天马望远镜结构重力变形对面形和指向精度影响

以天马望远镜（简称TM65m）为研究对象，采用仿真与实验相结合的方法，对结构重力作用下主面面形精度和天线指向精度的变化进行了研究.借助有限元软件分析不同俯仰角下结构重力变形，得到主面相应的促动器调整量，将其加载到主动面系统中，经调整后天线效率在俯仰角35°和71°提高了20%.主面重力变形修正后，其顶点位置发生变化，将计算结果转化到指向模型中，得俯仰角由5°旋转到90°指向发生了0.037 99°的变化，与实际指向模型重力误差修正项系数的误差为4%.同时，发现天线俯仰及以上部分结构自重在不同俯仰角下引起俯仰轴弯曲变形，有限元分析得最大挠度为3.2 mm，挠度变化趋势与倾斜仪测量结果一致性较好，由此导致的俯仰指向变化达0.012 14°.因此，合理的结构设计对提高天线精度非常重要.

Effect of gravity deformation of TianMa telescope structure on the surface and pointing accuracy

Taking TianMa telescope (abbreviated as TM65m) as research object,the variations of primary surface accuracy and antenna pointing accuracy under gravity were researched using the method of combining simulation and experiment.The gravity deformations of structure were analyzed at different elevation angles by finite element software and the corresponding actuator adjustments of primary surface were obtained.The antenna efficiency improves 20％ at elevation angle of 35° and 71° when the actuator adjustments were loaded into the active surface system and the primary surface was adjusted.The vertex position of primary surface changed after the gravity deformations of the primary surface were modified.The variation of pointing error is 0.037 99° from 5° to 90° elevation angle when the position variations were converted into the pointing model,which is compared to the modified parameter of gravity error of the real pointing model and the error is 4％.Simultaneously,we found that the gravity of elevation structure and above it leads to elevation axis bend at different elevation angles.The maximum deflection acquired from finite element analysis is 3.2mm.The variation trend keeps in line with measured results of inclinometer,which results in the elevation pointing variation reaching 0.012 14° arc-second.Consequently,reasonable structure design is important to improve antenna accuracy.