结构动态测试传感器优化配置的预试验技术

Pre-test Technique for Optimization of Sensors Placement in Structure Dynamic Testing

传感器配置是结构动态测试的一项重要的技术措施,其效果决定了结构的各阶主要测试模态的有效程度。由此,首先对结构仿真模型进行预先的主元素分析,优化传感器的布置。在结构有限元模型(FEM)中,对模型固有特性进行分析,确认重要的结构模态和结构动态测试目标。利用Guyan缩减方法对模型的自由度进行主从划分;选取感兴趣的结构振型的主自由度,对应从有限元模型中提取缩减的"试验模型"。针对提取的缩减模型重新开展模态分析,采用模态置信度(MAC)指标评估各阶振型之间的相关性,进而量化并直观显示传感器的配置效果。对某型号无人直升机机身结构进行地面振动试验。通过从仿真模型中选取合适的振型主元,改进传感器的配置,能保证试验中获得期望的结构测试模态,验证了利用结构仿真模型在动态测试之前预先进行传感器优化配置的效果。

Sensors placement is a key step in the dynamic testing of structures. In this article, preliminary master-elementsanalysis of structural simulation models was done to optimize the sensors placement. A finite element model （FEM） ofthe structures was prepared. Structural modal analysis was performed to determine the key modals and the objective of thedynamic testing of the structures. Master-slave degrees of freedom （DOFs） of the structural finite element model were thenclassified using the Guyan reduction method. The master DOFs for the interesting vibration modes corresponding to the extracted“reduced test model”from the aircraft finite element model were defined. Modal analysis for the reduced model wasrepeated. Modal assurance criterion （MAC） was used to assess the correlation among the calculated mode shapes of the reducedmodel. The effects of optimal sensor placement were eventually quantified and clearly displayed. An actual examplewas demonstrated for the ground vibration test （GVT） of an unmanned helicopter fuselage. The optimal placement of testingsensors through selecting the suitable master vibration modes of FEM assured that the expected fuselage vibration modesfrom the GVT could be obtained. This verified the effectiveness of the structural simulation model for the optimization ofthe sensor placement before the dynamic testing.