Research On Thermal Error Modeling And Compensation Method Of NC Machine Tool Spindle Based On GA-LSSVM

With the continuous development of modern mechanical manufacturing technology,high-speed and high-precision CNC machine tools have gradually become the mainstream in modern mass production.However,there are still many factors affecting the improvement of maching precision,and the thermal deformation of machine tool spindle is one of the key factors.The experimental results show that thermal error is the biggest error source in NC machining,especially in the precision machining,the thermal error accounts for 40%?70%of the total error.In order to improve the machining precision of the high-precision CNC machine tools and reduce the thermal error of machine tool spindle,this thesis uses the methods of theoretical derivation,simulation analysis and measurement test to study the key technologies such as the formation mechanism of thermal error of CNC machine tool spindle system,the establishment of mathematical model of thermal error and compensation.The main research contents and conclusions can be described as follows:(1)The thermal characteristics of CNC machine tool spindle system were studied,the temperature field and thermal deformation of machine tool spindle system were analyzed by using ANSYS Workbench,and the change law of temperature and thermal deformation of spindle system was obtained,which provides reference for the preliminary determination of thermal key points.(2)The experiment of temperature and thermal error data acquisiton of machine tool spindle system was designed,and the reliability of finite element model was verified.Through the analysis of the measurement data,it can be seen that the thermal error is close to the trend of temperature change,and when the spindle system of the machine tool reaches the thermal balance,the thermal error tends to be stable.With the passage of processing time,the temperature of each part of the spindle of the machine tool no longer increases significantly after reaching a certain degree,and the thermal error of the spindle also reaches a certain stable value,indicating that there is a high correlation between temperature and thermal error.(3)Fuzzy clustering and correlation analysis methods were proposed to optimize the thermal key points of machine tool spindle in X,Y,and Z directions,and the thermal key points of spindle system in three directions were obtained.The thermal error modeling method for optimizing parameters of least square support vector machine based on genetic algorithm was introduced,and the experiment of varying working conditions was designed.The thermal error GA-LSSVM model of the spindle system in Z direction was established and its performance was verified.(4)Based on the origin migration function of the machine tool's external coordinate system,the thermal error compensation test of the CNC machine tool was carried out according to the thermal error GA-LSSVM model of the machine tool's spindle,and the accuracy of the model and the feasibility of the compensation method were verified.