零振幅誤差追跡運動控制器設計

Abstract

面對當前被廣泛使用的前置控制器--零相位誤差追跡控制器（ZPETC），本文提出新的前置控制器，零振幅誤差追跡控制器（Zero Magnitude Error Tracking Controller, ZMETC），並以雙維自由度（2DOF）的伺服控制架構為基礎，結合數位式擾動觀測器（DDOB），以達到高精密度、高穩健性的目的，且在高速時有優異的表現。 為達成精密運動控制的要求，控制系統需要具備良好的追跡能力、輪廓精度以及抗擾動能力。高精密度意味著降低追跡誤差與輪廓誤差，而前置控制器能藉著適當的極零點配置（pole-zero placement）與極零點對消（pole-zero cancellation）改善控制系統的追跡性能，提高運動精密度。但由於控制系統無可避免地會受到外界擾動（external disturbance），如摩擦力、負載變化，以及控制系統本身參數變化（parameter variance）的影響，使得控制器無法針對精準的受控模型（model）進行控制，因而降低了系統效能。於是，如何既降低追跡誤差與輪廓誤差，又能避免控制系統受到擾動的影響，就成為一項重要的課題。 ZMETC的追跡能力十分優越，而且具有高頻寬的特性，非常適合高速應用。配合 DDOB 之後，能提高運動控制系統的穩健性，降低擾動對控制系統的影響，並且消除極零點對消不完全所造成的不良效應，更進一步地提升 ZMETC 的效能。 本文探討的控制架構都實現在 DYNA 1007 型工具機上，實驗結果顯示，無論命令速度提高或負載增加，ZMETC 的效能都超越 ZPETC，尤其在高速應用時，ZMETC 追跡能力的領先幅度更大。然而，若兩者都搭配 DDOB，ZPETC+DDOB 的控制架構會有較佳的表現。

In resent years, zero phase error tracking controller (ZPETC) has been succeed in improving tracking accuracy. This thesis proposed a new feedforward controller, the zero magnitude error tracking controller (ZMETC) to achieve better performance with high-speed operations. By applying the two degree-of-freedom (2DOF) servo control structure, ZMETC and digital disturbance observer (DDOB) are combined to achieve high-speed-high-precision (HSHP) tracking performance and robustness for motion systems. To achieve precise motion control, the control system requires all good tracking ability, contouring accuracy and robustness. By applying the pole-zero placement and pole-zero cancellation, the feedforward controller improves the tracking performance of motion system. However, the control system is certainly effected by external disturbance which causes modeling error and degrades tracking accuracy of systems. ZMETC has superior tracking performance and high bandwidth which makes it suitable for high-speed applications. By combining ZMETC and DDOB, the influence of disturbance is degraded and both the tracking error and contouring error are thus reduced. Experimental results show that ZMETC has better tracking accuracy than ZPETC, as the command speed increases and the loading is added. Moreover, as the DDOB is included, the control structure of ZPETC+DDOB presents better performance for HSHP systems.