Randomly Under The Condition Of Parallel Hybrid Electric Vehicle Control Strategy Research

Hybrid Electric Vehicle (HEV), which incorporates the advantages of both the conventional internal combustion engine (ICE) vehicle and the battery electric vehicle, has been recognized as one of the most promising alternative fuel vehicles. It is also an important solution to deal with the problems of energy shortage and environmental pollution. Control strategy, as one of the key techniques of HEV, plays a decisive part in vehicle performance and has been one of research focuses. However, for a long time, the control strategy of HEV is established based on a particular driving cycle and the significant effects of driving cycle on vehicle performance hasn’t receive critical emphasis. On the other hand, most of HEVs still choose Electric Assist Control Strategy, whose control parameters are static. So the distribution of power source won’t get optimized, and it can’t reach the purpose of improving vehicle performance. Based on the two defects of control strategy above, the Markov chain model of driving cycle and the method of using Fuzzy Logic to adjust parameters dynamically are proposed in this paper.Firstly, this paper introduces basic theory, fuel-saving mechanism and classified method of HEV, then gives brief introduction and summary to the current control strategy concerning on the problems and difficulties of Parallel Hybrid Electric Vehicles. According to the structure of PHEV. electric vehicle simulator ADVISOR2002is seleced for modeling and simulation in next chapter.Secondly, we analysis the effects of driving cycle on both control strategy and vehicle performance in details and point out that there are some contradictories between randomness of real driving cycle and control strategy based on specific driving cycle, which lacks of ability to adapt to different driving cycles. So in this paper a stochastic model based on Markov Chain is set up to predict the driving cycle of vehicle.Thirdly, this paper focuses on the control parameters of Electric Assist Control Strategy, presenting its influence on fuel economy and automotive dynamics. Then Fuzzy Logic algorithm is chosed to adjust appropriate parameters dynamically, so as to distribute energy reasonably.Simulation results show that compared to the traditional Electric Assist Control Strategy, this proposed control strategy can effectively improve the fuel economy of HEV and adapt to random driving cycle well.