Operational Modal Analysis on Wind Turbine Hub

In this paper we present a dataset for Operational Modal Analysis (OMA) on a Vestas V112 wind turbine hub and illustrate how reliable Automatic OMA (AOMA) can be done on this structure. The chosen AOMA algorithm is called the Smallest Sphere Algorithm (SSA), and is based on the sliding filter stability diagram recently introduced by Olsen et al. We show how the SSA is able to identify all modes of the hub dataset reliable, including many closely spaced modes. The algorithm also successfully identifies two triple modes automatically. We show how a set of manually identified mode shapes compares to the Finite Element (FE) model. In this context it is discussed how the phenomenon of closely spaced modes is handled by rotating the identified modes into a basis defined by the FE model. A method for mode shape merging for multi setup testing is discussed.