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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.


Papers
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Journal ArticleDOI
TL;DR: In this article, a PZT gripper with a piezoelectric (PZT) stack and flexible mechanism is presented, and an input-shaping algorithm is applied to restrain the residual vibration caused by the flexible structure.
Abstract: A microgripper capable of accurately releasing or clamping the microgold wire for ultrasonic bonding is a key component in integrated circuit and light-emitting diode wire bonders. A novel gripper with a piezoelectric (PZT) stack and flexible mechanism is presented. A dynamic model of the PZT gripper is established, and a method of suppression control for residual vibration is proposed. The vibration characteristics of the PZT gripper are calculated using finite-element modeling (FEM) to obtain the natural frequency, vibration mode, and displacement. An input-shaping algorithm is applied to restrain the residual vibration caused by the flexible structure. The performance of the control algorithm is discussed and compared to the performance of the square, trapezoidal, and synthetic control methods. Three typical input-shaping filters—zero vibration, zero vibration differential, and extreme insensitivity—are compared, and the effects of frequency and damping on vibration suppression are discussed. In the experiment, a high-speed camera is used to track the displacement of the gripper, and the relationship between displacement and driven voltage is proven. Impedance and frequency are measured by an impedance analyzer, and the results agree with the values from the FEM. The residual vibration with the different driver control methods is recorded by a noncontact laser Doppler vibrometer. With the input-shaping control method, the residual vibration of the PZT gripper is reduced to 10%, and the settling time is reduced by 0.7 ms compared to the original vibration, demonstrating that the method improves the performance of the PZT gripper.

27 citations

Patent
20 Dec 2002
TL;DR: In this paper, a line laser assembly including a laser and emitting a laser beam line and an electronic target assembly, including a photo detector array, is used for laser alignment at a distance of 10 feet.
Abstract: A laser alignment tool includes a line laser assembly including a laser and emitting a laser beam line and an electronic target assembly including a photo detector array. The laser beam line of the laser is pointed toward the center of the photo detector array with the longitudinal axis of the laser beam line being perpendicular to the centerline of the photo detector array. The line laser assembly includes a laser diode having a line-generating lens attached in front using a lens holder and being mounted onto a tilt stage. Using a line laser provides a certified accuracy of +/−0.005 inches at a distance of 10 feet. The electronic target further includes a narrow band pass filter and a discrete LED display that is controlled by a microprocessor. The microprocessor may be programmed with a variable range for each LED of the discrete LED display according to the alignment task.

27 citations

Journal ArticleDOI
TL;DR: This paper describes the application of a tracking laser Doppler vibrometer (TLDV) for vibration measurements on automotive components and the advances in data processing.
Abstract: This paper describes the application of a tracking laser Doppler vibrometer (TLDV) for vibration measurements on automotive components and the advances in data processing. A Lagrangian approach is adopted: the target point moves continuously and it is tracked by the measurement laser spot, thus no relative velocity between the target and the laser spot exists. By eliminating the relative motion of the laser beam on the surface, speckle noise is drastically reduced. Measuring on a moving reference frame opens an innovative way to look at automotive component vibrations, because the space-time evolution of the vibration can be measured under simulated operative conditions. After a presentation and discussion of the measurement technique, attention is focused on three different applications in the automotive field: the side-wall vibration of a rolling tyre, the out-of-plane vibration of a timing belt and the rubber blade vibration of complex motion windscreen wipers. The development of optimized TLDV measurement systems for each specific application is shown and some results are presented. Vibration data have been analysed in both the time and frequency domains. Moreover, in order to point out time-dependent frequency features in signals, vibration data have been further processed by means of joint time-frequency algorithms.

27 citations

Journal ArticleDOI
Run-Han Wang1, Vasant Nayak1, Fu-Ying Huang1, Wade Tang1, Francis Chee-Shuen Lee1 
TL;DR: In this article, the magnetic signal was used to identify both the vertical spacing modulation due to the air bearing modes and off-track jitter due to suspension modes with nanometer resolution.
Abstract: To achieve an areal density approaching 50 Gb/in. 2 for the magnetic storage of data in hard disk drives requires reduced mechanical and magnetic spacing. Off-track jitter caused by airflow or contact can cause track misregistration on the order of 20-70 nm which may be excessive for adequate servo performance. The magnetic signal can be used to identify both the vertical spacing modulation due to the air bearing modes and off-track jitter due to suspension modes with nanometer resolution. We find that the off-track jitter in the flying regime is driven by airflow and is a strong function of the disk velocity and the suspension type. In the contact regime, the vertical spacing modulation and off-track jitter increase due to contact. Using a laser Doppler vibrometer we identified the leading contribution to the off-track jitter to be primarily the first torsional mode (T1) and to a lesser extent the first bending mode (B1) of the suspension.

27 citations

Journal ArticleDOI
TL;DR: In this paper, a simple and inexpensive optical fiber vibrometer with reflectivity and illuminating power compensation is presented, which consists of a light emitting diode, an optical fibre probe and two photodetectors.
Abstract: In this paper, a simple and inexpensive optical fibre vibrometer with reflectivity and illuminating power compensation is presented. It consists of a light emitting diode, an optical fibre probe and two photodetectors. The bundling of the probe is divided into three parts: an illuminating fibre, the first-neighbour receiving fibres (group A) and the second-neighbour receiving fibres (group B). The ratio of mean values of the output signal from group A to that from group B is dependent on the mean distance between the probe and target surface, and is independent of the reflectivity of the target surface and illuminating power. By using this ratio, the mean distance between the probe and target surface is estimated. Then based on the calibration curve of group A or B, compensation of sensitivity is made. Because mean values of the photodetector outputs are used in ratio calculation, an increase in vibration frequency does not limit the application of this ratio technique. For this reason, this method is suitable for dynamic measurement. Results of experiments show that this optical fibre vibrometer is capable of compensating for target surface reflectivity, illuminating power and the mean distance between the probe and target surface.

27 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202381
2022177
2021122
2020142
2019134
2018174