Anti-Shock Air Gap Control for SIL-Based Near-Field Recording System

Author

Kim, Jung-Gon ; Kim, Wan-Chin ; Hwang, Hyun-Woo ; Shin, Won-Ho ; Park, Kyoung-Su ; Park, No-Cheol ; Yang, Hyunseok ; Park, Young-Pil

Author_Institution

Center for Inf. Storage Device, Yonsei Univ., Seoul

Volume

45

Issue

5

fYear

2009

fDate

5/1/2009 12:00:00 AM

Firstpage

2244

Lastpage

2247

Abstract

The aim of this research is to improve the robustness of the air gap controller for solid immersion lens (SIL)-based near-field recording (NFR) servo systems against dynamic disturbances such as external shocks. Stable control is essential in these systems because the air gap distance between the SIL and the rotating disk is less than 100 nm. To detect gap error and read-out signals for the SIL and the disk, the air gap control performance must be increased to avoid collisions due to external shocks. We propose an anti-shock air gap control system using a disturbance observer (DOB) and a dead-zone nonlinear controller. Experimental results demonstrate that a DOB with a Q filter bandwidth of 500 Hz reduced the minimum air gap distance due to an external 1 g@10 ms shock by 70.1%. A DOB and a dead-zone nonlinear controller maintained the optical head distance for a 2 g@10 ms shock. Thus the control performance in the presence of external shocks was improved.

Keywords

air gaps; lenses; nonlinear control systems; observers; optical control; optical storage; servomechanisms; shock control; Q filter bandwidth; anti-shock air gap control system; bandwidth 500 Hz; dead-zone nonlinear controller; disturbance observer; dynamic disturbances; near-field recording servo systems; optical head; solid immersion lens; Anti-shock control; dead-zone nonlinear controller; disturbance observer (DOB); gap error signal (GES); near-field recording (NFR);

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/TMAG.2009.2016237

Filename

4816008