Research On Feedrate Scheduling And Trajectory Smoothing Methods For High Precision Machining Of Linear Segments

Manufacturing is an important pillar of the national economy,and the CNC machine tool is the "industrial mother machine" of the manufacturing industry.As the core and brain of the CNC machine tool,the CNC system is an important symbol to measure the development level of the national equipment manufacturing industry.As the most commonly used CNC machining mode,continuous linear segments(G01)machining can process complex curved surfaces.However,the poor geometrical continuity between linear segments trajectories leads to acceleration oscillation,which affects machining accuracy and smoothness.In order to achieve high precision and smooth machining of micro-segments,this paper explores key technologies such as acceleration and deceleration algorithms,corner transition algorithms and look-ahead scheduling algorithms in micro-segment machining,with the main research content as follows:(1)In order to improve the flexibility and the efficiency of acceleration and deceleration in micro linear segments machining,the traditional trigonometric acceleration and deceleration control algorithm with good continuity is improved by adding a uniform jerk phase to motion model to improve the continuous acceleration capability of the algorithm.On the basis of ensuring continuous jerk,the acceleration efficiency is further improved.At the same time,considering different motion parameters,the improved motion profile is divided into eight cases to adapt to the feedrate scheduling under various working conditions and to improve the look-ahead scheduling efficiency.(2)In order to improve the continuity of the linear segments and effectively control the dynamic performance of each axis to ensure smooth machining,a one-step corner transition algorithm based on improved trigonometric acceleration and deceleration is proposed.The algorithm makes the velocities of adjacent linear segments to be vector-summed during the transition stage,and completes the trajectory smoothing directly during the feedrate scheduling phase,improving the continuity of the interpolated trajectory and achieving effective control of the contour error and the dynamic performance of each axis.The algorithm improves the efficiency of the interpolation operation and the tracking accuracy of the servo control on the basis of ensuring machining efficiency.(3)Aiming at the problem of poor transition efficiency of one-step corner transition at short linear segments,a look-ahead scheduling algorithm based on short line segment transition optimization is proposed.The short line segment is selected according to the corner error,and then the corner transition is optimized for the short line segment under the contouring error constraint to achieve overlapping processing of the transition curves and improve the machining efficiency of the one-step corner transition.(4)Finally,the algorithm is embedded in laboratory CNC system for simulation and experimental validation.The practicality and advantages of this method are verified by comparing with other acceleration and deceleration algorithms,corner transition algorithms and look-ahead scheduling algorithms.The results show that,on the basis of excellent machining efficiency,the algorithm in this paper can better achieve continuous higher-order speed and control the dynamic performance of each feed axis,and effectively improve the interpolation efficiency and tracking accuracy in corner transitions.