Research on consecutive micro-line interpolation algorithm with local cubic B-spline fitting for high speed machining

Abstract

To achieve high-speed and high-accuracy machining, look-ahead scheme and parametric interpolator have shown significant effect on interpolating micro-line blocks. On the one hand, look-ahead schemes have been integrated in many computer numerical control (CNC) systems to alleviate the frequent start/stop motion and achieve a higher feedrate. However, the unsmooth speed at the segment junctions cannot be avoided entirely due to the discontinuous nature of the linearized-segmented contour. On the other hand, parametric interpolator has been proposed to overcome the shortcomings of the linear/circular interpolator. But, it is difficult to fit the blocks into parametric curves on-line. In this paper, a local cubic B-spline fitting algorithm with real-time look-ahead scheme is proposed for consecutive micro-line blocks interpolation. First, the consecutive micro-line blocks, which satisfy the bi-chord error constraint, are fitted into a C1 continuous cubic B-spline curve. Second, machining dynamics and tool path contour constrains are taken into consideration. Third, an optimal look-ahead scheme is proposed to generate the optimal feedrate profile. Simulation and experiment are performed in real-time environment to verify the effectiveness of the proposed method. Compared with the conventional interpolation algorithm, the proposed algorithm reduces the machining time by 70%.