Automated transmissibility based operational modal analysis for continuous monitoring in the presence of harmonics

Through Operational Modal Analysis (OMA) the modal parameters of an operational structure can be monitored over its lifetime. In recent years several interesting applications have illustrated this concept and it has been applied successfully at different locations across Europe. However, one of the disadvantages of most OMA techniques is the poor estimation and reliability in the presence of (varying) harmonics, e. g. due the passing blades of a wind turbine. Therefore, it is very hard to monitor the modal parameters of these structures using classic OMA-techniques. TOMA, OMA based on transmissibility functions, is potentially uninfluenced by these harmonics and could therefore resolve this limitation of OMA. This paper will discuss the differences between the automation of classic OMA and automating TOMA. It will suggest a strategy to achieve a fully automated TOMA approach that is uninfluenced by the harmonics present in the measured vibrations.