SIMULATION AND OPTIMAL CONTROL OF HYBRID ELECTRIC VEHICLES

摘要

New strategies for controlling the power split in hybrid electric vehicles (HEV) are described. The strategies focus in a planetary gear system, where kinematic and dynamic constraints must be fulfillied. The aim is to satisfy driver demands and to reduce fuel consumption. Two strategies are presented, one inspired on optimal control and the other derived from Pontryagin's Minimum Principle. It is shown that, under appropriate choice of weighting parameters in the cost function of the Hamiltonian, both strategies are similar. The resultant power flow control is continuous and uses the internal combustion engine with the maximum efficiency possible. The main advantages are the low computational cost, when compared to other optimization based approaches, and the easiness to tune. The strategy is tested by simulations using a mathematical model of a power train of a hybrid diesel-electric bus subject to the power demands of representative urban area driving cycles. The main elements of the vehicle, internal combustion engine (ICE),battery state of charge (soc), electric machine (EM) and vehicle inertia are simulated with high order models. Simulation results indicate that both strategies achieves small speed tracking errors and attain good fuel consumption reduction levels.