Research On Regenerative Braking Control Strategy Of Electric Vehicle Driven By Dual Motor In Front And Rear Axles

In the face of the dual pressure of energy and environmental problems,pure electric vehicles(PEVS)with its advantages of zero emission have been highly valued by governments all over the world.Among them,the front and rear axle dual motor drive vehicle configuration with its excellent performance has become the research hotspot of major vehicle enterprises.However,due to the limitations of current battery technology,there is still a gap between the driving range of pure electric vehicles and the driver’s expectations compared with other models.Therefore,it is of great significance to study regenerative braking technology,which can convert braking energy into electric energy and store it and use it when driving,so as to extend the driving range of the vehicle.In this paper,a front and rear axle dual motor drive electric vehicle is taken as the research object,to solve the key issues of the optimal distribution of the front and rear motor braking force during regenerative braking and the coordinated control of motor braking force and hydraulic system braking force.Based on the efficiency data of the motor,inverter and battery,a regenerative braking torque optimization strategy with the goal of maximizing braking energy recovery is proposed;based on the different response characteristics of motor braking system and hydraulic braking system,a compound braking coordination control strategy with variable reserved motor braking force is proposed,which realizes the efficient energy recovery and coordinated control under the condition of safe braking.The specific research contents are as follows:(1)Based on the design goal of vehicle power performance and the statistical data of typical cycle conditions,the parameters of motor,battery and other key components of vehicle power system are matched.(2)The models of motor braking system and hydraulic braking system are established,and the losses of motor,battery and inverter are analyzed combined with specific control strategies.(3)The braking principle of permanent magnet synchronous motor(PMSM)is analyzed.Based on the component parameters of motor braking system,the optimal regenerative braking torque and torque distribution coefficient of front and rear axle motor are optimized,and the influence of parameter changes on the optimal torque is studied.And consider the drag torque of the motor and the constraint of battery on motor braking force,and use the efficiency data of the motor,battery,and inverter to achieve the optimal distribution of motor braking torque.(4)Based on the dynamic response characteristics of motor braking system and hydraulic braking system,the requirements of braking regulations are analyzed,and the steady-state braking force distribution strategy based on the optimal distribution of motor braking torque is proposed.The brake torque of the motor is used to compensate the torque error of the hydraulic brake system due to the hysteresis effect to improve the response of the composite brake system.At the same time,the compensation torque of the motor system changes with the change of braking intensity,to ensure efficient recovery of vehicle braking energy during low-intensity braking and reduce the deviation between the actual total braking torque and the target value under each braking intensity.(5)The system simulation model is established based on MATLAB / Simulink software,and the evaluation indexes of the simulation results are analyzed.The optimal distribution strategy of regenerative braking force of front and rear axles proposed in this paper is verified in WLTC(World Light Vehicle Test Cycle)and other cycle conditions,and compared with typical average distribution strategy.The results show that the strategy can recover braking energy more efficiently;simultaneously,the electro-hydraulic coordinated control strategy of the front and rear axles is simulated under low-intensity and other working conditions.The simulation results show that compared with the uncoordinated control strategies,the strategy proposed in this paper can effectively reduce the error between the actual braking torque and the target value,shorten the braking distance,and improve the braking energy recovery rate under the condition of small intensity braking.