Design And Optimization Of Flux Reversal Permanent Magnet Torque Motor

With the continuous modernization of domestic industry,the requirements in terms of miniaturization,high precision and fast response for the transmission mechanisms of industrial robots,numerical control machines and other important manufacturing equipment are increasing.Flux reversal permanent magnet torque motors(FRMs),which can be directly connected to the load,have good performance at low speed with large output torque.Therefore,FRMs have potential application prospects in low speed and direct drive applications.As a novel type of stator permanent magnet motor,the permanent magnets(PMs)of FRMs are located in the stator,while the rotor consists of laminated silicon steel sheets.FRMs have the advantages of simple structure,high torque density and fast dynamic response.In addition,the temperature of PMs in FRMs is easy to monitor and control.However,due to the doubly salient structure,FRMs suffer from large cogging torque and significant fluctuations of load torque.At present,the optimal design on the torque performance of FRMs has become the focus in research.This thesis introduces the research background and significance of FRMs firstly.Based on relevant domestic and foreign literatures,the history of development and status of research about FRMs are reviewed and the structural characteristics as well as corresponding advantages are summarized,which indicate that FRMs are suitable for low speed and direct drive applications.Secondly,the typical structure and operating principles of FRMs are elaborated in detail.Based on permanent magnet magnetomotive-air gap relative permeance model,basic equations of FRMs are deduced,and the analytical expressions of important electromagnetic characteristics such as flux linkage,electromotive force and torque are obtained.The deduced equations of FRMs not only contribute in improving the understanding of working principles of FRMs,but also revealing the relationship between the structural parameters and the electromagnetic characteristics.Then,referring to the preliminary design scheme of the stator permanent magnet motors,the structural parameters of a 12/29 poles prototype motor were determined by empirical formulas and preliminary calculations.Finite element analysis(FEA)on the performance of the prototype is performed by using FEMM tools and the results show that the preliminary design is reasonable.However,FEA simulations also reveals the large torque fluctuations of the prototype.By comparing the electromagnetic characteristics of the prototype calculated by FEA and the analytical method,the accuracy of the deduced equations is verified since the results show good agreement with each other.Finally,mathematical models of the random search method(MRS)and the improved random search method(IMRS)are introduced in detail.In order to minimize the torque fluctuation of the prototype,IMRS is applied to the optimal design and multiple structural parameters are picked up as optimized variables.The result of the optimization shows a significantly decrease of the torque fluctuation and the electromagnetic performance of the prototype meets design requirements.By analyzing the specific performance of both MRS and IMRS in the optimization of the prototype,the effectiveness and relatively higher reliability of IMRS are verified.