Decomposition Method of Weakly Nonlinear Signals in Offshore Structures

Abstract

The invention relates to a method for decomposing weakly nonlinear signals of offshore structures, comprising: determining the original dynamic response of the offshore structure to be tested and performing FFT transformation on it, sliding and dividing the full-frequency spectrum at equal intervals; dividing the divided sub-frequency bands The IFFT transformation is performed sequentially to obtain the original dynamic response sub-signals corresponding to each sub-frequency band; the original dynamic response sub-signals corresponding to each sub-frequency band are decomposed and reconstructed based on the Prony sequence; the original dynamic response sub-signals corresponding to each sub-frequency band are compared with the reconstructed The relative residuals of the dynamic response sub-signals are constructed to judge the decomposition accuracy of the original dynamic response sub-signals corresponding to each sub-band; the full-band dynamic response signals are reconstructed to judge the overall decomposition accuracy of the full-band original dynamic response signals. The method of the invention can efficiently realize the high-precision decomposition of the nonlinear signal of the marine structure, and provides a basis for applications such as modal parameter identification, time-frequency analysis, and noise elimination of the nonlinear signal.

Description

technical field [0001] The invention belongs to the technical field of dynamic design of marine structures, and in particular relates to a weak nonlinear signal decomposition method of marine structures. Background technique [0002] In order to ensure the safe operation of offshore wind power structures during their service life, structural design has evolved from a simple strength design stage to a reliability design stage. The dynamic design process of structures is no longer a simple calculation of structural dynamic characteristics, but has gradually developed into a process of dynamic response analysis of the entire structure. Due to the complexity of the marine environment in the actual offshore structure, the complexity of the measured signal is determined. Therefore, the measured signal usually has the characteristics of nonlinearity and non-stationarity. The traditional fast Fourier transform, wavelet transform and empirical mode decomposition are used It is diffi...

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Problems solved by technology

However, the frequency band division results of this method and its improved method based on it are susceptible to interference from spectrum leakage and noise pollution, and there is a problem that the various modes of the signal cannot be accurately separated.

[0004] Empirical mode decomposition is based on decomposing signals one by one from high to low frequency. However, due to the influence of the complex environment in which the actual offshore structure is located, modal aliasing and end-point effects usually occur, resulting in poor decomposition effects, and even break down problem

Although the variational empirical mode decomposition proposed on the basis of empirical mode decomposition overcomes the problems of mode mixing and other problems, some parameters required by it are difficult to be determined in advance, which limits its application in actual offshore structural engineering to a certain extent. application on

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