CNC運動控制器之最佳化NURBS曲線規劃與插值器設計

Design of Optimum Feedrate Planning and Interploator of NURBS Curve for CNC Motion Controller

蔡政穎(Cheng-Yin Tsai)

指導教授 ： 陳金聖

國立臺北科技大學/機電學院/自動化科技研究所/碩士(2011年)

摘要

本論文主旨在提出一套有效且能實際應用在CNC工具機台上的NURBS曲線規劃與插值器設計的方法。此方法包括：NURBS曲線前處理、NURBS曲線規劃以及NURBS曲線插值器三部份。在CAM透過演算法產生近似原工件輪廓的加工資訊時，即在產生的過程中造成了誤差，使得工件在加工的過程中會產生刀痕。曲線前處理透過直線前處理和曲線前處理。前者過濾原本應該是直線的加工線段，避免經過曲線擬合成曲線；後者是降低CAM產生加工資訊的誤差，所以曲線前處理即是在減少加工資訊的誤差產生更接近原工件，且利用曲線擬合的方式產生NURBS曲線資訊來作為規劃使用。曲線規劃這部分是藉由擬合產生的NURBS曲線資訊透過適應性進給率的演算法來設計曲線產生的精度以及估測進給率，並且找到區域曲率最大之位置當作分段點，用這些分段點將NURBS曲線分成幾個區段規劃進給率。利用最低速優先規劃法規劃進給率，以降低因為區段內路徑長度不足以加減速而需重新規劃的次數。在規劃進給率時，使用考慮運動性能的S-Curve與S-L-Curve作為加減速的規劃，以降低機台的震動，增加機台工作壽命。最後透過補償式插值器的演算法計算出準確的控制命令。本論文之方法透過CNC機台實際加工一個工件驗證其可行性。

關鍵字

NURBS ； 刀具路徑 ； 速度規劃 ； 最低速優先規劃法

並列摘要

This paper proposes a method application for the CNC system's NURBS curve planning and interpolator. The method is include 3 parts that are the NURBS curve pre-process, NURBS curve planning and NURBS curve interpolator. The information has the error with the original workpiece, this was generating by the CAM algorithm like the original workpiece's contour. First, the NURBS curve pre-process has two parts that are the line filter and curve filter. Former filters the line to avoid into curve fitting. And the latter reduces the error of the processing information. In the other hand, the NURBS curve pre-process is reducing the processing information's error and fitting the curve into NURBS data. Second, the NURBS curve planning uses the NURBS data to plane. Then, the adaptive feedrate algorithm designs the accuracy and estimated feedrates of NURBS curve. Finding the local maximum curvature position as the break points, these break points separate the NURBS curve into some segments. Furthermore, planning the NURBS curve with our proposed the lowest feedrate first priority planning that can reduce the replanning times. When the planning, the algorithm applies the two kinds of S-Curve and S-L-Curve ACC/DEC profiles based on the motion dynamics. Then, the accurate command is generated by the compensated interpolator. Finally, the processing a workpiece by the CNC system to verify this paper proposed method.

並列關鍵字

NURBS ； Feedrate Planning ； Tool Path ； LFFPP

參考文獻

[26] 賴政賢，考量機械性能之NURBS曲線速度規劃運用於補償式插值器，碩士論文，國立臺北科技大學，台北，2011。

[2] 王人傑，CNC工具機加工路徑補間之研究，碩士論文，國立成功大學造船暨船舶機械工程研究所，台南，2002。

[3] C. W. Cheng, Design and Implementation of Real-time NURBS Curve and Surface Interpolators for Motion Controllers, Ph.D. Thesis, National Cheng Kung University, Tainan, Taiwan, 2003.

[4] S. S. Yeh and P. L. Hsu, "The speed-controlled interpolator for machining parametric curves," Computer Aided Design, Vol. 31, No. 5, 1999, pp. 349-357.

[6] W. T. Lei and S. B. Wang, "Robust real-time NURBS path interpolators," International Journal of Machine Tools and Manufacture, Vol. 49, 2009, pp. 625-633.