大口径主镜位置的实时检测

由于望远镜主镜位置的调整与主镜位置的实时监测相关,本文设计了基于位移传感器的主镜位置监测系统。重点考虑镜室重力变形的影响,利用解析几何方法得到了解算主镜位置的算法。以实验室的1.2mSiC主镜作为试验镜进行了主镜位置实时监测试验。在主镜绕支撑架做俯仰转动时,通过布置在主镜背部和侧向的6个位移传感器,实时采集测量数据,并利用有限元方法计算镜室的变形;最后将镜室变形作为系统差和传感器测量值代入解算算法,得到主镜沿X、Y、Z三向平移、绕X、Y轴转动角度及主镜半径随温度变化值。测试结果显示:该试验主镜的支撑系统中的轴向支撑刚度远大于侧向支撑刚度。当镜室转动45°时,主镜的Z向平移变化只有20μm,而X向平移和Y向平移分别为146μm和100μm。试验结果验证了提出的实时监测方法和监测系统的准确性,为大口径主镜实时位置校正提供了依据。

On line measurement of position for large primary mirror

When the primary mirror position of a telescope is adjusted ,its position should be measured in real time .This paper proposes an on line measuring system for the primary mirror position based on position sensors .By taking the deformation of a mirror cell into account ,a algorithm to solve the primary mirror position was obtained by using the space analytic geometry method .A 1 .23 m SiC mirror in our lab was used to complete the online measuring experiment for the primary mirror position .The measuring data were collected in real time by using 6 position sensors fixed at the back and later of the mirror when the mirror was turning around the rotation axis .The cell deformation was also analyzed by using finite element method .Finally ,the measuring values by the sensors and the cell deformation value were taken as the system’s difference to introduce the algorithm to obtain the X\Y \Z displacements ,rotation angles around X\Y axis and the extension of mirror radius caused by temperature changing . Experimental results indicate that the stiffness of axial supporting mechanism is much larger than that of the lateral one .When the rotation angle of mirror is 45° ,the mirror displacement in Z direction is about 20 μm ,and that in X and Z directions are 146 μm and 100 μm ,respectively .The accuracy of this method is verified by the test results ,which provides a reference for the correction of primary mirror positions in telescopes .