Conference article

Collocation Methods for Optimization in a Modelica Environment

Fredrik Magnusson
Department of Automatic Control, Lund University/Modelon AB, Lund, Sweden

Johan Åkesson
Department of Automatic Control, Lund University, Sweden

Download articlehttp://dx.doi.org/10.3384/ecp12076649

Published in: Proceedings of the 9th International MODELICA Conference; September 3-5; 2012; Munich; Germany

Linköping Electronic Conference Proceedings 76:66, s. 649-658

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Published: 2012-11-19

ISBN: 978-91-7519-826-2

ISSN: 1650-3686 (print), 1650-3740 (online)

Abstract

The solution of generic dynamic optimization problems described by Modelica; and its extension Optimica; code using direct collocation methods is discussed. We start by providing a description of dynamic optimization problems in general and how to solve them by means of direct collocation. Next; an existing implementation of a collocation algorithm in JModelica.org; using CasADi and IPOPT; is presented. The extensions made to this implementation are reported. The new implementation is compared to an old C-based collocation algorithm in JModelica.org in two benchmarks. The presented benchmarks are based on a continuously stirred tank reactor and a combined cycle power plant. The new algorithm and its surrounding framework is more flexible and shown to be several times more efficient than its predecessor.

Keywords

dynamic optimization; JModelica.org; collocation; nonlinear programming; CasADi

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