Research On Key Technology Of Intelligent Control The Bearing Preload Of Motorized Spindle Based On Piezoelectric Actuators

Intelligent manufacturing as the core technology in the new round of industrial revolution.It has great significance to the development of manufacturing industry.Intelligent equipment with functions of analysis,reasoning,judgment,learning and decision can improve the accuracy and efficiency of manufacturing which requires the combination of new sensor,module,advanced control and optimization technology,fault diagnosis,special technology and precision technology etc.High grade CNC machine is the basis of manufacturing industry.So the intelligent research of high grade CNC will directly determine the core competence of a country's manufacturing industry.The intelligent research on motorized spindle has a great significance to improve the performance of high grade CNC machine and the quality of the product.This thesis focuses on the most widely used angular contact ball bearings in high speed motorized spindle.Research on the driving performance of piezoelectric actuators.And research on the bearings preload intelligent control method of spindle based on piezoelectric actuator.The main research work were as follows:(1)The 7009C angular contact ball bearings were quasi-static analyzed by Hertz contact theory.The principal curvature,principal curvature difference,displacement-load factor of bearings were calculated.The contact angle and contact load of' bearing roller under different speed and positioning preload conditions were calculated.Newton-Raphson method was used to calculate the minimum bearing preload to prevent the gyroscopic slip effect.The spindle bearing was simplified to a single degree of freedom model.Vibration of simplified spindle bearing system was analyzed by MATLAB/Simulink.(2)A force output characteristics of piezoelectric actuators test device was designed.Experimental analysis the force output characteristics of PSt150/4/7VS9 piezoelectric actuators under different initial preload,voltage frequency,cycle working,voltage travel were obtained by the maximum output force,average hysteresis degree,maximum deviation,drift amount,cycle delay of curves and other parameters as evaluating indexes.The piezoelectric actuators have the best output under the condition of 150N preload and 1 Hz voltage frequency.The hysteresis loops of piezoelectric actuators were predicted and analyzed by the BP neural network which the input voltage based on the working principle of Preisach model.(3)An intelligent control method for bearing preload of spindle is proposed.ORBIT36CNC surface grinder and Kistler9257B plane dynamometer was used to collect grinding force signal.Vibration of simplified spindle bearing system was analyzed by MATLAB/Simulink.An intelligent control method for spindle bearings based on piezoelectric actuators was proposed.The results showed that the preload of bearings were better controlled by the initial control and fine tuning based on the change of performance parameters during machining.A set of strategies based on spindle bearing preload control by piezoelectric actuators bearings was proposed by this thesis.It provide a foundation for the construction of intelligent motorized spindle.