| The production and manufacture of complex curved parts is of particular importance in the aerospace,automotive,ship,tool and die industries.Such part contouring is often represented in CAD/CAM software using NURBS spline curves(non-uniform rational B-splines).Therefore,NURBS curve and surface real-time interpolation technology has become a hotspot in the research of numerical control interpolation technology in recent years.NURBS curve surface interpolation function has become one of the iconic functions of modern high-performance CNC system.However,most of the traditional CNC systems only have linear and circular interpolation functions.When machining non-linear or circular curved surfaces,the high-order curved surface must be discretized into a large number of small straight segments,resulting in long and frequent processing codes.Acceleration and deceleration and machine vibration;Although foreign high-end CNC systems such as FANUC,SIEMENS,and Mitsubishi have been equipped with NURBS spline interpolation,there are contradictions between high-speed machining and finishing.Therefore,research on an interpolation and control algorithm suitable for high-speed machining is of great significance for improving the performance of high-speed machining CNC systems.Based on the analysis of the development status and trend of high-speed machining,this paper makes an in-depth study on the NURBS curve interpolation technology in high-speed CNC machining.It introduces the evaluation index of CNC numerical control interpolation algorithm in detail and carries on the theoretical basis of NURBS curve.The combing,the definition of Bezier curve,B-spline curve and uniform Bspline curve are expanded and compared.The method of determining the non-uniform rational B-spline node vector,the influence of weight factor on the shape of NURBS curve and the NURBS curve are summarized.The formulas for increasing and decreasing the order are analyzed,and the properties,advantages and disadvantages of the NURBS curve are analyzed in depth.The NURBS curve bow height error-feed rate adaptive interpolation algorithm is studied and given,which can make the machine interpolate the workpiece with the maximum feed speed under the premise of satisfying the machining accuracy requirements.Accuracy and optimization of interpolation speed.However,considering the motor acceleration and deceleration caused by the speed adjustment in the large curvature area of the curve,the machine flutter is affected,which affects the smooth running of the machine tool.Therefore,based on the definition of the bow height error,an S-type acceleration/deceleration control algorithm is proposed,which is designed to meet the requirements of high-speed and highprecision machining and the processing process is smooth and shock-free.At the same time,the real-time calculation method of feed rate distribution and forward interpolation curve length under S-type acceleration and deceleration is studied.Finally,the program is programmed and simulated by VC++ software based on adaptive speed real-time interpolation algorithm and experimental simulation,prove the correctness and feasibility of the algorithm. |
