Automotive lidars for rotating wind turbine blade monitoring

Abstract. Permanently integrated sensor systems, such as strain gauges and fiber optic sensors, are the predominant means of measuring deflection in full-scale wind turbine blades. However, these approaches suffer from several key limitations, including complex calibration procedures, labor-intensive installation, and the inability to repair sensors once the blade structure is sealed. Furthermore, they are severely limited in measuring torsional deformation, a parameter of increasing importance for large wind turbine blades. To address these limitations, this study presents a novel non-contact monitoring framework based on a synchronized array of three automotive-grade lidars, enabling full-scale measurement of blade deflection and torsional deformation under diverse operating conditions. Lidar-derived flapwise deflection measurements (sampled at 33.3 Hz) are validated against co-located strain gauge data acquired at 1.4 m from the rotor plane center (sampled at 50 Hz), while lidar-based pitch angle estimates are validated against SCADA measurements after both signals are resampled to 2 Hz. The measured blade torsional deformation reaches approximately 0.8° under above-rated wind speed conditions, consistent with expected aerodynamic behavior. The dependence of median flapwise deflection on mean hub-height wind speed, rotor azimuth angle, and wind shear is also systematically analyzed. The results demonstrate that the proposed lidar-based system can accurately capture both flapwise deflection and pitch deformation along the blade span. These findings highlight the potential of cost-effective automotive lidar sensors for reliable, high-resolution monitoring of wind turbine structural dynamics under challenging field conditions.