Research On Rule-based Control Strategy For Range-extended Electric Vehicle

New energy vehicle is a significant researching filed of automobile industry.Being a kind of new energy vehicles,range-extended electric vehicle?R-EEV?combines motor,battery and internal combustion engine,owning advantages of long driving distance compared with the electric vehicle,higher efficient,lower pollution and lower noise in comparision with the tradition internal combustion engine vehicles.Matching of power system of REEV equipped with engine and motor is the foundation for REEV researching and developing,and the energy management control is the key for improving fuel economy and power output.The range-extended electric vehicle can obtain better performance through building reasonable power transmission systems,matching accurate dynamic parameters and forming efficient control strategies.The rule-based control strategy was studied because of its high stability and simple control process.First,the power system was built.The power system of the R-EEV is mainly composed of an engine,a generator,a motor,a battery and a drive train.The motor is used as a main power source to drive the vehicle through reducer and a differential,and the engine is an auxiliary power device.There is no direct mechanical connection between the engine and the drive system.Instead,the chemical energy of the fuel is converted into electricity by the generator to provide power for the motor or to charge the battery.After considering the layout of the power equipment in the vehicle,the Rear wheel drive structure was designed.In order to determine the type of power equipment for REEV,the total power demands of vehicle to meet the demand of maximum vehicle speed,climbing gradient and the acceleration performance were contrastively analyzed.The results showed that the traditional calculation of power demand based on the maximum speed and climbing gradient requirements could not meet the requirement of vehicle acceleration performance.Then,a method based on acceleration time to calculate the demand power and the calculation equation were presented.Through the deduction of the equation,it was obvious that the acceleration power demand of the REEV is far bigger than that of the power to meet the maximum speed and the climbing requirement.The basic parameters of the engine,motor,the battery and the transmission system were determined based on the demand power calculation mentioned above,and the matching of the power system of the REEV was completed.Then,the vehicle model and energy management control strategy were conducted based on the co-simulation of AVL Cruise and Matlab/Simulink level.Taking the traditional engine power following control strategy as the core,the control strategy model was built based on Matlab/Simulink and the vehicle model was completed on AVL Cruise software.The working point distributions of the engine and the motor under six cycle conditions of EUDC,FTP75,HIGHWAY,JAPAN₀8,NEDC and WLTC were determined.And it was concluded that the driving distance were 371.057 km,392.825 km,366.505 km,365.051 km,368.163 km and 403.607 km,respectively.In addition the equivalent fuel consumption were 8.423L/100 km,8.638 L/100 km,8.284 L/100 km,8.507 L/100 km,8.483 L/100 km,and 7.662 L/100 km,respectively.The result showed that WLTC owned the longest driving distance and the smallest equivalent fuel consumption.At the same time,the acceleration time from 0 to 100 km/h and the maximum climbing performance at the speed of 40 km/h were calculated.The results show that the REEV model can meet the requirements of dynamic performance.Finally,basing on the traditional engine power following control strategy,an improved research on rules-based energy management control was carried out.An improved thermostat control strategy,the fixed-speed engine power following control strategy,and the fuzzy control strategy were proposed and controller model was established respectively based on Matlab/Simulink level.Meanwhile,theNEDC economic performance using different control models mentioned above was researched.The fuel economy performance of the vehicle was improved to some extent by using the three kinds of different control strategies.The consequence showed that the fuel consumptions of the R-EEV adopting improved thermostat control strategy,fixedspeed engine power following control strategy and fuzzy control strategy were 8.319L/100 km,8.267 L/100 km and 7.784 L/100 km,respectively,and the driving distances were 369.993 km,389.112 km and 405.129 km,increasing by 0.50%,5.69%,and 10.04% compared with the traditional engine power following control strategy.At the same time,using the fuzzy control strategy,the phenomenon of large-current charge and discharge of the battery was obviously decreased,which was of great significance for prolonging the service life of battery.