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Due to small production volume in aircraft industry, the available information of variation sources is often not enough to make assumptions on their probabilistic characteristics, especially in the stage of prototype manufacturing. To deal with the problem, an assembly variation modeling and analysis method based on the elasticity mechanics and int...
Contexts in source publication
Context 1
... this section, a simulant wing skeleton is used to demonstrate and verify the proposed assembly varia- tion analysis method based on the interval approach. During the assembly process of a wing box in aircraft manufacturing, rear spar, front spar and wing ribs are first constructed as a ladder structure called wing skele- ton using a gantry-based main assembly jig, which is shown in Figure 4. First, the rear and front spars are positioned on the jig and coordinated with each other. Second, the wing ribs are fastened to the rib posts dis- tributed on the rear and front spars. The locating schemes of the components of the wing skeleton are coincident with what generally used in compliant ...
Context 2
... this section, a simulant wing skeleton is used to demonstrate and verify the proposed assembly varia- tion analysis method based on the interval approach. During the assembly process of a wing box in aircraft manufacturing, rear spar, front spar and wing ribs are first constructed as a ladder structure called wing skele- ton using a gantry-based main assembly jig, which is shown in Figure 4. First, the rear and front spars are positioned on the jig and coordinated with each other. ...
Citations
... However, existing research employing machine learning methods often develops algorithms only for specific combinations of components, resulting in poor generality of datasets for other models. Moreover, these methods are sensitive to environmental factors, rendering many Assembly Geometric Error accuracy predicting algorithms ineffective if environmental changes occur during data collection [12][13][14]. ...
... The remaining values are filled with the overall mean 10%, which was obtained through testing, and the specific results are shown in Section 4.2. So, the prob_attention can be expressed as Equation (12). ...
Using optimal assembly relationships, companies can enhance product quality without significantly increasing production costs. However, predicting Assembly Geometric Errors presents a challenging real-world problem in the manufacturing domain. To address this challenge, this paper introduces a highly efficient Transformer-based neural network model known as Predicting Assembly Geometric Errors based on Transformer (PAGEformer). This model accurately captures long-range assembly relationships and predicts final assembly errors. The proposed model incorporates two unique features: firstly, an enhanced self-attention mechanism to more effectively handle long-range dependencies, and secondly, the generation of positional information regarding gaps and fillings to better capture assembly relationships. This paper collected actual assembly data for folding rudder blades for unmanned aerial vehicles and established a Mechanical Assembly Relationship Dataset (MARD) for a comparative study. To further illustrate PAGEformer performance, we conducted extensive testing on a large-scale dataset and performed ablation experiments. The experimental results demonstrated a 15.3% improvement in PAGEformer accuracy compared to ARIMA on the MARD. On the ETH, Weather, and ECL open datasets, PAGEformer accuracy increased by 15.17%, 17.17%, and 9.5%, respectively, compared to the mainstream neural network models.
... The key process of assembling aircraft fuselage panels, fuselage frames, bulkhead, primary control system, secondary control system, and engine nacelle is drilling and riveting [2]. Component assembly finishing refers to after the riveting process of the aircraft components assembly is completed and the final product structure is completely closed [3]. The aircraft component joint holes and surface finishing are processed based on the component shape in the drilling and riveting process. ...
The aircraft assembly process mainly refers to the drilling and riveting/joint process of the aircraft product/components. It's necessary to assemble the aircraft with high accuracy to ensure the safety of the aerospace vehicle. In this research, factor affecting aircraft assembly accuracy is discussed. And the efficient process is demonstrated to improve the aircraft component's assembly accuracy based on experts' knowledge information. At first, the assembly accuracy requirements of different aircraft components assembly are provided. According to the required accuracy of aircraft assembly, finishing the drilling and riveting/joint operation is not easy at all. Because various factors affect the aircraft components assembly and manufacture processes, such as the transmission dimension and geometry errors. The accumulation of transmission errors will cause multiple inconsistencies. These inconsistencies are ultimately manifested as component shapes inconsistencies and component joint inconsistencies. This article carries out the precaution, awareness, and effective process of the aircraft component adjustment in the jig to avoid surface failure due to excessive clamping force, drilling, and riveting process. Then summarizes the aircraft components adjustment, clamping, drilling, and riveting processing methods during aircraft components assembly and manufacturing. Finally, these methods have been applied in aircraft parts assembly, which represents an efficient assembly finishing of the aircraft components.
... Indeed, three main factors act on the spot position, such as parts geometrical deviations, positioning variations of components to be assembled and tooling errors. In the aeronautical industry, Mei et al. 14 presented a method for the variation modeling and analysis in the case of compliant structures' assemblies. The dimensional variation sources of the assembly parts are represented with interval structural parameters. ...
... The approaches proposed in Refs. [11][12][13][14][15][16][17][18][19][20][21][22] overcome the limitations of the above tolerancing methods by taking into account the deformations of non-rigid components. Most of these methods [11][12][13][14] can be applied just in the case of sheets metal assemblies and are not valid for thick parts. ...
... [11][12][13][14][15][16][17][18][19][20][21][22] overcome the limitations of the above tolerancing methods by taking into account the deformations of non-rigid components. Most of these methods [11][12][13][14] can be applied just in the case of sheets metal assemblies and are not valid for thick parts. The rest of models [15][16][17][18][19][20][21][22] are focused on the use of mathematical formulations, statistical tools and the FE computations without a realistic geometric modeling of assembly components on the CAD software. ...
During the design stage, the ideal simulation and visualization of the mechanical assemblies behavior require the modeling of parts with dimensional and geometrical defects. However, the deviations caused by parts deformations can generate an important difference between the ideal assembly and the real product. In this regard, this paper proposes a tolerance analysis method of CAD assemblies considering non-rigid joints between parts with defects. The determination of realistic rigid components with dimensional and geometrical defects is based on the worst case tolerancing approach and the Small Displacement Torsor (SDT) parameters. The Finite Element (FE) computation is executed to determine deformations of realistic non-rigid part models under external loads. Sub-algorithms to define non-rigid joints between realistic parts are developed. The tolerance analysis is established using the realistic CAD assembly. A case study is presented to evaluate the proposed model.
... Camelio et al. 3 combined the principal component analysis and MIC to consider the geometric covariance of variation sources. Mei et al. 4 proposed the assembly variation analysis method based on MIC and the interval approach. Moreover, Xing and Wang 5 put forward a power balance method to obtain a higher calculation accuracy for the deviation of assembly. ...
The deviation vector at arbitrary location of large thin-walled structure caused by manufacturing process is different and has the characteristic of field distribution, which has great influence on the assemble quality. The deviation of each point on the part is not independent, and the final assembly deviation is difficult to be controlled. In this paper, the deviation field of large thin-walled structure is described by the linear combination of a series of basic deviation patterns. The deviation propagation model is established to quantify the contribution of basic deviation patterns between parts and assembly. A new two-step optimization method based on the adjustment of key control points of the part is proposed for the deviation control of large thin-walled structures. Firstly, the effective independent method is employed to obtain the optimal measurement points, which may characterize all basic deviation patterns of the part accurately. Then a new optimization model is developed to determine the key control points for special basic deviation pattern, which have little influence on the other basic deviation patterns. Based on the genetic optimization algorithm, the optimal key control points and the adjusted quantities for special basic deviation pattern are obtained, simultaneously. A case study on the assembly process of two cylindrical thin-walled parts with initial deviations measured by the Laser Scan Device is conducted. The basic deviation pattern with great influence on the deviation of assembly is determined firstly. The key control points and the corresponding adjusted quantities for this basic deviation pattern are calculated. The results indicate that the deviation of the assembled structure may be suppressed by the adjusted deformation of the key control points of parts. It is useful on the deviation control for the assembly process of large thin-walled structures.
... On the other hand, the drilled rivet holes' pose errors are influenced by the preassembly variation of the aircraft structure, which can be ensured by assembly variation analysis and control [17][18][19], as well as accurate alignment of aircraft structures [20,21]. For example, McKenna et al. developed a novel variation propagation model for the overconstrained wing spar assembly, which contribute to the dimensional tolerance allocation [22]. ...
Modern aircraft assembly demands assembly cells or machines with higher machining efficiency and accuracy. Thus, a dual-machine drilling and riveting cell is developed in this paper. We firstly discuss its physical design, as well as the automatic drilling and riveting process. With the automatic drilling and riveting cell, drilling and riveting production line of aircraft panels can be expected. The frame chain of the drilling and riveting cell is constructed to link the assembly cell to its task space, which is the kinematics base. System calibrations, including task space calibration, the sensor calibration of an orientation alignment unit, the floating calibration of the implicit hand-eye relationship, are explored. For high positioning accuracy, a multi-sensor servoing method is proposed for cell positioning. An orientation-based laser servoing strategy, which uses the feedback of the orientation errors measured by laser displacement sensors, is used to align drilling direction and camera shooting direction. Besides, A single-camera-based visual servoing is applied to align the tool center point (TCP) to reference holes, to obtain their coordinates for drilling position modification. Experiments of multi-sensor servoing for cell positioning are performed on an automatic drilling and riveting machine developed for the panel assembly of an aircraft in China. With the cell positioning method, the automatic drilling and riveting cell can approximately achieve an accuracy of 0.05 mm, which can adequately fulfill the requirement for the assembly of the aircraft.
... Zhu et al. proposed a positioning error compensation method based on the two dimensional manifold to improve the efficiency of the error compensation for robots in aircraft industry [17]. For another, assembly variation analysis and control based on various theories [18][19][20], as well as accurate alignment of aircraft components [21,22], could be beneficial to mitigate the out-of-tolerance risk of the drilled fastener holes. However, the mutual coordination error inducing the position variation of fastener holes could be large, even if the equipment's positioning accuracy, assembly variation, and temperature filed are effectively controlled. ...
... In the field of mechanical assembly, manufacturing and locating errors of parts and fixtures could cause an assembly to be in erroneous shape and pose. To associate assembly variations of the key characteristics (KCs) with various variation sources, a mathematical function, i.e., an assembly variation model, is built for the assembly [18,19]. This process is treated as assembly variation modeling. ...
Tight position tolerance is required for fastener holes in wing manufacturing. Automated drilling system with high positioning accuracy is the key to achieve the requirement. The paper seeks to determine allowable values of variation sources and guarantee the hole position tolerance. The process of reference hole positioning and the compensation of drilling positions are firstly explored and formalized for an automated drilling system integrated with an industrial camera. Based on this, a positioning variation model for automated drilling considering positioning error measurement and compensation is built. After that, positioning variation synthesis being imposed engineering constraints on is mathematically modeled based on the theory of mathematical statistics. In the positioning variation synthesis, imperfect camera installation, nonideal measurement conditions, equipment positioning error, etc. are included. The positioning variation model and involving synthesis strategy have been used to develop an automated drilling system for wing assembly. Experiments conducted on the developed drilling system show that the fastener holes’ desired position tolerance 0.3 mm will not be exceeded, which is a necessary condition of the satisfactory drilling quality of the aircraft wing.
... As a significant influential factor of assembly accuracy, 1 assembly deviation has been paid more attention to so as to analyze the performance of product. 2,3 For instance, Wang et al. 4 established an assembly deformation prediction model and a variation propagation model to predict the assembly variation of aircraft panels, which creates an analytical foundation on variation control and tolerance optimization. And Cai et al. 5 proposed a unified variation modeling method considering both rigid and compliant variations to verify the geometric and dimensional requirements of parts. ...
Performance of mechanical product is highly influenced by assembly deviation. Due to manufacturing errors, the real part surface is machined with morphology deviations, which would cause mating surface deviating from ideal position in assembly behavior, consequently leading to assembly deviation. Meanwhile, the random variation of relative position and orientation between two non-ideal parts also affects the assembly deviation. To efficiently obtain the maximum assembly deviation considering the comprehensive influence of two factors above for circumferential grinding plane, an assembly deviation calculation method based on surface deviation modeling is proposed in this paper. In this method, morphology deviations models of part surfaces are firstly established from the deviation function. The randomness of two factors are represented by a multivariate group with randomness containing deviation function coefficients and three deflected parameters. Then based on surface deviation modeling method, differential evolution algorithm is applied to search the maximum assembly deviation, which involves the construction of fitness function by implementing optimized progressive contact method and iterative operations of mutation, crossover and selection. Finally, the effectiveness of this method is illustrated by an assembly in the end.
... In Wärmefjord et al. (2008), the authors used the MIC approach in conjunction with a direct contact point location algorithm. MIC was also used for wing skeleton variation analysis in Mei et al. (2018). ...
Purpose
The authors consider the problem of optimizing temporary fastener patterns in aircraft assembly. Minimizing the number of fasteners while maintaining final product quality is one of the key enablers for intensifying production in the aerospace industry. The purpose of this study is to formulate the fastener pattern optimization problem and compare different solving approaches on both test benchmarks and rear wing-to-fuselage assembly of an Airbus A350-900.
Design/methodology/approach
The first considered algorithm is based on a local exhaustive search. It is proved to be efficient and reliable but requires much computational effort. Secondly, the Mesh Adaptive Direct Search (MADS) implemented in NOMAD software (Nonlinear Optimization by Mesh Adaptive Direct Search) is used to apply the powerful mathematical machinery of surrogate modeling and associated optimization strategy. In addition, another popular optimization algorithm called simulated annealing (SA) was implemented. Since a single fastener pattern must be used for the entire aircraft series, cross-validation of obtained results was applied. The available measured initial gaps from 340 different aircraft of the A350-900 series were used.
Findings
The results indicated that SA cannot be applicable as its random character does not provide repeatable results and requires tens of runs for any optimization analysis. Both local variations (LV) method and MADS have proved to be appropriate as they improved the existing fastener pattern for all available gaps. The modification of the MADS' search step was performed to exploit all the information the authors have about the problem.
Originality/value
The paper presents deterministic and probabilistic optimization problem formulations and considers three different approaches for their solution. The existing fastener pattern was improved.
... At present, the research on the complexity in assembly manufacturing system mainly focuses on structure complexity, process complexity, and control complexity [5][6][7][8][9], as Figure 1 shows. Many scholars have done considerable work on assembly system. ...
... At present, the research on the complexity in assembly manufacturing system mainly focuses on structure complexity, process complexity, and control complexity [6][7][8][9][10], as Figure 1 shows. Many scholars have done considerable work on assembly system. ...
In the past decade years, much attention has been attached on assembly process reliability in manufacturing system, because the quality and cost of product are highly determined by assembly process. However, existing research on reliability in assembly are mainly focused on study of size deviation propagation. In this paper, the method for risk evaluation in assembly process based on the discrete-time SIRS epidemic model and information entropy was proposed. Firstly, aiming at the issue of assembly process optimization, innovative solutions are proposed from the perspectives of reliability and cost by decomposing the assembly into general path and rework path. Secondly, the propagation mechanism of defects in optimal assembly approach were studied through combining the infectious disease model and information entropy. According to the bifurcation phenomenon in the SIRS model, the entropy increment of assembly process Δ H b a s e when defect emergence occurs is calculated. Thirdly, the information entropy increment of optimal assembly approach Δ H is used to evaluate the assembly risk by comparing with the Δ H b a s e . Finally, a case study of assembly risk evaluation for the oil pump was presented to verify the advantage of this method.
... There are a number of key challenges associated with variation, such as the large number of potential variation sources, disparate variation magnitudes, the stochastic nature of variation occurrence, and a lack of knowledge of variation propagation mechanisms [17,18]. The most recent research in the area of variation propagation has developed physics-driven variation models [19] and compliance-induced variation models [20][21][22]. To date, most assembly variation models have focused on the connective assembly relationships between parts. ...
Overconstrained assemblies such as aircraft sub-assemblies present a challenge to production planners, as variations in parts and processes can make it difficult to achieve all assembly Key Characteristics (KCs) simultaneously. Despite assigning tight tolerances to sub-component manufacture, part variation propagation necessitates expensive and time-consuming variation management processes such as shimming in order to ensure the final assembly is within specification. This paper presents for the first time a variation propagation model for overconstrained assemblies, and develops a novel modelling method to connect variations with production costs. This facilitates a novel process optimisation method based on variation propagation, with the ability to analyse the trade-offs between the cost and achievable variation limits of the entire manufacturing chain in order to minimise the overall manufacturing cost. An overconstrained wing spar assembly is used as a case study to validate the methodology.
