Abstract:

A Non-uniform rational B-spline (NURBS) interpolation algorithm was proposed herein, which was based on the feedrate sensitive point identification. It was crucial for an advanced CNC system compatible with NURBS. The contour errors during rough interpolating calculation were related to the federate at the current point, so it was possible to indentify the feedrate sensitive points according to the chord error during interpolation approximation. The feedrate profile between any two sensitive points should be designed adaptively according to the distance between them, and the security buffer was used. The whole feedrate profile can be generated by feedrate segments combination. A cubic NURBS curve was used to evaluate the interpolation algorithm, and it was simulated under 3 different feedrate commands. Simulation results show that the algorithm is available and can be implemented flexibly according to the different situations of sensitive points. It is also shown that the proposed algorithm guarantees both the contour precision and feedrate smoothness.

Key words: NURBS, sensitive point, chord error, security buffer

摘要：

提出了一种基于进给速度敏感点识别的NURBS曲线插补算法,该方法对于兼容NURBS形式的高档数控系统至关重要。粗插补计算造成的轮廓误差与插补经过该点时的进给速度大小有关,敏感点则可根据插补微段逼近时的弓高误差来界定。进而,根据相邻敏感点之间的距离,通过增设安全缓冲区等方法,进行速度曲线自适应规划。整体进给速度曲线可以由各部分进给速度曲线连接而成。为评价算法的有效性,采用3次NURBS曲线在三种不同进给速度指令下进行仿真计算。仿真结果证明,该算法很好地将轮廓精度和进给速度的平滑性进行了系统考虑,能在相邻危险点复杂分布的情况下执行柔性的插补控制。

关键词: NURBS, 敏感点, 弓高误差, 安全缓冲区