Anti-shock air gap control for SIL-based near-field recording system

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

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


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.

Original languageEnglish
Article number4816008
Pages (from-to)2244-2247
Number of pages4
JournalIEEE Transactions on Magnetics
Issue number5
Publication statusPublished - 2009 May

Bibliographical note

Funding Information:
This work was supported by the Korea Science and Engineering Foundation through the Center for Information Storage Mechatronics grant R17-2008-040-01001-0. The authors would like to acknowledge the technical support kindly provided for their experiments by LG Corporation.

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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