Multi Objective Optimization Design And Temperature Field Research On Coreless Permanent Magnet Linear Synchronous Motor

Permanent magnet linear synchronous motor(PMLSM)has the advantages of high thrust density,fast response speed and high transmission efficiency,and are widely used in high-precision industrial production such as laser engraving machines,laser cutting machines and semiconductor manufacturing.Therefore,in this thesis,according to the demand of a laser engraving machine,the ironless permanent magnet linear synchronous motor is studied to avoid the influence of positioning force from its own structural characteristics,focus the problem of generating thrust fluctuation on the sinusoidality of the air gap magnetic field,and propose a trapezoidal Halbach consequent-pole topology,which improves the motor thrust stability and reduces the cost of magnetic pole.At the same time,the output thrust of the motor is closely related to the winding current,which inevitably leads to the temperature rise of the winding when achieving higher output thrust,while the ironless permanent magnet linear synchronous motor has poor heat dissipation because there is not enough space for heat dissipation.From the consideration of motor safety,we should pay attention to its temperature rise characteristics to avoid safety accidents caused by high temperature.This thesis aims to optimize the thrust performance of ironless permanent magnet linear synchronous motor,reduce the manufacturing cost and operate safely under different overload conditions.The equivalent magnetization intensity method,superposition principle,finite element method and heat transfer law are used as modeling methods to study the thrust characteristics and temperature rise characteristics of the motor,propose the trapezoidal Halbach consequent-pole structure design,determine the maximum permissible overload operating time of the motor in continuous operating system,and verify the feasibility and effectiveness of the design through simulation.The main work of this thesis is as follows.(1)Based on the Halbach pole array and consequent-pole characteristics,the trapezoidal Halbach consequent-pole(THCP)structure topology is proposed,its overall structural characteristics are described,and the air-gap magnetic field harmonic components,no-load counter-electromotive force,average thrust,and thrust-to-volume ratio of the motor are analyzed in the static field state,transient no-load state,and load state,and compared with the Halbach consequent-pole(HCP)and double Halbach(DH)pole structures.The results show the rationality of the pole design and provide an important theoretical basis for the subsequent study.(2)THCP-PMLSM is modeled and key parameters are analyzed for thrust fluctuation,average thrust and thrust-to-volume ratio.First,the model is divided into air gap layer and magnetic pole layer.Then,the equivalent magnetization intensity method is used to establish an analytical model of the air gap magnetic field,and the trapezoidal magnetic pole is divided into a combination of a rectangle and two right-angle triangles,and the superposition principle is used to calculate the superposition of the air gap magnetic field in each part.Finally,the analytical models of average thrust,thrust fluctuation and thrust-to-volume ratio are established in turn.Based on the analytical relationships and parametric modeling analysis in the finite element simulation software,the pole pitch,main permanent magnet width and trapezoidal pole inclination angle are selected as the parameters to be optimized.(3)The Kriging agent model is introduced to improve the accuracy of model calculation.First,the Latin hypercube sampling method is used to establish the initial sample database,and then the Kriging proxy model is established based on this,and the proxy model is updated to improve the prediction accuracy by combining the EI additive point criterion,and the proxy model is optimized by multiple swarm genetic algorithms.This has resulted in an increase in the average thrust and thrust volume of THCP-PMLSM and a significant reduction in thrust fluctuation.Compared with HCP-PMLSM with the same amount of permanent magnets,THCP-PMLSM has better stability under different working conditions.Finally,through the economic analysis,the cost and utilization rate of motor permanent magnets are considered,and THCP-PMLSM has higher practical application value compared with HCP-PMLSM and DH-PMLSM.(4)The temperature field of the primary part of the motor is calculated to determine the maximum operating time of the motor under different overload conditions in the continuous operation regime.Firstly,the basic assumptions of the motor primary are made by the law of heat transfer to determine the boundary conditions of the model.Secondly,a 3D model of the motor primary is established in COMSOL Multiphysic simulation software,relevant physical parameters and material parameters are defined,and temperature field calculations are performed for the motor in two states,natural cooling and air cooling,to obtain the temperature rise characteristics of these two states.Finally,different overload currents are passed in the windings to calculate the maximum operating time.The study found that using a trapezoidal Halbach alternating magnet pole structure improves the stability and performance of motors while reducing costs.It also calculated the maximum overload time for safe motor operation.These findings provide a crucial theoretical foundation for using ironless permanent magnet synchronous linear motors.