| Under the background of national support for the development of new energy vehicles,the market share of pure electric vehicles is getting higher and higher.How to improve the driving range is one of the key technologies restricting the popularization of pure electric vehicles,and consumers have put forward higher and higher requirements for the driving range.As the core assembly of pure electric vehicle,electric drive system has a direct impact on many performances of the whole vehicle.In recent years,through matching multi gear transmission to improve the operation efficiency of electric drive system,it has attracted the attention of automobile manufacturers at home and abroad.However,limited by key technologies such as system integration and reliability,it has not been widely used in pure electric vehicle.According to the optimization of electric vehicle electric drive system parameters and the optimal shift schedule design,based on the theory of automobile system dynamics;the theory and method of dynamic programming and Kalman filter are applied.This paper mainly carries out the parameter matching of pure electric vehicle electric drive system and Research on shift control strategy,the main research contents are as follows.(1)The background and significance of the research are elaborated.Whether multi-gear transmission is needed in the electric drive system of pure electric vehicle and the configuration of the transmission used in pure electric vehicle are analyzed.The key technical problems in the application of AMT system in pure electric vehicle are investigated,and then the main research contents of this paper are introduced.(2)Based on the design of the power and economic design of pure electric vehicles,combined with the analysis of the key components of the powertrain system,the parameters of the main components of the powertrain are matched.After analyzing the speed/torque characteristics of the drive motor,the motor power parameters and speed parameters are matched according to the design parameters of the vehicle’s maximum speed,maximum grade,acceleration time,etc.;the transmission gear number and speed ratio parameters are analyzed for the vehicle’s power and The economic impact,the establishment of the transmission system speed ratio constraints,the use of dynamic programming algorithm to optimize the transmission system speed ratio parameters,determine the use of two-speed AMT transmission scheme.(3)Using the joint simulation method of Amesim and Matlab,the vehicle longitudinal motion model is built,including battery model,drive motor model,AMT model,vehicle model,vehicle controller VCU and shift strategy.model.(4)The economics and dynamics are used as indicators to determine the optimal dynamics and the best economic shift rules.According to the relevant theoretical knowledge of genetic algorithm,a multi-objective comprehensive performance evaluation function based on dynamics and economy is established,and the comprehensive shifting rules of pure electric vehicles based on genetic algorithm optimization are established.The three shift rules designed in this paper are verified by simulation,and their economy and dynamics are compared.The results show that the comprehensive shifting rules based on genetic algorithm optimization ensure the dynamics while taking into account the economy.(5)Using the extended Kalman filter algorithm to design the vehicle quality and road gradient identification algorithm,the algorithm can effectively estimate the vehicle quality and road gradient,and can meet the requirements of the vehicle automatic transmission control system.Based on this,the shifting strategy of different loads and different road ramp conditions is carried out.The simulation results show that the ramp shifting strategy designed in this paper can downshift when going uphill,effectively avoid frequent shifting and reduce the shift.Wear of the blocking parts;timely downshift when downhill,fully utilize the braking torque characteristics of the driving motor,improve the braking energy recovery efficiency and reduce the wear of the braking system.(6)In order to verify the shift control strategy proposed in this paper,the software architecture design and hardware circuit design of the two shift AMT control system are completed.Based on the self-developed controller,the model-based control software development process is adopted to complete the vehicle road test.Through the acceleration test of 0-100km/h,the shift test of different load and different road slope conditions,the effectiveness and practicability of the shift strategy designed in this paper are verified. |
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