Researches On Behavior Of Vibration And Noise In Permanent Magnet Synchronous Motorized Spindle In Vertical Machining Center

Permanent magnet synchronous motorized spindle is the key part of NC machine tool,and plays an important role in the manufacture and processing of products.It has the advantages of compact structure,small inertia,wide speed range and good dynamic performance,but the vibration and noise of motorized spindle directly affects its comprehensive performance.The main factors causing electromagnetic vibration and noise of motorized spindle are as follows: firstly,the harmonic amplitude caused by radial electromagnetic force produced by air gap magnetic field;secondly,the approximation degree of radial electromagnetic force and harmonic frequency to the natural frequencies of the modals of motorized spindle components.In this paper,the electromagnetic vibration and noise characteristics of a 4-pole 18-slot permanent magnet synchronous motorized spindle are studied by finite element method.Firstly,the two-dimensional model of permanent magnet synchronous motorized spindle is established by ansoft software,and the air gap magnetic field of the motorized spindle is simulated by finite element method.The radial and tangential flux density curves with time and position are obtained.The electromagnetic force density waveforms with time are plotted,and then the harmonic analysis and calculation are carried out.The radial electromagnetic force is introduced into matlab to get the spectrum analysis.It is concluded that the radial electromagnetic force is the main source of exciting force which causes the electromagnetic noise of the motorized spindle.The analysis and calculation of the air gap magnetic field and electromagnetic force provide the necessary theoretical basis for the study of the vibration and noise of the motorized spindle later.Secondly,this paper establishes the three-dimensional model of the main parts of synchronous motorized spindle,and carries out modal analysis of the main parts.The vibration modes and natural frequencies of stator core,rotor core and motorized spindle are obtained.The frequency of the radial electromagnetic force on the stator of the motorized spindle is compared with the natural frequencies of the main components to ensure that the resonance of the motorized spindle will not occur in normal operation.Finally,the electromagnetic force extracted by ansoft is applied to the stator teeth in workbench,and the vibration characteristic diagram of the motorized spindle is obtained.Then,a spherical radiation model with radius of 1 m is established to analyze and calculate the noise at the spherical surface.The surface profile of the pole of permanent magnet synchronous motorized spindle is optimized,and the torque ripple is reduced by slotting the pole surface to suppress the vibration and noise.The groove includes arc,rectangle,triangle,trapezoid and other shapes.The results show that the trapezoidal groove with appropriate depth on the surface of the magnetic pole has the best effect on the optimization of the spindle torque ripple.It can significantly reduce the torque ripple without reducing the average torque,and has the effect of suppressing the vibration and noise of the motorized spindle.