Research On HEV Acceleration Performance Prediction

As a representative of the new fuel-efficient vehicles, the hybrid vehicles have significant advantages of high efficiency and high reliability. Accelerating performance is the basic evaluation index of vehicle dynamic performance. Furthermore, it has been the basis of vehicle driving performance. Good acceleration performance is the guarantee of vehicle power performance. In this paper, one type of vehicle with electro-mechanical transmission(EMT) is studied specifically. The prediction and optimization of the EMT’s acceleration performance is very important for the study of its power flow and dynamic performance.In this paper concerning EMT, vehicle’s acceleration performance is analyzed, and the acceleration performance prediction model is established. An optimization method for the acceleration performance based on variable rotational mass coefficient is presented. Besides, an optimal starting acceleration strategy is obtained. At last, the results are verified by numerical simulation and bench test.According to the basic rule and the essential parameters of the acceleration process of EMT system, a simulation model is established to study the longitudinal dynamics model of the acceleration process, and the equivalent inertia moment of the whole vehicle is calculated. Based on the Matlab/Simulink simulation platform, the simulation model of the 40t-level electro-mechanical transmission vehicle is established. In particular, the mean value model of the diesel engine is established using modular modeling method and the engine cycle variation is neglected. The accelerating performance prediction model including engine, motors, battery pack, planetary coupling mechanism, load and control unit module is established. Numerical simulations show that the acceleration performance prediction model can reflect the dynamic changes of the components, and calculate the acceleration performance accurately. As a result, the acceleration time from 0 to 32km/h is 5.4s.The variable rotational mass coefficient is proposed and conducted, and its application law in EMT is studied. The optimal acceleration process control strategy is obtained considering variable rotational mass coefficient. In comparison with the strategy regardless of the variation of rotational mass coefficient, it turns out that vehicle acceleration performance can be promoted by considering the variation of rotational mass coefficient,with an acceleration time from 0 to 32km/h of 5.4s. In the Matlab/GUI platform, a graphical computing program is compiled.To verify the validity of the acceleration process simulation model, the EMT low-power function prototype bench test based on the 40 t level EMT vehicle is built. Besides, the engine transfer function is obtained by bench test identification and its Simulink model is established. The simulation results show that the acceleration time from 0 to 70km/h is 4.7s. In the end, experimental verification is accomplished comparing to the simulation results of the acceleration performance prediction and optimization. The experimental results show that the acceleration process simulation model can accurately calculate the vehicle acceleration performance with EMT system. The acceleration time from 0 to 70km/h is 4.9s.