Research On Opto-mechanical Structure Design Of Large Aperture Reflecting Telescope In Near Space

In recent years,reflective telescopes have been widely used in modern large telescopes because of their advantages such as colorlessness and ease of fabrication.Ground-based telescopes are limited by the basic limitations of the atmosphere that prevent them from accessing certain spectral regions,while space observatories are inherently expensive and operationally limited due to aircraft capabilities that often do not allow for post-launch instrument updates or corrections.So the advantages of using a balloon mounted on a retrievable telescope in close space to overcome the obstacles of the Earth's atmosphere become apparent.With the continuous improvement of the resolution of space exploration required by astronomical observation,the aperture of the main mirror of the space camera is getting larger and larger,which brings difficulties to the design of the optomechanical structure of the telescope.This paper relies on a load item suitable for near space.?816mm aperture telescope's optical and mechanical structure design is the research object.Aiming at the scientific problems of mirror design,composite support structure design and precision assembly,the research is carried out from theoretical research,structural design,simulation optimization and experimental verification.:(1)A composite support scheme with 6 points on the back and 6 points on the periphery was proposed.The ?816mm near space telescope has a pitch angle variation of 0° to 65° during observation.The traditional support scheme cannot meet the observation requirements because of the elevation angle change.Based on the development of the space large aperture telescope,the principle and supporting form of the large aperture mirror are expounded.And according to the principle of kinematics support to determine the peripheral support combined with back support composite support for the primary mirror support scheme of the subject.(2)The design of the primary mirror body is completed according to the requirements of the optical properties,weight and working environment of the816 mm caliber mirror,according to the traditional empirical formula and topology optimization method.Depending on the results of the physical main mirror,find the power path of the back support,determine the lightweight hole form of the main mirror and the distribution of the back reinforcing rib.The weight mirror weight of the lightweight form of a triangular + local fan-shaped lightweight hole is only 32.6kg,and the optical axis horizontal RMS is 1.21 nm,and the optical axis vertical surface RMS is 2.82 nm,preferably ? / 50(? = 632.8 nm).(3)A method of calculation of a straight beam hinge is proposed based on the coordinate transformation method.Firstly,the motion characteristics of six degrees of freedom of flexible structure are analyzed,and the flexibility matrix of ordinary flexible element is obtained.Then the deformation theory of Von Mise is deduced by coordinate transformation method,and the flexibility matrix of the straight beam rounded flexure hinge at the end of beam is obtained.According to the results of functional allocation and index assignment,the structural design of flexible thin rod in back support is carried out by sensitivity analysis and parameter optimization.The flexibility analysis method and the comprehensive evaluation factor are used to design the A frame in the surrounding support.Finally,through decoupling analysis,the main mirror face types under vertical and horizontal state of optical axis are obtained.The analysis results show that the flexible support designed by flexibility analysis method not only meets the requirement of surface shape,but also meets the decoupling requirement.(4)The equivalent planar model of the Serrurier truss and the rigidity of the triangular trusses in the triangular trusses derived the displacement formula and the self-vibration frequency formula caused by the displacement formula and gravity eccentricity in different gravity directions,and provided the theoretical basis for the truss design.(5)The results of the optical-mechanical structure design of the near space telescope were investigated by the method of simulation analysis and experimental verification.The stability of the whole telescope system under various working conditions was verified by the finite element analysis through the analysis of the dynamic characteristics,dynamic response and static performance of the whole telescope system.Combined with the surface detection of the primary mirror assembly and the installation test results of the telescope system,the feasibility and effectiveness of the telescope support scheme and related design methods adopted in this paper are also demonstrated.