MIMO-SAR Interferometric Measurements for Wind Turbine Tower Deformation Monitoring

Abstract

Deformations affect the structural integrity of wind turbine towers. The health of such structures is thus assessed by monitoring. The majority of sensors used for this purpose are costly and require in situ installations. We investigated whether Multiple-Input Multiple-Output Synthetic Aperture Radar (MIMO-SAR) sensors can be used to monitor wind turbine towers. We used an automotive-grade, low-cost, off-the-shelf MIMO-SAR sensor operating in the W-band with an acquisition frequency of 100 Hz to derive Line-Of-Sight (LOS) deformation measurements in ranges up to about 175 m. Time series of displacement measurements for areas at different heights of the tower were analyzed and compared to reference measurements acquired by processing video camera recordings and total station measurements. The results showed movements in the range of up to 1 m at the top of the tower. We were able to detect the deformations also with the W-band MIMO-SAR sensor; for areas with sufficient radar backscattering, the results suggest a sub-mm noise level of the radar measurements and agreement with the reference measurements at the mm- to sub-mm level. We further applied Fourier transformation to detect the dominant vibration frequencies and identified values ranging from 0.17 to 24 Hz. The outcomes confirmed the potential of MIMO-SAR sensors for highly precise, cost-efficient, and time-efficient structural monitoring of wind turbine towers. The sensors are likely also applicable for monitoring other high-rise structures such as skyscrapers or chimneys.

Enabling High-Resolution Micro-Vibration Detection Using Ground-Based Synthetic Aperture Radar: A Case Study for Pipeline Monitoring

“…The results obtained from MIMO radar interferometric processing were used as a benchmark and for comparison. Previous studies have shown that radar observations exhibit a high correlation with vision-based methods and accelerometers, with a maximum error of approximately 0.02 mm [5,7]. Our simulations revealed that while the resolutions of the AoA and vibration frequency improved with an increasing observation length, the resolution of the vibration amplitude remained at around 0.9 mm in our study.…”

“…Moreover, radar is insensitive to weather and lighting conditions and capable of penetrating through fog or smoke, thus significantly surpassing optical sensors [1]. As a result, studies in SHM are increasingly exploring radar remote sensing across various domains, including civil structures such as bridges [2] and buildings [3], tall structures such as towers [4] and wind turbines [5], cultural heritage [6], and industrial structures such as pipelines [7].…”

“…In fact, a higher operational frequency results in a more compact and lighter system and, as a result, simpler deployment [23]. However, these systems, due to their weak power, are suitable for monitoring a single object such as a building, bridge, or wind turbine [5,[29][30][31].…”

Wind Turbine Tower State Reconstruction Method Based on the Corner Cut Recursion Algorithm

“…In 2021, Paula Helming from the University of Bremen employed a ground-based laser scanner with a horizontal alignment line scanning mode to measure the tower and determined its axial and lateral deformation results through a least square fitting approach [12]. In 2023, Andreas Baumann-Ouyang from ETH Zürich used synthetic aperture radar to identify the tower's main frequency and to measure its deformation state [13]. These measurement methods require external auxiliary equipment and have high environmental requirements.…”

Study on the law of residual deformation in mining subsidence area and its influence on the safety of ground buildings

“…The method of monitoring surface displacement is usually used for the construction safety of goaf, as shown by Zhuang and Qu (2022). Andreas et al (2023) used MIMO-SAR sensors to provide accuracy and economy in structural displacement monitoring; Zhang et al (2023) proposed the Time-Series InSAR and Hurst Index method to provide a new idea for ground deformation monitoring; Ju et al (2023) adopted the TDT method to better eliminate the temperature delay effect; Ren et al (2023) proposed that the distributed optical fiber monitoring technology of Brillouin optical frequency domain analysis (BOFDA) has specific advantages in monitoring the excavation deformation of ultra-deep underground space; Ju et al (2023) adopted the TDT method to better eliminate the temperature delay effect. Some studies also provide methods to improve monitoring accuracy, such as the constrained total least squares (CTLS) method (Zhou et al, 2021), a novel robust AE/MS source location method (Rui et al, 2022a), a novel acoustic emission(AE) source localization method (Rui et al, 2022b).…”