- 學位論文
高精度低成本的精密定位平台之雙迴路控制器設計
Development of a Precise and Low-Cost Positioning Stage Using a Two-Loop Robust Controller
摘要
以商業化量產的讀取頭模組作為一小型定位平台，利用讀寫頭的兩大伺服系統之ㄧ的聚焦伺服系統，作為此精密定位平台的之動作。位置的資訊取得不需要另外的感測器，而是直接採用讀取頭模組的光感測器來實現，即著名的S-曲線。為了降低成本需求而且能達到高精度的精密定位精度，本研究採用Matlab Simulink的xPC架構，運用Sensoray 626A/D D/A擷取卡，以雙迴路控制器，即由H-infinity控制器、前饋控制器和干擾觀測器(disturbance observer)所構成的雙迴路，來實現此平台之定位精度。由實驗結果顯示此精密定位平台的中、短行程(1 、200 )都有很好的定位精度呈現出來，並有改善抵抗干擾能力的不足。選擇H∞和干擾觀測器控制器是因為舊有PD控制器在音圈馬達低速時雖能有很好的追蹤效能，但在高速時卻會變的不穩定，頻寬也會受限制；然而，H∞控制器除了在低速能有極佳的穩定性能，在高速也依然穩定強健，這乃是因為H∞控制器具有頻率整形能獲得充分的穩定邊限可在高頻寬適應DOB。既然此低成本取向之定位平台能有高精度的結果，未來能應用在生醫精密定位上。
並列摘要
In this research, we implemented a low-cost precision positioning stage which using a commercial available OPU (optical pickup-head unit) by a two-loop controller. A two-loop controller described in this research is proposed by adopting a disturbance observer (DOB) as the internal-loop compensator to cancel out the model error and a H-infinity as external-loop compensator to provide sufficient stability robustness for the entire system. The feedback position signal of the platform was measured through the reflected signals on photodiodes from a compact disc. Experimental results showed that the positioning stage was able to follow different ranges of step commands, such as 1 and 200 step commands. H-infinity controller has superior features for frequency shaping to obtain a sufficient stability margin to adapt an internal-loop DOB with higher bandwidth. This explains why the H-infinity control with DOB can achieve better performance.