Research On Thrust Characteristics Of Permanent Magnet Linear Vernier Machine With Double Stator

Linear machine can convert electric energy into linear mechanical energy without intermediate transmission device.It has a good application prospect in direct drive applications such as ropeless elevator,transportation and so on.Aiming at the problem of low thrust density and large thrust ripple of conventional permanent magnet linear machine,the permanent magnet linear vernier machine(PMLVM)is studied in this paper.With the goal of improving thrust density and reducing thrust ripple,the novel machine topology and analysis method are studied.The specific research contents are as follows:1)Take PMLVM as an example to reveal the feasibility of flux modulation theory in linear machine.From the topological evolution of linear vernier machine(LVM)to theoretical analysis,the magnetomotive force(MMF)-permeability method and finite element method(FEM)are used to analyze the air gap magnetic field characteristics from the perspective of harmonics,and deduce the general expressions of back electromotive force(EMF)and thrust of PMLVM.The surface-mounted PMLVM experimental testing platform was established to verify with theoretical analysis and FEM results.2)Based on the flux modulation theory of linear machine,a novel structure of double-stator and dual-PM toroidal-winding LVM is proposed with high thrust density and low thrust ripple.Firstly,the topological structure of the machine is analyzed,and the design elements such as double stator,dual-PM and toroidal-winding are combined together,which has a bidirectional flux modulation effect.Secondly,three kinds of conventional LVMs with different topologies are compared with the novel machine,and their working principles are verified from the perspective of harmonics.Thirdly,taking average thrust value,thrust ripple and PM utilization rate as optimization objectives,the key parameters of the machine were optimized and designed,and the magnetic field,inductance,back potential and thrust and other electromagnetic characteristics of the four kinds of machines were analyzed and compared.The average thrust of the optimized novel machine reaches 321.23N,the thrust ripplr is only 2.68%,and the thrust density is 304.19kN/m~3,which is 38%,51.7%and 164%higher than the other three conventional machines,respectively.Finally,the two experimental platforms were used to verify that the performance of dual-PM LVM was significantly improved compared with one-side PM LVM.3)The thrust ripple mechanism of double-stator PMLVM was studied,and an end-assisted iron block topology was proposed to suppress the detent force.The analytical model of detent force of double-stator PMLVM is deduced by Fourier series method,and the method of adding end-assisted iron block is proposed to weaken the end force of the machine.The FEM results show that the detent force is reduced by 77.3%,and the thrust ripple of the machuine is suppressed well.By means of topological analysis,theoretical research,electromagnetic calculation,experimental verification and other methods,this paper verified the easibility of flux modulation theory in the topology of novel linear machine.The high thrust density and low thrust ripple characteristics of linear machine can be shown,so its suitable for direct drive elevator,mine hoist system,precision machining and other applications.