Taking laser Doppler vibrometry off the tripod: correction of measurements affected by instrument vibration

Halkon, Ben J.; Rothberg, Steve

doi:10.1016/j.optlaseng.2016.11.006

Cited by 20 publications

(34 citation statements)

References 7 publications

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“…Meanwhile, at very low frequencies, seismic applications [125] have incentivised development of a technique to compensate for instrument vibration [126], recognising that LDVs, for all the successful applications, actually measure relative rather than absolute motion. Expectations remain high for the next 30 years in which many predict that multi-channel measurements will open up a new chapter in the story of LDV.…”

Section: Discussionmentioning

confidence: 99%

An international review of laser Doppler vibrometry: Making light work of vibration measurement

Rothberg

Allen

Castellini

et al. 2017

Optics and Lasers in Engineering

324

153

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In 1964, just a few years after the invention of the laser, a fluid velocity measurement based on the frequency shift of scattered light was made and the laser Doppler technique was born. This comprehensive review paper charts advances in the development and applications of laser Doppler vibrometry (LDV) since those first pioneering experiments. Consideration is first given to the challenges that continue to be posed by laser speckle. Scanning LDV is introduced and its significant influence in the field of experimental modal analysis described. Applications in structural health

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Section: Discussionmentioning

confidence: 99%

An international review of laser Doppler vibrometry: Making light work of vibration measurement

Rothberg

Allen

Castellini

et al. 2017

Optics and Lasers in Engineering

324

153

View full text Add to dashboard Cite

show abstract

“…To combat the issue of pseudo-vibration caused with the movement of the vibrometer, additional measurements to determine its movement need to be done. Halkon and Rothberg proved with laboratory and some real-world measurements that with placement of only 2 additional uni-axial accelerometers on the housing of the vibrometer the error caused by the movement of the device in the direction of the laser beam can be extracted [30]. The mathematical procedure and laboratory measurements where the procedure was validated are in detail described in the aforementioned paper [30].…”

Section: Methodsmentioning

confidence: 99%

“…Halkon and Rothberg proved with laboratory and some real-world measurements that with placement of only 2 additional uni-axial accelerometers on the housing of the vibrometer the error caused by the movement of the device in the direction of the laser beam can be extracted [30]. The mathematical procedure and laboratory measurements where the procedure was validated are in detail described in the aforementioned paper [30]. Here, we will focus on the application in the powerhouse and the issues concerning measurements out of laboratory conditions.…”

Section: Methodsmentioning

confidence: 99%

“…The placement of the corrective accelerometers has to be precise, and in order to smooth the error caused by the rigid body tilt of the vibrometer, accelerometers have to be placed on one of the diagonals and perfectly symmetrically to the origin of the laser beam, i.e., mirrored where the y,z location components should be (y1,z1)=−(y2,z2) and also y1=z1 and y2=z2, where y=0 and z=0 represent the origin of the laser beam (see Figure 1). The precise installation is very important; a 1 mm imperfection in the position causes an error of π360 mm/s and an angle misalignment causes a 1% error per degree of misalignment [30].…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

On the Application of Laser Vibrometry to Perform Structural Health Monitoring in Non-Stationary Conditions of a Hydropower Dam

Klun

Zupan

Lopatič

et al. 2019

Sensors

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This paper presents the first application of the Laser Doppler Vibrometer (LDV) in non-stationary conditions within a hydropower plant powerhouse. The aim of this research is to develop a methodology to include non-contact vibration monitoring as part of structural health monitoring of concrete dams. We have performed in-situ structural vibration measurements on the run-of-the-river Brežice dam in Slovenia during the start-up tests and regular operation. In recent decades, the rapid development of laser measurement technology has provided powerful methods for a variety of measuring tasks. Despite these recent developments, the use of lasers for measuring has been limited to sites provided with stationary conditions. This paper explains the elimination of pseudo-vibration and measurement noise inherent in the non-stationary conditions of the site. Upon removal of the noise, fatigue of the different structural elements of the powerhouse could be identified if significant changes over time are observed in the eigenfrequencies. The use of laser technology is to complement the regular monitoring activities on large dams, since observation and analysis of integrity parameters provide indispensable information for decision making and maintaining good structural health of ageing dams.

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“…LDV is a technique that has built its reputation on real world measurements with high accuracy. The practical steps proposed in this paper, like those proposed in a recent study of the effects of vibration of the instrument itself [6], are essential to restoring that accuracy in the kind of challenging applications that are the trademark of LDV and represent a significant and important contribution to the vibration engineering community.…”

Section: Introductionmentioning

confidence: 99%

Restoring high accuracy to laser Doppler vibrometry measurements affected by vibration of beam steering optics

Halkon

Rothberg

2017

Journal of Sound and Vibration

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Laser Doppler vibrometers are now well-established as an effective non-contact alternative to traditional contacting transducers. Wide-ranging applications include those where beam steering optics are required to reach locations that are difficult to access but no attention has yet been given to measurement sensitivity to the vibration of those optics. In this paper, a thorough mathematical treatment of this sensitivity to steering optic vibration and its correction is set out. A very practical scheme requiring a single correction measurement, from the back-surface of the mirror at the incidence point and aligned with the mirror normal, delivers an error reduction typically in excess of 30 dB. After validation in the laboratory, the scheme is then applied to a genuinely challenging measurement scenario on a single cylinder racing motorcycle. Correction is theoretically perfect for translational mirror vibrations but angular mirror vibrations require an adapted scheme using a triplet of accelerometers arranged around a circular path on the mirror back-surface and this is set out theoretically.

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Taking laser Doppler vibrometry off the tripod: correction of measurements affected by instrument vibration

Cited by 20 publications

References 7 publications

An international review of laser Doppler vibrometry: Making light work of vibration measurement

An international review of laser Doppler vibrometry: Making light work of vibration measurement

On the Application of Laser Vibrometry to Perform Structural Health Monitoring in Non-Stationary Conditions of a Hydropower Dam

Restoring high accuracy to laser Doppler vibrometry measurements affected by vibration of beam steering optics

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