Research Of Torque Distribution Strategy For Parallel Hybrid Electrical Vehicle

Hybrid electric vehicle was researched extensively for its great fuel economy and dynamic property that could catch up with traditional oil fired automobile in recent years. Since the driving system of hybrid electric vehicle has engine driving system and motor driving system, it needs to make a torque distribution strategy to distribute the engine torque and motor torque reasonably.This article established a torque distribution strategy on restricted engine on-off based on parallel Hybrid Electric Vehicle driving system with a torque coupler. This torque distribution strategy established a low engine torque curve in the engine universal characteristic map, the engine will be always restricted to work in the economy area between the low engine torque curve and high engine torque curve. It not only can always make the engine work efficiently, but also can avoid the energy loss made by energy transformation.The engine model, motor model, battery model and vehicle dynamic model were built based on Matlab/simulink, and then built the backward vehicle model to test the torque distribution strategy in simulation experiment. The simulation running condition was NEDC that combines urban running condition and suburb running condition. Since the low engine torque curve coefficient λ is a key parameter and different low engine torque curve coefficient will exert a great influence on the vehicle working modes and fuel economy, the simulations were conducted as λ was 0.7, 0.5 and 0.3 to study the influence on practical running of Hybrid Electric Vehicle made by different λ.The simulation results were that engine working points of different λ were all distributed in the economy area between the low engine torque curve and high engine torque curve, and the vehicle primarily worked on the charging mode in the most time. When λ equals 0.7 and 0.5, the engine primarily worked at the low engine torque curve to charge the battery and without engine driving mode during all periods. Since 0.7 is higher, the time of charging battery of it at the high engine torque curve is longer than when λ equals 0.5. When λ equals 0.3, engine primarily worked at the high engine torque curve to charge the battery and engine driving mode appeared in the suburb road condition. In the end, it was found that when λ equals 0.5, its fuel economy is best and fuel consumption per hundred kilometers were only 4.34 L by the 5×NEDC simulation. Compared with the same type traditional fuel vehicles, its fuel economy improved greatly.