LiU startsida
Abstract |
Explicit fuel optimal speed profiles for heavy trucks on a set of topographic road profiles
The problem addressed is how to drive a heavy truck over various
road topographies such that the fuel consumption is minimized. Using a
realistic model of a truck powertrain, an optimization problem for
minimization of fuel consumption is formulated. Through the solutions
of this problem optimal speed profiles are found. An advantage here is
that explicit analytical solutions can be found, and this is done for
a few constructed test roads. The test roads are constructed to be
easy enough to enable analytical solutions but still capture the
important properties of real roads. In this way the obtained solutions
provide explanations to some behaviour obtained by ourselves and
others using more elaborate modeling and numeric optimization like
dynamic programming. The results show that for level road and in small gradients the
optimal solution is to drive with constant speed. For large gradients
in downhill slopes it is optimal to utilize the kinetic energy of the
vehicle to accelerate in order to gain speed. This speed increase is
used to lower the speed on other road sections such that the total
average speed is kept. Taking account for limitations of top speed the
optimal speed profile changes to a strategy that minimizes brake
usage. This is done by e.g. slowing down before steep down gradients
were the truck will accelerate even though the engine does not produce
any torque.
Anders Fröberg, Erik Hellström and Lars Nielsen
2006
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Last updated: 2021-11-10
