关键词: 数控系统, 非均匀有理B样条, 曲线拟合, 刀具路径, 最小二乘法

Abstract: In high speed, high accuracy machining process of complicate surface, micro-line chains were utilized as tool path to generate free-form splines and surfaces, the discontinuities between line segments destroyed part surface smoothness and caused feed rate and acceleration fluctuation. To deal with this problem, a tool path optimization method based on Non-Uniform Rational B-Spline（NURBS） curve fitting was proposed. A segmentation algorithm based on tool path geometric characteristics analysis was used to distinguish the Micro-line Chains. Least square NURBS curve fitting algorithm combined with boundary continuity conditions was implemented to resume tool path smoothness. A feature point searching method was proposed to set the original curve parameters and error-bounded node vector as well as control point adjusting were used to guarantee the fitting precision. Experiment results showed that optimized tool path based on the proposed NURBS curve fitting algorithm obtained good smoothness to fulfill the high performance requirements in free-form surface machining.

Key words: numberical control system, non-uniform rational B-spline, curve fitting, tool path, least square method