Frequency slice algorithm for modal signal separation and damping identification

Abstract

This paper focuses on modal signal separation and damping parameter identification by a new time-frequency analysis method. With the aid of the random decrement technique (RDT), an accurate estimation method is firstly introduced both in time and frequency domains for single modal damping identification. Next, the background of a new concept of frequency slice wavelet transform (FSWT) is revealed clearly. Then, some new properties of the FSWT are briefly discussed in contrast with the wavelet transform (WT). Based on the analysis of RDT and FSWT, a frequency slice algorithm (FSA) is designed for modal separation and parameter identification. The merits of FSWT and FSA with numerical simulations and experiments are demonstrated in this paper. We finally apply the proposed methods to analyze the free-decay responses (FDR) collected from a small laboratory bridge monitoring system (LBMS). Some conclusions are drawn that the RDT being used directly in FSWT domain can bring a good damping estimator. The FSA is not limited to FDR, and also can be used to random impacting response directly. FSWT itself is a new kind of good filter, and has high performance against noise. It is significant to get damping parameter with higher accuracy through modal separation by FSWT, and FSWT can be controlled adaptively in modal separation by dynamic scale method.