虚假模态参数识别试验研究

Experimental research on false modes parameter identification

摘要:

为有效识别试验模态分析过程中的虚假模态和轴对称结构中的密集模态,对铝合金薄壳截锥壳卫星适配器样机的动态特性进行试验研究. 采用电磁激振器进行激励和压电加速度传感器采集响应,获得结构整体频响函数. 采用多项式方法拟合试验曲线,识别结构的模态参数. 系统比较单输入单输出、单输入多输出、多输入多输出等方法对频响函数曲线中密集模态参数识别的影响,并对比分析试验结果与有限元仿真结果,进一步识别试验测试曲线中的虚假模态参数. 试验结果表明:多输入多输出法更有利于分离轴对称结构的密集模态,试验获得铝合金截锥壳卫星适配器的前10阶固有模态;激振器安装不当导致频响函数曲线中存在虚假模态;对轻质结构进行试验模态分析时,需要考虑激振器的附加质量和附加刚度影响.

Abstract:

To discern false modes during experimental modal analysis process and identify dense modes in axial symmetrical structures, the dynamic properties of truncated conic aluminum alloy thin shell satellite adaptor was experimental investigated. Electromagnetic vibration generators were used for exciting structures, and piezoelectric accelerometers for measuring the corresponding response. Polynomial method was applied for fitting experimental frequency response functions and identifying modal parameters. The effects of different methods between single input single output (SISO), single input multiple output (SIMO), and multiple input multiple output (MIMO) were evaluated systematically, both experimental and numerical analysis results were compared to recognize false modes. The experimental results show that the MIMO method helps in splitting dense modes in axial symmetry structures, and the former 10 modes of satellite adaptor were clearly identified. However, improper exciter fixation results in false modes in frequency response function. For experimental modal analysis of lightweight structures, special attention should be paid on additional mass and stiffness due to exciter fixation.