Research On Motor Torque Distribution Strategy Of Four-wheel Independent Drive Electric Vehicl

As an important form of distributed electric vehicle,four-wheel independent drive electric vehicle has its unique advantages,such as simple structure and high efficiency.It will have a good development prospect in the future.For this special form of electric vehicle,targeted electronic stability control program that can give full play to the advantages of the platform is also essential.Based on the control mode of direct yaw moment control(DYC),a motor torque distribution strategy considering the influence of road adhesion coefficient and the difference of contribution of each wheel pair to yaw moment is proposed for four-wheel independent drive electric vehicle.This strategy fully considers the different contribution of each tire to the generation of yaw moment,The adaptive control of vehicle stability is realized under different road adhesion conditions.Firstly,in order to meet the needs of research and balance the relationship between key research contents and model complexity,tire model and seven degree of freedom dynamic model are established in this paper.Secondly,based on the characteristics of four-wheel independent drive electric vehicle,some important state parameters are observed.The tire force in each coordinate direction of the tire is estimated in the form of dynamic equation.An observation method based on Unscented Kalman filter is established to estimate the sideslip angle of centroid.At the same time,for the observation of road adhesion coefficient with low accuracy,there is no need to specially construct other algorithms.Combined with the tire model and unscented Kalman filter algorithm in the previous paragraph,the corresponding road adhesion coefficient of each tire that meets the requirements of this paper can be obtained.Considering the safest principle,the coefficient corresponding to the smallest of the four tires can be used as the reference of the whole control algorithm.Then,based on the hierarchical control structure of the control allocation problem,this paper designs the upper yaw motion control and the lower motor torque allocation strategy.The yaw motion control is based on the approach law sliding mode control method,taking the yaw rate and centroid sideslip angle as the control variables,and considering the influence of vertical load on the sideslip stiffness,the expected yaw moment required by the whole vehicle is calculated;In this paper,the contribution difference of each tire to the yaw moment is fully considered,and the stable maximum speed under different road adhesion coefficient is tested.A motor torque distribution strategy considering the influence of road adhesion coefficient and the contribution difference of yaw moment of each wheel set is proposed.At the same time,in order to reduce the amount of calculation in the real object,the particle swarm optimization algorithm is used to improve the motor torque distribution strategy.Finally,hardware in the loop experiment is carried out to verify the feasibility of the proposed motor torque distribution strategy.