以滑動模式為基礎之近場光碟機學習控制

Abstract

近場光碟機應用近場光學理論之飛行讀寫頭設計，突破了以往光碟機技術瓶頸，可以大幅的提高光碟片儲存容量和密度，然而光碟機讀寫的性能要求相對的提高。為了達成讀寫頭的尋軌，本研究提出結合滑動模式控制特性與重複學習控制特性，發展以滑動模式為基礎之重複學習控制。滑動模式對模型不確定性及外界干擾具有獨特的強健性。學習法則的補償項是使用形狀函數來趨近積分項中的影響函數，並且估測控制輸入。此類重複學習控制器能夠學習讀寫頭重覆尋軌動作所需之控制訊號輸入，從而增加重覆性尋軌動作的性能表現。設計此類控制器不需事先推導被控系統之動態模型，便可在每一取樣時間學習控制輸入值。本研究分別應用電阻和光學尺作位置迴授，以音圈馬達帶動光學讀寫頭從事尋軌控制之實驗，證明所提出之控制方法有效可行。

The flying head design in near-field optical disk drives applies the near-field optics theory to overcome the limit of conventional optical disk techniques, thereby substantially increasing data storage capacity. To that end, enhancing control performance to improve the tracking speed and accuracy is required. This study aims to develop a sliding mode based repetitive learning controller, which incorporates characteristics of sliding mode control into repetitive learning control. The reason for using sliding mode control is attributed to robust properties dealing with model uncertainty and disturbances. The learning algorithm utilizes shape functions to approximate influence functions in integral transforms and estimate the control input to perform seeking movement. It learns at each sampling instant the desired control input without prior knowledge of system dynamics. To validate the proposed method, this work conducts track-seeking experiments, in which a resistance device and an optical grating respectively read position feedback signals of the pickup head.