Modelica extensions for Multi-Mode DAE Systems
Hilding Elmqvist, Sven Erik Mattsson, Martin Otter · Linköping electronic conference proceedings · 2014
This paper describes a proposal for modeling systems with multiple operating modes, such as changing a controller from nominal operation to startup or shutdown or describing failure situations where the model structure is changing (e.g. an electrical line or a mechanical shaft breaks).This is achieved by extending the Modelica 3.3 synchronous state machines to continuous-time state machines having continuous-time models as "states".Every model can be a "state" of a state machine, and in particular certain acausal models.Currently, no new language element is needed for Modelica, but a generalized semantics for state machines has to be introduced, such as "merge semantics for differential equations".Symbolic transformations are still handled during translation, so the generated code is efficient and there is no run-time interpreter.On the other, this feature restricts the class of multi-mode systems that can be handled.