Research On Permanent Magnet Linear Synchronous Motor With Low Normal Force Ripple

The single-side flat-plate core servo-used permanent magnet linear synchronous motor(PMLSM)with the characteristics of big thrust,high power density,has been applied in many fields.Nonetheless,due to the influence of slot effect,end effect and magnetic field harmonics,there is the large normal force ripple between the primary and secondary when the PMLSM is operating,the normal force ripple will influence the accuracy of machine tool greatly.The producing mechanism and weakening methods of the normal force ripple in flat-plate core PMLSM are systematically theoretical analysis and research in this dissertation.Main works are listed as follows:Firstly,to lower the ripple,the effects of electromagnetic parameters on the vibration should be considered when the parameters are determined.An fractional slot structure of 14 poles and 12 slots is adopted.This kind of structure has the advantages of no-load electromotive force with few high harmonics and high thrust density.The motor winding adopts double layer winding,which has better electromagnetic performance and torque performance.Secondly,from the perspective of air gap magnetic field energy,the relativity of the normal force and tangential electromagnetic thrust is analyzed using analytical method.By analyzing the generating principle of the normal force ripple of single-side plate PMLSM,it is found that the end effect and the slot effect are the main reasons of the normal force ripple of linear motor.The effect of the end effect on the normal force ripple of linear motor was verified by the unslotted model of the linear motor,and the effect of the slot effect on the normal force ripple of linear motor was verified by the linear motor of infinite long primary.The simulation results show that the influence of slot effect on the normal force ripple of the linear motor is 28%,which cannot be ignored.Finally,the normal force ripple based on copper sheet structure PMLSM is reduced by 12%.From the angle of normal air gap magnetic density,the copper sheet structure is used to weaken the high harmonic of normal air gap magnetic density.The normal force and thrust ripple performance of PMLSM before and after copper sheet structure were compared and analyzed,concluded the normal force and thrust ripple of copper sheet structure PMLSM is lower than before the copper sheet structure of PMLSM.The modal analysis of the primary cores of linear motor is calculated to obtain the modal modes and inherent frequencies of the motor,and the harmonic response analysis of the primary cores of two motors is carried out to calculate the frequency response of the primary core of linear motor.By observing the frequency response curve,the two maximum values of the primary vibration speed of PMLSM correspond to frequencies at 600 Hz and 3000 Hz,which are close to the natural frequency of 605.91 Hz in the first mode and 2999.99 Hz in the 5th mode.