Structure Optimization And Control Of Large Area And High Precision Diffraction Grating Ruling Engine

The diffraction grating of large area and high precision is the core optical device of large observational instruments which are applied to various fields. Because of the characteristics of large size and high precision, the grating can only be manufactured by mechanical characterization. Since the high precision of the grating ruling machine is decided by such factors as mechanical structure and control technique, both of which are inseparable from each other, the core of the research of the grating ruling machine is to study the two factors. Thus, the crux of improving the manufacturing technology of the grating ruling machine is the research of its structure optimization theory and its control theory. With the developing of various large-scale astrophysics projects, the diffraction grating of large area and high precision needs higher manufacturing precision. The grating’s groove density and groove quality (straightness and shape of the groove) are directly determined by the positioning accuracy and the tip trajectory of grating ruling machine. Therefore, the main factors that influence the optical function of the grating are the positioning accuracy and the tip trajectory. This paper focuses on the structure optimization and the control of the two factors which influence the precision of the diffraction grating ruling machine-the scribing system and the indexing system.Because of the high precision, difficulty, long cycle and high cost of machining parts of the grating ruling machine and because it is impossible to repeatedly trial-produce prototype in the structure optimization process, the optimization design method based on the CAD/CAE integrated technology is adopted in the research of structure optimization of the grating machine. CAD parametric design method based on Parasolid and CAE technical characteristics are studied firstly. At the same time, CAD/CAE integrated technology and design patterns are studied. Based on the combination of these studies, an integrated CAD/CAE software framework system which has high development efficiency and strong portability and extendibility is put forward. In the meanwhile, based on CAD parametric modeling, the virtual prototype model of the grating machine is established to carry through CAE analysis and structure optimization, especially that of the scribing system and the indexing system. Besides, the grating kinematics simulation is conducted.The design and optimization of the grating ruling machine which is a typical ultra-precision optical and electrical integration of mechanical system should be guided by an integrated performance analysis. In this paper, the study of grating imaging theory, computational Fourier optics theory and finite element modal analysis is used to analyze the vibration of the scribing system of the grating machine. The main error caused by scribing system---the vibration of the turret guide---has been found out. Then, the scheme of improving and optimizing the structure, which achieved good optimization effects, has been proposed.Considering the structure features and the accuracy requirements of the positioning table in the indexing system, the multi-objective optimization theory research which is based on genetic algorithm is conducted. In order to improve the accuracy of multi-objective optimization, an integration optimization platform which is based on Pro/E-Matlab integrated optimization technology is proposed. Accurate CAE analysis based on3D model is conducted in the Pro/E platform and based on the results of the analysis, the search of optimum solution is conducted in the Matlab platform. Then, a multi-objective structural optimization is conducted in the positioning table of the indexing system, and the correctness of the optimization platform is verified through the simulation experiments.At last, the present research studied the control of the indexing system of the grating ruling machine and analyzed errors of the groove. Controllability and observability of grating ruling machine’s control model are analyzed from the perspective of the state space. PID feedback control based on neural network is utilized to the indexing system. Experiment results reveal the efficient and robust of the control scheme and show that the positional accuracy has been readily achieved within5nm and quality of the groove has made great improvements. After collecting a large number of experiment data, statistical analysis and error analysis of the groove is carried out to verify the validity of structure optimization and control algorithms.