最小變異控制應用於光學循軌伺服系統之研究

Abstract

本論文之重點在於研究光碟機的循軌伺服系統，我們採用市面上實際的光碟機為平台，期望在變動原系統最小的原則下，另外加入控制器以改善循軌輸出誤差。首先針對循軌伺服系統的原理進行分析，推導出系統數學模型，接著利用虛擬二元隨機訊號(PRBS)為輸入來進行量測，以此實驗架構取得實際系統輸入與輸出之資料，配合前述所推導的數學模型，進行系統判別。在取得循軌系統的ARMAX模型後，開始設計輔助的循軌控制器，將最小變異控制的理論應用在循軌致動器上，以控制其輸出的變異量最小化。由實驗的結果發現我們所設計的最小變異控制器可以有效的降低循軌輸出誤差的變異量，以提高光碟機系統本身循軌的精確度，而適用在未來更高密度的光儲存系統。

The thesis described the study of tracking servo in optical system .The proposed control scheme uses the concept of “add-on” to combing the proposed control input with the control signal coming from DVD chip. An add-on controller imposes a light computational burden, and does not need any extra sensor. The present study is organized as follows: Firstly, studied and analyzed the tracking servo system to get the system model. A sequence of pseudo random binary signal (PRBS) is fed into the measured circuit of servo control system. We obtain the experimental I/O data so that the tracking model can be identified. Secondly, we use the identified model (ARMAX) to design the proposed tracking controller. This add-on controller reinforces the system performance having the minimum variance of the tracking error. Simulations and experiments indicated that the proposed tracking controller makes the tracking error smaller than conventional servo system. Therefore, the proposed controller can be applied to next-generation optical storage systems.