Approximate Dynamic Programming applied to a Four Quadrant Transducer Series-Parallel Hybrid Electric Bus

This paper presents an Approximate Dynamic Programming scheme that, based on the assumption of perfectly known future driving, efficiently solves the optimal power split in a Series-Parallel hybrid powertrain. The scheme combines two ideas to reduce the computational load of the dynamic programming. First, the cost-to-go function is approximated using piecewise linear functions on a sparse grid. Secondly, by using precalculated maps, the iterations performed in the dynamic programming are reduced to simple table lookups and linear interpolation. The approximation scheme is simulated on a Four Quadrant Transducer Series-Parallel Hybrid Electric Bus. In the simulations the approximation scheme is able to find a sufficiently good approximation of the optimal control trajectory.