Wavelet-based Frequency Response Function for time-variant systems—An exploratory study

• A new wavelet-based FRF is proposed for time-variant systems.
• The method is based on the wavelet convolution theorem.
• The method is used for simulated and experimental time-variant data.

A wavelet-based Frequency Response Function (FRF) is proposed for vibration analysis of systems with time-varying parameters. The classical FRF is extended to a representation in the combined time–frequency domain using wavelet analysis. Time averaging is performed on the initial FRF to improve signal-to-noise ratio. It is shown that use of the wavelet ridge algorithm is effective in extracting and representing visually data from wavelet-based FRFs. The wavelet-based FRF is demonstrated on selected time-variant simulated lumped parameter systems and one experimental vibrating system.