Measuring and adjusting method and system for large spherical shell flange assembly

Abstract

The invention discloses a measuring and adjusting method and system for assembling a large spherical shell flange, and relates to a measuring and adjusting method and system for assembling a spherical shell flange. The problems that in a traditional assembling technology, due to flange hole manufacturing errors, flanges cannot be aligned to theoretical poses, the poses of the flanges are difficult to evaluate rapidly in the assembling process, the flanges are difficult to position, and the flanges are difficult to adjust through a mechanism due to the fact that the assembling space is limited are solved. The method comprises the following steps: evaluating the optimal reachable pose of a flange by adopting an improved non-dominated sorting algorithm based on the manufacturing error of a flange mounting hole; calibrating a flange coordinate system; positioning based on the measured value of the distance between the flange mounting hole corner point and the sphere center; establishing a theoretical flange coordinate system in the sphere center coordinate system according to the assembly process requirements of the flange; and theoretical coordinate information of the auxiliary positioning point under the spherical center coordinate system is obtained. The invention belongs to the technical field of high-precision assembly and measurement of flange parts.

Description

Technical Field

[0001] The invention relates to a measurement and adjustment method and system for spherical shell flange assembly, belonging to the technical field of high-precision assembly and measurement of flange parts. Background Art

[0002] In large spherical shell pressure vessels, flanges are important connecting components between the spherical shell and the pipeline. Their high-precision assembly is a key link to ensure the normal operation of the pressure vessel device. Due to the curvature and complex geometric characteristics of the spherical shell, it is a technical challenge to accurately position and install the flange on its surface. Traditional assembly technology has a series of problems such as flange hole manufacturing errors causing the flange to be unable to align to the theoretical posture, difficulty in quickly evaluating the flange posture during assembly, difficulty in flange positioning, and difficulty in adjusting the flange through mechanisms due to limited assembly space. The invention patent with publication number CN116929252A and application date July 18, 2023 discloses an assembly measurement method, device, system, equipment and storage medium for a flange structure, which involves the fields of assembly and measurement technology, wherein the method is as follows: obtaining a first end face image group before assembly of the flange structure to be measured and a second end face image group after assembly by bolts, which are captured by at least one group of binocular cameras; obtaining first point cloud data corresponding to the first end face image group and second point cloud data corresponding to the second end face image group; determining the coaxiality error of the flange structure to be measured and the surface error corresponding to each bolt area on the flange structure to be measured based on the first point cloud data and the second point cloud data; and performing assembly adjustment on the flange structure to be measured based on the coaxiality error and the surface error. This application processes the end face image group before and after assembly of the flange structure, and quantifies the deformation or assembly effect of the flange structure by the coaxiality error and the surface error, which can optimize the sealing performance of the flange structure and help reduce the number of adjustments. This method and system are not suitable for the assembly technology of large vacuum spherical shell flanges, and they cannot solve a series of problems such as alignment to the theoretical posture, difficulty in quickly evaluating the posture of the flange during assembly, difficulty in positioning the flange, and difficulty in adjusting the flange through the mechanism due to limited assembly space.

[0003] In view of the above problems, the present invention proposes an assembly method for the flange assembly process, thereby efficiently completing the high-precision assembly task of the flange. Summary of the Invention

[0004] The present invention aims to solve the problems in traditional assembly technology such as flange hole manufacturing errors causing the flange to be unable to align to the theoretical position, difficulty in quickly evaluating the flange position during assembly, difficulty in flange positioning, and difficulty in adjusting the flange through a mechanism due to limited assembly space. A measurement and adjustment method and system for large spherical shell flange assembly are proposed.

[0005] The technical solution adopted by the present invention to solve the above problems is: the steps of the measurement and adjustment method for assembling a large spherical shell flange of the present invention include: Step 1: Based on the manufacturing error of the flange mounting hole, the improved non-dominated sorting algorithm is used to evaluate the optimal reachable pose of the flange; Step 2: calibrate the flange coordinate system to obtain the coordinate information of the auxiliary positioning point in the flange coordinate system; Step 3: Locate and weld the flange positioning block based on the measured value of the distance between the corner point of the flange mounting hole and the center of the sphere, insert the flange into the hole, and roughly position the flange with the help of the positioning block; Step 4: Use a laser tracker to measure the coordinate information of the auxiliary positioning point in the spherical center coordinate system, and solve the actual flange coordinate system posture in the spherical center coordinate system based on the coordinate information of the auxiliary positioning point in the flange coordinate system in step 1; Step 5: Establish a theoretical flange coordinate system in the spherical center coordinate system according to the flange assembly process requirements, compare the deviation between the actual flange coordinate system and the theoretical flange coordinate system, calculate the various flange assembly errors, and determine whether the assembly errors meet the requirements. If so, end the assembly and adjustment; if not, proceed to step 6. Step 6. Obtain the theoretical coordinate information of the auxiliary positioning point in the spherical center coordinate system based on the coordinate information of the auxiliary positioning point in the flange coordinate system in step 2 and the position of the theoretical flange coordinate system in the spherical center coordinate system in step 5; spot weld the flange root based on the comparison of the theoretical coordinate and actual coordinate information of the auxiliary positioning point to fine-tune the flange position, and then return to step 4.

[0006] Furthermore, in step 1, a flange posture evaluation model is constructed based on the manufacturing error of the flange mounting hole and the flange assembly accuracy requirements. The improved non-dominated sorting algorithm is used to solve the optimal achievable posture parameters of the flange. The specific steps include: Step 101: In the search space of the design variables, divide the range of each variable into m equally spaced intervals, and randomly select a point in each interval as a sampling point; then sample each variable, construct an individual, and use these individuals to form the initial population. P 0; Step 102: Calculate the fitness value of each generated individual target. After calculating the fitness value, perform non-dominated sorting and crowding calculation on the individuals in the initial population. Step 103: Use a tournament to select parent individuals from the current population. Each time, two groups of individuals are randomly selected for comparison. Individuals with lower non-dominated ranks or higher crowding degrees are selected as parents until N pairs of parent individuals are selected. Step 104: for each pair of parent individuals and Perform a simulated binary crossover operation to generate two offspring individuals and , the expected position of the offspring does not deviate from the mean of the parent generation, and the generation formula of the offspring is: , Where, i Represents the index of the function parameter, β It represents the cross coefficient, and its calculation formula is: , Where, u represents a random number uniformly distributed between 0 and 1. η c Indicates control parameters; when η c When it tends to infinity, the offspring genes are concentrated near the parent generation, achieving local fine search, and when η c When it is smaller, the generated β A more dispersed distribution helps the global system escape from local optimality; Step 105: For each variable in each individual, p m The mutation probability is used to determine whether to mutate; then based on the number of iterations t To set the standard deviation of the variation σ Dynamic adjustment, the standard deviation of the t-th generation variation σ t for: , , represents the initial standard deviation, represents the maximum number of iterations, Indicates the current iteration number; If a variable of the offspring individual x i If variation is required, then from the normal distribution Generate a random value Δx in , and add it to the original variable value to form a variant value; , in, Indicates the value of the gene after the mutation operation, Indicates the number of an individual in the current population i’ The original value of each gene; If the mutated value exceeds the variable's range, the following corrections are made to it: , in, represents the upper bound of the variable, Indicates the lower bound of the variable; Step 106: First, merge the parent population and the child population to generate a temporary population of size 2N. P' ; Calculate the fitness of the population, and then according to the Pareto dominance relationship, divide the population P' is divided into multiple non-dominated layers, where F 1 contains the current best non-dominated individual, F 2 contains the suboptimal non-dominated individuals, and so on; finally, for each individual in the non-dominated layer, its crowding distance D i for: , Where, represents the number of objective functions in the optimization problem, f mi+1 and f mi-1 represents the target value of the adjacent individuals on the target m, f mmax represents the maximum value of the target m, f mmin represents the minimum value of the target m; Step 107: select the population according to the principle of lower non-dominated level first and larger crowding distance second priority. P' Select the next generation population of size N P next , then returns to step 103 and iterates the optimization until the termination condition is reached.

[0007] Furthermore, the various assembly accuracies of the flange are the error of the center position of the flange end face, the error of the vertical distance from the sphere center to the flange end face, and the centering deviation. Their mathematical models are: , Where, Indicates the error of the center position of the flange end face, Indicates the actual position horizontal coordinate of the flange end face center, Indicates the horizontal coordinate of the theoretical position of the center of the flange end face, Indicates the actual position ordinate of the flange end face center, Indicates the theoretical vertical coordinate of the flange end face center. Indicates the assembly accuracy requirements of the flange end face center position, Indicates the error of the flange end face center position in the x direction, Indicates the assembly accuracy requirement of the flange end face center position in the x direction, Indicates the error of the flange end face center position in the y direction, Indicates the assembly accuracy requirement of the flange end face center position in the x direction; , Where, Indicates the error in the vertical distance from the center of the sphere to the flange end face. Indicates the actual distance to the flange center, Indicates the theoretical distance of the flange center, Indicates the assembly accuracy requirement of the vertical distance from the center of the sphere to the flange end face; ; Where, Indicates deviation from the center. Represents the direction vector of the flange end face centerline, represents the position of the center of the sphere, Indicates the position of the center of the flange end face; Indicates deviation from the center. Indicates the assembly accuracy requirements for the center; The error of the center position of the flange mounting hole is: , , Where, Indicates the actual position of the mounting hole in the x direction, Indicates the theoretical position of the mounting hole in the x direction, Indicates the assembly accuracy requirement of the center position of the mounting hole in the x direction, Indicates the actual position of the mounting hole in the y direction, Indicates the theoretical position of the mounting hole in the y direction, Indicates the assembly accuracy requirement of the center position of the mounting hole in the y direction; Therefore, the evaluation model of the flange posture is: .

[0008] Furthermore, in step 2, the flange coordinate system is calibrated by measuring the coordinate information of the flange end face and outer side points in the laser tracker measurement coordinate system, and the end face and four outer side faces of the flange are obtained by fitting the point cloud. The left and right outer side faces and the upper and lower outer side faces are divided into two equal parts to obtain two relatively perpendicular left and right center planes and upper and lower center planes; the intersection of the two center planes and the end face is used as the origin of the flange coordinate system, the normal direction of the flange end face is used as the Z axis of the flange coordinate system, and the normal direction of the left and right center planes is used as the Y axis of the flange coordinate system to establish the flange coordinate system. The position expression of the flange coordinate system in the laser tracker measurement coordinate system is: , ; In step 2, the coordinate information of the auxiliary positioning point in the flange coordinate system is obtained. It is known that the position of the flange coordinate system in the laser tracker measurement coordinate system is L and t. The auxiliary positioning point { P 测量}, the auxiliary positioning point is in the flange coordinate system { P 法兰}The coordinate value expression is: .

[0009] Furthermore, the position of the positioning block relative to the flange end face in step 3 is determined based on the measured value of the distance between the intersection of the four side ridges of the flange mounting hole and the inner wall of the spherical shell and the center of the sphere. Its projection on the flange centerline is M. According to the assembly process requirements, the distance between the flange end face and the center of the sphere is known to be D. The calculation expression for the distance H of the positioning block relative to the flange end face is: H = D - M, After determining the position of the coarse positioning block, weld it to fix it, use the crane to lift the flange, adjust the posture by the hand hoist, insert the flange into the flange mounting hole, and use the positioning block to perform coarse positioning on the flange.

[0010] Furthermore, in step 4, a laser tracker is used to measure the coordinate information of the auxiliary positioning point in the spherical center coordinate system. ,based on and The two point clouds are solved through the point cloud registration algorithm to obtain the actual position of the flange coordinate system in the spherical center coordinate system.

[0011] Furthermore, in step 5, a theoretical flange coordinate system is established in the spherical center coordinate system according to the flange assembly process requirements, the actual flange coordinate system is compared with the theoretical flange coordinate system for deviation, the various assembly errors of the flange are calculated, and it is determined whether the assembly error meets the requirements. If so, the assembly is terminated; if not, step 6 is performed.

[0012] Furthermore, in step 6, based on The theoretical coordinate information of the auxiliary positioning point in the spherical center coordinate system is obtained from the theoretical flange coordinate system posture in the spherical center coordinate system in step 5. ; Based on comparison auxiliary positioning point and The comparison results are used to adjust the flange root by metal inert gas shielded welding. The spot welding operation is performed by metal inert gas shielded welding. The spot welding sequence starts from the flange root corresponding to the auxiliary positioning point with the largest position deviation, and transitions to the corresponding flange root with smaller deviation. During the spot welding process, welding shrinkage allowance is reserved according to the measurement results to ensure that the flange posture still meets the design requirements after the final welding is completed. In this way, the flange posture is finely adjusted, and then return to step 4.

[0013] The measurement and adjustment system for large spherical shell flange assembly described in the present invention includes a storage device, a processor, a laser tracker measurement device, a posture calculation module, an assembly evaluation module and a welding auxiliary module; the processor executes a computer program stored in the storage device to implement the steps of the measurement and adjustment method for large vacuum spherical shell flange assembly as described in any one of claims 1 to 9.

[0014] The computer program product of the present invention, when executed by a processor, can implement the steps of the method according to any one of claims 1 to 8, and the computer program includes the following functional modules: Posture optimization module: This module is used to build a flange assembly posture model based on the flange mounting hole manufacturing error and assembly accuracy requirements, and calls the improved non-dominated sorting algorithm to search for the optimal solution and output the optimal assembly posture parameter set; Coordinate conversion and calibration module: used to establish the flange coordinate system and calibrate the position of the auxiliary positioning point in the flange coordinate system by fitting the point cloud data of the flange end face and outer surface in the laser tracker coordinate system; Actual pose solution module: used to receive the coordinates of the auxiliary positioning points measured by the laser tracker, transform them with the flange coordinate system data and perform point cloud registration to obtain the actual pose of the flange in the spherical center coordinate system; Assembly error calculation module: used to construct theoretical flange posture, compare it with the actual posture, calculate various key error indicators, and determine whether the assembly tolerance requirements are met; Welding adjustment control module: used to output spot welding sequence, spot welding position and welding shrinkage reserve gap according to the posture deviation of auxiliary positioning points when the assembly error exceeds the limit, and generate spot welding path suggestions; Posture backtest and iteration module: used to re-collect the coordinates of the auxiliary positioning points after each round of spot welding and determine whether the posture error tolerance is met. If not, it outputs the adjustment instruction again and returns to the posture measurement link to achieve automatic iterative closed loop.

[0015] The beneficial effects of the present invention are: 1. The present invention proposes to solve the problem that the flange is difficult to adjust to its theoretical design position due to manufacturing errors in the flange mounting holes by solving the optimal achievable position of the flange based on the improved non-dominated sorting algorithm; 2. The present invention proposes a method for calibrating the flange coordinate system and the coordinate information of the auxiliary positioning points to solve the problem of the difficulty in quickly determining the actual position and posture of the flange during assembly and to quickly guide assembly. The method also constructs a coordinate information model of the auxiliary positioning points in the flange coordinate system. 3. The present invention proposes an assembly process scheme for roughly positioning the flange using a positioning block, which can solve the problem of difficulty in positioning the flange during the initial assembly process. The position of the rough positioning block is determined and welded to fix it. The flange is lifted by a trolley, and the flange is inserted into the flange mounting hole by adjusting the posture using a hand hoist. The flange is roughly positioned by relying on the positioning block. 4. The present invention proposes an assembly process solution for fine-tuning the flange position by spot welding the flange root according to the flange assembly error and the deviation of the auxiliary positioning point. This can solve the problem of difficulty in adjusting the flange using the adjustment mechanism due to limited assembly space during the initial assembly of the flange. 5. The measurement and adjustment method and system for large vacuum spherical shell flange assembly proposed in the present invention can effectively improve the efficiency and accuracy of flange assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the center position deviation of the flange end face according to the present invention; Figure 2 Schematic diagram of the vertical distance deviation and centering deviation from the spherical center to the flange end face according to the present invention; Figure 3 is a flow chart of the improved non-dominated sorting algorithm of the present invention; Figure 4 It is a flow chart of the calibration of the flange coordinate system of the present invention; Figure 5 It is a schematic diagram of the posture transformation of the auxiliary positioning point from LTCS to FCS; Figure 6 This is a schematic diagram of the position calculation of the positioning block of the present invention; Figure 7 This is a flow chart about flange measurement and adjustment according to the present invention; Figure 8 It is an overall flow chart of the present invention. DETAILED DESCRIPTION

[0017] Example 1: Based on the manufacturing error of the flange mounting hole and the assembly accuracy requirements of the flange, an improved non-dominated sorting algorithm is used to evaluate the optimal achievable position of the flange, and an optimal achievable flange target position is obtained to guide assembly. During the assembly process, the flange needs to meet the assembly accuracy requirements of both position and direction. The position error includes the error in the center position of the flange end face and the error in the vertical distance between the center of the spherical shell and the flange end face; the direction error is the error in the vertical distance between the center of the sphere and the normal to the center of the flange end face. The above assembly accuracy requirements for the flange are collectively referred to as positioning accuracy constraints, and the specific modeling process is as follows.

[0018] The error of the center position of the flange end face is described in the theoretical flange coordinate system. The deviation between the actual position of the flange end face center and the theoretical position is as follows: Figure 1 As shown, the actual deviation of this point shall not be greater than ε1, so the error of the center position of the flange end face is: , Where, x 0 、y 0 is the actual position of the center of the flange end face, x 0N 、y 0N The theoretical position of the flange end face center, the deviation between them shall not exceed the accuracy requirement Δ x max 、 Δ y max ; The vertical distance from the center of the sphere to the flange end face is as follows Figure 2 As shown, the error of this distance shall not be greater than ε2, and the error expression formula is: , Where D is the actual distance between the flange centers, D N is the theoretical distance from the flange center; The actual flange orientation error causes the flange end face center normal to fail to pass through the sphere center, such as Figure 3 As shown in the figure, the distance between the center of the sphere and the center normal of the flange end face is called the centration deviation, and its calculation formula and error expression are: , Where, O is the position of the sphere center, P is the position of the flange end center, L Actual is the direction vector of the center line of the flange end face; In addition to the positioning accuracy constraint, the adjustment of the flange posture is also affected by the manufacturing error of the flange mounting hole. The resulting constraint is called the machining accuracy constraint. The modeling process is as follows: The error of the center position of the flange mounting hole is , , In summary, the optimization goal of the flange assembly optimal posture evaluation problem can be expressed as: ; According to the objective function established above and the engineering constraints set, the non-dominated sorting genetic algorithm is used to optimize the above multi-objective problem. However, the traditional genetic algorithm is prone to local convergence and poor distribution uniformity of spatial solutions. In order to improve the optimization performance of the final assembly parameters in high-dimensional nonlinear space, the classic non-dominated sorting genetic algorithm is improved by improving the initialization strategy, introducing simulated binary crossover, and adaptive Gaussian mutation mechanism to enhance the globality and convergence of the algorithm search. The flowchart of the improved algorithm is shown below. Figure 3 As shown; The specific process of the improved algorithm is as follows: Step 1: In the search space of the design variables, divide the range of each variable into m equally spaced intervals, and randomly select a point in each interval as a sampling point; then sample each variable, construct an individual, and use these individuals to form the initial population. P 0; Step 2: Calculate the fitness value of each generated individual target. After calculating the fitness value, perform non-dominated sorting and crowding calculation on the individuals in the initial population. Step 3: Use the tournament to select parent individuals from the current population. Each time, two groups of individuals are randomly selected for comparison. Individuals with lower non-dominated ranks or higher crowding degrees are selected as parents until N pairs of parent individuals are selected. Step 4: For each pair of parent individuals and Perform a simulated binary crossover operation to generate two offspring individuals and , the expected position of the offspring does not deviate from the mean of the parent generation, and the generation formula of the offspring is: , Where, i is the index of the function parameter, β is the cross coefficient, and its calculation formula is: , Where, u is a random number uniformly distributed between 0 and 1, η c is a control parameter that controls the distribution strength of the crossover operation, which determines the degree of deviation of the offspring gene value from the parent gene value; At the same time η c When it tends to infinity, the offspring genes are concentrated near the parent generation, achieving local fine search, and when η c When it is smaller, the generated βA more dispersed distribution helps the algorithm escape local optima. This controllable distribution range ensures that the algorithm has strong exploration capabilities in the early stages of iteration, while gradually focusing on the neighborhood of the Pareto frontier in the later stages, thus balancing diversity and convergence speed. Step 5: For each variable in each individual, p m The mutation probability is used to determine whether to mutate; then based on the number of iterations t To set the standard deviation of the variation σ Dynamic adjustment, the standard deviation of the t-th generation variation σ t for: , Since the standard deviation of each generation σ t The following equation satisfies the sufficient convergence condition in the randomized approximation algorithm, ensuring both a large-scale search in the early stages and a gradual refinement of the solution accuracy in the later stages. This mathematically supports the algorithm's global search and local convergence capabilities. , If a variable of the offspring individual x i If variation is required, then from the normal distribution Generate a random value Δx in , and add it to the original variable value to form a variant value; , If the mutated value exceeds the value range of the variable, the following corrections are made to it; ; Step 6: First, merge the parent population and the child population to generate a temporary population of size 2N P' ; Calculate the fitness of the population, and then according to the Pareto dominance relationship, divide the population P' is divided into multiple non-dominated layers, where F 1 contains the current best non-dominated individual, F 2 contains the suboptimal non-dominated individuals, and so on; finally, for each individual in the non-dominated layer, its crowding distance D i for: , Where, f mi+1 and f mi-1 is the target value of the adjacent individuals on the target m, f mmax and f mmin is the maximum and minimum value of the target m; Step 7: Select the population according to the principle of lower priority for non-dominated level and larger priority for crowded distance.P' Select the next generation population of size N P next , then return to step 3 and iterate the optimization until the termination condition is reached.

[0019] After solving the optimal target pose of the flange, the flange coordinate system is calibrated. The calibration process is as follows: Figure 3 shown.

[0020] The flange coordinate system is first calibrated by measuring high-precision feature information (end face and outer wall) on the flange in the laser tracker measurement coordinate system. Because the direction of measuring the flange end face features is opposite to the direction of measuring its auxiliary positioning points, the laser needs to measure the same flange at different stations. However, this process uses the same measurement network of the laser tracker, resulting in low measurement efficiency. To solve this problem, an L-shaped auxiliary measurement tool is introduced to measure the flange end face. The flange coordinate system is constructed by extracting the flange end face features and outer surface information. This measurement process does not require moving the laser tracker and the same measurement space network, thereby improving measurement efficiency. The laser tracker uses the L-shaped auxiliary measurement tool to measure the coordinate information of the flange end face and outer surface points in the laser tracker measurement coordinate system. The flange end face and four outer surface sides are obtained by fitting the point cloud. The left and right outer surface sides and the upper and lower outer surface sides are divided into two equal parts to obtain two relatively perpendicular left and right center planes and upper and lower center planes. The intersection of the two center planes and the end plane is used as the origin of the flange coordinate system, the normal direction of the flange end plane is used as the Z axis of the flange coordinate system, and the normal direction of the left and right center planes is used as the Y axis of the flange coordinate system. The flange coordinate system is established to obtain the position relationship L0 and t0 between the laser tracker measurement coordinate system and the flange coordinate system. The coordinate values ​​of the auxiliary positioning point in the laser tracker measurement coordinate system are shown in the following formula. The point group is expressed as { P 测量}, the auxiliary positioning point is in the flange coordinate system { P 法兰}The coordinate value expression is: , After calibrating the flange coordinate system and determining the coordinate information of the auxiliary positioning points in the flange coordinate system, determine and weld the positioning blocks and preliminarily install the flange.

[0021] The position of the positioning block relative to the flange end face is determined based on the measured value L of the distance between the intersection of the four side ridges of the flange mounting hole and the inner wall of the spherical shell and the center of the sphere. The position calculation diagram of the positioning block is as follows: Figure 5 As shown, its projection on the flange centerline is M. According to the assembly process requirements, the distance between the flange end face and the sphere center is D. The calculation expression for the distance H between the positioning block and the flange end face is: H = D - M, After determining the position of the rough positioning block, weld it to fix it, use the crane to lift the flange, adjust the posture by the hand chain hoist, insert the flange into the flange mounting hole, and use the positioning block to perform rough positioning of the flange; After the initial flange assembly, use a laser tracker to measure the coordinate information of the auxiliary positioning point in the spherical center coordinate system. ,based on and The two point clouds are aligned using a point cloud registration algorithm to determine the actual pose of the flange coordinate system within the spherical center coordinate system. In three-dimensional space, the flange's pose is determined by its translation and rotation parameters. These parameters can be further divided into translation and rotation. Translation represents the displacement of the flange center along the x, y, and z axes, while rotation represents the flange's rotation angle relative to the x, y, and z axes, typically expressed as Euler angles. Therefore, the overall pose parameters of the flange in space can be defined as a six-dimensional vector, as shown in the following formula. These pose parameters describe the flange's complete position and orientation in three-dimensional space.

[0022] , , According to pose fitting theory, only three non-collinear measurement points are required to determine the position and pose of a rigid body in space. The greater the number of measurement points, the more accurate the position and pose of the rigid body in space. Therefore, the auxiliary positioning points on the auxiliary measurement plate on the flange can be used to evaluate the flange's position and pose.

[0023] Before solving the initial position of the flange by the auxiliary positioning points actually measured, it is necessary to first eliminate the translation effect of the point set so that the position of each point is described relative to its center of mass. The point group can be calculated by the formula The centroid of the point group is then subtracted from the centroid of each point in the point group. The coordinate values ​​of the point group can be obtained The position relative to the center of mass is given by the formula: , , The n characteristic points of the flange are in two point groups and The covariance matrix H between can be obtained by the formula: , The covariance matrix H is decomposed into three parts by singular value decomposition (SVD), where U and V are orthogonal matrices. is a diagonal matrix containing the singular values ​​of the matrix.

[0024] , At this time, the rotation matrix R is calculated by the decomposition matrix of the covariance matrix H. As shown in the formula, if det(R) = −1, the last column of the matrix V needs to be inverted.

[0025] , The calculation of the translation vector is shown in the formula: , Finally, the pose transformation matrix of the actual flange coordinate system in the spherical center coordinate system is obtained as follows: , The position of the actual flange coordinate system in the spherical center coordinate system is known, and then the theoretical flange coordinate system is established in the spherical center coordinate system according to the flange assembly process requirements. Figure 1 、 2 Calculate the various assembly errors of the flange and determine whether the assembly error meets the requirements. If so, end the installation and adjustment. If not, compare the auxiliary positioning points.

[0026] The theoretical flange coordinate system pose in the spherical center coordinate system obtains the theoretical coordinate information of the auxiliary positioning point in the spherical center coordinate system , and compare it with Compare and the coordinate difference of the corresponding points is: , Based on comparison auxiliary positioning point and Based on the comparison results, since the auxiliary positioning points have a limited adjustment range in the x and y directions, adjustments to the auxiliary positioning points are primarily made in the z direction. Spot welding is performed on the flange root based on the difference in the z direction of the auxiliary positioning points to fine-tune the flange position. After obtaining the comparison results, the operator can fine-tune the flange to minimize deviations within the design tolerance range. To initially secure the flange in this state, metal inert gas (MIG) welding (spot welding) is used. MIG welding offers advantages such as stable heat input, low spatter, and moderate penetration, making it suitable for the initial securing of fine structures on medium and thin plates and effectively reducing the risk of thermal deformation during welding.

[0027] Regarding the spot welding sequence, to minimize residual stress and avoid posture drift, the system prioritizes starting at the flange root, corresponding to the auxiliary positioning point with the largest positional deviation, and then sequentially transitioning to locations with smaller deviations. This "reverse deviation gradient" spot welding strategy achieves rigid constraints on areas with large initial deviations while mitigating stress transfer from subsequent welding areas, reducing the overall cumulative error of the system.

[0028] During spot welding, operators should allow for appropriate shrinkage based on the deviation information obtained through comparison. For example, a gap of 0.5 to 1.0 mm in the direction of the deviation should be maintained to prevent overcompensation or reverse shift of the flange posture due to shrinkage. Intermittent spot welding (each spot weld length should not exceed 20 mm) can be used to avoid heat concentration and reduce the risk of deformation.

[0029] The following points should also be noted during the welding process: 1. Before welding, the welding area should be derusted, degreased, and dried to ensure arc stability; 2. Keep the welding gun inclination angle at 15°~20° and use the direct push method; 3. Each soldering point can be welded only after it has cooled down to prevent deformation caused by heat accumulation; After spot welding is completed, the laser tracker should be measured again to confirm that the actual position of the flange meets the design requirements. If there is a slight deviation, local repair welding can be performed or the weld spot can be removed and readjusted to ensure that the closed loop of posture adjustment and precision control is closed during the entire assembly process.

[0030] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement of the above embodiments made according to the technical essence of the present invention, within the spirit and principles of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A measurement and adjustment method for large spherical shell flange assembly, characterized in that: The specific steps include: Step 1: Based on the manufacturing error of the flange mounting hole, the improved non-dominated sorting algorithm is used to evaluate the optimal reachable pose of the flange; Step 2: calibrate the flange coordinate system to obtain the coordinate information of the auxiliary positioning point in the flange coordinate system; Step 3: Locate and weld the flange positioning block based on the measured value of the distance between the corner point of the flange mounting hole and the center of the sphere, insert the flange into the hole, and roughly position the flange with the help of the positioning block; Step 4: Use a laser tracker to measure the coordinate information of the auxiliary positioning point in the spherical center coordinate system, and solve the actual flange coordinate system posture in the spherical center coordinate system based on the coordinate information of the auxiliary positioning point in the flange coordinate system in step 1; Step 5: Establish a theoretical flange coordinate system in the spherical center coordinate system according to the flange assembly process requirements, compare the deviation between the actual flange coordinate system and the theoretical flange coordinate system, calculate the various flange assembly errors, and determine whether the assembly errors meet the requirements. If so, end the assembly and adjustment; if not, proceed to step 6. Step 6. Obtain the theoretical coordinate information of the auxiliary positioning point in the spherical center coordinate system based on the coordinate information of the auxiliary positioning point in the flange coordinate system in step 2 and the position of the theoretical flange coordinate system in the spherical center coordinate system in step 5; spot weld the flange root based on the comparison of the theoretical coordinate and actual coordinate information of the auxiliary positioning point to fine-tune the flange position, and then return to step 4.

2. A measurement and adjustment method for large spherical shell flange assembly according to claim 1, characterized in that: In step 1, a flange posture evaluation model is constructed based on the manufacturing error of the flange mounting hole and the flange assembly accuracy requirements. The improved non-dominated sorting algorithm is used to solve the optimal achievable posture parameters of the flange. The specific steps include: Step 101: In the search space of the design variables, divide the range of each variable into m equally spaced intervals, and randomly select a point in each interval as a sampling point; then sample each variable, construct an individual, and use these individuals to form the initial population. P 0; Step 102: Calculate the fitness value of each generated individual target. After calculating the fitness value, perform non-dominated sorting and crowding calculation on the individuals in the initial population. Step 103: Use a tournament to select parent individuals from the current population. Each time, two groups of individuals are randomly selected for comparison. Individuals with lower non-dominated ranks or higher crowding degrees are selected as parents until N pairs of parent individuals are selected. Step 104: For each pair of parent individuals and Perform a simulated binary crossover operation to generate two offspring individuals and , the expected position of the offspring does not deviate from the mean of the parent generation, and the generation formula of the offspring is: ， Where, i Represents the index of the function parameter, β It represents the cross coefficient, and its calculation formula is: ， Where, u represents a random number uniformly distributed between 0 and 1. η c Indicates control parameters; when η c When it tends to infinity, the offspring genes are concentrated near the parent generation, achieving local fine search, and when η c When it is smaller, the generated β A more dispersed distribution helps the global system escape from local optimality; Step 105: For each variable in each individual, p m The mutation probability is used to determine whether to mutate; then based on the number of iterations t To set the standard deviation of the variation σ Dynamic adjustment, the standard deviation of the t-th generation variation σ t for: ， ， represents the initial standard deviation, represents the maximum number of iterations, Indicates the current iteration number; If a variable of the offspring individual x i If variation is required, then from the normal distribution Generate a random value Δx in , and add it to the original variable value to form a variant value; ， in, Indicates the value of the gene after the mutation operation, Indicates the number of an individual in the current population i’ The original value of each gene; If the mutated value exceeds the variable's range, the following corrections are made to it: ， in, represents the upper bound of the variable, Indicates the lower bound of the variable; Step 106: First, merge the parent population and the child population to generate a temporary population of size 2N. P' ; Calculate the fitness of the population, and then according to the Pareto dominance relationship, divide the population P' is divided into multiple non-dominated layers, where F 1 contains the current best non-dominated individual, F 2 contains the suboptimal non-dominated individuals, and so on; finally, for each individual in the non-dominated layer, its crowding distance D i for: ， Where, f mi+1 and f mi-1 represents the target value of the adjacent individuals on the target m, f mmax represents the maximum value of the target m, f mmin represents the minimum value of the target m; Step 107: select the population according to the principle of lower non-dominated level first and larger crowding distance second priority. P' Select the next generation population of size N P next , then returns to step 103 and iterates the optimization until the termination condition is reached.

3. A measurement and adjustment method for large spherical shell flange assembly according to claim 2, characterized in that: The various assembly accuracies of the flange are the error of the center position of the flange end face, the error of the vertical distance from the sphere center to the flange end face, and the centering deviation. Their mathematical models are: ， Where, Indicates the error of the center position of the flange end face, Indicates the actual position horizontal coordinate of the flange end face center, Indicates the horizontal coordinate of the theoretical position of the center of the flange end face, Indicates the actual position ordinate of the flange end face center, Indicates the theoretical vertical coordinate of the flange end face center. Indicates the assembly accuracy requirements of the flange end face center position, Indicates the error of the flange end face center position in the x direction, Indicates the assembly accuracy requirement of the flange end face center position in the x direction, Indicates the error of the flange end face center position in the y direction, Indicates the assembly accuracy requirement of the flange end face center position in the x direction; ， Where, Indicates the error in the vertical distance from the center of the sphere to the flange end face. Indicates the actual distance to the flange center, Indicates the theoretical distance of the flange center, Indicates the assembly accuracy requirement of the vertical distance from the center of the sphere to the flange end face; ； Where, Indicates deviation from the center. Represents the direction vector of the flange end face centerline, represents the position of the center of the sphere, Indicates the position of the center of the flange end face; Indicates deviation from the center. Indicates the assembly accuracy requirements for the center; The error of the center position of the flange mounting hole is: ， ， Where, Indicates the actual position of the mounting hole in the x direction, Indicates the theoretical position of the mounting hole in the x direction, Indicates the assembly accuracy requirement of the center position of the mounting hole in the x direction, Indicates the actual position of the mounting hole in the y direction, Indicates the theoretical position of the mounting hole in the y direction, Indicates the assembly accuracy requirement of the center position of the mounting hole in the y direction; Therefore, the evaluation model of the flange posture is: 。 4. The measurement and adjustment method for large spherical shell flange assembly according to claim 1, characterized in that: In step 2, the flange coordinate system is calibrated by measuring the coordinate information of the flange end face and outer side points in the laser tracker measurement coordinate system. The end face and four outer side faces of the flange are obtained by fitting the point cloud. The left and right outer side faces and the upper and lower outer side faces are divided into two equal parts to obtain two relatively vertical left and right center planes and upper and lower center planes. The intersection of the two center planes and the end face is used as the origin of the flange coordinate system, the normal direction of the flange end face is used as the Z axis of the flange coordinate system, and the normal direction of the left and right center planes is used as the Y axis of the flange coordinate system. The flange coordinate system is established. The position expression of the flange coordinate system in the laser tracker measurement coordinate system is: ， ； In step 2, the coordinate information of the auxiliary positioning point in the flange coordinate system is obtained. It is known that the position of the flange coordinate system in the laser tracker measurement coordinate system is L and t. The auxiliary positioning point { P 测量 }, the auxiliary positioning point is in the flange coordinate system { P 法兰 }The coordinate value expression is: 。 5. The measurement and adjustment method for large spherical shell flange assembly according to claim 1, characterized in that: The position of the positioning block relative to the flange end face in step 3 is determined based on the measured value of the distance between the intersection of the four side ridges of the flange mounting hole and the inner wall of the spherical shell and the center of the sphere. Its projection on the flange centerline is M. According to the assembly process requirements, the distance between the flange end face and the center of the sphere is known to be D. The calculation expression for the distance H of the positioning block relative to the flange end face is: H = D - M, After determining the position of the coarse positioning block, weld it to fix it, use the crane to lift the flange, adjust the posture by the hand hoist, insert the flange into the flange mounting hole, and use the positioning block to perform coarse positioning on the flange.

6. The measurement and adjustment method for large spherical shell flange assembly according to claim 1, characterized in that: In step 4, a laser tracker is used to measure the coordinate information of the auxiliary positioning point in the spherical center coordinate system. ,based on and The two point clouds are solved through the point cloud registration algorithm to obtain the actual position of the flange coordinate system in the spherical center coordinate system.

7. The measurement and adjustment method for large spherical shell flange assembly according to claim 1, characterized in that: In step 5, a theoretical flange coordinate system is established in the spherical center coordinate system according to the flange assembly process requirements, and the deviation between the actual flange coordinate system and the theoretical flange coordinate system is compared to calculate the various assembly errors of the flange to determine whether the assembly error meets the requirements. If so, the assembly adjustment is terminated; if not, proceed to step 6.

8. The measurement and adjustment method for large spherical shell flange assembly according to claim 1, characterized in that: In step 6, based on The theoretical coordinate information of the auxiliary positioning point in the spherical center coordinate system is obtained from the theoretical flange coordinate system posture in the spherical center coordinate system in step 5. ; Based on comparison auxiliary positioning point and The comparison results are used to adjust the flange root by metal inert gas shielded welding. The spot welding operation is performed by metal inert gas shielded welding. The spot welding sequence starts from the flange root corresponding to the auxiliary positioning point with the largest position deviation, and transitions to the corresponding flange root with smaller deviation. During the spot welding process, welding shrinkage allowance is reserved according to the measurement results to ensure that the flange posture still meets the design requirements after the final welding is completed. In this way, the flange posture is finely adjusted, and then return to step 4.

9. A measuring and adjusting system for assembling large spherical shell flanges for implementing the method of claim 1, 2, 3, 4, 5, 6, 7 or 8, characterized in that: It includes a storage device, a processor, a laser tracker measuring device, a posture calculation module, an assembly evaluation module and a welding auxiliary module; the processor executes a computer program stored in the storage device to implement the steps of the measurement and adjustment method for assembling a large vacuum spherical shell flange as described in any one of claims 1 to 9.

10. A computer program product, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 can be implemented. The computer program includes the following functional modules: Posture optimization module: This module is used to build a flange assembly posture model based on the flange mounting hole manufacturing error and assembly accuracy requirements, and calls the improved non-dominated sorting algorithm to search for the optimal solution and output the optimal assembly posture parameter set; Coordinate conversion and calibration module: used to establish the flange coordinate system and calibrate the position of the auxiliary positioning point in the flange coordinate system by fitting the point cloud data of the flange end face and outer surface in the laser tracker coordinate system; Actual pose solution module: used to receive the coordinates of the auxiliary positioning points measured by the laser tracker, transform them with the flange coordinate system data and perform point cloud registration to obtain the actual pose of the flange in the spherical center coordinate system; Assembly error calculation module: used to construct theoretical flange posture, compare it with the actual posture, calculate various key error indicators, and determine whether the assembly tolerance requirements are met; Welding adjustment control module: used to output spot welding sequence, spot welding position and welding shrinkage reserve gap according to the posture deviation of auxiliary positioning points when the assembly error exceeds the limit, and generate spot welding path suggestions; Posture backtest and iteration module: used to re-collect the coordinates of the auxiliary positioning points after each round of spot welding and determine whether the posture error tolerance is met. If not, it outputs the adjustment instruction again and returns to the posture measurement link to achieve automatic iterative closed loop.

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