4 As shown, a fine-tuning retaining groove 3 51 is provided on the fixing plate 5, a threaded hole 43 is provided on the rotating disk on the second turntable 4, a bolt 52 is provided in the fine-tuning retaining groove 3 51, and the fixing plate 5 is connected to the threaded hole 43 by the bolt 52 to achieve fixation. The fine-tuning retaining groove 3 51 is an elliptical groove, and the fixing plate 5 can move along the length direction of the elliptical groove. A through hole 53 coaxial with the second hollow circular hole 42 is also provided on the fixing plate 5. In this embodiment, the length direction of the fine-tuning retaining groove 3 is flush with the Z-axis direction (i.e., in Figure 4 The fine-tuning retaining groove 3 is provided so that the position of the fixing plate 5 can be fine-tuned, thereby ensuring that the rotation axis 41 of the second hollow circular hole 42 coincides with the center axis of the through hole 53 .

[0074] The measuring rod 20 is provided to ensure that when the laser rangefinder 1 is installed, the emission point 10 of the laser rangefinder 1 can be located at the intersection of the rotation axis 21 of the first turntable 2 and the rotation axis 42 of the second turntable 4, thereby making it possible for the emission point 10 of the laser rangefinder 1 to be located at the intersection of the rotation axis 21 of the first turntable 2 and the rotation axis 41 of the second turntable 4 when the first turntable 2 and the second turntable 4 rotate, so that the position of the emission point 10 of the laser rangefinder 1 is not affected by the rotation of the first turntable 2 and the second turntable 4.

[0075] like Figure 2 , 4 As shown in FIG. 7 , the laser rangefinder 1 is provided with a mounting plate 11, on which a fine-tuning retaining groove 12 is provided, and a threaded hole 54 (in Figure 4 As shown in FIG. 1 ), a bolt 13 is provided in the fine-tuning retaining groove 12 (in Figure 2), the laser rangefinder 1 is fixed in the threaded hole 54 by bolts 13, the fine-tuning retaining groove 14 12 is an elliptical groove, the laser rangefinder 1 can move along the length direction of the elliptical groove, and the emission point 10 of the laser rangefinder 1 is located on the center axis of the through hole 53 of the mounting plate 5. The fine-tuning retaining groove 14 12 is provided so that the position of the laser rangefinder 1 can be fine-tuned, so that the emission point 10 of the laser rangefinder 1 can coincide with the center axis of the through hole 53 of the mounting plate 5, so as to ensure that the emission point 10 of the laser rangefinder 1 is located at the intersection of the rotation axis 21 of the first turntable 2 and the rotation axis 41 of the second turntable 4.

[0076] like Figure 8 As shown, a control method for a numerical control measuring device for gas lifting of a large LNG storage tank is introduced, and the specific steps include: (1) A measuring unit is installed on the tank wall, and a camera that moves with the tank top is installed on the tank top. The measuring unit consists of a two-axis turntable and a laser rangefinder, and the laser rangefinder is installed on the two-axis turntable. The two-axis turntable consists of a first turntable that rotates horizontally and a second turntable that rotates vertically. The emission point of the laser rangefinder coincides with the intersection of the rotation axis of the first turntable and the rotation axis of the second turntable.

[0077] (2) The target point is detected by the light spot emitted by the laser rangefinder.

[0078] (3) The target point and the light spot are captured by the camera to ensure that both are within the camera’s shooting range. Then, the coordinates of the light spot and the target point in the pixel coordinate system are determined based on the captured image using image processing technology.

[0079] (4) Rotate the first turntable and the second turntable according to the pixel distance between the light spot and the target point.

[0080] (5) When the tank top is lifted, the position of the target point changes as the tank top is lifted.

[0081] (6) Perform step (4) so ​​that the light spot and the target point remain coincident.

[0082] like Figure 5 As shown, the specific steps of adjusting the emission point of the laser rangefinder in step (1) include: S1 pre-fixes the bracket mounting plate on the rotating disk of the first turntable with bolts, and pre-fixes the second turntable on the cantilever bracket.

[0083] S2 inserts the measuring rod into the measuring hole so that the upper end of the measuring rod corresponds to the second hollow circular hole and the lower end of the measuring rod is located in the first hollow circular hole.

[0084] S3 measures the coaxiality of the cylinder at the bottom end of the measuring rod and the first hollow circular hole by using a measuring tool to ensure that the center axis of the bottom end of the measuring rod coincides with the rotation axis of the first hollow circular hole.

[0085] If the coaxiality is within the allowable deviation range, proceed to step S4.

[0086] S32 If the coaxiality exceeds the allowable deviation range, adjust the bracket mounting plate to ensure that the center axis of the bottom end of the measuring rod coincides with the rotation axis of the first hollow circular hole.

[0087] S4 fixes the bracket mounting plate with bolts.

[0088] S5 measures the measuring rod in the second hollow circular hole by using a measuring tool to ensure that the center axis of the measuring rod is perpendicular to the rotation axis of the second hollow circular hole, and finally ensures that the rotation axis of the first turntable intersects with the rotation axis of the second turntable.

[0089] S51: If the central axis of the measuring rod is perpendicular to the rotation axis of the second hollow circular hole, proceed to step S6.

[0090] S52: if the central axis of the measuring rod is not perpendicular to the rotation axis of the second hollow circular hole, adjusting the second turntable so that the central axis of the measuring rod is perpendicular to the rotation axis of the second hollow circular hole; S6 fixes the second turntable with bolts.

[0091] S7 pre-fixes the fixing plate on the rotating disk of the second turntable.

[0092] S8 measures the through hole and the second hollow circular hole by using a measuring tool to ensure that the axis of the through hole coincides with the axis of rotation of the second hollow circular hole.

[0093] S81 If the through hole axis coincides with the rotation axis of the second hollow circular hole, proceed to step S9.

[0094] S82: If the axis of the through hole does not coincide with the axis of rotation of the second hollow circular hole, the fixing plate is adjusted so that the axis of the through hole coincides with the axis of rotation of the second hollow circular hole.

[0095] S9 fixes the fixing plate with bolts.

[0096] S10 takes out the measuring rod, installs the laser distance meter on the fixing plate and pre-fixes it.

[0097] S101 checks with a measuring tool, and if the emission point of the laser rangefinder is not aligned with the center of the second hollow circular hole and the center of the measuring hole, adjusts the laser rangefinder.

[0098] S102: If the emission point of the laser rangefinder is aligned with the center of the second hollow circular hole and the center of the measuring hole, proceed to step 11.

[0099] S11 fixes the laser rangefinder by means of bolts so that the emission point of the laser rangefinder is located at the intersection of the axis of the first turntable and the axis of the second turntable.

[0100] In this embodiment, the measuring tool includes a tool that can be used to measure the concentricity, coaxiality or center point of the shaft and the hole, such as a micrometer, which is a prior art and will not be described in detail here.

[0101] By measuring the measuring rod, it is ensured that the emission point of the laser rangefinder is accurately located at the intersection of the first turntable rotation axis and the second turntable rotation axis.

[0102] Step (4) specifically includes: (41) The centroid algorithm is used to calculate the centroid positions of the light spot and the target point to determine the pixel coordinates of the light spot and the target point in the pixel coordinate system.

[0103] (42) A hill climbing algorithm is used to determine the rotation angles of the first turntable and the second turntable so that the pixel distance between the light spot emitted by the laser rangefinder and the target point is less than a given threshold.

[0104] Step (41) specifically includes: (411) A camera is used to capture an image containing the light spot and the target point.

[0105] (412) Grayscale processing is performed on the image to convert the image into a grayscale image and remove noise.

[0106] (413) Binarization processing is applied to the grayscale image to extract the spot area and target point.

[0107] (414) Iterate over each pixel in the binary image.

[0108] (415) The pixel coordinates of the light spot and the target point are determined by the centroid algorithm.

[0109] The above settings facilitate the extraction of pixel coordinates of the light spot and the target point by processing the image captured by the camera.

[0110] Furthermore, the light spot or target point is composed of multiple pixel points, and the centroid algorithm is: .

[0111] Among them, (x i ,y i ) is the coordinate of the pixel of the light spot or target point in the xth row and yth column in the pixel coordinate system, I iis the grayscale value of the pixel of the light spot or target point, (U, V) is the pixel coordinate of the target point or light spot in the pixel coordinate system, and n is the total number of pixels of the light spot or target point.

[0112] By calculating the pixel distance between the light spot and the target point, it is convenient to control the first turntable and the second turntable through the hill climbing algorithm.

[0113] In this embodiment, the Hill Climbing Algorithm is a simple optimization algorithm used to solve the optimization problem. It adopts a greedy strategy, starting from the current solution, and gradually moving to the next better solution until a local optimal solution is reached.

[0114] like Figure 6 As shown, step (42) specifically includes: (421) Establish a pixel coordinate system with the upper left corner as the origin.

[0115] (422) Assume that the minimum step angle of the first turntable is θ1, and the minimum step angle of the second turntable is θ2. Control the two turntables to rotate according to their respective minimum step angles, and obtain four light spots: Light spot 1, the first turntable angle is 0, and the second turntable angle is θ2.

[0116] Light spot 2, the first turntable angle is 0, and the second turntable angle is -θ2.

[0117] Light spot 3, the first turntable angle is θ1, and the second turntable angle is 0.

[0118] Light spot 4, the first turntable angle is -θ1, and the second turntable angle is 0.

[0119] (423) Use a camera to capture images of each light spot and target point respectively.

[0120] (424) Calculate the pixel distance between each light spot and the target point.

[0121] .

[0122] Among them (U i ,V i ), i=1,2,3,4 represents the pixel coordinates of spot i; D i , i=1,2,3,4, represents the pixel distance from the light spot i to the target point.

[0123] (425) Select the optimal direction: Find D i The minimum value in and its corresponding spot D b Then, control the first turntable or the second turntable to rotate so that the light spot moves to D b Location.

[0124] (426) Repeat steps (422-425) until the pixel distance between the light spot and the target point is less than a set threshold.

[0125] The rotation angles of the first turntable and the second turntable are determined by the above settings and the hill climbing algorithm so that the light spot coincides with the target point.

[0126] The working principle of the present invention is: by adjusting the emission point of the laser rangefinder, ensure that the emission point of the laser rangefinder is located at the intersection of the rotation axis of the first turntable and the rotation axis of the second turntable, so that the emission point position of the laser rangefinder is not affected by the rotation of the first turntable and the second turntable. Then, according to the image of the light spot emitted by the laser rangefinder and the target point captured by the camera, image processing is then performed to obtain the pixel coordinates of the light spot and the target point. Finally, the rotation angle of the first turntable and the second turntable is determined by the hill climbing algorithm, so that the light spot emitted by the laser rangefinder coincides with the target point, thereby completing the detection of the target point on the tank top surface of the LNG gas storage tank.

Claims

1. A numerical control measuring device for gas lift of large LNG storage tanks, characterized in that: The measuring unit comprises a two-axis turntable, which comprises a first turntable, a cantilever bracket, a second turntable and a fixing plate. The first turntable is arranged on the top of the tank wall, the cantilever bracket is mounted on the first turntable through a bracket mounting plate, a second turntable is arranged on the cantilever bracket, the laser rangefinder is mounted on a rotating disk of the second turntable through a fixing plate, and an emission point of the laser rangefinder is located at the intersection of the central axes of the rotating disks of the first turntable and the second turntable; the first turntable drives the cantilever bracket to rotate in a horizontal direction, and the second turntable drives the laser rangefinder to rotate in a vertical direction; the camera is mounted on the tank top and moves with the tank top, and is used to take pictures of the light spot and the target point in real time.

2. A numerical control measuring device for gas lift of large LNG storage tanks according to claim 1, characterized in that: A first fine-tuning retaining groove is provided on the bracket mounting plate, and the fine-tuning retaining groove is composed of four elliptical grooves. Four threaded holes are provided on the rotating disk on the first turntable. Bolts pass through the fine-tuning retaining groove and are screwed into the threaded holes, so that the bracket mounting plate is connected to the first turntable, thereby the bracket mounting plate can be adjusted along the length direction of the fine-tuning retaining groove; The cantilever bracket is also provided with a second fine-tuning retaining groove, which is composed of three elliptical grooves. Three circular through holes are provided on the second turntable. Bolts pass through the through holes and through the fine-tuning retaining grooves, so that the cantilever bracket is connected to the second turntable, so that the cantilever bracket can be adjusted along the length direction of the elliptical grooves. A fine-tuning retaining groove three is provided on the fixed plate, and the fine-tuning retaining groove is composed of four elliptical grooves. Four threaded holes are provided on the rotating disk on the second turntable. Bolts pass through the fine-tuning retaining groove and are screwed into the threaded holes, so that the fixed plate is connected to the rotating disk on the second turntable, so that the fixed plate can be adjusted along the length direction of the elliptical groove, and a through hole coaxial with the second hollow circular hole is provided on the fixed plate.

3. A numerical control measuring device for gas lift of large LNG storage tanks according to claim 2, characterized in that: The laser rangefinder is equipped with a mounting plate, on which a fine-tuning retaining groove four is provided, the fine-tuning retaining groove is composed of four elliptical grooves, a mounting hole is provided on the fixed plate, the mounting hole is composed of four threaded holes, a bolt passes through the fine-tuning retaining groove and is screwed into the threaded hole, so that the laser rangefinder is connected to the fixed plate, thereby the laser rangefinder can be adjusted along the length direction of the elliptical groove, and the emission point of the laser rangefinder is located at the intersection of the rotation axis of the second hollow circular hole.

4. A control method for a numerical control measuring device for gas lift of a large LNG storage tank according to any one of claims 1 to 3, characterized in that: The specific steps include: (1) The emission point of the laser rangefinder is adjusted, and a camera that moves with the tank top is installed on the tank top; the measuring unit consists of a two-axis turntable and a laser rangefinder, and the laser rangefinder is installed on the two-axis turntable; the two-axis turntable consists of a first turntable that rotates horizontally and a second turntable that rotates vertically, and the emission point of the laser rangefinder coincides with the intersection of the axis of the first turntable and the axis of the second turntable; (2) Detect the target point through the light spot emitted by the laser rangefinder; (3) The target point and light spot images obtained by the camera are ensured to be within the camera's shooting range; then, the coordinates of the light spot and target point in the pixel coordinate system are determined based on the captured images through image processing technology; (4) rotating the first turntable and the second turntable according to the pixel distance between the light spot and the target point; (5) When the tank top is lifted, the position of the target point changes as the tank top is lifted; (6) Perform step (4) so ​​that the light spot and the target point remain coincident.

5. The control method of a numerical control measuring device for gas lift of a large LNG storage tank according to claim 4, characterized in that: The specific steps of adjusting the emission point of the laser rangefinder in step (1) include: S1 pre-fixes the bracket mounting plate on the rotating disk of the first turntable with bolts, and pre-fixes the second turntable on the cantilever bracket; S2 inserts the measuring rod into the measuring hole so that the upper end of the measuring rod corresponds to the second hollow circular hole and the lower end of the measuring rod is located in the first hollow circular hole; S3: measuring the coaxiality of the cylinder at the bottom end of the measuring rod and the first hollow circular hole by using a measuring tool to ensure that the center axis of the bottom end of the measuring rod coincides with the rotation axis of the first hollow circular hole; If the coaxiality is within the allowable deviation range, proceed to step S4; S32 If the coaxiality exceeds the allowable deviation range, adjust the bracket mounting plate to ensure that the center axis of the bottom end of the measuring rod coincides with the rotation axis of the first hollow circular hole; S4 fixes the bracket mounting plate with bolts; S5: measuring the measuring rod in the second hollow circular hole by using a measuring tool to ensure that the center axis of the measuring rod is perpendicular to the rotation axis of the second hollow circular hole, and finally ensuring that the rotation axis of the first turntable intersects with the rotation axis of the second turntable; S51: If the central axis of the measuring rod is perpendicular to the rotation axis of the second hollow circular hole, proceed to step S6; S52: if the central axis of the measuring rod is not perpendicular to the rotation axis of the second hollow circular hole, adjusting the second turntable so that the central axis of the measuring rod is perpendicular to the rotation axis of the second hollow circular hole; S6 fixes the second turntable with bolts; S7 pre-fixes the fixing plate on the rotating disk of the second turntable; S8: measuring the through hole and the second hollow circular hole by using a measuring tool to ensure that the axis of the through hole coincides with the axis of rotation of the second hollow circular hole; S81: If the through hole axis coincides with the rotation axis of the second hollow circular hole, proceed to step S9; S82: if the axis of the through hole and the axis of rotation of the second hollow circular hole do not coincide with each other, adjusting the fixing plate so that the axis of the through hole and the axis of rotation of the second hollow circular hole coincide with each other; S9 fixes the fixing plate with bolts; S10 takes out the measuring rod, installs the laser distance meter on the fixing plate and performs pre-fixation; S101 uses a measuring tool to check, and if the emission point of the laser rangefinder is not aligned with the center of the second hollow circular hole and the center of the measuring hole, the laser rangefinder is adjusted; S102: If the center of the second hollow circular hole of the laser rangefinder is aligned with the center of the measuring hole, proceed to step 11; S11 fixes the laser rangefinder by means of bolts, so that the emission point of the laser rangefinder is located at the intersection of the rotation axis of the first turntable and the rotation axis of the second turntable.

6. The control method of a numerical control measuring device for gas lift of a large LNG storage tank according to claim 4, characterized in that: Step (4) specifically includes: (41) Calculate the centroid positions of the light spot and the target point using a centroid algorithm to determine the pixel coordinates of the light spot and the target point in a pixel coordinate system; (42) A hill climbing algorithm is used to determine the rotation angles of the first turntable and the second turntable so that the distance between the light spot emitted by the laser rangefinder and the target point is less than a given threshold.

7. The control method of a numerical control measuring device for gas lift of a large LNG storage tank according to claim 6, characterized in that: Step (41) specifically comprises: (411) using a camera to capture an image containing the light spot and the target point; (412) grayscale processing is performed on the image, so that the image is converted into a grayscale image and noise is removed; (413) applying binarization processing to the grayscale image to extract the spot area and target point; (414) traverse each pixel in the binary image; (415) The pixel coordinates of the light spot and the target point are determined by a centroid algorithm.

8. The control method of a numerical control measuring device for gas lift of a large LNG storage tank according to claim 7, characterized in that: The light spot or target point is composed of multiple pixel points, and the centroid algorithm is: ； Among them, (x i ,y i ) is the coordinate of the pixel of the light spot or target point in the xth row and yth column in the pixel coordinate system, I i is the grayscale value of the pixel of the light spot or target point, (U, V) is the pixel coordinate of the target point or light spot in the pixel coordinate system, and n is the total number of pixels of the light spot or target point.

9. The control method of a numerical control measuring device for gas lift of a large LNG storage tank according to claim 6, characterized in that: Step (42) specifically includes: (421) Establishing a pixel coordinate system with the upper left corner as the origin; (422) rotating the first turntable and the second turntable at the minimum step angle of the motor to obtain four light spots; (423) using a camera to capture images of each light spot and target point respectively; (424) respectively calculating the pixel distance between each light spot and the target point; (425) selecting the light spot with the smallest pixel distance from the target point among the four light spots, and adjusting the first turntable and the second turntable according to the position of the light spot so that they reach the predetermined position; (426) Repeat steps (422-425) until the pixel distance between the light spot and the target point is less than a set threshold.

Images