DVD光碟機之DSP主動式聚焦控制器
摘要
DVD具有儲存密度高、體積小與保存方便等優點，越來越被廣泛地應用，而由於其較高的儲存資料密度，因此雷射的讀寫控制勢必更加精密、即時與穩定，而在攜帶式的DVD光碟機產品因外在環境影響更必須特別注意其讀取與寫入的穩定性。本論文即提出一有效的控制方式以解決攜帶式光碟機受外在擾動聚焦不穩定的問題，主要是以主動式(active)前饋控制(feedforward control)的方式有效消除外來擾動對光學頭的影響，控制器使用適應性濾波器(adaptive filter)來實現，其較被動式控制與回饋控制(feedback control)更能有效消除低頻及寬頻的擾動，其即為攜帶式光碟機最須克服的難題。
而整體實驗為了提高與市面產品的相容性，也開發了一數位信號處理器(digital signal processor，DSP)嵌入式(embedded)系統以實現適應性控制的運算並可提供其他控制系統之開發核心。實驗結果顯示在窄頻(single tone)擾動可迅速的(約0.3秒內)消除了約32dB，而寬頻(broad band)方面則消除16.7dB，證明了所提出的主動式前饋控制對低頻且寬頻的擾動有效的消除，進而達到光學頭聚焦的穩定。

DVD Optical Disk Driver with a DSP-Embedded Active Focusing Controller
Abstract
DVD optical disk driver is becoming more and more popular because of the advantages of high storage density, compact volume, and easy preservation. Therefore, the controller of the driver must focus the laser spot precisely and stably. In this thesis, an active feedforward controller is set up to eliminate external disturbance with s stable focusing control. An adaptive digital filter is designed based on fixed-x least mean square (FXLMS) algorithm to implement the controller that can more efficientlysuppress the low frequency and broad band noises.
In order to match the real DVD camera recorder, we develop a 32-bit floating point DSP embedded system to implement the adaptive digital filter. Moreover, the DSP embedded system can be used as a control core in developing other system. The experimental results demonstrate that the active controller can suppress a single-tone disturbance with 32dB and a broad-band disturbance with 16.7dB. It is proven that the active feedforward controller can stably control the focusing actuator with the suppressing effect of external disturbance.

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