Research On Structure Optimization And Drive System Control Of In-wheel Switched Reluctance Motor

With the increasing shortage of energy and environmental pollution,new energy vehicles have received widespread attention.Many new energy vehicles using electric drive,in-wheel motor is one of its core components.In-wheel motor technology,also known as wheel motor technology,it integrates power,transmission and braking into the wheel,thus greatly simplifying the mechanical part of the electric vehicle and enabling a variety of complex drive modes.Switched reluctance motor(SRM)is regarded as the first choice for in-wheel motors of electric vehicles,because of its reliable and simple structure,low cost,high efficiency and wide range of speed regulation.However,the development of SRM in electric vehicles is limited by its inherent double salient pole structure,highly nonlinear magnetic circuit and drive control mode.It is of great significance to study the output performance of switched reluctance motor for improving the performance of electric vehiclesIn the actual operation,the air gap eccentricity caused by road excitation and internal load will produce unbalanced radial force in the radial direction,which produce impact on the vibration and noise of the SRM.At the same time,the effect of unbalanced radial force direct influence the vehicle ride comfort.In this paper,the several main structure parameters of SRM multi-objective optimization by constructing the response surface model,to find inhibition caused by unbalanced radial force of the new method of in-wheel motor output performance from the source.Constructed the integrated model of electric vehicle driven by switched reluctance in-wheel motor,wheel and vehicle body system.And different motor drive control strategies are adopted to reduce the magnitude of unbalanced radial force,so as to improve the ride comfort of electric vehicle.The main research contents are as follows:(1)The 8/6 pole four phase switched reluctance motor finite element simulation model are set up in the Ansoft Maxwell,the static characteristic and dynamic characteristic are analyzed in the simulation,obtain under different current and rotor position angle of the torque,current,flux and inductance characteristic.(2)In-wheel motor output characteristic should satisfy electric vehicle dynamic performance and comfort of vehicle performance requirements,such as the unbalanced radial force for switched reluctance motor,leads to the deterioration of the output performance.The five indicators of output performance is presented,with an average torque motor,coefficient of torque ripple,unbalanced radial force,torque density and efficiency as the optimization goal,the basic structure of in-wheel motor parameters sensitivity analysis,the combination of finite element and design of experiments method,set up the 3th-order response surface model of switched reluctance motor structure parameters for multi-objective optimization,optimization results show that the average torque,torque ripple coefficient,unbalance radial force,torque density and motor efficiency are all improved.(3)Based on switch reluctance motor finite element simulation analysis,the motor mechanical and electrical contact equation,electromagnetic equation,mechanical drive equation and circuit equation are derived,establish a nonlinear mathematical model of switched reluctance motor.And then the in-wheel motor driver model and vehicle vibration model of the switched reluctance wheel motor drive electric vehicle integration model are derived.It is shown that the unbalanced radial force of the motor has negative effect on the vertical excitation of the vehicle,which lays a good foundation for the subsequent research on the motor drive control.(4)The basic principles of Current Chopper control,Voltage Chopper control and Pulse Width Modulation control of SRM are analyzed theoretically.The current response,torque characteristics and unbalanced radial force response of the vehicle were analyzed when the vehicle adopted current chopper control at low speed and at high speed.Advances a PWM control method based on the current chopping,contrast current chopping control and PWM control strategy based on current chopping under unbalanced radial force,The results show that the unbalanced radial force effectively reduced by the PWM control strategy based on CCC,at the same time,the rms value of sprung mass acceleration,suspension dynamic displacement and the tire dynamic load also reduced,it improve that the control strategy improve the ride comfort of the vehicle.