| Recent years,the rapid development of automobiles in China has brought serious energy crisis and environmental pollution problems.As an important way for the auto industry to get out of the predicament,the new energy vehicle has received great attention and policy encouragement from the government.Although the electric vehicle is the ultimate goal of the development of new energy vehicles,it is restricted by factors such as cost,energy density and battery life,making it difficult to popularize.On the basis of the configuration of the pure electric vehicle,the extended-range electric vehicle adds a set of range extender,which reduces the cost of the whole vehicle and extends the driving range of the vehicle.It is an excellent choice for the transition to the pure electric vehicle.The main energy source of the extended-range electric vehicle is the power battery,and the battery will age in different degrees under different conditions,which will affect it’s capacity and power.Therefore,on the basis of analyzing and researching the decay law of power battery life,this paper formulates a vehicle control strategy for the extended-range electric vehicle and allocates energy to minimize the total operating cost of the vehicle and to protect the battery and prolong its life.The specific work of the article is as follows:(1)Based on the project of the research group,we designed an extended-range vehicle.After clarifying the power system structure,vehicle parameters and performance indicators,the three main power components of the extended-range electric vehicle,the motor,battery pack and range extender,were matched with parameters.And product selection was made on the market according to the matching results.(2)Then,the thesis analyzed the working principle of the lithium battery for electric vehicles and the factors that influnce the cycle life.Then conducted an electrochemical performance experiment on a certain lithium power battery under laboratory conditions,and studied its cycle performance in different processes.After that,a multi-factor prediction model(referred to as multi-factor prediction model)for the cycle life of the lithium power battery was established by using statistics and regression methods.Further,according to the principle of vehicles,the multi-factor predictive model is discretized into the driving process of the car,paving the way for the subsequent simulation process.(3)Analyzed the structure of the vehicle control system and various control strategies of the extended range vehicle.Based on the operating characteristics of the extended range electric vehicle and the purpose of improving the life decline of the power battery,the thesis formulated some principles of the control system.Because the battery power state will change under the conditions of different SOC,temperature and battery health,the SOP table and the law of battery power decline with battery life were given.Then designed a fuzzy control strategy of APU.In the control strategy,the key membership function parameters were initially selected based on empirical values,which has certain subjectivity and limitations.Therefore,in order to achieve the goal of optimal vehicle operating cost,combined with the battery power state,a genetic algorithm is introduced to optimize the parameters of the membership function in real time under different conditions until the optimal solution under the objective function is found.Finally,with the goal of recovering as much energy as possible,on the basis of ECE regulations,the regenerative braking force was allocated reasonably and the flow chart of regenerative braking control was given.(4)According to the matching results of the extended-range electric vehicle power system and the formulated vehicle control strategy,a vehicle simulation platform was established in Advisor,and the control strategy algorithm was written in MATLAB/Simulink.The two were jointly simulated to verify the whole vehicle can meet the requirements of power performance indicators.Then,in the case of different ambient temperature,initial SOC and running time,the fuzzy control optimized by genetic algorithm and the traditional single-point strategy were compared.The simulation results showed that the fuzzy control strategy of using APU to compensate the discharge of the power battery can reduce the battery’s life decline and prolong its service life in the daily working condition cycle.But taking the battery loss into the total cost,in some cases there were not be much improvement compared to before.However,as the temperature increases,the initial SOC decreases and the running time increases,the optimization of the fuzzy control strategy will improve the economy of the vehicle more obviously. |
