A Contactless Laser Doppler Strain Sensor for Fatigue Testing with Resonance-Testing Machine

Wang, Fangjian; Krause, Steffen; Hug, Joachim; Rembe, Christian

doi:10.3390/s21010319

Cited by 7 publications

(4 citation statements)

References 35 publications

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“…For this purpose, we use an out-of-plane LDV in [29] and an in-plane LDV in [20,30]. Meanwhile, this in-plane LDV was built with signal diversity, whereby both photodetectors collected the light from orthogonal polarization states and stochastic independent detector signals were obtained (see in [20]).…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, our mathematical model can be applied not only to an out-of-plane LDV but also to an in-plane LDV. [20,30] with the mathematical model. Thus, the theoretical density functions 𝑓 𝐶𝑁 (𝐶𝑁) and 𝑓 𝐶𝑁 𝑐 (𝐶𝑁 𝑐 ) also agree with the experimental results 𝐶𝑁 𝑒𝑥𝑝 and 𝐶𝑁 𝑐,𝑒𝑥𝑝 .…”

Section: Aivela-2023mentioning

confidence: 99%

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Statistical behaviour of laser Doppler vibrometer detector signals and application of statistics for signal diversity

Wang,

Rembe

2024

J. Phys.: Conf. Ser.

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The problem of speckle noise and the so-called signal dropouts is well-known by many LDV sensors. Signal power is reduced when less light power is scattered into the detection aperture due to laser speckle. Signal dropouts occur when the carrier-to-noise ratio (C/N) of the photodetector signal falls below the frequency modulation (FM) threshold. This problem can be resolved with signal diversity. However, the influence of the speckle noise and signal dropouts has not been quantitatively analysed the state of the art. We introduce in this paper a new mathematical model of the statistical behaviour of detector signals of LDV sensors. This allows us to calculate the influence of speckle noise and signal dropouts on the detector signals of LDV sensors. Furthermore, we optimize the signal combination method of signal diversity according to the state of the art. Finally, we present some experimental results to prove our mathematical model and signal diversity for reducing speckle noise and signal dropouts.

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Section: Methodsmentioning

confidence: 99%

Section: Aivela-2023mentioning

confidence: 99%

Statistical behaviour of laser Doppler vibrometer detector signals and application of statistics for signal diversity

Wang,

Rembe

2024

J. Phys.: Conf. Ser.

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“…For the traditional heterodyne LDV, the reference beam is coherent with the measurement beam shifted by the Bragg cell. Since the optical path difference in the intended applications are rather short compared to the coherence length of a laser diode with even a relatively large linewidth, the realization of a reliable system has average requirements on the linewidth [19]. Most important for the OPLL is that the linewidth 𝛿𝑓 is lower than the modulation response bandwidth.…”

Section: Laser Requirementmentioning

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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“…However, it relies on cameras which are impractical at high rotation speeds because of their frames-per-second limit [8]. Laser Doppler velocimetry uses photo diodes instead of cameras, which would solve the speed issue but relies on positioning on a suitable speckle [9].…”

Section: Introductionmentioning

confidence: 99%

Uncertainty Analysis of an Optoelectronic Strain Measurement System for Flywheel Rotors

Rath

Schweighofer

Wegleiter

2021

Sensors

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The strain in a fast spinning carbon fiber flywheel rotor is of great interest for condition monitoring, as well as for studying long-term aging effects in the carbon fiber matrix. Optoelectronic strain measurement is a contactless measurement principle where a special reflective pattern is applied to the rotor which is scanned by a stationary optical setup. It does not require any active electronic components on the rotor and is suited for operation in a vacuum. In this paper, the influences of the key parts comprising the optoelectronic strain measurement are analyzed. The influence of each part on the measurement result including the uncertainty is modeled. The total uncertainty, as well as each part’s contribution is calculated. This provides a valuable assessment of requirements for component selection, as well as tolerances of mechanical parts and processes to reach a final target measurement uncertainty or to estimate the uncertainty of a given setup. We have shown that the edge quality of the special reflective pattern has the strongest influence, and how to improve it. Considering all influences, it is possible to measure strain with an uncertainty of less than 1% at a rotation speed of 500Hz.

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A Contactless Laser Doppler Strain Sensor for Fatigue Testing with Resonance-Testing Machine

Cited by 7 publications

References 35 publications

Statistical behaviour of laser Doppler vibrometer detector signals and application of statistics for signal diversity

Statistical behaviour of laser Doppler vibrometer detector signals and application of statistics for signal diversity

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

Uncertainty Analysis of an Optoelectronic Strain Measurement System for Flywheel Rotors

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