| The electric spindle is the core component for ultra-high speed grinding.The permanent magnet synchronous electric spindle has wider application in high-precision CNC machine tools due to its high power factor,high precision,low temperature rise and good performance index.There is complex electromagnetic coupling between the stator and rotor inside motorized spindle,which plays a vital role in the processing performance of the electric spindle.However,there are still many deficiencies in the research of electromagnetic coupling of electric spindle.Especially the research on the influence of electromagnetic characteristics,electromagnetic force and magneto-thermal coupling under rotor eccentricity is not deep enough.In this paper,aiming at the electromagnetic coupling characteristics of permanent magnet synchronous electric spindle and the influence of rotor eccentricity on the working performance of electric spindle,the electromechanical magnetic-thermal coupling characteristics of stator and rotor under concentric,static eccentricity,dynamic eccentricity and mixed eccentricity conditions are studied in depth.The main research contents include:1.According to the electromagnetic field theory and the magneto-electric coupling principle of the air gap magnetic field of permanent magnet synchronous motorized spindle,the functional relationships of air gap magnetic permeability,magnetomotive force and integrated electromagnetic force density under mixed eccentricity are derived.2.Taking the permanent magnet synchronous motorized spindle with rated speed 7000 RPM and power 41 KW as the research object,a two-dimensional finite element model of motorized spindle is established based on Ansoft Maxwell finite element software.Aiming at the difficulty of mesh generation in pretreatment,the expression of precise mesh generation and the method of odd-layer mesh generation are obtained by numerical analysis of MATLAB,which breaks the limitation of even-layer mesh generation in motion domain.3.By adjusting the eccentricity and rotation center of the finite element model of electromagnetic field,the changing nature of electromagnetic characteristics under different air gap eccentricity is analyzed,and the trends of magnetic line,radial electromagnetic force density,comprehensive electromagnetic force waveform and harmonic proportion under static eccentricity and dynamic eccentricity are obtained.The parametric analysis of electromagnetic force under mixed eccentricity is carried out,and the electromagnetic force density,the comprehensive electromagnetic force curve and the stiffness characteristic curve are obtained,which further explored the electromagnetic characteristics closer to the actual working conditions.4.Aiming at the drawbacks of the slow calculation of finite element software and the disadvantage of multi-physical field coupling analysis,a semi-analytical model of three-dimensional tilt eccentricity of permanent magnet synchronous motorized spindle is established.The numerical analysis method of its key electromagnetic characteristics is given by MATLAB programming calculation,and the accuracy of its method and analysis results is verified by comparing with Maxwell finite element method.The variation law of unbalanced electromagnetic force and electromagnetic stiffness with the inclined angle is obtained,and the results show that the inclined state increases the fluctuation of the spindle and decreases the stability of the spindle.5.In order to accurately calculate and analyze the internal temperature field distribution characteristics of the electric spindle,the magnetic-thermal coupling simulation of the motor is carried out by using the method of correlation and interaction between Ansoft Maxwell and ANSYS Workbench.The time-domain variation curves and distribution characteristics of copper loss,iron loss and permanent magnet eddy current loss are obtained.The temperature rise law of each part in the motor is analyzed,and the influence of rotor eccentricity on the internal temperature field of the electric spindle is studied. |
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