Research On Matching Of Powertrain Parameters And EMT Shift Strategy For Pure Electric City Bus

As a public transportation vehicle,pure electric city bus has advantages of high efficiency,energy saving and environmental protection.It is an efficient way to alleviate the current situation of energy shortage,urban road congestion and air pollution.Powertrain is the power source of pure electric bus,so the rationality of its parameters matching has a decisive influence on vehicle performance.At the same time,via using reasonable shift control to regulate the working condition of drive system and to make the best use of motor's working characteristics,the vehicle performance can be improved effectively.It is of great theoretical significance in improving the level of pure electric vehicle technology.In this thesis,based on the analysis of the movement mechanics of pure electric city bus,the vehicle performance requirements and their evaluation methods are analyzed and the influence factors of vehicle performance are studied.The matching principle of powertrain,which meets the vehicle dynamic performance as the premise and also considers the vehicle economy performance,is established.And the requirement of the maximum transient power demand of the vehicle under the cycle condition is one of the matching factors of the motor parameters so as to ensure the output power of the power system,which can guarantee the needs of the vehicle's actual operation.The simulation model of the pure electric city bus is established and the simulation is carried out by using the AVL-Cruise software simulation platform to calculate the vehicle performance.The simulation results show that the parameters of the designed powertrain can meet the requirements of vehicle dynamic performance,and the motor can maintain high efficiency while the vehicle is under the cycle condition.Through a vehicle road test,the results show that the simulation model has high reliability and accuracy,which provides a basis for further study of shift strategy.Based on the validated vehicle performance simulation model,the three-parameter optimal dynamic performance and optimal economic performance shift schedule for targeted vehicle is established.The results show that comparing with the single parameter shift schedule of original vehicle,the new dynamic shift schedule can effectively improve the acceleration performance of the vehicle and reduce the acceleration time required,and the new economic shift schedule can improve the working area of the motor under the cycle condition and improve its overall working efficiency.Furthermore,both two kinds of three-parameter shift schedules can eliminate efficiently the cycle shift phenomenon while vehicle is accelerating on slope.In this thesis,the research methods are based on theoretical analysis,simulation as auxiliary,and the real vehicle test are carried out to verify the method.The power system parameters matching method and the shift schedule of automatic transmission system are studied,and great results have been achieved.This research provides a reasonable reference for the development of power system and performance optimization of pure electric bus and has good practical value in engineering.