Time-frequency identification: a review

Due to the importance of non-stationary components in vibration signals, several studies in the past have proposed the adoption of time-frequency analysis in structural identification and damage assessment. A major problem is that time-frequency domain representations are intrinsically unable to identify an energy density at every point in the time–frequency plane. Consequently, the definition of an instantaneous spectrum poses some conceptual problems, and similar difficulties apply to instantaneous estimates that originate from such representations. This paper is a comprehensive overview of the recent advances in the field of time-frequency analysis for structural identification, with illustrative examples to both linear and non-linear systems.