大口径空间反射镜高精度面形检测的支撑技术研究

High-precision figure testing of large-aperture space mirrors

由于空间失重状态与地面状态不同,大口径空间反射镜在地面检测时需要通过特殊支撑结构对其重力进行卸载,同时严格控制支撑力引入的反射镜变形,以满足反射镜高精度面形检测的要求。通过对一口径750mm的空间SiC非球面反射镜进行检测,对比分析检测结果和有限元仿真结果,研究支撑结构对反射镜面形所造成的影响。主要针对吊带支撑和中心支撑进行详细的检测验证,分析其不能实现该反射镜高精度检测的原因;通过改进支撑方案,最后提出背板支撑,改善支撑变形的影响,不同角度下测量重复性达到纳米级,收到较好的检测效果,为该反射镜加工质量和加工效率的提升奠定了基础。

Due to different situations on the ground and in agravic space,special support structure is demanded to unload mirror gravity when testing large-aperture space mirrors on the ground.Meanwhile,deformation induced by clamping forces must be strictly controlled to meet the requirements of high-precision figure testing.This paper presents test experiments performed on a space aspheric mirror made of SiC with 750 mm aperture.Testing results are compared with the finite element analysis results to investigate the influence of the support structure on mirror surface figure.To analyze the causes of incapability of high-precision surface figure testing,the methods of strip suspension and central supporting are discussed.An improved method of backboard supporting is proposed,it reduces the supporting deformation and the repeatability of surface figure at different angles reaches nanometer level.It is proved to be able to achieve higher precision testing,which is a fundamental solution for improving machining quality and efficiency.