A Study of VCM-Type Vibration Absorber in Optical Disk Drive
|關鍵字:||吸振器;音圈馬達;光碟機;vibration absorber;voice coil motor;optical disk drive|
Unbalanced disks in rotation will lead to main vibration of an optical disk drive. Passive vibration absorbers are usually used in current optical disk drives to suppress vibration. Generally, optical disk drives have to make a disk spin at multiple speeds by different read/write conditions. However, the passive vibration absorber only suppresses vibration at a specific rotating speed and may excite vibration at other speeds. This study aims to investigate an active vibration absorber to reduce disk drive vibration at multiple rotating speeds using an effective control. In addition to the basic absorber as a passive device, a voice coil motor serves to actively control vibration. In this study, combining passive and active devices is named as a voice coil motor type vibration absorber. The derived mathematical model depicts the advantage of an active vibration absorber. For reducing vibration of the traverse, corresponding to the disk speed, required electrical voltages in a voice coil motor type vibration absorber are calculated as the control system input. Using voice coil motors makes optical disk drives more stable and robust at multiple speeds. A function generator generates sinewave signal, which actuates the active absorber through a power amplifier. The vibration of a disk drive at different rotating speeds is measured by a laser Doppler vibrometer. Experimental results show that a suitable actuating amplitude and a rotating speed nearby actuating frequency lead to effective vibration reduction of a voice coil motor type vibration absorber. This study investigates vibration reduction by the vibration absorber with a linear quadratic Gaussian method in the closed-loop control. Simulation and experimental results show that a voice coil motor type vibration absorber effectively decreases vibration of an optical disk drive at different operating speeds. A data acquisition hardware and a personal computer act as a controller of the vibration absorber in experiments. Moreover, this study proposes a method to design a voice coil motor type vibration absorber. A better voice coil motor type vibration absorber performance, such as low average consumption power, can be achieved by tuning the wire diameter of a coil, the thickness of the permanent magnet, and coil spaces. In design procedure it also needs to consider allowable currents and voltages in this system. The force constant and the coil inductance of the voice coil motor are obtained by the finite element method simulation. Then, the average consumption power is computed from the Kirchhoff’s voltage law and dynamic equations. This study demonstrates the performance of this proposed vibration absorber.