Xu Xiuzhong 

Department of Mechanical Engineering,

Shanghai Maritime University,

 Shanghai 200135, China

Zhang Zhiyi

Hua Hongxing
National Key Laboratory of Vibration Shock & Noise,

Shanghai Jiaotong University,
Shanghai 200030, China

Chen Zhaoneng

School of Mechanical Engineering ,

Shanghai Jiaotong University,

 Shanghai 200030, China

Abstract: A new method of parameter identification based on linear time-frequency representation and Hilbert transform is proposed to identify modal parameters of linear time-varying systems from measured vibration responses. Using Gabor expansion and synthesis theory, measured responses are represented in the time-frequency domain and modal components are reconstructed by time-frequency filtering. The Hilbert transform is applied to obtain time histories of the amplitude and phase angle of each modal component, from which time-varying frequencies and damping ratios are identified. The proposed method has been demonstrated with a numerical example in which a linear time-varying system of two degrees of freedom is used to validate the identification scheme based on time-frequency representation. Simulation results have indicated that time-frequency representation presents an effective tool for modal parameter identification of time-varying systems.

Key words: Linear time-varying system  Modal parameter identification  Hilbert transform Gabor expansion