Research And Design On Feedrate Look-Ahead Controlling Algorithms Of NURBS Interpolation

CNC plays an important role in modern equipment manufacturing industry.Highspeed and high accuray are development trend of CNC system.Traditional CNC systemonly provides liner and circle interpolation,both of them lead less accuracy.To solvethis problem,the application of NURBS interpolation techniques are increasinglycommon.With the development of computer technology,sophisticated controllingtechniques are becoming hot research.There are many sensitive points in CNCmachining,so the feed rate will rapidly change direction, it leads to reduce theprocessing quality. Look-ahead controlling technology has been implemented inmodern CNC system.it can analyze the tool path, find the dangerous points aboutfeedrate and deal with it. So its performance has a direct impact on the efficiency ofproduction and the quality of the products. Because of its status of critical, highperformance of look-ahead has been developed in the pursuit of the goal. In view ofthis, to satisfy smooth feedrate and acceleration,reduce shock and vibration impact onmachine tools caused by jerk changes, a look-ahead interpolation algorithm forNURBS curve is proposed and established a general model. first, the high speed of thefeedrate sensitive corners are established, then the curve is dividing into somesegments according to it. During the look-ahead process, first,the concept oflook-ahead distance and the optimization scheme are proposed,then, the optimizationmethod of feedrate between sensitive points is set up,finally, the determine criteria ofdeceleration point is given. Designing a look-ahead algorithm based on the cubicpolynomial acceleration and deceleration control model, the specific implementationprocess of the look-ahead algorithm is set up. By the results of simulations, allsensitive points including optimization method can be obtained with the proposedalgorithm, so it can meet the requirements to look-ahead in modern CNC systems. Bycontrast test with a S shape acceleration and deceleartion for look-aheadalgorithm,results show that this algorithm can get a smooth transition,also reduce thefrequency of jerk mutationsd.