在一般情況下，光碟機本身的伺服控制器可以減少些許聚焦及尋軌誤差，然而車用或可攜式光碟機，常受到外在環境的衝擊或振動等干擾，使得光碟機本身的伺服控制器無法抑制外在干擾所造成之聚焦及尋軌誤差。有鑑於此，本論文應用適應性複合伺服控制器(AHSC)於車用光碟機之伺服系統，期能消除因外在環境所產生之低頻干擾，進而改善聚焦及尋軌性能。適應性複合控制器包含前饋及回饋主動式干擾消除，並採用RVSS-FXLMS架構，此架構由濾波型最小均方（FXLMS）為基礎，搭配可變收斂因子（RVSS）演算法，依據控制狀態增加FXLMS之收斂速度及穩定性。由此法產生之控制訊號，能有效控制讀取頭跟隨外界振動進而達到擾動消除之效果；實驗結果顯示，AHSC能有效的消除車用光碟機上經由振動干擾產生之聚焦及尋軌誤差。 In general, the servo controller of a DVD drive system can reduce some extent of errors present. However, in vehicle or portable systems, disturbances from external environment such as shocks and vibrations can further raise the level of errors. The focusing and tracking errors of DVD drives can not be effectively suppressed by the servo controller as the feeding deck is severely disturbed by environment. The thesis employs the adaptive hybrid servo control (AHSC) for the servo system of DVD drives in recreation vehicle, in order to suppress disturbance with frequencies under 100Hz cased by external disturbance and to improve the performance of focusing and tracking servo systems. The AHSC technique consists of both the active feedforward and feedback disturbance cancellation. In the study, the controller is designed based on an adaptive digital filter with the robust variable step-size filtered-x-least-mean-square (RVSS-FXLMS) algorithm. The applied RVSS-FXLMS filtering algorithm is a combination of the RVSS convergence and FXLMS algorithms. The control signal generated by the AHSC as an anti-error input can effectively suppress the tracking/focusing errors arising from the vibration disturbance. The experimental results demonstrate that the AHSC can successfully suppress external vibration disturbances and improve the focusing and tracking performance upon an existing architecture of the DVD drives in a vehicle system.
