By analyzing the rotor structural dynamic response of a wind turbine, this research aims to improve decision making in operation and maintenance. To illustrate the potential of this measurement technique, a horizontal axis wind turbine test-bed is used to experimentally simulate the rotor structural dynamic response to uniform flow as well as horizontal and vertical shear flow across the rotor plane. The structural dynamic characteristics of the wind turbine rotor are described in the context of modal analysis where each mode of vibration occurs at a particular frequency with a particular modal deflection shape. These deflection shapes facilitate the effectiveness with which a given aerodynamic load couples into the rotor to produce mechanical power in addition to vibrations of the rotor. Operational modal analysis is used to explore the effects of changes in the wind state on the sensitivity of condition monitoring data to two types of damages in the turbine rotor, ice accretion and blade root cracking. Additionally, the degree to which various damage mechanisms can be identified in the presence of yaw and pitch set points is analyzed. It is shown that certain frequencies in the measured response using the flap, edgewise, and span directions of the wind turbine are sensitive to a change in condition of the rotor for use in detecting that type of damage. By analyzing the changes in the modal response amplitudes, the type of damage present in the rotor system can also be classified.

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