A practical real-time non-uniform rational B-spline curve interpolator for computer numerical control machining

Non-uniform rational B-spline (NURBS) interpolator, a key technique in computer numerical control (CNC) machining, has many advantages over linear and circular interpolator. A practical real-time NURBS interpolator based on an off-line algorithm, which is developed to handle the limitation of velocity and acceleration, is presented in this article. Two processing modules are employed to realize the real-time interpolator. In one module, a NURBS curve is split into shorter NURBS curves or approximated as continuous line segments according to the minimum splitting length first, and then the velocity planning of a short curve is applied. In the other module, the interpolation according to the velocity planning results is implemented. The proposed algorithm realizes the real-time velocity planning and interpolation of a NURBS curve regardless of the curve length or the continuity. It is also applicable to three-dimensional surface designed by computer-aided design system, which is composed of multiple NURBS curves or both NURBS curves and continuous line segments. Both the simulation and experiment results have proved the effectiveness of the proposed practical real-time NURBS interpolator.