應用免疫法則於壓電管雙方向之控制

Abstract

隨著高密度的儲存需求，近場光碟機的開發與設計是值得重視 的；近場光碟機為了滿足近場光學的需求，必須接近碟片反射面約 50 奈米處進行讀寫的動作。由於讀寫頭飛行時，受到碟片轉動造成 的空氣動力與側向風切干擾，和系統模型的誤差、外界干擾等影響， 控制器必須具強健性才不至於失效。 本研究提出在近場光碟機中，利用壓電管作為飛行讀寫頭的雙軸 致動器，進行飛行讀寫頭的對焦和尋軌雙方向的控制，進而使用免疫 法則以改善控制器的強健性及適應性。免疫法則主要分為下列步驟： 抗原的辨識與規劃、抗原結合與呈現、抗體形成免疫網路、與免疫反 應動作。在抗體規劃部分，本研究模擬時將抗原涵蓋尋軌時資料軌的 誤差，與對焦時外在環境的干擾，並定義抗體進行免疫反應，以達到 控制器的強健性。實驗時則將碟片轉動所造成的變形定義為抗原，並 針對不同抗原的特定PID 控制增益，建立免疫資料庫來實現免疫法則 控制，雙軸控制結果顯示當追蹤時半徑500 nm 的圓時，軌跡之閉路 控制精度是5 %。

To pursue high recording density of optical storage systems, near-field optical disk drives represent a promising device. In order to meet requirements of near-field optics, a flying pickup head in near-field optical disk drives has to fly stably around 50 nm above a disk surface so as to read/write disk data. Subject to air bearing runout, lateral windage, modeling error, and disturbance, the controller has to be robust. This work proposes to employ a dual-axis piezotube actuator for the flying pickup head of near-filed recording. This study uses an immune algorithm to improve control robustness for the piezotube actuator of the flying pickup head in the presence of air bearing effect and runout disturbance. The immune algorithm includes antigens reorganization, antigen integration and appearance, the stimulation and suppression chains between antibodies in the immune system, and immune response of artificial immune system. In simulation, this study treats runout disturbance as antigens in track following whereas environment disturbance as antigens in focusing. For control robustness, we define suitable antibodies to restrain antigens. In experiments, we treat disk deformation as antigens and proportional-integral-derivative (PID) gains as antibodies. Established by PID gains, the immune database helps realize the immune algorithm. In track following for a circle of 500 nm radius, the closed-loop response precision is 5 % in dual-direction control experiments.