| Assembly is one of the most important part in the aircraft manufacturing,the performance and quality of aircraft are totally determined by the assembly quality.The traditional rigid assembly tooling is difficult to meet the assembly requirements of current aircraft with multiple varieties,small batch and low cost.Flexible tooling has the characteristics of adjustable,detachable,low cost and reconfigurable,which can significantly improve the utilization of aircraft assembly tooling resources,so it has been widely used in the assembly process of the aircraft.Parallel mechanism has obvious advantages in stiffness,accuracy,static/dynamic characteristics and so on.More and more attention has been paid to the flexible tooling with parallel mechanism.The reconfigurable alignment pose system based on the parallel configuration is studied in this dissertation.Through the modular design of software and hardware and the research of key technologies,reconfiguration design of alignment pose system facing the change of aircraft products and process is realized,which improves the efficiency and quality of aircraft assembly.The main contribution of this dissertation can be concluded as following:(1)The framework of the hardware and software of reconfigurable alignment pose system for aircraft assembly based on parallel configuration is proposed.The reconfiguration method is used in the design of alignment pose system and the detail of the configurable alignment pose system is analyzed from three aspects: the basic environment,the key technology and the organizational form.On the basis,a clustering analysis method of typical components considering the characteristics of the parallel mechanism is presented.At last,the design and application of reconfigurable alignment pose system are given.(2)Kinematic modeling and nested solution of the parallel alignment pose system are proposed based on the self-similarity characteristics.According to the self-similarity of the topological structure of the alignment pose system,the unified kinematic model of the alignment pose system is constructed based on screw theory and the nested solution method is given.Based on the geometric rotation method,the mapping model of geometric error is established and the evaluation index which reflecting the characteristics of the alignment pose system is defined.Then,considering the absolute positioning accuracy of each parallel mechanism and the relative positioning accuracy between parallel mechanisms,the general calibration method of multi-parallel mechanism is proposed and the geometric errors are identified.(3)A mapping model of alignment pose system accuracy considering the coupling of flexibility error of parallel mechanism and flexibility error of the alignment pose object is proposed.The positioning accuracy model of the parallel mechanism is established by considering the equivalent flexible joints and clearance in the joints.Then,the whole positioning accuracy model is proposed by considering the elastic deformation of the panel caused by the gravity.On this basis,the positioning accuracy index for the assembly is proposed.The optimal trajectory optimization problem with multi-factors coupling is solved by discretization of redundant axis with combining the assembly process requirements of components and the redundant characteristics of the alignment pose system.(4)A two-stage force and positon hybrid control method of components alignment pose and joining assembly is proposed.In order to correct the deformation caused by the internal forces in the aircraft assembly,an assembly posture adjustment method based on force/position control is proposed.Based on screw theory,the mapping relationship between the force sensor measurement value and gravity and the internal force is established,then the dynamic compensation of gravity is calculated.Based on the hypothesis of local rigid body spring connected,the model of converting internal force to position compensation is constructed by a multiple linear regression method.Then,aiming at the problem of the force control in the process of the joining assembly,the contact state space model and state transition principle are analyzed.The adjustment strategy set is modeled and used in the force/positon hybrid control system.The application research is conducted based on the above research.The reconfigurable configuration method is analyzed from the hardware and software aspects of the adujusting system.The application cases of the key technologies proposed in this dissertation under the reconfigurable platform are given.The high assembly quality is obtained in the fuselage assembly of the large aircraft by using the methods proposed in this dissertation. |
