本論文應用並實現適應性聚焦控制器於車用光碟機系統。此研究分為兩部份，首先設計架設於激振器上之光碟機振動平台，用以模擬行車振動；進而應用適應性聚焦伺服控制（AFSC）於光碟機上做前饋控制，以改善聚焦效能。LMS架構之適應性控制器已被廣泛採用，但此演算法收斂速度與穩定性較不適用於條件急速變化之環境，如光碟機使用於行車振動之情況等。本研究採用MVSS-FXLMS架構用以改善，此架構由濾波型最小均方（FXLMS）為基礎，並搭配可變收斂因子（MVSS）演算法，依據控制狀態增加FXLMS之收斂速度及穩定性。由此法產生之前饋控制訊號，能有效控制讀取頭跟隨外界振動進而達到消除擾動之效果；實驗結果顯示， AFSC能有效的消除車用光碟機上經由垂直振動產生之聚焦誤差。 The thesis presents the implementation and application of an adaptive focusing controller for DVD drives in recreation vehicle. This study includes two parts. The first part is to design and construct an optical disk drive platform mounted on a vibrating shaker which is to simulate a vehicle system with variant environment. The second is to apply and implement adaptive focusing servo control (AFSC) techniques in the employed optical disk drive platform. The applied AFSC is realized to improve focusing performance and based upon the adaptive control algorithm associated with optical disk drives. To adaptively suppress vibration influence on DVD drives, most of the conventional methods for AFSC are to extensively apply adaptive filtering with the least-mean-square (LMS) error algorithm. Unfortunately, convergence speed is often limited and unsatisfied with vibration environment of disk and/or varying filtering plant. It is noted that the learning process of the adaptive algorithm fails to quickly respond to the changing operational conditions. In the study, a modified variable step-size filtered-x-least-mean-square algorithm (MVSS-FXLMS) is implemented. The applied MVSS-FXLMS filtering algorithm is a combination of the MVSS convergence and FXLMS algorithms. The feedforward signal generated by the adaptive controller as an antivibration input can effectively suppress the primary source arising from the vibration disturbance. Experimentation indicates promising results that the AFSC can successfully eliminate the focusing error due to the vibration of DVD drives in vehicle systems.
