整合精密運動控制器與NURBS插值器之CNC設計

Abstract

運動控制器要提高精密度，主要是要降低加工中產生之輪廓誤差（contouring error），及路徑命令之誤差。整合式運動控制系統（integrated motion control system）將零相位誤差追跡控制器（ZPETC）及交叉耦合控制器（CCC）整合起來，分別改善追跡誤差（tracking error）及輪廓誤差，得到良好的運動精度。命令軌跡座標架構（task coordinate frame approach）的方法，將追跡誤差轉換為命令軌跡之切線方向誤差及法線方向誤差，成為誤差調整的問題。降低切線方向誤差將改善追跡誤差﹔降低法線方向誤差將改善追跡誤差及輪廓誤差。整合式運動控制以SISO的手法得到穩健的輪廓控制精度。軌跡座標方法以MIMO的設計同時達成降低軌跡及輪廓誤差。本文深入研究兩種控制方式之控制器設計並比較兩者對於運動精度之影響。並實現於實際的加工機上，改良其加工精度。 另一方面，本文實現NURBS插值器於運動控制系統之中。實驗結果指出，定速度參數迭代之NURBS插值器達成精密之位置命令精度及速度命令精度，配合上精密之運動控制系統，可達成精密之軌跡精度。

To improve the motion accuracy, efforts were put mainly on reduction of contouring error and inaccuracy of the path command. In the past the integrated motion control system combines the zero phase error tracking controller (ZPETC) and the cross couple controller (CCC), to simultaneously reduce the tracking error and contouring error, to achieve high motion accuracy. On the other hand, the task coordinate frame (TCF) approach transfers the tracking error into the normal error and tangential error in a moving task coordinate frame. Then the contouring motion can be viewed as a regulation problem on the coordinate. The normal error is approximated to the contouring error to be reduced. Moreover, to reduce the tangential error will improve tracking performance. In this paper, performance of the two different precise motion control laws is compared on the DYNA 1007 machining center. Furthermore, the non-uniform rational B-spline (NURBS) interpolator in the motion control system is included. Results indicate that, the constant-speed NURBS combined with precise motion controller will achieve the highest tracking and contouring accuracy, and the least velocity variation.