Search results

The introduction of automation for the assembly of aircraft wing box structures will require individual components to conform closely to the CAD design specification with regard to shape geometry and dimensional tolerances. Often, due to a variety of previous manufacturing processes, the 3D shape of these large components lose the accuracy of their designed dimensional specifications. Under these circumstances part‐to‐part assembly becomes tedious and it would be impossible to rely on robots to achieve precise assembly in an automated system. For this reason, variations need to be accurately quantified in order to provide a reliable prediction model in aid of any future automated assembly. This paper describes the measurement method used to record the possible variations occurring during the assembly process. The measurements were made using a laser tracker where the results are expected to offer some explanations as to the causes of the variation. The suitability of a laser tracker in a large assembly jig environment is then assessed. This study is based on the work that was carried out at BAE Systems UK, where the Airbus commercial aircraft wings are manufactured.

This paper results from research carried out to survey the various large commercial aerospace engineering component measurement systems. The commercial aircraft manufacturing industry is special due to the size of the components involved. Accuracy constraints remain very close, despite the size, and therefore accurate methods of measurement are necessary to control the quality of the final product. A survey of various current methods of measurement for such components is presented. These methods are based around three main principles: theodolites, photogrammetry, and laser technology. Each method has its own advantages and disadvantages in terms of accuracy, repeatability, range and cost. It is also often necessary to consider what each technique provides in terms of data storage and analysis. Most techniques use computer‐based systems to store results and perform various calculations. These systems also have their own requirements in terms of the environment in which they are used. It is important to consider whether a particular system can be installed in an area suitable to measure the required component, as well as ensuring that the stability requirements are met. In this paper the principles and characteristics of conventional optical tooling, electronic triangulation, electronic trilateration, photogrammetry, laser trackers, and laser scanners are reviewed.

This paper aims to present a method for predicting dimensional variation in assembly processes of a wingbox structure concentrating on the assembly of skin panels to rib feet.

Finite element modelling and experimental tests are conducted on the rib structure based on the site measurement gathered from the Airbus assembly factory.

The results have shown that the simulated model has the capability of predicting to an acceptable degree of accuracy the overall geometrical variations of the ribs and skin panels, as well as the positional variations of each individual rib foot.

The authors believe that no previous research has offered a similar prediction method for large aerostructures.

The purpose of this paper is to propose a method to identify sources of variation in horizontal stabilizer assembly using FEA (finite element analysis) and PCA (principal component analysis).

The horizontal stabilizer is assembled by long and thin‐walled deformable aluminum components. Part‐to‐part assembly of these compliant components regularly causes difficulties associated with dimensional variations. Finite element modeling and PCA are employed to predict the propagation of variation from edge to horizontal stabilizer.

The variation analysis combined with pattern fitting method is demonstrated in a case study of the horizontal stabilizer assembly system and good performance is obtained. The results have shown that the FEA and PCA method has the capability of predicting, to an acceptable degree of accuracy, the overall geometrical variations propagation of the edges and trailing edge.

The results of this research will enhance the understanding of the compliant components deformation in assembly, and help to systematically improve the precision control efficiency in civil aircraft assembly.

Flexible materials are used extensively in a wide range of industrial applications including the manufacture and assembly of garment and footwear products, the packaging industry and aircraft manufacturing. These applications are often extremely labour intensive requiring fast and accurate manipulation of materials by skilled human operators. This has resulted in numerous international research and development efforts to automate certain handling and manipulation processes involving flexible materials. Much of the research has been inspired by real industrial problems, and thus has been mainly sponsored by industry. A variety of innovative techniques and methods have emerged either addressing specific industrial problems, or suggesting a number of generic solutions. This paper closely examines the international research effort of automatic manipulation of flexible materials through a classification of workpieces in terms of their broad geometric shape, industrial applications, and individual processes.

Tolerance simulation’s reliability depends on the concordance between the input probability distribution and the real variation. The prescribed clamp force introduced changes in parts’ variation, which should be reflected in the input probability distribution for the tolerance simulation. The paper aims to present a tolerance analysis process of the composite wingbox assembly considering the preloading-modified distribution and especially focuses on the spring-in deviation of the thin-walled C-section composite beam (TC2B).

Based on finite element analysis model of TC2B, the preloading-modified probability distribution function (PDF) of the spring-in deviation is obtained. Thickness variations of the TC2B are obtained from the data of the downscaled composite wingbox. These variations are input to the computer-aided tolerance tools, and the final assembly variations are obtained. The assembly of the downscaled wingbox illustrates the effect of preloading on the probability distribution of the spring-in deviation.

The results have shown that the final assembly variations estimated with the modified probability distribution is more reliable than the variation of the initial normal distribution.

The tolerance simulation work presented in the paper will enhance the understanding of the composite parts assembling with spring-in deviations, improve the chance to choose assembling processes that allow specifications to be met and help with tolerance allocation in composites assembly.

The purpose of this study is to design and optimize copper indium gallium selenide (CIGS) thin film solar cells.

A novel bi-layer CIGS thin film solar cell based on SnS is designed. To improve the performance of the CIGS based thin film solar cell a tin sulfide (SnS) layer is added to the structure, as back surface field and second absorbing layer. Defect recombination centers have a significant effect on the performance of CIGS solar cells by changing recombination rate and charge density. Therefore, performance of the proposed structure is investigated in two stages successively, considering typical and maximum reported trap density for both CIGS and SnS. To achieve valid results, the authors use previously reported experimental parameters in the simulations.

First by considering the typical reported trap density for both SnS and CIGS, high efficiency of 36%, was obtained. Afterward maximum reported trap densities of 1 × 10¹⁹ and 5.6 × 10¹⁵cm⁻³ were considered for SnS and CIGS, respectively. The efficiency of the optimized cell is 27.17% which is achieved in CIGS and SnS thicknesses of cell are 0.3 and 0.1 µm, respectively. Therefore, even in this case, the obtained efficiency is well greater than previous structures while the absorbing layer thickness is low.

Having results similar to practical CIGS solar cells, the impact of the defects of SnS and CIGS layers was investigated. It was found that affixing SnS between CIGS and Mo layers causes a significant improvement in the efficiency of CIGS thin-film solar cell.

In aircraft wing–fuselage assembly, the distributed multi-point support layout of positioners causes fuselage to deform under gravity load, leading to assembly difficulty and assembly stress. This paper aims to propose a hybrid force position control method to balance aerodynamic shape accuracy and deformation of assembly area, thereby correcting assembly deformation and reducing assembly stress.

Force and position control axes of positioners are selected based on screw theory and ellipsoid method. The position-control axes follow the posture trajectory to align the fuselage posture. To exert force on the fuselage and correct the deformations, the force-control axes follow the contact force derived by using orthogonal experiments and partial least squares regression (PLSR). Finite element simulation and one-dimension deformation correction experiment are conducted to verify the validity of this method.

Simulation results indicate that hybrid force position control method can correct assembly deformation and improve the wing–fuselage assembly quality significantly. Experiment on specimen verifies the effect of this method indirectly.

The proposed method gives a solution to solve the deformation problem during aircraft wing-fuselage assembly, thereby reducing assembly stress and improving assembly quality.

The purpose of this paper is to identify control systems that give rise to better construction project performance; and develop and test project performance predictive models based on control systems adopted in the project.

Research design was questionnaire survey. Data were collected via Electronic mails. The sampling frame was Singapore-based construction firms.

In all, 16 control mechanisms are significantly correlated with project outcomes. The more important control mechanisms are: adequacy of project information to develop the project schedule; adequacy of float in the schedule; and quality of techniques used to support risk identification. Two relatively robust predictive models were constructed and validated to predict schedule and quality outcomes of construction projects. Schedule performance may be predicted by adequacy of float and stringency of criteria to select suppliers. Quality outcome is most significantly affected by competency of quality manager, rather than the hard systems adopted in the project.

The limitations include low response rate, and subjective nature of the five-point Likert scale used to rate project outcomes and extent to which control mechanisms were adopted in the project.

The implication of the findings is that merely having good project management practices and adequate resources are not sufficient to achieve good project outcomes. Instead, construction projects need to have control systems in place, as they play an important role in project outcomes.

The paper has shown empirically that control systems affect project outcomes. They are needed not just to control the project, but also help the project to achieve good outcomes. The research designed and tested two relatively robust models to predict schedule and quality outcomes of a project. These models may be used to make an initial assessment of the project's likely outcome, based on the control systems that contractors are going to adopt.

Current research topics in relation to health information searching focus on challenges faced by health consumers and domains used to perform the health search. Health consumers may not be capable of successfully searching for a health task due to limited medical knowledge. As such search assisting features provided on health domains are important in assisting health consumers during a search session. The purpose of this paper is to perform a preliminary exploratory research study to understand if search assisting features are visible to searchers and the usage of search assisting features when searching on a personal health task.

A convenience sampling method in a university setting and an observational type study was used. MedlinePlus is used as the search domain for this research study. While participants of this research study were first time users of MedlinePlus, they were not first time medical searchers.

Results of this research study indicate health consumers do not utilize search assisting features when searching for a personal health task. This is because health consumers are comfortable with their search skills. In other cases health consumers found the search assisting features irrelevant or had no confidence in the search assisting features presented. Key contributions of this research study indicate health consumers do not utilize search assisting features when searching for a personal health task. This is because health consumers are comfortable with their search skills. In other cases health consumers found the search assisting features irrelevant or had no confidence in the search assisting features presented.

Results of this research study has implications for health domain and human computer designers in relation to the development of specialized search assisting features and the placement of these features. Theoretical contributions indicate health searchers use search assisting features minimally when searching on a personal health task.

Results of this research study indicate health consumers do not utilize search assisting features when searching for a personal health task. This is because health consumers are comfortable with their search skills. In other cases health consumers found the search assisting features irrelevant or had no confidence in the search assisting features presented.