The Research On Interpolation Algorithm Of NURBS Curve Based On Milne-Hamming Method And Acceleration/Deceleration Control Algorithm

Numerical control technology is the basis of manufacturing field.With the development trends of modern machining towards refinement,high efficiency and complexity,the modern numerical control system is also developing towards high precision,integration,intelligence and networking.For some complicated curves and surfaces,the traditional interpolation of lines and arcs can no longer achieve high speed and high precision machining.NURBS curve has been widely used as a mathematical method to define the geometric shapes of industrial products.Therefore,a set of interpolation algorithm and acceleration/deceleration control algorithm is studied based on the NURBS curve of three order,so as to achieve smooth machining,high precision and high efficiency.Firstly,a NURBS curve interpolation algorithm based on Milne-Hamming method is proposed.Combining the Runge-Kutta method and the modified Milne-Hamming predictive-correction formula,the principle and steps of the interpolation algorithm are described in detail.Then a three-dimensional NURBS curve is used to compare the algorithm with the other three interpolation algorithms.The correctness and superiority of the algorithm are verified by the comparison of speed volatility and correction times.Secondly,a novel speed planning algorithm based on the improved S-type acceleration/deceleration model is proposed.The pretreatment work and the calculation and derivation of the modified S-type acceleration/deceleration model are introduced in detail.According to the characteristics of the model and the speed characteristics of the curve segment,the curve segments are divided into four cases.Then it is compared with adaptive speed algorithm and S-type acceleration/deceleration algorithm.Simulation results show that the algorithm can effectively reduce the speed fluctuation,ensure the machining accuracy and improve the machining efficiency.Finally,the hardware platform and software platform of embedded CNC system based on OMAP3530 developed by the Laboratory are briefly introduced.The Bootloader transplantation and other operations are described.Qt/E is used to set up the operation interface of CNC system and related functions are added.The feasibility and availability of the algorithm are verified by a machining example.