Optimization Design Of Space Large Aperture Telescope Optical Machine Structure

Ground observation is one of the main application directions of satellite technology.The earth observation satellite plays an indispensable role in national economy,social development and national security.Its application fields include meteorological forecast,land survey,crop estimation,forest investigation,environmental protection,disaster monitoring and so on.Its data and information have already been treated as the basic and strategic resources of the country.The space large aperture telescope is the main payload of the Earth observation satellite.With the increasing of telescope aperture,the proportion of composite material application has become larger and larger,and the traditional design method is no longer applicable to the modern large aperture optical system.In order to meet the requirements of structural stiffness and optical axis indication precision,to reduce the total mass of the structure,it is necessary to study the comprehensive optimization design method of space large aperture telescope with new composite material.The main contents of this study include:(1)The general method of the finite element analysis of space large aperture telescope are introduced,the design steps of the optimized design are studied,different softwares and input-output data for reflector mirror optimization are compared.These studies lay the technical foundation for the structure design and optimization of the space large-aperture telescope.The composition of optical mirror surface deformation is expounded.By using least square method,this paper calculates the RMS value and PV value of the parabolic surface mirror,spherical surface mirror and other mirrors,which lays the foundation for the analysis of the mirror deformation of large space telescope.(2)In order to effectively reduce the weight of the metal structure and glass mirror material telescope system,in this paper,the comprehensive design method of the structure and material of the new type composite telescope is studied,and the structural scheme and analysis model of the C/SIC telescope supporting tube with a high component aluminum base and the main mirror of Si C are established.Combined with the vibration test data,the finite element model of the related structure is modified,which provides a basis for further optimization analysis.Compared with the traditional telescope system of metal structure and glass mirror,a large scale lightweight design is realized under the precondition of satisfying the performance index.The results of vibration test and analysis of the telescope system are compared and analyzed,and the deficiencies in preliminary design are studied,and the improvement is proposed.(3)According to the improvement proposed before,the main and secondary mirror assemblies are optimized,the main mirror support structure is simpelified,the main optical back plate is combined with the substrate,and the optimized main mirror assembly is analyzed using finite element method.The secondary mirror is modified from the back three points to the back center point installation,and from the positive loading type to the flip,which reduces the stress concentration.In view of the problem of insufficient rigidity of the existing secondary mirror support tube,the structural topological algorithm with variable density method is adopted.Considering structural constraints of the secondary mirror,the structure material,weight,stiffness and deformation,the mirror support tube using ceramic based composite material is optimized,ites modal frequency increases from 82.5Hz to 114.8Hz,which provides a reference for engineering development.(4)In view of the coupling between the frame interface and the precision of the telescope and the whole optical system,based on the joint simulation analysis of large space telescope and system frame,the influence of interface flatness on the main mirror shape is analyzed,the modal parameters of the whole optical system integare studied,and the model is further modified with the vibration test data.It provides a theoretical basis for the integrated design of telescope and frame system.