A method for controlling the shape and position dimensions of ultra-long common-bottom storage tanks in a vertical assembly and welding mode

Abstract

This application provides a method for controlling the shape and dimensions of an ultra-long common-bottom tank in a vertical assembly and welding mode, including a method for controlling the length between the front and rear end frames of the tank, a method for controlling the parallelism of the end faces of the front and rear end frames, and a method for controlling the coaxiality of the mating surfaces of the front and rear end frames. The method for controlling the length between the front and rear end frames is used to control the length between the front and rear end frames, ensuring that the overall tank length tolerance meets a predetermined tolerance range. The method for controlling the parallelism of the end faces of the front and rear end frames is used to adjust the parallelism between the connecting surfaces of the bottom support ring end frame and the lifting ring end frame, ensuring that the parallelism of the end faces of the front and rear end frames meets a predetermined parallelism range. The method for controlling the coaxiality of the mating surfaces of the front and rear end frames is used to adjust the coaxiality between the connecting surfaces of the lifting ring end frame and the bottom support ring end frame, ensuring that the coaxiality of the mating surfaces of the front and rear end frames meets a predetermined coaxiality range. The method described in this application enables high-quality and high-standard research and production of ultra-long common-bottom tanks in a vertical assembly and welding mode.

Description

Technical Field

[0001] This application belongs to the technical field of automated equipment for assembling and welding large propellant tanks for launch vehicles, and particularly relates to a method for controlling the shape and position dimensions of an ultra-long common-bottom propellant tank in a vertical assembly and welding mode. Background Technology

[0002] Currently, the largest fuel tank for domestic launch vehicles has a diameter of 5m and a length of 20m. The tank is produced by welding using a horizontal assembly and welding method. The length tolerance is required to be ≤10mm, the parallelism of the front and rear end frame faces is ≤4mm, and the coaxiality of the front and rear end frame mating surfaces is ≤Φ10mm.

[0003] Comparison of the dimensional requirements of the new generation of launch vehicle's ultra-long common-base propellant tank with the current largest fuel tank. Figure 2 As shown in the comparative analysis, the length tolerance control of the ultra-long common bottom propellant tank of the new generation of launch vehicles is the same, but the requirements for the parallelism of the end faces of the front and rear frame and the coaxiality of the docking surfaces of the front and rear frame are doubled, which greatly increases the control difficulty.

[0004] my country's largest carrier rocket fuel tanks all adopt a horizontal assembly and welding mode and use tungsten inert gas welding process. The tank shape and size control technology and equipment can only meet the production requirements of tanks with a length of less than 20m between the front and rear frames, and cannot meet the production requirements of 40m-class ultra-long common bottom tanks. Summary of the Invention

[0005] In view of this, this application aims to propose a method for controlling the shape and position dimensions of ultra-long common-bottom tanks in a vertical assembly and welding mode, so as to solve the problem that the shape and position dimension control technology for 20m tanks cannot meet the production requirements of 40m-class ultra-long common-bottom tanks.

[0006] To achieve the above objectives, the technical solution of this application is implemented as follows:

[0007] This application provides a method for controlling the shape and position dimensions of an ultra-long common-bottom tank in a vertical assembly and welding mode, including a method for controlling the length between the front and rear end frames of the tank, a method for controlling the parallelism of the end faces of the front and rear end frames of the tank, and a method for controlling the coaxiality of the mating surfaces of the front and rear end frames of the tank.

[0008] The method for controlling the length between the front and rear frames of the storage tank controls the length of the tank cylinder section and controls the length of half of the tank before sealing and welding, so as to ensure that the overall length tolerance meets the predetermined tolerance range.

[0009] The parallelism control method for the front and rear end frames of the storage tank calculates the parallelism by detecting the target point offset data through a laser measurement array, and adjusts the parallelism of the connection surface between the bottom support ring end frame and the lifting ring end frame by correcting the mechanical coordinates of the lifting mechanism, so that the parallelism of the front and rear end frames of the storage tank meets the predetermined parallelism range.

[0010] The method for controlling the coaxiality of the front and rear end frame mating surfaces of the storage tank calculates the coaxiality by detecting target point offset data using a laser measurement array, and adjusts the coaxiality of the lifting ring end frame connecting surface and the bottom support ring end frame connecting surface by correcting the center coordinates of the lifting ring, so that the coaxiality of the front and rear end frame mating surfaces of the storage tank meets the predetermined coaxiality range.

[0011] Furthermore, the method for controlling the length between the front and rear end frames of the storage tank includes:

[0012] The actual length of the cylinder segment is controlled by the standard cylinder segment control method: theoretical length of cylinder segment + 4.5mm, tolerance ±1mm, so as to control the overall length tolerance within 15mm;

[0013] Multiple laser targets are set on the end face of one side of the tank that has been welded. A laser rangefinder is used to measure the length of the target points on the end face of the half-tank sealing circumferential seam to be welded. The average length of the half-tank is obtained based on the length of the multiple target points. The milling amount of the half-tank to be welded is calculated from the average length of the half-tank, the theoretical length between the front and rear end frames of the tank, and the height of the front bottom assembly measured before the bottom assembly is put on the frame for sealing welding. After the milling is completed, sealing welding is performed.

[0014] Furthermore, the formula for calculating the milling allowance for the half-box to be welded is as follows:

[0015] δ=La+Lb-L0-2;

[0016] In the formula, La represents the height of the front bottom assembly, Lb represents the average length of half the tank, and L0 represents the theoretical length between the front and rear end frames of the tank.

[0017] Furthermore, the method for controlling the parallelism of the front and rear end face frames of the storage tank includes a method for measuring the parallelism of the front and rear end face frames, comprising:

[0018] The laser measurement array is arranged circumferentially on the bottom frame connection surface of the lifting ring box, and the laser target array is arranged circumferentially on the bottom support ring of the box, corresponding to the axis of the laser measurement array.

[0019] Before the storage tank product is put on the shelf, the position of the laser target point is measured by the target, and the parallelism of the connection surface of the bottom support ring end frame and the connection surface of the lifting ring end frame is calculated based on the target point offset of multiple target point positions.

[0020] Furthermore, the parallelism control method for the front and rear end face frames of the storage tank also includes a method for correcting the parallelism of the front and rear end face frames, comprising:

[0021] The bottom support ring of the tank is fixed. The coordinates of the lifting mechanism connected to the lifting ring are corrected based on the calculated parallelism between the end frame connecting surface of the bottom support ring and the end frame connecting surface of the lifting ring. The corrected coordinate values ​​are then updated to new parallelism reference coordinates. The pose of the end frame connecting surface of the lifting ring is adjusted based on the new parallelism reference coordinates to regulate the parallelism between the end frame connecting surface of the bottom support ring and the end frame connecting surface of the lifting ring, thereby controlling the parallelism of the front and rear end frame end faces of the tank within a predetermined parallelism range.

[0022] Furthermore, the method for controlling the coaxiality of the mating surfaces of the front and rear end frames of the storage tank includes a method for measuring the coaxiality of the mating surfaces of the front and rear end frames, comprising:

[0023] A laser measuring instrument is set at the center point of the lifting ring, and a laser target is set at the center point of the bottom support ring. Before the storage tank is put on the shelf, the position of the laser target point is measured by the target. The coaxiality of the connection surface of the bottom support ring end frame and the connection surface of the lifting ring end frame is calculated based on the target point offset of multiple target point positions.

[0024] Furthermore, the method for controlling the coaxiality of the mating surfaces of the front and rear end frames of the storage tank also includes:

[0025] The bottom support ring of the tank is fixed. The lifting ring is corrected based on the coaxiality of the end frame connection surface of the bottom support ring and the end frame connection surface of the lifting ring. The corrected coordinate values ​​are updated to new coaxiality reference coordinates. The center point position of the lifting ring is adjusted based on the new coaxiality reference coordinates to regulate the coaxiality of the end frame connection surface of the lifting ring and the end frame connection surface of the bottom support ring, and to control the coaxiality of the front and rear end frame mating surfaces of the tank within a predetermined coaxiality range.

[0026] Furthermore, the theoretical center points of the connection surfaces of the bottom support ring end frame and the lifting ring end frame are determined and marked by CNC machining of the end face positioning pin holes and connection holes.

[0027] Compared with the prior art, the method for controlling the shape and position dimensions of an ultra-long common-bottom tank in a vertical assembly and welding mode described in this application has the following advantages:

[0028] The method for controlling the shape and position dimensions of an ultra-long common-bottom tank in a vertical assembly and welding mode described in this application can control the length between the front and rear end frames, the parallelism of the end faces of the front and rear end frames, and the coaxiality of the mating surfaces of the front and rear end frames within the design tolerance range, thereby achieving high-quality and high-standard research and development and production of the product. Attached Figure Description

[0029] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0030] Figure 1This is a schematic diagram of the tank structure and main dimensions described in the embodiments of this application;

[0031] Figure 2 This is a comparison diagram of the dimensional requirements of the ultra-long storage tank described in the embodiments of this application and the existing maximum storage tank.

[0032] Figure 3 This is a schematic diagram of the device layout for the precision measurement and milling method before sealing the box as described in the embodiments of this application;

[0033] Figure 4 This is a schematic diagram of the vertical assembly and welding state of the ultra-long common bottom tank described in the embodiments of this application;

[0034] Figure 5 This is a schematic diagram illustrating the parallelism measurement of the front and rear frame connection surfaces as described in an embodiment of this application.

[0035] Figure 6 This is a schematic diagram of laser target offset measurement as described in an embodiment of this application;

[0036] Figure 7 This is a schematic diagram of the lifting ring parallelism adjustment described in the embodiments of this application;

[0037] Figure 8 This is a schematic diagram showing the positioning of the center point of the connection surface between the bottom support ring and the lifting ring end frame as described in the embodiments of this application;

[0038] Figure 9 This is a schematic diagram of the coaxiality measurement of the mating surfaces of the front and rear end frames of the storage tank as described in an embodiment of this application;

[0039] Figure 10 This is a schematic diagram of the coaxiality adjustment of the lifting ring as described in an embodiment of this application. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0041] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0042] The embodiments of this application are described in detail below with reference to the accompanying drawings.

[0043] Explanation of technical terms:

[0044] Common-bottom tank: The propellant tank and oxidizer tank are combined into one tank, and the propellant and oxidizer are separated by a common bottom inside the tank.

[0045] Tank bottom assembly: including front bottom assembly and rear bottom assembly, which is welded together from the tank bottom and short shell, and participates in the welding of the tank as an integral component.

[0046] End frame: including front frame and rear frame, located on the short shell of front bottom assembly and rear bottom assembly respectively, and is an important connection surface between the propellant tank and other rocket body structures.

[0047] my country's new generation of carrier rocket fuel tanks are characterized by their ultra-long length, novel structure, and high requirements. The tanks have a diameter of 5 meters and a length of approximately 40 meters, featuring a common-bottom structure (see schematic diagram of tank structure and main dimensions). Figure 1 As shown, a vertical welding method is used for the welding production of the box body. The box body manufacturing standards are high and the shape and size requirements are strict. Within the 40m scale range, the length tolerance between the front and rear end frames of the box body is required to be ≤20mm, the parallelism of the end faces of the front and rear end frames is ≤4mm, and the coaxiality of the mating surfaces of the front and rear end frames of the box body is ≤Φ10mm.

[0048] Because my country's largest launch vehicle fuel tank currently uses a horizontal assembly and welding method and employs tungsten inert gas welding, the tank's shape and size control technology and equipment can only meet the production requirements of tanks with a length of less than 20m between the front and rear frames. There is currently no shape and size control technology for ultra-long common-bottom tanks with a length of 40m or more.

[0049] Based on the above, this application develops a dimension control technology for ultra-long common-bottom tanks under the vertical assembly and welding mode, which controls the length between the front and rear end frames, the parallelism of the end faces of the front and rear end frames, and the coaxiality of the mating surfaces of the front and rear end frames within the design tolerance range, thereby achieving high-quality and high-standard research and production of the product.

[0050] The method for controlling the shape and position dimensions of an ultra-long common-bottom tank in a vertical assembly and welding mode described in this embodiment mainly includes a method for controlling the length between the front and rear end frames of the tank, a method for controlling the parallelism of the end faces of the front and rear end frames of the tank, and a method for controlling the coaxiality of the mating surfaces of the front and rear end frames of the tank. This embodiment will describe each of the above control methods in detail.

[0051] I. Method for controlling the length between the front and rear end frames of the storage tank

[0052] The method for controlling the length between the front and rear frames of the ultra-long common-bottom tank in this application adopts a standard cylinder section and a precise measurement and milling method before sealing the tank body, which controls the overall tank length tolerance within 5mm.

[0053] (1) Standard cylinder section control method:

[0054] The extra-long storage tank mainly consists of front and rear short shells, front and rear tank bottoms, a common bottom, and several cylindrical sections. The length of the tank is mainly affected by the length of the cylindrical sections. Controlling the length of the cylindrical sections within a relatively precise range can effectively control the length of the tank body. After analysis and verification, controlling the actual length of the cylindrical sections to: theoretical length of the cylindrical section + 4.5mm, with a tolerance of ±1mm, can control the overall tank length tolerance within 15mm.

[0055] (2) Precision measurement and milling method for sealing the storage tank body:

[0056] By measuring and milling the length of half-tank before sealing and welding, the length between the front and rear frames of the tank can be further precisely controlled. The theoretical length between the front and rear frames of the tank is L0. Before the bottom assembly is placed on the frame for sealing and welding, the height La of the front bottom assembly is measured on the measuring platform.

[0057] like Figure 3 and Figure 4 As shown, laser targets are set at the end face of one side of the tank that has been welded. Four targets are evenly set around the tank. A laser rangefinder is used to measure the length of the four target points on the end face of the half-tank sealing circumference to be welded, and the average length of the half-tank is obtained as Lb = (L1 + L2 + L3 + L4) / 4. The milling amount of the half-tank to be welded is δ = La + Lb - L0 - 2 (the fixed value of 2 here is a standard value set based on work experience). After the milling is completed, the sealing welding is carried out. By using the precise measurement and milling method before sealing the tank, the overall length tolerance of the tank can be further controlled within 5mm.

[0058] II. Methods for controlling the parallelism of the front and rear end faces of the storage tank

[0059] The parallelism control method for the front and rear end faces of the storage tank in this application includes a method for measuring the parallelism of the front and rear end faces and a method for correcting the parallelism of the front and rear end faces, thereby controlling the parallelism of the front and rear end faces of the storage tank within a range of 4mm.

[0060] This embodiment controls the parallelism of the front and rear end faces of the storage tank by controlling the parallelism of the tooling connection surfaces of the equipment connecting the front and rear end frames. The mating surfaces connected to the front and rear end frames of the ultra-long storage tank are the bottom support ring end frame connection surface and the lifting ring end frame connection surface, respectively. Measurement and adjustment are performed before the storage tank is put on the rack for production. During measurement and adjustment, the distance between the bottom support ring end frame connection surface and the lifting ring end frame connection surface is adjusted to the theoretical length of the storage tank. The schematic diagram of the vertical welding state of the ultra-long common-bottom storage tank is shown below. Figure 4 As shown.

[0061] like Figure 5 As shown, to achieve parallelism measurement and precise control of the connection surfaces of the bottom support ring end frame and the lifting ring end frame within a distance of over 35m in vertical mode, this application calculates parallelism by using a laser measurement array to detect target point offset data, and achieves precise measurement and adjustment control of the parallelism between the connection surfaces of the bottom support ring end frame and the lifting ring end frame by correcting the mechanical coordinates of the lifting mechanism. The specific explanation is as follows:

[0062] (1) Method for measuring the parallelism of the front and rear end face frames:

[0063] The laser measurement array is arranged on the bottom frame connection surface of the lifting ring box, with four evenly distributed points along the circumference. The laser target array is arranged on the bottom support ring of the box, also with four evenly distributed points along the circumference, corresponding to the axis of the laser measurement array. It should be noted that when the parallelism is 0, the lasers from the four laser measurement arrays hit the center position of their respective targets.

[0064] Before the storage tank product is placed on the shelf, the parallelism laser measurement program is started to measure the position of the laser target point through the target, such as... Figures 6 to 8 As shown, if the laser target point position shifts, the target will transmit the measured target point shift X and target point shift Y to the system computer. The system computer will calculate the parallelism between the bottom support ring end frame connection surface and the lifting ring end frame connection surface based on the target point shifts at the four positions, and display the parallelism on the operation interface.

[0065] (2) Method for correcting the parallelism of the front and rear end face frames:

[0066] To achieve precise parallelism adjustment, the bottom support ring of the box is fixed, while the axial position of the lifting ring is adjusted to adapt to the parallelism of the bottom support ring. The lifting ring and the vertical frame are supported at 4 points, and each support is equipped with an independent servo lifting mechanism, which can achieve stable lifting movement and parallelism adjustment.

[0067] If the detected parallelism exceeds the process requirement, the system computer adjusts the coordinate values ​​of the four lifting mechanisms connected to the lifting ring and updates the corrected coordinate values ​​to the new parallelism reference coordinates. Based on the new parallelism reference coordinates, the position and posture of the lifting ring end frame connection surface are adjusted, thereby controlling the parallelism between the lifting ring end frame connection surface and the bottom support ring end frame connection surface, and thus controlling the parallelism of the front and rear end frame docking surfaces of the ultra-long common bottom storage tank.

[0068] The method for calculating parallelism is as follows: This embodiment uses four sets of rangefinders as an example for explanation. The measurement heights of the four sets of rangefinders are L1, L2, L3, and L4, respectively.

[0069] Parallelism N = max(L1..L4) - min(L1..L4);

[0070] The correction method is as follows:

[0071] 1) Using height L1 as the reference, the other three servo lifting mechanisms adjust their heights based on the difference between their measured heights and L1. The adjustment amounts are ΔL2 = L1 - L2; ΔL3 = L1 - L3; ΔL4 = L1 - L4, respectively.

[0072] 2) After adjustment, use a rangefinder to measure the adjusted height.

[0073] 3) Calculate the parallelism; if the parallelism index is not met, repeat step 1); if it is met, the adjustment ends.

[0074] III. Methods for controlling the coaxiality of the mating surfaces of the front and rear end frames of the storage tank:

[0075] The method for controlling the coaxiality of the mating surfaces of the front and rear end frames of the storage tank in this application includes a method for measuring the coaxiality of the mating surfaces of the front and rear end frames and a method for correcting the coaxiality of the mating surfaces of the front and rear end frames, thereby controlling the coaxiality of the end faces of the front and rear end frames of the storage tank within the range of Φ10mm.

[0076] This embodiment controls the coaxiality of the front and rear end frame mating surfaces of the storage tank by controlling the coaxiality between the central axis of the lifting ring end frame connection surface and the central axis of the bottom support ring end frame connection surface. Measurement and adjustment are performed before the storage tank is put on the shelf for production. During measurement and adjustment, the distance between the bottom support ring end frame connection surface and the lifting ring end frame connection surface is adjusted to the theoretical length position of the storage tank.

[0077] To achieve precise assembly and welding and control product quality, during the assembly of the storage tank, a method of pin positioning and connecting bolt fixing is used to connect and fix the end frame of the tank bottom assembly to the connecting surfaces of the equipment tank bottom support ring end frame and the lifting ring end frame. The theoretical axis of the storage tank bottom assembly end frame is the same as the theoretical axis of the connecting surfaces of the tank bottom support ring end frame and the lifting ring end frame. Figure 9As shown, the theoretical center points of the connection surfaces of the bottom support ring end frame and the lifting ring end frame are determined and marked when the positioning pin holes and connection holes are machined using CNC machining. A detailed explanation follows:

[0078] (1) Method for measuring the coaxiality of the mating surfaces of the front and rear end frames:

[0079] like Figure 9 As shown, in this embodiment, a laser measuring instrument is set at the center point of the lifting ring, and a laser target is set at the center point of the bottom support ring. It should be noted that when the coaxiality is 0, the laser target point of the laser measuring instrument at the center of the lifting ring should be directly aligned with the center position of the target on the bottom support ring.

[0080] Before the storage tank is put on the shelf, the coaxiality laser measurement program is started. The target measures the position of the laser target point. If the position of the laser target point is offset, the target will transmit the measured target point offset X and target point offset Y to the system computer. The system computer calculates the coaxiality of the connection surface of the bottom support ring end frame and the connection surface of the lifting ring end frame by the target point offset at the four positions, and displays the coaxiality on the operation interface.

[0081] (2) Method for correcting the coaxiality of the front and rear end frame mating surfaces:

[0082] To achieve precise coaxiality adjustment, the bottom support ring remains stationary, while the lifting ring is adjusted in the horizontal plane to align with the axis of the bottom support ring. This horizontal adjustment employs a multi-point sliding method, such as... Figure 10 As shown, a sliding platform is installed at each connection point between the lifting ring and each lifting mechanism. Each sliding platform can move independently and in conjunction with other platforms in both the X and Y directions, allowing the center point of the lifting ring to be positioned and fixed at any point within a 50mm radius circle. If the detected coaxiality exceeds the process requirements, the system computer adjusts the sliding platforms, corrects the coordinate values ​​of the lifting ring's center, and updates the corrected coordinate values ​​as the new coaxiality reference coordinates. This enables the control of the coaxiality between the lifting ring end frame connection surface and the bottom support ring end frame connection surface, thereby controlling the coaxiality of the front and rear end frame mating surfaces of the ultra-long common-bottom storage tank.

[0083] It should be noted that the coaxiality measurement algorithm used in this embodiment is based on existing technology. Coaxiality correction is based on the sensor feedback values ​​X' and Y'.

[0084] Algorithm principle: The deviation values ​​ΔX = X0 - X' and ΔY = Y0 - Y' between the reference positions X0 and Y0 and the measured positions X' and Y' are used as the errors of the self-aligning mechanism X and Y servo motors. The displacements of the self-aligning mechanism X and Y servo motors are adjusted by PID control to eliminate the errors, so that the measured position and the reference position coincide, and the product is coaxial.

[0085] 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 them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

[0086] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this application.

Claims

1. A method for controlling the shape and position dimensions of an ultra-long common-bottom storage tank in a vertical assembly and welding mode, characterized in that: This includes methods for controlling the length between the front and rear frames of the storage tank, methods for controlling the parallelism of the end faces of the front and rear frames of the storage tank, and methods for controlling the coaxiality of the mating surfaces of the front and rear frames of the storage tank. The method for controlling the length between the front and rear frames of the storage tank controls the length of the tank cylinder section and controls the length of half of the tank before sealing and welding, so as to ensure that the overall length tolerance meets the predetermined tolerance range. The parallelism control method for the front and rear end frames of the storage tank calculates the parallelism by detecting the target point offset data through a laser measurement array, and adjusts the parallelism of the connection surface between the bottom support ring end frame and the lifting ring end frame by correcting the mechanical coordinates of the lifting mechanism, so that the parallelism of the front and rear end frames of the storage tank meets the predetermined parallelism range. The method for controlling the coaxiality of the front and rear end frame mating surfaces of the storage tank calculates the coaxiality by detecting target point offset data using a laser measurement array, and adjusts the coaxiality of the lifting ring end frame connecting surface and the bottom support ring end frame connecting surface by correcting the center coordinates of the lifting ring, so that the coaxiality of the front and rear end frame mating surfaces of the storage tank meets the predetermined coaxiality range.

2. The method according to claim 1, characterized in that, The method for controlling the length between the front and rear end frames of the storage tank includes: By using the standard cylinder segment control method, the actual length of the cylinder segment is controlled within: theoretical length of cylinder segment + 4.5mm, tolerance ±1mm, so as to control the overall length tolerance within 15mm; Multiple laser targets are set on the end face of one side of the tank that has been welded. A laser rangefinder is used to measure the length of the target points on the end face of the half-tank sealing circumferential seam to be welded. The average length of the half-tank is obtained based on the length of the multiple target points. The milling amount of the half-tank to be welded is calculated from the average length of the half-tank, the theoretical length between the front and rear end frames of the tank, and the height of the front bottom assembly measured before the bottom assembly is put on the frame for sealing welding. After the milling is completed, sealing welding is performed.

3. The method according to claim 2, characterized in that, The formula for calculating the milling allowance of the half-box to be welded is as follows: δ=La+Lb-L0-2; In the formula, La represents the height of the front bottom assembly, Lb represents the average length of half the tank, and L0 represents the theoretical length between the front and rear end frames of the tank.

4. The method according to claim 1, characterized in that, The method for controlling the parallelism of the end faces of the front and rear end frames of the storage tank includes a method for measuring the parallelism of the end faces of the front and rear end frames, comprising: The laser measurement array is arranged circumferentially on the bottom frame connection surface of the lifting ring box, and the laser target array is arranged circumferentially on the bottom support ring of the box, corresponding to the axis of the laser measurement array. Before the storage tank product is put on the shelf, the position of the laser target point is measured by the target, and the parallelism of the connection surface of the bottom support ring end frame and the connection surface of the lifting ring end frame is calculated based on the target point offset of multiple target point positions.

5. The method according to claim 4, characterized in that, The method for controlling the parallelism of the end faces of the front and rear end frames of the storage tank also includes a method for correcting the parallelism of the end faces of the front and rear end frames, including: The bottom support ring of the tank is fixed. The coordinates of the lifting mechanism connected to the lifting ring are corrected based on the calculated parallelism between the end frame connecting surface of the bottom support ring and the end frame connecting surface of the lifting ring. The corrected coordinate values ​​are then updated to new parallelism reference coordinates. The pose of the end frame connecting surface of the lifting ring is adjusted based on the new parallelism reference coordinates to regulate the parallelism between the end frame connecting surface of the bottom support ring and the end frame connecting surface of the lifting ring, thereby controlling the parallelism of the front and rear end frame end faces of the tank within a predetermined parallelism range.

6. The method according to claim 1, characterized in that, The method for controlling the coaxiality of the mating surfaces of the front and rear end frames of the storage tank includes a method for measuring the coaxiality of the mating surfaces of the front and rear end frames, including: A laser measuring instrument is set at the center point of the lifting ring, and a laser target is set at the center point of the bottom support ring. Before the storage tank is put on the shelf, the position of the laser target point is measured by the target. The coaxiality of the connection surface of the bottom support ring end frame and the connection surface of the lifting ring end frame is calculated based on the target point offset of multiple target point positions.

7. The method according to claim 6, characterized in that, The method for controlling the coaxiality of the mating surfaces of the front and rear end frames of the storage tank also includes: The bottom support ring of the tank is fixed. The lifting ring is corrected based on the coaxiality of the end frame connection surface of the bottom support ring and the end frame connection surface of the lifting ring. The corrected coordinate values ​​are updated to new coaxiality reference coordinates. The center point position of the lifting ring is adjusted based on the new coaxiality reference coordinates to regulate the coaxiality of the end frame connection surface of the lifting ring and the end frame connection surface of the bottom support ring, and to control the coaxiality of the front and rear end frame mating surfaces of the tank within a predetermined coaxiality range.

8. The method according to claim 6, characterized in that: The theoretical center points of the connection surfaces of the bottom support ring end frame and the lifting ring end frame are determined and marked when the positioning pin holes and connection holes are machined by CNC machining.

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