小线段高速加工的速度模型研究和实现

Research on Feedrate Model of Look-ahead and Solution Algorithm for High-speed Machining of Small Line Segments

针对数控插补中离散化进给速度控制的特点,导出了在直线加减速情况下的小线段长度和轨迹形状误差对进给速度的约束条件;完善了小线段高速加工速度衔接数学模型,形成了能实际应用的工程化方法,该方法以给定的最大预处理段数为条件,根据小线段路径的具体形状和长短、速度变化的平滑性和位置误差精度的要求,求解出离散化的进给速度值。同时提出了在指令进给速度实时变化的情况下进给速度的求解方法。仿真结果表明,此数学模型及离散速度的求解方法能实现进给速度的高速衔接,从而大大提高加工效率。

In actual control of CNC interpolation with look-ahead, the feedrate is discrete, so some new constrains on feedrate caused by the length of small line blocks and the accuracy of workpiece contours are presented. And a novel algorithm that can apply the model of high-speed machine of small line blocks is also proposed after improving the model. Given the maximum number of look-ahead blocks, this engineering-oriented algorithm can calculate the discrete feedrate by taking account of the shape and the length of small line blocks, and also satisfy the requirements of the smoothly changing of feedrate and the accuracy of parts. At the same time the solution of achieving look-ahead when CNC is faced with real-time adjusting of the programmed feed rate override is built. Simulation result of a practical example demonstrates the machine applying the improved model and the algorithm can achieve high speed machine and improve the productivity dramatically.