Research And Application On The Theory And Method Of Local Wave Analysis

In recent years, analysis of the non-stationary signal in equipment fault diagnosis, is always a complex and significant work. With the hard research, the local wave method is gradually turned into one of the effective method to solve non-stationary problems. In this paper, based on the former achievements linking to practical project, the local wave method is deeply developed and expanded. And the fault diagnosis method on mechanical equipment is researched on the basis of former work.Local wave method is imported especially for solving non-stationary problems of the equipment diagnosis. The method, which can decompose time varying signal into several local wave functions, is based on the instantaneous frequency of signals. Every function describes different frequency and scale of the inherence oscillation mode. Instantaneous frequency can be defined everywhere in every function. By Hilbert transform, local wave time-frequency spectrum can give enough information in both time domain and frequency domain.Aimed at the research status of local wave method, the problems in this method is analysed, such as the end effect, estimate of instantaneous frequency and how to choice the sampling frequency. The way is put forward for improvement on arithmetic based on envelope mean. The validity and accuracy of phase difference method is analysed and validated. The criterion of how to choice the sampling frequency is given in local wave method.Based on the former work, the characteristic of multi-distinguish frequency analysis of local wave method and time-scale filtering is researched. The expressions of the frequency distinguish ratio in the time-frequency spectrum is given. The formula of filter can also be found in this paper. The feasibility is proved by noise canceling of signals with noise. An approach, which can be called boundary spectrum and energy of frequency belt, is proposed based on the local wave spectrum. With these methods we can find the fault in rolling machine and reciprocating machine.Two-dimensional local wave decomposition is investigated on the basis of one dimensional decomposition method. A new way to obtain the local maxima and minima at boundary is brought forward. The boundary swing problem is effectively solved. The criterions for the sifting process and decompose process to stop is also given. An examination on image de-noising is carried out. It proves that detail information of image can be obtainedby two-dimensional local wave decomposition which. Image diagnosis method based on decomposition is put forward. Details of time-frequency grayer degree image with fault information can be picked up by two-dimensional decomposition. During this process, we may find the fault character.The research work mentioned above enhances the local wave method. It also proved that the methods which are introduced in the paper can effectively identify the fault and solve practical problems.