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Wind loading from turbulence and gusts can cause damage in horizontal axis wind turbines. These unsteady loads and
the resulting damage initiation and propagation are difficult to predict. Unsteady loads enter at the rotor and are
transmitted to the drivetrain. The current generation of wind turbine has drivetrain-mounted vibration and bearing
temperature sensors, a nacelle-mounted inertial measurement unit, and a nacelle-mounted anemometer and wind vane.
Some advanced wind turbines are also equipped with strain measurements at the root of the rotor. This paper analyzes
additional measurements in a rotor blade to investigate the complexity of these unsteady loads. By identifying the
spatial distribution, amplitude, and frequency bandwidth of these loads, design improvements could be facilitated to
reduce uncertainties in reliability predictions. In addition, dynamic load estimates could be used in the future to control
high-bandwidth aerodynamic actuators distributed along the rotor blade to reduce the saturation of slower pitch actuators
currently used for wind turbine blades. Local acceleration measurements are made along a rotor blade to infer
operational rotor states including deflection and dynamic modal contributions. Previous work has demonstrated that
acceleration measurements can be experimentally acquired on an operating wind turbine. Simulations on simplified
rotor blades have also been used to demonstrate that mean blade loading can be estimated based on deflection estimates.
To successfully apply accelerometers in wind turbine applications for load identification, the spectral and spatial
characteristics of each excitation source must be understood so that the total acceleration measurement can be
decomposed into contributions from each source. To demonstrate the decomposition of acceleration measurements in
conjunction with load estimation methods, a flexible body model has been created with MSC.ADAMS© The benefit of
using a simulation model as opposed to a physical experiment to examine the merits of acceleration-based load
identification methods is that models of the structural dynamics and aerodynamics enable one to compare estimates of
the deflection and loading with actual values. Realistic wind conditions are applied to the wind turbine and used to
estimate the operational displacement and acceleration of the rotor. The per-revolution harmonics dominate the
displacement and acceleration response. Turbulent wind produces broadband excitation that includes both the harmonics
and modal vibrations, such as the tower modes. Power Spectral Density estimates of the acceleration along the span of
the rotor blades indicate that the edge modes may be coupled to the second harmonic.
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