Classical and statechart - based modeling of state events and of structural changes in the Modelica - Simulator Mosilab

Mosilab (MOdelling and SImulation LABoratory) a new simulation system developed by Fraunhofer understands Modelica, offers different modeling approaches, and support structural dynamic systems. This will be discussed on the basis of a main example, the classical constrained pendulum. We show how the solution can be done using only standard Modelica components, where the benefits are and which kind of switching the states can be done. As we will see there is no possibility to define separate submodels with different state space dimensions and switch between these systems during one simulation run. The next point of view lies on an extension of the Modelica framework. The most important new feature of this model description language is the definition of a statechart framework. With this construction the next three solutions of the constrained pendulum are done. The first approach is mathematically similar to the Modelica solution and defines poor parameter events within the statechart construct. This approach cannot handle events of higher order. The second approach for the model is done with two different submodels, one for the case that the rope of the pendulum is short and one for the case it is long. In the statechart the two models are then connected and disconnected to the main program and thereby switched between active and off. A third approaches with only one submodel but two instances of the system will conclude our model inspection. We focus on how the numerical approaches are done in general and where are the benefits comparing to the other solutions. A final step is to look at the numerical quality of the output of the different approaches. This is done by validation with another example for which an analytical solution exists.