Research On Velocity Planning And Interpolation Algorithm For NC Camshaft Grinding Based On Workpiece Constant Linear Velocity

In CNC camshaft grinding,the smoothness of feed velocity curve is of great significance to improve the efficiency of camshaft manufacture and reduce the error of profile.In order to solve the problem that the leading axis velocity and acceleration are discontinuous when the discrete data in the leading axis velocity table are processed by linear interpolation,a camshaft grinding velocity planning and interpolation algorithm based on the workpiece constant line velocity is proposed in this paper.The velocity table is fitted into a spline velocity curve,and the velocity planning can be carried out in real time in the CNC system to drive the motion of the drive shaft,so as to achieve high precision and high efficiency camshaft grinding.Aiming at the problems of low accuracy and low efficiency of small line segment interpolation in constant rotating speed grinding of camshaft in high speed machining,the principle of camshaft contour forming in constant line speed is studied,and the kinematics model of camshaft constant line speed grinding is established in this paper.The key technologies of joint motion control of rotating axis and straight axis in the interpolation process are analyzed,and the differences,advantages and disadvantages of the dynamic cooperation of the two axes and the following control technology are compared.The numerical control system uses linear interpolation to process the discrete position-velocity data in the user-defined velocity table,which leads to discontinuous velocity curve,and the problem of sudden change of velocity and acceleration of the leading axis occurs during machining.The method of cubic uniform B-spline fitting is proposed to interpolate and fit the data in the velocity table to form a smooth 2-D velocity curve.The numerical control system uses this algorithm to fit the velocity table into spline velocity curve when loading the velocity table,and stores control points and other information,which is ready for the subsequent interpolation process.Aiming at the problem that it is difficult to calculate the interpolation increment by using the small line interpolation algorithm after fitting the two-dimensional velocity curve by numerical control system,and that the acceleration of the leading axis exceeds the limit during the starting and stopping of the machine and the switching of the velocity during the grinding process,a real-time velocity planning algorithm of the leading axis is proposed in this paper.By establishing the finite state machine model of the velocity control of the leading axis and combining with the S-type acceleration and deceleration planning under the discrete condition,the interconversion and interpolation of the acceleration,deceleration,velocity table execution and feed adjustment during the operation of the CNC system are planned.On the basis of the above research,the camshaft grinding leading axis interpolation function software module based on the velocity table was developed,and the simulation test and actual manufactur verification were carried out.Experimental results show that the algorithm proposed in this paper can run stably in the CNC system,ensure the smoothness of the velocity curve of the leading axis,and effectively improve the accuracy of camshaft grinding.