scholarly journals Development of a High-Resolution All-Fiber Homodyne Laser Doppler Vibrometer

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5801
Author(s):  
Jianhua Shang ◽  
Yan He ◽  
Qi Wang ◽  
Yilun Li ◽  
Lihong Ren
Keyword(s):  
High Resolution ◽  
Background Noise ◽  
Sound Pressure ◽  
Laser Doppler Vibrometer ◽  
Cost Effective ◽  
Pressure Level ◽  
Laser Doppler ◽  
Vibration Measurement ◽  
Calibration Experiment ◽  
Optic Communication

Based on the homodyne detection, a compact and cost-effective all-fiber laser Doppler vibrometer (LDV) with high resolution is presented. For the signal processing, the discrimination algorithm combined with the nonorthogonal correction is applied. The algorithm corrects the quadrature imbalance and other nonlinearity. In the calibration experiment, with the glass pasted on a piezoceramic transducer (PZT), the velocity resolution of 62 nm/s at 4 kHz and displacement resolution of 2.468 pm are achieved. For the LDV-based acousto-optic communication, the minimum detectable sound pressure level (SPL) reached 0.12 Pa under the hydrostatic air-water surface. The results demonstrate that the designed homodyne LDV has a low system background noise and can offer high precision in the vibration measurement.

Research on the Vibration Measurement Approach to the On-Line Noise Evaluation for Vehicle Transmissions

2012 ◽  
Vol 562-564 ◽  
pp. 1163-1167
Author(s):  
Feng Qiang Zhao ◽  
Guang Qiang Li ◽  
Hong Ying Hu ◽  
Jia Lu Du ◽  
Chen Guo
Keyword(s):  
Sound Pressure Level ◽  
Production Line ◽  
Background Noise ◽  
Sound Pressure ◽  
Sound Level ◽  
Pressure Level ◽  
Vibration Measurement ◽  
Vehicle Transmissions ◽  
Quality Of Transmission ◽  
Level Meter

At present, the common method of testing noise generated by vehicle transmission before delivery is to measure the noise sound pressure level by means of sound level meter. Since the measurement result is susceptible to background noise, the method can only be operated in anechoic chamber. In this paper, in order to measure sound pressure level directly on production-line, a new vibration measurement method and its relevant formula are presented. The proposed method can effectively avoid being affected by background noise and obtain the sound pressure level of transmission noise on production-line by testing the vibration acceleration signals of transmission box. It’s proved that the new method makes the delivery test of transmission noise more convenient and effective. Moreover, it can improve the delivery quality of transmission as well as the performance of whole vehicle.

Temperature coefficient of Young’s modulus of silver microwhiskers determined by a laser Doppler vibration measurement

2021 ◽  
pp. 2150350
Author(s):  
Yijun Jiang ◽  
Mingyuan Lu ◽  
Shiliang Wang ◽  
Han Huang
Keyword(s):  
Temperature Dependence ◽  
Temperature Coefficient ◽  
Single Crystals ◽  
Young’S Modulus ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Young's Modulus ◽  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Vibration Measurement

Temperature dependence of Young’s modulus of Ag microwhiskers was determined by a laser Doppler vibrometer. The Ag whiskers with diameters in sub-microns were synthesized by the use of physical vapor deposition (PVD). They have a five-fold twinned structure grown along the [1 1 0] direction. The temperature coefficient of Young’s modulus was measured to be [Formula: see text] ppm/K in the range of 300 K to 650 K. The measured values are very close to the reported values of [Formula: see text] ppm/K for bulk Ag single crystals. This finding can benefit the design of Ag-based micro/nano-electromechanical systems or micro/nano-interconnectors operated at elevated or lowered temperatures.

Heterodyne Laser Doppler Vibrometer for Underwater Acousto-Optic Communication

2009 ◽  
Vol 36 (1) ◽  
pp. 189-192
Author(s):  
计贺岩 He Yan ◽  
尚建华 Shang Jianhua ◽  
刘丹 LiuDan ◽  
贾宁 Jia Ning ◽  
臧华国 Zang Huaguo ◽  
...  
Keyword(s):  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Optic Communication

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

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Chong Yang ◽  
Yu Fu ◽  
Jianmin Yuan ◽  
Min Guo ◽  
Keyu Yan ◽  
...  
Keyword(s):  
Mode Shape ◽  
Natural Frequencies ◽  
Damage Identification ◽  
Reference Beam ◽  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Vibration Measurement ◽  
Mode Shapes ◽  
Interference Signal ◽  
Short Period

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.

scholarly journals Measuring Transverse Displacements Using Unmanned Aerial Systems Laser Doppler Vibrometer (UAS-LDV): Development and Field Validation

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6051
Author(s):  
Piyush Garg ◽  
Roya Nasimi ◽  
Ali Ozdagli ◽  
Su Zhang ◽  
David Dennis Lee Mascarenas ◽  
...  
Keyword(s):  
Laser Doppler Vibrometer ◽  
Field Tests ◽  
Field Measurements ◽  
Cost Effective ◽  
Laser Doppler ◽  
Unmanned Aerial Systems ◽  
Dynamic Displacement ◽  
Railway Bridges ◽  
Industrial Adoption ◽  
Aerial Systems

Measurement of bridge displacements is important for ensuring the safe operation of railway bridges. Traditionally, contact sensors such as Linear Variable Displacement Transducers (LVDT) and accelerometers have been used to measure the displacement of the railway bridges. However, these sensors need significant effort in installation and maintenance. Therefore, railroad management agencies are interested in new means to measure bridge displacements. This research focuses on mounting Laser Doppler Vibrometer (LDV) on an Unmanned Aerial System (UAS) to enable contact-free transverse dynamic displacement of railroad bridges. Researchers conducted three field tests by flying the Unmanned Aerial Systems Laser Doppler Vibrometer (UAS-LDV) 1.5 m away from the ground and measured the displacement of a moving target at various distances. The accuracy of the UAS-LDV measurements was compared to the Linear Variable Differential Transducer (LVDT) measurements. The results of the three field tests showed that the proposed system could measure non-contact, reference-free dynamic displacement with an average peak and root mean square (RMS) error for the three experiments of 10% and 8% compared to LVDT, respectively. Such errors are acceptable for field measurements in railroads, as the interest prior to bridge monitoring implementation of a new approach is to demonstrate similar success for different flights, as reported in the three results. This study also identified barriers for industrial adoption of this technology and proposed operational development practices for both technical and cost-effective implementation.

Noise Abatement From Large Size Electric Generators

2005 ◽  
Author(s):  
Wei Tong
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Near Field ◽  
Cost Effective ◽  
The United States ◽  
Pressure Level ◽  
Environmental Sound ◽  
Industrial Noise ◽  
Large Size ◽  
Electric Generators

Growing environmental sound concerns and recognition that lengthy unprotected exposure to high industrial noise levels can be detrimental to man have resulted in increased attention to reducing industrial noise. In the United States, it is required by law that all turbomachinery manufacturers must provide acoustic guarantees to their customers. For instance, for majority of generators, the near field sound pressure level is usually guaranteed not to exceed 85 dBA. To accomplish this goal, a number of methods of noise reduction have been developed in power industry. As one of the most practical and cost-effective solutions, acoustic blankets have been designed and tested for using on large size electric generators to efficiently reduce their sound pressure levels. This work has successfully demonstrated the potential of acoustic blankets for improve the passive acoustic transmission characteristics from generators. The acoustic data obtained from a field test have shown that the blankets can reduce the overall sound pressure level from large size generators about 4 to 6 dBA.

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