Instantaneous modal parameter identification of time-varying systems based on adaptive chirplet decomposition
ZHANG Jie，SHI Zhiyu，ZHAO Zongshuang
State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aeronautics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
An instantaneous modal parameter identification method of time-varying systems based on the time-frequency decomposition of chirplet transform (CT) was proposed.First, the adaptive linear chirplet transform was applied in the time-frequency analysis of time-varying system acceleration responses, and the instantaneous frequency was extracted by using the wavelet ridge method.Then each order response was adaptively decomposed to obtain the amplitude information with a Kalman filter.In order to more accurately identify the damping ratio of the structure, a time-varying damping ratio identification method based on the amplitude energy was also proposed.It is found that CT has higher energy concentration than the traditional wavelet.Therefore, the method has higher instantaneous frequency extraction accuracy.In addition, the traditional amplitude-based damping identification method is susceptible to noise interference, while the energy method has strong noise immunity and higher identification accuracy based on the integral of the amplitude in a short interval.As a simulation example, a three-degree-of-freedom time-varying structure was constructed to verify the correctness and anti-noise capability of the method.The method can more precisely identify the instantaneous frequency and damping ratio, comparing with the traditional wavelet and time domain peak method.
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