System Modeling And Performance Simulation Of Differential Coupling Hybrid Electric Vehicle

Hybrid Electric Vehicl(eHEV)is a hot study topic in the automotive industry. HEV includes three typical structures which are SHEV,PHEV and SPHEV(series,parallel and series-parallel). To SHEV,it is easy to achieve the best control of the engine as there is no direct connection between the engine and the driving wheel; to PHEV,there is a direct connection between the engine and the driving wheel,so it can drive the vehicle directly and the efficiency is higher; SPHEV has the advantages both of SHEV and PHEV. However,the studies of HEV focus on SHEV and PHEV in our country. The study of SPHEV is less.In the study of SPHEV,the key problem is to study and develop an excellent dynamic coupling system. However,Prius HEV of Japan Toyota Automobile Corporation has got a great success and its THS dynamic coupling system has got the international patent. It limits the development of SPHEV in our country. As a result,it is significant to develop and study the dynamic coupling system with our own patent. It is meaningful to break the restriction of the international patent.The study of this paper is supported by National Natural Science Foundation. Has completed part study of the subject named"Study on Drive Theory and Control Theory of New SPHEV Dynamic System". It is helpful to the subsequent study.First, analyze the driving mechanism of Differential Hybrid System(DHS).In the distribution characteristics of rotary velocity, the sum of the rotary velocity of the left and the right gears is twice of the rotary velocity of the differential shell. In the distribution characteristics of the torque, DHS can distribute the torque evenly. The engine, the generator and the motor are correspondingly connected with the differential shell and the left and the right half axle gears. This kind of connection is better, because most of the energy can be used to drive the vehicle directly and other energy can work in the way of energy conversion. Also, to the generator, the battery and the motor, the need of the power and the capacity is smaller than other kinds of connections. Compared with THS, the transmission ratio of DHS is different, but DHS can also achieve the functions of dynamic coupling. As the device of dynamic coupling, it is a unique method.Second, referring to the successful product of Toyota Prius, complete the selection of the types and the parameters for the engine, the motor, the generator and the battery. On this basis, build the model of Differential Coupling Hybrid Electric Vehicle in AMESim. The modeling method of AMESim is similar to the method of Power Bond Graph. It expresses the physical models in figures, so it is easy to model. The models mainly include: cycle model, driver model, engine model, motor model, generator model, battery model, differential coupling device model, vehicle body model, the co-simulation interface model and so on. Among them, it is a characteristic that the differential coupling device is used to achieve the functions of dynamic coupling.Third, study and analyze the control strategies of series-parallel hybrid electric vehicle. Analyze the typical control strategies which are Engine Constant Operating Point Strategy, Engine Optimal Operating Curve Strategy, Instantaneous Optimal Strategy, Overall Optimal Strategy and Power Demand Strategy. They have different features. Among them, Power Demand Strategy depends on the engineering experience and the experiments, so it is much more feasible. Basing on Power Demand Strategy, build the control strategy model and control the hybrid electric vehicle.Finally, finish the co-simulation of AMESim model and Simulink model. Then debug and improve the models through the simulation. Select four typical city cycles which are NEDC, ECE-EUDC, JAPAN-1015, China Sedan Cycle and simulate in these cycles. The simulation results verify the distribution characteristics of rotary velocity and torque. The dynamic coupling functions are consistent with the theory analysis. Through the simulation, the maximum vehicle velocity achieved when the driving force is equal to the driving resistance is 37.8m/s that is equal to 136.1km/h and the velocity following characteristic is well which prove that the dynamic performance of the vehicle model is well. In the aspect of the fuel economy, the fuel consumption of Differential Coupling Hybrid Electric Vehicle in the different cycles is close to the published value of Toyota Prius. It shows that the study and development of Differential Coupling Hybrid Electric Vehicle have good prospects. Differential Coupling Hybrid Electric Vehicle provides a unique method to solve the problems of dynamic coupling in a series-parallel hybrid electric vehicle. This method can break through the restriction of the successful product with the international patent, and it can well achieve the functions of dynamic coupling, and the performance of the vehicle is also well. So its prospect is well. Through the further study, the final goal is to get the dynamic coupling product with our own patent.