针对热膨胀率较大的SiC反射镜, 设计了结合A-Frame柔性切向杆侧向支撑结构和机械式Whiffletree轴向支撑结构、具有良好热解耦能力的1.2 m SiC轻量化主镜被动支撑系统。为研究A-Frame柔性侧向支撑机构对主镜支撑面形、热解耦和系统刚度的影响, 利用Ansys软件对支撑系统的支撑效果进行了有限元分析, 而后对实际的支撑系统进行了相关试验测试。测试显示在光轴竖直和水平两种状态下, 使用提出的支撑机构的支撑系统引起的主镜镜面变形误差RMS的变化小于13 nm; 在实验室温度14~23℃下, 检测得到主镜面形RMS最大差异为1.9 nm。利用模态分析仪对该主镜及支撑系统进行的动态测试表明: 系统的一阶固有频率为52.7 Hz, 而理论分析为63 Hz, 且前6阶模态振型与分析一致。得到的分析和测试结果都表明该被动支撑系统支撑效果良好, 且具有较高的支撑刚度和良好的热解耦能力。

For a SiC mirror with larger thermal expansion coefficients, a passive support system for light-weighted SiC primary mirror with thermal decoupling ability was designed by combing a A-Frame flexible tangential rod lateral support structure and a mechanical Whiffletree axial support structure. To obtain the effects of the A-Frame flexible tangential rod lateral support structure on the primary mirror surface, thermal decoupling and the stiffness of the support system, the support effect of the support system was analyzed by using Finite Element Analysis (FEA) with ANSYS. And actual support system was also tested. The tested results show that the distortion error change(RMS) of primary mirror caused by the support structure is less than 13 nm in horizontal and vertical states. The worst mirror surface error change(RMS) is 1.9 nm at the ambient temperature from 14℃ to 23℃ in a laboratory. The dynamic properties of the support system including mirror are also tested. The first natural frequency of support system is 52.7 Hz and the same analyzed result is 63.0 Hz in theory. Moreover, the first six vibration modals are consistent well in both theoretical and experimental results. Finally, it concludes that this support system has excellent support effect and shows both good stiffness and thermal decoupling capability.