Research On Robust Thermal Error Modeling Of CNC Machine Tools Based On Interval Optimization

As the "industrial master machine",the machining accuracy of CNC machine tool is closely related to the development direction of the whole manufacturing industry.It is the embodiment of the country's manufacturing capacity and has a far-reaching impact on the country's overall industrial development.There are six error sources that will affect the machining accuracy of CNC machine tools,Among them,thermal error accounts for a large proportion of the total error.For high-precision CNC machine tools,the thermal error accounts for even close to 70% of the total error.Therefore,reduce the influence of thermal error play an important role in improve the machining accuracy of CNC machine tools.Summarize the relevant research,we can find that the main methods to reduce the influence of thermal error in the world are: the improvement of structure design,the use of new materials,temperature control,modeling to compensate thermal error by software,etc.Among them,"modeling to compensate thermal error by software" has been widely studied because of its excellent engineering practicability and economy.Using this method to obtain good compensation effect requires in-depth research on the following four aspects: standardized and accurate thermal error measurement,optimized selection of temperature sensitive points,robust and accurate thermal error modeling,and efficient and economic thermal error compensation.In this paper,leaderway-v450 three-axis C-type vertical machining center is taken as the research object,and a large number of long-term experiments and data analysis are carried out on the above four aspects.The selection of temperature sensitive points,thermal error modeling and standardization of thermal error measurement methods are mainly studied.The main contents of this paper are as follows:1)This paper studies the selection technology of temperature sensitive points,analyzes the mathematical principle of the traditional method of selecting temperature sensitive points based on fuzzy clustering and grey correlation degree,points out the defect mechanism of temperature sensitive point selection variability,and puts forward a robust temperature sensitive point selection method.The validity of this method to eliminate the change of temperature sensitive points and the correctness of the selected temperature sensitive points are verified by 12 batches of experimental data in the whole year.2)The thermal error modeling technology is studied.The mathematical mechanism of multiple linear regression modeling algorithm,ridge regression modeling algorithm and principal component regression modeling algorithm is analyzed.Different thermal error compensation models of CNC machine tools are established by using different algorithms.The prediction accuracy and robustness of different models are compared and analyzed.It is pointed out that principal component regression has greater engineering value than ridge regression practicability.Further research points out that the thermal error compensation model of machine tool has a jump interval affected by the ambient temperature,and puts forward the concept of temperature sensitive interval of CNC machine tool.Aiming at the temperature sensitive interval of CNC machine tool,the segmented point selection algorithm of temperature sensitive interval is proposed based on interval optimization to solve the problem,and the robust thermal error modeling of CNC machine tool based on interval optimization is realized.Which further improved the prediction accuracy and robustness of the model.3)The standardization of thermal error measurement method is studied.The current national standard on thermal error measurement is mainly aimed at the spindle idling condition of CNC machine tools.There are some problems in the measurement of thermal error of machine tool in real cutting state and the measurement of multi-point thermal error of machine tool worktable.In order to standardize the measurement of thermal error of CNC machine tools under these two working conditions,two measurement standards were studied and put forward,which laid a foundation for the future research of thermal error compensation of machine tool under complex working conditions.These two standards have passed the audit of Anhui market supervision and administration bureau,and have been approved for release as local standards of Anhui Province.