Simulation-Based Development of Safety Related Interlocks - Simulation and Modeling Methodologies, Technologies and Application - page 164

Fig. 2. The purpose of the transformation is to add the control system specific parts to an existing
model of the physical process
specified by OMG. The possibility to use standardized transformation languages with
existing open source tool support and the open source background of Modelica and
ModelicaML are good reasons for selecting Modelica as the target simulation language
in our approach.
In Modelica (and in ModelicaML) simulation classes are defined separately from
their use context, similarly to classes in object oriented programming languages. In
ModelicaML models, the model elements also need to reference the ModelicaML pro-
file in order to use the stereotypes and tagged values of it. This results in a structure
sketched in the left side of figure 2. ModelicaML models consist of Modelica class def-
initions and instances of the classes. Classes may contain ports with which they can be
connected and both the definitions and instances of the classes need to use the stereo-
types of the ModelicaML profile in order to map the concepts to Modelica keywords.
In our approach, we assume that ModelicaML models of processes to be controlled are
available and conform to this structure.
The purpose of the transformation is to create and add the control system specific
parts to the existing model of the process to be controlled and to connect the created
parts to the existing model so that the controlled system can be simulated. In this pro-
cess, Modelica class definitions corresponding to platform independent (PIM) and plat-
form specific (PSM) UML AP elements are copied to the model of the process to be
controlled (process model) so that they can be referenced from the process model. In-
stances of the templates are instantiated to the process model and connected together
according to the control system model in the UML AP tool. Instances corresponding to
measurement and actuation AutomationFunctions are connected to the elements of the
process model that are used to model sensors and actuators.In more detail, this process
and the characteristics of different kind of AFs are discussed in detail in [19].
However, because interlocks are specific to applications they cannot be librarized, as
explained earlier. Instead, the definitions of interlock classes need to be created by the
transformation based on the logic diagrams. This process is rather simple and illustrated