Operational Modal Identification of Time-Varying Structures via a Vector Multistage Recursive Approach in Hybrid Time and Frequency Domain

Si-Da Zhou,Li Liu,Wu Yang,Zhi-Sai Ma

doi:10.1155/2015/397364

Abstract

Real-time estimation of modal parameters of time-varying structures can conduct an obvious contribution to some specific applications in structural dynamic area, such as health monitoring, damage detection, and vibration control; the recursive algorithm of modal parameter estimation supplies one of fundamentals for acquiring modal parameters in real-time. This paper presents a vector multistage recursive method of modal parameter estimation for time-varying structures in hybrid time and frequency domain, including stages of recursive estimation of time-dependent power spectra, frozen-time modal parameter estimation, recursive modal validation, and continuous-time estimation of modal parameters. An experimental example validates the proposed method finally.

Highlights

In the real world, many engineering structures, such as trafficexcited bridges, launch vehicles with varying fuel mass, airplanes in flight with varying additional aerodynamic effects, deployable and flexible geometry-variable aerospace structures, and rotating machinery, show properties changing with time
The frozen-time modal parameters will be estimated by the frequency-domain method in the stage, so the selection of the frequency band is possible, which is an advantage of the frequency-domain methods over the time-domain methods
With the white-noise assumption, one of the fundamentals in the community of the operational modal analysis, the power spectra can be expressed by the right matrix fraction model as the same form as the representation of the frequency response functions

Summary

Introduction

Many engineering structures, such as trafficexcited bridges, launch vehicles with varying fuel mass, airplanes in flight with varying additional aerodynamic effects, deployable and flexible geometry-variable aerospace structures, and rotating machinery, show properties changing with time. Many time-domain parametric approaches of dynamic identification for time-varying structures were presented. Poulimenos et al [4, 5] estimated the modal parameters via the TARMA-based approaches and validated them with a laboratory experiment. In author’s previous work, the time-frequency-domain twostage least square method of modal parameter estimation for time-varying structures is presented [17], which can estimate the frequency and mode shapes well. This paper attempts to present a multistage recursive approach for the potential applications of real-time estimation methods of modal parameters in the hybrid time and frequency domain by choosing and reproducing the available time-domain and frequency-domain methods into the four sequential stages.

Design of the Multistage Recursive Estimator

Stage I

Stage III

Stage IV

Experiment

Conclusion