2m望远镜方位轴系倾角回转误差分析

Wobble Error Analysis for Azimuth Shafting Dip of 2m Telescope

为了寻找引起2m望远镜方位轴系倾角回转误差的主要误差源,相应采取措施减小或消除,确保望远镜方位轴系有较高的回转精度,采用国军标中水平仪法测量方位轴系倾角回转误差,对测量数据进行傅立叶谐波展开,分别对常数项和前三次谐波来源进行了分析。常数项和一次谐波为操作误差,予以去除,对比不同轴承结构的方位轴系,得出二次谐波来源于轴承滚道面加工误差,利用有限元分析得出三点调平支撑对大型方位轴系不能提供足够的刚度,由此引起三次谐波。去除操作误差的方位轴系倾角回转误差为1.7″,三点支撑引起轴系晃动量为0.6″,去除二次和三次谐波后,倾角回转误差仅为0.1″。提高轴承滚道面的加工精度,提供一个稳定的高刚度支撑,可有效提高方位轴系的倾角回转误差。

In order to find out source of wobble error of azimuth shafting dip of 2m telescope and adopt corresponding techniques to eliminate or decrease error source, so rotation precision of azimuth shafting can be improved. Gradienter method according to GJB 1801-93 was adopted to measure wobble error of azimuth shafting;and measure data was spread of Fourier harmonic. Constant item and the first order harmonic was caused by operation and should be subtracted. It was concluded by comparing different bearing configuration that the second order harmonic was generated because of machining error of bearing surface. Three pads couldn＇t provide enough rigidity for large azimuth shafting by FEA,so the third order harmonic was generated. Wobble error of the azimuth shafting dip was 1.7 ″ after subtracted operation error, and wobble error was generated by three pads was 0.6 ″. It was only 0.1 ″ after subtracted the second and the third order harmonic. Wobble error of azimuth shafting dip can be obviously decreased by improving machining precision for bearing surface and providing enoughrigid support, so rotation precision of azimuth shafting can be improved.