The Research On Approximation Algorithm For NURBS Curves With Line And Circular Arc In NC

To meet the requirements of modeling and NC machining of complex-contour curve, at first, the thesis discusses how to acquire the control vertex from data points. It bases on the reverse-calculation of NURBS, then two approaching algorithms with lines and circular arcs are presented, the former is based on dichotomy and its principle is so simple that can be programmed easily, the latter uses least square circular arc to fit the curve and its approaching precision is high though the number of circular arcs is smaller. Another approaching algorithm with line or curve is proposed on the basis of the former methods. The curve's curvature decides which approaching method to choose. The algorithm reduces the information transferred from the CAD system to the CNC system and improves the efficiency and quality of machining.