Towards airborne laser Doppler vibrometry for structural health monitoring of large and curved structures

Schewe, Marvin; Ismail, Mohamed A.A.; Rembe, Christian

doi:10.1784/insi.2021.63.5.280

Cited by 7 publications

(3 citation statements)

References 4 publications

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“…An LDV employs the optical coherent detection method and is widely used in industry, vehicles, robots, aerospace, biomedical field, etc. [2][3][4][5][6][7][8][9]. Compared with the contact sensors, the LDV attracts widespread attention because it enables non-contact measurements.…”

Section: Introductionmentioning

confidence: 99%

A Variable Carrier Generation for Heterodyne LDV with an Optical Phase-locked Loop

Gao,

Rembe

2024

J. Phys.: Conf. Ser.

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A heterodyne laser Doppler vibrometer (LDV) requires a frequency shifter to generate a carrier for the vibration information in the detector signal. The carrier frequency should be carefully selected in order to obtain the intended measurement range with a demodulation bandwidth that avoids existing noise sources. The traditional frequency shift in heterodyne LDV is realized with an acoustooptical modulator, which can only generate a fixed carrier frequency. In this paper, a variable carrier generation method based on an optical phase locked loop (OPLL) is demonstrated. Our setup implements a feedback loop to control the phase of the second laser to synchronize a reference laser. In lock-in status the carrier for the vibration information associated with a local oscillator signal. In this paper, we obtain the laser diode parameters relevant to performance and on the design of the photodetector and loop filter. Finally, the performance of the lock-in OPLL, variable carrier as well as velocity measurement is reported and the reliability of the proposed method is evaluated.

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Section: Introductionmentioning

confidence: 99%

A Variable Carrier Generation for Heterodyne LDV with an Optical Phase-locked Loop

Gao,

Rembe

2024

J. Phys.: Conf. Ser.

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“…Other scholars claimed that they have built a UAV-LDV system to achieve aerial testing. However, the utilization of the UAVs in these systems is limited to the placement of reflective targets [44], for the enhancement of the reflected laser intensity or the carriage of acoustic exciters [45], for the replacement of manual tapping, or carrying mirrors to reflect the laser light from stationary LDVs [46,47]. Their actual tests still rely on stationary LDVs, and the purported UAV-LDV systems have not been fully realized.…”

Section: Introductionmentioning

confidence: 99%

A Novel Debonding Damage Identification Approach of Hidden Frame-Supported Glass Curtain Walls Based on UAV-LDV System

Zheng,

Guo,

Zhi

et al. 2024

Applied Sciences

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This study introduces a novel Unmanned Aerial Vehicle-mounted (UAV-mounted) Laser Doppler Vibrometer (LDV) system for detecting debonding damage in Hidden Frame-Supported Glass Curtain Walls (HFSGCW). The established system enables UAVs to transport the LDV to high altitudes for operation. The vibration signals acquired by the UAV-LDV system are decomposed into different energy bands by wavelet packet analysis, and then the occurrence and location of the damage are identified by the Sum of Squared Differences (SSD) of the wavelet packet bands’ energy. This paper investigates the potential factors affecting the performance of the Unmanned Aerial Vehicle-Laser Doppler Vibrometer (UAV-LDV) system, including the arrangement of measuring points, measuring distance, noise level, and wind speed through the first-order natural frequency, the normalized frequency response functions, and the SSD indicator. Experimental and simulation results confirm the effectiveness of the UAV-LDV system, highlighting its advantages over traditional methods by offering remote, non-contact, and efficient debonding detection. This method not only indicates the presence of the damage, as traditional indicators do, but also pinpoints the exact location of it, ensuring safety and cost-effectiveness in high-rise inspections. The proposed method and indicator offer advantages in terms of convenience, visualization, and efficiency. The study discusses the impact of measurement point arrangement, measuring distance, noise levels, and wind speed on the system’s performance. The findings demonstrate that while the UAV-LDV system introduces new capabilities in rapid and reliable structural damage assessment, operational challenges such as wind and noise levels significantly influence its accuracy.

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“…Specifically, they provide valuable insights into potential strategies for mitigating turbulencerelated challenges, particularly in LDV applications deployed on drones. 9,10 Gibson et al observed fluctuations in the optical path length (OPL) with root mean square (RMS) values of around ∼ 0.2 µm over 1-meter optical path when wind speeds ranged from 1 m/s to 5 m/s. 11 Turbulence occurs within the optical path, and longer optical paths lead to more pronounced turbulence effects.…”

Section: Introductionmentioning

confidence: 99%

Measuring turbulence parameters with high precision through the smooth perturbation method

Tolchkova,

Rembe

2024

Optical Instrument Science, Technology, and Applications III

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The refractive index structure constant C 2 n and the microscale l 0 of turbulence contribute as crucial indicators of turbulence strength in a medium, such as the atmosphere. These parameters exert a substantial influence on measurements performed with Laser Doppler Vibrometry in an open atmosphere. Their significance becomes evident through variations in the phase characteristics of laser beams induced by outdoor turbulent phenomena, thereby impacting the precision and reliability of measurements. We discuss the measurement of turbulence parameters through application of the Rytov approximation using a specialized arrangement with laser Doppler vibrometers. In this paper, we investigate how this method allows deriving key turbulence parameters, such as the refractive index structure constant C 2 n and the inner scale of turbulence l 0 .

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Towards airborne laser Doppler vibrometry for structural health monitoring of large and curved structures

Cited by 7 publications

References 4 publications

A Variable Carrier Generation for Heterodyne LDV with an Optical Phase-locked Loop

A Variable Carrier Generation for Heterodyne LDV with an Optical Phase-locked Loop

A Novel Debonding Damage Identification Approach of Hidden Frame-Supported Glass Curtain Walls Based on UAV-LDV System

Measuring turbulence parameters with high precision through the smooth perturbation method

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