Using Diffused Fields for Monitoring the Structural Health of Wind Turbine Blades

Advances in wind turbine technologies will include increasing their reliability in order to decrease their cost. One important aspect of reliability is the downtime events that prevent a wind turbine from generating power. Improved health monitoring systems for wind turbine blades can provide wind farm operators with more information about the state of the blade in order to reduce downtimes associated with costly field inspections and repairs. A potential system for structural health monitoring is studied using the diffused fields present in the wind turbine blades caused by the consistent, stochastic, and natural excitation generated during operation. The Green's function can be reconstructed from the recorded signals of two passive sensors placed within the diffuse field. In the case at hand, the reconstructed coherent signal contains multimodal and dispersive waves. Here we demonstrate the method through experimental tests on a CX-100 wind turbine blade located at the UCSD Powell Structural Laboratories. Impulse and random excitation experiments were performed on a skin section of the blade in the max chord region. The results show a strong comparison between the measured Green's function and the reconstructed Green's function from the diffused field.