The assumption that frequencies of responses of linear time-varying systems vary linearly in a short-time was proposed. By fitting the time-varying responses to multi-component line frequency modulation signals

a physical parameter identification method of time-varying systems under random white noise excitation was obtained according to the cross-correlation theory of line frequency modulation signals. The mass and stiffness coefficients of time-varying structures were identified only using the acceleration response. Due to the introduction of frequency modulation factor to describe the variation of frequencies of response signals in a short-time

this method could track fast changes or even abrupt changes of parameters better than traditional identification method

so it had important application value for time-varying structures in practical engineering. In the simulation example

a 3-degress of freedom time-varying structure model was constructed to identify linear

periodic and abrupt changes of physical parameters. The error analysis showed that the identification errors were all within 5%. The results verified the correctness and applicability of the method.