伺服馬達之QFT穩健控制器設計與CNC精密運動之監控系統實現

Abstract

本論文首先提出了速度迴路頻寬提升的控制架構，利用尼可士圖分析系統的 頻寬及共振峰值，並設計QFT 控制器抑制共振峰值，使系統運作在較高的增益 下提升系統的頻寬，即可將系統的頻寬提升且共振峰值抑制在2dB 以下，隨後 將此方法實現在士林公司的伺服馬達上，使用QFT 控制器並搭配ZMETC 成功 將原先頻寬上限613Hz 提升至806Hz。對於大幅變動負載與增益的系統重新設計 QFT 控制器，使3.9J 負載的系統頻寬從93Hz 提升至206Hz，並且實際應用於 CNC 平台進行位置控制，使用QFT 控制器的CNC 平台不管命令的快慢都有較 好的精密度，隨後藉由追跡誤差與DDOB 輸出量兩項指標進行監控，將外部擾 動與命令變化等影響系統指標的因素，透過數位式擾動觀測器與位置迴路P 控制 器進行補償，使系統回復至原有的性能。

The robust QFT (Quantitative feedback theory) control structure for improving bandwidth of the velocity loop for the AC servo motor has been studied in this Thesis. By using Nichols Chart of the motor system, the QFT controller can be obtained to effectively suppress the resonance peak. Experimental results indicate that the velocity bandwidth of the Shih-Lin AC servo motor can be thus enhanced from 613 Hz to 806 Hz with a resonance peak under 2 dB. As the load or the system gain significant changes, the original nominal model for the QFT design is not suitable anymore and a redesigning process with a newly identified system model is thus required in practice. By applying the additional 3.9 J load to the servo motor, the bandwidth can be thus enhanced from 93 Hz to 206 Hz with the newly designed QFT controller. Experimental results of the servo motor implemented on the DYNA CNC 1007 machine tool indicate that regardless of CNC motion command feedrate, the motion accuracy can be well maintained by implementing the QFT controller. Results also indicate that to eliminate the effect of external disturbances and command changes, the system compensated with both the DDOB and tuned position loop P controller will maintain the motion accuracy well.