OMNI Interpolator for High-performance Motion Control System Part I: Algorithm of Interpolator

This paper presents the OMNI-Interpolator design based on the NURBS interpolation algorithm. The five main issues regarding CNC interpolator have been discussed. First, a unified NURBS interpolator is proposed to simplify the CNC interpolator design thoroughly. Then, the geometry chord error that usually occurs during interpolation calculation is well controlled to obtain high accuracy. Third, variable feedrate is introduced to adjust the speed profile to adapt with the cutting trajectory geometry, especially around sharp corners. Fourth, limitation settings for the limitations on servo motor power and overcut/undercut are discussed. Finally, the machine tool dynamics are considered and integrated in the interpolation stage by filtering out natural frequency components contained in the compositional feedrate profile of the interpolated motion command. A simulation has been conducted using a X-Y table to evaluate the feasibility and effectiveness of the proposed interpolation scheme.