Research On The Optimization Of Parallel Hybrid Electric Truck Energy Management Strategy

In order to solve the increasingly acute environmental pollution and energy shortage problems,hybrid electric vehicles that combine the advantages of traditional internal combustion engine vehicles and electric vehicles have gradually become the focus of attention.In the process of developing hybrid electric vehicles,how to build a mathematical model of the vehicle and design a reasonable energy management strategy are very important.To ensure the vehicle dynamic performance and fuel economy improvement,this paper develops the modeling and energy management strategies for the hybrid power system,with taking the heavy truck based on the engine power take off as the research object.According to the characteristics of the engine power take off as the hybrid coupling mechanism,using the automobile theory and automobile dynamics knowledge,the determination of hybrid electric truck performance parameter index and the parameter matching scheme of the important components of power system are determined to meet the dynamic and economical requirements of the truck under the corresponding driving conditions.In the AVL/CRUISE simulation software,this paper build the vehicle model of the hybrid electric truck,including a vehicle model,an engine model,a motor model,a battery model,a transmission model,and a driver model.The energy management strategy based on logic threshold is designed.The hybrid electric vehicle control strategy model is built in MATLAB/Simulink platform.In order to achieve the minimum fuel consumption of the vehicle,the battery state of charge and its upper and lower limits,and the vehicle demand torque are selected as logic threshold values.Through the division of the optimal working range of the engine and battery and the judgment of the working mode of the hybrid electric vehicle,the energy flow direction and energy distribution rules of different working modes are analyzed,and the controller model based on the logic threshold is built in Stateflow.The hybrid electric vehicle is simulated by combining the model of the vehicle components and the designed controller model.The simulation results verify the effectiveness of the energy management strategy designed by the hybrid electric truck.An energy management strategy based on ECMS algorithm is designed.The multi-stage decision-making problem of energy distribution between two power sources of hybrid electric vehicles is transformed into multiple single-stage decision problems with the minimum fuel consumption under certain constraints,and solved by ECMS algorithm.In each control cycle,according to the real-time working state of the hybrid electric vehicle,all the engine and motor torque distribution combinations are calculated,the minimum equivalent fuel consumption corresponding to the combination of the engine and the motor torque are obtained and used it as a working point for output torque.The characteristics of the two equivalent factor penalty functions are analyzed.The objective function of the system is established based on the vehicle fuel consumption function and the battery state of charge penalty function.The optimal control rule of the optimal theoretical fuel economy and energy distribution of the vehicle under specific working conditions are obtained.It is proposed to optimize the engine torque in ECMS by genetic algorithm and the value of SOC target value,finding a reasonable torque distribution.This could make the fuel consumption of the whole process close to the theoretical optimal value as much as possible.Through the analysis of the simulation results of the energy management strategy,the ECMS energy management strategy based on the genetic algorithm optimization designed in this paper makes the engine work more in the high efficiency area and effectively reduces the fuel consumption of the hybrid electric vehicle.The stability of the battery nuclear power state is well guaranteed during the simulation.