Research Of Electronic Differential System For Distributed Drive Electric Vehicles

The distributed drive electric vehicle eliminates the complex system of the traditional car and simplifies the chassis structure,and it not only reduces the quality of the vehicle,but also leaves more passenger space,it is easier to achieve modular,electrified and active control of the vehicle chassis while improving transmission efficiency,and achieving a better driving experience.Therefore,distributed drive electric vehicles are highly concerned by major enterprises and universities.Nevertheless,the problems of distributed electric vehicle drive control technology can not be ignored.Distributed drive electric vehicles have the problem of coordinated control between drive wheels when they have more controllable degrees of freedom.Especially,when the vehicles are turning,due to the different lengths of the inner and outer wheel motion trajectories,there is a contradiction between the speed demand and the torque control,so-called differential problem.In order to solve the differential problem of distributed electric vehicles,this paper takes the distributed electric vehicle as the research object,which driven by the rear wheel,and an adaptive electronic differential control strategy based on slip correction is proposed.Firstly,based on the theory of vehicle dynamics,this paper establishes and analyzes a quarter model of vehicle,Ackermann steering geometry model and multi-degree of freedom steering force model,and clarifies the mechanical relationship between single drive wheel and ground,the geometric relationship in the steering and the force in the steering of the vehicle.Secondly,referring to the principle that the traditional differential realizes the speed difference with the road surface adhesion,the model adaptive differential control of the vertical load ratio distribution of the vehicle model is proposed based on the principle that the adhesion coefficients of the driving wheels on both sides are the same.At the same time,the rotational speed constraints of the driving wheels on both sides are established based on the Ackermann steering geometry,and the limit slip control strategy of correcting slip is proposed by using the references which estimating vehicle speed difference on both sides.Therefore,the limited slip differential control of vehicles achieved by the combination of the above two.Furthermore,in order to verify the control strategy proposed in this paper,the vehicle model established by using the CarSim,and the joint simulation is carried out by using the control strategy model constructed by Matlab/Simulink.The simulation results show that compared with the traditional mechanical differential,the differential scheme proposed in this paper has advantages in wheel limit slip while achieving electronic differential.Finally,this paper designed and developed an electronic differential controller,and built a distributed electric vehicle test vehicle driven by the rear wheel hub motor,and carried out a vehicle test.The experimental results show that the adaptive electronic differential control strategy based on slip correction designed in this paper can realize the differential effect through torque coordinated control.