Research On Regenerative Braking Control Strategy For Pure Electric Vehicle With Two-Speed AMT Based On Driver’s Braking Intention And Road Condition

Faced with the increasingly urgent global issues such as energy and environment,developing new energy vehicles represented by pure electric vehicles has become an important means to solve them.Compared with conventional fuel vehicles,pure electric vehicles can improve energy efficiency through regenerative braking energy recovery,thus significantly improving energy consumption economy.Therefore,it is of great academic significance and application value to study the regenerative braking control strategy for pure electric vehicle.In this thesis,a domestic pure electric vehicle with two-speed AMT is taken as the research object,the main scientific problems of pure electric vehicle regenerative braking are studied and the regenerative braking control strategy for pure electric vehicle with two-speed AMT based on driver’s braking intention and road condition is formulated.Specific research contents include:(1)Aimed to existing these two braking modes include the conventional regenerative braking and the sliding regenerative braking when the pure electric vehicle needs to brake,the BP neural network algorithm is first used to establish a neural network prediction model to predict the shortest braking distance that can be achieved under different gradients when adopting sliding regenerative braking.Then,according to the braking distance defined by the road conditions and braking requirements and the predicted value of the shortest sliding braking distance,the braking mode is selected from these two braking modes.Under the premise of satisfying the road conditions and braking requirements,the priority is to select the sliding regenerative braking which has high energy recovery rate and low operation requirement for drivers,and select the conventional regenerative braking when the sliding regenerative braking cannot meet the road conditions and braking requirements.(2)Aimed to the driver’s braking intention identification under conventional braking conditions,the expected braking intensity expressed by the driver’s braking intention identification coefficient based on the brake pedal operation is firstly obtained by the fuzzy identification method,and the driver’s braking intention is further amended according to different road conditions to ensure brake safety.Then the braking force distribution strategy under conventional braking conditions is formulated.The method of piecewise control is taken to control the braking force distribution of the front and rear axle,achieving the braking force distribution target that guarantees high energy recovery and braking stability simultaneously based on the low braking system control requirements.(3)Aimed to the driver’s braking intention identification under sliding braking conditions,the driver’s braking intention identification coefficient based on the accelerator pedal operation is firstly obtained by the fuzzy identification method,and the driver’s braking intention is further amended according to different road conditions to ensure brake safety.Then the regenerative braking force control strategy based on the driver’s braking intention under sliding braking conditions is formulated,and the purpose of adjusting the regenerative braking torque and the torque variation rate of the motor according to the driver’s braking intention is achieved.Thus the braking force that meets the driver’s braking needs is obtained,the degree of jerk of the vehicle is controlled when braking.(4)The efficiency characteristics of major components(battery,motor,transmission)affecting the effective regenerative braking power in the transmission system of pure electric vehicles with two-speed AMT are analyzed.And then the regenerative braking energy recovery optimization control strategy is formulated to optimize the regenerative braking torque of motor and transmission ratio at the same time with the intention of maximizing the effective regenerative braking power,further improving the regenerative braking energy recovery rate.(5)Aimed to pure electric vehicles with two-speed AMT,a forward simulation model is established to perform simulations for the regenerative braking control strategy proposed in this thesis under different road conditions and typical urban cycle condition.The simulation results show that the proposed regenerative braking control strategy can improve the controllability,security and comfort in the braking process of pure electric vehicles,as well as the braking energy recovery rate.