水平式望远镜轴系刚度分析及轴系误差的修正

摘要

为了解40 cm水平式望远镜经纬轴系的刚度,并解决轴系误差检测值与实际使用中轴系精度之间的矛盾,本文采用有限元法,对经纬轴系关键性部件进行了模态分析和重力变形分析,分析结果表明结构刚度满足设计指标要求.利用不同经度角下经轴轴系支撑结构的重力变形分析结果,计算出重力变形引起的经轴晃动误差,并与检测结果进行比较,得出两者均具有随经度角改变而正弦变化的相同规律.利用计算值对检测值进行误差补偿,使得经轴轴系晃动误差PV值从7.2"降到2.6",RMS值从0.7"降到0.3",补偿后的经轴晃动误差更符合实际使用状态下的轴系精度情况,可作为经轴轴系性能是否满足指标要求的准确判据.%In order to estimate longitude and latitude shafts rigidity and resolve conflict between shaft error test result and actual work performance of the 40 cm alt-alt telescope, vibration modes and gravity deformations at the different angles of the shaft were analyzed respectively by Finite Element Method (FEM). Frequencies and the max deformations of longitude and latitude shafts indicated that shaft rigidity satisfied the design requirement. From 0° to 180°　 longitude angle,longitude shaft shake error caused by gravity deformation was calculated. The shake error caused by structure deformation has the same sinusoidal variation pattem with the shaft error test result. The longitude shaft precision amendment is obtained by the compensation method that subtracting the calculated results from the test result. The shaft precision PV value is improved from 7.2" to 2.6" and the RMS value is improved from 0.7" to 0.3". The corrected shaft shake error is consistent with actual work performance state, and represents actual performance of the alt-alt telescope longitude shaft.