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FEM AND EXPERIMENTAL ANALYSIS OF THE ACTUATOR ‘BUTTERFLY MODE’ IN A HARD-DISK DRIVE

✍ Scribed by X. LIU; J. LIU; C.K. LIM

Publisher
Elsevier Science
Year
2003
Tongue
English
Weight
452 KB
Volume
17
Category
Article
ISSN
0888-3270

No coin nor oath required. For personal study only.

✦ Synopsis

As the recording track density increases in hard-disk drives, the off-track error-rejection capability of the servo controller must also be increased. The high rejection capability is achieved by increasing the servo bandwidth; however, the ability to extend the bandwidth is limited by the actuator's structural resonance. One particular resonance mode of interest is the so-called 'butterfly mode' where it exhibits as the primary resonance with a 1808 phase in the structural (open-loop) transfer function plot. The factors influencing the butterfly mode were investigated using finite element analysis and confirmed by prototype testing. Although the mass-to-stiffness ratio in bearing cartridge pivot and the sway mode of the actuator structure by themselves were at a high enough frequency range, it was observed that the coupling effect in the pivot and actuator structure limited the frequency that it can be achieved. With the knowledge gained from the analysis, it is now possible to design an actuator to enable the high servo bandwidth required to follow track densities of more than 50 kilotracks per inch (kTPI) without the need for a dual-stage actuator.

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