兩段式光學讀頭聚焦伺服設計

Abstract

在這篇論文中，我們對光學讀頭聚焦伺服機構採取了兩段式的設計，根據聚焦裝置在物理上的限制設計整個控 制系統迴路，並對非線性系統提出線性化的方法及條件假設後，藉由系統穩定性及其穩態誤差與頻率響應規格的 分析來進行控制器的設計，然後將所設計的控制器用於控制系統來做步階響應及一用高低頻混合訊號來表示碟片 的翹曲及軸向晃動的模擬測試。模擬測試的結果中，步階響應的上升時間和最大超越量分別可以達到0.00005秒和 1.17%。混合訊號測試上，雖然coarse stage和fine stage可以分別將低頻和高頻的訊號處理的不錯，但由於小車(fine stage)在行程先天上的限制，必須重新設計補償器來增加coarse stage的頻寬，最後的模擬顯示，聚焦誤差可以控制 在 0.23 以內。另外，利用伺服晶片MT1105F裡的控制方塊，經由韌體來改變參數，而達到實現控制器的目的。

In this thesis, we design a two-stage focus servo system for the optical pick-up head. According to the native restriction of the focus mechanism, there is a nonlinear effect in the system. We first analyze the system with linear assumption first. Based on the stability criterion, we have specifications for steady state error, and focusing requirements designed the compensators. Taking the simulation tests for a step response and a signal of mixed frequency using the compensator we have examined. The step response is sound, both rising time and overshoot is improved to 0.00005 sec and 1.17%. Although both coarse stage and fine stage yield good response in low and high frequency signals. But the fine stage has difficulty for completing the movement due to the limitation of stroke for the mixed frequency signals expressing the effect of disk warp and axial runout. After a redesign step the compensator that increases the bandwidth of coarse stage yields a better result. The simulation resultant shows the error reduce under 0.23 . In addition, we use MT1105F servo chip to offer a method to implement the controller due to the firmware.