Natural Frequency Measurement of A 13-Meter Wind Turbine Blade Using Different Techniques

Nowadays the wind energy markets continue to grow to accommodate the current demands of renewable energy. As the wind turbine blades are susceptible to suffer damage from complex and irregular loading caused by catastrophes, development of quick and reliable ways for wind turbine health monitoring is becoming crucial. Modal testing is one of the most commonly used non-destructive health monitoring methods, as any damages could lead to changes in the structural vibration characteristics. In this paper, a series of modal tests were carried out to measure the natural frequencies of a 13 m wind turbine blade. Various data acquisition devices, namely the accelerometer, the laser vibrometer and the mobile phone sensor, were employed and the accuracy of the recorded accelerations and the corresponding Fast Fourier Transform (FFT) diagrams, were compared. The advantages and disadvantage of the employed techniques were discussed. It was found that all the three devices could capture the blade natural frequencies accurately, while the mobile phone sensor is recommended for a quick outdoor natural frequency testing under limited testing conditions.