Study On Technologies For Controlling And Correcting Large Aircraft Panel Assembly Deformation

Aircraft assembly, which is one of the most important and complicated parts of aircraft manufacturing, determines the final performance, quality and service life of aircraft, while in the aircraft assembly process, the aircraft panel is one of the major components, whose assembly accuracy has a direct influence on the coordinations between component parts and the shape accuracy of the whole part. How to control the panel assembly deformation effectively is one of the key technical difficulties which the aviation enterprises are facing now. For the purpose of controlling aircraft panel effectively and presenting a practicably integral solution, this dissertation carries out in-depth study and analysis on several crucial issues such as the support layout for fuselage panels, the placement of measurement points and the prediction and correction of panel deformation. The main research work is as follows:The research background and significance of this dissertation are expatiated, and the domestic and foreign development states of aircraft digital assembly techniques are also introduced and summarized. Then, the development, current situation and the application of controlling and correcting large aircraft panel deformation are presented, which imply that the technology for controlling and correcting panel deformation is one of the difficult and important problems in aircraft digital assembly.To improve and enhance the panel stiffness in digital assembly, a method for optimizing the multi load-transmitting device (LTD) based discrete support layout is presented. By constructing finite element (FE) models of the fuselage panel and LTDs, the panel’s strain energy under different support layout parameters is obtained according to the principle of the mixed uniform design (MUD). Using the partial least squares regression (PLSR) method, the mathematical relationship between the strain energy and the support layout parameters is established, which is then used to obtain the optimum multi LTD based support layout. Furthermore, the panel deformation under the optimum multi LTD based support is compared with that under the full-scale shape-preserving bracket (FSSPB) based support.Since the posture of an aircraft panel is commonly evaluated by matching the theoretical and actual positions of the measurement points placed on it, and its assembly deformation is also represented by the position errors of the measurement points, a reasonable measurement point placement is significant for the aircraft panel in digital assembly. A method based on the D-optimality method and the adaptive simulated annealing genetic algorithm (ASAGA) is proposed to optimize the placement of the measurement points which can cover more deformation information of the panel for effective assembly error diagnosis. By taking the principle of the D-optimality method, an optimal set of measurement points are selected from a larger candidate set through the ASAGA.The deformation of a large fuselage panel is unavoidable due to its weak-stiffness and low-rigidity. Sometimes the assembly accuracy of the panel is out of tolerance. A method is proposed to predict and correct the panel deformation during digital assembly by using a finite element analysis (FEA) and PLSR method. An FE model is established to investigate the panel deformation behavior firstly, and by orthogonal simulations, the position error data of measurement points representing the precision of the panel is obtained. Then a mathematical model of the relationship between the position errors of measurement points on the panel and the displacements of numerical control positioners is developed based on the PLSR method, which can be used to predict and correct the panel deformation effectively.In order to verify the correctness and validity of the methods such as the support layout for fuselage panels and the prediction and correction of panel deformation, a corresponding testing system for aircraft panel positioning and alignment is designed and built, then based on this system, a series of experiments are arranged to analyze and compare the theoretical and experimental data, thereby validating the reliability of related methods.Finally, the whole work described in this dissertation is summarized, and the future work is also discussed.