Laser Doppler vibrometer

About: Laser Doppler vibrometer is a research topic. Over the lifetime, 6319 publications have been published within this topic receiving 76068 citations.

Piecewise-linear restoring force surfaces for semi-nonparametric identification of nonlinear systems

Abstract: A method for identifying a piecewise-linear approximation to the nonlinear forces acting on a system is presented and demonstrated using response data from a micro-cantilever beam. It is based on the Restoring Force Surface (RFS) method by Masri and Caughey, which is very attractive when initially testing a nonlinear system because it does not require the user to postulate a form for the nonlinearity a priori. The piecewise-linear fitting method presented here assures that a continuous piecewise-linear surface is identified, is effective even when the data does not cover the phase plane uniformly, and is more computationally efficient than classical polynomial based methods. A strategy for applying the method in polar form to sinusoidally excited response data is also presented. The method is demonstrated on simulated response data from a cantilever beam with a nonlinear electrostatic force, which highlights some of the differences between the local, piecewise-linear model presented here and polynomial-based models. The proposed methods are then applied to identify the force-state relationship for a micro-cantilever beam, whose response to single frequency excitation, measured with a Laser Doppler Vibrometer, contains a multitude of harmonics. The measurements suggest that an oscillatory nonlinear force acts on the cantilever when its tip velocity is near maximum during each cycle.

Computational Lamb wave model validation using 1D and 3D laser vibrometer measurements

Abstract: Lamb waves are being explored for structural health monitoring (SHM) due to their capability of detecting relatively small damage within reasonably large inspection areas. However, Lamb wave behavior is fairly complex, and therefore, various computational techniques, including finite element analysis (FEA), have been utilized to design appropriate SHM systems. Validation of these computational models is often based on a limited number of measurements made at discrete locations on the structure. For example, models of pitch-catch of Lamb waves may be validated by comparing predicted waveform time histories at a sensor to experimentally measured results. The use of laser Doppler vibrometer (LDV) measurements offers the potential to improve model validation. One-dimensional (1D) LDV scans provide detailed out-of-plane measurements over the entire scanned region, and checks at discrete sensor locations can still be performed. The use of three-dimensional (3D) laser vibrometer scans further expands the data available for correlation by providing in- and out-of-plane velocity components over the entire scanned region. This paper compares the use of 1D and 3D laser vibrometer data for qualitatively and quantitatively validating models of healthy metallic and composite plates.

Integral transmitter-receiver optical communication apparatus

Abstract: Disclosed is an integral transmitter-receiver optical communication apparatus, including: a transmitter-receiver device which includes: a transmitter having a laser source for emitting a laser beam modulated in accordance with a transmission information signal, a receiver having a position detecting sensor and a light receiving element which receive a complementing modulated laser beam transmitted from a complementing transmitter, and a beam splitting device for splitting the modulated laser beam and the complementing modulated laser beam which are incident thereon as two separate laser beams; a telescopic optical system for transmitting the modulated laser beam emitted by the laser source and for receiving the complementing modulated laser beam transmitted from the complementing transmitter; and a light beam deflecting device positioned between the telescopic optical system and the transmitter-receiver device, wherein the light beam deflecting device is controlled in accordance with a signal output from the position detecting sensor.

Multi-point differential laser doppler velocimeter using arrayed waveguide gratings with small wavelength sensitivity

Abstract: A multi-point laser Doppler velocimeter (LDV) using the arrayed waveguide gratings (AWGs) with small wavelength sensitivity (less than 1/10 of that for a conventional LDV without the AWGs) is proposed, in which velocities at different points in the depth direction can be simultaneously measured with compact optical systems. The design and characteristics of the proposed LDV are investigated with the model using the grating equation of the AWGs. From our simulation results, the wavelength sensitivity for multiple measured points can be reduced to less than 1/10 of that for a conventional LDV without an AWG.