Field measuring, positioning and machining method for machining large spherical shell assembly

Abstract

The invention relates to the technical field of oversized component in-situ machining, and discloses an on-site measuring, positioning and machining method for large spherical shell assembly machining, which comprises the following steps: building a rotary arched on-site machining system and establishing a three-dimensional space coordinate system of a large spherical shell assembly; an external laser tracker of the large spherical shell assembly establishes direct connection with a three-dimensional space coordinate system through the transfer station measuring points, and the external laser tracker guides a robot to complete trepanning machining of the large spherical shell assembly; counting the trepanning form of the large spherical shell assembly and carrying out overall machining planning; and performing trepanning processing according to the overall processing plan, and synchronously adopting an iterative sphere center fitting method. According to the technical scheme, the direct relation with the coordinate system is established through the transfer station measuring points, trepanning of the spherical shell is completed, then the influences of different trepanning positions and trepanning shapes under the gravity field are comprehensively considered, overall planning of trepanning is conducted, and the reliability of the machining process of the large spherical shell assembly and the accuracy of a finished product are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of in-situ processing of super-large components, and in particular to an on-site measurement, positioning and processing method for processing large spherical shell components. Background Art

[0002] Affected by the processing stress and the change in deadweight after material removal, the multi-hole processing of the spherical shell will cause large deformation of the spherical shell, deviation of the spherical center reference, and difficulty in processing.

[0003] According to some data, the existing technology puts forward the following basic requirements for the tooling at the processing site based on the preliminary processing process arrangement: A reinforced concrete platform with a diameter of not less than 18m is built as the installation platform for the spherical shell components and processing equipment; Lay the gantry rotary guide rail on the ground, requiring the parallelism of the guide rail to be better than 5mm with the horizontal plane, set the transfer station auxiliary measurement points, and establish a fixed reference coordinate system; An adjustment base for placing the ball shell is installed at the center of the guide rail so that the distance between its central axis and the center of the guide rail is less than 5mm. A ball shell positioning pin is provided at the center of the base. The spherical shell assembly with a Φ2500mm hole machined is hoisted onto the base at the center of the platform. The center normal of the target base is measured and fitted. Based on this, the position of the spherical shell assembly relative to the tool rail is adjusted so that the distance between the center normal of the guide rail and the center normal of the target base is less than 10mm. Hoist the rotary arch platform onto the mobile base on the circular guide rail, and adjust the arch platform so that the distance between its rotation axis and the center of the guide rail is less than 10mm; hoist the processing equipment onto the rotary arch platform, use a laser tracker to measure and position the processing equipment and the spherical shell of the spherical shell assembly, and prepare for processing.

[0004] Chinese patent document CN107138762B discloses a "method and system for drilling multiple holes in a large spherical shell." This method includes: establishing a three-dimensional spatial coordinate system for the large spherical shell and measuring the three-dimensional data of the large spherical shell; determining the position coordinates of the machining system within the three-dimensional spatial coordinate system; comparing the machining theoretical model of the large spherical shell with the three-dimensional data of the large spherical shell to obtain machining coordinates based on the three-dimensional spatial coordinate system; moving the machining system to drill a hole in the large spherical shell based on the machining coordinates; and repeating the above steps to drill the next hole. This technical solution does not distinguish between different hole opening types in large spherical shell components and lacks an overall plan for machining different hole opening types. Summary of the Invention

[0005] The present invention mainly solves the technical problem that the original technical solution does not distinguish between different opening forms of large spherical shell components and lacks an overall planning for processing different opening forms. It provides an on-site measurement, positioning and processing method for processing large spherical shell components, sets up a laser tracker inside the spherical shell component, measures several distributed points on the spherical surface inside the spherical shell component, fits the center of the sphere and determines the orientation of the reference axis, establishes a processing measurement coordinate system, and the external laser tracker of the spherical shell component establishes a direct connection with the coordinate system through the transfer station measurement point, thereby guiding the milling robot to complete the hole processing of the spherical shell of the spherical shell component through the external laser tracker, and then comprehensively considers the influence of different hole positions and hole shapes under the gravity field, and performs an overall planning of the hole processing to ensure the reliability of the processing process of the large spherical shell component and the accuracy of the finished product.

[0006] The above technical problems of the present invention are mainly solved by the following technical solutions: The present invention comprises the following steps: S1. Build a rotary arch field processing system and establish a three-dimensional spatial coordinate system for large spherical shell components; S2. The external laser tracker of the large spherical shell component establishes a direct connection with the three-dimensional spatial coordinate system through the transfer station measurement point. The external laser tracker guides the robot to complete the hole drilling of the large spherical shell component. S3. Count the hole patterns of large spherical shell components and make overall processing plans; S4. Perform hole drilling according to the overall machining plan and simultaneously adopt the iterative sphere center fitting method.

[0007] Preferably, the rotary arch field processing system comprises a rotary arch platform, a self-leveling mobile trolley, a robot processing system and a laser tracker measurement system; The arched platform adopts a three-dimensional arched structure, and multiple layers of working platforms are built between the arched platforms; The self-leveling mobile trolley moves along the arched platform and has the functions of autonomous movement, automatic locking and automatic leveling; The robotic processing system uses industrial robots and processing equipment; The tracker measurement system includes laser trackers arranged inside and outside the large spherical shell assembly to build an on-site high-precision measurement network.

[0008] Preferably, the establishment of the processing measurement coordinate system includes setting up a laser tracker inside the large spherical shell assembly, measuring a number of distributed points on the spherical surface inside the large spherical shell assembly, fitting the center of the sphere and determining the orientation of the reference axis, and establishing the processing measurement coordinate system.

[0009] Preferably, the step S2 specifically includes determining the robot processing coordinate system by a fixed-point measurement method when drilling holes, adopting a four-point measurement method during fine-machining holes and flange welding auxiliary assembly, using the fixed-point method to measure the robot base coordinate system B, and obtaining the position of the robot base coordinate system R through the relationship between the robot base coordinate system B and the robot base coordinate system R; the four-point measurement method is specifically to repeatedly move the robot end to 4 points in space, and the laser tracker measures the average position of the 4 points, and fits a virtual coordinate system V. The robot solves the conversion relationship between the virtual coordinate system V and its own base coordinate system R, thereby indirectly measuring the robot base coordinate system.

[0010] Preferably, the overall planning of the processing includes the following hole opening principles: first open the low-precision hole system and then the high-precision holes; open the large holes first and then the small holes, use a support structure for the large circular holes, and use a positioning welding process to fix the flange for the large square holes; after most of the flange holes are opened, the internal stress of the spherical shell is stable. After all the holes are opened and stabilized for a period of time, all the spherical shell holes are re-inspected and refined, and then the flange installation and adjustment operation is carried out.

[0011] Preferably, the overall planning of the processing specifically includes: S3.1. Measure the center of the spherical surface of the large spherical shell assembly. Open a light-transmitting hole on the inner surface. Use an external measuring station to determine the center of the large spherical shell assembly, which serves as a reference for machining the shell hole. Weld a material removal bracket to the inner surface of the shell where the hole is to be cut to support the sheet metal during cutting. S3.2. First, machine the spherical shell hole corresponding to the reference flange hole; S3.3. Next, process the other flange holes to correspond to the spherical shell holes. S3.4 The next step is to process the ordinary circular flange hole to correspond to the spherical shell hole; S3.5. Finally, process square and high-precision circular spherical shell holes; S3.6. Recheck all spherical shell holes taking into account residual stress and deformation, and perform secondary refinement on holes that do not meet the requirements.

[0012] Preferably, after the hole processing, hole detection is performed, specifically including: The longitude and latitude deviations of the centers of all reference spherical shell holes are tested to be less than 1', and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 2mm; the longitude and latitude deviations of the centers of all other spherical shell holes are tested to be less than ±2.5', and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 5mm; the longitude and latitude deviations of the centers of all ordinary circular spherical shell holes are tested to be less than 3', and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 5mm; the longitude and latitude deviations of the centers of all square and high-precision circular holes are tested to be less than 1', and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 2mm.

[0013] Preferably, the hole opening processing follows the principle of opposite-side hole opening, adopts a top-down hole opening sequence, first roughly opening the "Y"-shaped weld interface and the flange hole at the weld, and after processing the flange holes at other places, the "Y"-shaped weld interface and the flange hole at the weld are refined.

[0014] Preferably, the iterative sphere center fitting method specifically includes measuring the accuracy of all holes after processing a batch of flange holes, and fitting and adjusting the sphere center position according to the measurement information.

[0015] As a preference, large holes should be processed first and small holes later. For large-diameter square flange holes, they need to be opened simultaneously when some holes in the upper half area are opened, and the flanges should be assembled in place and fixed with positioning welding to reduce local deformation.

[0016] The beneficial effects of the present invention are as follows: a laser tracker is set up inside the spherical shell assembly to measure several distributed points on the spherical surface inside the spherical shell assembly, the center of the sphere is fitted and the orientation of the reference axis is determined, and a processing measurement coordinate system is established. The laser tracker outside the spherical shell assembly establishes a direct connection with the coordinate system through the transfer station measurement point, thereby guiding the milling robot to complete the hole opening processing of the spherical shell of the spherical shell assembly through the external laser tracker, and then comprehensively considering the hole opening positions and hole shapes of different holes to carry out overall processing planning, thereby ensuring the accuracy and reliability of the finished product of the large spherical shell assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a circuit principle connection structure block diagram of the present invention.

[0018] Figure 2 This is a connection diagram between the center of an internal measuring sphere shell assembly and an external measuring system of the present invention.

[0019] Figure 3 This is a schematic diagram of the hole positioning principle of the present invention.

[0020] Figure 4 This is a schematic diagram of a fixed point method for measuring a robot base coordinate system according to the present invention.

[0021] Figure 5 This is a schematic diagram of a four-point method for measuring a robot base coordinate system according to the present invention.

[0022] Figure 6 This is a schematic diagram of measuring the end posture of a robot according to the present invention.

[0023] Figure 7 This is a finite element simulation diagram of a spherical shell under a gravity field before a hole is opened.

[0024] Figure 8 This is a finite element simulation diagram of a spherical shell with holes opened on the equatorial plane (excluding large holes) under a gravity field according to the present invention.

[0025] Figure 9 This is a finite element simulation diagram of a spherical shell with a hole (including a large hole) opened on the equatorial plane under a gravity field of the present invention.

[0026] Figure 10 This is a finite element simulation diagram of a spherical shell in a gravity field after a hole is opened in the upper half area of ​​the shell.

[0027] Figure 11 This is a flow chart of sphere center fitting and adjustment during the process of opening a hole in a spherical shell according to the present invention.

[0028] Figure 12 This is a structural diagram of a rotary arched platform of the present invention. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clear, the technical solutions of the present application are further described in detail below through examples and in combination with the accompanying drawings. It should be understood that the specific implementation method described here is only an optimal embodiment of the present application, which is only used to explain the present application and does not limit the scope of protection of the present application. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] The technical solution of the present invention will be further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0031] Example 1: This embodiment is a field measurement, positioning and processing method for large spherical shell components, such as Figure 1 As shown, the following steps are included: S1. Build a rotary arch field processing system and establish a three-dimensional coordinate system for the large spherical shell assembly. The rotary arch field processing system includes a rotary arch platform, a self-leveling mobile vehicle, a robotic processing system, and a laser tracker measurement system. The arched platform adopts a three-dimensional arched structure, with multiple layers of working platforms built between the arched platforms; The self-leveling mobile trolley moves along the arched platform and has the functions of autonomous movement, automatic locking and automatic leveling; The robotic processing system uses industrial robots and processing equipment; The tracker measurement system includes laser trackers placed inside and outside the large spherical shell assembly to establish an on-site high-precision measurement network.

[0032] Establishing a processing measurement coordinate system includes setting up a laser tracker inside the large spherical shell component, measuring a number of distributed points on the spherical surface inside the large spherical shell component, fitting the center of the sphere and determining the orientation of the reference axis, and establishing the processing measurement coordinate system.

[0033] S2. The external laser tracker of the large spherical shell component establishes a direct connection with the three-dimensional spatial coordinate system through the transfer station measurement point. The external laser tracker guides the robot to complete the hole drilling of the large spherical shell component. Specifically, the robot processing coordinate system is determined by the fixed point measurement method during hole drilling. The four-point measurement method is used during the fine hole machining and flange welding auxiliary assembly. The fixed point method is used to measure the robot base coordinate system B. The position of the robot base coordinate system R is obtained through the relationship between the robot base coordinate system B and the robot base coordinate system R. The four-point measurement method is specifically to repeatedly move the robot end to four points in space. The laser tracker measures the average position of the four points and fits a virtual coordinate system V. The robot solves the transformation relationship between the virtual coordinate system V and its own base coordinate system R, thereby indirectly measuring the robot base coordinate system.

[0034] S3. Count the hole patterns of large spherical shell components and develop an overall machining plan. This overall machining plan includes the following drilling principles: drill low-precision holes first, followed by high-precision holes; drill large holes first, followed by small holes; utilize support structures for large circular holes; and secure flanges with tack welding for large square holes. After most flange holes are drilled and the internal stress of the spherical shell stabilizes, and after all holes have stabilized for a period of time, re-inspect and refine all spherical shell holes before proceeding with flange assembly and adjustment.

[0035] The hole opening processing follows the principle of opposite-side hole opening, and adopts a top-down hole opening sequence. First, the "Y"-shaped weld interface and the flange hole at the weld are roughly opened. After processing the flange holes at other places, the "Y"-shaped weld interface and the flange hole at the weld are refined.

[0036] The overall planning of processing specifically includes: S3.1. Measure the center of the spherical surface of the large spherical shell assembly. Open a light-transmitting hole on the inner surface. Use an external measurement station to obtain the center position of the large spherical shell assembly, which serves as the datum for machining the spherical shell hole. Weld a material removal bracket to the inner surface of the spherical shell where the spherical shell hole is to be cut to hold the sheet metal during cutting.

[0037] S3.2. First, machine the spherical shell holes corresponding to the reference flange holes; check that the longitude and latitude deviations of the centers of all reference spherical shell holes are less than 1′, and that the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 2 mm.

[0038] S3.3. Next, process the other flange holes corresponding to the spherical shell holes; check that the longitude and latitude deviations of the centers of all other spherical shell holes are less than ±2.5′, and that the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 5 mm.

[0039] S3.4 The next step is to process the ordinary circular flange hole corresponding to the spherical shell hole; check that the longitude and latitude deviation of the center of all ordinary circular spherical shell holes is less than 3', and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 5mm.

[0040] S3.5. Finally, process the square and high-precision circular spherical shell holes; check that the longitude and latitude deviations of the centers of all square and high-precision circular holes are less than 1′, and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 2mm.

[0041] S3.6. Recheck all spherical shell holes taking into account residual stress and deformation, and perform secondary refinement on holes that do not meet the requirements.

[0042] In order to formulate a reasonable opening sequence, the following finite element simulation analysis is carried out.

[0043] Since most of the welding residual stress has been eliminated through the heat treatment process, the weight of the spherical shell is the main factor causing the deformation of the spherical shell during the hole opening process. Figure 7 It can be seen that after welding, the deformation of the spherical shell in the gravity field environment is 0.17mm, and the overall stiffness of the spherical shell is good. Figure 8 First, the hole system on the equatorial plane is processed. The deformation of the spherical shell is 0.17mm. After processing the large flange hole on the equator, Figure 9 As shown, the maximum local deformation is 0.39 mm, so the enlarged flange hole will significantly weaken the stiffness of the spherical shell. Therefore, after the hole is opened, local stiffness enhancement measures need to be taken.

[0044] like Figure 10 As shown in the figure, after drilling some holes in the upper half of the sphere, the shell deformation under gravity is 0.15mm. The center position is basically the same after drilling the holes in the upper half of the sphere and before drilling. After drilling all the holes, the shell deformation under gravity is 0.42mm. The center deformation is relatively large, so multiple measurements are required during the drilling and welding process to re-fit the center.

[0045] After all flange surfaces were welded, finite element simulation was performed under a gravity field. The maximum deformation was 0.33 mm. Compared with the spherical shell before and after the hole was opened, the spherical center coordinate system changed significantly. During the welding process, an iterative fitting method was used to adjust the spherical center coordinate system according to the measurement results of the welded flange to improve the accuracy of the hole opening and flange installation.

[0046] S4. Perform hole drilling according to the overall machining plan and simultaneously employ an iterative sphere center fitting method. This method involves measuring the accuracy of all flange holes after machining a batch of them, fitting and adjusting the sphere center position based on the measured information. Large holes are machined first, followed by smaller holes. For large-diameter square flange holes, the holes in the upper half of the flange area must be drilled simultaneously with the holes in the upper half. The flange is then assembled and secured using tack welding to minimize local deformation.

[0047] Example 2: The object of this processing is the spherical shell assembly of the vacuum spherical shell subsystem of the laser nuclear fusion system. This assembly consists of the spherical shell, its welded flange, and a transition joint structure. The overall processing route for the spherical shell assembly is as follows: each spherical lobe is hot-pressed at the processing plant, and then three spherical lobes are welded together to form a large spherical lobe, resulting in a total of six large spherical lobes. The spherical shell is then transported to a temporary processing shed near the main target range for the overall welding of the spherical shell. After the spherical shell is formed, the hole drilling and flange welding processes are completed. Finally, the spherical shell assembly is hoisted from the temporary processing shed to the vertical support base at the target range for final precision repair, debugging, and installation. The main repair parts are the adjustment gaskets on the welded flanges. Table 1 shows the main precision indicators for the processing and installation of the spherical shell assembly. In response to the above processing requirements of the spherical shell assembly, this processing technology mainly focuses on the spherical shell hole drilling and welded flange repair processes. The goal is to complete the on-site processing of circular and square holes of various sizes on the spherical shell and complete the on-site repair of the welded flanges.

[0048] The inner diameter of the spherical shell is 11m, the wall thickness is 110mm, and it is welded from 18 identical spherical petals made of aluminum alloy 5083-O. 74 square flanges, 7 high-precision round flanges, 1 large-diameter square flange and 150 ordinary round flanges need to be welded on it. It has a large number of openings and a short processing cycle. At the same time, the influence of welding residual stress needs to be considered.

[0049] To address the above issues, the project team designed a rotary arch processing and assembly integrated platform based on many years of experience in large-scale non-standard equipment manufacturing and super-large component processing. The milling robot was used to perform rough and fine drilling, which can meet the drilling needs of all positions of the spherical shell. The Φ2300 and 2900×2000 hole systems were processed using a multiple splicing method. Other square holes and round holes can be drilled at one station at one time. Two robots were used for parallel processing to improve the drilling efficiency.

[0050] Considering the influence of residual stress, the following drilling principles were formulated: low-precision holes were drilled first, followed by high-precision holes; large holes were drilled first, followed by small holes; support structures were used for Φ2300 holes, and tack welding was used to secure flanges for 2900×2000 square holes; holes on the weld seam were rough-drilled and then fine-tuned before flange installation; and tack welding was used to secure flanges when machining equatorial holes. Due to the long drilling cycle and the fact that flange holes at the weld seam were drilled in advance, the internal stress of the spherical shell stabilized after most of the flange holes were drilled, resulting in minimal deformation. After all holes were drilled and stabilized for a period of time, all spherical shell holes were re-inspected and fine-tuned before flange installation and adjustment.

[0051] Table 1 Main precision indicators for the processing, installation and use of spherical shell components

[0052] Spherical shell assemblies are typically heavy and large components, making conventional large-scale machining equipment difficult to meet their processing requirements. Developing dedicated large-scale machining equipment would be costly and time-consuming, and would be extremely challenging. Therefore, this task proposes the development of an integrated machining, assembly, and measurement system, using a mobile robot to perform on-site spherical shell hole drilling and flange assembly.

[0053] This project utilizes an integrated machining and assembly platform. Because it eliminates line drawing errors and portable machine tool installation errors, and utilizes an internal tracker system for hole refinement, it ensures that the center longitude and latitude errors meet or exceed design specifications. It's worth noting that due to the long release period of residual stress, slight deformation of the spherical shell typically occurs only in the later stages of hole drilling. Considering the amount of adjustment required for subsequent flange installation, ensuring center longitude and latitude is the primary factor in adjusting the spherical center coordinate system, followed by centration deviation and aperture size, particularly regarding the center longitude and latitude deviation of high-precision flange holes.

[0054] The on-site processing system consists of four parts: a rotary arch platform, a self-leveling mobile car, a robot processing system, and a laser tracker measurement system. Figure 12 As shown, the arch platform adopts a three-dimensional arch structure, which has good stability and high rigidity. At the same time, multi-layer working platforms are built between the arch platforms, which on the one hand enhances the structural stability and on the other hand can also be used as a construction platform; the self-leveling mobile trolley can move along the arch platform and has autonomous movement, automatic locking and automatic leveling functions; the robot system adopts commercial industrial robots and processing equipment with high technical maturity. Two robots are used to work together to improve the processing and assembly efficiency. A symmetrical or same-side layout can be adopted according to the needs of production tasks; the tracker measurement system uses more than four trackers on site to build an on-site high-precision measurement network to guide the processing of processing equipment throughout the process.

[0055] This project combines existing technologies to develop an integrated control system for processing, measurement, and assembly. During the welding and processing of the spherical shell, a measurement and measurement data rapid processing software system, a rotary platform motion control system, a mobile trolley control system, a robot CNC system (processing trajectory planning and processing program generation), a flange posture rapid adjustment system, and an iterative measurement system for the center of the sphere during flange welding are developed on the host computer. The system hardware communicates via TCP / IP to build a "processing_assembly_measurement" control system to ensure data traceability throughout the manufacturing cycle and achieve high-precision and efficient processing and assembly. After the spherical shell assembly is hoisted, a measurement and data rapid processing software system, a spherical shell assembly fine-tuning calculation system, a gasket repair system, and a final inspection information database are developed to achieve rapid adjustment of the spherical shell assembly and one-click optimization and generation of gasket repair data, and provide database support for the later use of the spherical shell assembly.

[0056] Project processing and assembly process such as Figure 11 As shown, the revolving arched platform rotates along the guide rail around the axis of the spherical shell and, when it moves to a specified position, the arched processing platform is fixed. The robotic processing system is mounted on a mobile platform, which can move along the guide rail to reach any processing position on the surface of the spherical shell. The robot position is adjusted under the guidance of a laser tracker, and the robotic CNC system generates a processing program based on the measurement information to perform the spherical shell hole drilling. After completing the drilling task, this processing system can also serve as an auxiliary adjustment fixture for flange welding, achieving integrated processing and assembly. During the flange welding process, the flange positioning surface information is measured using an auxiliary measuring device, and the spherical center coordinate system is adjusted online based on the fitted spherical center of the welded flange, achieving "online measurement and spherical center iteration" to ensure high-precision installation of the spherical shell flange.

[0057] The drilling process adopts the method of "drilling holes in batches, iterating online, starting with low and then high, concentrating the area, and starting with large and then small". After completing one stage of drilling tasks, the flange hole position accuracy and centering accuracy are re-checked. Due to the release of residual stress and the deformation of the spherical shell structure, the center of the spherical shell will change slightly, causing the flange hole accuracy to change. In the drilling process, an iterative spherical center fitting method is used, that is, after processing a batch of flange holes, the accuracy of all holes is measured, and the spherical center position is fitted and adjusted based on the measurement information. Since the longitude and latitude of the center of the rectangular flange hole and the centering accuracy requirements are relatively high, the rectangular hole is processed after other holes are processed to reduce the impact of the spherical shell deformation and reduce the number of iterative adjustments to the spherical center. See the drilling process for details. Figure 11 .

[0058] Considering that the release of welding residual stress and the weight of the spherical shell are the main factors causing the change of the spherical shell center coordinate system during the hole opening process, based on the spherical shell simulation results and the above hole opening principles, the following more targeted hole opening criteria are initially formulated: (1) After the large spherical petals at the north and south poles of the spherical shell are formed, the 2500 and 2200 dia. flange holes are first processed in the processing factory. The top flange hole is pre-opened to 1500 dia. in the factory, and then further expanded to the range to be processed at the processing site; (2) To reduce the deformation of the spherical shell, the principle of opening holes on the opposite side is followed and the order of opening holes from top to bottom is adopted; (3) Adopt a reasonable layout to reduce the overlap between flange holes and welds. First, roughly open the flange holes at the "Y"-shaped weld interface and the weld, then process the flange holes at other locations, and then fine-tune the flange holes to reduce the influence of residual stress and deformation; (4) In order to reduce the influence of the deformation of the spherical shell during the drilling process, the holes with low precision requirements should be processed first, and the holes with higher precision requirements should be processed last. When drilling, the position of the fitting sphere center should be adjusted repeatedly and appropriately to reduce the drilling error; (5) Process large holes first and small holes later. For large-diameter square flange holes, it is necessary to complete the hole after completing the opening of the upper half of the area. According to simulation analysis, the local deformation is large after the hole is opened. Therefore, the flange needs to be assembled in place and fixed with a positioning welding process to reduce local deformation. (6) Process the holes in the same area first to reduce the adjustment time. Where the flange holes are concentrated, high-precision holes are reserved for support (i.e., unloading before welding) to reduce welding deformation; (7) There are many openings on the equatorial plane, which have a certain impact on the stiffness of the entire spherical shell. Therefore, the corresponding flanges are assembled in place when the holes are opened on the equatorial plane, and the flanges are fixed by positioning welding to improve the overall support stiffness of the spherical shell.

[0059] The cutting parameters are optimized by harmonic response analysis of the rotary platform. When the spindle speed is above 2000 rpm, the machining platform is less affected by the stimulated vibration and stable machining can be achieved.

[0060] The spherical shell component is made of aluminum alloy, and the drilling precision required is high. Current industrial robots generally have a repeatability accuracy of 0.08mm, which meets the machining requirements of this project. The selection of an industrial robot requires consideration of the robot's machining range. This processing object is an 11m diameter spherical shell, and the robot needs to be positioned at various locations outside the shell. The robot's basic machining range at each fixed position must be determined in advance.

[0061] In addition to the large square flange and 2200mm adapter assembly, the flange hole and its flange determine the basic processing space of 1600×1600×720mm. To enable the robot to reach any processing position on the sphere, a rotating arch-shaped three-dimensional support platform is used to ensure processing at any position.

[0062] Based on the machining range, a KR 600 FORTEC 2830-C robotic milling system was selected. It has an end-load capacity of 600 kg, a repeatability of 0.08 mm, and a machining range of up to 2.8 m. The robot is controlled by a KR C4 controller. A modular spindle system is installed at the end-of-line. The end-of-line load capacity of the robot varies with the position of its center of mass relative to the robot's end-of-line coordinate system. Therefore, proper selection of cutting parameters and the proper positioning of the end-of-line spindle system ensure proper robot operation.

[0063] After installing the electric spindle system, the robot end can withstand milling forces of 1000 to 4000N. Appropriate cutting parameters were selected based on modal analysis of the arched platform, and the calculated milling force was approximately 300N. To ensure safety and reliability, 2000N was used as the robot end cutting load, and 1500N was used as the spindle module static load. Based on the spindle module structural design, Lx = 400mm, Lz = 200mm. Based on this information, the static and dynamic loads of each robot axis were calculated. The dynamic load calculation of the robot takes into account the effects of acceleration and speed. The milling load is within the robot's load capacity, ensuring stable cutting.

[0064] According to finite element analysis, after the robot is loaded on the arch platform, the milling force on the end becomes less than 0.2mm, and the deformation of the arch platform is small, which can meet the processing requirements.

[0065] Robot milling allows for separate roughing and finishing operations. For finishing, a profiled grinding wheel can be mounted on the electric spindle to grind the inner wall of the spherical shell hole to the desired dimensions. The selected robot's machining accuracy meets the requirements for spherical shell hole machining, which include: deviations in latitude and longitude from the center of the reference flange hole, square, and high-precision circular spherical shell holes to better than ±1mm; dimensional accuracy to better than ±0.1mm; and a distance between the hole axis and the center of the spherical shell assembly to less than 5mm.

[0066] The industrial robot selected for this process can also be used for auxiliary positioning and adjustment tooling during flange welding. Except for large square flanges, the heaviest flange that needs to be welded is a square flange weighing less than 400kg. According to calculations, this weight is within the load range of the selected industrial robot. The robot's position adjustment resolution is 0.01mm, and the posture adjustment resolution is 0.01°, which can fully meet the auxiliary positioning and adjustment requirements during flange welding.

[0067] The specific embodiments described herein are merely examples of the spirit of the present invention. The above embodiments only express several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of protection of the present application. It should be pointed out that those skilled in the art of the present application can make various modifications or supplements to the described specific embodiments or replace them in a similar manner, but they will not deviate from the spirit of the present application or exceed the scope defined by the appended claims. For those of ordinary skill in the art, multiple variations and improvements can be made without departing from the concept of the present application. Therefore, the scope of protection of the present application should be based on the appended claims.

Claims

1. A method for on-site measurement, positioning and processing of large spherical shell components, characterized in that: The following steps are involved: S1. Build a rotary arch field processing system and establish a three-dimensional spatial coordinate system for large spherical shell components; S2. The external laser tracker of the large spherical shell component establishes a direct connection with the three-dimensional spatial coordinate system through the transfer station measurement point. The external laser tracker guides the robot to complete the hole drilling of the large spherical shell component. S3. Count the hole patterns of large spherical shell components and make overall processing plans; S4. Perform hole drilling according to the overall machining plan and simultaneously adopt the iterative sphere center fitting method.

2. The on-site measurement, positioning and processing method for large spherical shell components according to claim 1 is characterized in that: The rotary arch field processing system includes a rotary arch platform, a self-leveling mobile trolley, a robot processing system and a laser tracker measurement system; The arched platform adopts a three-dimensional arched structure, and multiple layers of working platforms are built between the arched platforms; The self-leveling mobile trolley moves along the arched platform and has the functions of autonomous movement, automatic locking and automatic leveling; The robotic processing system uses industrial robots and processing equipment; The tracker measurement system includes laser trackers arranged inside and outside the large spherical shell assembly to build an on-site high-precision measurement network.

3. The on-site measurement, positioning and processing method for large spherical shell components according to claim 1 is characterized in that: The establishment of the processing measurement coordinate system includes setting up a laser tracker inside the large spherical shell component, measuring a number of distributed points on the spherical surface inside the large spherical shell component, fitting the spherical center and determining the reference axis orientation to establish the processing measurement coordinate system.

4. The on-site measurement, positioning and processing method for large spherical shell components according to claim 1 or 2, characterized in that: The step S2 specifically includes determining the robot processing coordinate system by a fixed-point measurement method when drilling holes, adopting a four-point measurement method when fine-machining holes and flange welding auxiliary assembly, using the fixed-point method to measure the robot base coordinate system B, and obtaining the position of the robot base coordinate system R through the relationship between the robot base coordinate system B and the robot base coordinate system R; the four-point measurement method specifically involves repeatedly moving the robot end to four points in space, measuring the average position of the four points with a laser tracker, fitting a virtual coordinate system V, and the robot solving the conversion relationship between the virtual coordinate system V and its own base coordinate system R, thereby indirectly measuring the robot base coordinate system.

5. The on-site measurement, positioning and processing method for large spherical shell components according to claim 1, characterized in that: The overall planning of the processing includes the following hole opening principles: open the low-precision hole system first and then the high-precision holes; open the large holes first and then the small holes, use a support structure for the large round holes, and use a positioning welding process to fix the flange for the large square holes; after most of the flange holes are opened, the internal stress of the spherical shell is stable. After all the holes are opened and stabilized for a period of time, all the spherical shell holes are re-inspected and refined, and then the flange installation and adjustment operation is carried out.

6. The on-site measurement, positioning and processing method for large spherical shell components according to claim 1, characterized in that: The overall planning of the processing specifically includes: S3.

1. Measure the center of the spherical surface of the large spherical shell assembly. Open a light-transmitting hole on the inner surface. Use an external measuring station to determine the center of the large spherical shell assembly, which serves as a reference for machining the shell hole. Weld a material removal bracket to the inner surface of the shell where the hole is to be cut to support the sheet metal during cutting. S3.

2. First, machine the spherical shell hole corresponding to the reference flange hole; S3.

3. Next, process the other flange holes to correspond to the spherical shell holes. S3.4 The next step is to process the ordinary circular flange hole to correspond to the spherical shell hole; S3.

5. Finally, process square and high-precision circular spherical shell holes; S3.

6. Recheck all spherical shell holes taking into account residual stress and deformation, and perform secondary refinement on holes that do not meet the requirements.

7. The on-site measurement, positioning and processing method for large spherical shell components according to claim 6, characterized in that: After the hole processing, hole detection is performed, which specifically includes: The longitude and latitude deviations of the centers of all reference spherical shell holes are tested to be less than 1', and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 2mm; the longitude and latitude deviations of the centers of all other spherical shell holes are tested to be less than ±2.5', and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 5mm; the longitude and latitude deviations of the centers of all ordinary circular spherical shell holes are tested to be less than 3', and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 5mm; the longitude and latitude deviations of the centers of all square and high-precision circular holes are tested to be less than 1', and the distance between the axis of the spherical shell hole and the center of the large spherical shell assembly is less than 2mm.

8. The on-site measurement, positioning and processing method for large spherical shell components according to claim 1, 5 or 6, characterized in that: The hole opening process follows the principle of opposite-side hole opening and adopts a top-down hole opening sequence. First, the "Y"-shaped weld interface and the flange hole at the weld are roughly opened. After processing the flange holes at other locations, the "Y"-shaped weld interface and the flange hole at the weld are refined.

9. The on-site measurement, positioning and processing method for large spherical shell components according to claim 1, 5 or 6, characterized in that: The iterative sphere center fitting method specifically includes measuring the accuracy of all holes after machining a batch of flange holes, and fitting and adjusting the sphere center position according to the measurement information.

10. The on-site measurement, positioning and processing method for large spherical shell components according to claim 1, 5 or 6, characterized in that: Large holes should be processed first, and small holes should be processed later. For large-diameter square flange holes, they need to be opened simultaneously when some holes in the upper half area are opened, and the flanges should be assembled in place. The flanges should be fixed with positioning welding to reduce local deformation.

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