A fine-interpolation-based parametric interpolation method with a novel real-time look-ahead algorithm

Abstract

Parametric interpolation is presently supported by majority of CNC systems because of its various advantages over traditional linear/circular interpolation. Two stages (i.e. rough interpolation and fine interpolation) involved in parametric interpolation are complementary to each other in terms of affecting machining quality significantly. So far much work has been conducted to improve the machining process with various rough interpolation adjustments, while with little research on fine interpolation. To further alleviate the feedrate jump between two adjacent rough interpolation periods, a fine interpolating strategy implemented within one rough interpolation period can be utilized to make the feedrate alteration comparatively smooth. Meanwhile, an arc is adopted to substitute the linear path to reduce the chord errors caused by rough interpolation. Besides, as one of the major difficulties of parametric interpolation is the feedrate determination concerning a wide variety of technical parameters, a real-time look-ahead feedrate generation method which can determine the decelerating position rapidly and accurately is proposed in this paper. The look-ahead approach can generate the feedrate profile to satisfy the geometrical constraints and kinematical characteristics determined by machine tools. Finally, the proposed parametric interpolation method is performed in an open architecture CNC platform to machine parametric curves. The results are satisfactory and are able to verify the robustness and effectiveness of the proposed algorithm.