A method and system for measuring and adjusting large spherical shell flange assembly

Abstract

The application relates to a kind of measurement and adjustment method and system for large spherical shell flange assembly, and relates to a kind of measurement and adjustment method and system for spherical shell flange assembly.The present application is to solve the problems that flange cannot be aligned to theoretical pose caused by flange hole manufacturing error in traditional assembly technology, it is difficult to quickly evaluate the pose of flange in the process of assembly, flange positioning is difficult, assembly space is limited, leading to the difficulty of adjusting flange through mechanism.The steps of the method include evaluating the optimal reachable pose of flange based on the manufacturing error of flange mounting hole using improved non-dominated sorting algorithm;calibrating flange coordinate system;positioning based on the measured value of the distance between the corner point of flange mounting hole and the center of the sphere;establishing theoretical flange coordinate system in the center coordinate system of the sphere according to the assembly process requirements of flange;obtaining the theoretical coordinate information of auxiliary positioning point in the center coordinate system of the sphere.The application belongs to the field of high-precision assembly and measurement technology of flange parts.

Description

Technical Field

[0001] This invention relates to a measurement and adjustment method and system for assembling ball flanges, belonging to the field of high-precision assembly and measurement technology for flange parts. Background Technology

[0002] In large spherical pressure vessels, flanges serve as crucial connecting components between the spherical shell and piping. Their high-precision assembly is critical to ensuring the normal operation of the pressure vessel. Due to the curvature and complex geometry of the spherical shell, achieving precise flange positioning and installation on its surface presents a significant technical challenge. Traditional assembly techniques suffer from a series of problems, including manufacturing errors in the flange bores causing misalignment, difficulty in quickly assessing the flange's position during assembly, difficulties in flange positioning, and limitations in assembly space hindering adjustments via mechanisms.

[0003] Patent application CN116929252A, filed on July 18, 2023, discloses an assembly measurement method, device, system, equipment, and storage medium for flange structures, relating to the fields of assembly and measurement technology. The method involves: acquiring at least one set of first end-face images of the flange structure before assembly and a second end-face image set after bolt assembly, captured by a binocular camera; acquiring first point cloud data corresponding to the first end-face image set and second point cloud data corresponding to the second end-face image set; determining the coaxiality error of the flange structure and the surface shape error corresponding to each bolt area on the flange structure based on the first and second point cloud data; and adjusting the assembly of the flange structure based on the coaxiality error and surface shape error. This application processes the end-face image sets before and after flange assembly and quantifies the deformation or assembly effect of the flange structure using coaxiality error and surface shape error, which can optimize the sealing performance of the flange structure and reduce the number of adjustments. This method and system are not applicable to the assembly technology of large vacuum spherical flanges, and they cannot solve a series of problems such as aligning to the theoretical pose, difficulty in quickly assessing the flange pose during assembly, difficulty in flange positioning, and difficulty in adjusting the flange by means of a mechanism due to limited assembly space.

[0004] To address the above problems, this invention proposes an assembly method for the flange assembly process, thereby efficiently completing the high-precision assembly task of flanges. Summary of the Invention

[0005] This invention addresses the problems in traditional assembly techniques, such as flange hole manufacturing errors causing flanges to fail to align to their theoretical positions, difficulty in quickly assessing flange positions during assembly, flange positioning difficulties, and limited assembly space making it difficult to adjust flanges using mechanisms. Therefore, this invention proposes a measurement and adjustment method and system for assembling large spherical flanges.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: The steps of the measurement and adjustment method for assembling large spherical flanges according to the present invention include:

[0007] Step 1: Based on the manufacturing error of the flange mounting holes, an improved non-dominated sorting algorithm is used to evaluate the optimal reachable pose of the flange.

[0008] Step 2: Calibrate the flange coordinate system to obtain the coordinate information of the auxiliary positioning point in the flange coordinate system;

[0009] Step 3: Based on the measured distance between the corner point of the flange mounting hole and the center of the ball, locate and weld the flange positioning block, insert the flange into the hole, and use the positioning block to roughly position the flange.

[0010] Step 4: Use a laser tracker to measure the coordinate information of the auxiliary positioning point in the sphere-centered coordinate system. Based on the coordinate information of the auxiliary positioning point in the flange coordinate system in Step 1, solve for the pose of the actual flange coordinate system in the sphere-centered coordinate system.

[0011] Step 5: Establish a theoretical flange coordinate system in the sphere 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 assembly errors of the flange, and determine whether the assembly errors meet the requirements. If they do, the assembly and adjustment will end. If they do not meet the requirements, proceed to step 6.

[0012] Step 6: Based on the coordinate information of the auxiliary positioning point in the flange coordinate system in Step 2 and the pose of the theoretical flange coordinate system in the sphere center coordinate system in Step 5, obtain the theoretical coordinate information of the auxiliary positioning point in the sphere center coordinate system; perform spot welding on the flange root to finely adjust the flange pose by comparing the theoretical coordinates and actual coordinate information of the auxiliary positioning point, and then return to Step 4.

[0013] Furthermore, in step 1, an evaluation model for the flange pose is constructed based on the manufacturing error of the flange mounting holes and the assembly accuracy requirements of the flange. An improved non-dominated sorting algorithm is used to solve for the optimal reachable pose parameters of the flange. The specific steps include:

[0014] Step 101: Within 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 to construct an individual, and collect these individuals to form the initial population. P 0;

[0015] Step 102: Calculate the fitness value of each generated individual on the target. After calculating the fitness value, perform non-dominated sorting and crowding calculation on the individuals in the initial population.

[0016] Step 103: Select parent individuals from the current population using a tournament. Each time, randomly select two groups of individuals for comparison. Select individuals with lower non-dominance level or higher crowding as parents until N pairs of parent individuals are selected.

[0017] 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 average of the parents. The formula for generating offspring is:

[0018] ,

[0019] In the formula, i Indicates the index of the function parameter. β The cross coefficient is represented by the following formula:

[0020] ,

[0021] In the formula, u This represents a random number that is uniformly distributed between 0 and 1. η c Indicates control parameters;

[0022] when η c As the number approaches infinity, offspring genes concentrate near the parents, achieving a fine-grained local search. However, when... η c When smaller, the generated β A more dispersed distribution helps the global system escape local optima;

[0023] Step 105: For each variable in each individual, use... p m The mutation probability is used to determine whether to perform mutation; then, based on the number of iterations... t To set the standard deviation of the variation σ Dynamically adjust the standard deviation of the variation in generation t. σ t for:

[0024] ,

[0025] ,

[0026] Indicates the initial standard deviation. Indicates the maximum number of iterations. Indicates the current iteration number;

[0027] If a certain variable of the offspring individuals xi If variation is needed, then follow the normal distribution. A random value Δx is generated and added to the original variable value to form a variant value;

[0028] ,

[0029] in, This indicates the value of the gene after the mutation operation. This represents the first individual in the current population. i’ The original values ​​of each gene;

[0030] If the mutated value exceeds the range of the variable, then it is corrected as follows:

[0031] ,

[0032] in, Indicates the upper boundary of the variable. Indicates the lower boundary of the variable;

[0033] Step 106: First, merge the parent population and the offspring population to generate a temporary population of size 2N. P' Calculate the fitness of the population, and then, according to Pareto dominance, divide the population... P' Divided into multiple non-dominated layers, among which F 1 includes the currently best non-dominated individual. F 2 includes suboptimal non-dominated individuals, and so on; finally, for each individual in the non-dominated layer, their crowding distance is... D i for:

[0034] ,

[0035] In the formula, This represents the number of objective functions in an optimization problem. f mi+1 and f mi-1 This represents the target value of the adjacent individuals on target m. f mmax This represents the maximum value of the target m. f mmin This represents the minimum value of the objective m;

[0036] Step 107: Prioritize populations with lower non-dominant rank and those with greater crowding distance. P' Select the next generation population of size N. P next Then return to step 103 and continue iteratively optimizing until the termination condition is met.

[0037] Furthermore, the assembly precision requirements for the flange are: error in the center position of the flange end face, error in the perpendicular distance from the center of the ball to the flange end face, and misalignment. Their mathematical models are as follows:

[0038] ,

[0039] In the formula, This indicates the error in the center position of the flange end face. The x-coordinate represents the actual position of the center of the flange end face. The x-coordinate represents the theoretical position of the flange end face center. The vertical coordinate represents the actual position of the center of the flange end face. This represents the ordinate of the theoretical position of the flange end face center. This indicates the assembly precision requirements for the center position of the flange end face. This indicates the error in the x-direction of the flange end face center position. This indicates the assembly accuracy requirement for the center position of the flange end face in the x-direction. This indicates the error in the y-direction of the flange end face center position. This indicates the assembly accuracy requirement for the center position of the flange end face in the x direction;

[0040] ,

[0041] In the formula, This indicates the error in the perpendicular distance from the center of the ball to the flange end face. Indicates the actual distance between the flange centers. This represents the theoretical distance between the flange centers. This indicates the required assembly precision for the vertical distance from the center of the ball to the flange end face.

[0042] ;

[0043] In the formula, Indicates a deviation from the center of gravity. This represents the direction vector of the centerline of the flange end face. Indicates the position of the center of the ball. Indicates the position of the center of the flange end face; Indicates a deviation from the center of gravity. This indicates the required assembly precision for the core.

[0044] The error in the center position of the flange mounting hole is:

[0045] ,

[0046] ,

[0047] In the formula, This indicates the actual position of the mounting hole in the x-direction. This indicates the theoretical position of the mounting hole in the x-direction. This indicates the required assembly accuracy of the mounting hole center position in the x-direction. This indicates the actual position of the mounting hole in the y-direction. This indicates the theoretical position of the mounting hole in the y-direction. This indicates the required assembly accuracy of the mounting hole center position in the y-direction;

[0048] Therefore, the evaluation model for the flange pose is as follows:

[0049] .

[0050] Furthermore, in step 2, the flange coordinate system is calibrated by measuring 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 surfaces are obtained by fitting the point cloud. The left and right outer surfaces and the upper and lower outer surfaces are bisected to obtain two relatively perpendicular left and right center planes and upper and lower center planes. The intersection point of the two center planes and the end face is taken as the origin of the flange coordinate system. The normal direction of the flange end face is taken as the Z-axis of the flange coordinate system, and the normal directions of the left and right center planes are taken as the Y-axis of the flange coordinate system. The pose expression of the flange coordinate system in the laser tracker measurement coordinate system is:

[0051] ,

[0052] ;

[0053] Step 2 obtains the coordinate information of the auxiliary positioning point in the flange coordinate system. Given the pose of the flange coordinate system in the laser tracker measurement coordinate system as L and t, the auxiliary positioning point { is measured in the laser tracker measurement coordinate system. P 测量}, the auxiliary positioning point is in the flange coordinate system { P 法兰 The coordinate value expression is:

[0054] .

[0055] Furthermore, in step 3, determining the position of the positioning block relative to the flange end face is based on the measured distance between the intersection of the four side ribs 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 expression for calculating the distance H of the positioning block relative to the flange end face is:

[0056] H = D -M,

[0057] After determining the position of the coarse positioning block, weld it in place. Use an overhead crane to lift the flange, and use a hand-operated hoist to adjust its position so that the flange is inserted into the flange mounting hole. The positioning block is used to coarsely position the flange.

[0058] Furthermore, in step 4, a laser tracker is used to measure the coordinate information of the auxiliary positioning point in the spherical coordinate system. ,based on and The actual pose of the flange coordinate system in the sphere-centered coordinate system is obtained from the two point clouds using a point cloud registration algorithm.

[0059] Furthermore, in step 5, a theoretical flange coordinate system is established in the spherical coordinate system according to the flange assembly process requirements. The deviation between the actual flange coordinate system and the theoretical flange coordinate system is compared, and various assembly errors of the flange are calculated. It is then determined whether the assembly errors meet the requirements. If they do, the assembly and adjustment process ends; otherwise, step 6 is performed.

[0060] Furthermore, in step 6 based on In step 5, the theoretical coordinate information of the auxiliary positioning point in the sphere-centered coordinate system is obtained from the pose of the theoretical flange in the sphere-centered coordinate system. Based on comparison of auxiliary positioning points and The comparison results were used to adjust the flange root by spot welding with metal inert gas shielded welding. The spot welding operation was carried out by metal inert gas shielded welding. The spot welding sequence started from the flange root corresponding to the auxiliary positioning point with the largest position deviation and transitioned to the flange root corresponding to the smaller deviation. During the spot welding process, the welding shrinkage allowance was reserved according to the measurement results to ensure that the flange position still meets the design requirements after the final welding is completed. This was used to finely adjust the flange position and then return to step 4.

[0061] The present invention provides a measurement and adjustment system for assembling large spherical flanges, comprising a storage device, a processor, a laser tracker measuring device, an attitude 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 large vacuum spherical flanges as described in any one of claims 1 to 9.

[0062] The present invention provides a computer program product, which, when executed by a processor, is capable of implementing the steps of the method as described in any one of claims 1 to 8. The computer program includes the following functional modules:

[0063] Pose optimization module: used to build a flange assembly pose model based on the manufacturing error and assembly accuracy requirements of the flange mounting hole, and call the improved non-dominated sorting algorithm to search for the optimal solution and output the optimal assembly pose parameter set.

[0064] Coordinate transformation 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;

[0065] Actual pose calculation module: It is used to receive the coordinates of the auxiliary positioning points measured by the laser tracker, and transform and register them with the flange coordinate system data to obtain the actual pose of the flange in the sphere center coordinate system.

[0066] Assembly error calculation module: used to construct the theoretical flange pose, compare it with the actual pose, calculate various key error indicators, and determine whether the assembly tolerance requirements are met;

[0067] Welding adjustment control module: When assembly errors exceed the limits, it outputs the spot welding sequence, spot welding position and welding shrinkage allowance gap based on the positional deviation of the auxiliary positioning point, and generates spot welding path suggestions.

[0068] Attitude backtesting and iteration module: It is used to reacquire 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 command again and returns to the posture measurement stage to realize automatic iterative closed loop.

[0069] The beneficial effects of this invention are:

[0070] 1. This invention proposes an improved non-dominated sorting algorithm to solve the problem of flanges being difficult to adjust to their theoretically designed pose due to manufacturing errors in the flange mounting holes.

[0071] 2. This invention proposes a calibration method for the flange coordinate system and auxiliary positioning point coordinate information, which can solve the problem of the difficulty in quickly solving the actual position and orientation of the flange during the assembly process and rapidly guiding the assembly, and constructs a coordinate information model of the auxiliary positioning point in the flange coordinate system.

[0072] 3. The present invention proposes an assembly process scheme for using positioning blocks to coarsely position flanges, which can solve the problem of difficulty in positioning flanges during the initial assembly process. The position of the coarse positioning blocks is determined and welded and fixed. The flange is lifted by an overhead crane and the flange is inserted into the flange mounting hole by adjusting the posture with a hand-operated hoist. The flange is coarsely positioned by relying on the positioning blocks.

[0073] 4. The present invention proposes an assembly process scheme that uses spot welding at the flange root to fine-tune the flange position based on the flange assembly error and the deviation of the auxiliary positioning point. This can solve the problem that it is difficult to use the adjustment mechanism to adjust the flange during the initial assembly process due to the limited assembly space.

[0074] 5. The measurement and adjustment method and system for assembling large vacuum spherical flanges proposed in this invention can effectively improve the efficiency and accuracy of flange assembly. Attached Figure Description

[0075] Figure 1 This is a schematic diagram of the center position deviation of the flange end face described in this invention;

[0076] Figure 2 This is a schematic diagram of the vertical distance deviation and centering deviation from the ball center to the flange end face as described in this invention;

[0077] Figure 3 This is a flowchart of the improved non-dominated sorting algorithm described in this invention;

[0078] Figure 4 This is a flowchart of the calibration process for the flange coordinate system described in this invention;

[0079] Figure 5 This is a schematic diagram of the pose transformation of the auxiliary positioning point from LTCS to FCS;

[0080] Figure 6 This is a schematic diagram illustrating the position calculation of the positioning block described in this invention;

[0081] Figure 7 This is a flowchart of flange measurement and assembly as described in this invention;

[0082] Figure 8 This is an overall flowchart of the present invention. Detailed Implementation

[0083] Example 1: Based on the manufacturing errors of the flange mounting holes and the assembly accuracy requirements of the flange, an improved non-dominated sorting algorithm is used to evaluate the optimal reachable pose of the flange, obtaining an optimal reachable target flange pose to guide assembly. During assembly, the flange needs to simultaneously meet the assembly accuracy requirements of position and orientation. Positional errors include the error in the center position of the flange end face and the error in the perpendicular distance between the center of the spherical shell and the flange end face; orientation errors are the error in the perpendicular distance between the center of the spherical shell 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 their specific modeling process is as follows.

[0084] The error in the center position of the flange end face is described in the theoretical flange coordinate system. The deviation between the actual and theoretical positions of the flange end face center is as follows: Figure 1 As shown, the actual deviation at this point must not exceed ε1, therefore the error of the center position of the flange end face is:

[0085] ,

[0086] In the formula, x 0 、y0 represents the actual position of the center of the flange end face. x 0N 、y 0N The theoretical position of the flange end face center must be within the specified tolerance; the deviation between them must not exceed the accuracy requirement Δ. x max 、 Δ y max ;

[0087] Vertical distance from the center of the ball to the flange end face, as shown Figure 2 As shown, the error of this distance must not exceed ε2, and the formula for expressing the error is:

[0088] ,

[0089] In the formula, D is the actual distance between the flange centers. N This is the theoretical distance from the flange center;

[0090] The actual directional error of the flange caused the center normal of the flange end face to fail to pass through the center of the ball, such as Figure 3 As shown, the distance between the center of the ball and the normal to the center of the flange end face is called the centering deviation, and its calculation formula and error expression are as follows:

[0091] ,

[0092] In the formula, O is the position of the ball's center, P is the position of the flange end face center, and L... Actual The direction vector of the centerline of the flange end face;

[0093] In addition to positioning accuracy constraints, the adjustment of flange pose is also affected by the manufacturing errors of flange mounting holes. The resulting constraints are called machining accuracy constraints, and their modeling process is as follows:

[0094] The error in the center position of the flange mounting hole is

[0095] ,

[0096] ,

[0097] In summary, the objective of optimizing the flange assembly optimal pose evaluation problem can be expressed as:

[0098] ;

[0099] Based on the established objective function and engineering constraints, a non-dominated sorting genetic algorithm is used to optimize the multi-objective problem. However, traditional genetic algorithms are prone to problems such as local convergence and poor uniformity of solution distribution. To improve the optimization performance of the final assembly parameters in a high-dimensional nonlinear space, the classic non-dominated sorting genetic algorithm is improved by modifying the initialization strategy, introducing simulated binary crossover, and an adaptive Gaussian mutation mechanism to enhance the globality and convergence of the search. The flowchart of the improved algorithm is as follows. Figure 3 As shown;

[0100] The specific process of improving the algorithm is as follows:

[0101] Step 1: Within 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 to construct an individual, and collect these individuals to form the initial population. P 0;

[0102] Step 2: Calculate the fitness value of each generated individual on the target. After calculating the fitness value, perform non-dominated sorting and crowding calculation on the individuals in the initial population.

[0103] Step 3: Select parent individuals from the current population using a tournament format. Each time, randomly select two groups of individuals for comparison, and select individuals with lower non-dominance levels or higher crowding levels as parents, until N pairs of parent individuals are selected.

[0104] 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 average of the parents. The formula for generating offspring is:

[0105] ,

[0106] In the formula, i For the index of the function parameter, β The cross coefficient is calculated using the following formula:

[0107] ,

[0108] In the formula, u These are random numbers uniformly distributed between 0 and 1. η c As a control parameter, it controls the distribution intensity of crossover operations, and determines the degree of deviation of the offspring gene value from the parent gene value.

[0109] At the same time ηc As the number approaches infinity, offspring genes concentrate near the parents, achieving a fine-grained local search. However, when... η c When smaller, the generated β A more dispersed distribution helps the algorithm escape local optima globally; this controllability of the distribution range ensures that the algorithm has a strong exploratory ability in the early stages of iteration, and can gradually focus on the neighborhood of the Pareto front in the later stages, thus balancing diversity and convergence speed.

[0110] Step 5: For each variable in each individual, use p m The mutation probability is used to determine whether to perform mutation; then, based on the number of iterations... t To set the standard deviation of the variation σ Dynamically adjust the standard deviation of the variation in generation t. σ t for:

[0111] ,

[0112] Due to the standard deviation of each generation σ t Satisfying the following formula satisfies the sufficient convergence condition in the random approximation algorithm, which can guarantee a large-scale search in the early stage and refine the accuracy in a gradual way in the later stage, thus mathematically supporting the algorithm's global search and local convergence capabilities.

[0113] ,

[0114] If a certain variable of the offspring individuals x i If variation is needed, then follow the normal distribution. A random value Δx is generated and added to the original variable value to form a variant value;

[0115] ,

[0116] If the mutated value exceeds the range of the variable, then the following corrections are made;

[0117] ;

[0118] Step 6: First, merge the parent population and the offspring population to generate a temporary population of size 2N. P' Calculate the fitness of the population, and then, according to Pareto dominance, divide the population... P' Divided into multiple non-dominated layers, among which F 1 includes the currently best non-dominated individual. F2 includes suboptimal non-dominated individuals, and so on; finally, for each individual in the non-dominated layer, their crowding distance is... D i for:

[0119] ,

[0120] In the formula, f mi+1 and f mi-1 Let m be the target value of the adjacent individuals. f mmax and f mmin Let m be the maximum and minimum values ​​of the target m.

[0121] Step 7: Prioritize populations with lower non-dominant rank and those with greater crowding distance. P' Select the next generation population of size N. P next Then return to step 3 and continue iteratively optimizing until the termination condition is met.

[0122] After solving for the optimal reachable target pose of the flange, the flange coordinate system is calibrated. The calibration process is as follows: Figure 3 As shown.

[0123] The calibration of the flange coordinate system begins with measuring high-precision feature information (end face and outer wall) on the flange in a laser tracker measurement coordinate system. Since 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 from different positions. However, this process uses the same measurement network for 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. By extracting the flange end face features and outer surface information, a flange coordinate system is constructed. This measurement process does not require moving the laser tracker or using the same measurement space network, thus improving measurement efficiency. Using the L-shaped auxiliary measurement tool, the coordinate information of the flange end face and outer surface points in the laser tracker measurement coordinate system is measured with the laser tracker. By fitting the point cloud, the flange end face and four outer surfaces are obtained. The left and right outer surfaces and the top and bottom outer surfaces are then bisected to obtain two relatively perpendicular left and right center planes and top and bottom center planes. Using the intersection of the two center planes and the end face as the origin of the flange coordinate system, the normal direction of the flange end face as the Z-axis, and the normal directions of the left and right center planes as the Y-axis, a flange coordinate system is established. This allows us to derive the pose relationship L0 and t0 between the laser tracker's measurement coordinate system and the flange coordinate system. The coordinate values ​​of the auxiliary positioning points in the laser tracker's measurement coordinate system are shown in the following formula. This point group is represented as { P 测量}, the auxiliary positioning point is in the flange coordinate system { P 法兰 The coordinate value expression is:

[0124] ,

[0125] After calibrating the flange coordinate system and determining the coordinate information of the auxiliary positioning points in the flange coordinate system, the positioning blocks are determined and welded, and the flange is initially installed.

[0126] The position of the locating 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 ribs 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 locating block is shown below. 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 center of the ball is D. The calculation expression for the distance H of the locating block relative to the flange end face is:

[0127] H = D - M,

[0128] After determining the position of the coarse positioning block, weld it to fix it. Use an overhead crane to lift the flange, and use a hand chain hoist to adjust the attitude and insert the flange into the flange mounting hole. Use the positioning block to coarsely position the flange.

[0129] After the initial flange assembly is completed, a laser tracker is used to measure the coordinates of the auxiliary positioning points in the spherical coordinate system. ,based on and Two point clouds are used to solve for the actual pose of the flange in the sphere-centered coordinate system using a point cloud registration algorithm. In three-dimensional space, the flange pose is determined by its translation and rotation parameters. These pose parameters can be further divided into translation and rotation parameters. Translation parameters represent the displacement of the flange center along the x, y, and z axes, while rotation parameters represent the flange's rotation relative to the x, y, and z axes, typically expressed in 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. This pose parameter describes the complete position and orientation of the flange in three-dimensional space.

[0130] ,

[0131] ,

[0132] According to pose fitting theory, theoretically, only three non-collinear measurement points are needed to determine the position and orientation of a rigid body in space. The more measurement points there are, the more accurate the representation of the rigid body's orientation in space. Therefore, the auxiliary positioning points on the auxiliary measuring plate on the flange can be used to evaluate the position and orientation of the flange.

[0133] Before solving for the initial pose of the flange using actual measured auxiliary positioning points, it is first necessary to eliminate the translational effects of the point set, ensuring that the position of each point is described relative to its centroid. The point group can then be calculated using formulas. Find the centroid of the point group, and then subtract the centroid from the coordinates of each point in the point group. The coordinates of the points can be used to obtain the point group. The position relative to the center of mass is shown in the formula:

[0134] ,

[0135] ,

[0136] For n characteristic points of the flange in two point groups and The covariance matrix H between them can be obtained from the formula:

[0137] ,

[0138] The singular value decomposition (SVD) of the covariance matrix H decomposes the matrix into three parts, where U and V are orthogonal matrices. It is a diagonal matrix that contains the singular values ​​of the matrix.

[0139] ,

[0140] At this point, the rotation matrix R is calculated by decomposing the covariance matrix H, as shown in the formula. If det(R) = −1, then the last column of matrix V needs to be inverted.

[0141] ,

[0142] The translation vector is calculated as shown in the formula:

[0143] ,

[0144] The final pose transformation matrix of the actual flange coordinate system in the sphere-centered coordinate system is:

[0145] ,

[0146] Given the actual flange coordinate system's pose in the spherical coordinate system, a theoretical flange coordinate system is established in the spherical coordinate system according to the flange's assembly process requirements. This theoretical flange coordinate system is then used as a reference... Figure 1 , 2 Calculate the various assembly errors of the flange, and determine whether the assembly errors meet the requirements. If they do, the assembly and adjustment is completed; otherwise, the auxiliary positioning points are compared.

[0147] The theoretical coordinate information of the auxiliary positioning point in the spherical coordinate system is obtained from the pose of the theoretical flange in the spherical coordinate system. , and The coordinate difference between the corresponding points is as follows:

[0148] ,

[0149] Based on comparison of auxiliary positioning points and Based on the comparison results, since the adjustable range of the auxiliary positioning points in the x and y directions is relatively small, the adjustment of the auxiliary positioning points is mainly 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 finely adjust the flange posture. After obtaining the comparison results, the operator can fine-tune the flange to minimize its deviation to within the design tolerance range. To initially fix the flange in this state, spot welding is performed using metal inert gas welding (MIG welding). MIG welding has advantages such as stable heat input, minimal spatter, and moderate penetration depth, making it suitable for the initial fixing of fine structures in medium and thin plates, and effectively reducing the risk of thermal deformation during welding.

[0150] Regarding the spot welding sequence, to control residual welding stress and avoid attitude drift as much as possible, spot welding is initiated at the flange root corresponding to the auxiliary positioning point with the largest positional deviation, and then gradually transitions to positions with smaller deviations. This "reverse deviation gradient" spot welding strategy can provide rigid constraints on areas with larger errors in the initial stage, while mitigating stress transmission caused by subsequent welding and reducing the overall cumulative error of the system.

[0151] During spot welding, operators need to allow for appropriate welding shrinkage allowance based on the deviation information obtained from the comparison. For example, a gap of 0.5~1.0 mm should be maintained in the direction of deviation to avoid overcompensation or reverse offset of the flange posture caused by welding shrinkage. Intermittent spot welding (each spot weld length not exceeding 20 mm) can be used to avoid heat concentration and reduce the risk of deformation.

[0152] The following points should also be noted during the welding process:

[0153] 1. Before welding, the welding area should be derusted, degreased, and dried to ensure arc stability;

[0154] 2. Maintain the welding torch tilt angle at 15°~20° and operate using the direct push method;

[0155] 3. Each weld point must be cooled before the next weld point is applied to prevent heat buildup and deformation.

[0156] After spot welding is completed, laser tracking measurement should be performed again to confirm that the actual position and posture of the flange meet the design requirements. If there is a slight deviation, local repair welding or removal of the weld point for readjustment can be performed to ensure the closed loop of posture adjustment and precision control during the entire assembly process.

[0157] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A measurement and adjustment method for assembling large spherical flanges, characterized in that, The specific steps include: Step 1: Based on the manufacturing error of the flange mounting holes, an improved non-dominated sorting algorithm is used to evaluate the optimal reachable pose of the flange; the improved non-dominated sorting algorithm is used to solve for the optimal reachable pose parameters of the flange, and the specific steps include: Step 101: Within 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 to construct an individual, and collect these individuals to form the initial population. P 0; Step 102: Calculate the fitness value of each generated individual on the target. After calculating the fitness value, perform non-dominated sorting and crowding calculation on the individuals in the initial population. Step 103: Select parent individuals from the current population using a tournament. Each time, randomly select two groups of individuals for comparison. Select individuals with lower non-dominance level or higher crowding 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 average of the parents. The formula for generating offspring is: ， In the formula, i Indicates the index of the function parameter. β The cross coefficient is represented by the following formula: ， In the formula, u This represents a random number that is uniformly distributed between 0 and 1. η c Indicates control parameters; when η c As the number approaches infinity, offspring genes concentrate near the parents, achieving a fine-grained local search. However, when... η c When smaller, the generated β A more dispersed distribution helps the global system escape local optima; Step 105: For each variable in each individual, use... p m The mutation probability is used to determine whether to perform mutation; then, based on the number of iterations... t To set the standard deviation of the variation σ Dynamically adjust the standard deviation of the variation in generation t. σ t for: ， ， Indicates the initial standard deviation. Indicates the maximum number of iterations. Indicates the current iteration number; If a certain variable of the offspring individuals x i If variation is needed, then follow the normal distribution. A random value Δx is generated and added to the original variable value to form a variant value; ， in, This indicates the value of the gene after the mutation operation. This represents the first individual in the current population. i’ The original values ​​of each gene; If the mutated value exceeds the range of the variable, then it is corrected as follows: ， in, Indicates the upper boundary of the variable. Indicates the lower boundary of the variable; Step 106: First, merge the parent population and the offspring population to generate a temporary population of size 2N. P' Calculate the fitness of the population, and then, according to Pareto dominance, divide the population... P' Divided into multiple non-dominated layers, among which F 1 includes the currently best non-dominated individual. F 2 includes suboptimal non-dominated individuals, and so on; finally, for each individual in the non-dominated layer, their crowding distance is... D i for: ， In the formula, f mi+1 and f mi-1 This represents the target value of the adjacent individuals on target m. f mmax This represents the maximum value of the target m. f mmin This represents the minimum value of the objective m; Step 107: Prioritize populations with lower non-dominant rank and those with greater crowding distance. P' Select the next generation population of size N. P next Then return to step 103 and continue iterative optimization until the termination condition is met. Step 2: Calibrate the flange coordinate system to obtain the coordinate information of the auxiliary positioning point in the flange coordinate system; Step 3: Based on the measured distance between the corner point of the flange mounting hole and the center of the ball, locate and weld the flange positioning block, insert the flange into the hole, and use the positioning block to roughly position the flange. Step 4: Use a laser tracker to measure the coordinate information of the auxiliary positioning point in the sphere-centered coordinate system. Based on the coordinate information of the auxiliary positioning point in the flange coordinate system in Step 2, solve for the pose of the actual flange coordinate system in the sphere-centered coordinate system. Step 5: Establish a theoretical flange coordinate system in the sphere 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 assembly errors of the flange, and determine whether the assembly errors meet the requirements. If they do, the assembly and adjustment will end. If they do not meet the requirements, proceed to step 6. Step 6: Based on the coordinate information of the auxiliary positioning point in the flange coordinate system in Step 2 and the pose of the theoretical flange coordinate system in the sphere center coordinate system in Step 5, obtain the theoretical coordinate information of the auxiliary positioning point in the sphere center coordinate system; perform spot welding on the flange root to finely adjust the flange pose by comparing the theoretical coordinates and actual coordinate information of the auxiliary positioning point, and then return to Step 4.

2. The measurement and adjustment method for assembling large spherical flanges according to claim 1, characterized in that, The assembly precision parameters of the flange are: error in the center position of the flange end face, error in the perpendicular distance from the center of the ball to the flange end face, and misalignment. Their mathematical models are as follows: ， In the formula, This indicates the error in the center position of the flange end face. The x-coordinate represents the actual position of the center of the flange end face. The x-coordinate represents the theoretical position of the flange end face center. The vertical coordinate represents the actual position of the center of the flange end face. This represents the ordinate of the theoretical position of the flange end face center. This indicates the assembly precision requirements for the center position of the flange end face. This indicates the error in the x-direction of the flange end face center position. This indicates the assembly accuracy requirement for the center position of the flange end face in the x-direction. This indicates the error in the y-direction of the flange end face center position. This indicates the assembly accuracy requirement for the center position of the flange end face in the x direction; ， In the formula, This indicates the error in the perpendicular distance from the center of the ball to the flange end face. Indicates the actual distance between the flange centers. This represents the theoretical distance between the flange centers. This indicates the required assembly precision for the vertical distance from the center of the ball to the flange end face. ； In the formula, Indicates a deviation from the center of gravity. This represents the direction vector of the centerline of the flange end face. Indicates the position of the center of the ball. Indicates the position of the center of the flange end face; Indicates a deviation from the center of gravity. This indicates the required assembly precision for the core. The error in the center position of the flange mounting hole is: ， ， In the formula, This indicates the actual position of the mounting hole in the x-direction. This indicates the theoretical position of the mounting hole in the x-direction. This indicates the required assembly accuracy of the mounting hole center position in the x-direction. This indicates the actual position of the mounting hole in the y-direction. This indicates the theoretical position of the mounting hole in the y-direction. This indicates the required assembly accuracy of the mounting hole center position in the y-direction; Therefore, the evaluation model for the flange pose is as follows: 。 3. The measurement and adjustment method for assembling large spherical flanges 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 surface points in the laser tracker measurement coordinate system. The flange end face and four outer surfaces are obtained by fitting the point cloud. The left and right outer surfaces and the top and bottom outer surfaces are bisected to obtain two relatively perpendicular left and right center planes and top and bottom center planes. The intersection point of the two center planes and the three surfaces of the end face is taken as the origin of the flange coordinate system. The normal direction of the flange end face is taken as the Z-axis of the flange coordinate system, and the normal directions of the left and right center planes are taken as the Y-axis of the flange coordinate system. The pose expression of the flange coordinate system in the laser tracker measurement coordinate system is as follows: ， ； Step 2 obtains the coordinate information of the auxiliary positioning point in the flange coordinate system. Given the pose of the flange coordinate system in the laser tracker measurement coordinate system as L and t, the auxiliary positioning point { is measured in the laser tracker measurement coordinate system. P 测量 }, the auxiliary positioning point is in the flange coordinate system { P 法兰 The coordinate value expression is: 。 4. The measurement and adjustment method for assembling large spherical flanges according to claim 1, characterized in that, In step 3, determining the position of the locating block relative to the flange end face is based on the measured distance between the intersection of the four side ribs 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 as D. The expression for calculating the distance H of the locating block relative to the flange end face is: H = D - M, After determining the position of the coarse positioning block, weld it in place. Use an overhead crane to lift the flange, and use a hand-operated hoist to adjust its position so that the flange is inserted into the flange mounting hole. The positioning block is used to coarsely position the flange.

5. The measurement and adjustment method for assembling large spherical flanges according to claim 1, characterized in that, In step 4, a laser tracker is used to measure the coordinates of the auxiliary positioning point in the spherical coordinate system. ,based on and The actual pose of the flange coordinate system in the sphere-centered coordinate system is obtained from the two point clouds using a point cloud registration algorithm.

6. The measurement and adjustment method for assembling large spherical flanges according to claim 1, characterized in that, In step 5, a theoretical flange coordinate system is established in the spherical coordinate system according to the flange assembly process requirements. The deviation between the actual flange coordinate system and the theoretical flange coordinate system is compared, and the various assembly errors of the flange are calculated. It is then determined whether the assembly errors meet the requirements. If they do, the assembly and adjustment process ends; otherwise, step 6 is performed.

7. The measurement and adjustment method for assembling large spherical flanges according to claim 1, characterized in that, Step 6 is based on In step 5, the theoretical coordinate information of the auxiliary positioning point in the sphere-centered coordinate system is obtained from the pose of the theoretical flange in the sphere-centered coordinate system. Based on comparison of auxiliary positioning points and The comparison results were used to adjust the flange root by spot welding with metal inert gas shielded welding. The spot welding operation was carried out by metal inert gas shielded welding. The spot welding sequence started from the flange root corresponding to the auxiliary positioning point with the largest position deviation and transitioned to the flange root corresponding to the smaller deviation. During the spot welding process, the welding shrinkage allowance was reserved according to the measurement results to ensure that the flange position still meets the design requirements after the final welding is completed. This was used to finely adjust the flange position and then return to step 4.

8. A measurement and adjustment system for assembling large spherical flanges, used for implementing the method described in claims 1, 2, 3, 4, 5, 6, or 7, characterized in that, It includes a storage device, a processor, a laser tracker measuring device, an attitude 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 flange as described in any one of claims 1 to 7.

9. A computer program product, characterized in that, When the computer program is executed by a processor, it can implement the steps of the method as described in any one of claims 1 to 7, and the computer program includes the following functional modules: Pose optimization module: used to build a flange assembly pose model based on the manufacturing error and assembly accuracy requirements of the flange mounting hole, and call the improved non-dominated sorting algorithm to search for the optimal solution and output the optimal assembly pose parameter set. Coordinate transformation 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 calculation module: It is used to receive the coordinates of the auxiliary positioning points measured by the laser tracker, and transform and register them with the flange coordinate system data to obtain the actual pose of the flange in the sphere center coordinate system. Assembly error calculation module: used to construct the theoretical flange pose, compare it with the actual pose, calculate various key error indicators, and determine whether the assembly tolerance requirements are met; Welding adjustment control module: When assembly errors exceed the limits, it outputs the spot welding sequence, spot welding position and welding shrinkage allowance gap based on the positional deviation of the auxiliary positioning point, and generates spot welding path suggestions. Attitude backtesting and iteration module: It is used to reacquire 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 command again and returns to the posture measurement stage to realize automatic iterative closed loop.

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