Research On The Halbach-Magnetized Tubular Linear Machine For Hybrid Electric Vehicles

In recent years,with the increasing demand for energy saving and environmental protection in the automobile field,new energy vehicles ha s been paid more attention to.Due to the insufficient energy density of battery,the use of battery electric vehicle has been limited.So scholars have focused on the research of hybrid electric vehicles.Under the application background of hybrid electric vehicle,the combination of linear motor and free-piston internal combustion engine can form a linear power generation system.The system does not need any intermediate transmission mechanism,so the system efficiency and integration have been effectively improved.In this paper,the electromagnetic design,permanent-magnet(PM)structure,mechanical structure and optimization algorithm of linear motor are studied.And the major work can be summarized as follows:Firstly,the electromagnetic scheme of the linear motor is designed ba sed on the free-piston linear power generation system.According to the requirements of the application background,a 15-slot 13-pole cylindrical linear motor was selected.The winding form is a single-layer fractional slot concentrated winding structure,and the PM structure is a Halbach permanent-magnet structure.The influence of PM thickness,radial magnetizing proportion,outside diameter of mover and pole slot fit on efficiency and power density is studied,and the influence of end tooth structure on thrust fluctuation is explored.Then,the influence of variable speed motion on motor performance is studied.On this basis,the matching of current and speed is studied.To solve the problem of magnetic field on the non-air gap side of Halbach PM structure,the special-shaped PM structure and the back-iron are adopted.Secondly,the magnetizing structure of cylindrical linear motor is studied.The influence of radial PM structure,axial magnetization PM structure and Halbach PM structure on the performance of the motor is analyzed under the premise that the mass of the motor is strictly limited.Then,in view of the defects of unreasonable utilization rate of mover core and excessive magnetic leakage,the special-shaped permanent magnet design is adopted.Thirdly,the optimization algorithm of cylindrical linear motor is studied.To solve the problem that the finite element analysis(FEA)takes a long time to optimize the motor,the response surface method is used to generate the proxy model to approximate the FEA.Various response surface models are studied and the most suitable response surface model is selected according to the fitting precision.Then,particle swarm optimization is used to optimize the parameters of the fitted response surface model,and the final results are verified by finite element analysis.The results show that the algorithm is effective.Finally,the mechanical structure of cylindrical linear motor is studied.The deflagration of internal combustion engine will generate a huge axial thrust,which is acted directly on the linear motor through the free-piston..On this basis,the stress analysis of the linear motor is carried out and the most suitable structure is selected.Then the linear displacement sensor is studied and the assembly of the displacement sensor under the condition of insufficient space at the end of the linear motor is explored.