五轴NURBS插补中的速度前瞻控制方法

为提高五轴非均匀有理B样条的插补精度,减轻段间转接时对机床的机械冲击,提出了一种速度前瞻控制处理方法.采用曲率圆逼近的方法建立了插补误差计算模型,并推导出满足插补误差要求的最小曲率半径与进给速度间的关系.采用数值分析方法预先计算出减速点的参数值,对样条插补进行了加减速前瞻规划处理.实时插补时对样条曲线上曲率半径较小的地方进行减速处理,以提高插补曲线的逼近精度.实例证明,该方法能有效降低插补误差和段间转接时的加速度,具有良好的实时性,可以应用到实际的数控系统中.

Look-ahead controlling method of feedrate in 5-axis NURBS interpolation

To improve accuracy of S-axis Non-Uniform Rational B Spline(NURBS)interpolation and to cut down mechanical impact on machines during transition, a look-ahead feedrate control method was presented. The computa-tion model of interpolation errors was established by using an approximation method with curvature circle and the relationship between minimum curvature radius and federate, which could meet the requirements of interpolation errors, was also deduced. With the numerical analysis method, parametric value of deceleration point was calculated and then acceleration/deceleration predictive planning was executed on spline interpolation. To the points on the spline curve with smaller curvature radius, feedrate was slowed down to enhance the approximate precision of the interpolated curve in real-time interpolation. The example validated that the proposed method could effectively reduce the interpolation errors and the accelerations in transition. At the same time, the presented method had excellent real-time performance and it could be applied to practical numerical control system.