An experimental method and device for operating modal analysis based on cross-spectrum function

Abstract

The invention relates to a cross spectral function-based operational modal analysis experiment method. The method comprises the following steps that: (1), a beam is suspended by elastic ropes and a steel hammer is used for exerting pulsed excitation on the beam at a selected excitation point; (2), response signals generated by a reference point and a response point after the pulsed excitation are collected; (3), band-pass filtering is carried out on the collected signals; (4), a cross-power spectral function between the reference point and the response point is calculated and a matrix equation formed by data of the cross-power spectral function at different sampling moments is constructed; (5), a coefficient matrix is calculated by using the matrix equation so as to obtain a system pole; (6), a modal shape matrix and a modal participation factor matrix are identified; and (7), modal assurance criterion matrix value calculation is carried out; and when the modal assurance criterion value is in a preset reasonable range, a modal parameter of the beam is obtained. In addition, the invention also provides a cross spectral function-based operational modal analysis experiment apparatus. According to the invention, the experiment intensity and time are reduced; and the test efficiency as well as the learning effect of students is also substantially improved.

Description

technical field [0001] The invention relates to the technical field of operation mode analysis, in particular to an operation mode analysis experiment method and device. Background technique [0002] In the teaching process of engineering testing technology, mechanical vibration and other courses, adding some modal analysis experiments can stimulate students' interest in learning, mobilize students' learning enthusiasm and initiative, cultivate students' innovative ability, and greatly improve the teaching effect. Through experiments, students can gain rich perceptual knowledge, deepen their understanding of the concept of modal parameters and their solution methods, and reduce the difficulty of students encountering problems in the process of self-study. [0003] Modal testing is often used in the extraction of modal models under actual working conditions, state monitoring and analysis, nonlinear system research, failure analysis and verification of the correctness of finit...

AI Technical Summary

Problems solved by technology

The parameter identification methods in operational modal analysis can be divided into time domain, frequency domain and time-frequency domain identification methods, etc., mainly including time series method, random decrement method (random decrement, RD), environmental excitation method, random subspace method , Empirical mode decomposition (empirical mode decomposition, EMD), peak picking method, frequency domain decomposition method and continuous wavelet transform method, etc., the existing analysis methods are mostly based on the assumption that the excitation signal is zero-mean white noise, and each method is There are certain limitations, for example, it is difficult to determine the model order of the time series method; the natural excitation method requires long data samples and many average times; the determination of the model order of the stochastic subspace method is cumbersome, and when there are many measurement points, Hankel The matrix order is very high, which is easy to cause the problem of matrix ill-conditioning; the disadvantage of the frequency domain method is that it requires high frequency resolution; the time-frequency analysis method uses less response information, and is a local identification method, etc.

In order to improve the learning effect of students, it is necessary to carry out experimental teaching of operational modal analysis. However, there is no such experimental device at present, so the experimental method and device of operational modal analysis for teaching needs need to be studied urgently.

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