Instantaneous Frequency Identification of Time-Varying Structures Using Maximum Coefficient Based Multi-synchrosqueezing Transform

In order to solve the problem of non-reassigned points in multi-synchrosqueezing transform and its improved algorithm,a maximum coefficient based multi-synchrosqueezing transform(MCMSST)is proposed to identify the instantaneous frequency(IF)of nonstationary response signals from time-varying structures. The Fourier spectrum is introduced at first to facilitate the selection of cut-off frequency of multi-component signals. After that,short-time Fourier transform is performed on the response signal and the estimated IF can be obtained by taking partial derivative of the Fourier coefficients with respect to time. Multiple iterations are then applied on the obtained IF and only the maximum modulus of time frequency coefficient is retained,in which extra coefficients at other positions are defined as zero. Finally,an operation of reassignment is performed on the estimated IF to get a refined IF band. Due to what the MCMSST extracts is only an IF band but not an IF curve, the maxima of time frequency coefficient modulus method is applied to extract the IF curve in the frequency band restricted by MCMSST. In addition,two numerical cases and an aluminum cantilever beam test with abrupt mass reduction are investigated to verify the effectiveness of the proposed method. The results demonstrate that the proposed MCMSST not only completely removes non-reassigned points in the refined frequency band,but also enhance the accuracy of IF identification and the robustness on noise resistance. © 2024 Nanjing University of Aeronautics an Astronautics. All rights reserved.