大型射电望远镜副面表面形状与位姿实时测量及其对电性能影响机理研究

The influence of antenna pointing accuracy and efficiency induced by sub-reflector position, attitude and the surface shape change cannot be ignored due to the rapid increase of antenna aperture and observation frequency. So an alignment mechanism should be installed to compensate the sub-reflector deformation. Controlled by present measurement methods, only the system load such as gravity can be corrected, the random load cannot be compensated. This will be strongly restriction the observation time at high frequency. The tiny changes of large antenna sub-reflector will lead to seriously electrical performance reduction; the error distribution rules for sub-reflector surface are difference due to the outer environment loads, it cannot be reference the influence by main-reflector surface. This project will carry out real-time measurement on large radio telescope sub-reflector surface shape position and attitude and its influence on electrical performance, using strain sensors to measure the sub-reflector deformation on shape and the supporting legs, combination with wire sensors a closed loop method use for measurement the sub-reflector position and attitude will be accomplished. Based on electro-mechanical coupling theory the analysis model about antenna electrical performance influence rule induced by sub-reflector position and attitude will be established. The results will be firstly tested by some simple designed samples, then using the old Nanshan 25 m antenna sub-reflector to carry out site measurement, and the electrical performance influence model will be revised. All the results can be used for the sub-reflector alignment due to the best electrical performance. All these will accumulation experiences for the upcoming QTT project.

副面因位姿与形状变化对天线指向和效率的影响，随天线口径增大观测频段提高愈发不可忽视。为此需要安装调整机构对副面变形进行补偿，受制于当前测量手段，仅对系统性载荷(如重力)引起变形进行补偿，对于随机环境载荷(温度等)不能补偿，将极大限制天线在高频工作有效时间。大天线副面微小变化会导致严重电性能下降，环境载荷导致副面误差分布规律千差万别，不能简单类比主面带来影响。本项目开展副面表面形状与位姿实时测量及其对电性能影响机理研究，采用应变传感器实现副反射体撑腿以及副面变形测量，并结合拉线传感器实现副面形状和姿态的闭环测量。通过机电耦合理论建立副面位姿与变形对天线电性能影响机理分析模型。设计简易实验样件检验变形测量与影响机理，利用南山25米天线旧副面构建测量平台，基于台址环境开展实地测量，修正影响机理分析模型，最终指导基于天线电性能下的副面调整。为新疆110米天线副面变形、位姿测量与电性能调整提供支持。

本项目针对大型射电望远镜，因副面位姿与形状变化对天线指向和效率的影响，造成天线综合性能下降开展研究。在项目研究开展的三年内，针对项目研究内容与关键技术，按照项目计划，项目组开展了认真细致的研究，很好的完成了研究工作，主要有：1)创新提出了基于光纤光栅应变传感器的桁架变形进行实时重构方案，建立了应变与结构变形间的数学模型，提出了传感器分布的准则，并通过南山实验场副面支撑结构实验验证了所提方法的有效性；2)建立了四节点单元的平面板和8节点单元的壳结构应变与结构变形的模型；3)基于电磁仿真与优化，获取了不同副面位置对天线电性能的影响；4)基于反射面面板分环、分块的特点，进一步分析了反射面表面误差分布及其对天线电性能的影响机理，为反射面天线电性能的估算与面板的公差分配提供参考。依托本项目研究，项目相关人员参加国内外学术会议8次，并做口头报告6次，参与各类技术交流活动11次。项目组成员共发表标注基金号文章11篇，另外还有几篇文章正在刊发中，授权专利1项，构建实验测试及验证平台一套。项目组参与成员包括研究生通过该项目得到锻炼，已有3位参与本项目研究的成员成功申请到国家青年基金、协助培养的3名研究生已经毕业。继续在单位工作的成员必将成为110米天线建设的主力军。