大口径望远镜次镜桁架调整机构设计

Design of truss adjusting mechanism for secondary mirror of large aperture telescope

大口径望远镜主次镜之间的相对位姿有着非常严格的要求,由于主镜质量较大,因此常常将次镜系统设计为有多个自由度的可调整机构,其调整效果对望远镜成像有着重要的影响。为了降低望远镜的整体高度,对次镜桁架和次镜调整机构进行融合,设计了一种可用于大口径望远镜的次镜桁架调整机构。首先对所设计的调整机构进行了详细的介绍,之后对所设计的机构进行静力学和模态分析,然后对试验样机进行运动学性能测试。所设计的机构在Z方向的移动行程可达±5 mm,绝对定位精度优于16μm,在X/Y方向的偏转行程可达±0.574°,绝对定位精度优于6.4″。满足大口径望远镜对次镜调整精度和行程的要求。

In large-aperture telescopes,the relative positions of the primary and secondary mirrors must conform to stringent specifications.The secondary-mirror system is frequently designed as an adjustable mechanism with several degrees of freedom,owing to the high quality of the primary mirror.This significantly affects the telescope imaging.The secondary-mirror truss and adjustment mechanism are combined and designed to decrease the overall height of the telescope.Moreover,a secondary-mirror truss-adjustment mechanism that can be employed in large-diameter telescopes is designed.First,a detailed description of the designed adjustment mechanism is given,followed by static and modal analyses,and finally,a kinematic-performance test of the experimental prototype.The moving stroke of the designed mechanism in the Z direction can reach±5 mm and the absolute positioning accuracy is better than 16μm.The deflection stroke in the X/Y direction can reach±0.574°and the absolute positioning accuracy is better than 6.4″.The mechanism complies with the itinerary requirements and secondary-mirror adjustment accuracy for large-diameter telescopes.