A cryogenic loading and unloading conveyor system docking method and apparatus

Abstract

The present application belongs to the technical field of oil and gas exploration and development, and relates to a low-temperature loading and unloading conveying system docking method and device, comprising: when the tank truck enters the working area, the tank truck is roughly positioned to preliminarily determine the tank opening position of the tank truck; the tank opening is photographed at the tank opening position to obtain a tank opening image; the tank opening image is input into an image edge detection algorithm model to obtain an edge image of the tank opening; the edge image is corrected through orthogonal scanning to obtain the center coordinates of the tank opening; the center coordinates are compared with the center position of the fluid loading and unloading arm to obtain the deviation amount of the two; the fluid loading and unloading arm is driven to move according to the deviation amount; when the center coordinates and the center position of the fluid loading and unloading arm completely coincide, the docking operation is completed, and the fluid loading and unloading arm is lowered by the lifting hydraulic cylinder. The present application can realize the automatic centering, lowering and retracting of the loading and unloading arm and the pipe opening, thereby eliminating the labor of the person during the loading process and reducing the harm to the person caused by possible safety hazards.

Description

Technical Field

[0001] This invention relates to a docking method and apparatus for a cryogenic loading and unloading transportation system, belonging to the field of oil and gas exploration and development technology. Background Technology

[0002] A floating production storage and offloading unit (FLNG) is a floating production facility used for offshore gas field development. Positioned at sea via a mooring system, it performs the functions of extracting, processing, liquefying, storing, and loading / unloading natural gas. Used in conjunction with LNG carriers, it enables the extraction and transportation of natural gas from offshore gas fields. Utilizing FLNG for offshore gas field development breaks the single mode of relying solely on pipeline transportation, saving transportation costs and not occupying onshore space. Furthermore, FLNG can be reused after the gas field is completed, being placed in other gas fields, resulting in high economic efficiency.

[0003] An LNG unloading boom is a rigid, articulated piping system installed on a dock or for unloading FLNG (Frequency-to-LNG). Its main structure includes a rotary joint, outer boom, inner boom, base riser, and the rotary joint connecting the inner boom and base riser. When an LNG carrier arrives at the dedicated terminal, the LNG is pumped into the terminal's storage tanks via the liquid phase unloading boom and unloading pipeline, using cryogenic pumps on board. Simultaneously, the boil-off gas (BOG) in the storage tanks returns to the LNG carrier via a return gas pipeline and a gaseous return boom. During operation, a traction line guides the end of the unloading boom to the LNG carrier's receiving end for accurate docking under relative motion. The hydraulic system controlling the unloading boom is designed to withstand the speed and acceleration effects caused by the ship's movement.

[0004] LNG transportation on land typically utilizes tank trucks, requiring the LNG unloading boom's nozzle to connect with the tank truck's opening. Due to the complex loading and unloading environment of LNG tank workshops, extremely high demands are placed on the structural characteristics and control performance of the loading boom for intermediate transfer operations. The boom system must possess stability and flexibility to adapt to changes in external loads during operation, ultimately ensuring safe and stable LNG transfer. This working principle also applies to onshore liquid hydrogen loading and unloading skid technology.

[0005] The docking of LNG positioning loading arms is typically done manually, which is inefficient. Currently, the operation relies heavily on manual intervention. Workers operate the loading arm to complete the docking by closely observing the positional relationship between the loading arm and the tanker truck. This method is labor-intensive, inefficient, and the liquefied natural gas inside the pipeline is under high pressure and at low temperature. The entire process currently requires manual operation, which is repetitive and prone to causing visual fatigue. Furthermore, manual operation poses certain safety hazards.

[0006] Existing automated positioning loading and unloading arms typically use industrial cameras as image detection devices for pipe docking. Visual point cloud technology is applied to acquire and process the pipe opening images in real time to determine the center position of the opening. However, this method has high requirements for the working environment; factors such as dust in the air, light intensity, and oil stains on the loading / unloading vehicle can all affect the recognition efficiency and accuracy of the tank opening images. Summary of the Invention

[0007] To address the aforementioned problems, the purpose of this invention is to provide a method and apparatus for docking a cryogenic loading and unloading conveying system, which can minimize human labor during the loading process and reduce potential safety hazards that could harm people.

[0008] To achieve the above objectives, the present invention proposes the following technical solution: a docking method for a cryogenic loading and unloading conveying system, comprising the following steps: after a tank truck enters the working area, the tank truck is coarsely positioned to preliminarily determine the position of the tank opening; a photograph is taken of the tank opening at the tank opening position to obtain a tank opening image; the tank opening image is input into an image edge detection algorithm model to obtain an edge image of the tank opening; the edge image is corrected by orthogonal scanning to obtain the center coordinates of the tank opening; the center coordinates are compared with the center position of the fluid loading and unloading arm to obtain the deviation between the two; the fluid loading and unloading arm is driven to move according to the deviation; when the center coordinates completely coincide with the center position of the fluid loading and unloading arm, the docking operation is completed, and the fluid loading and unloading arm is lowered by a lifting hydraulic cylinder.

[0009] Furthermore, the method for initially determining the tanker opening position of the tanker truck is as follows: setting a threshold limit for the grayscale band; when the scanned grayscale value is continuously lower than the threshold limit, it is determined that the tanker truck has entered the working area, and the continuous area with the grayscale value lower than the threshold limit is identified as the tanker opening area; the center of the tanker opening area is selected as the center coordinate of the coarse positioning.

[0010] Furthermore, the image of the can opening is subjected to image enhancement processing. The image enhancement processing method is as follows: obtaining the gray value of a single pixel in the space of the can opening image; constructing a histogram of gray values ​​based on the gray value of each pixel; and correcting the gray value of the can opening image to [0,100] in the histogram to eliminate the influence of the shadow part inside the can opening.

[0011] Furthermore, the image edge detection algorithm model employs the Canny algorithm with adaptive thresholding. The method for obtaining the edge image of the can opening is as follows: input the can opening image; perform bilateral filtering denoising on the can opening image; calculate the gradient magnitude of the center pixel based on the gradient components in the horizontal, vertical, 45°, and 135° directions of the denoised can opening image; distinguish the can opening from the vehicle body based on the gradient magnitude of the center pixel using the maximum inter-class variance method; and enhance the contrast of the can opening image through histogram normalization to obtain the edge image of the can opening.

[0012] Furthermore, the bilateral filtering performs nonlinear filtering by combining pixel similarity and geometric spatial distance. It calculates the weights of pixel similarity and geometric spatial distance using two Gaussian functions, and then performs convolution operation with the original can opening image to output a denoised can opening image. The spatial standard deviation based on the two-dimensional Gaussian function is determined by the radius of the can opening, and the grayscale standard deviation based on the two-dimensional Gaussian function is equal to twice the noise standard deviation of all pixels during the filtering process.

[0013] Furthermore, the gradient magnitude of the center pixel E The calculation formula is:

[0014] in, It is the gradient component in the horizontal direction. It is the gradient component in the vertical direction; It is the gradient component in the 45° direction; It is the gradient component in the 145° direction; the method for distinguishing between the tank opening and the vehicle body is as follows: by using the maximum inter-class variance method, the maximum threshold of pixel values ​​in the image is adaptively obtained; the maximum threshold is used as the high threshold, half of the maximum threshold is used as the low threshold, pixels with pixel values ​​higher than the high threshold are assigned a first gray value, pixels with pixel values ​​lower than the low threshold are assigned a second gray value, and the first gray value is greater than the second gray value.

[0015] Furthermore, the method for correcting the edge image by orthogonal scanning is as follows: the image of the can opening is an incomplete circle, two non-parallel chords are drawn on the incomplete circle, and the perpendicular bisectors of the two chords are drawn respectively. The intersection of the two perpendicular bisectors is the center coordinate of the can opening.

[0016] Furthermore, the formula for calculating the adjustment amount that drives the fluid loading / unloading arm to move based on the aforementioned deviation is as follows: Adjustment value = Deviation × +differential value × +points value×

[0017] The integral value is the sum of the previous integral value and the current deviation; the differential value is the current deviation minus the previous deviation; the deviation is equal to the center position of the center coordinates minus the center position of the fluid loading / unloading arm.

[0018] This invention also discloses a docking device for a cryogenic loading and unloading conveying system, used in any of the above-described cryogenic loading and unloading conveying system docking methods, comprising: a vision unit, a fluid loading and unloading arm alignment control unit, a host computer, and a PLC control system. The vision unit is used to obtain an image of the tank opening of the tank truck and transmit the image to the host computer and the fluid loading and unloading arm alignment control unit. The fluid loading and unloading arm alignment control unit is used to obtain the center position coordinates of the fluid loading and unloading arm based on a displacement sensor, and drive the fluid loading and unloading arm to move according to a drive control signal issued by the PLC control system to complete the alignment of the fluid loading and unloading arm with the tank truck. The host computer is used to calculate the center coordinates of the tank opening based on the image of the tank opening, send control commands to the PLC control system based on the center coordinates of the tank opening, and receive feedback signals from the PLC control system. The PLC control system is used to obtain the deviation between the center coordinates and the center position of the fluid loading and unloading arm, and generate a drive control signal based on the deviation.

[0019] Furthermore, the centering control unit of the fluid loading and unloading arm employs hydraulic servo control, which includes a first oil pump and a second oil pump. The first oil pump supplies oil for the lifting and lowering movement of the loading and unloading arm, and the second oil pump supplies oil for the horizontal movement of the loading and unloading arm. The first and second oil pumps are respectively connected to the oil tank through a first relief valve and a second relief valve. The first oil pump is connected to the vertical drive hydraulic cylinder through a first proportional servo valve and a speed control valve. A first displacement sensor is installed on the vertical drive hydraulic cylinder. The second oil pump is connected to the input end of the horizontal drive hydraulic cylinder through a second proportional servo valve. The output end of the horizontal drive hydraulic cylinder is connected to the input end of the traction crawler. The output end of the traction crawler is connected to the input end of the second displacement sensor. The output end of the second displacement sensor is connected to the input end of a servo amplifier. The output end of the servo amplifier is connected to the second proportional servo valve, forming a loop. The technical solution of the present invention has at least the following technical effects or advantages: 1. This invention avoids the possibility of oil and gas volatilization and leakage during manual docking by automatically docking the pipe openings of the loading and unloading arm, thereby ensuring the safety and reliability of the loading and unloading process.

[0020] 2. This invention can improve the automation level of existing fluid loading and unloading equipment. The implementation process only requires a manual interface to achieve automatic centering of the loading and unloading arm, as well as the lowering and retraction of the arm. This significantly simplifies the loading and unloading operation process, enabling automated loading and unloading of petrochemical products. Simultaneously, using a lifting device to lower the loading and unloading arm can shorten the waiting time for tank trucks, helping to improve the efficiency of petrochemical product loading and unloading and reduce the labor intensity of workers.

[0021] 3. This invention can reduce resource waste caused by transportation and loading / unloading in petrochemical product manufacturing enterprises, thereby reducing the enterprise's operating costs and labor costs, and providing an excellent opportunity for enterprise development. Attached Figure Description

[0022] Figure 1 This is a flowchart of a method for docking a cryogenic loading and unloading conveying system according to an embodiment of the present invention; Figure 2 This is an image of the tank opening of a tanker truck in one embodiment of the present invention; Figure 3 This is an image of the can opening after image enhancement in one embodiment of the present invention; Figure 4 This is a flowchart of an image edge detection algorithm in one embodiment of the present invention. Figure (a) is the image of the tank opening after grayscale correction, and Figure (b) is the grayscale histogram. Figure 5 Figure (a) is a schematic diagram of a can opening image after bilateral filtering in one embodiment of the present invention; Figure (b) is a can opening image with added salt and pepper filtering; Figure (c) is a can opening image after Gaussian filtering; Figure (d) is a can opening image after bilateral filtering. Figure 6 This is a schematic diagram of the Sobel algorithm template after adding 45° and 135° directions in one embodiment of the present invention; Figure 7 Figure (a) is a comparison of the edge detection results of the method in one embodiment of the present invention with the traditional Canny algorithm and Soble algorithm. Figure (b) is the first can opening image, and Figure (c) is the second can opening image. Figure 8 This is a schematic diagram illustrating the principle of the orthogonal scanning method in one embodiment of the present invention; Figure 9 This is a schematic diagram of the docking device of a cryogenic loading and unloading conveying system in one embodiment of the present invention; Figure 10 This is a schematic diagram of the drive module of the fluid loading and unloading arm in one embodiment of the present invention; Figure 11 This is a schematic diagram of a hydraulic servo control method for a fluid loading / unloading arm in one embodiment of the present invention; Detailed Implementation To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in detail through specific embodiments. However, it should be understood that the specific embodiments are provided only for a better understanding of the present invention and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terminology used is for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] To address the issue that existing technologies using visual point cloud technology to acquire and process camera-captured pipe opening images in real time are subject to high environmental requirements at the work site, such as dust in the air, light intensity, and oil stains on the loading and unloading vehicle, resulting in low recognition efficiency and poor accuracy of tank opening images, this invention proposes a docking method and apparatus for a cryogenic loading and unloading conveying system. The method includes the following steps: after the tank truck enters the work area, coarse positioning of the tank truck is performed to initially determine the position of the tank opening; a photograph is taken of the tank opening at the tank opening position to obtain an image; the tank opening image is input into an image edge detection algorithm model to obtain the edge image of the tank opening; the edge image is corrected through orthogonal scanning to obtain the center coordinates of the tank opening; the center coordinates are compared with the center position of the fluid loading and unloading arm to obtain the deviation between the two; the fluid loading and unloading arm is moved according to the deviation; when the center coordinates completely coincide with the center position of the fluid loading and unloading arm, the docking operation is completed, and the fluid loading and unloading arm is lowered by a lifting hydraulic cylinder. This invention combines image recognition technology, hydraulic transmission and control technology. It uses an industrial camera to capture images of the pipe opening, and a computer algorithm to determine the pipe opening's centering coordinates, which are then used as the centering control signal for the cryogenic fluid loading and unloading arm. A hydraulic cylinder then drives the loading and unloading arm to automatically center, lower, and retract the arm relative to the pipe opening, thereby minimizing human labor during loading and reducing potential safety hazards. The invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0024] Example 1 This embodiment discloses a docking method for a cryogenic loading and unloading conveying system, such as... Figure 1 The steps shown are as follows: S1 After the tanker truck enters the work area, the tanker truck is roughly positioned to preliminarily determine the location of the tank opening.

[0025] Images of the tanker opening of a tanker truck taken using an integrated industrial camera under natural lighting conditions, such as... Figure 2 As shown, The grayscale value inside the tanker truck's opening is significantly lower than that of the vehicle body. Therefore, the initial method for determining the location of the tanker truck's opening is as follows: A threshold limit for the grayscale band is set; when consecutive scans show grayscale values ​​below the threshold limit, the tanker truck is considered to have entered the working area, i.e., the visible range of the industrial integrated camera, and the continuous area with grayscale values ​​below the threshold limit is identified as the opening area; the center of the opening area is selected as the center coordinate for coarse positioning. In this embodiment, the threshold limit for the grayscale band is 1 / 3 of the average value of all pixels in the opening image, to ensure that the industrial integrated camera can acquire images more stably after the tanker truck enters the effective field of view.

[0026] S2 takes a picture of the can opening at the can opening position to obtain an image of the can opening.

[0027] The grayscale difference between the inner and outer edges of the can opening is small, and there is no significant brightness change with the change of light intensity, which greatly interferes with the edge detection of the can opening. To highlight the contour features of the can opening edge, it is necessary to preprocess the captured can opening image, especially image enhancement technology. The image enhancement processing of the can opening image is performed as follows: obtain the grayscale value of each pixel in the spatial area of ​​the can opening image; construct a grayscale histogram of grayscale values ​​[0~255] based on the grayscale value of each pixel, that is, map the grayscale value of each pixel in the image to the grayscale histogram; in Matlab, correct the grayscale values ​​of the can opening image to [0,100] in the histogram to eliminate the influence of the shadow part inside the can opening, and obtain the grayscale corrected can opening image as shown below. Figure 3 As shown.

[0028] S3 inputs the image of the can opening into the image edge detection algorithm model to obtain the edge image of the can opening.

[0029] Edge detection methods are used to segment images of tank truck openings. This involves connecting detected edge points according to a specific strategy to outline the edge contour curve of the opening. Edges serve as a crucial basis for segmenting the target image from the background region and are essential for subsequent image processing. Currently, among numerous image edge detection methods, the Canny algorithm is widely used due to its stable performance, high segmentation accuracy, and ease of adjustment.

[0030] Traditional Canny algorithms use Gaussian filtering for image preprocessing, which can eliminate some noise interference. However, continuously increasing the standard deviation radius can cause excessive smoothing, leading to image distortion or the creation of false edges. Furthermore, the image thresholding process requires manual adjustment of high and low threshold values ​​based on experience to adapt to environmental changes. This method is time-consuming, struggles to determine the optimal dual thresholds, and has poor adaptability. Therefore, this embodiment employs an adaptive threshold Canny algorithm for image edge detection to adapt to complex environments and ensure accurate edge detection.

[0031] like Figure 4 As shown, the image edge detection algorithm model employs the adaptive threshold Canny algorithm to obtain the edge image of the can opening. The method is as follows: input the can opening image; perform bilateral filtering on the can opening image to remove noise interference while preserving edge details to the greatest extent; based on the denoised can opening image, calculate the gradient components in the horizontal, vertical, 45°, and 135° directions to calculate the gradient magnitude of the center pixel, thereby expanding the edge detection search range; based on the gradient magnitude of the center pixel, distinguish between the can opening and the vehicle body using the Otsu's method (maximum inter-class variance); and enhance the contrast of the can opening image through histogram normalization to obtain the edge image of the can opening. The adaptive threshold Canny algorithm overcomes the problems of traditional Canny algorithms, such as the need for manually given thresholds when identifying image edges, resulting in low image recognition efficiency and poor accuracy.

[0032] Bilateral filtering performs nonlinear filtering by combining pixel similarity and geometric spatial distance. It calculates the weights of pixel similarity and geometric spatial distance using two Gaussian functions, then convolves these weights with the original can opening image to output a denoised can opening image. In the MATLAB environment, salt-and-pepper noise was added to the can opening images, and the images processed by bilateral filtering and Gaussian filtering were compared. The experimental results are as follows: Figure 5 As shown. By Figure 5 It can be seen that after adding salt and pepper noise to the original image of the can opening, compared with Gaussian filtering, the image after bilateral filtering has less noise and better image smoothing effect. While suppressing noise and smoothing the image, it preserves the continuity and integrity of the image edges to a greater extent.

[0033] The formula for calculating bilateral filtering is as follows:

[0034]

[0035] in, It is a bilaterally filtered image of the tank opening. p Center pixel q For input pixels, As the normalization factor, S It is the set of all pixels q within the filtering neighborhood window centered on the central pixel p. It is the spatial domain weight. It is the range weight. It is the original image. It is the grayscale value (pixel brightness value) of the center pixel p of the original image. and The calculation formula is:

[0036]

[0037] in, m、n These are the x and y coordinates of the input pixel, respectively. i, j These are the x and y coordinates of the center pixel, respectively. I(m,n) It is the value of the input pixel. I(i,j) It is the value of the center pixel. It is based on the spatial standard deviation of a two-dimensional Gaussian function. It is based on the gray-level standard deviation of a two-dimensional Gaussian function. In practical applications, due to insufficient experience, it is impossible to provide a reasonable standard deviation. Therefore, the denoising and edge preservation effect of the output image is poor. To ensure that the algorithm obtains high-quality image edge information while denoising, this embodiment selects multiple noisy images for experiments in the MATLAB environment. Through performance evaluation and analysis of the filtered images, the bilateral filter is finally determined. For: because the two-dimensional Gaussian function is in [-2 ,2 The spatial standard deviation exhibits a normal distribution trend within the range, based on a two-dimensional Gaussian function. Determined by the radius of the can opening, i.e. The standard deviation of gray levels based on a two-dimensional Gaussian function is equal to twice the standard deviation of noise at all pixels during the filtering process. That is... , This represents the noise standard deviation of all pixels during the filtering process.

[0038] Traditional Canny algorithms often employ the Sobel algorithm's convolution operation for gradient calculation, determining the blurred position of the center pixel by analyzing the vector direction and gradient intensity information of each pixel. However, this method only considers the horizontal and vertical grayscale gradients of the center pixel, potentially missing some pixels during scanning and resulting in discontinuous image edges. To reduce false edges and other artifacts, this embodiment adds templates at 45° and 135° directions to the original horizontal and vertical directions of the center pixel. The added Sobel algorithm templates are shown below. Figure 4 As shown. Let the gradient template in the horizontal direction be... M x The gradient components are E x The gradient template in the vertical direction is M y The gradient components are E y The gradient template in the 45° direction is M n The gradient components are E n The gradient template in the 135° direction isM m The gradient components are E m .

[0039]

[0040] Performing a convolution operation on the above formula yields the gradient magnitude of the center pixel. E The calculation formula is:

[0041] in, It is the gradient component in the horizontal direction. It is the gradient component in the vertical direction; It is the gradient component in the 45° direction; It is the gradient component in the 145° direction; the method to distinguish between the tank opening and the vehicle body is: adaptively obtain the maximum threshold of pixel values ​​in the image using the maximum inter-class variance method; use the maximum threshold as the high threshold T. h3 Half of the maximum threshold is used as the low threshold T. h4 Pixel values ​​higher than the high threshold T h3 Pixels with values ​​below a certain threshold T are assigned a first grayscale value. h4 The pixels are assigned a second gray value, and the first gray value is greater than the second gray value.

[0042] The image edge detection algorithm model was validated by running it in the Visual Studio environment with the OpenCV runtime library. Three images of the tanker openings of tank trucks taken on-site were selected as evaluation samples. The method in this embodiment was compared and analyzed with the traditional Canny and Soble algorithms in edge detection experiments. The output results are as follows: Figure 5 As shown. Figure 7 As shown, the classic Canny algorithm suffers from missing information and false edges when detecting the background (circled in green) edges of tanker images. Edge contour feature extraction is discontinuous with numerous extraneous lines, resulting in a large number of noise points and blurred boundaries. In comparison, the Soble algorithm performs slightly better than the classic Canny algorithm, but it suffers from numerous false edges and noise when processing image details (circled in red), leading to blurred edges and a lack of prominence in true edges. Both the traditional Canny and Soble algorithms are significantly affected by noise from vehicle oil stains and lighting conditions. Compared to the previous two methods, the method in this embodiment can suppress the generation of false edges to the greatest extent, ensuring the continuity of image edges, resulting in a clearer overall image contour with fewer edge breakpoints, effectively offsetting most of the noise and false edge effects. This demonstrates that the method in this embodiment can quickly and accurately identify the edge contour image of a tanker truck's opening in complex environments.

[0043] S4 corrects the edge image through orthogonal scanning to obtain the center coordinates of the can opening.

[0044] Because the initial position of the fluid loading / unloading arm is uncertain, the industrial integrated camera easily captures incomplete circles when acquiring images of the tank opening. Therefore, orthogonal scanning is used for correction. The method for correcting the edge image using orthogonal scanning is as follows: The tank opening image is an incomplete circle. Two non-parallel chords are drawn on the incomplete circle. One chord intersects the circle at points q(a,b) and p(c,d), and the other chord intersects the circle at points m(e,f) and n(g,h). The perpendicular bisectors of the two chords are then drawn. The intersection of the two perpendicular bisectors is the center coordinate of the tank opening. Figure 8 As shown. The formula for calculating the center coordinates (O1, O2) of the can opening is:

[0045] in, With the center coordinates, It can be 1 or 2.

[0046] S5 compares the center coordinates with the center position of the fluid loading / unloading arm to obtain the deviation between the two.

[0047] S6 drives the fluid loading / unloading arm to move according to the deviation.

[0048] The formula for calculating the adjustment amount for the fluid loading / unloading arm movement driven by the deviation is as follows: Adjustment value = Deviation × +differential value × +points value×

[0049] The integral value is the sum of the previous integral value and the current deviation; the differential value is the current deviation minus the previous deviation; the deviation is equal to the center position of the center coordinates minus the center position of the fluid loading / unloading arm.

[0050] When the center coordinates of S7 completely coincide with the center position of the fluid loading and unloading arm, the docking operation is completed, and the lifting hydraulic cylinder completes the lowering of the fluid loading and unloading arm.

[0051] Example 2 Based on the same inventive concept, this embodiment discloses a docking device for a cryogenic loading and unloading conveying system, used for docking methods of cryogenic loading and unloading conveying systems as described above. Figure 9As shown, the system includes: a vision unit, a fluid loading / unloading arm alignment control unit, a host computer, and a PLC control system. The vision unit is used to obtain an image of the tanker opening of the tank truck and transmit the image to the host computer and the fluid loading / unloading arm alignment control unit. The fluid loading / unloading arm alignment control unit is used to obtain the center position coordinates of the fluid loading / unloading arm based on a displacement sensor, and drive the fluid loading / unloading arm to move according to the drive control signal issued by the PLC control system to complete the alignment of the fluid loading / unloading arm with the tank truck. In this embodiment, the fluid loading / unloading arm is driven to move on the track by a valve-controlled hydraulic cylinder, and its displacement is controlled to be an adjustment value. The host computer is used to calculate the center coordinates of the tank opening based on the image of the tank opening, send control commands to the PLC control system based on the center coordinates of the tank opening, and receive feedback signals from the PLC control system. The PLC control system is used to obtain the deviation between the center coordinates and the center position of the fluid loading / unloading arm, and generate a drive control signal based on the deviation.

[0052] The structure of the drive module of the fluid loading and unloading arm is as follows: Figure 10 As shown, the system includes: a horizontal guide rail 1; a traction trolley 2 mounted on the horizontal guide rail 1; the traction trolley 2 connected to a horizontal drive hydraulic cylinder 3, allowing the traction trolley 2 to reciprocate on the horizontal guide rail 1; a vertical support 4 mounted on the traction trolley 2, supporting a lifting pipe 5; the top end of the lifting pipe 5 connected to a fluid loading / unloading arm; and an oil receiving hopper 6 connected to the bottom of the lifting pipe 5, sealed to the outside by a sealing cap 7. A vertical drive hydraulic cylinder 8 is located at the bottom of the lifting pipe 5, with one end connected to the oil receiving hopper 6 and the other end connected to the horizontal guide rail 1, used to drive the lifting pipe 5 and the fluid loading / unloading arm to reciprocate vertically.

[0053] Both the horizontal drive hydraulic cylinder 3 and the vertical drive hydraulic cylinder 8 are connected to the hydraulic station 9. The vertical drive hydraulic cylinder 8 is connected to the hydraulic station 9 via a stainless steel hydraulic line 10.

[0054] In other words, the fluid loading arm can achieve two-dimensional movement in both the horizontal and vertical directions. The reason for choosing a hydraulic cylinder drive module to realize the movement of the fluid loading arm is that the electrical control components in the hydraulic transmission module can be located away from the loading area, so no electrical sparks will be generated, which makes the loading process safer.

[0055] The working process of the drive module of the fluid loading and unloading arm is as follows: When the tank truck arrives at the designated working area, the traction crawler 2 pushes the tank truck to travel a distance of about one parking space to complete the coarse positioning. At this time, the tank opening image is obtained by the method in Example 1, and the tank opening image is input into the image edge detection algorithm model to obtain the edge image of the tank opening. The calculated center coordinates of the tank opening are then transmitted to the host computer through the PLC control system.

[0056] The fluid loading / unloading arm reciprocates in both the horizontal and vertical directions, so it can be equipped with an upward-acting single-rod hydraulic cylinder. The reciprocating motion of the hydraulic cylinder can be achieved through a proportional servo valve. During horizontal movement, precise position control is required to ensure alignment between the fluid loading / unloading arm and the tank truck opening; therefore, a standard hydraulic servo system cannot be used.

[0057] like Figure 11 As shown, in this embodiment, the hydraulic servo control includes a first oil pump 11 and a second oil pump 12. The first oil pump 11 supplies oil for the lifting and lowering movement of the loading and unloading arm, and the second oil pump 12 supplies oil for the horizontal movement of the loading and unloading arm. The first oil pump 11 and the second oil pump 12 are respectively connected to the oil tank 15 through a first relief valve 13 and a second relief valve 14. The first relief valve 13 and the second relief valve 14 are respectively used to adjust the maximum pressure of the first oil pump 11 and the second oil pump 12 to avoid interference caused when the load changes.

[0058] The first oil pump 11 is connected to the vertical drive hydraulic cylinder 6 via the first proportional servo valve 16 and the speed control valve 17. A first displacement sensor 18 is installed on the vertical drive hydraulic cylinder 6. The second oil pump 12 is connected to the input end of the horizontal drive hydraulic cylinder 3 via the second proportional servo valve 19. The output end of the horizontal drive hydraulic cylinder 3 is connected to the input end of the traction crawler 2. The output end of the traction crawler 2 is connected to the input end of the second displacement sensor 20. The output end of the second displacement sensor 20 is connected to the input end of the servo amplifier 21. The output end of the servo amplifier 21 is connected to the second proportional servo valve 19, forming a loop. The proportional servo valve enables displacement control of the fluid loading / unloading arm and facilitates structural feedback control, further improving the accuracy of hydraulic servo control. The vertical lifting motion of the fluid loading / unloading arm is driven by a dual hydraulic cylinder. This is because the fluid loading / unloading arm requires a large stroke when penetrating deep into the tank of the tanker truck, necessitating a long-stroke hydraulic cylinder. However, long-stroke cylinders suffer from reduced rigidity and stability; a dual-cylinder structure is more conducive to maintaining rigidity and stability. In addition, the dual-cylinder support distributes the load from the loading arm to the cylinder, reducing the working pressure of the hydraulic system.

[0059] When the fluid loading / unloading arm is not extended, the piston rod of the vertical drive hydraulic cylinder 6 extends to its maximum stroke, supporting the fluid loading / unloading arm and preventing it from falling. When the fluid loading / unloading arm moves to the center position above the tank truck opening, the first proportional servo valve 16 switches to the left position, and the pressurized oil output from the first oil pump 11 enters the rod chamber of the vertical drive hydraulic cylinder 6, causing the piston rod to retract, i.e., lowering the fluid loading / unloading arm into the tank truck body; at this time, the falling speed of the fluid loading / unloading arm is adjusted by the speed control valve 17. When the oil transfer is complete and the fluid loading / unloading arm needs to be lifted, the first proportional servo valve 16 switches to the right position, and pressurized oil enters the rodless chamber of the vertical drive hydraulic cylinder 6, extending the piston rod to return the oil transfer arm to its initial state. The first displacement sensor 18 is used to detect the stroke of the fluid loading / unloading arm, ensuring that it can be fully raised or lowered. The speed control valve 17 is used to adjust the movement speed of the piston rod and also to ensure the synchronous movement of the two cylinders in the dual-cylinder vertical drive hydraulic cylinder 6.

[0060] The piston rod of the horizontal drive hydraulic cylinder 3 retracts completely, bringing the traction trolley 2 and the fluid loading / unloading arm mounted on it to their initial positions. After detecting the alignment coordinates of the tank opening, the servo amplifier 21 receives the alignment control signal U. ps Then, the centering control signal is amplified and input to the second proportional servo valve 19. The second proportional servo valve 19 switches to the right position, and the pressure oil output by the second oil pump 12 enters the rodless chamber of the horizontal drive hydraulic cylinder 3, pushing the traction trolley 2 and the fluid loading and unloading arm to move towards the tank opening position. The moving distance is detected by the second displacement sensor 20, which sends a feedback signal U. fs Centering control signal U ps and feedback signal U fs The comparison is performed in the servo amplifier 21 to form the adjustment value U. e U e =U ps -U fs Adjustment value U e This represents the positional difference between the fluid loading / unloading arm and the tank opening, as long as U e ≠0, before the fluid loading / unloading arm reaches the centering position, the second hydraulic cylinder will push it towards the tank opening. (This is followed by a seemingly unrelated instruction: "to centering control signal U") ps and feedback signal U fs When the comparison result is 0, it indicates that the traction crawler 2 has reached the centering position of the tank opening, the second hydraulic cylinder stops moving, and the first proportional servo valve 16 controls the extension of the fluid loading and unloading arm. When the transportation is completed and the fluid loading and unloading arm is fully retracted, the first displacement sensor 18 sends a signal to the second proportional servo valve 19, causing the second proportional servo valve 19 to switch to the left position; at this time, the oil output by the second oil pump 12 enters the rod chamber of the horizontal drive hydraulic cylinder, driving the traction crawler 2 and the fluid loading and unloading arm to retract to their original initial position.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific embodiments of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention. The above content is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims

1. A docking method for a cryogenic loading and unloading conveying system, characterized in that, Includes the following steps: Once the tanker truck enters the work area, it is roughly positioned to preliminarily determine the location of the tank opening. Take a picture of the can opening at the specified location to obtain an image of the can opening; The image of the can opening is input into the image edge detection algorithm model to obtain the edge image of the can opening; The center coordinates of the can opening are obtained by correcting the edge image through orthogonal scanning; The center coordinates are compared with the center position of the fluid loading and unloading arm to obtain the deviation between the two. The fluid loading / unloading arm is moved according to the deviation amount; When the center coordinates are completely aligned with the center position of the fluid loading and unloading arm, the docking operation is completed, and the fluid loading and unloading arm is lowered by the lifting hydraulic cylinder.

2. The docking method for a cryogenic loading and unloading conveying system as described in claim 1, characterized in that, The method for initially determining the location of the tanker truck's opening is as follows: Set the threshold limits for the grayscale band; When the grayscale value of a scan is continuously lower than the threshold limit, it is determined that the tanker truck has entered the working area, and the continuous area with the grayscale value lower than the threshold limit is identified as the tank opening area. The center of the can opening area is selected as the center coordinate for coarse positioning.

3. The docking method for a cryogenic loading and unloading conveying system as described in claim 2, characterized in that, The image enhancement process for the can opening image is as follows: obtaining the grayscale value of a single pixel in the space of the can opening image; constructing a histogram of grayscale values ​​based on the grayscale value of each pixel; and correcting the grayscale value of the can opening image to [0, 100] in the histogram to eliminate the influence of the shadow part inside the can opening.

4. The docking method for a cryogenic loading and unloading conveying system as described in claim 1, characterized in that, The image edge detection algorithm model employs the Canny algorithm with adaptive thresholding to obtain the edge image of the can opening as follows: Input an image of the tank opening; The image of the can opening is subjected to bilateral filtering for noise reduction; Based on the denoised image of the tank opening, the gradient components in the horizontal, vertical, 45° and 135° directions are calculated to determine the gradient magnitude of the center pixel. Based on the gradient magnitude of the center pixel, the tank opening and the vehicle body are distinguished using the maximum inter-class variance method. Histogram normalization enhances the contrast of the can opening image, thereby obtaining the edge image of the can opening.

5. The docking method for a cryogenic loading and unloading conveying system as described in claim 4, characterized in that, The bilateral filtering performs nonlinear filtering by combining pixel similarity and geometric spatial distance. It calculates the weights of pixel similarity and geometric spatial distance using two Gaussian functions, and then performs a convolution operation with the original can opening image to output a denoised can opening image. The spatial standard deviation based on the two-dimensional Gaussian function is determined by the radius of the can opening, and the grayscale standard deviation based on the two-dimensional Gaussian function is equal to twice the noise standard deviation of all pixels during the filtering process.

6. The docking method for a cryogenic loading and unloading conveying system as described in claim 4, characterized in that, The gradient magnitude of the center pixel E The calculation formula is: in, It is the gradient component in the horizontal direction. It is the gradient component in the vertical direction; It is the gradient component in the 45° direction; It is the gradient component in the 145° direction; The method for distinguishing between the tank opening and the vehicle body is as follows: by using the maximum inter-class variance method, the maximum threshold of pixel values ​​in the image is adaptively obtained; the maximum threshold is used as a high threshold, half of the maximum threshold is used as a low threshold, pixels with pixel values ​​higher than the high threshold are assigned a first gray value, and pixels with pixel values ​​lower than the low threshold are assigned a second gray value, wherein the first gray value is greater than the second gray value.

7. The docking method for a cryogenic loading and unloading conveying system as described in claim 4, characterized in that, The method for correcting the edge image by orthogonal scanning is as follows: the image of the can opening is an incomplete circle, two non-parallel chords are drawn on the incomplete circle, and the perpendicular bisectors of the two chords are drawn respectively. The intersection of the two perpendicular bisectors is the center coordinate of the can opening.

8. The docking method for a cryogenic loading and unloading conveying system as described in any one of claims 1-7, characterized in that, The formula for calculating the adjustment amount for driving the fluid loading / unloading arm to move based on the aforementioned deviation is as follows: Adjustment value = Deviation × +differential value × +points value× ; The integral value is the sum of the previous integral value and the current deviation; the differential value is the current deviation minus the previous deviation; the deviation is equal to the center position of the center coordinates minus the center position of the fluid loading / unloading arm.

9. A docking device for a cryogenic loading and unloading conveying system, used in the docking method for a cryogenic loading and unloading conveying system as described in any one of claims 1-8, characterized in that, include: The system comprises a vision unit, a fluid loading / unloading arm alignment control unit, a host computer, and a PLC control system. The vision unit acquires an image of the tanker opening of the tank truck and transmits the image to the host computer and the fluid loading / unloading arm alignment control unit. The fluid loading / unloading arm alignment control unit obtains the center position coordinates of the fluid loading / unloading arm based on a displacement sensor and drives the fluid loading / unloading arm to move according to the drive control signal issued by the PLC control system, thereby aligning the fluid loading / unloading arm with the tanker truck. The host computer calculates the center coordinates of the tank opening based on the image, sends control commands to the PLC control system based on the center coordinates, and receives feedback signals from the PLC control system. The PLC control system obtains the deviation between the center coordinates and the center position of the fluid loading / unloading arm and generates a drive control signal based on the deviation.

10. The docking device for a cryogenic loading and unloading conveying system as described in claim 9, characterized in that, The centering control unit of the fluid loading and unloading arm adopts hydraulic servo control, which includes a first oil pump and a second oil pump. The first oil pump supplies oil for the lifting and lowering movement of the loading and unloading arm, and the second oil pump supplies oil for the horizontal movement of the loading and unloading arm. The first and second oil pumps are respectively connected to the oil tank through a first relief valve and a second relief valve. The first oil pump is connected to the vertical drive hydraulic cylinder through a first proportional servo valve and a speed control valve. A first displacement sensor is installed on the vertical drive hydraulic cylinder. The second oil pump is connected to the input end of the horizontal drive hydraulic cylinder through a second proportional servo valve. The output end of the horizontal drive hydraulic cylinder is connected to the input end of the traction crawler. The output end of the traction crawler is connected to the input end of the second displacement sensor. The output end of the second displacement sensor is connected to the input end of the servo amplifier. The output end of the servo amplifier is connected to the second proportional servo valve, forming a loop.

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