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Research And Application On The Theory Of Local Wave Time-Frequency Analysis Method

Posted on:2002-12-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q GaiFull Text:PDF
GTID:1118360032954586Subject:Mechanical and electrical engineering
Abstract/Summary:PDF Full Text Request
An overview of Time-Frequency analysis theory in the pass and now is given in this paper. Based on the study of former achievements and by using the newest Time-Frequency analysis method, I have developed a lot of new theory on Local Wave Time-Frequency analysis method by means of theory analysis, numerical computation and experiment.A core problem discussed in this paper is using Local Wave decomposition method and Hilbert spectrum to analyse nonlinear and non-stationary data. The key part of the method is the 'empirical mode decomposition ' method with which any complicated data set can be decomposed into a finite and often small number of 'intrinsic mode functions' that admit well-behaved Hilbert transforms. This decomposition method is adaptive, and, therefore, highly efficient. Since the decomposition is based on the local characteristic time scale of the data, it is applicable to nonlinear and non-stationary processes. With the Hilbert transform, the 'intrinsic mode functions' yield instantaneous frequencies as functions of time that give sharp identifications of imbedded structures. The final presentation of the results is an energy-frequency-time distribution, designated as the Hilbert spectrum.In the theoretical aspect, this paper pays special attention to Time-Frequency domain analysis method, and achieved some improvements both in theory and application. I first point out that the Local Wave Time-Frequency analysis method is a broad sense linear expression and deduce a mathematical decomposition formula of the Local Wave Method; Then I present an Extremum field Mean Mode Decomposition (EMMD) method based on the mean value theorem in a local ; And then I develop wave matching method to solve the end effect of the decomposition. In this paper, I present some new theory. First, I put forward a new concept of multi-frequency distinguish analysis of Local Wave Method, this method highly improves the resolution and precision of decomposition and is especially useful for the extraction of fault characteristics from nonlinear or non-stationary vibration signal. Next I presnt a adaptive filter group concept for filtering nonlinear and non-stationary data, thus explain the physical significance of the Local Wave Method ; Finally , I analyse the sense of adaptive broad sense radix, and explain the completeness and orthogonalityof the Local Wave Method.The main conceptual innovations are the introduction of intrinsic mode functions'based on local properties of the signal, which makes the instantaneous frequency meaningful; and the introduction of the instantaneous frequencies for complicated data sets, which eliminate the need for squrious harmonics to represent nonlinear and non-stationary signals.Practical application imply that the utilization of nonlinear and non-stationary character of signals is better then the ignorance of it, we can extract more fault characteristic of vibration signals by that, and obtain more physical explanation.
Keywords/Search Tags:nonlinear and non-stationary time series, intrinsic mode functions, time-frequency spectrum, Hilbert spectral analysis, fault diagnosis
PDF Full Text Request
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