Optimal Control of a Vehicular Organic Rankine Cycle via Dynamic Programming with Adaptive Discretization Grid

This paper addresses the problem of maximizing the power produced by an organic rankine cycle (ORC) waste heat recovery (WHR) system along a given vehicle mission. A simplified model of the system allows the formulation of an optimal control problem that can be solved via dynamic programming (DP). To increase the smoothness and the accuracy of the solution obtained using the state-of-the-art implementation of DP known as level-set DP, an improved version is developed, making use of adaptive grids for discretization. The adaptive-grid algorithm is first validated on a simple problem with an analytical solution, then applied to the more complex ORC case study. It is shown that the required accuracy can be achieved with a lower computational effort than the original algorithm. The analysis of the resulting optimal trajectory for the ORC control problem provides useful insight for both control design and system design.