| In optical systems, the aspheric optics has incomparable advantages of sphere parts. Therefore, its applications are more and more widely. At the same time, more and more demands on the surface quality and contour accuracy of aspheric optics are proposed, and the required size is also growing. However, compared with sphere optics, the aspheric optics, especially the large-scale aspheric optics has mach more difficulties in machining, testing etc. Therefore, the ultra-precision machining of aspheric optics receives more and more attentions around the world. All countries are committing to the ultra-precision machining technology of aspheric surface.There is still a big gap compared with foreign countries in the overall performance, integrated precision index, reliability, stability and human design etc. Now in domestic, the polishing method is mainly adopted for machining of large aspheric optics, which is finished through continuous testing and repeated repair finishing, cannot meet the application requirements. Thus, according to the current manufacturing level, it's imminent to break through the traditional processing techniques, develop new ultra-precision machining methods and machining equipments.This thesis studied a novel ultra-precision turning method and machine tool, realized the efficient ultra-precision machining of axisymmetric aspheric metal reflector in sub-micron accuracy.First, a novel ultra-precision turning method is proposed in this thesis. Its processing principle is analyzed theoretically. The space geometric error model is established for the ultra-precision machine tool based on this new method. Permitted error value is determined under the premise of scheduled accuracy, to lay a theoretical foundation for further work.A novel micro-feeding mechanism driven by piezoelectric ceramics is proposed and designed in this thesis. Compared with the traditional dual-parallel flexible hinge, it has a higher consistency of stiffness in different directions of the axis vertical plane, which is more relevant to the machine tool in this subject. The mathematical model is established, and the experimental method is applied to research the open-loop characteristics has a maximum 3.19% displacement rate in different directions under 20N load. Experimentally study the open loop properties of micro-feeding mechanism such as static stiffness, natural frequency and the movement resolution etc. The experimental results of static stiffness and the first order shape have 22.4% and 5.03% deviation with the simulated results. The models of hysteresis and creep characteristics are established. On the basis of these studies, open-loop compensation control experiments are carried out on the mechanism, by which the following accuracy is improved 77.4%.The overall structure of the pendulum feeding ultra-precision machine is designed and the key components are analyzed. When processed on this machine, the best fitting sphere of parabolic surface is determined, while the formula of radial asphericity is derived. The tool tip trajectory control method is also studied. On these bases, the overall structure of control system and the main functions of CNC software are designed.This thesis studies the error compensation machining method of aspheric surface, analyzes the process of static space geometry error compensation machining and surface residual form error direct compensation machining method separately. The form accuracy is improved by 28.8% and 69.7% through the above two compensation machining methods. |
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