Equation-based Modeling of Variable-structure Systems
Abstract
Equation-based languages have become a prevalent tool for the modeling
and simulation (M&S) of physical systems. Their declarative style
enables the design of self-contained models that are liberated from
system-specific computational aspects. Variable-structure systems form
a collective term for models, where equations change during the time of
simulation. This class of models is generally not supported in M&S
frameworks. The current languages lack the required expressiveness, and
further limitations are imposed by technical aspects of the
corresponding simulation framework. This thesis explores the modeling
of variable-structure systems for equation-based languages in full
generality. For this research purpose, a new modeling language has been
designed based on the prominent language Modelica. By generalizing
prevalent language constructs, the new language becomes not only
simpler but also more expressive. In this way, almost arbitrary
structural changes in the set of equations can be described. A
corresponding simulation environment supports the new language and
incorporates new and dynamic methods for index-reduction of
differential-algebraic equation systems. Models of four systems of
different domains exemplify the use of the language and demonstrate
the robustness of the proposed modeling methodology.
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Last modified: June 16, 2010 -- © François Cellier