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Open AccessArticle

An Improved Second-Order Blind Identification (SOBI) Signal De-Noising Method for Dynamic Deflection Measurements of Bridges Using Ground-Based Synthetic Aperture Radar (GBSAR)

1
Key Laboratory for Urban Geomatics of National Administration of Surveying, Mapping and Geoinformation, Beijing Key Laboratory for Architectural Heritage Fine Reconstruction & Health Monitoring, Beijing University of Civil Engineering and Architecture, 1 Zhanlanguan Road, Beijing 100044, China
2
Department of Geography, University College London, Gower Street, London WC1E 6BT, UK
*
Authors to whom correspondence should be addressed.
Appl. Sci. 2019, 9(17), 3561; https://doi.org/10.3390/app9173561
Received: 7 August 2019 / Revised: 23 August 2019 / Accepted: 28 August 2019 / Published: 30 August 2019
(This article belongs to the Special Issue Bridge Dynamics)
Ground-based synthetic aperture radar (GBSAR) technology has been widely used for bridge dynamic deflection measurements due to its advantages of non-contact measurements, high frequency, and high accuracy. To reduce the influence of noise in dynamic deflection measurements of bridges using GBSAR—especially for noise of the instantaneous vibrations of the instrument itself caused by passing vehicles—an improved second-order blind identification (SOBI) signal de-noising method is proposed to obtain the de-noised time-series displacement of bridges. First, the obtained time-series displacements of three adjacent monitoring points in the same time domain are selected as observation signals, and the second-order correlations among the three time-series displacements are removed using a whitening process. Second, a mixing matrix is calculated using the joint approximation diagonalization technique for covariance matrices and to further obtain three separate signal components. Finally, the three separate signal components are converted in the frequency domain using the fast Fourier transform (FFT) algorithm, and the noise signal components are identified using a spectrum analysis. A new, independent, separated signal component matrix is generated using a zeroing process for the noise signal components. This process is inversely reconstructed using a mixing matrix to recover the original amplitude of the de-noised time-series displacement of the middle monitoring point among three adjacent monitoring points. The results of both simulated and on-site experiments show that the improved SOBI method has a powerful signal de-noising ability. View Full-Text
Keywords: second-order blind identification; bridge monitoring; microwave interferometry; ground-based synthetic aperture radar; signal de-noising second-order blind identification; bridge monitoring; microwave interferometry; ground-based synthetic aperture radar; signal de-noising
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Liu, X.; Wang, H.; Huang, M.; Yang, W. An Improved Second-Order Blind Identification (SOBI) Signal De-Noising Method for Dynamic Deflection Measurements of Bridges Using Ground-Based Synthetic Aperture Radar (GBSAR). Appl. Sci. 2019, 9, 3561.

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