LOOK-AHEAD NURBS-PH INTERPOLATION FOR HIGH SPEED CNC MACHINING

Abstract

Various methods for parametric interpolation of NURBS<br><br>curves have been proposed in the past. However, the errors<br><br>caused by the approximate nature of the NURBS interpolator<br><br>were rarely taken into account. This paper proposes an<br><br>integrated look-ahead algorithm for parametric interpolation<br><br>along NURBS curves. The algorithm interpolates the sharp<br><br>corners on the curve with the Pythagorean-hodograph (PH)<br><br>interpolation. This will minimize the geometric and interpolator<br><br>approximation errors simultaneously. The algorithm consists of<br><br>four different modules: a sharp corner detection module, a PH<br><br>construction module, a jerk-limited module, and a dynamics<br><br>module. Simulations are performed to show correctness of the<br><br>proposed algorithm. Experiments on an X-Y table confirm that<br><br>the developed method improves tracking and contour<br><br>accuracies significantly when compared to previously proposed<br><br>adaptive-feedrate and curvature-feedrate algorithms.