Radial vibration measurements on rotors using laser vibrometry: a first practical solution to the cross-sensitivity problem

1998 ◽  
Author(s):  
John Bell ◽  
Steve J. Rothberg
Keyword(s):  
Radial Vibration ◽  
Laser Vibrometry ◽  
Vibration Measurements ◽  
Cross Sensitivity ◽  
Practical Solution ◽  
Sensitivity Problem ◽  
The Cross

A Modified Dual-Wavelength Matrix Calculation Method for Fiber Bragg Grating (FBG)

2012 ◽  
Vol 430-432 ◽  
pp. 1211-1214
Author(s):  
Xin Liu
Keyword(s):  
Fiber Bragg Grating ◽  
Calculation Method ◽  
Dual Wavelength ◽  
Fiber Sensor ◽  
Bragg Grating ◽  
Fiber Grating ◽  
Cross Sensitivity ◽  
Sensitivity Problem ◽  
The Cross ◽  
Matrix Calculation

Fiber grating is an optical passive device which is developed very fast in recent years. FBG is the most grating which is used as fiber sensor. Cross-sensitivity of fiber grating sensor is an important problem which is restricted the development of the fiber sensor. We do a deep research on the cross-sensitivity problem of the Fiber Bragg grating in this paper. Based on the basic principle of how the cross-sensitivity problem is produced, we suggest a modification in a dual-wavelength matrix calculation method which is used to solve the cross-sensitivity problem in traditional. The modified dual-wavelength matrix calculation method has a higher accuracy than the traditional method.

Application of Laser Vibrometry to Vibration Measurement on Rotating Components

1995 ◽  
Author(s):  
Steven J. Rothberg ◽  
Neil A. Halliwell
Keyword(s):  
Vibration Analysis ◽  
Laser Speckle ◽  
Vibration Measurement ◽  
Torsional Vibrations ◽  
Radial Vibration ◽  
Laser Vibrometry ◽  
Laser Doppler Vibrometry ◽  
Vibration Measurements ◽  
Speed Fluctuations ◽  
Fundamental Limitation

Abstract This paper describes the application of Laser Doppler Vibrometry to vibration measurements on rotating targets. The noise generating mechanism of the laser speckle phenomenon is first explained before confirmation of the insensitivity of measurements to target shape. The principal focus of the paper is on the fundamental limitation associated with the use of Laser Vibrometers for radial vibration measurements directly on rotating components. In such measurements significant cross-sensitivities to speed fluctuations, including torsional vibrations, and in-plane vibrations are evident, preventing synchronous vibration analysis. Mathematical and electronic means to resolve the correct orthogonal vibration components are presented and shown to be successful in enabling the use of Laser Vibrometry for non-synchronous vibration measurements.

scholarly journals Gravity-Based Characterization of Three-Axis Accelerometers in Terms of Intrinsic Accelerometer Parameters

2017 ◽  
Vol 122 ◽  
Author(s):  
Jon Geist ◽  
Muhammad Yaqub Afridi ◽  
Craig D. McGray ◽  
Michael Gaitan
Keyword(s):  
Gravitational Field ◽  
Coordinate System ◽  
Measurement Errors ◽  
Angle Measurement ◽  
Sensitivity Matrix ◽  
Cross Sensitivity ◽  
Measurement Capability ◽  
Intrinsic Parameters ◽  
The Cross ◽  
Alignment Errors

Cross-sensitivity matrices are used to translate the response of three-axis accelerometers into components of acceleration along the axes of a specified coordinate system. For inertial three-axis accelerometers, this coordinate system is often defined by the axes of a gimbal-based instrument that exposes the device to different acceleration inputs as the gimbal is rotated in the local gravitational field. Therefore, the cross-sensitivity matrix for a given three-axis accelerometer is not unique. Instead, it depends upon the orientation of the device when mounted on the gimbal. We define nine intrinsic parameters of three-axis accelerometers and describe how to measure them directly and how to calculate them from independently determined cross-sensitivity matrices. We propose that comparisons of the intrinsic parameters of three axis accelerometers that were calculated from independently determined cross-sensitivity matrices can be useful for comparisons of the cross-sensitivity-matrix measurement capability of different institutions because the intrinsic parameters will separate the accelerator-gimbal alignment differences among the participating institutions from the purely gimbal-related differences, such as gimbal-axis orthogonality errors, z-axis gravitational-field alignment errors, and angle-setting or angle-measurement errors.

Cross-Sensitivity Characteristics of Instrumented Wheelset Associated With Longitudinal Force and Lateral Contact Position

2021 ◽  
Author(s):  
Takatoshi Hondo ◽  
Takayuki Tanaka ◽  
Shoya Kuniyuki ◽  
Mitsugi Suzuki
Keyword(s):  
Measurement Accuracy ◽  
Contact Point ◽  
Fem Analysis ◽  
Longitudinal Force ◽  
Lateral Position ◽  
Contact Forces ◽  
Load Test ◽  
Static Load Test ◽  
Cross Sensitivity ◽  
The Cross

Abstract It is crucial to grasp wheel-rail contact forces in the evaluation of running safety and curving performance of railway vehicles. To measure the wheel-rail contact forces, instrumented wheelset, which has the strain gauges on the wheel surface, is widely used. The purpose of this research is to increase the measurement accuracy of the wheel-rail contact forces by understanding the detailed characteristics of the instrumented wheelset. Although the various researches on the instrumented wheelset have been carried out to increase the measurement accuracy of wheel-rail contact forces, there are few works considering the longitudinal force and the lateral shift of the wheel-rail contact point. However, sometimes the longitudinal force has a non-negligible influence on the measurement accuracy on the instrumented wheelset. In this paper, the authors clarify the cross-sensitivity characteristics of the instrumented wheelset when the longitudinal force is applied to the various lateral position on the wheel tread through the FEM analysis and the static load test. The authors also propose a method to approximate the cross-sensitivity as an analytical function of the lateral and circumferential contact positions.

scholarly journals Tilted Fiber Bragg Grating Sensor Using Chemical Plating of a Palladium Membrane for the Detection of Hydrogen Leakage

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4478 ◽  
Author(s):  
Jiachen Yu ◽  
Zhenlin Wu ◽  
Xin Yang ◽  
Xiuyou Han ◽  
Mingshan Zhao
Keyword(s):  
Fiber Bragg Grating ◽  
Low Cost ◽  
Hydrogen Sensor ◽  
Bragg Grating ◽  
Wavelength Shift ◽  
Cross Sensitivity ◽  
Chemical Plating ◽  
Palladium Membrane ◽  
Surrounding Refractive Index ◽  
The Cross

A tilted fiber Bragg grating (TFBG) hydrogen sensor coated with a palladium (Pd) membrane by the electroless plating method is proposed in this paper. A uniform layer of Pd metal is fabricated in aqueous solutions by the chemical coating method, which is used as the sensitive element to detect the change of the surrounding refractive index (SRI) caused by hydrogen absorption. The change in SRI causes an unsynchronized change of the cladding modes and the Bragg peak in the TFBG transmission spectrum, thereby eliminating the cross-sensitivity due to membrane expansion and is able to simultaneously monitor the presence of cracks in the pipe, as well as the hydrogen leakage. By subtracting the wavelength shift caused by fiber expansion, the change of SRI, i.e., the information from the H2 level, can be separately obtained. The drifted wavelength is measured for the H2 concentration below the hydrogen explosion limit between 1% and 4%. The chemical-based coating has the advantages of a low cost, a simple operation, and being suitable for coating on long fiber structures. The proposed sensor is able to detect the H2 signal in 5 min at a 1% H2 concentration. The proposed sensor is proved to be able to monitor the hydrogen level without the cross-sensitivity of temperature variation and expansion strains, so could be a good candidate for security applications in industry.

Study on Practical FBG Acceleration System

2011 ◽  
Vol 346 ◽  
pp. 546-550
Author(s):  
Wei Guang Zhang ◽  
Jian Zhang
Keyword(s):  
System Application ◽  
High Frequency ◽  
High Sensitivity ◽  
Acceleration Measurement ◽  
Cross Sensitivity ◽  
Loop Control ◽  
Sensitivity Problem ◽  
Micro Vibration ◽  
Low Sensitivity ◽  
Close Loop Control

A micro vibration, high sensitivity FBG demodulation system with close loop control is presented. By introducing a close loop control, the difficulty in matched FBG making process is overcame. Further more, the FBG strain-temperature cross sensitivity problem is settled. And low sensitivity in high frequency of cantilever FBG accelerator is overcame either. An example of the system application in acceleration measurement is introduced.

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