System Modal Parameter Identification Based On Continuous Wavelet Transform Method

This paper deals with the use of the continuous wavelet transform (CWT) for system identification purposes. CWT method is a new way to the identification of modal parameter. This time-frequency-domain method is a new developed method after time–domain and frequency-domain method. It has been proved that CWT method was exact at the identification of modal parameter, and was not sensitive to the noise. The main work and harvests of this paper are as follows:The wavelet ridge extraction method (REM) was studied in this paper. REM was used for the extraction of temporary frequency at before. REMs developed for this purpose would not work for modal parameter identification. A new method is introduced in this paper, called Crazy Climber method. Crazy Climber method can extract several ridges in the same time. It can be used for modal parameter identification of multi-degree-of-freedom (MDOF). But this method is sensitive to the noise. A improved study was introduced in this paper. The simulate result shows that the improved Crazy Climber method is not sensitive to the noise.Morlet wavelet was selected in this paper for identification purpose. A optimize wavelet method was used for the best time and frequency performances. A cantilever was tested to validate this method. The test result shows that the method is suit to the modal parameter identification.The edge-effect of wavelets was analyzed in this paper. A edge-effect measure method was introduced in this paper. In order to the MDOF identification, an equalizing function method was put forward. The simulate result shows that this method can modify the edge effected wavelet transform ridge commendably.The mass model question was studied in this paper. An estimate rule was introduced in this paper. This rule could divide mass models from normal models. A improved Morlet wavelet is used for the mass model estimation. A simulated 3DOF system was tested by the wavelet. The result shows that the improved Morlet wavelet is useful for mass model identification.