Study On Modeling And Simulation Of Alignment Pose Process Of Aircraft Component

Aircraft assembly is one of the most important and complicated part of aircraft manufacturing. The final performance and quality of aircraft depend on aircraft assembly. In the process of the assembly, the accuracy of pose of component or subassembly directly affects the aerodynamic shape, fatigue life and reliability of aircraft, which is a common and key issue in aircraft assembly. To improve the quality and efficiency of pose alignment, digital, automatous and flexible technologies are introduced. The research object in this dissertation is the digital alignment pose system which consists of an aircraft component and several three coordinate numerical control positioners. Several crucial technology issues on modeling and simulation of alignment process, such as the inverse kinematics, workspace, flexibly multi-body dynamic and kinematic modeling and simulation, simulation of alignment process with non-ideal kinematic joints and wearing modeling are studied and analyzed deeply.The development of aircraft assembly technology and key techniques of modern aircraft digital flexible assembly are introduced. Then, the development, current situation and the application of modeling and simulation in aircraft assembly are presented.The alignment principle of alignment pose system is described. The advantage and disadvantage of several structures of alignment pose systems are discussed. A trajectory planing method based on the inverse kinematics of alignment pose mechanism is proposed. The workspace problem of alignment pose mechanism is solved by utilizing forward kinematics and grid search method. The integration of hardware and software of digital alignment pose system is presented.The flexible multi-body dynamic model of alignment pose mechanism is constructed. In terms of the characteristic of alignment pose mechanism, the supporting poles of positioners are considered to be flexible for simulation, and the dynamic model of alignment pose mechanism is established by utilizing Lagrange equation, virtual work theory and Lagrange multipliers method. Then, the joint reaction forces of aircraft component and supporting poles are acquired by solving dynamic equation numerically.The kinematic and dynamic models of two typical types of non-ideal spherical joints are developed. Firstly, two normal force model of spherical joint with hemi-spherical and spherical segment sockets are constructed based on Hertz contact theory and volumetric contact model, respectively. Secondly, the dynamic models of two types of spherical joints are derived form the normal force model, which are combined with modified Coulomb friction law. Finally, simulations of alignment pose mechanism are carried out for typical moving trajectories. The influences of moving trajectory, friction, clearance and structure of spherical joint on the performance of mechanism are analyzed. The simulation results are also applicable to similar mechanism design, moving trajectory planning and kinematic joint wear forecasting.Wear model of the two types of spherical joints are developed. Firstly, the contact forces and positions of contact points are obtained by utilizing the dynamic models of non-ideal spherical joints proposed previously. Secondly, the Archard’s equation is employed to model the wear of balls and sockets. To acquire the distribution of wear depth, the surfaces on the ball and socket are discretized for calculating and storing wear depth. Hertz contact theory and volumetric contact model are used to obtain the distribution of contact force in the two wearing models, respectively. Finally, process simulation of alignment mechanism with four positioners is carried out. This wear model is able to be applicable for life prediction and mechanical design of alignment mechanism.The whole work in this dissertation is summarized, and the future work is discussed.