大型射电望远镜主副面结构共轭保型设计与形面协同调整方法研究

The mismatch of main- and sub-reflector leads to the decrease of pointing precision and efficiency of dual reflector antenna, which seriously impact the observational performance of large radio telescopes at high frequency. To this end, it is necessary to match the main- and sub-reflector with position and shape. However, in tradition, only the main reflector is design homologously, but sub-reflector is considered rigid. On the one hand, there will be principal residual deformation which reducing the efficiency of antenna system. On the other hand, it can only reduce the influence of systematic error such as deformation caused by gravity, but not be useful to other random errors, such as temperature.deformation and so on. This will limit the effective time of radio telescope at high frequency. At the same time, the measurement and adjustment of panels in the main reflector surface is time-consuming and arduous. Only improving the main reflector surface accuracy limits the overall electrical performance of dual reflector system. This project aims at the mismatch of main- and sub-reflector with position and shape during both design and adjustment. It is appropriate to relax the stiffness of sub-reflector, in order to produce a certain and.controllable deformation in sub-reflector surface, so that the influence of phase distribution on the aperture is complementary to the main reflector. Thus the main- and sub-reflector are conjugated homology in the view of electrical performance. In addition, compensating the residual error of the main-reflector by adjusting the shape of sub-reflector, the phase error on the aperture field can be eliminated, so as to achieve the best matching of main- and sub-reflector. An experimental platform will be built using Nanshan 25m old antenna to verify the.proposed method, ultimately to guide the adjustment of the matching of main- and sub-reflector. It provides a substantial theoretical foundation for structural design and performance compensation of the QTT antenna.

主副面形位失配导致天线指向偏差和效率下降，对大口径高频段射电望远镜观测性能的影响愈发突出。为此需要对天线主副面位姿与形状进行最佳匹配，然而传统方法仅对主面进行保型而视副面为刚体，一方面存在主面保型残差，降低天线效率；另一方面只能减小自重变形等系统误差，对温度变形等随机误差不起作用，这将极大限制天线在高频工作有效时间。同时，主面精度测量与调整费时费力，单纯提高主面精度对系统整体性能的提升已接近极限。本项目针对主副面在设计与装调阶段的形位匹配问题，适当放松副面结构刚度，产生程度一定、分布可控的副面变形，使其对口径场相位分布的影响与主面互补，实现电性能意义下的主副面共轭保型。另外，通过调节副面形状补偿主面各类残差，实现口径场相位误差对消，达到主副形面协同匹配。利用南山25米旧天线构建实验平台，验证方法有效性，最终指导主副面匹配调整，为QTT天线副面结构设计、性能补偿提供理论指导。

超大口径射电望远镜设计过程中，面临着高指向精度带来的结构优化设计瓶颈问题。本项目针对主副面在设计与装调阶段的形位匹配问题，适当放松副面结构刚度，产生程度一定、分布可控的副面变形，使其对口径场相位分布的影响与主面互补，实现电性能意义下的主副面共轭保型。另外，通过调节副面形状补偿主面各类残差，实现口径场相位误差对消，达到主副形面协同匹配。利用南山25米天线构建实验平台，验证方法有效性。本项目完成的主要研究成果如下：.（1）双反射面天线机电耦合建模：望远镜在俯仰过程中受到自重、热等载荷作用，会使主副面结构发生变形、同时副面发生位置偏移和姿态偏转，误差最终导致主副面位置与形状均匹配不佳，最终导致天线电性能变差。针对上述各类误差，建立了其与口径场相位误差的定量影响关系，明确了其对望远镜最终电性能的影响；.（2）主副面结构共轭保型设计：基于前述机电耦合理论，建立主副面结构共轭保型优化设计模型，研究电性能意义下的结构设计变形归并，确定合适的优化求解策略，得到一组最优结构设计变量，实现了重力作用下的主副面形状最佳匹配；.（3）主副形面协同调整方法及实验验证：分析主副反射面面板调整量与口径场相位误差的影响，研究主副面变形区域的映射关系，建立主副形面调整参数的优化模型，通过调节副面变形，实现对口径场相位误差的对消，达到电性能意义下的主副形面协同调整。以新疆25米旧反射面天线为对象，通过实验验证了所提方法的有效性。.本项目所提出的超大口径射电望远镜天线主副面协同设计与调控技术方法，以电性能最优为目标函数，进行主副结构设计变量共轭归并，降低了对主面精度的要求，是一项具有创新性的保型设计方法，突破了百米级口径反射面天线优化设计的技术瓶颈问题，为将来更大口径望远镜天线的设计工作奠定了坚实的理论基础，可大幅提升我国超大口径射电望远镜的整体设计水平。