改善CNC工具機運動輪廓精度的控制器設計策略

Abstract

傳統工具機的運動控制方式，是使用各軸獨立控制並減少各軸所造成 的 位置誤差 ( Position Error )，但是此法卻不能有效減少因各軸 動態特性不一 致或外界負載干擾所引起的輪廓誤差 ( Contouring Error )。有鑑於此，交叉 耦合控制器 (CCC) 架構被提出，藉著補償器所產生 的補償訊號，協調各軸 而茹除兩軸以上的綜合軸廓誤差。本文則在 CCC 的架構下，提出輪廓誤差 轉移函數的穩健設計方式，以簡化補 償器的設計過程，並提供系統良好的輪 廓誤差響應。 另一方面，為使系統能有良好的追跡控制，本文藉由最佳前置控制器設 計，近似地抵銷位置回授控制系統的落後相位，同時提供系統良好的增益 響 應。此外，為降低位置回授控制系統的參數變化以及外界擾動的影 響，本文 使用適應控制方式實現前置控制器。 在本文的最後將討論含有前置控制器與交叉耦合控制器的整合型伺服 馬達位置控制系統，並且由實驗結果得知，本文所提出的控制方法在與傳 統 的位置控制結構相比較下，確實有較好的輪廓加工精度。 Traditionally, the CNC machines control the servo system of each axis independently to reduce the position error. However, they can not effectively eliminate contouring errors caused by mismatch of system model and external disturbance. To improve the contouring error, the Cross Couple Control (CCC) structure which can effectively reduce the contouring error by generating compensational signals to each axis have been proposed. Moreover, for improving tracking performance, we present a optimal method to compensate the phase lag as well as provide better gain response of the position feedback control system by a feedforward controller. To reduce the influence of external disturbance and parameter variations to the performance of position feedback control system, the feedforward controller is implemented by an adaptive algorithm. Finally, the servo motor position control system integrate both the CCC and feedforward controller in our servo motor position control system. Furthermore, theoretical results indicate that the proposed integrated controller can be designed independently. Experimental results show that both the contouring and tracking errors in motion control have been successfully suppressed by applying the integrated controller.