Abstract. The paper based on OpenCASCADE algorithms to approximate the NURBS curve to arc spline. The method is most useful in numerical control to drive the cutter along straight line or circular paths. Or in the shipbuilding industry to manufacture section bar for cold frame bender.
Key Words. NURBS, Biarc approximation, arc spline,
1.Introduction
在數(shù)控加工CNC領(lǐng)域，通常需要用盡量少段數(shù)的圓弧和直線段來對曲線進行擬合。有的數(shù)控繪圖機也只有直線和圓弧插補器，即只能繪制直線和圓弧，所以也需要將自由曲線轉(zhuǎn)換成直線和圓弧來進行繪制。在船舶制造方面，如肋骨冷彎機只有兩種狀態(tài)：彎和不彎，也只能加工出直線和圓弧，所以也需要將曲面型材的彎曲信息轉(zhuǎn)換成肋骨冷彎機能加工的數(shù)據(jù)。如下圖所示為型材模型及其基線：
Figure 1. 型材模型及基線