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Purpose <p>Operational modal analysis (OMA) with non-contact excitation is essential for determining modal parameters of delicate structures where physical contact may induce damage. This study aims to systematically compare two non-contact excitation techniques–air jet excitation and electromagnetic force generated by a coil with an iron core–in identifying the modal parameters of a thin cantilever rectangular plate, and to benchmark their performance against conventional contact excitation.</p> Methods <p>Modal parameters, including natural frequencies, damping ratios, and mode shapes, were estimated using three OMA techniques, with a particular focus on stochastic subspace identification (SSI-cov). The extracted parameters were validated against reference values obtained from experimental modal analysis (EMA). Uncertainty quantification was conducted via the delta method to evaluate the precision and robustness of each excitation method.</p> Results <p>The SSI-cov technique demonstrated superior accuracy, with modal parameter deviations remaining below 1% across all excitation types. Contact excitation produced the lowest standard deviation in natural frequencies (&lt;0.2 Hz), followed by electromagnetic excitation (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="42417_2025_2042_Article_IEq1.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(\le \)</EquationSource> <EquationSource Format="MATHML"><math> <mo>≤</mo> </math></EquationSource> </InlineEquation>0.3 Hz), whereas air jet excitation exhibited the highest uncertainty (up to 1 Hz).</p> Conclusion <p>Electromagnetic excitation was identified as the most reliable non-contact method, offering an optimal balance between structural safety and measurement precision. The findings provide practical guidelines for selecting excitation methods in the structural health monitoring of sensitive or fragile systems.</p>

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Non-contact Operational Modal Analysis of Thin Plates with Uncertainty Quantification of Identified Parameters: A Comparative Study

  • 期刊论文

  • 发表日期：

    2025年8月15日

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  • Marie Zaheri,
  • Morteza Karamooz Mahdiabadi

摘要

Purpose

Operational modal analysis (OMA) with non-contact excitation is essential for determining modal parameters of delicate structures where physical contact may induce damage. This study aims to systematically compare two non-contact excitation techniques–air jet excitation and electromagnetic force generated by a coil with an iron core–in identifying the modal parameters of a thin cantilever rectangular plate, and to benchmark their performance against conventional contact excitation.

Methods

Modal parameters, including natural frequencies, damping ratios, and mode shapes, were estimated using three OMA techniques, with a particular focus on stochastic subspace identification (SSI-cov). The extracted parameters were validated against reference values obtained from experimental modal analysis (EMA). Uncertainty quantification was conducted via the delta method to evaluate the precision and robustness of each excitation method.

Results

The SSI-cov technique demonstrated superior accuracy, with modal parameter deviations remaining below 1% across all excitation types. Contact excitation produced the lowest standard deviation in natural frequencies (<0.2 Hz), followed by electromagnetic excitation ( \(\le \) ≤ 0.3 Hz), whereas air jet excitation exhibited the highest uncertainty (up to 1 Hz).

Conclusion

Electromagnetic excitation was identified as the most reliable non-contact method, offering an optimal balance between structural safety and measurement precision. The findings provide practical guidelines for selecting excitation methods in the structural health monitoring of sensitive or fragile systems.