Research On Dynamic Characteristics And Corresponding Control Strategies Of In-Wheel Motor Driving System

In recent years,the problems of energy shortage and ecological environment deterioration have become increasingly prominent.Electric vehicles(EVs)with zero emissions have become the main development direction of the automotive industry.IWM-EVs(in-wheel motor electric vehicles),which eliminates mechanical transmission system and integrates fast and accurate multidimensional dynamic control,has brought significant attention.However,vibration and noise problems hinder its applications.The mechanical interactions couple highly with the electromagnetic excitation generated by driven motor.As a result,the transient fluctuation of output energy from power source directly transfers to the wheel,which results in the new dynamic issues and deteriorates vehicle dynamic performance.Considering the characteristics of electromagnetic output of the energy conversion device-drive motor in IWM drive system,this paper investigates(1)the effect of fluctuation of output electromagnetic force on the longitudinal driving performance of vehicle,and(2)the electromechanical coupling effect of unbalanced electromagnetic excitation on the vertical vibration of vehicle.In addition,this study explores the optimal design for the torque ripple of drive motor,the coupling mechanism of the machine-electric multi-field system and its negative effects on vehicle system,and then seeks for corresponding control methods.The details include the following aspects:(1)After type selection and dynamic matching for the power source in IWM,the parameters of the motor were optimized by using fuzzy mathematics theory.With the improvement in torque-power density,the unsprung mass of vehicle has been effective reduced.(2)Focusing on the longitudinal form stability of an electric vehicle equipped with an IWM system,the causes of the two kinds of torque ripple are analyzed.The corresponding phase current balance strategy and the improved stator and rotor pole tip solutions are proposed.The optimal stator and rotor pole tip were determined by a finite element parameter scanning.(3)The analytical calculation models which is characterized the output electromagnetic force of the IWM driving system and the vehicle dynamics model which is characterized the motion of the four-wheel independently driven electric vehicle were developed and conjoined.The acquired electromechanical coupling analysis model is adopted to study the electromechanical coupling mechanism between the electromagnetic excitation generated by the driving motor and the motion of the vehicle dynamic system by using the transfer function and vibration energy distribution.The key influence factors and control parameters of electromechanical coupling effect are clarified and studied.(4)Two control strategies based on in-wheel driving motor controller and active suspension system respectively were introduced and studied to solve the vehicle vibration problem caused by the negative electromechanical coupling effects.