The Design And Research Of Multiple Degree Of Freedom M3 Assembly In Large-aperture Telescope

In the large-aperture ground-based electro-optical telescope (LGEOT) of coaxial and reflective Cassegrain system,the tertiary mirror assembly(M3 assembly) ,as one of critical components,need to be researched and analysised with detail in the theory to thoroughly satisfy the requirement of the telescope system.Based on the project of 2m LGEOT,taking the M3 assembly as object,the design and study of the each part of it would provide reference for large-aperture telescope project. The followed is the main work:Based on lots of literatures, the studies and applications of the structural system of M3 assembly of large optical telescope both internal and abroad was introduced, also the typical structure of multiple degree of freedom M3 assembly were compared. Finally a scheme of structural system design for M3assembly was put forward which would fit the requirements of the project. Based on the finite element and structural mechanics theory,the lightweight design of M3 was carried out,meanwhile,considering the effect of lightweight structure parameters to the mirror surface quality, the lightweight structure parameters was optimized with the aid of finite element software ANSYS,MSC.Patran/Nastran.Due to the adverse impact of material thermal expansivity mismatch and temperature variation for the mirror surface quality,based on elasticity mechanics theory,a new flexible support structure was designed for M3,meanwhile,the finite element simulation analysis was carried out to ensure the support performance.According to the essential requirements of two degree freedom Tip/Tilt adjusting mechanism and combined with flexible hinge theory,put forward a Tip/Tilt adjusting mechanism which based on cross-blade hinge. The flexibility equation of cross-blade hinge was provided,the precision of rotation and limit stress was analysed,the bending stiffness of the used cross-blade hinge, and finally, the actuator of the adjusting mechanism was selected by comparison of piezoceramics and voice coil motor,finally,the whole 3D model of the adjusting mechanism was provided.By the consideration the boundary dimension,positioning accuracy,stability ,the design scheme of the single-degree-of-freedom turntable was put forward。Based on theory of the principle of the bulk concentrated ball-bearing structure,the turntable shafting was designed and with its precision analysed and calculated. Torque motor was selected and analysed.