MINIMIZING NOISE EFFECTS IN STRUCTURAL HEALTH MONITORING USING HILBERT TRANSFORM OF THE CONDENSED FRF

A novel model updating-based damage detection method is proposed that uses the Unwrapped Instantaneous Hilbert Phase (UIHP) of the condensed frequency response function (CFRF) as input to the objective function of an optimisation problem. The novelty of the proposed method lies in two items: (1) using the CFRF instead of the FRF itself, and (2) using the UIHP associated with the columns of the CFRF as input. The proposed modifications bring about the following improvements in the damage detection practice as follows: (1) CFRF will reduce the number of required degrees of freedom (DOFs) to be measured, and (2) the UIHP mitigates the effect of the measurement noise on damage detection. The problem of damage detection in a laminated composite plate with different number of layers and ply orientation has been solved where the results demonstrate the effectiveness of the proposed method.