Deflection Monitoring of a Composite BladeUsing a Modal Approach Based ShapeEstimation Algorithm with FBG Sensors

Real-time deflection monitoring of a composite wind turbine blade was accomplished using the shape estimation algorithm with modal approach and strain data from embedded fiber Bragg grating (FBG) sensors. The finite element model of the composite wind turbine blade was created and the displacement-strain transformation (DST) matrix on the basis of the modal approach was obtained. The locations of the nine FBG strain sensors were optimized by minimizing the condition number of the displacement-strain transformation matrix. The deflection-monitoring test of the 11m span composite blade was conducted to verify the shape reconstruction algorithm and applicability of the FBG sensors in structural condition monitoring. The estimated shapes measured by embedded Bragg grating sensors are compared with the directly captured deflection shapes measured by stereo pattern recognition (SPR) cameras. The results confirm very close agreement showing the potentials of the proposed shape estimation technique using arrayed Bragg grating sensors.