Research On Electromechanical Coupling Vibration And Vehicle-road Interaction Dynamics Of Independently Driven Electric Vehicle

Due to motors in the wheels of electric vehicles,the increase in the unsprung mass and the unbalanced force generated from eccentricity may cause the suspension to vibrate.At the same time,the vehicle and the road are coupled with each other through dynamic tire forces,and the vehicle-road coupling effect will also change vibration of the vehicle status.Therefore,it is of great significance to establish a model of mutual coupling system among cars,motors,and roads to study vehicle ride comfort.This dissertation firstly derives the expressions of the air gap magnetic field and electromagnetic force wave when the in-wheel motor has no eccentricity,static eccentricity,and dynamic eccentricity using the magnetic potential multiplying permeance method The spatial order and frequency characteristics of the air gap magnetic field and electromagnetic force wave are analyzed.Then the permanent magnet synchronous motor was modeled and verified by the finite element software.Secondly,the modal superposition method is used to obtain the road displacement response caused by the vehicle load as the road secondary excitation.And the electric vehicle-road coupled nonlinear dynamic model is established based on the quarter and half-vehicle models,respectively.The influence of parameters such as motor mass,motor electromagnetic excitation,and road secondary excitation on vehicle vibration and road friendliness is analyzed.Finally,based on the fuzzy PID algorithm,the control strategy of the electric vehicle active suspension is designed,and the influence of the secondary excitation of the road surface and the different eccentric electromagnetic force on the control effect is analyzed.The research results show that:(1)When the hub motor has a static eccentricity,the electromagnetic force balance position will shift so that the main frequency will be an even multiple of the current fundamental frequency.When dynamic eccentricity occurs,the electromagnetic force amplitude increases about±f_e near the fundamental frequency.(2)The flatter the road,the more significant the impact of motor quality,vehicle nonlinearity,electromagnetic excitation and road secondary excitation on vehicle body vibration and road damage.Among them,the secondary excitation of the road surface has the greatest impact on the acceleration of the vehicle body,and the nonlinearity of the vehicle has the greatest impact on the dynamic deflection of the suspension.The dynamic tire load and the fourth power resultant force are led by the static eccentric electromagnetic force.(3)Vehicle nonlinearity and road secondary excitation mainly increase the dynamic load of the rear wheels,and the degree of increase of vehicle nonlinearity is about three times that of the road secondary excitation.The static eccentric electromagnetic force has the greatest impact on the dynamic load of the front wheels,which can increase by25.74%.The impact of the secondary excitation of the road on the ride comfort is mainly reflected in the pitching motion of the body.(4)After adopting fuzzy PID strategy,the acceleration of the vehicle body is reduced by 26.28%,and the maximum deflection of the road surface is reduced by 4.6%,which effectively improves the ride comfort and road friendliness of the vehicle.The secondary excitation of the road surface and the dynamic eccentric electromagnetic force will reduce the control effect of fuzzy PID.The static eccentric electromagnetic force will improve the control of vehicle ride comfort,but will reduce the control effect of road friendliness.