Harmonic Transfer Function to Measure Translational and Rotational Velocities With Continuous-Scan Laser Doppler Vibrometry

Yang, Shifei; Allen, Matthew S.

doi:10.1115/1.4026350

Cited by 14 publications

(10 citation statements)

References 13 publications

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“…Scanning the laser can increase laser speckle noise, so this application seeks to find a balance between the additional spatial information that CSLDV provides (in a reduced time) with increasing speckle noise. CSLDV typically increases speckle noise, but it has been shown to decrease the noise in some cases [37]. A schematic of the CSLDV process is shown in Fig.…”

Section: Special Solutionsmentioning

confidence: 99%

Laser Doppler Vibrometry Measurements in Structural Dynamics

Chiariotti¹,

Rembe²,

Castellini³

et al. 2020

Handbook of Experimental Structural Dynamics

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Laser vibrometry is a powerful tool for measurement of vibration on a variety of structures. Lasers do not mass-load or otherwise change the dynamics of a structure, and so they have enabled measurements from surfaces that are too light, delicate, hot, etc. to allow conventional surface mounted sensors. The position of the measurement point can also be changed readily. Thus, laser vibrometry has also allowed acquisition of measurements over a dense grid of points, to more completely characterize a structure its deformation shapes, the evolution of stress waves, or the identification of structural damages than it might be feasible with other methods. The chapter is divided in two sections: the first one is intended to provide an insight about the theory behind laser Doppler vibrometry (LDV), while the second section aims at giving an overview of the different types of laser Doppler vibrometers that have been developed so far. The chapter is not intended to give a comprehensive discussion of laser Doppler vibrometry, but it provides sufficient details about potentials, issues, and best practice approaches for successfully exploiting such technique in structural dynamics testing. References are provided to direct the interested reader to more detailed information as well as to examples of application cases.

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Section: Special Solutionsmentioning

confidence: 99%

Laser Doppler Vibrometry Measurements in Structural Dynamics

Chiariotti¹,

Rembe²,

Castellini³

et al. 2020

Handbook of Experimental Structural Dynamics

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show abstract

“…In order to investigate the stability of the proposed method, the number of target points from four to 12 was selected from Table 1 to calculate T and R. Indices of each group are (1,2,5,9), (1,2,5,6,9), (1,2,5,6,9,10), (1,2,3,5,6,9,10), (1,2,3,5,6,7,9,10), (1,2,3,5,6,7,9,10,11), (1,2,3,4,5,6,7,9,10,11), (1,…”

Section: Effects Of the Number Of Target Pointsmentioning

confidence: 99%

“…Giuliani et al [8] developed a new scanning device that can measure all six degrees of freedom at a measurement point with a LDV and a simple setup by combining various small circular scans. Yang and Allen [9] used a harmonic transfer function to process the continuous SLDV output of a downhill ski and obtain translational and rotational velocities with small circular scans.…”

Section: Introductionmentioning

confidence: 99%

Investigation of three-dimensional vibration measurement by a single scanning laser Doppler vibrometer

Chen

Zhu

2017

Journal of Sound and Vibration

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A scanning laser Doppler vibrometer (SLDV) has been widely used in noncontact vibration measurement. This paper presents a novel investigation of three-dimensional (3D) vibration measurement by a single SLDV sequentially placed at three different positions, where 3D vibration is defined as three vibration components along axes of a specified measurement coordinate system (MCS), which can give more precise knowledge of structural dynamic characteristics. A geometric model of the SLDV is proposed and a vibrometer coordinate system (VCS) based on the geometric model is defined and fixed on the SLDV. The pose of a SLDV with respect to a MCS is expressed in the form of a translation vector and a direction cosine matrix from the VCS to the MCS, which can be calculated by four or more target points with known coordinates in both the MCS and the VCS. An improved method based on the least squares method and singular value decomposition is proposed to obtain the pose of the SLDV. Compared with an inverse method, the proposed method can yield an orthogonal direction cosine matrix and be applicable to a two-dimensional (2D) structure. Effects of the number of target points on the accuracy and stability of the proposed method are investigated. With three direction cosine matrices of three different positions obtained by the proposed method, measured vibration velocities along laser line-of-sight directions can be transformed to vibration components along axes of the MCS. An experiment was conducted to measure 3D vibration

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“…This method was extended to output-only modal analysis to identify modal characteristics of a structure under unmeasurable broadband random excitation [19]. Yang and Allen [20] used a harmonic transfer function to process the CSLDV output of a downhill ski and obtain translational and rotational velocities with circular scans. Khan et al [21] applied the demodulation method to measure ODSs of various structures with surface cracks.…”

Section: Introductionmentioning

confidence: 99%

Damage Identification of Beams Using a Continuously Scanning Laser Doppler Vibrometer System

Chen

Zhu

2016

Journal of Vibration and Acoustics

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A continuously scanning laser Doppler vibrometer (CSLDV) system is capable of rapidly obtaining spatially dense operating deflection shapes (ODSs) by continuously sweeping a laser spot from the system over a structure surface. This paper presents a new damage identification methodology for beams that uses their ODSs under sinusoidal excitation obtained by a CSLDV system, where baseline information of associated undamaged beams is not needed. A curvature damage index (CDI) is proposed to identify damage near a region with high values of the CDI at an excitation frequency. The CDI uses the difference between curvatures of ODSs (CODSs) associated with ODSs that are obtained by two different CSLDV measurement methods, i.e., demodulation and polynomial methods; the former provides rapid and spatially dense ODSs of beams, and the latter provides ODSs that can be considered as those of associated undamaged beams. Phase variables are introduced to the two methods for damage identification purposes. Effects of the order in the polynomial method on qualities of ODSs and CODSs are investigated. A convergence index and a criterion are proposed to determine a proper order in the polynomial method. Effects of scan and sampling frequencies of a CSLDV system on qualities of ODSs and CODSs from the two measurement methods are investigated. The proposed damage identification methodology was experimentally validated on a beam with damage in the form of machined thickness reduction. The damage and its region were successfully identified in neighborhoods of prominent peaks of CDIs at different excitation frequencies.

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Harmonic Transfer Function to Measure Translational and Rotational Velocities With Continuous-Scan Laser Doppler Vibrometry

Cited by 14 publications

References 13 publications

Laser Doppler Vibrometry Measurements in Structural Dynamics

Laser Doppler Vibrometry Measurements in Structural Dynamics

Investigation of three-dimensional vibration measurement by a single scanning laser Doppler vibrometer

Damage Identification of Beams Using a Continuously Scanning Laser Doppler Vibrometer System

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