Comparative performance assessment of methods for operational modal analysis during transient order excitation

Machinery with rotating components poses a challenge to Operational Modal Analysis (OMA) due its periodic inputs, i.e. orders. Transient (acceleration or deceleration) runs represent relevant test condition for structures, which experience low amount of broadband (noise) excitation during operation. In these cases, orders present themselves as favourable source excitation. However, this type can result in distortions the response spectrum at ending frequencies individual These “end-of-order” introduce spurious biased modal estimations. Order-based (OBMA) is an OMA method, was developed specifically transient case and not affected by end-of-order distortions. some downsides are associated OBMA because it performs analysis each order individually. addition effort, produces multiple sets estimations ambiguous results. This paper introduces extension address issues. The proposed called Averaged (AOBMA), applies scaling (weighted) averaging extracted prior estimation step. A Monte-Carlo simulation study introduced compare performance traditional OMA, AOBMA. Different ratios harmonic random amplitudes simulated gauge impact excitation's composition. addition, all methods also applied operational measurements from turbofan casing run-up. results indicate that AOBMA lower variance estimated parameters compared OBMA. Moreover, while more successful closely spaced modes, surpassed regarding accuracy mode shape