Research On Power System Modeling And Control Strategy Of Dual-planetary Gear Hybrid Electric Vehicle

In recent years, the problem caused by the energy shrotage and environmental pollution is getting more and more serious. This brings great challenges to our living. At present, because of its excellent fuel economy and low emission recognised by the world, the HEVs(hybrid electric vehicles) have become one of the most important orientation of the future automobile development and research point. The hybrid vehicles equipped with dual-planetary gear set can not only leave out the traditional transmission, effectively simplify the power system structure, but also can enrich the system operation modes, improve the dynamic performance of the coupling mechanism, overcome the shortage of single-planetary or three-planetary coupling device. It has stronger practicability and value of research.The paper is based on the project: Research on dynamic modeling and optimal control for dual-planetary gear hybrid electric vehicle energy management system based on hybrid. For a new kind of hybrid coupling device formed by two single planetary gear sets, the characteristic parameters rationality, system operation modes, kinematics and dynamics analysis, the vehicle model and control strategy building and co-simulation were researched.Firstly, for the new dual-planetary hybrid coupling device, the rationality of the gear set characteristic parameters selection was verified from the angle of the system efficiency. On the basis of the analysis, two brakes and one clutch were added to further optimize the system power structure.Secondly, according to the different states of the brakes, clutch and power conponents, the operation modes of the system were divided reasonably. By using the lever analogy, each pattern was analyzed deeply and the kinematics equations and dynamics equations are obtained respectively.Thirdly, with the aid of the AVL/Cruise platform, the dual-planetary gear hybrid electric vehicle model was built. Considering the feature of power components: speed and torque decoupling from the load, the traditional PI algorithm was introduced and implemented to control the engine speed. The engine constant working point control strategy and the engine optimal operation line control strategy were built up in the MATLAB/Simulink software. After that the co-simulation and analysis were carried out respectively. The simulation results show that, compared with the engine constant working point control strategy, the overall fuel can be saved by 9.74% under the engine optimal operation line control and the battery SOC was kept in a better range.Finally, because of the shortage of the traditional PI parameter regulation in the engine optimal operation line control strategy, the fuzzy control algorithm was imported to revise the PI parameters of engine’s each power point of optimal operation line in real time. The simulation results show that, with the help of the fuzzy PI control, the engine speed responses more sensitive and timely, comparing with the traditional PI control. And also the fuzzy algorithm effectively restrained the engine speed fluctuation. The new control system achieved a better fuel economy performance by 2.83% than the traditional PI control system.