Research On The Negative Effect Of Vertical Vibration In The In-wheel Motor Driven Electric Vehicle Based On Electromagnetic Suspension

Electric vehicles are being widely studied by scholars all around the world because of environmental and energy pressures.The driving form of electric vehicles is divided into centralized driving and distributed driving including in-wheel motor driving and wheel-side motor driving.Compared with centralized motor driving,in-wheel motor driving eliminates reduction gearbox and other transmission devices to make it easier to realize complex kinematics and dynamics control,and improve the transmission efficiency and space utilization.However,electric vehicles unsprung mass is increased due to the installation of the in-wheel motor,which may deteriorate the tire grounding and ride comfort.On account of this,this paper takes the in-wheel motor driven vehicle as the research object,through optimizing the in-wheel motor arrangement form and adopting the electromagnetic suspension structure,comprehensively solving the negative effect of vertical vibration in the in-wheel motor driven vehicle caused by the unsprung mass increase.The main research contents are as follows:Firstly,the dynamic effects of the in-wheel motor on vehicles are analyzed and two types of in-wheel motor arrangements are proposed to suppress the negative effects of the vertical vibration.Through the modeling and simulation to compare between the two layout forms,the structure adopts the suspended type on accounts of the performance in tire grounding.The wheel motor is equivalent to a dynamic vibration absorber,vibration can effectively share the wheels in the high frequency resonance region,which can effectively share the road vertical excitation on the tire especially in the high frequency resonance region.Secondly,a coordinated control method of active control and semi-active control is designed based on electromagnetic suspension,targeting at improving ride comfort and reducing energy consumption.In the semi-active control mode,the system can provide a range of ceiling control power to improve the ride comfort without consuming energy.In the active control mode,the linear motor outputs the active force to suppresses the vertical vibration of the vehicle body by working as a motor.The force ranges widely,but it needs to consume energy.Thirdly,a dynamic model of the electromagnetic suspension with suspended in-wheel motor is built.The transmission characteristics and the amplitude characteristics related vehicle body acceleration and the tire dynamic load are analyzed.The results show that the hybrid electromagnetic suspension with the suspended in-wheel motor significantly improves its vertical dynamic performance including ride comfort and tire grounding.In addition,the key parameters of the suspension system and the stiffness-damping coefficient of the elastic component in the suspended in-wheel motor are optimized.The dynamic performance of vehicle body and wheel is improved after optimization.Finally,1/4 electromagnetic suspension is experimented based on the dSPACE rapid control prototype on random and sinusoidal road to test the dynamic performance of the electromagnetic suspension system.The experiment results show that the electromagnetic suspension can improve the ride comfort,which is consistent with the simulation to verify the feasibility of the skyhook control strategy.The research shows that electromagnetic suspension with suspended in-wheel motor makes the motor be equivalent to a dynamic vibration absorber to share the body vertical excitation from the road.The tire dynamic load reduces by 13.0% when compared to traditional suspension to suppress the vertical vibration of the wheel and to improve the tire grounding.In terms of control,coordinated control mode including semi-active control and active control based on skyhook control strategy decrease the body acceleration by 24.7% when compared with traditional suspension,the tire dynamic load decreased by 13.0%.Vehicle ride comfort is improved while energy consumption is reduced.