Research On Processing Instruction Pre-Processing Method Based On Trajectory Error Prediction

With the increasing machining speed of CNC machine tools,the track error caused by the dynamic characteristics of the feed system has become an important factor affecting the machining accuracy of CNC machine tools.At home and abroad,a lot of research has been done on the compensation methods of trajectory error,and good results have been achieved.In the actual production,users face more closed CNC systems,many of the path error compensation methods will be difficult to achieve because of the closed system.In order to solve this problem,a preprocessing method based on trajectory error prediction is proposed.In order to realize this method,the rapid and accurate modeling of feed system,numerical control interpolation and speed planning simulation,trajectory error calculation and trajectory error pre compensation method will be studied in depth.By analyzing the influence of nonlinear friction on the identification accuracy of the feed system model,fast and accurate modeling of the feed system is achieved.In this method,the excitation signal of the identification experiment is designed in the form of uniform velocity plus pseudo-random sequence,the feedback position of the feed system is collected in real time,and the feed system model is identified by the least square method.Experimental results show that this method can effectively reduce the impact of low-speed nonlinear friction on the feed system,and significantly improve the accuracy of the identification model.According to the interpolation principle of the numerical control system,the interpolation simulation of linear segments and arc trajectories was realized,the characteristics of trapezoidal acceleration and deceleration and S-type acceleration and deceleration were studied,and the trapezoidal acceleration and deceleration planning during interpolation was realized.By studying different trajectory error calculation methods and implementing the trajectory error vector prediction method based on the feed system identification model according to the needs of the subject,this method calculates the minimum error value and direction of the actual machining curve by calculating the command position and its interpolation point,Provide data support for trajectory error analysis and pre-compensation.Through thesimulation experiment of circular trajectory,the accuracy of the error calculation method is verified.The simulation analyzes the different error performance and influencing factors of continuous processing of long-line segment trajectory and short-line segment trajectory,and proposes a processing instruction preprocessing method based on trajectory error prediction.This method predicts the average value of each line segment trajectory error and each axis component as the compensation amount and superimposes on the line segment command endpoint coordinates,and pre-compensates the trajectory error multiple times through loop iteration.Simulation results show that this method can be effective Reduce the machining error of CNC machine tool linkage and improve the machining accuracy of the machine tool.