An Experimental Method of Operational Modal Analysis Based on Pulse Excitation

Abstract

An experimental method for operating modal analysis based on pulse excitation, including the following steps: 1) Select the end point of the beam as the excitation point, and use a steel hammer to implement pulse excitation on the beam; 2) Collect the reference points and response points generated after the pulse excitation Response signal; 3) Perform band-pass filtering on the collected signal; 4) Find the cross-correlation function between the reference point and the response point, and construct a matrix equation group composed of data at different sampling times of the cross-correlation function; 5) Use the matrix equation group Solve the coefficient matrix; 6) identify the poles of the system, establish the least squares error steady-state diagram, and solve the mode shape; 7) if the modal confidence criterion value is not good, select different sampling time values, and return to step 4), Until the modal confidence criterion value is within the preset reasonable interval, the modal parameters of the beam are obtained. And a pulse excitation-based operating mode analysis experimental device is provided. The invention can reduce the test intensity and time, and improve the learning effect of students.

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 students' understanding of obscure physical concepts, theorems and laws, and reduce the difficulty of students encountering problems in the process of self-study; with the help of experiments, they can explain problems vividly, concretely and intuitively, and be able to Make abstract knowledge come alive quickly. [0003] The existing experimental modal analysis system generally consists of t...

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 order of the matrix 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 and long samples, and the structure is small damping; 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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