Research On Regenerative Braking Control Strategy Of Pure Electric City Bus Based On Fuzzy Control

In recent years,pure electric bus has gradually become the dominant transport tool in urban.However,the bus needs to accelerate and brake frequently in the urban working condition.Because of its heavy weight,most of the kinetic energy in the process of mechanical braking is directly converted into heat energy dissipation,and the energy is not fully utilized.In view of this problem,based on the fuzzy control theory,the research on regenerative braking control strategy of pure electric city bus is carried out.The main research work includes:(1)According to the composition of the pure electric vehicle subsystem,the working logic of each subsystem in the braking mode of the bus in this study is determined;according to the performance objectives of the bus,the main components of the bus power system are matched and selected,and then the front and rear axle braking force distribution range under the condition of maintaining the braking stability of the bus is studied.(2)The regenerative braking control strategy based on fuzzy control is divided into front and rear axle braking torque distribution strategy and regenerative braking torque distribution strategy.According to the stable braking conditions of the bus,the improved front and rear axle braking torque distribution strategy is designed.In order to improve the control accuracy,considering the brake strength,vehicle speed and SOC of battery state,the intervention proportion of motor is divided into seven levels based on the fuzzy control theory;the regenerative brake torque distribution strategy of bus is designed,and the corresponding control strategy model is built in Matlab/Simulink platform.(3)Using cruise software to build the simulation model of the bus and input the real car parameters,using cruise software and Simulink to carry out joint simulation,mainly in different braking conditions,carry out simulation analysis on the distribution of braking force of each axle of the bus under different braking conditions.The power performance of the bus and the economy of the bus under the typical urban public transport cycle in China are simulated.Based on CAN-bus,the topological structure of bus electromechanical composite braking system node connection is established in CANoe software,and each node is simulated based on SAE J1939 protocol.The results show that the braking torque can be distributed according to the design control strategy,and the braking distance can be kept within 45m under the initial speed of 60km/h,Which can meet the requirements of national standards for braking distance.Compared with the default regenerative braking control strategy of cruise,the regenerative braking control strategy of this study can significantly improve the recovery ability of braking energy,and has good speed following performance.The driving range has reached 153.8km,and the energy consumption rate has been reduced by 10.7%to 808.9W/h/km.In CANoe software,the topological structure of bus electromechanical composite braking system node connection is established.Based on SAE J1939 protocol,each node is simulated to send and receive messages.The results show that the bus load rate of this structure is low,the stability is good and it can be expanded.(4)According to the relevant national test standards,the real vehicle test of the power performance,economic performance and braking performance of the city bus is completed.The test results show that the acceleration time of 0-30km/h is 7.5s,the acceleration time of 30-50km/h is 7.3s,the maximum speed reaches 68.5km/h,the constant driving mileage reaches 186km,and the braking time at the initial speed of 60km/h is 2.48s.The dynamic performance,economic performance and braking performance of the car are The performance indexes are in good agreement with the simulation results,Which proves the high reliability of the model,that is to say,the effectiveness of the regenerative braking control strategy developed in this study is effective.In this research,the regenerative braking control strategy of pure electric city bus is studied and developed.The application of the control strategy in this study has good braking performance,meets the braking demand of city working condition,and makes the secondary utilization of energy more fully,Which provides an effective method for improving the economic performance of city bus.