Dynamic Parameter Identification Using Ambient Response Analysis and Ibrahim Time Domain Approach: A Case Study on a Steel Plate Structure

Abstract

Since the level of vibration always depends on the natural frequencies of the system, it is important to know the modal parameters of such system to control failure and provide prevention actions. However, for many mechanical engineering machines or structures, there is a demand and necessity to determine real-life modal parameters using actual operating condition. This type of testing condition cannot be done in lab environment because most of the mechanical structure is big in size and heavy. Thus, the purpose of this paper is to study the natural frequencies of a steel plate by using Operational Modal Analysis (OMA) and Ibrahim Time Domain (ITD). Comparison of results between both approaches will be shown.

Constrained mode decomposition method for modal parameter identification

“…The six responses are subjected to the FFT to obtain the six-element frequency-domain response vector Y ω ð Þ as in Equation (7). Note that the frequency resolution is defined by the length of the responses y i t ð Þ, so that it is slightly worse than that of the original 10-s-long signal.…”

“…Classical modal parameter identification methods are usually formulated and operate in time domain or in frequency domain. Time-domain methods include the widely used eigensystem realization algorithm (ERA) [1][2][3] and autoregressive moving average (ARMA) models, [4][5][6] the Ibrahim time domain (ITD) approach, 7,8 and stochastic subspace identification (SSI) method. [9][10][11] Frequency-domain methods include the simplest peak picking method, 12 maximum likelihood identification, 13 and the frequency-domain decomposition method.…”

Operational Modal Analysis of Damage Gear

“…Frequency Domain Decomposition (FDD) is a nonparametric method extended from the Basic Frequency Domain (BFD) technique [8]. It does not depend on any type of curve fitting from parametric modelling and was well explained by [7], [9]. It was shown to be very good technique in the study on the turbine wind where excellent results for natural frequencies and mode shapes were obtained.…”