Validation of Vibro-Acoustic Modulation of Wind Turbine Blades for Structural Health Monitoring Using Operational Vibration as a Pumping Signal

Abstract

This paper presents a crack detection technique for wind turbine blades using Vibro-Acoustic Modulation. The technique identifies nonlinear characteristics of a blade by utilizing the wind turbine operational vibration as a pumping signal. The theory underlying the technique is described and an experiment with a 900 watt smallscale wind turbine is conducted using a wind tunnel. Two other conventional VibroAcoustic Modulation tests were also performed with same blades to compare the results from these offline tests with the proposed online Vibro-Acoustic Modulation test using the turbine operational vibration as the pumping signal. It is shown that the structural vibration of the blades during operation lead to identical trends in the measured Vibro-Acoustic Modulation spectra for the cracked blade as the case in which the impact and piezoelectric actuator narrowband pumping signals are used.