数控系统连续微段重构与插补算法

Continuous Micro Line Blocks Reconstruction & Interpolation Algorithm of CNC System

针对目前微段加工所采用的非重构微段加工方法中存在的因加工轨迹与设计曲线轮廓误差较大而产生的轮廓加工精度较低的问题,及因微段节点处速度方向不连续而导致的加工表面质量不高、加工过程机床振动较大的问题,在计算机数控(computerized numerical control,CNC)中采用实时曲线重构与插补算法进行连续微段加工以实现对复杂曲面的高速高精度加工.微段插补技术包括样条曲线的实时重构及递推插补算法,及建立满足插补过程中加减速要求的且可以直接递推的插补样条曲线的重构条件.应用微段曲线重构技术进行的样件数控加工实验中,在保证曲线轮廓加工精度达到微米级精度的同时,加工速度提高了2～2.4倍.实验结果表明,实时曲线重构微段加工不仅可以实现在重构曲线的范围内只进行一次整体加减速的速度规划,提高加工效率,而且加工轨迹的进给速率的衔接平滑、轨迹光滑、表面质量好,并且利用重构的可以直接递推插补的样条曲线,有效解决了复杂算法加工过程中精度与运算速度的矛盾,提高了加工精度.

Aiming at the low accuracy of profile caused by large deviation between machined trajectory and designed profile,and the low surface quality and the vibration in machining process induced by discontinuity of velocity direction on the knot of micro-line blocks when using the algorithm of micro-line machining without curve reconstruction of micro line blocks,a continuous micro line blocks real time curve reconstruction and interpolation algorithm is presented for micro-line machining to realize high speed and high accuracy complex surface machining in computerized numerical control（CNC）. The algorithm includes micro-line blocks real time spline reconstruction recursive interpolation algorithm,and establishes conditions of reconstructed spline curve which can be directly interpolated recursively under condition of acc/dec（acceleration and deceleration） in interpolation process.As the experiment shows,in which a sample is manufactured,the new algorithm can ensure that contour accuracy of curve machining reaches micrometer level,meanwhile,the machining speed is 2～2.4 times the speed of the origin algorithm.The result indicates that by using real time curve reconstruction micro-line machining algorithm,not only the machining efficiency can be improved,because speed planning with acc/dec can be made only once in entire reconstructed curve range,but also trajectory feedrate can be joined smoothly,so trajectory is fair and surface quality is fine.Plus,by making use of reconstructed spline curve suitable for recursive interpolation,the conflict between accuracy and computing speed of machining process using complicate algorithm is balanced,therefore machining accuracy can be promoted.