Energy Management Optimal Control Strategy In Consideration Of Battery Lifetime For Hybrid Electric Vehicle

Hybrid electric vehicle, because of its own advantage in energy saving and reducing environmental pollution, is gaining the favor of broad consumer on a global scale increasingly. One of the key technologies to full use of the advantages of energy conservation and emissions reduction of hybrid electric vehicle is the designed energy management strategy in electronic control unit. For problems of both real-time application of energy management optimization of hybrid electric vehicle and improvement of the vehicle total economy, considering the facts that incomprehensibility of road traffic information in the future, the operation of the actual energy management strategy could not rely on a fixed condition, the frequent battery charge and discharge leads to the irreversible battery lifetime degradation, the energy management optimal control strategy for commuter hybrid electric vehicle is researched in this paper. Main researches are shown as follows:Firstly, the traffic information model is established for commuter hybrid electric vehicle energy management optimal control strategy. Considering that the traffic route of a commuter vehicle is almost fixed, the statistical properties of average speed of relative distance are used to describe the traffic information of driving route. And based on the same statistical properties, the whole journey could be divided into several segments. Then an optimal control-oriented traffic information model is established by using maximum likelihood method of probability theory in each segment.Secondly, by using the stochastic traffic information model, the energy management problem of commuter hybrid electric vehicle can be converted into a stochastic optimal control problem. And by taking into account the physical constraints of the improved stochastic dynamic programming strategy iterative algorithm, the problem of stochastic optimal control is then solved. An energy management strategy considering traffic information with the minimum equivalent fuel consumption in average sense is designed.Thirdly, based on the designed energy management strategy with both traffic information and the minimum of equivalent fuel consumption used in average sense, moreover, considering the influence of the battery life on the vehicle fuel economy, the original data of battery lifetime is transformed into a simpler model used for optimization control by curved surface fitting method. On this basis, a multi-objective stochastic optimal control problem with target of minimizing both the energy consumption and battery life is put forward. With the form of price, the multi-objective optimization problem will be converted into a single objective optimization problem. A commuter plug-in hybrid electric vehicle energy management strategy with consideration of battery lifetime degradation is proposed by using policy iterative algorithm of stochastic dynamic programming.Finally, the simulation models are built in the MATLAB/Simulink platform by using the related data of Toyota Prius automobile, and the designed energy management optimization strategy is verified through the above simulation models.