Smooth non-uniform rational B-spline (NURBS) machining with kinematic limit for short linear segments

Abstract

Set of methods based on non-uniform rational B-spline (NURBS) are proposed in this article, which are adopted to improve the smoothness during short linear numerical control (NC) codes machining. The smoothness refers to two aspects: the contour fairness of CL trajectory and the machining stability of the machine tool. To obtain contour fairness, the optimised knots combination strategy (OKCS) is proposed in least square NURBS fitting from short linear segments, which generates NURBS curve for the next interpolating process. Sequentially, an axis-based look-ahead NURBS interpolator (ALANI) is designed for NURBS interpolation in order to improve the machining stability according to the kinematic limit. Both OKCS and ALANI are simulated and compared with congener algorithms, respectively. Furthermore, algorithms are implemented on digital signal processor (DSP) platform, and actual machining examples are presented at last.

Keywords:

• NURBS interpolation
• NURBS fitting
• short linear segments
• knots combination
• kinematic limit
• DSP

Acknowledgements

This project is supported by the Science and Technology Project of Zhejiang Province (no. 2009R50008).