Approximate Dynamic Programming Applied to Parallel Hybrid Powertrains
Paper in proceedings, 2008
The extra degree of freedom offered in hybrid electric vehicles have inspired many
researchers to formulate and solve optimal control problems of various kinds. This paper presents
an Approximate Dynamic Programming scheme that efficiently solves the optimal power split
between the internal combustion engine and the electric machine in parallel hybrid powertrains.
Gear switches and switches between hybrid and pure electric mode are formally treated. The
scheme combines two ideas to reduce the computational time of the iterations performed in
the dynamic programming. First, the value function is approximated using piecewise linear
functions on a sparse grid. Secondly, by using model approximation the iterations performed in
the dynamic programming are reduced to solving scalar quadratic problems. In the simulations
the approximation scheme is able to find a good approximation of the optimal control trajectory.