P Jalali - Vibration and Modal Analysis Research Lab, Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran
S Varahram - Vibration and Modal Analysis Research Lab, Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran
R Hassannejad - Vibration and Modal Analysis Research Lab, Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran
M.H Sadeghi - Vibration and Modal Analysis Research Lab, Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran

According to the great importance of safety in aerospace industries, identification of dynamic parameters of related equipment by experimental tests in operating conditions has been in focus. Due to the existence of noise sources in these conditions the probability of fault occurrence may increases. This study investigates the effects of noise in the process of modal parameters identification by Output only Modal Analysis (OMA) method using Singular Value Decomposition (SVD) algorithm. The study case is the horizontal tailplane of the aircraft; therefore, at first, the modal parameters of the tailplane are obtained numerically. Then a cantilever beam is used to perform experimental tests with regard to the high aspect ratio of the modeled tailplane. The modal parameters of the beam are obtained nonparametrically by Experimental Modal Analysis (EMA) and OMA. In order to investigate the effects of noise in a controlled manner, the artificial excitation namely the shaker with the random force is used. Then, the effects of noisy measurements on the specifications of the system in EMA and OMA methods are investigated. The results indicate that: 1. The OMA method has more resistance against the noise for extracting natural frequencies. 2. The results of the Modal Assurance Criterion (MAC) values by EMA method, in the condition of noise existence in output data, are worse than the noise existence in input data. 3. The average of MAC values in general condition of EMA method by noisy input & output data is worse than the OMA method.

Output only modal analysis, Frequency domain decomposition, Finite Element, Singular value, Noise measurement