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Cubic Spline Approximations of the Dynamic Programming Cost-to-go in HEV Energy Management Problems

Viktor Larsson (Institutionen för signaler och system, Reglerteknik) ; Lars Johannesson (Institutionen för signaler och system, Reglerteknik) ; Bo Egardt (Institutionen för signaler och system, Reglerteknik)
13th European Control Conference, ECC 2014; Strasbourg Convention and Exhibition CenterPlace de BordeauxStrasbourg; France; 24 June 2014 through 27 June 2014 p. 1699-1704. (2014)
[Konferensbidrag, refereegranskat]

The energy management problem of a hybrid electric vehicle (HEV) is a non-linear and mixed integer optimization problem. The problem can be solved with Dynamic Programming (DP), but the algorithm requires the problem to be gridded in time, states and control signals. To ensure a high accuracy of the solution the grid must be dense, meaning that the cost-to-go can require several megabytes of memory. The scope of this paper is therefore twofold. The first topic is a sensitivity study, where the effect of a sparsely gridded state is investigated, both for an HEV and a plug-in HEV (PHEV). The study shows that it is possible to use a sparse grid for an HEV, but not for a PHEV. The second topic and the main contribution is a method to approximate the DP cost-to-go with cubic splines. The results indicate that it is possible to use only a few splines, if the knot points are determined based on the characteristics of the cost-to-go. Thereby it is possible to significantly reduce the memory requirements, without any noticeable increase in simulated fuel consumption.


Article number 6862404



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Denna post skapades 2014-06-09. Senast ändrad 2015-05-08.
CPL Pubid: 198988

 

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Institutioner (Chalmers)

Institutionen för signaler och system, Reglerteknik (2005-2017)

Ämnesområden

Energi
Transport
Hållbar utveckling
Reglerteknik

Chalmers infrastruktur

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