Lennart Ochel
Bielefeld University of Applied Sciences, Department of Mathematics and Engineering, Bielefeld, Germany
Bernhard Bachmann
Bielefeld University of Applied Sciences, Department of Mathematics and Engineering, Bielefeld, Germany
Francesco Casella
Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Milano, Italy
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http://dx.doi.org/10.3384/ecp140961179Published in: Proceedings of the 10th International Modelica Conference; March 10-12; 2014; Lund; Sweden
Linköping Electronic Conference Proceedings 96:124, p. 1179-1187
Published: 2014-03-10
ISBN: 978-91-7519-380-9
ISSN: 1650-3686 (print), 1650-3740 (online)
The amount of needed initial equations in an object-oriented model can only be determined at system level. Because Modelica models are generally designed by components; it is hard to figure out all needed initial conditions at system level; even more when changes are applied to the model; e.g. by adding or removing components. Hence; it is more convenient to define initial equations at component level. Due to component connections; algebraic dependencies between states may be introduced; which eventually lead to the removal of states when symbolic index reduction algorithms are applied. In this process the corresponding initial equations are not automatically removed and an over-determined initial system ensues.
This paper describes an algorithm that detects such redundant equations and determines if they are consistent or not. Consistent redundant initial equations can thus be removed automatically; and inconsistent ones can be reported to the modeler. The algorithm is implemented in OpenModelica; tested on several representative cases; and compared to previously presented concepts.
