研制了一个用于1.2 m望远镜的次镜支撑结构, 以满足其对刚度和伺服系统带宽的要求。首先, 对影响主镜遮拦和支撑系统刚度的四翼梁进行研究。使用动力学建模方法, 初选四翼梁结构的参数。然后在ANSYS中建立有限元模型, 进行静力学和模态分析。最后, 使用试验模态分析法测试设计的支撑结构。有限元分析显示, 设计的结构受重力影响会引入0.004 2λ的切向彗差, 第一阶模态频率约为57.2 Hz。试验模态分析显示, 系统第一阶谐振频率为54.1 Hz, 与理论分析和有限元分析结果一致。实验结果与仿真结果对比后显示: 归一化的振型向量中叶片结构振幅较小时, 实验模态较难提取, 且实验结果略小于有限元分析结果, 最大相对误差约为7%。设计的次镜支撑结构遮拦小、刚度好, 满足使用要求。

A reasonable supporting structure between primary mirror and secondary mirror for a 1.2 m telescope was fabricated to meet its requirement for stiffness and the bandwidth of servo system. A four-vane spider effecting on the primary obstruction and secondary mirror stiffness was explored. The key parameters for the four-vane spider were selected by dynamic molding. Then, a finite element model was established in the ANSYS to perform static analysis and modal analysis. Finally, the modal analysis method was used to test the designed support structure. The finite element analysis shows that the designed structure effected by gravity induces about 0.004 2λ coma while the telescope points to the horizon, and the first-order modal frequency is about 57.2 Hz. The modal analysis indicates that the first-order resonance frequency is up to 54.1 Hz, which is in agreement with that of finite element analysis. Experimental results and FEA results are compared, and it shows that it is difficult to extract the modal when the vibration magnitude on the vane is smaller and obtained results are little smaller than that of the FEA, in which the maximum relative error is less than 7%. In conclusion, this design is not only a fewer obstruction but also an excellent stiffness, meeting the requirement of telescopes.