Overview of RF-based structural health monitoring of wind turbine blades

The structural health monitoring (SHM) of wind turbine blades is crucial for early failure identification, which subsequently reduces maintenance costs and ensures reliable operation in both onshore and offshore environments. Radio frequency (RF) and microwave radar technologies offer an effective non-contact and weather-resistant method for assessing wind turbine blade deflection. To achieve high-performance radar, various antenna types are offered in the literature, each with specific requirements and methodologies aimed at enhancing their performance to improve radar detection accuracy, such as high gain and narrow beam width. Among the different Doppler radars, Frequency Modulated Continuous Wave (FMCW) radar is preferred due to its enhanced spatial resolution, phase-based displacement sensitivity, and accurate fault localization. Additionally, radar performance can improve using advanced digital signal processing (DSP), improving signal strength, detection accuracy, and mitigating the multipath interference effect. This study examines RF-based solutions for wind turbine blade deflections, addressing various types of antennas, their placement on the blade at distinct frequencies (e.g., UWB and mmWave). It also tackles the primary limits of monitoring, including air attenuation, multipath effects, and resolution constraints. Challenges and future work for wind turbine monitoring based on RF were also mentioned. This overview establishes the fundamentals for the RF-based strategy in SHM of wind turbine blades.