Yunbo Bi

Numerical study on predicting and correcting assembly deformation of a large fuselage panel during digital assembly

Purpose – 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. The purpose of this paper is to propose a method to predict and correct the assembly deformation of a large fuselage panel during digital assembly by using a finite element (FE) analysis and partial least squares regression (PLSR) method. Design/methodology/approach – A FE model is proposed to optimize the layout of load-transmitting devices to reduce panel deformation after the process of hoisting and supporting. Furthermore, another FE model is established to investigate the deformation behavior of the panel. By orthogonal simulations, the position error data of measurement points representing the precision of the panel are 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 me...

Optimal placement of measurement points on large aircraft fuselage panels in digital assembly

A large aircraft fuselage panel is commonly composed of a variety of thin-walled components. Most of these components are large, thin and compliant, and they are also prone to some flexible deformation during assembly and remain deformed after assembly. Besides, many different fabrication and assembly manners are adopted in order to guarantee the complicated assembly relationships between each component. The above characteristics often cause large aircraft fuselage panels to exhibit low stiffness and weak strength, thereby inducing deformation during assembly. Since the posture of a large aircraft fuselage 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 large aircraft fuselage panel in digital assembly. This article presents a method based on the D-optimality method and the adaptive simulated annealing genetic algorithm 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 is selected from a larger candidate set through adaptive simulated annealing genetic algorithm. As illustrated by an example, the final measurement point configuration is more effective to maximize the determinant of the corresponding Fisher Information Matrix and minimize the estimation error of the assembly deformation than those obtained by other methods.

Modeling of fast pre-joining processes optimization for skin-stringer panels

Purpose – The purpose of this paper is to propose a new model for optimizing pre-joining processes quickly and accurately, guiding workers to standardized operations. For the automatic riveting in panel assemblies, the traditional approach of determination of pre-joining processes entirely rests on the experience of workers, which leads to the improper number, location and sequence of pre-joining, the low quality stability and the high repair rate in most cases. Design/methodology/approach – The clearances computation with the complete finite element model for every process combination is time-consuming. Therefore a fast pre-joining processes optimization model (FPPOM) is proposed. This model treats both the measured initial clearances and the stiffness matrices of key points of panels as an input; considers the permissive clearances as an evaluation criterion; regards the optimal number, location and sequence as an objective; and takes the neighborhood-search-based adaptive genetic algorithm as a solutio...

Multi load-transmitting device based support layout optimization for large fuselage panels in digital assembly

A large fuselage panel is always connected to a full-scale shape-preserving bracket to enhance its stiffness in digital assembly processes and reduce assembly deformation induced by factors such as gravity. However, the full-scale shape-preserving bracket’s characteristics, such as large size and weight, usually result in a complex installation process and high maintenance costs. A method for optimizing a multi load-transmitting device based discrete support layout is presented in this paper. By constructing finite element model including the fuselage panel and LTDs, the panel’s strain energy under different support layout parameters is obtained according to the principle of mixed uniform design. Using the method of partial least squares regression, 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, by comparing the panel deformation under the optimum multi LTD based support with that under the full-scale shape-preserving bracket-based support, we conclude that the optimum multi LTD based support can not only suppress panel deformation effectively, but also keep the panel’s stiffness comparable to that under the full-scale shape-preserving bracket-based support.

A united kinematic calibration method for a dual-machine system

Purpose This paper aims to propose a united kinematic calibration method for a dual-machine system in automatic drilling and riveting. The method takes both absolute and relative pose accuracy into account, which will largely influence the machining accuracy of the dual-machine system and assembly quality. Design/methodology/approach A comprehensive kinematic model of the dual-machine system is established by the superposition of sub-models with pose constraints, which involves base frame parameters, kinematic parameters and tool frame parameters. Based on the kinematic model and the actual pose error data measured by a laser tracker, the parameters of coordinated machines are identified by the Levenberg–Marquardt method as a multi-objective nonlinear optimization problem. The identified parameters of the coordinated machines will be used in the control system. Findings A new calibration method for the dual-machine system is developed, including a comprehensive kinematic model and an efficient parameter identification method. The experiment results show that with the proposed method, the pose accuracy of the dual-machine system was remarkably improved, especially the relative position and orientation errors. Practical implications This method has been used in an aircraft assembly project. The calibrated dual-machine system shows a good performance on system coordination and machining accuracy. Originality/value This paper proposes a new method with high accuracy and efficiency for the dual-machine system calibration. The research can be extended to multi-machine and multi-robot fields to improve the system precision.