丽江2.4 m望远镜耐焦卡焦切换系统的设计与分析

Design and analysis of Lijiang 2.4-meter telescope Nasmyth focus and Cassgrain focus switching system

针对丽江2.4 m望远镜耐焦与卡焦不能自动切换的现状,设计了一套M3切换系统,实现焦点间快速切换,进一步提高望远镜的观测能力。首先对切换系统进行结构设计,介绍了系统的组成和实现方法,然后进行了精度分析及有限元分析,最后通过实验进行了标定和测试。有限元分析结果表明,在重力作用下反射镜的面形精度RMS<λ/60(λ=632.8 nm),切换系统的一阶模态达到了34.71 Hz,整个系统具有较好的刚度。实验测试表明,方位轴系和俯仰轴系的重复定位精度优于0.5″,平移机构的重复定位精度为1μm。该切换系统的性能指标达到了设计要求,并已装调于该望远镜且投入观测使用,同时也为类似望远镜的设计提供了参考。

In order to solve the situation that the 2.4-meter telescope cannot switch Nasmyth focus and Cassgrain focus intelligently,a switching system was designed to switch focuses rapidly to improve the observation ability.Firstly,a M3 switching system model was built,the composition and implementation of the system were discussed in detail.Then precision analysis and finite element analysis were performed to optimize design.Finally,the calibration and test were carried out through experiment.Finite element analysis shows that under the action of gravity,the mirror surface shape RMS<λ/60(λ=632.8 nm).The first-order modal of system reaches 34.71 Hz,the system has good stiffness.Experimental measurement shows that azimuth structure and altitude structure repetition precision are superior to 0.5″,translation stage repetition precision is 1μm.The switching system meets the performance requirements and has been installed in the telescope,which has been used for observation.It also provides a reference for the design of other telescopes.