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.

Fibre optic sensors for delamination identification in composite beams using a genetic algorithm

Abstract: Fibre Bragg grating (FBG) sensors associated with a genetic algorithm (GA) were used to detect and identify the size and location of delaminations in composite beams. A theoretical beam model is implemented into the GA for on-line delamination parameter searching. The objective function of this vibration-based delamination detection problem in the GA is defined as the sum of squared ratios of the differences between the shifts of eigenvalues of a delaminated beam measured by the FBG sensors and calculated from the theoretical beam model to the eigenvalues of an intact beam measured by the FBG sensors in the first three vibration modes. The principle of the FBG sensors for vibration detection is briefly discussed in this paper. A laser vibrometer and an accelerometer are utilized to compare the results measured from the FBG sensors. The reliability of using the FBG sensors for delamination detection is highlighted. Different delamination sizes and locations in spanwise and thickness-wise directions of the beams are simulated to demonstrate the feasibility of using the GA for the detection of delamination in the composite beams.

The Application of Tactile, Audible, and Ultrasonic Forces to Human Fingertips Using Broadband Electroadhesion

Abstract: We report an electroadhesive approach to controlling friction forces on sliding fingertips which is capable of producing vibrations across an exceedingly broad range of tactile, audible, and ultrasonic frequencies. Vibrations on the skin can be felt directly, and vibrations in the air can be heard emanating from the finger. Additionally, we report evidence from an investigation of the electrical dynamics of the system suggesting that an air gap at the skin/surface interface is primarily responsible for the induced electrostatic attraction underlying the electroadhesion effect. We developed an experimental apparatus capable of recording friction forces up to a frequency of 6 kHz, and used it to characterize two different electroadhesive systems, both of which exhibit flat force magnitude responses throughout the measurement range. These systems use custom electrical hardware to modulate a high frequency current and apply surprisingly low distortion, broadband forces to the skin. Recordings of skin vibrations with a laser Doppler vibrometer demonstrate the tactile capabilities of the system, while recordings of vibrations in the air with a MEMS microphone quantify the audible response and reveal the existence of ultrasonic forces applied to the skin via electronic friction modulation. Implications for surface haptic and audio-haptic displays are briefly discussed.

Measurement and analysis of rolling tire vibrations

Abstract: This paper presents the measurement and analysis of rolling tire vibrations due to road impact excitations, such as from cobbled roads, junctions between concrete road surface plates, railroad crossings. Vibrations of the tire surface due to road impact excitations cause noise radiation in the frequency band typically below 500 Hz. Tire vibration measurements with a laser Doppler vibrometer are performed on a test set-up based on a tire-on-tire principle which allows highly repetitive and controllable impact excitation tests under various realistic operating conditions. The influence on the measured velocity of random noise, cross sensitivity and alignment errors is discussed. An operational modal analysis technique is applied on sequential vibration measurements to characterise the dynamic behaviour of the rolling tire. Comparison between the operational modal parameters of the rolling tire and the modal parameters of the non-rolling tire allows an assessment of the changes in dynamic behaviour due to rolling.