光碟機聚焦伺服之PID 控制器自動調整

Abstract

本文研究光碟機聚焦伺服之 PID 控制器增益之自動調整機制，並且利用 數位訊號處理器（DSP）與可程式閘陣列（FPGA）實現於光碟機系統。於 聚焦伺服控制器增益自動調整，採用頻率響應之觀念，有系統地設計聚焦伺 服控制器增益線上自動調整機制，使聚焦伺服控制器能針對光碟機因製造組 裝上的差異、元件老化、環境溫度改變、碟片反射光量變化等不確定因素對 伺服性能造成的影響進行自動補償，進而讓系統對於參數不確定性具有強健 性，確保系統達到目標性能。 本文以市售之12 倍速DVD-ROM 光碟機進行改裝而成實驗平台，以TI TMS320C6713 DSP 與 Xilinx 可程式閘陣列（FPGA）取代光碟機上原有的 伺服控制晶片，並以C 語言與硬體描述語言（VHDL）做為發展工具，進行 PID 控制器設計且實現於此光碟機。 經由實驗結果證實，透過本文提出之聚焦伺服PID 控制器自動調整機 制，無論系統原有之控制器增益值過高或是過低、碟片轉速快或慢，均能自 動將聚焦伺服系統調校至符合DVD 規格書規範之伺服性能要求，即便使用 超過規格書容許偏擺量之測試碟片進行實驗，本自動調整機制仍能有效運 作，自動調整聚焦控制器增益，使聚焦伺服性能達到要求目標。

This thesis presents an automatic gain-tuning mechanism which is based on the frequency-response approach and applied to focus servo of optical disk drives with on-line and self-tuning features. This method can attenuate servo-gain error due to mass production, temperature variation, or different light reflections, and fulfill specifications of focus servo. The experimental system consists of a commercially available 12Xs DVD-ROM drive and a DSP/FPGA system that is the control kernel. We use the C language and hardware description language (VHDL) as tools for developing servo controllers to replace the servo chip on the original drive by the DSP/FPGA. The proposed method has been implemented in the experimental system under various operating conditions, such as different initial controllers, disk with significant wobble, and various spindle speeds. According to the experimental results, the method presented in this thesis can automatically and robustly adjust controller gains to fulfill frequency-domain specifications.