  An optimal control based methodology is proposed for minimising the
combustible fuel consumption of a hybrid vehicle equipped with an internal
combustion engine, a high-speed flywheel and a battery. The
three-dimensionality of the road is recognised by the optimal control
calculations. Fuel efficiency is achieved by optimally exploiting the primary
and secondary energy sources and controlling the vehicle so that the fuel
consumption is minimised for a given, but arbitrary three-dimensional route. A
time-of-arrival constraint rather than a driving cycle is used. The benefits of
using multiple auxiliary storage systems are demonstrated and a lower-bound
estimate of the fuel consumption is presented.
