近場光碟機之讀取頭與碟片介面動態與反模式適應控制

Abstract

利用近場光學能解決資料儲存裝置日益增加的容量需求。為了近場讀寫需求，滑動片與光學碟片表面之間的距離，即飛行高度必須維持穩定。 在近場光碟機中，本研究使用一個壓電彎片作為實現飛行高度控制的致動器，設計一個包含壓電彎片的飛行讀寫頭，藉由搭配音圈馬達同時控制聚焦與尋軌。在外觀上，該讀寫頭的架構不同於傳統CD光碟機或DVD光碟機裡的讀寫頭架構，飛行讀寫頭非常靠近佈滿無數溝槽的光碟片表面。因此，讀取頭與光碟片之間的動態值得探討。不同於雷射都卜勒干涉儀，本文以光槓桿法使用兩個光感測器量測讀寫頭的飛行高度變化。最後，分別使用反模式適應控制及比例—積分—微分控制器進行對焦與尋軌╱循軌之控制。對焦與循軌的耦合於推導及電腦模擬中考慮。 本研究並且分析溝槽狀的表面對飛行的影響、實現讀取頭的飛行高度量測與控制、探討中性軸收縮對循軌的影響。就氣流干擾的消除而言，提出的方法，在模擬與實驗上證實有效。就模擬結果而言，提出的架構可以消除80%的氣流干擾，與傳統的反模式適應控制架構只能消除43%的干擾相比，明顯改善。就實驗結果而言，該架構可以減小追蹤誤差至13%，明顯優於傳統的反模式適應控制架構的27%追蹤誤差。

This study aims to realize near-field optics and solves the requirement of data increasing recording capacity. For near-field recording, the distance between the slider and optical disk surface, i.e. the flying height must maintain stable. As a flying height actuator, a piezoelectric bender is used to implement the flying height control in near-field optical disk drives. Firstly, this study designs a flying pickup head including a piezoelectric bender to complement VCM to control both focusing and track-seeking/track-following motions simultaneously. The pickup head structure differs from traditional CD-ROM and DVD-ROM pickup heads. Secondly, the pickup head is very close to an optical disk whose surface contains numerous grooves. Thus the dynamics between the optical disk and the pickup head must be investigated. Different from laser Doppler interferometers, an optical lever method using two quadrant photodetectors is developed to measure the flying height variation of a pickup head above a rotating disk. Finally, adaptive inverse control and PID control are used to implement focusing and track-following, respectively. Coupling between focusing and track-following is incorporated in derivation and computer simulation. This study analyzes the effect of grooved surface on flying, carries out experiments for flying height measurement and control with the pickup head, and investigates effects of horizontal deflection of the bender on track-following. For air bearing disturbance canceling, the proposed method is validated. Regarding simulation, dealing with air flow disturbance the previous method only cancels 43 %. By contrast, the proposed method can cancel disturbance up to 80 %. In experiments, the proposed method yields tracking error of 13 %, in contrast to 27 % by using the previous method.