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Removal of non-stationary harmonics for operational modal analysis in time and frequency domain
Mechanical Systems and Signal Processing ( IF 7.9 ) Pub Date : 2021-09-04 , DOI: 10.1016/j.ymssp.2021.108329
Pieter-Jan Daems 1 , Cédric Peeters 1 , Patrick Guillaume 1 , Jan Helsen 1
Affiliation  

Operational Modal Analysis allows to assess the modal model of rotating machinery. However, it is needed to pre-process the measured vibration data such that the influence of the harmonic content is suppressed. In this paper, such pre-processing techniques are discussed. The main focus is on evaluating the effects of amplitude modulation, originating for example from speed and load oscillations in rotating machines, on the harmonic removal. Both frequency and time domain editing techniques are considered. To illustrate the need of taking these modulations into account, their effect on the performance of a classical frequency domain editing technique is first discussed. Afterwards, different methods are developed that are able to cope better with frequency and amplitude modulated harmonics. To this end, it is opted to extract the harmonic response in the time domain using complex demodulation. This response can either be used to directly perform the system identification, or it can be used to design filters. Two different filters are proposed with distinct goals. The first one directly sets the harmonic response to the level of the white noise response based on the demodulated signal, whereas the second one is designed to remove the effects of amplitude modulation. For the latter, it is shown that classical editing methods can afterwards be applied in a more efficient manner.



中文翻译:

在时域和频域中去除非平稳谐波以进行操作模态分析

运行模态分析允许评估旋转机械的模态模型。但是,需要对测得的振动数据进行预处理,以抑制谐波含量的影响。在本文中,讨论了这种预处理技术。主要重点是评估振幅调制对谐波消除的影响,例如源自旋转机器中的速度和负载振荡。考虑了频域和时域编辑技术。为了说明需要考虑这些调制,首先讨论它们对经典频域编辑技术性能的影响。之后,开发了能够更好地处理频率和幅度调制谐波的不同方法。为此,选择使用复数解调在时域中提取谐波响应。该响应既可用于直接执行系统识别,也可用于设计滤波器。提出了两种具有不同目标的不同过滤器。第一个直接将谐波响应设置为基于解调信号的白噪声响应水平,而第二个则旨在消除幅度调制的影响。对于后者,表明可以以更有效的方式应用经典的编辑方法。第一个直接将谐波响应设置为基于解调信号的白噪声响应水平,而第二个则旨在消除幅度调制的影响。对于后者,表明可以以更有效的方式应用经典的编辑方法。第一个直接将谐波响应设置为基于解调信号的白噪声响应水平,而第二个则旨在消除幅度调制的影响。对于后者,表明可以以更有效的方式应用经典的编辑方法。

更新日期:2021-09-04
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