A Continuous Scanning Laser Doppler Vibrometer for Mode Shape Analysis

La, Jongpil; Choi, Jieun; Hong, Jin-Pyo; Wang, Semyung; Kim, Kyoungsuk; Park, Kyihwan

doi:10.1016/s1474-6670(17)33986-1

Cited by 3 publications

(3 citation statements)

References 7 publications

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“…The dominating demerit is LDV which can only play a pointwise measurement as a single-pixel detector. For mode shape measurement, usually a scanning LDV (SLDV) [18] is adopted to measure the vibration on different spatial points. Ability of providing extremely high sampling density makes SLDV a popular metrical tool in damage identification [12,[19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Damage Identification by Using a Self-Synchronizing Multipoint Laser Doppler Vibrometer

Yang

Yuan

et al. 2015

Shock and Vibration

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The vibration-based damage identification method extracts the damage location and severity information from the change of modal properties, such as natural frequency and mode shape. Its performance and accuracy depends on the measurement precision. Laser Doppler vibrometer (LDV) provides a noncontact vibration measurement of high quality, but usually it can only do sampling on a single point. Scanning LDV is normally used to obtain the mode shape with a longer scanning time. In this paper, a damage detection technique is proposed using a self-synchronizing multipoint LDV. Multiple laser beams with various frequency shifts are projected on different points of the object, reflected and interfered with a common reference beam. The interference signal containing synchronized temporal vibration information of multiple spatial points is captured by a single photodetector and can be retrieved in a very short period. Experiments are conducted to measure the natural frequencies and mode shapes of pre- and postcrack cantilever beams. Mode shape curvature is calculated by numerical interpolation and windowed Fourier analysis. The results show that the artificial crack can be identified precisely from the change of natural frequencies and the difference of mode shape curvature squares.

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Section: Introductionmentioning

confidence: 99%

Damage Identification by Using a Self-Synchronizing Multipoint Laser Doppler Vibrometer

Yang

Yuan

et al. 2015

Shock and Vibration

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“…Although LDI gains above mentioned merits of owning a very high temporal sampling rate and requiring less on lighting condition, its primary demerit that normally only a point-wise measurement can be offered, restricts its use in practice. In order to overcome this problem, the scanning LDI [9] (SLDI) technique has been developed to measure different spatial points by quickly moving the laser beam on the testing surface. However, scanning is time-consuming thus the SLDI is unsuitable for unsteady phenomena, and the accuracy relies on the stability and repeatability of scanning device which utilizes mirrors to shift the laser beam.…”

Section: Introductionmentioning

confidence: 99%

Dynamic measurement via laser interferometry: crystal growth monitoring and modal parameter analysis

Yang

Fu²,

Zhao

et al. 2015

SPIE Proceedings

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“…Most of the vibrometric systems offer pointwise measurement; this becomes a main disadvantage of LDVs. To measure vibration at different points, a scanning system containing two orthogonal mirrors is normally adopted to move the measurement point rapidly and precisely on the testing surface [9]. This approach assumes that the measurement conditions remain invariant while sequential measurements are performed.…”

Section: Introductionmentioning

confidence: 99%

Multipoint laser Doppler vibrometry with single detector: principles, implementations, and signal analyses

Guo

Phua

2011

Appl. Opt.

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A 20-point laser Doppler vibrometer with single photodetector is presented for noncontact dynamic measurement. A 5×4 beam array with various frequency shifts is generated by a 1.55 μm distributed feedback laser and four acousto-optic devices, and illuminating different points on vibrating objects. The reflected beams are coupled into a single-mode fiber by a pigtailed collimator and interfere with a reference beam. The signal output from a high-speed photodetector is amplified and then digitized by a high-speed analog-to-digital converter with a sampling rate of 1 gigasample per second (1 GS/s). Several methods are introduced to avoid the cross talk among different frequencies and extract the vibration information of 20 points from a one-dimensional signal. Two signal processing algorithms based on Fourier transform and windowed Fourier transform are illustrated to extract the vibration signals at different points. The experimental results are compared with that from a commercial single-point laser vibrometer. The results show simultaneous vibration measurement can be realized on multiple points using a single laser source and a single photodetector.

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A Continuous Scanning Laser Doppler Vibrometer for Mode Shape Analysis

Cited by 3 publications

References 7 publications

Damage Identification by Using a Self-Synchronizing Multipoint Laser Doppler Vibrometer

Damage Identification by Using a Self-Synchronizing Multipoint Laser Doppler Vibrometer

Dynamic measurement via laser interferometry: crystal growth monitoring and modal parameter analysis

Multipoint laser Doppler vibrometry with single detector: principles, implementations, and signal analyses

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