A method and system for reducing geometric gaps in forced positioning and clamping of an assembly

Abstract

The present invention provides a method and system for reducing geometric gaps in forced positioning clamping during assembly, which belongs to the field of aviation composite structure assembly technology, including: S1: conducting three-dimensional scanning and mechanical simulation analysis of complex surface features to obtain highly stable clamping points; S2: establishing a correlation model between the flexible adjustment amount and key posture deviation of a composite thin-walled structure; S3: correcting the geometric posture model; S4: solving the posture deviation correction model using an iterative algorithm and experimental measurement to reduce the geometric gap of the mating surface; S5: conducting force sensing data feedback and finite element analysis, and accurately regulating the assembly stress and geometric gap inside the composite thin-walled structure through the coordinated flexible adjustment of the clamping force load and the positioning position constraint; S6: measuring and evaluating whether key indicators such as assembly accuracy and internal stress of the composite thin-walled structure meet the standards. The present invention solves the problems that the contradiction between assembly geometric gap and internal stress is difficult to coordinate, and the assembly accuracy is difficult to achieve the optimal level.

Description

Technical Field

[0001] The invention relates to the technical field of aviation composite structure assembly, and in particular to a method and system for reducing geometric gaps in assembly forced positioning clamping. Background Art

[0002] In the field of precision assembly and testing technology of composite structure assembly engineering technology in advanced aviation manufacturing, especially in the process of forced positioning and clamping of aviation composite thin-walled structures, the essence of reducing the geometric gap between the mating surfaces of parts containing curvature is to change the geometric shape of the aviation composite thin-walled structure through the clamping force to achieve the purpose of eliminating or reducing the geometric assembly gap, thereby improving the overall mechanical properties of the composite thin-walled components. If the positioning geometric gap is directly ignored and the forced fastening connection is performed in the subsequent process, it may lead to weakening of strength, reduction of precision and functional failure at the connection of the composite thin-walled components. Therefore, eliminating the gap is crucial to ensure high-precision matching and long-term stability between composite thin-walled parts. However, as the clamping force increases, although the assembly geometric gap can be effectively reduced, it will inevitably cause large assembly internal stress inside the composite thin-walled structure. If this stress exceeds the allowable range of the aviation composite thin-walled structure, it will not only affect the overall deformation of the composite thin-walled structure itself, but may also cause cracks and other damage to the composite parts themselves or even destruction. Therefore, when implementing forced positioning and clamping operations, the key is to find a balance strategy that can fully eliminate geometric gaps through the application of clamping force to achieve ideal assembly accuracy, while ensuring that the generated assembly stress is maintained within a safe and controllable range to avoid adverse effects such as damage to the composite thin-walled structure.

[0003] Traditional technologies have the following disadvantages: ① In terms of identifying clamping points and controlling geometric gaps, they usually rely on expert experience and general rules. There is a lack of accurate basis for reasonable selection of clamping points and support from three-dimensional scanning technology at the assembly site, which may lead to inaccurate design of clamping point positions and limited effect of reducing assembly geometric gaps. ② Traditional technologies often rely on preset clamping force values, which can easily lead to excessive stress inside the thin-walled composite structure, causing damage, or fail to ensure tight fit due to too small clamping force. ③ When dealing with clamping errors and position deviations, the construction and adjustment of the geometric gap reduction model are mostly based on theoretical data, and there is a lack of dynamic iterative optimization process, which means that for unexpected position deviations that occur at the clamping site, there is no way to quickly and effectively feedback and correct them, affecting assembly accuracy. ④ Limited detection means: Traditional detection methods may only rely on simple measuring tools and visual inspections, and have limited detection capabilities for the internal stress state, tiny geometric gaps and potential defects of thin-walled composite structures, making it difficult to achieve comprehensive and in-depth quality assessment. ⑤ Insufficient consideration of environmental factors: In the clamping process, traditional technology does not take into account the impact of environmental factors such as changes in material properties (such as temperature effects) and thickness changes on the clamping effect. This may cause the geometric gap reduction effect produced by clamping to deviate from expectations in the actual assembly environment. ⑥ Human dependence: Traditional clamping operations rely heavily on the skills of workers, and use the "double two-finger" rule based on experience to eliminate geometric gaps. It is impossible to judge the distribution effect of physical states such as internal stress and damage in the assembly, and the uncertainty of the assembly process is relatively strong.

[0004] In order to ensure the smooth progress of the assembly process and guarantee the assembly quality and mechanical reliability of aviation composite thin-walled structures, the key is how to eliminate the geometric gap of the bonding surface through digital and intelligent forced positioning clamping while avoiding excessive assembly stress inside the composite thin-walled structure.

[0005] Therefore, it is necessary to study a method and system for reducing geometric gaps in the assembly of aviation composite thin-walled structures to address the shortcomings of the existing technology and to solve or alleviate one or more of the above problems. Summary of the invention

[0006] In view of this, the present invention provides a method and system for reducing geometric gaps in forced positioning clamping for assembly, which are used in the assembly process of aviation composite thin-walled structures. The method comprehensively considers the factors affecting the geometric gap and assembly stress and the relationship between the two, and reduces the assembly gap between composite parts containing curvature by flexibly adjusting the composite wall panels to the ideal position. At the same time, the clamping force applied during the assembly process is limited by the force sensor on the tooling positioner to prevent excessive assembly stress inside the composite thin-walled structure. Therefore, the problems of difficulty in coordinating the contradiction between the geometric gap and the assembly stress, and difficulty in achieving the optimal assembly accuracy are solved through the coordinated flexible adjustment of the clamping force load and the positioning position constraint.

[0007] In one aspect, the present invention provides a method for reducing geometric gaps in the assembly of an aviation composite thin-walled structure, which is used in the forced positioning and clamping process of the aviation composite thin-walled structure. The method for reducing geometric gaps comprises:

[0008] S1: Perform 3D scanning and mechanical simulation modeling on thin-walled aviation composite structures, select key positioning features of complex curved surfaces, and determine highly stable clamping points;

[0009] S2: Establish a correlation model between the flexible adjustment amount of composite thin-walled structures and the key assembly posture deviation based on high-stability clamping points;

[0010] S3: Obtain high-precision parameter values ​​of the association model through dynamic and static simulation tests of multiple factors, correct the association model, and obtain the posture deviation correction model;

[0011] S4: Use iterative algorithms and experimental measurements to solve the posture deviation correction model and reduce the geometric gap of the mating surface;

[0012] S5: Based on force sensing data feedback and finite element stress analysis, the assembly stress and geometric gap inside the composite thin-walled structure are regulated by the coordinated flexible adjustment of the clamping force load and the positioning position constraint;

[0013] S6: Measure the assembly posture, gaps, key tolerances and internal stresses between components to determine whether the assembly accuracy and internal stress indicators of the composite thin-walled structure meet the preset requirements.

[0014] According to the above aspects and any possible implementation, an implementation is further provided. According to the above aspects and any possible implementation, an implementation is further provided, wherein S1 specifically includes:

[0015] S11: Based on the overall structural characteristics of the composite thin-walled structure, the surface of the composite thin-walled structure with curvature is 3D scanned and measured for digital processing to obtain its complex surface features and identify key points that can represent the geometric features of the complex surface of the composite thin-walled structure in the spatial coordinate system;

[0016] S12: Among the key points that can represent the complex curved surface features of the composite thin-walled structure, the parts that must be positioned and clamped on the composite thin-walled structure, and the areas where the strength and stiffness of the composite thin-walled structure meet the preset assembly quality conditions are selected as the initial positioning and clamping points;

[0017] S13: Combined with the actual stress conditions and working conditions of the composite thin-walled structure, mechanical simulation software is used to simulate the stress distribution and deformation of the weak rigid workpiece during the clamping process, and the clamping scheme is optimized. After the selection of clamping points meets both the physical properties of the composite thin-walled structure and the actual engineering needs, a clamping area that can represent the complex curved surface features of the workpiece and has a stiffness that meets the preset requirements and has less influence on the deformation of the workpiece than the preset requirements is selected as the subsequent high-stability clamping point.

[0018] According to the above aspects and any possible implementation manner, an implementation manner is further provided, wherein S2 specifically includes:

[0019] S21: Determine the relative position relationship between each selected clamping point on the composite key and the center coordinate system of the tooling locator;

[0020] S22: The actual coordinate data of the clamping point is obtained by three-dimensional measurement technology, and compared with the ideal coordinates on the design digital model to obtain the actual position deviation of each clamping point;

[0021] S23: Based on the actual position deviation data, an error model between the actual position of each clamping point and the ideal target position is established;

[0022] S24: Using a deterministic positioning algorithm, the position error of the clamping point is further converted into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weakly rigid composite thin-walled workpiece.

[0023] According to the above aspects and any possible implementation, an implementation is further provided, wherein S3 specifically includes:

[0024] S31: According to the error range of the tooling locator, the position errors of each clamping point before and after the composite thin-walled structure is clamped are randomly assigned to determine the initial position deviation of each positioning clamping point;

[0025] S32: Conduct static clamping experiments to record the deformation and stress distribution data of the composite thin-walled structure under different clamping schemes;

[0026] S33: Perform a dynamic clamping experiment, record the relationship data between the composite thin-walled structure and the deformation of the composite thin-walled structure at different positioner adjustment amounts, obtain the correlation coefficient between the positioner adjustment amount and the deformation of the composite thin-walled structure, and determine the key factors that affect the distribution of assembly geometric posture deviation;

[0027] S34: Parameter values ​​are obtained experimentally through changes in material properties, thickness changes of composite thin-wall structures, and changes in clamping results corresponding to thermal expansion coefficients, and the parameter values ​​are integrated into the recorded data to establish an assembly geometry posture correction model.

[0028] According to the above aspects and any possible implementation manner, an implementation manner is further provided, wherein S4 specifically includes:

[0029] S41: Perform three-dimensional measurement of the key clamping point positions before and after the composite thin-walled structure is clamped, and record the initial position deviation of each positioning clamping point;

[0030] S42: A numerical iteration algorithm is used to solve the assembly geometric posture correction model. During the iteration process, for the clamping point, the adjustment amount of the positioner is updated according to the current actual position deviation and the ideal target position, and the positioner is adjusted in the corresponding amplitude and direction;

[0031] S43: After the adjustment is performed, the geometric clearance between the assembly mating surfaces is remeasured and a new posture deviation is calculated until the position deviation of all clamping points meets the set accuracy requirement or reaches the preset maximum number of iterations.

[0032] According to the above aspects and any possible implementation, an implementation is further provided, wherein the three-dimensional measurement tool in S41 includes but is not limited to a high-precision three-dimensional coordinate measuring machine, a laser tracker and a laser scanner.

[0033] According to the above aspects and any possible implementation manner, an implementation manner is further provided, wherein S5 specifically includes:

[0034] S51: Equipped with high-precision six-dimensional force sensors at the tooling positioning and clamping points, real-time monitoring and feedback of the magnitude of the force during the actual forced positioning and clamping process, and refined management of the force control adjustment during the assembly process;

[0035] S52: With the help of finite element analysis, through the coordinated flexible adjustment of the clamping force load and the positioning position constraint, the internal stress distribution of the composite thin-walled structure under different clamping force loads and the positioning position constraints of the tooling locator is obtained, and the mechanical model between the clamping force / clamping position and the internal stress of the composite thin-walled structure is established;

[0036] S53: During the clamping process, according to the real-time data provided by the six-dimensional force sensor and assembly posture measurement, the simulation model and parameters are corrected by comparing with the finite element model, and the clamping force load and positioning position are adjusted in time to accurately control the assembly stress and geometric gap elimination effect inside the composite thin-walled structure to meet the design requirements.

[0037] According to the aspects and any possible implementation methods described above, an implementation method is further provided, wherein the mechanical simulation analysis process of the composite thin-walled structure in S52 includes: assigning material, ply, and mechanical property parameters of assembly components in the finite element software ABAQUS, defining process constraints in combination with actual assembly conditions, establishing a finite element simulation model of the composite assembly process based on cohesive force units, and accurately characterizing assembly internal stresses; using ABAQUS secondary development to write classical damage criteria for composite laminates, evaluating the stress level state during forced assembly, and accurately characterizing the failure safety margin of microscopic damage forms through damage indexes.

[0038] According to the above aspects and any possible implementation manner, an implementation manner is further provided, wherein S6 specifically includes:

[0039] S61: Re-measure the actual positions of each key part and clamping point of the composite thin-wall structure, compare them with the ideal position on the design digital model, and check whether they meet the preset tolerance range;

[0040] S62: Check the bonding surfaces between the composite thin-walled structures to see if there is any warping or deformation caused by excessive extrusion, and ensure that the assembly geometric clearance meets the design requirements and complies with the preset elimination results of the assembly geometric clearance;

[0041] S63: Use strain gauges and ultrasonic methods to monitor the stress and damage distribution inside the composite thin-walled structure, verify whether there is local stress higher than the preset value and local damage, and evaluate whether the mechanical properties of the overall structure meet the standards.

[0042] According to the above aspects and any possible implementation, a geometric gap reduction system for assembling an aerospace composite thin-walled structure is further provided, which is used in a forced positioning and clamping process of an aerospace composite thin-walled structure, and the geometric gap reduction system for assembling the aerospace composite thin-walled structure comprises:

[0043] High-stability clamping point determination module, used for 3D scanning and mechanical simulation modeling of aviation composite thin-walled structures, selecting key positioning features of complex surfaces, and determining high-stability clamping points;

[0044] Positioning adjustment modeling module, which is used to establish the correlation model between the flexible adjustment amount of composite thin-walled structures and the key assembly posture deviation based on high-stability clamping points;

[0045] The positioning adjustment correction module is used to obtain high-precision parameter values ​​of the correlation model through dynamic and static simulation tests of multiple factors, correct the correlation model, and obtain the posture deviation correction model;

[0046] The posture deviation correction model solving module is used to solve the posture deviation correction model by using an iterative algorithm and experimental measurement to reduce the geometric clearance of the mating surface;

[0047] The assembly gap and stress coordinated control module is used to control the assembly stress and geometric gap inside the composite thin-walled structure through the coordinated flexible adjustment of the clamping force load and the positioning position constraint based on force sensing data feedback and finite element stress analysis;

[0048] The measurement and evaluation module is used to measure assembly posture, gaps, key tolerances and internal stresses between components to determine whether the assembly accuracy and internal stress indicators of the composite thin-walled structure meet the preset requirements.

[0049] Compared with the prior art, the present invention can achieve the following technical effects:

[0050] 1) Through three-dimensional scanning and mechanical simulation modeling of aviation composite thin-walled structures, key positioning features of complex surfaces are selected and highly stable clamping points are determined, laying a technological foundation for reducing assembly geometric gaps in forced positioning and clamping of aviation composite thin-walled structures.

[0051] 2) The position error of the clamping point is further converted into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weak-rigid composite thin-walled workpiece, forming a locator adjustment strategy to ensure that the assembly key reaches the ideal designed position under the adjustment of the clamping force position.

[0052] 3) Through dynamic and static clamping tests based on multiple factors, high-precision positioning adjustment model parameter correction values ​​are obtained, which can achieve precise control of the workpiece posture during the clamping process. At the same time, material properties and environmental factors are considered, thereby improving the practicality and adaptability of the clamping strategy.

[0053] 4) Through the numerical iterative solution algorithm and experimental measurement, the clamping adjustment amount of the composite thin-walled structure is gradually optimized, and the positioner is continuously adjusted until all clamping points reach the preset accuracy, thereby achieving the effect of reducing the geometric gap of the mating surface.

[0054] 5) With the help of force sensing data feedback and finite element stress analysis, real-time monitoring and refined control of the clamping force of composite thin-walled structures can be achieved. A mechanical model of clamping force and internal stress is established. Through the coordinated flexible adjustment of clamping force load and positioning position constraint, the clamping force is ensured to be moderate, which not only prevents damage to the composite thin-walled structure but also ensures the reduction of geometric gaps, thereby improving assembly quality and structural reliability.

[0055] 6) By using high-precision measuring tools and non-destructive testing technology to conduct a final inspection of the assembly effect of the composite thin-walled structure, the accuracy of the clamping adjustment, the assembly quality and the safety of the composite thin-walled structure are ensured, and the high-quality assembly of the composite thin-walled structure is fully guaranteed.

[0056] Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned technical effects at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0058] Figure 1 This is a technical step diagram of eliminating geometric gaps in forced clamping of an aviation composite thin-wall structure of the present invention;

[0059] Figure 2 It is a schematic diagram of the change of the geometric gap of a certain type of composite wall panel before and after adjustment provided by an embodiment of the present invention;

[0060] Figure 3 is a flow chart of a geometric gap elimination technique in forced clamping provided by an embodiment of the present invention;

[0061] Figure 4 It is an exploded view of the overall structure of a certain type of wing box component provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0062] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0063] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention are also intended to include plural forms, unless the context clearly indicates other meanings.

[0065] The present invention provides a method for reducing geometric gaps in the assembly of an aviation composite thin-walled structure, which is used in the forced positioning and clamping process of the aviation composite thin-walled structure. The method for reducing geometric gaps comprises:

[0066] S1: Perform 3D scanning and mechanical simulation modeling on thin-walled aviation composite structures, select key positioning features of complex curved surfaces, and determine highly stable clamping points;

[0067] S2: Establish a correlation model between the flexible adjustment amount of composite thin-walled structures and the key assembly posture deviation based on high-stability clamping points;

[0068] S3: Obtain high-precision parameter values ​​of the association model through dynamic and static simulation tests of multiple factors, correct the association model, and obtain the posture deviation correction model;

[0069] S4: Use iterative algorithms and experimental measurements to solve the posture deviation correction model and reduce the geometric gap of the mating surface;

[0070] S5: Based on force sensing data feedback and finite element stress analysis, the assembly stress and geometric gap inside the composite thin-walled structure are regulated by the coordinated flexible adjustment of the clamping force load and the positioning position constraint;

[0071] S6: Measure the assembly posture, gaps, key tolerances and internal stresses between components to determine whether the assembly accuracy and internal stress indicators of the composite thin-walled structure meet the preset requirements.

[0072] An implementation is further provided, wherein S1 specifically includes:

[0073] S11: Based on the overall structural characteristics of the composite thin-walled structure, the surface of the composite thin-walled structure with curvature is 3D scanned and measured for digital processing to obtain its complex surface features and identify key points that can represent the geometric features of the complex surface of the composite thin-walled structure in the spatial coordinate system;

[0074] S12: Among the key points that can represent the complex curved surface features of the composite thin-walled structure, the parts that must be positioned and clamped on the composite thin-walled structure, and the areas where the strength and stiffness of the composite thin-walled structure meet the preset assembly quality conditions are selected as the initial positioning and clamping points;

[0075] S13: Combined with the actual stress conditions and working conditions of the composite thin-walled structure, mechanical simulation software is used to simulate the stress distribution and deformation of the weak rigid workpiece during the clamping process, and the clamping scheme is optimized. After the selection of the clamping point meets both the physical characteristics of the composite thin-walled structure and the actual engineering needs, the clamping area that can represent the complex curved surface characteristics of the workpiece and whose stiffness meets the preset and has less influence on the deformation of the workpiece than the preset is selected as the subsequent high-stability clamping point. Among them, the preset condition of stiffness is that the overall deformation of the workpiece is within the required assembly accuracy range, and the preset small influence on the deformation of the workpiece is specifically that the overall deformation of the workpiece is within the required assembly accuracy range.

[0076] The S2 specifically includes:

[0077] S21: Determine the relative position relationship between each selected clamping point on the composite key and the center coordinate system of the tooling locator;

[0078] S22: The actual coordinate data of the clamping point is obtained by three-dimensional measurement technology, and compared with the ideal coordinates on the design digital model to obtain the actual position deviation of each clamping point;

[0079] S23: Based on the actual position deviation data, an error model between the actual position of each clamping point and the ideal target position is established;

[0080] S24: Using a deterministic positioning algorithm, the position error of the clamping point is further converted into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weakly rigid composite thin-walled workpiece.

[0081] The S3 specifically includes:

[0082] S31: According to the error range of the tooling locator, the position errors of each clamping point before and after the composite thin-walled structure is clamped are randomly assigned to determine the initial position deviation of each positioning clamping point;

[0083] S32: Conduct static clamping experiments to record the deformation and stress distribution data of the composite thin-walled structure under different clamping schemes;

[0084] S33: Perform a dynamic clamping experiment, record the relationship data between the composite thin-walled structure and the deformation of the composite thin-walled structure at different positioner adjustment amounts, obtain the correlation coefficient between the positioner adjustment amount and the deformation of the composite thin-walled structure, and determine the key factors that affect the distribution of assembly geometric posture deviation;

[0085] S34: Parameter values ​​are obtained experimentally through changes in material properties, thickness changes of composite thin-wall structures, and changes in clamping results corresponding to thermal expansion coefficients, and the parameter values ​​are integrated into the recorded data to establish an assembly geometry posture correction model.

[0086] The S4 specifically includes:

[0087] S41: Perform three-dimensional measurement of the key clamping point positions before and after the composite thin-walled structure is clamped, and record the initial position deviation of each positioning clamping point;

[0088] S42: A numerical iteration algorithm is used to solve the assembly geometric posture correction model. During the iteration process, for the clamping point, the adjustment amount of the positioner is updated according to the current actual position deviation and the ideal target position, and the positioner is adjusted in the corresponding amplitude and direction;

[0089] S43: After the adjustment is performed, the geometric clearance between the assembly mating surfaces is remeasured and a new posture deviation is calculated until the position deviation of all clamping points meets the set accuracy requirement or reaches the preset maximum number of iterations.

[0090] The three-dimensional measurement tools in S41 include but are not limited to high-precision three-dimensional coordinate measuring machines, laser trackers and laser scanners.

[0091] The S5 specifically includes:

[0092] S51: Equipped with high-precision six-dimensional force sensors at the tooling positioning and clamping points, real-time monitoring and feedback of the magnitude of the force during the actual forced positioning and clamping process, and refined management of the force control adjustment during the assembly process;

[0093] S52: With the help of finite element analysis, through the coordinated flexible adjustment of the clamping force load and the positioning position constraint, the internal stress distribution of the composite thin-walled structure under different clamping force loads and the positioning position constraints of the tooling locator is obtained, and the mechanical model between the clamping force / clamping position and the internal stress of the composite thin-walled structure is established;

[0094] S53: During the clamping process, according to the real-time data provided by the six-dimensional force sensor and assembly posture measurement, the simulation model and parameters are corrected by comparing with the finite element model, and the clamping force load and positioning position are adjusted in time to accurately control the assembly stress and geometric gap elimination effect inside the composite thin-walled structure to meet the design requirements.

[0095] The mechanical simulation analysis process of the composite thin-walled structure in S52 includes: assigning material, ply, and mechanical property parameters of assembly components in the finite element software ABAQUS, defining process constraints in combination with actual assembly conditions, establishing a finite element simulation model of the composite assembly process based on cohesive force units, and accurately characterizing assembly internal stresses; using ABAQUS secondary development to write in classic damage criteria for composite laminates, evaluating the stress level state during forced assembly, and accurately characterizing the failure safety margin of microscopic damage forms through damage indexes.

[0096] The S6 specifically includes:

[0097] S61: Re-measure the actual positions of each key part and clamping point of the composite thin-wall structure, compare them with the ideal position on the design digital model, and check whether they meet the preset tolerance range;

[0098] S62: Check the bonding surface between the composite thin-walled structures to see if there is any warping or deformation caused by excessive extrusion, and ensure that the assembly geometric clearance meets the design requirements (meets the accuracy requirements in the assembly process file) and meets the preset elimination results of the assembly geometric clearance (achieves the effective elimination effect of the assembly geometric clearance, generally within 0.2mm);

[0099] S63: Use strain gauges and ultrasonic methods to monitor the stress and damage distribution inside the composite thin-walled structure, verify whether there is local stress higher than the preset value and local damage, and evaluate whether the mechanical properties of the overall structure meet the standards.

[0100] The present invention also provides an assembly geometric gap reduction system for an aviation composite thin-walled structure, which is used in a forced positioning and clamping process of an aviation composite thin-walled structure. The assembly geometric gap reduction system comprises:

[0101] High-stability clamping point determination module, used for 3D scanning and mechanical simulation modeling of aviation composite thin-walled structures, selecting key positioning features of complex surfaces, and determining high-stability clamping points;

[0102] Positioning adjustment modeling module, which is used to establish the correlation model between the flexible adjustment amount of composite thin-walled structures and the key assembly posture deviation based on high-stability clamping points;

[0103] The positioning adjustment correction module is used to obtain high-precision parameter values ​​of the correlation model through dynamic and static simulation tests of multiple factors, correct the correlation model, and obtain the posture deviation correction model;

[0104] The posture deviation correction model solving module is used to solve the posture deviation correction model by using an iterative algorithm and experimental measurement to reduce the geometric clearance of the mating surface;

[0105] The assembly gap and stress coordinated control module is used to control the assembly stress and geometric gap inside the composite thin-walled structure through the coordinated flexible adjustment of the clamping force load and the positioning position constraint based on force sensing data feedback and finite element stress analysis;

[0106] The measurement and evaluation module is used to measure assembly posture, gaps, key tolerances and internal stresses between components to determine whether the assembly accuracy and internal stress indicators of the composite thin-walled structure meet the preset requirements.

[0107] The present invention Figure 2 This is a schematic diagram of the geometric gap change before and after local clamping and adjustment of this type of aviation composite thin-walled structure. Figure 3 The specific implementation flow chart of this solution in this embodiment is as follows. The overall idea adopted by the present invention to solve its technical problem is:

[0108] First, based on the overall structural characteristics of the composite thin-walled structure, the surface containing curvature of the composite thin-walled structure is 3D scanned and measured for digital processing, and the key points that can represent the complex curved surface characteristics of the composite thin-walled structure are identified. Combined with the actual stress conditions and working conditions of the composite thin-walled structure, the points located in the support structure of the composite thin-walled structure or the high-strength and high-rigidity areas are preferentially selected as clamping points, and the clamping scheme is optimized through mechanical simulation to adapt to the physical characteristics and engineering requirements of the aviation composite thin-walled structure. Secondly, the relative position relationship between the selected clamping point and the center coordinate system of the locator is established, and the position error of the clamping point is further converted into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weak rigid composite thin-walled workpiece. Thirdly, through multi-factor dynamic and static clamping simulation tests, as well as the collection of various parameters including material properties, thickness changes of composite thin-walled structures and thermal expansion coefficients, the model is improved, high-precision model parameter values ​​are obtained, and an assembly geometric posture correction model is established to more accurately reflect the actual clamping situation. Afterwards, the error correction model is solved by using a numerical iteration algorithm. For each clamping point, the positioner is continuously iteratively adjusted according to the actual position deviation and the ideal target position until the positions of all clamping points meet the preset accuracy requirements and the geometric gap of the mating surface is reduced. Then, force sensors are installed at the clamping points to monitor the clamping force in real time, and the internal stress distribution of the composite thin-walled structure under different clamping forces is predicted by finite element analysis. Through the coordinated flexible adjustment of the clamping force load and the positioning position constraint, a mechanical model between the assembly force and the internal stress of the composite thin-walled structure is established to guide the adjustment of the clamping force and ensure that the internal stress of the composite thin-walled structure is kept within the safety limit while eliminating the gap between the bonding surfaces. Finally, after the assembly is completed, the composite thin-walled structure is measured and inspected in an all-round and high-precision manner, including the actual position and posture of key parts, the gap and deformation of the bonding surface, the internal stress distribution, etc., to comprehensively evaluate whether the composite thin-walled structure meets the mechanical properties and assembly function requirements specified in the design.

[0109] The present invention provides a geometric gap elimination technology in forced clamping of an aviation composite thin-walled structure. The geometric gap elimination technology is used for the assembly stage of the aviation composite thin-walled structure. At the same time, the forced positioning clamping is used to eliminate the geometric gap of the bonding surface of the aviation composite thin-walled structure, which causes excessive assembly stress inside the composite thin-walled structure, which may cause damage and other problems. The technology is mainly used to optimize the geometric gap and assembly stress to achieve a balanced state and meet engineering requirements, such as Figure 3 As shown, the geometric gap elimination technology in the forced clamping of the aviation composite thin-walled structure includes the following specific technical implementation processes:

[0110] S1: Perform 3D scanning and mechanical simulation modeling on aviation composite thin-walled structures, select key positioning features of complex curved surfaces, and determine highly stable clamping points.

[0111] The S1 specifically includes:

[0112] S11: Based on the overall structural characteristics of the composite thin-walled structure, the surface of the composite thin-walled structure with curvature is 3D scanned and measured for digital processing to obtain its complex surface features and identify key points that can represent the geometric features of the complex thin-walled surface of the composite material in the spatial coordinate system;

[0113] S12: Among the key points that can represent the complex curved surface features of the composite thin-walled structure, the parts that must be positioned and clamped on the composite thin-walled structure, and the areas where the strength and stiffness of the composite thin-walled structure meet the preset assembly quality conditions are selected as the initial positioning and clamping points;

[0114] S13: Combined with the actual stress conditions and working conditions of the composite thin-walled structure, mechanical simulation software is used to simulate the stress distribution and deformation of the weak rigid workpiece during the clamping process, and the clamping scheme is optimized. After the selection of clamping points meets both the physical properties of the composite thin-walled structure and the actual engineering needs, the clamping area that can represent the complex curved surface features of the workpiece, has high rigidity and has little effect on the deformation of the workpiece is selected as the subsequent high-stability clamping point.

[0115] Specifically, 3D scanning technology is first used to collect topological shape data of the curvature-containing surface of aviation composite thin-walled structures to generate a high-precision three-dimensional point cloud model. Based on this, professional software is used to identify surface features and find key points that can represent the complex curved surface features of composite thin walls in the spatial coordinate system, including but not limited to places with large curvature changes, shape assembly seams, shape covers, etc.

[0116] Furthermore, among the key characteristic points identified above, areas with stable structure, high rigidity and strength in the composite thin-wall are selected as the locations of the clamping points, as well as areas that are particularly prone to deformation, and are set as initial positioning clamping points, so that the clamping points can better withstand the clamping force, and limit the weak rigid deformation of the composite thin-wall structure, so as to prevent undesirable deformation or damage of the aviation composite thin-wall structure caused by excessive local stress.

[0117] Furthermore, mechanical simulation software is used to simulate the loads borne by the composite thin-walled structure during the clamping process in combination with the actual working conditions and working status of the composite thin-walled structure. The stress distribution, strain response and overall deformation of the composite thin-walled structure are calculated and analyzed. Through repeated simulation calculations and optimization iterations, the clamping scheme is optimized, and the clamping point positions that can represent the complex surface features of the workpiece and are suitable are selected to ensure that the highly stable clamping points finally selected have the least impact on the composite thin-walled structure itself and can meet the actual assembly needs of the project.

[0118] S2: Establish a model for the relationship between the flexible adjustment amount and key assembly posture deviation of composite thin-walled structures.

[0119] The S2 specifically includes:

[0120] S21: Determine the relative position relationship between each selected clamping point on the composite key and the center coordinate system of the tooling locator;

[0121] S22: The actual coordinate data of the clamping point is obtained by three-dimensional measurement technology, and compared with the ideal coordinates on the design digital model to obtain the actual position deviation of each clamping point;

[0122] S23: Based on the actual position deviation data, an error model between the actual position of each clamping point and the ideal target position is established;

[0123] S24: Using a deterministic positioning algorithm, the position error of the clamping point is further converted into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weakly rigid composite thin-walled workpiece.

[0124] Specifically, first determine the relative position between each selected clamping point and the center coordinate system of the locator. The coordinates of the clamping points are , and the corresponding locator coordinates are , then the relative position relationship between the two can be expressed as:

[0125]

[0126] Furthermore, the selected clamping points of the composite thin-walled structure are measured on site with the help of 3D measurement technology, such as laser tracker or laser scanner, to obtain the actual assembly process. The coordinates of the clamping points are . The coordinate values ​​obtained by actual measurement The ideal coordinates set theoretically in the design model By making a one-to-one comparison, we can conclude that The actual position deviation of the clamping points:

[0127]

[0128] Furthermore, based on the actual position deviation of each clamping point , establish the error model between the actual position of each clamping point and the ideal target position ,The model can systematically describe and predict the position change trend that may occur in the actual clamping process.

[0129] Furthermore, in order to achieve precise control of the clamping process of the composite thin-walled structure, a deterministic positioning algorithm is used to convert the above error model into the positioner adjustment value Ideal target pose of composite thin-walled structure The mathematical relationship between them can be expressed as:

[0130]

[0131] in, The conversion function further converts the position error of the clamping point into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weakly rigid composite thin-walled workpiece. This model is used to guide how to adjust the locator according to the current actual deviation of the composite assembly to achieve the ideal target position and posture.

[0132] S3: Obtain high-precision model parameter values ​​through multi-factor dynamic and static simulation tests and correct the assembly geometric posture model.

[0133] The S3 specifically includes:

[0134] S31: According to the error range of the tooling locator, the position errors of each clamping point before and after the composite thin-walled structure is clamped are randomly assigned to determine the initial position deviation of each positioning clamping point;

[0135] S32: Conduct static clamping experiments to record the deformation and stress distribution data of composite thin-walled structures under different clamping schemes;

[0136] S33: Conduct dynamic clamping experiments, record the relationship data between the positioner adjustment amount and the deformation of the composite thin-walled structure, obtain the correlation coefficient between the positioner adjustment amount and the deformation of the composite thin-walled structure, and determine the key factors affecting the distribution of assembly geometric posture deviation;

[0137] S34: Parameter values ​​are obtained experimentally through changes in material properties, thickness changes of composite thin-wall structures, and changes in clamping results corresponding to thermal expansion coefficients, and the parameter values ​​are integrated into the recorded data to establish an assembly geometry posture correction model.

[0138] Specifically, according to the positioning error range specified by the tooling locator, such as [-0.1mm, 0.1mm], the position errors of each clamping point before and after the clamping of the composite thin-walled structure are randomly assigned, or the initial position deviation of each positioning clamping point is determined based on on-site experience. Based on this, the initial position deviation of the clamping point relative to the ideal position is calculated according to the above formula as the input of the dynamic and static simulation test, providing an accurate benchmark reference for the subsequent establishment and verification of the error model in the clamping process.

[0139] Furthermore, static clamping experiments are carried out under different clamping conditions or schemes to record the deformation of the aviation composite thin-walled structure after clamping, as well as the changes in the stress distribution inside the assembled structure.

[0140] Furthermore, dynamic clamping experiments were carried out to record the relationship data between the composite thin-walled structure and the deformation of the composite thin-walled structure at different positioner adjustment amounts, obtain the correlation coefficient between the positioner adjustment amount and the deformation of the composite thin-walled structure, determine the key factors affecting the distribution of assembly geometric posture deviation, and realize the tooling positioner adjustment amount. Ideal target pose of composite thin-walled structure The detailed mathematical expression between .

[0141] Furthermore, considering the influence of factors such as material properties, thickness changes of composite thin-walled structures and temperature effects on the clamping effect, through special experimental research, the mechanical parameters of the composite thin-walled structure material such as elastic modulus, Poisson's ratio, yield strength, and the thermal expansion parameters of the composite thin-walled structure under temperature changes are obtained, and integrated into the error model and mechanical simulation calculations to obtain the corresponding changes in the clamping results, and the parameter values ​​are integrated into the recorded data to establish an assembly geometry posture correction model to improve the model's simulation applicability to the actual clamping process.

[0142] S4: Use iterative algorithms and experimental measurements to solve the posture deviation correction model and reduce the geometric gap between the mating surfaces.

[0143] The S4 specifically includes:

[0144] S41: Perform three-dimensional measurement of the key clamping point positions before and after the composite thin-walled structure is clamped, and record the initial position deviation of each positioning clamping point;

[0145] S42: A numerical iteration algorithm is used to solve the assembly geometric posture correction model. During the iteration process, for the clamping point, the adjustment amount of the positioner is updated according to the current actual position deviation and the ideal target position, and the positioner is adjusted in the corresponding amplitude and direction;

[0146] S43: After the adjustment is performed, the geometric clearance between the assembly mating surfaces is remeasured and a new posture deviation is calculated until the position deviation of all clamping points meets the set accuracy requirement or reaches the preset maximum number of iterations.

[0147] Specifically, a high-precision three-dimensional measuring tool such as a three-dimensional coordinate measuring machine, a laser tracker or a laser scanner is used to perform three-dimensional measurement of the positions of key clamping points before and after clamping of the composite thin-walled structure, and record the initial position deviation of each positioning clamping point.

[0148] Specifically, in the process of clamping error correction of composite thin-walled structures, a numerical iterative algorithm is used to solve the assembly geometry correction model by gradually approaching the optimal solution through multiple iterations. In the first iteration, the composite thin-walled structure Clamping points, calculate the positioner adjustment The adjustment includes: rotation angle around the XYZ axis And the size of the movement adjustment along the XYZ axis .

[0149] Furthermore, after completing the nth positioner adjustment, the geometric clearance between the assembly mating surfaces is measured again using high-precision measuring equipment and the new posture deviation is calculated. These new position deviation data are then compared with the set accuracy requirements. If there are still assembly posture deviations on key products that exceed the specified range, the next round of iteration is continued, and the above error correction steps are repeated, that is, the positioner is adjusted again according to the newly calculated assembly posture to gradually reduce the deviation.

[0150] Furthermore, the above iterative process is repeated until the position deviations of all clamping points meet the preset accuracy requirements or reach the preset maximum number of iterations. In this process, each iteration is a feedback and improvement of the last adjustment result. Through continuous iterative optimization, the clamping position of the composite thin-walled structure is precisely controlled, ensuring that the composite thin-walled structure achieves the required position and posture accuracy during the assembly process, while also achieving effective reduction of the geometric clearance of the mating surface.

[0151] S5: With the help of force sensing data feedback and finite element stress analysis, the assembly stress and geometric gap inside the composite thin-walled structure can be precisely controlled through the coordinated flexible adjustment of the clamping force load and the positioning position constraint.

[0152] The S5 specifically includes:

[0153] S51: Equipped with high-precision six-dimensional force sensors at the tooling positioning and clamping points, real-time monitoring and feedback of the magnitude of the force during the actual forced positioning and clamping process, and refined management of the force control adjustment during the assembly process;

[0154] S52: With the help of finite element analysis, through the coordinated flexible adjustment of the clamping force load and the positioning position constraint, the internal stress distribution of the composite thin-walled structure under different clamping force loads and the positioning position constraints of the tooling locator is obtained, and the mechanical model between the clamping force / clamping position and the internal stress of the composite thin-walled structure is established;

[0155] S53: During the clamping process, according to the real-time data provided by the six-dimensional force sensor and assembly posture measurement, the simulation model and parameters are corrected by comparing with the finite element model, and the clamping force load and positioning position are adjusted in time to accurately control the assembly stress and geometric gap elimination effect inside the composite thin-walled structure to meet the design requirements.

[0156] Specifically, in order to achieve refined control of assembly force during the clamping process of composite thin-walled structures, a high-precision six-dimensional force sensor is configured at each clamping point to capture and accurately measure the force between the composite thin-walled structure and the tooling locator during the clamping process in real time, forming a continuous and dynamic force signal feedback. Through real-time monitoring of the force value, the control system of the clamping system adjusts the working state of the clamping device at any time based on the sensor data to ensure that the clamping force is neither too large to cause excessive deformation or damage to the composite thin-walled structure, nor too small to cause the composite thin-walled structure to be unable to be firmly fixed, thereby achieving refined control and management of the clamping force of the composite thin-walled structure.

[0157] Furthermore, the finite element analysis technology is used to predict and simulate the internal stress distribution of the composite thin-walled structure under the action of different clamping force magnitudes and positioning position constraints through the coordinated flexible adjustment of the clamping force load and the positioning position constraint. By establishing a mechanical response simulation model of the composite thin-walled structure, the stress and strain distribution inside the composite thin-walled structure is simulated. Based on these simulation results, a mechanical model between the assembly force / clamping position and the internal stress of the composite thin-walled structure is established to reveal the inherent relationship between the internal stress distribution of the composite thin-walled structure in forced assembly positioning:

[0158]

[0159] In the formula, represents the stress response matrix, For the The stress value of each monitoring point, is a matrix whose elements Reflects the The stress response of each monitoring point is Mechanical relationship coefficient between the force / position load of each clamping point; is a The column vector of represents the stress value of each monitoring point without external force.

[0160] Furthermore, in the actual clamping process, according to the real-time data provided by the six-dimensional force sensor and the assembly posture measurement, the simulation model and parameters are corrected and the clamping force load and positioning position are adjusted in time according to the finite element model. Once it is found that the actual clamping force may cause the internal stress of the composite thin-walled structure to exceed the safety threshold, the system will immediately adjust the torque or pressure of the clamping device to ensure that while effectively eliminating the gap between the fitting surface of the composite thin-walled structure and other components, the internal stress of the composite thin-walled structure is kept within the safe range allowed by the design to the maximum extent, realizing the intelligent and dynamic control of the clamping force of the composite thin-walled structure.

[0161] S6: Measure assembly posture, gaps, key tolerances and internal stresses between components to evaluate whether key indicators such as assembly accuracy and internal stress of composite thin-walled structures meet the standards.

[0162] The S6 specifically includes:

[0163] S61: Re-measure the actual positions of each key part and clamping point of the composite thin-wall structure, compare them with the ideal position on the design digital model, and check whether they meet the preset tolerance range;

[0164] S62: Check the bonding surface between the composite thin-walled structures to see if there is any warping or deformation caused by excessive extrusion, and ensure that the assembly geometric clearance meets the design requirements to effectively eliminate the assembly geometric clearance;

[0165] S63: Use strain gauges and ultrasonic methods to monitor the stress and damage distribution inside the composite thin-walled structure, verify whether there is excessive local stress and local damage, and evaluate whether the mechanical properties of the overall structure meet the standards.

[0166] Specifically, after completing the clamping and adjustment of the composite thin-walled structure, in order to verify the final assembly geometry and physical quality, a three-coordinate measuring machine, laser tracker or laser scanner is used to perform a second precise measurement of the actual positions of the key connection parts and clamping points of the composite thin-walled structure. The measurement results are compared with the ideal positions on the design digital model to check whether the actual assembly positions of the key points of the composite thin-walled structure fall within the predetermined tolerance range, thereby evaluating the effectiveness of the clamping and adjustment work.

[0167] Furthermore, through visual inspection and the assistance of precision measuring tools, check the fit between the composite thin-walled structure and other structural parts to ensure that there is no out-of-tolerance assembly geometric gap; at the same time, observe whether there is local extrusion deformation or warping of the composite thin-walled structure due to excessive clamping force to ensure that the geometric shape of the composite thin-walled structure meets the design requirements and effectively eliminate the assembly geometric gap.

[0168] Furthermore, in order to deeply evaluate the stress state inside the composite thin-walled structure, strain gauge technology is used to attach to the key positions of the composite thin-walled structure, and the stress distribution inside the composite thin-walled structure is indirectly inferred based on its displayed values. In addition, ultrasonic flaw detection technology is used to perform non-destructive testing on the composite thin-walled structure to detect possible internal cracks, delamination and other assembly damage defects, and to evaluate whether local damage occurs in local areas, and to determine whether the mechanical properties of the overall structure meet the standards, thereby ensuring the overall structural stability and service safety of the composite thin-walled structure.

[0169] The present invention provides a geometric gap elimination technology in the forced clamping of aviation composite thin-walled structures, which provides an effective solution to the problems of accurately identifying high-stability clamping points, finely controlling clamping force and clamping positioning errors, and balancing and coordinating the contradictions between assembly geometric gaps and assembly internal stresses in the assembly of aviation composite curved surface weak-rigidity thin-walled structures.

[0170] The present invention mainly includes three parts, namely: the selection of high-stability clamping points on curved parts, modeling, correction and solution of positioning adjustment, and coordinated regulation and evaluation of assembly geometric clearance and internal stress. Based on the measured data, the positioner adjustment can be accurately controlled to eliminate the geometric clearance caused by the assembly of composite thin-walled structures; at the same time, the internal assembly stress of aviation composite thin-walled structures can be finely regulated in combination with the state monitoring of composite thin-walled structures, which can effectively eliminate the assembly geometric clearance and reasonably control the assembly internal stress, achieving the dual guarantee effect of improving the assembly quality of aviation composite thin-walled structures and performance indicators. After example optimization verification, the present invention can achieve:

[0171] 1) Through three-dimensional scanning and mechanical simulation modeling of aviation composite thin-walled structures, key positioning features of complex surfaces are selected and highly stable clamping points are determined, laying a technological foundation for reducing assembly geometric gaps in forced positioning and clamping of aviation composite thin-walled structures.

[0172] 2) The position error of the clamping point is further converted into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weak-rigid composite thin-walled workpiece, forming a locator adjustment strategy to ensure that the assembly key reaches the ideal designed position under the adjustment of the clamping force position.

[0173] 3) Through dynamic and static clamping tests based on multiple factors, high-precision positioning adjustment model parameter correction values ​​are obtained, which can achieve precise control of the workpiece posture during the clamping process. At the same time, material properties and environmental factors are considered, thereby improving the practicality and adaptability of the clamping strategy.

[0174] 4) Through the numerical iterative solution algorithm and experimental measurement, the clamping adjustment amount of the composite thin-walled structure is gradually optimized, and the positioner is continuously adjusted until all clamping points reach the preset accuracy, thereby achieving the effect of reducing the geometric gap of the mating surface.

[0175] 5) With the help of force sensing data feedback and finite element stress analysis, real-time monitoring and refined control of the clamping force of composite thin-walled structures can be achieved. A mechanical model of clamping force and internal stress is established. Through the coordinated flexible adjustment of clamping force load and positioning position constraint, the clamping force is ensured to be moderate, which not only prevents damage to the composite thin-walled structure but also ensures the reduction of geometric gaps, thereby improving assembly quality and structural reliability.

[0176] 6) By using high-precision measuring tools and non-destructive testing technology to conduct a final inspection of the assembly effect of the composite thin-walled structure, the accuracy of the clamping adjustment, the assembly quality and the safety of the composite thin-walled structure are ensured, and the high-quality assembly of the composite thin-walled structure is fully guaranteed. Example 1

[0177] In this embodiment, a composite wing box assembly application of a certain type of aircraft is taken as an example ( Figure 4 ). The assembly of the composite wing box components is divided into four steps: ① Fix and install the left and right walls and the first and fourth frame parts on the tooling; ② Use this as a positioning reference to install the second and fourth frames; ③ Install the composite lower wall panel assembly; ④ Install the composite lower wall panel assembly to form a complete wing box component. The above positioning and clamping installation processes all require the assistance of assembly tooling fixtures.

[0178] Firstly, 3D scanning technology is used to capture high-precision data of wing box components such as the left wall, right wall, first frame, second frame, third frame, fourth frame, composite upper wall panel, and composite lower wall panel. Key feature points are identified through software analysis as the basis for clamping. Finite element analysis is used to verify the effectiveness of the clamping points, and the clamping strategy is optimized to ensure structural stability. Secondly, the left and right walls and the first and fourth frame structural parts are installed first. The clamping deviations of the clamping points on each component are accurately determined through three-dimensional measurement technology, and an assembly posture error model is established to guide the fine-tuning of the positioner. Thirdly, on the scaled model of the wing box skeleton assembly, stress detection and ultrasonic analysis are combined to obtain the positioning adjustment amount of the vacuum suction cup flexible positioner ( Figure 2 ) and the deformation of the skeleton, and taking into account the complex influence of material properties and environmental factors on the clamping effect, the algorithm is iteratively optimized and adjusted; then, force sensing monitoring is implemented in the above-mentioned entire clamping process, the assembly force and the clamping force position are dynamically adjusted to maintain an appropriate stress level, and the finite element simulation is used to predict the stress distribution and structural deformation under different clamping forces / clamping positions; then, after the skeleton composed of the left and right walls and the first and fourth frames is assembled, the assembly accuracy and quality of the frame are verified by multiple detection methods such as three-coordinate measurement, laser tracking, visual and precision measuring tool inspection, strain gauges and ultrasonic flaw detection to ensure that there are no assembly damage defects and the assembly stress is controlled; finally, the two ribs are installed to form the skeleton based on the frame, and the upper and lower wall panels of the composite material are installed based on the skeleton, and the above-mentioned adjustment process is repeated, and the high-quality assembly of the entire wing box structure is completed through the coordinated flexible adjustment of the clamping force load and the positioning position constraint. During this period, the geometric matching clearance and stress state between the upper and lower wall panels and each skeleton part, and between each skeleton part are continuously monitored to evaluate whether the key indicators such as the geometric clearance and internal stress of the composite thin-walled structure assembly meet the standards. The geometric gap elimination technology for a certain type of wing box assembly includes the following steps:

[0179] Specifically, 3D scanning technology is first used to collect data on each component of the composite wing box, including the left wall, right wall, front and rear beams, frame plates, partitions, and composite upper and lower skins, to generate a high-precision three-dimensional point cloud model of the structural surface. Professional software is then used to identify the key features of each component, and to find the key positioning points that can represent the complex features of the wing box components in the spatial coordinate system.

[0180] Furthermore, among the key positioning feature points identified above, key feature points where the components constituting the wing box have high strength and rigidity, stable structure, or are very prone to assembly deformation are selected as initial positioning clamping points.

[0181] Furthermore, the wing box was modeled by finite element three-dimensional modeling, and the material properties of the left wall, right wall, skin and other components were set, and the force was applied on the initial clamping point selected above. The model was imported into ABAQUS finite element software for analysis. After the force was applied at the clamping point of the composite wing box as a whole, the stress distribution, strain response and stability of the wing box structure were obtained through post-processing. The appropriate positioning clamping point position was selected through repeated simulation calculations and optimization iterations.

[0182] Furthermore, the left and right walls and the first and fourth frame structural parts are fixed and installed on the tooling. The subsequent assembly is based on the frame, so it is necessary to further adjust and reduce the geometric gap of each fitting surface to improve the assembly accuracy. First, determine the relative position between the selected clamping points on the left and right walls and the first and fourth frames and the center coordinate system of the locator. Use the three-dimensional measurement technology to measure the clamping points on these four parts on site to obtain the spatial coordinates of the actual clamping points. Compare the spatial coordinates of the actual clamping points with the spatial coordinates of the ideal clamping points on the design digital model to obtain the actual position deviation of each clamping point on the left wall, right wall, first frame, and fourth frame; secondly, establish an error model between the actual position deviation of the clamping points on each skeleton part and the posture of the outer edge surface of the skeleton part, and use a deterministic positioning algorithm to describe and predict the position change trend of the clamping point during the actual clamping process. Finally, the position error of the clamping point is further converted into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weak rigid composite thin-walled workpiece.

[0183] Furthermore, a laser tracker or laser interferometer is used to accurately measure the spatial positions of the left wall, right wall, first frame and fourth frame of the wing box before and after clamping, reflecting the initial position deviation of each point relative to the ideal position before clamping.

[0184] Furthermore, based on the wing box scaled model, static clamping experiments were carried out, that is: under different clamping conditions, the deformation and stress distribution data of the skeleton parts under different clamping schemes were recorded; dynamic clamping experiments were carried out to record the relationship data of the structural deformation of the skeleton parts under different locator adjustments, and the changes in the internal stress distribution of the frame composed of the left wall, right wall, first frame and fourth frame were obtained through stress detection technology, and the correlation between the locator adjustment amount and the deformation of each skeleton part was quantitatively analyzed.

[0185] Furthermore, considering the influence of factors such as the material properties, thickness changes and temperature effects of the skeleton parts on the clamping effect, through special experimental research, the mechanical parameters such as elastic modulus, Poisson's ratio, yield strength of each component material, as well as the thermal expansion performance index of the frame under temperature changes are obtained. These parameter values ​​are incorporated into the error model and mechanical simulation calculation to improve the simulation accuracy of the model for the actual clamping process of the skeleton components.

[0186] Furthermore, a numerical iterative algorithm is used to solve the assembly geometry posture correction model by gradually approaching the optimal solution through multiple iterations, and the positioning adjustment of the skeleton parts is calculated: the spatial displacement and rotation angle of the X, Y, and Z axes.

[0187] Furthermore, after the adjustment is completed, the three-dimensional measuring tools such as coordinate measuring machine, laser tracker or laser scanner are used to detect the position of the clamping points of each component clamped on the skeleton locator, calculate the new actual position deviation, and then compare these new position deviation data with the set assembly accuracy requirements. If there are still clamping points whose position deviation exceeds the specified range, continue to the next round of iteration and repeat the above error correction steps.

[0188] Furthermore, in the above-mentioned process of adjusting the spatial position of the skeleton assembly composed of the left wall, the right wall, the first frame and the fourth frame, in order to achieve refined control of the assembly force, a six-dimensional force sensor is configured at each clamping point to capture and accurately measure in real time the force value applied to each skeleton part during the clamping process. Based on the sensor data, the working state of the skeleton locator is adjusted at any time through the coordinated flexible adjustment of the clamping force load and the positioning position constraint to ensure that the force of each clamping point can clamp the frame without causing excessive assembly stress inside the skeleton assembly.

[0189] Furthermore, finite element analysis technology is used to predict and simulate the internal stress distribution of the skeleton component under different clamping forces / clamping positions, and a mechanical model between the assembly force / clamping position and the internal stress of the skeleton component is established.

[0190] Furthermore, during the clamping process, based on the above-mentioned mechanical model and real-time data provided by the six-dimensional force sensor, the adjustment of the clamping force and the clamping position is guided by the results predicted by the model, and the assembly stress and geometric gap elimination effects inside the composite thin-walled structure are precisely controlled to meet the design requirements.

[0191] Furthermore, after completing the clamping and adjustment of the skeleton assembly, in order to verify the accuracy and quality of the final assembly, a three-dimensional measuring device is used to perform a second precise measurement of the key parts of the connection between the left wall and the first frame, the fourth frame, and the right wall and the first frame, the fourth frame of the skeleton assembly, as well as the actual positions of the clamping points. The measurement results are compared with the ideal assembly posture on the design digital model to check whether they fall within the predetermined tolerance range.

[0192] Furthermore, the assembly geometric clearances of the four mating surfaces, namely, the left wall and the first frame, the right wall and the first frame, the left wall and the fourth frame, and the right wall and the fourth frame, are checked by visual inspection and with the aid of precision measuring tools to ensure the assembly quality of the wing box skeleton assembly.

[0193] Furthermore, strain gauges are attached to the left wall, right wall, first frame, and fourth frame key positions, and the stress distribution inside the skeleton components is indirectly calculated based on the displayed values ​​by monitoring the changes in the resistance of the strain gauges. In addition, ultrasonic flaw detection technology is used to perform non-destructive testing on the skeleton components to detect possible internal cracks, delamination, and other assembly damage defects, and to assess whether local damage has occurred in local areas to determine whether the mechanical properties of the overall structure meet the standards.

[0194] Furthermore, after the left wall, right wall, first frame and fourth frame are adjusted and installed on the tooling to form a skeleton assembly, the two wall panel parts inside the skeleton are installed using this as a positioning reference, and the above adjustment steps are repeated to reduce the geometric gap while controlling the internal assembly stress in real time.

[0195] Furthermore, after the above operations, the left wall, the right wall, the first frame, the fourth frame, and the two ribs form a wing box frame, which is used as a reference for installing the composite upper and lower wall panel structural members. Figure 2 After the vacuum suction cup positioner in is installed, the above steps are adjusted to complete the installation of the entire wing box. During this process, each component installed on the tooling is monitored in real time, with a focus on monitoring the assembly geometric clearances and step differences between the left wall and the first frame, the left wall and the fourth frame, the right wall and the first frame, the right wall and the fourth frame, the left wall and the upper and lower wall panels, the right wall and the upper and lower wall panels, the first frame and the upper and lower wall panels, the fourth frame and the upper and lower wall panels, the two ribs and the upper and lower wall panels, as well as the corresponding assembly internal stresses and damage conditions of these matching parts, to ensure that the assembly geometric clearances are effectively eliminated, avoid the occurrence of excessive assembly internal stresses and damage, and collaboratively guarantee the assembly geometry and physical properties of the wing box components.

[0196] The assembly geometric gap elimination technology in the forced positioning clamping of aviation composite thin-walled structures proposed in the present invention mainly includes the following three parts: selection of high-stable clamping points on curved parts, modeling, correction and solution of positioning adjustment amounts, and coordinated regulation and evaluation of assembly geometric gaps and internal stresses. Based on the measured data, the positioner adjustment can be accurately controlled to eliminate the geometric gap caused by the assembly of the composite thin-walled structure; at the same time, the internal assembly stress of the aviation composite thin-walled structure can be finely regulated in combination with the state monitoring of the composite thin-walled structure, which can effectively eliminate the assembly geometric gap and reasonably control the assembly internal stress, thereby achieving the dual guarantee effect of improving the assembly quality of the aviation composite thin-walled structure and the performance indicators. The following can be achieved: ① Rationally select key feature points with high stiffness as clamping points to achieve balanced force and prevent deformation; ② Use iterative algorithms to accurately solve the mathematical model between the position deviation of the clamping point and the adjustment amount of the locator, and gradually adjust the locator to accurately adjust the shape of the composite thin-walled structure and eliminate the gap between the fitting surfaces; ③ With the help of force sensors, finely control the assembly force to eliminate geometric gaps and ensure that the internal assembly stress of the composite thin-walled structure is within a safe range; ④ During the flexible assembly and adjustment process, the state of the composite thin-walled structure is continuously measured to ensure that the preset geometric and physical assembly quality requirements are met.

[0197] The above is a detailed introduction to a method and system for reducing geometric gaps in assembly forced positioning clamping provided by the embodiment of the present application. The description of the above embodiment is only used to help understand the method and its core idea of ​​the present application; at the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0198] For example, certain words are used in the specification and therein to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification does not use the difference in name as a way to distinguish components, but uses the difference in function of the components as the criterion for distinction. As mentioned in the entire specification, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of implementing the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application.

[0199] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0200] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0201] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or technology or knowledge in the relevant field.

Claims

1. A method for reducing the assembly geometric gap in the forced positioning and clamping of an aviation composite thin-walled structure, characterized in that: The geometric gap reduction method comprises: S1: Perform 3D scanning and mechanical simulation modeling on thin-walled aviation composite structures, select key positioning features of complex curved surfaces, and determine highly stable clamping points; S2: Establish a correlation model between the flexible adjustment amount of composite thin-walled structures and the key assembly posture deviation based on high-stability clamping points; S3: Obtain high-precision parameter values ​​of the association model through dynamic and static simulation tests of multiple factors, correct the association model, and obtain the posture deviation correction model; S4: Use iterative algorithms and experimental measurements to solve the posture deviation correction model and reduce the geometric gap of the mating surface; S5: Based on force sensing data feedback and finite element stress analysis, the assembly stress and geometric gap inside the composite thin-walled structure are regulated by the coordinated flexible adjustment of the clamping force load and the positioning position constraint; S6: Measure the assembly posture, gap, key tolerance and internal stress between components to determine whether the assembly accuracy and internal stress index of the composite thin-walled structure meet the preset requirements; The S2 specifically includes: S21: Determine the relative position relationship between each selected clamping point on the composite key and the center coordinate system of the tooling locator; S22: The actual coordinate data of the clamping point is obtained by three-dimensional measurement technology, and compared with the ideal coordinates on the design digital model to obtain the actual position deviation of each clamping point; S23: Based on the actual position deviation data, an error model between the actual position of each clamping point and the ideal target position is established; S24: Using a deterministic positioning algorithm, the position error of the clamping point is further converted into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weakly rigid composite thin-walled workpiece; The S4 specifically includes: S41: Perform three-dimensional measurement of the key clamping point positions before and after the composite thin-walled structure is clamped, and record the initial position deviation of each positioning clamping point; S42: A numerical iteration algorithm is used to solve the assembly geometric posture correction model. During the iteration process, for the clamping point, the adjustment amount of the positioner is updated according to the current actual position deviation and the ideal target position, and the positioner is adjusted in the corresponding amplitude and direction; S43: After the adjustment is performed, the geometric clearance between the assembly mating surfaces is re-measured and a new posture deviation is calculated until the position deviations of all clamping points meet the set accuracy requirements or reach the preset maximum number of iterations; The S5 specifically includes: S51: Equipped with high-precision six-dimensional force sensors at the tooling positioning and clamping points, real-time monitoring and feedback of the magnitude of the force during the actual forced positioning and clamping process, and refined management of the force control adjustment during the assembly process; S52: With the help of finite element analysis, through the coordinated flexible adjustment of the clamping force load and the positioning position constraint, the internal stress distribution of the composite thin-walled structure under different clamping force loads and the positioning position constraints of the tooling locator is obtained, and the mechanical model between the clamping force / clamping position and the internal stress of the composite thin-walled structure is established; S53: During the clamping process, according to the real-time data provided by the six-dimensional force sensor and assembly posture measurement, the simulation model and parameters are corrected by comparing with the finite element model, and the clamping force load and positioning position are adjusted in time to accurately control the assembly stress and geometric gap elimination effect inside the composite thin-walled structure to meet the design requirements.

2. The method for reducing assembly geometric gap according to claim 1, characterized in that: The S1 specifically includes: S11: Based on the overall structural characteristics of the composite thin-walled structure, the surface of the composite thin-walled structure with curvature is 3D scanned and measured for digital processing to obtain its complex surface features and identify key points that can represent the geometric features of the complex surface of the composite thin-walled structure in the spatial coordinate system; S12: Among the key points that can represent the complex curved surface features of the composite thin-walled structure, the parts that must be positioned and clamped on the composite thin-walled structure, and the areas where the strength and stiffness of the composite thin-walled structure meet the preset assembly quality conditions are selected as the initial positioning and clamping points; S13: Combined with the actual stress conditions and working conditions of the composite thin-walled structure, mechanical simulation software is used to simulate the stress distribution and deformation of the weak rigid workpiece during the clamping process, and the clamping scheme is optimized. After the selection of clamping points meets both the physical properties of the composite thin-walled structure and the actual engineering needs, a clamping area that can represent the complex curved surface features of the workpiece and has a stiffness that meets the preset requirements and has less influence on the deformation of the workpiece than the preset requirements is selected as the subsequent high-stability clamping point.

3. The method for reducing assembly geometric gap according to claim 1, characterized in that: The S3 specifically includes: S31: According to the error range of the tooling locator, the position errors of each clamping point before and after the composite thin-walled structure is clamped are randomly assigned to determine the initial position deviation of each positioning clamping point; S32: Conduct static clamping experiments to record the deformation and stress distribution data of the composite thin-walled structure under different clamping schemes; S33: Perform a dynamic clamping experiment, record the relationship data between the composite thin-walled structure and the deformation of the composite thin-walled structure at different positioner adjustment amounts, obtain the correlation coefficient between the positioner adjustment amount and the deformation of the composite thin-walled structure, and determine the key factors that affect the distribution of assembly geometric posture deviation; S34: Parameter values ​​are obtained experimentally through changes in material properties, thickness changes of composite thin-wall structures, and changes in clamping results corresponding to thermal expansion coefficients, and the parameter values ​​are integrated into the recorded data to establish an assembly geometry posture correction model.

4. The method for reducing assembly geometric gap according to claim 1, characterized in that: The three-dimensional measurement tools in S41 include but are not limited to high-precision three-dimensional coordinate measuring machines, laser trackers and laser scanners.

5. The method for reducing assembly geometric gap according to claim 1, characterized in that: The mechanical simulation analysis process of the composite thin-walled structure in S52 includes: assigning material, ply, and mechanical property parameters of assembly components in the finite element software ABAQUS, defining process constraints in combination with actual assembly conditions, establishing a finite element simulation model of the composite assembly process based on cohesive force units, and accurately characterizing assembly internal stresses; using ABAQUS secondary development to write in classic damage criteria for composite laminates, evaluating the stress level state during forced assembly, and accurately characterizing the failure safety margin of microscopic damage forms through damage indexes.

6. The method for reducing assembly geometric gap according to claim 1, characterized in that: The S6 specifically includes: S61: Re-measure the actual positions of each key part and clamping point of the composite thin-wall structure, compare them with the ideal position on the design digital model, and check whether they meet the preset tolerance range; S62: Check the bonding surfaces between the composite thin-wall structures to see if there is any warping or deformation caused by excessive extrusion, and ensure that the assembly geometric clearance meets the design requirements and complies with the preset elimination results of the assembly geometric clearance; S63: Use strain gauges and ultrasonic methods to monitor the stress and damage distribution inside the composite thin-walled structure, verify whether there is local stress higher than the preset value and local damage, and evaluate whether the mechanical properties of the overall structure meet the standards.

7. A geometric gap reduction system for assembling thin-walled composite aviation structures, used in the forced positioning and clamping process of thin-walled composite aviation structures, characterized in that: The assembly geometry clearance reduction system comprises: High-stability clamping point determination module, used for 3D scanning and mechanical simulation modeling of aviation composite thin-walled structures, selecting key positioning features of complex surfaces, and determining high-stability clamping points; Positioning adjustment modeling module, which is used to establish the correlation model between the flexible adjustment amount of composite thin-walled structures and the key assembly posture deviation based on high-stability clamping points; Specifically include: Determine the relative position relationship between each selected clamping point on the composite key and the center coordinate system of the tooling locator; The actual coordinate data of the clamping point is obtained through 3D measurement technology, and compared with the ideal coordinates on the design digital model to obtain the actual position deviation of each clamping point; Based on the actual position deviation data, the error model between the actual position of each clamping point and the ideal target position is established; Using a deterministic positioning algorithm, the position error of the clamping point is further converted into a mathematical model between the flexible adjustment amount of the tooling locator and the theoretical assembly posture of the weakly rigid composite thin-walled workpiece. The positioning adjustment correction module is used to obtain high-precision parameter values ​​of the correlation model through dynamic and static simulation tests of multiple factors, correct the correlation model, and obtain the posture deviation correction model; The posture deviation correction model solving module is used to solve the posture deviation correction model by using an iterative algorithm and experimental measurement to reduce the geometric clearance of the mating surface; Specifically include: Conduct three-dimensional measurement of the key clamping points before and after the clamping of the composite thin-walled structure, and record the initial position deviation of each positioning clamping point; A numerical iterative algorithm is used to solve the assembly geometric posture correction model. During the iteration process, for the clamping point, the adjustment amount of the locator is updated according to the current actual position deviation and the ideal target position, and the locator is adjusted in the corresponding amplitude and direction. After the adjustment is performed, the geometric clearance between the assembly mating surfaces is remeasured and the new posture deviation is calculated until the position deviation of all clamping points meets the set accuracy requirements or reaches the preset maximum number of iterations; The assembly gap and stress coordinated control module is used to control the assembly stress and geometric gap inside the composite thin-walled structure through the coordinated flexible adjustment of the clamping force load and the positioning position constraint based on force sensing data feedback and finite element stress analysis; Specifically include: Equipped with high-precision six-dimensional force sensors at the tooling positioning and clamping points, real-time monitoring and feedback of the magnitude of the force during the actual forced positioning and clamping process, and refined management of the force control adjustment during the assembly process; With the help of finite element analysis, through the coordinated flexible adjustment of clamping force load and positioning position constraint, the internal stress distribution of the composite thin-walled structure under different clamping force loads and tooling locator positioning position constraints is obtained, and the mechanical model between the clamping force / clamping position and the internal stress of the composite thin-walled structure is established; During the clamping process, according to the real-time data provided by the six-dimensional force sensor and assembly posture measurement, the simulation model and parameters are corrected by comparing with the finite element model, and the clamping force load and positioning position are adjusted in time to accurately control the assembly stress and geometric gap elimination effect inside the composite thin-walled structure to meet the design requirements; The measurement and evaluation module is used to measure assembly posture, gaps, key tolerances and internal stresses between components to determine whether the assembly accuracy and internal stress indicators of the composite thin-walled structure meet the preset requirements.

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