A new SVD-based filtering technique for operational modal analysis in the presence of harmonic excitation and noise

Abstract

In most output-only-based modal identification methods, the excitation and the measurement error are assumed to be white Gaussian noise. One of the obstacles appears once the excitation has periodic nature and measurements are contaminated by colored noise. In this paper, a time-domain filtering technique is introduced for harmonic excitation/noise elimination in operational modal analysis. The procedure is based on the singular value decomposition of the vibrational response. If excitation, noise, and modal harmonics have no intersection, they will have independent counterparts within the decomposed row space. Therefore, the decomposed components are partly selected and explored in a few iterations and appropriated to the transient and steady-state response and noise contaminations. Then, the components associated with the steady-state response and noise are removed, and the transient response is used for identifying the observability matrix and modal parameters. The performance of the proposed procedure is investigated through several numerical and experimental case studies of vibrating structures, and compared with other methods. The effectiveness of the technique for eliminating the excitation and noise harmonics from the modal parameters, and reconstructing the vibration signals is verified.