| Compared with hybrid electric vehicles,pure electric vehicles employ electric motors as power devices and accumulator as energy storage devices,with the advantages of simple structure,low noise and zero emission.Pure electric vehicles have attracted wide concern and high attention all over the world by right of their broad industrialization prospects.It has become the major research direction to resolve the problem of how to improve the driving range and comprehensive performance of pure electric vehicles.However,besides battery technology,the improvement of driving range is also affected by many factors,including power assembly and its control technology,efficient transmission system and full-featured energy management control strategy.This thesis proposes a new dual drive powertrain for pure electric vehicles,which has two power sources that can switch among several working modes in accordance with different working conditions,and thus significantly improve the driving range of pure electric vehicles and greatly expand the efficiency range driven by synthetic power sources.In addition,the system has the function of ECVT(Electric Continuous Variable Transmission),which enlarges the speed ratio range of the transmission system to effectively improve the driving range of pure electric vehicles.Meanwhile,under the premise of driving safety,the braking energy recovery of the vehicle becomes more efficient and the driving range is further improved.The details of this study are listed as follows.(1)This paper aims to analyze the working characteristics of the dual drive powertrain of pure electric vehicles mentioned above,describe its various working modes,and provide a basis for the subsequent matching design and control method research through the system dynamics model constructed by lever principle.Furthermore,based on the analysis of energy consumption of electric vehicles and the working characteristics of driving motors,the energy-saving potential and mechanism of the new dual-drive transmission system configuration of pure electric vehicles are discussed.(2)The relationship between vehicle performance and the power of driving motor system is explored,and the relationship model between peak power and maximum speed,acceleration and climbing capability is constructed.In addition,this study will obtain the load power probability by analyzing the demand power distribution under various cyclic conditions,which is utilized as the basis of preliminary matching design.Based on the above work,the preliminary matching of power transmission system parameters is carried out,and the rationality of the preliminary matching parameters is verified by the built simulation platform.In order to improve the performance of the vehicle,a multi-objective optimization function including dynamic and economic indexes is created,and the genetic algorithm is used to optimize the power transmission system parameters.(3)This study comprehensively considers the efficiency of each component of the power transmission system and the influence of the efficiency on the overall vehicle efficiency under various working modes.A real-time optimal control strategy which is based on the logic threshold is formulated to improve the diving range under the premise of guaranteeing the vehicle's dynamic performance.Besides,considering the effect of driving intention on the vehicle performance,the driving intention is classified scientifically,and the real-time optimal control strategy based on driving intention is formulated,and then the simulation comparison analysis is carried out.(4)Based on the analysis of the dynamic characteristics of the key components,the dynamic simulation model of the motor,the actuator model of the hydraulic system and the dynamic model of the wet clutch/brake are constructed to lay the foundation for the study of the dynamic process of mode switching.Combining the working characteristics of each component of the dual drive powertrain and the characteristics of each working mode,a scientific and reasonable mode switching control flow is formulated.In addition,a torque coordinated control method of motor,clutch and brake is proposed for the process of speed regulation.Moreover,the MATLAB/Simulink platform is employed so as to complete the simulation analysis of the mode switching process among the various working modes.(5)Then the basic data test is completed to provide a basis for the follow-up research.Furthermore,the prototype and test bench of the dual-drive transmission system of pure electric vehicles are developed and designed.The control program and test bench software of the dual-drive transmission system are developed through the MATLAB/Simulink and dSPACE platform.What's more,the bench test system of dual-drive transmission system of pure electric vehicles is developed on the basis of dSPACE,which is then utilized to complete the functional test of the dual-drive transmission system of pure electric vehicles. |
PDF Full Text Request