Study On The Dynamic Control In Parallel Hybrid Electric Vehicle

It is necessary for Parallel Hybrid Electric Vehicle (PHEV) to distribute energy between engine and motor and to control state-switch during work. Compared with the numerous documents about the energy distribution, the research on state-switch control is rarely seen to report. In fact, the state-switch between operating-modes is a transient process, in which the dynamic control is aimed at keeping the vehicle running smoothly whilst maintains the hybrid system almost the same in power performance, fuel economy, low emission and driving comfort. In face of such a problem this paper successfully accomplishes the dynamic control research by following the technical route from literature research, vehicle modeling, preliminary test and algorithm simulation to validation test.According to the purpose of the dynamic control, a dynamics theoretical model for PHEV system is built, which includes the pseudo-bond graph IC engine model built on the basis of its thermodynamics process, AL4 automatic transmission model built on the grounds of lever-method and the frame for the multi-energy power control unit.In view of the limitation of the bond-graph IC engine model in practice control, this paper focuses on the experiment investigation in the steady and dynamic characteristics of IC engine, by which the dynamic property of engine with the change of rotate speed, throttle percentage and its change rate is obtained. Based on the experimental data and taking on the advantage of neural network in function approximation, the steady and dynamic engine torque estimation models are constructed.Aimed at keeping the total torque unchanging under state-switch, the dynamic control algorithm is put forward, which can be expressed as motor torque compensation for engine after torque pre-distribution, engine speed regulation and dynamic engine torque estimation. Taking Matlab/Simulink as the platform, the vehicle control simulation model is built and validated under driving cycle, based on which the fundamental control algorithm is verified by simulation testing with fixed state-switch conditions and consecutive state-switch conditions.The dynamic control algorithm is finally validated by experimental tests which are achieved by means of building test-bench and getting help from the rapid control prototyping tool, dSPACE. The results demonstrate that the dynamic control algorithm can effectively dampen torque fluctuations and ensures power transfer smoothly under various state-switches.