開發一具有即時預視功能之混合型NC碼插補器

Development of a real-time look-ahead interpolator with Hybird NC codes

王冠中(Guan-Jhong Wang)

指導教授 ： 林明宗

國立虎尾科技大學/工程學院/機械與機電工程研究所/碩士(2010年)

https://doi.org/10.6827/NFU.2010.00073

摘要

由於傳統的CNC 工具機只提供直線以及圓弧插補器，CAM 系統必須產生許多微小的直線及圓弧線段來逼近工件幾何外型，這種近似方法將會產生進給率變動太大、加速度不連續以及加工程式傳輸量太大等問題，在高速加工情況下，這些問題將會大幅降低工件的加工精度。
為了達到高速加工的需求，因此，本論文的目的是在PC-Based 開放式架構下，搭配即時多工作業系統(RTX)的各項功能及插補技術為核心，針對傳統的混合型G 碼(包含G00、G01、G02/G03、G06.2)開發一具有即時預視功能之混合型NC 碼插補器之功能。
首先，此混合型NC 碼插補演算法可事先預視200 個G01 短線段及G02/G03 圓弧線段，一方面可以由G01 連續短線段擬合成NURBS 曲線，另一方面可以將G01 和G02/03 線段混合使用。接著將預讀的線段產生出一平滑且具有加減速連續的速度命令及位置命令；該演算法同時可以偵測到NURBS 曲線和混合線段中的尖銳轉角，並藉由降低尖銳轉角處的加工速度來提升加工精度。
最後，將本論文所提出的方法以MATLAB 模擬其結果，並利用自行研發之PC-Based 控制器在三軸雕刻機進行實驗以驗證其演算法之可行性。

關鍵字

NURBS ； 即時預視 ； 直線/圓弧插補

並列摘要

Since traditional CNC (Computer Numerical Control) machines only provide linear and circular interpolations, CAM(Computer Aided Manufacturing)systems have to generate many small linear and circular NC blocks for the parts.
This approach suffers from the problems such as f eedrate fluctuation, acceleration/deceleration (ACC/DEC) discontinuity, and a large volume of data transmission. The problems could significantly reduce machining accuracy
under high-speed machining.
For achieving high-speed and high-accuracy machining, a real-time look-ahead interpolator with hybird NC codes which includes G01, G02/G03, G06.2 etc. is proposed in this thesis. We develop the kernel techniques of
interpolator and its look-ahead function based on PC-Based open architecture. For evaluating real-time performance of the proposed algorithm, the PC -based motion controller with real-time extension (RTX) embedded in Windows
operation is applied to realize real -time computing and multi-tasking.
The proposed algorithm can preview 200 blocks of NC codes such as G01,G02/G03 and G06.2 using the look -ahead function. G01 continuous short segments which satisfied chord tolerance are fitting to be a NURBS curve.
Furthermore, the look-ahead algorithm detects sharp corners of NURBS curves and corners among hybird NC blocks, and adjusts feedrates at the sharp corners
for improving machining accuracy. Finally, the interpolator generates a smooth and continuous acceleration/deceleration feedrate profile for each NC blocks.
Simulations are performed to verify the proposed method using MATLAB.Experiments using a PC-Based controller are conducted to demonstrate that the feasibility and efficiency of the proposed algorithm on a three-axis engraving machine.

並列關鍵字

NURBS ； Real-time Look-ahead ； Linear/Circular interpolator.

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