Reserch On Adaptive Federate Interpolation Method And Look-Ahead Motion Planning Based On NURBS Curve

Computer numerical control(CNC) is a key technology in modern machining industry.It plays a vital role in manufacturing to achieve flexible automation,integration,and intelligence.The interpolation and acceleration and deceleration control are two core functional modules of CNC machining technology,which have great impacts on machining precision and efficiency. With NURBS curve have a wide range applications in CAD / CAM field, the new NURBS curve interpolation technology has been proposed,and gradually become the core of numerical control technology.At present,NURBS interpolation algorithm proposed by the vast majority of around how to solve the problems which conflicts of the machining accuracy and processing speed.Under normal circumstances,the greater the feedrate,the greater interpolation error may be caused.Curve in different regions of the feedrate limits are different.When curvature has significant changes in processing path,it is not economy that the feedrate has been reduced in whole processing path in order to satisfy certain request of precision in certain sensitive areas of curvature.To Solution this problem,the adaptive federate interpolation method was put forward.However,the federate has constantly changinging in the adaptive federate changing regions,this change in feeding mode may lead to acceleration and deceleration of the machine tool.If faderdate control is not well,it will lead to a higher acceleration and jerk.Thus affecting the smooth running of machine tools.At the same time,it may lead to shock and vibration in the process of machining.In response to this problem,A smooth adaptive NURBS interpolation algorithm with limited acceleration and jerk constraints is proposed.Considering the relationship between federate and interpolation error as well as flexible acceleration/deceleration mechanism,the 2th order Taylor expansion is employed for next point parametric iteration.The federate is adaptively changed according to the demand of interpolation precision.In the adaptive area,an acceleration/deceleration and jerk limited S curve is used to replan the federate,to get smooth federate profile.With this interpolator,steady and fast federate,confined interpolation error,and a smooth and shock-free machining process is obtained,which enhances the machining efficiency an quality.Compared with the traditional interpolation methods,the interpolation algorithm to maintain the performance of high-speed and high precision machining,and can inhibit the process of the resulting interpolation error and speed fluctuation contours.Through the real-time simulation the interpokation trajectory of NC machining process,analysis of the interpolation algorithm accuracy, speed and acceleration and deceleration of the outcome of the case,and proved the correctness of the interpolation algorithm,the effectiveness and real-time performance.