含张力绳网伞状天线模态局部化研究

Mode localization in an umbrella antenna with tensile ropes

伞状天线属于典型的循环周期结构,天线肋为复合材料制件,其在尺寸、刚度、质量等方面的加工制作误差是客观存在的,天线肋之间的不一致会导致天线的模态局部化。模态局部化会影响天线的型面保持能力,同时对天线结构的健康带来隐患,因此抑制天线肋的模态局部化是伞状天线设计中不可忽视的问题。结合某型号伞状天线的研制,进行了含张力绳伞状天线结构的动力学理论推导,在天线肋刚度测试的基础上进行了天线结构的模态局部化仿真分析和试验。分析及试验结果显示,在张力绳刚度达到3.0N/mm后,天线结构由弱耦合系统转换为强耦合系统,天线肋的模态局部化得到有效控制。

Ribs of umbrella antennas are usually made of composite materials,which have large discreteness in material properties.The mode localization is common in such periodic cycling structure as the controls of mass and dimension are difficult for engineering realization.The model localization of the antenna can worsen radio frequency performance.The excessive vibration of the rib can keep the structure in a high stress status,which is unacceptable for the antenna reliability design.In this paper,the mode localization in an umbrella antenna is studied.Firstly,dynamic equation of the antenna with periodic cycling ribs and tensile ropes is derived.The modal frequencies and the modal shapes of the antenna come to an eigenvalue problem.Secondly,stiffness test of the ribs is conducted and the test results are used for structural mode localization simulation.Tensile ropes with stiffness of 1.0 N/mm and 3.0 N/mm are used for mode localization suppression.The final simulation and modal test results show that,for tensile ropes with stiffness up to 3.0 N/mm,the antenna changes from a weakly coupling system to a strongly coupling system,mode localization of the ribs are effectively controlled.