Abstract:

In operational modal analysis, it was difficult to identify all of system modes, when close modes existed, weak response signal submerged in big noise, and the response data was short. Consequently, a new method which combining transmissibility function and correlation function to identify system modal characteristics (combine method) was proposed herein. Specifically, transmissibility function which approximated to FRF was calculated to get frequency characteristic function of the system weak response, and then wavelet transform was exploited to achieve weak modal identification. The numerical simulation experiment was implemented, which utilizing GARTEUR plane model with random excitation to simulate outputs data in operational condition. At last, the results show that, compared with the poly-reference least squares complex frequency domain algorithm, this combine method can identify modal frequency with high precision. At the same time, the accuracy of damping ratio identification is improved greatly. Especially, transmissibility is good at weak modal identification with close modes.

Key words: operational modal, weak mode, transmissibility, correlation function, wavelet transform

摘要：

针对运行模态分析中响应信号数据样本较短、模态密集,以及弱响应信号淹没在大噪声中,系统模态难以全部辨识的问题,提出了联合相关函数与传递率识别系统模态参数的方法（联合方法）,该方法先应用传递率近似频响函数获取系统弱响应频率特征函数,然后再通过小波变换进行模态识别。运用随机激励下的GARTEUR飞机模型仿真运行状态的输出进行了数值仿真实验。结果表明：相比于多参考最小二乘复频域法,联合方法不仅能提高模态频率的识别精度,而且还能极大地提高阻尼比的识别精度,尤其是传递率对模态密集的弱响应模态识别结果良好。


关键词: 运行模态, 弱响应模态, 传递率, 相关函数, 小波变换