| CNC system is an important embodiment of the development in modern manufacturing industry.The requirements of CNC system for trajectory processing are gradually improving.Therefore,in the high-speed machining of complex curve and small segment trajectory processing,the quality of interpolation methods will greatly affect the generation and machining accuracy of trajectory.Non uniform rational B-spline(NURBS)curve interpolation technology can effectively retain the characteristics of curve,improve the shape quality of machining surface,obtain high speed and accuracy and improve machining efficiency.In this paper,NURBS curve interpolation technology is studied.The main research contents are as follows:Aiming at the error problem of traditional NURBS curve fitting,the data points are identified and deleted according to the processing method of small segment trajectory and the restriction conditions such as segment angle and adjacent length.In order to improve the accuracy of curve fitting,a NURBS curve interpolation fitting method based on the curvature information of discrete points is proposed,and the original NURBS curve is modified by reverse seeking control vertices.The effectiveness of the proposed method is verified by an example.The principle of NURBS curve interpolation is analyzed.Aiming at the problems of velocity limitation and parameter calculation in fitting curve curvature,a comprehensive velocity constraint model of interpolation error is established.The interpolation calculation effect of Taylor expansion method and Runge Kutta method under the model is analyzed.An improved Runge Kutta correction method based on the velocity fluctuation rate is proposed to iterate and modify the interpolation parameters,which improves the parameter calculation effect.An adaptive NURBS curve interpolation method based on flexible acceleration and deceleration is proposed.This method considers the curvature information and the feature points in the fitting stage to segment the curve parameters adaptively,and divides the interpolation interval reasonably to improve the interpolation speed.Combined with the improved S-shaped acceleration and deceleration control algorithm,the strict restriction in the interpolation cycle is implemented to dynamically modify the interpolation parameters such as acceleration,so as to realize the real-time adjustment of feed speed to meet all the constraint model conditions.The proposed method is compared with the traditional interpolation,and the simulation results are verified and compared.Finally,the simulation results show that the proposed NURBS curve adaptive interpolation method can adjust the segmentation parameters according to the curve curvature information and the speed extremum.At the same time,the interpolation parameters can be accurately calculated under the comprehensive speed constraints.Finally,the efficient speed planning is carried out,which meets the requirements of speed and acceleration.The proposed overall scheme can be applied to the high-speed machining of NURBS curves,which meets the needs of current research,and proves the effectiveness and correctness of the method proposed in this paper. |
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