The Research Of Spline Curve Interpolation Algorithm For Embedded Cnc System

Interpolation technology is the foundation of path's control in the CNC system, and it is a crucial segment in the promotion of CNC technology. The efficiency of interpolation algorithm will directly affect the performance of the CNC system. Especially, spline interpolation is the key technology of high-speed and high-precision CNC machining. At the same time, embedded CNC system still has a broad application prospect for its miniaturization and real-time. Therefore, the development of a high-efficiency spline interpolation algorithm for embedded CNC system is of great value in application.First, through the study of spline curves widely used by CNC system, specific construction algorithms for the matrix representations of parametric cubic spline curve, B-spline curve and NURBS curve are respectively presented in this paper. The simulation is carried out in the Visual C++ environment to verify the feasibility of the algorithms. Two-dimensional and three-dimensional spline curves are extracted from MFC GDI and OpenGL by simulation.Then a novel real-time spline interpolation algorithm is designed based on the Taylor expansion. According to the requirements of machining precision, speed and acceleration, the algorithm achieves controllability of chord error, centripetal acceleration and S-shape acceleration-deceleration through the adaptive chord length. Furthermore, a spline interpolation algorithm for NURBS curve based on its representation in homogeneous coordinates is proposed. The algorithm is simulated on PC to demonstrate the efficiency through analyzing the chord error, feed rate and tangential acceleration.Finally, the construction algorithm and interpolation algorithm of NURBS curve are implemented in an independent-development embedded CNC system, and then a real-time processing is successfully conducted. In consequence, the function of NURBS direct interpolation comes true in the embedded CNC system.