Research On Design And Digital Control System For Bearingless Flux-switching Permanent Magnet Motor

In recent years,bearingless permanent magnet(PM)synchronous(BPMSM)motors have gained extensive attention due to their virtues of reliable operation,high efficiency and high power density.However,conventional BPMSM motors usually suffer from the mechanical integrity and thermal problems since PMs are usually located in the rotor.In order to overcome this problem,a novel stator-permanent-magnet type of bearingless motor,namely 12/14-pole double-winding bearingless flux-switching permanent magnet(DW-BFSPM)motor,is proposed in this paper.The proposed DW-BFSPM motor combines the excellent characteristics of bearingless permanent magnet motors and flux-switching permanent magnet motors,offering the merits of high torque and suspension force densities,small torque and suspension force ripples,low coupling between torque and suspension force and direct and convenient suspension force regulation performance.Firstly,the configuration of the proposed 12/14-pole DW-BFSPM motor is introduced.Then,the principle of torque generation is explained according to the principle of flux-switching.After that,electromagnetic torque mathematical model is built.Based on the principle of magnetic field superposition,the principle of radial suspension force generation is analyzed.And mathematical model of radial suspension force is deduced according to the Maxwell tensor method.Secondly,the general method and design flow of motor design are discussed.Then the initial parameter design scheme of DW-BFSPM motor is mainly researched.In order to maximize the torque and suspension force and minimize the torque ripple and suspension force ripple,several leading parameters,including rotor pole width,rotor pole yoke width,stator tooth width and permanent magnet thickness,are optimally designed.After selecting the parameters which can best meet the requirements of the optimization design,the main design parameters of the DW-BFSPM motor are confirmed,which has made preparations for electromagnetic performance analyses of the proposed motor.Thirdly,the 2D finite element model of DW-BFSPM motor is built on the basis of magnetic field analysis software MagNet which is belong to Infolytica.Then,the electromagnetic performances of the proposed motor,including the distribution of magnetic field,PM flux-linkage,no-load back EMF,cogging torque,torque,suspension force,the coupling between torque and suspension force,suspension force regulation and comparisons between 12/10-pole and 12/14-pole DW-BFSPM motors,are analyzed and researched,verifying the superior characteristics of the proposed BFSPM motor.Finally,the control strategy of DW-BFSPM motor is analyzed.By adopting DSP TMS320F2812 as the core,the hardware and software designs of DW-BFSPM motor digital control system are expounded in detail.The designs of hardware circuits which contain main power circuit,signal conditioning circuit and protection circuit and programs which contain main program and interrupt service subroutine are completed.