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TECHNICAL PAPERS

Airflow-Housing-Induced Resonances of Rotating Optical Disks

[+] Author and Article Information
R. M. C. Mestrom

Department of Mechanical Engineering, Dynamics and Control Group, P.O. Box 513,  Eindhoven University of Technology, 5600 MB Eindhoven, the Netherlandsr.m.c.mestrom@tue.nl

R. H. B. Fey, H. Nijmeijer

Department of Mechanical Engineering, Dynamics and Control Group, P.O. Box 513,  Eindhoven University of Technology, 5600 MB Eindhoven, the Netherlands

P. M. R. Wortelboer, W. Aerts

Emerging Technologies and Systems,  Philips Optical Storage, P.O. Box 80002, 5600 JB Eindhoven, the Netherlands

J. Appl. Mech 74(6), 1252-1263 (Mar 16, 2007) (12 pages) doi:10.1115/1.2745356 History: Received April 24, 2006; Revised March 16, 2007

Numerous excitation sources for disk vibrations are present in optical drives. For increasing rotation speeds, airflow-housing-induced vibrations have become more and more important. Currently, drives are designed in which rotation speeds are so high that critical speed resonances may show up. The presence of these resonances depends on the layout of the inner housing geometry of the drive. The influence of the drive inner housing geometry is investigated systematically by means of a numerical-experimental approach. An analytical model is derived, containing disk dynamics and the geometry-induced pressure distribution acting as the excitation mechanism on the disk. The Reynolds’ lubrication equation is used as a first approach for the modeling of the pressure distribution. The model is numerically implemented using an approach based on a combination of finite element and finite difference techniques. An idealized, drive-like environment serves as the experimental setup. This setup resembles the situation in the numerical model, in order to be able to verify the numerical model. Wedge-like airflow disturbances are used in order to obtain insight into the influence of drive inner geometry on the critical speed resonances of optical disks. A disk tilt measurement method is designed that yields a global view of the disk deformation. By means of two newly proposed types of plots, numerical and experimental results can be compared in a straightforward way. A qualitative match between the numerical and experimental results is obtained. The numerical and experimental methods presented provide insight into airflow-housing-induced vibrations in optical drives. Additionally, reduction of some critical speed resonances is found to be possible for certain drive inner geometry configurations.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 17

Maximum absolute tangential tilt versus rotation frequency (solid line: reference; dashed line: two disturbances, 90deg apart

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Figure 18

Maximum absolute tangential tilt versus rotation frequency (solid line: reference; dashed line: two disturbances, 60deg apart; dashed-dotted line: two disturbances, 45deg apart

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Figure 1

Some examples of disk modes

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Figure 2

Campbell plot: natural frequencies in the body-fixed and Earth-fixed frames as a function of the rotation frequency

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Figure 3

Schematic representation of a flexible disk rotating above a rigid, fixed baseplate

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Figure 4

Schematic situation for the combined model

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Figure 5

Picture with parts of the idealized drive

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Figure 6

Schematic overview of the idealized drive

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Figure 7

Schematic overview of the projection method

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Figure 8

Examples of the camera view

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Figure 9

Campbell plot (for an Earth-fixed observer)

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Figure 10

Example of an avalanche plot: αt(ϕ,f) [mrad] (maxima: ▴; minima: ∘)

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Figure 11

Airflow disturbance configuration (a) and pressure difference (b) at a rotation frequency of f=120Hz. The pressure difference between the situation with and without disturbance is depicted in (c).

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Figure 12

Circumferential movement of the disk shape around the critical speed fc

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Figure 13

Maximum absolute tangential tilt αt,max(f) versus rotation frequency. Individual contributions of the (0,2), (0,3), and (0,4) mode are also indicated

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Figure 14

Simulation and experimental avalanche plot for the tangential tilt αt(ϕ,f) of the reference configuration

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Figure 15

Maximum absolute tangential tilt versus rotation frequency for the reference configuration

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Figure 16

Simulation and experimental avalanche plots for the configuration with two airflow disturbances, 90deg apart

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