Design And Analysis Of Magneto-thermal Bidirectional Coupling Of Low Ripple Built-in Servo Permanent Magnet Motor

Servo systems have been widely used in recent years,and are increasingly used in industrial robots,CNC machine tools and other application scenarios.With the rapid development of industrial information technology,the development direction of servo motors has become more and more clear: that is,to achieve lightweight,automated,and high-precision.Although the advantages of servo motors are outstanding,there are still many imperfections in their research,which are worthy of further study.Based on the above-mentioned related background,this article has launched a research on permanent magnet synchronous motors in the servo field.First of all,in the servo field,there are installation size requirements for the motor,and the motor needs to have the performance of high torque density,so it is proposed to research and design a built-in permanent magnet motor.According to the general design principles of permanent magnet synchronous motors,the initial design of the motor was carried out,and the performance differences were analyzed by comparing a variety of built-in topologies,and it was concluded that the V-shaped structure is more suitable for this design.Import the initial model into the finite element software,simulate the performance of the motor,and adjust the motor parameters until the electromagnetic performance requirements are met according to the results,and finally determine the electromagnetic design plan of the motor.Secondly,the servo motor needs to meet the requirements of high positioning accuracy and low ripple,which leads to torque ripple in the motor.Therefore,it is necessary to study how to effectively weaken the cogging torque.The work is embodied in: discuss the mechanism of cogging torque;analyze the Fourier series expression of cogging torque when the magnetic pole is offset,and give the calculation formula and derivation method of the magnetic pole offset angle;the results show that the magnetic pole is offset It has obvious weakening effect on cogging torque.Then,multiple methods of optimal pole arc coefficient,magnetic pole offset,and rotor eccentric pole design are combined and applied.The results show that the combination of multiple methods can reduce the cogging torque and torque ripple better,and the electromotive force and current waveforms are more sinusoidal.Then,the boundary condition of high torque density needs to be limited by temperature rise,so the motor temperature needs to be calculated.Using the thermal circuit method to compile the motor temperature calculation program on Matlab,and comparing with the results of the current mature motor thermal evaluation software Motor-cad,it shows that the thermal circuit program can calculate the motor temperature rise more accurately.At the same time,considering that the magnetic properties of permanent magnet materials are easily affected by temperature,it is proposed to couple the magnetic field and the thermal field in both directions,update the heat source in real time,and iteratively calculate the temperature results to achieve more accurate temperature evaluation.Finally,the genetic algorithm is used to optimize the design of the motor,and based on the weight coefficients,a multi-objective optimization function is constructed for the optimization objectives such as average output,torque ripple,and waveform distortion rate,and the global optimal solution of the key dimension parameters is obtained.The finite element results show that after the genetic algorithm optimization,the performance of the motor optimization objective has been further improved.