Study on Singular Spectrum Analysis as a data-driven technique for damage diagnosis. Comparison between time and frequency domain.

Abstract

Abstract. Vibration-based Structural Health Monitoring methodologies have been developed in many different applications with the aim of damage diagnosis. Recently, purely data-driven methods have been gained popularity because these methods do not assume any linearity or model in their analysis. Data-driven methods use the measured vibration signals as data-input to extract features that can conclude obtain useful information for the damage diagnosis. In this work a methodology based on Singular Spectrum Analysis (SSA) technique is presented which decomposes the measured vibration responses in a certain number of principal components which reveal the rotational patterns at any frequency in the motion. One of the steps of the methodology is to create a reference state where the observations can be compared for damage assessment. The data used to create the reference state determines how the information is represented in the reference state and therefore how meaningful and informative are the feature vectors for damage assessment. This study presents of the effect of the data representation considered on the creation of the reference state when the data is introduced in the time or frequency domain. The results obtained are different depending on the signal representation and hence they should have different interpretation when the state is created based on vibratory signals represented in the time or frequency domain.

An experimental study on the data-driven structural health monitoring of large wind turbine blades using a single accelerometer and actuator

“…The selection of the sliding window size W will affect the signal decomposition in the SSA methodology and it will depend on each case of study. A study was presented in the effect of W when SSA is applied in the time domain or frequency domain [19]. As a general overview, when, it comes to the frequency domain, a large number of W will result in an excessively smooth version of the original signal and therefore the consideration of more RCs will be needed to represent the dynamics of the measurement.…”

“…It can be observed that the reconstruction with 2 RCs is smoother than the reconstruction with 5 RCs. Therefore, it is clear that depending on how many RCs are used to obtain the FVs, more or less information in the original spectral line will be taken into account [19]. As a visualization of the methodology performance, the damage indices obtained by accelerometer 1 at the TE are presented in Fig.…”

“…SSA can be applied in the time [17] and frequency domain [18]. This will depend on the aim of the study and therefore the interpretation of the results will be different [19]. Based on above introduction the work presented here introduces a VSHM methodology based on a data-driven technique with its foundations on SSA for wind turbine blade damage assessment.…”