Solution of a Hybrid Optimal Control Problem For a Parallel Hybrid Vehicle

In this paper, an algorithm for solving a nonlinear hybrid optimal control problem for the fuel-optimal operation of a parallel hybrid electric vehicle is proposed. The proposed algorithm is very simple in its application and allows for finding the optimal controls in hybrid drive mode, as well as optimal discrete dynamics. In particular, the discrete decisions gear choice and drive mode are regarded. The algorithm uses an indirect variation of extremals approach based on necessary conditions for hybrid optimality. For better solvability, we accept the fact, that the solution becomes suboptimal, when encountering state constraints. It will be shown that the solution obtained provides a set of valuable information for the definition of the energy management for a given vehicle. The algorithm can be adapted to other configurations of hybrid vehicles and can be used to determine optimal controls on any drive cycle.