Study On Key Technologies Of Digital Posture Alignment And Finish Machining System For Wings

Normally, aircraft wings are located and clamped through specialized fixtures during the process of finish machining after wing assembly. However, the traditional analog coordination based equipment has low levels of cost-efficiency, automation and flexibility, and it is also hard to satisfy the increasing demands on the multiple-mission and small-lot manufacture. Achieving digital coordination based finish machining approaches is one of trends of aeronautical manufacture development. This dissertation systematically studies several crucial issues on the posture alignment and finish machining of wings, such as the configuration of the Wing Digital Posture Alignment and Finish Machining System (WDPA&FMS), the selection of supporting points for wings, the range of Numerical Control Positioner(NCP) for the WDPA&FMS, the key parameters of Auxiliary Clamping Fixture (AGF)and the cutting parameters for wing components during the process of wing finish machining with different phase, such as supporting, positioning, clamping and machining. The major contents of this dissertation are listed as follows:The WDFMS with Positioning and Posture Alignment Mechanism (PPAM)based on three paralleled chains has been established to realize the digital finish machining for wings. Chapter two has presented the construction of WDPA&FMS and the principle of pose alignment, and has introduced the freedom of PPAM. The Jacobean matrix and error model of PPAM have been analyzed, and the workspaces of PPAM have been solved by using the grid search method, establishing a foundation for the further design of the WDPA&FMS.The PPAM is not only a device based on the parallel manipulator for pose alignment, but also a positioning and holding fixture for wings in manufacturing or assembly. In order to achieve a good dexterity, bearing capacity, stiffness performance and positioning stability of the PPAM, Chapter three has presented the characteristics and choosing principle for wing supporting points. The trend of performance indexes have been studied qualitatively when the coordinate of supporting points is ever-changing, providing the basis for the effective selection of the supporting points for wing aligned and positioned by PPAMs.The range and layout of NCPs should be correctly arranged in order to reduce cost and make one set of PPAM to fit the size of multi-series wings. Chapter four has calculated the range and layout that meet the alignment needs of one NCP corresponding to one supporting point of one wing. Then, the optimal range and layout of NCPs that fit the size of multi-series wings have been determined with the genetic algorithm to achieve preset optimization objects including the manufacturing efficiency and the material cost. Such a study provides the theoretical basis for the arrangement and dimensions design of the NCPs.Chapter five has designed and fabricated a novel ACF to improve the pose fixing stability of wings which supported by distributed points. Firstly, several technologies have been coMPared and adopted to realize the ACF, secondly the necessity of multi-small-size vacuum cups approach and the force of one vacuum cup under the operation condition have been analyzed, and then the key parameters of ACF have been determined with both theoretical calculation and experiments, finally the improvement degree of pose fixing stability has been analyzed to prove the feasibility of ACFs. As a result, ACFs improves the pose fixing stability and provides a new method to clamp wing components during digital fine machining.In order to validate the effect of the WDPA&FMS on the wing joints machining,Chapter six has calculated the natural frequencies of wing holding by or without ACFs with the finite element technology. The effect of fabrication force with different frequencies, quantities and directions on the vibration amplitude has been analyzed.Cutting parameters of the finish machining have been analized through experiments of joints boring and milling,and provide a reference for the finish machining process of the fabrication of wing joints.Finally, Chapter seven has concluded the entire work. Moreover, innovations and the future work of this dissertation are also discussed briefly.