SLIDING OPTIMAL CONTROL IN HYBRID ELECTRIC VEHICLE ENERGY MANAGEMENT OPTIMIZATIONS

摘要

The hybrid electric vehicle is one of the promising alternatives of the enginepowered vehicle for better fuel economy and lower emissions. Energy management in the hybrid electric vehicle is regarded as an optimal control problem and has been solved by many researchers with dynamic programming, Equivalent Consumption Minimization Strategy, etc. In this paper, Pontryagin’s minimum principle is used to solve for a practical optimal solution. Since the Hamiltonian is piece-wise continuous and is not always convex, a better solution, sliding optimal control, is found for constant torque and speed requirements. The sliding optimal control cannot be implemented precisely because the switching frequency cannot be infinitely high in practice. Switching at 1 Hz is recommended according to the weak relationship between the switching frequency and the Hamiltonian. Finding the optimal solution for time-varying power requests will be accomplished next.