Research On System Modal Parameter Identification Based On Wavelet Transform Under The Ambient Excitation

Wavelet time-frequency analysis is a hot issue in recent years, it has been widely used in variousfields, the field of modal parameter identification is no exception. Unlike the frequency domain andtime domain modal parameter identification method, the signal will be unfolded with a certain scalesequence commenced in the time-frequency domain by the wavelet time-frequency analysis methods,and then the original signal’s frequency information will be unfolded intuitively in the time-frequency-amplitude axis of three-dimensional graphics.The main contents of this paper are the identification of modal parameters under the ambientexcitation and the intensive modal separation technology. The new method which named energythreshold and local energy maxima method which is used to extract wavelet ridge and separateintensive mode was proposed. And this parameter identification theory has been validated by thesimulation analysis and modal test. In the simulation analysis, Environmental motivation condition issimulated by a periodic signal and limited bandwidth random signal, on the MATLAB platform, thecantilever beam simulation model is established, and then apply the ambient excitation to thecantilever beam, calculate the time history response signal of each measuring point. Finally, make astudy of the modal parameter identification by the proposed method. In the modal test section, theGARTEUR aircraft model which has intensive-modal is selected as a test object, the excitation signalis the random white noise, the time history response signal and excitation signal are captured byacceleration sensor and force sensor synchronously based on the data acquisition platform of NI, thendo the research on parameter identification about time history response signal.The modal parameter of the simulation model and GARTEUR aircraft model were identified bythe proposed method, compare the identification results with the theoretical results, modal test resultsand the ERA results, the results show that this method has a certain accuracy in the identification ofmodal parameters under ambient excitation, its feasibility has been verified.