| Parallel Hybrid Electric Vehicle(PHEV)connects the engine and the motor to the drive system through a mechanical connection.The engine and the motor mentioned above can be driven separately or together to drive the vehicle,according to the needs of driving conditions.In this paper,a certain type of PHEV is chosen as the research subject.Based on the selected working conditions,the matching and optimization of the parameters of the powertrain and transmission system and the establishment of its control strategy have been analysed and studied in this paper.This paper first classified hybrid vehicles from the perspective of general component types and connection methods respectively.And then analyzed the structure and energy transmission of the three types of hybrid vehicles in detail.After that,the structure and energy transmission of the powertrain of the PHEV selected in this paper was analysed and the specific operating conditions of the PHEV was illustrated.According to the vehicle parameters and design requirements of the selected vehicle model,the design of the powertrain system was calculated and finally determined.Then,according to the vehicle dynamics theory,the motor parameters,the battery parameters and the speed ratio of the transmission were matched respectively.Finally,the simulation model of the vehicle was built in ADVISOR.Based on the previous analysis of powertrain components of PHEV,a mathematic model of engine and motor was built through steady-state experimental data and MATLAB mathematical toolbox.According to the knowledge of vehicle dynamics,the optimization variables,optimization targets and optimization constraints of optimal speed ratio matching between powertrain and transmission system were determined.The speed ratio of optimized transmission system was calculated by using complex method.Results of optimization are showed that the optimal method maintained the original vehicle design Dynamic performance and enhance the entire vehicle fuel economy.After the analysis and discussion of the control strategy used in current hybrid electric vehicles,the author finally decided to take the fuzzy control strategy as the research strategy of this paper.Fuzzy controller has two inputs:ΔT----the difference between the driving torque of the vehicle required by the real operating conditions and the target torque of the engine;the SOC value of the battery.Relevant fuzzy control rules were formulated.and the set value of k was regarded as the output.On the basis of ensuring the the complete charge-discharge cycle of the battery and of ensuring the engine to work in the most efficient range as much as possible,the fuzzy control device was designed.Afterwards,based on MATLAB/SIMULINK,ADVISOR was secondarily modeled,and the related fuzzy control strategy was completed to replace the electric auxiliary control strategy in the original vehicle,which would make preparations for the following simulation.Taking the new European driving cycle condition as the road condition of the PHEV selected in this paper,the PHEV was then studied through software.The results show that the simulation of fuzzy control strategy is advantageous in power performance and economic emissions over the power assisted control strategy of the original model,and the overall efficiency of the vehicle has also been improved.After that,the two control strategies are simulated with multi-conditions(UDDS,ECE,NYCC,FTP).The simulation results also show the superiority of fuzzy control strategy under the same working conditions and the self-adaptive ability and stability of fuzzy control under different working conditions. |
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