Study Of The Passive Lateral Support Of The 2m-SiC Primary Mirror

The primary mirror is the critical optical element of the ground-based telescope,its’ support system directly affects the imaging quality.With the development of the aperture of primary mirror,the primary mirror lateral support design is becoming more and more important.In this paper,according to the requirement of the accuracy of the primary mirror surface figure error,the support system natural frequency and temperature adaptability,the 2m-Si C primary mirror lateral support system is studied and designed.Through the review of relevant reference,the development of the 2m telescope lateral support is studied.While the basic theory of the primary mirror lateral support and the common lateral support method were studied,based on the kinematics principle,the 12-point Whiffletree lateral support design was proposed.Under the guidance of the primary mirror lateral support theory,the supporting point position and the supporting force angle are optimized.On this basis,the supporting force value of each point is optimized by ANSYS,MATLAB and i SIGHT.Two different optimized plans are compared and the general scheme of the lateral supports is finally adopted.The dynamic FEM of the designed support system is carried out,and the result indicates that the natural frequency of the system is about 23.96 Hz.Under the combined effects of the axial and lateral supports,the mirror surface figure error under different alt-az angles is analyzed,and the design requirements are achieved.It is found that if the lateral supporting structure is fixed in the mirror cell,the mirror surface figure error would be 3566.81 nm when a 10℃ load was applied.In order to reduce the influence of the temperature load on the mirror surface figure error,a structure which can eliminate thermal stress is designed.Finally,the mirror surface figure error rms is 18.056 nm when the optical axis is horizontal,and 7.05 nm when the system temperature changes at 10 degrees,the overall performance meet the design requirements.At the end of this paper,the influence of the errors of the key parameters in the lateral support system is discussed.The errors which may have a great impact on the mirror surface error were analyzed individually and comprehensively,and the guidance for the processing and assembly in the future was given.