Study On The Position-following Technique In Aircraft Digital Assembly System

Modularization is a very common mode in the production of aircrafts. Firstly, parts and subassemblies are joined into large components. Then, large components are joined into the whole aircraft. During the process of aircraft digital assembly, it is important to choose the way to support subassemblies and large components. Considering their positions and postures are supposed to be adjusted, we usually employ a unit of several three coordinate numerical control localizers to support them. Several so-called ball-heads are fixed to the subassemblies or large components, and a so-called ball-socket is installed on the top of each localizer, each ball-head and the corresponding ball-socket form a ball joint. However, how to obtain an accurate support for subassemblies and components by ball joint, namely to make the ball-head and the ball-socket be concentric is a key problem. This dissertation summarizes and compares several position ensuring techniques based on the project experiences of my laboratory team. The position-following method is especially introduced to solve the problem mentioned above, and a corresponding position-following device is designed to fulfill the method.In Chapter 1, the research and application status of aircraft digital assembly at home and abroad are introduced firstly, and then several position ensuring techniques are summarized. In the end of this chapter the background and overall framework of this dissertation are given.In Chapter 2, the layout of localizers which support the subassemblies or large components is introduced firstly, then, The principle of position and posture adjustment of subassemblies or large components, requirements of ball-heads' position and posture are proposed, and then the position-following method is described, finally the requirements of position-following device are made clear.In Chapter 3, a kind of position-following device is particularly designed, The designed device is divided into four modules which are the linear motion module, the locking module, the position feedback module and the ball-head supporting module. Each module is designed in detail and finally a whole position-following device is come into being.In Chapter 4, the ball-head supporting module is discussed emphatically. The structure of the module is presented. The working principle and three working patterns are explained. The transmission rate from the servomotor to the claws and the force supplied by the claws are calculated. The manufacture processes of key parts such as claws, ball-heads and ball-sockets are discussed finally.In Chapter 5, the stress or stiffness check of key parts which suffered large forces such as the blocks, the corresponding bolts, the ball-heads and ball-sockets is established.In the final chapter, summary for the whole work is given, and the future work is expected.