Figure 3. Modelica model structure
2.1 Model program structure
Modelica program structure is such like Figure 2. The simplest model is Figure 3. Within
the blocks model simpleModel and equation, variables can be declared. Within the block between
equation and end simpleModel, equations and connection statements can be put into. In Modelica
not only Model can be declared, but Record, Class, Connector, Function. Everything can also be
treated as an object.
2.2 Object-Oriented Modelica
Modelica is Object-Oriented. There are several objects in Modelica: Class, Model, Connec-
tor, Record, Block, Function. Each type of class can be inherited. Modelica has encapsulation.
The models of system components are connected through rigorously defined interfaces or connec-
tors(e.g. Fluid connectors with pressure, flow rate, and enthalpy, or heat connectors with temper-
atures and heat fluxes). Any two components with compatible connectors can be bound together,
regardless of their internal details.[6] In each class, there can be multi-type classed be declared.
These can help multi-physics modeling.
2.3 Modelica equation
Modelica is equation-based language. From Figure 2 this can be seen that the connection s-
tatements are in equation section. The equations in equation section can help increase reusability
of model components, since components adapt to the data flow context in which they are used.[2]
Without value assignment statements but the equations, the system allows acausal modeling high
level specification and increased correctness. For complex systems, equation-based statements can
not only be easily implemented but clearly.[7]
Some work can be more convenient in Modelica, for exmaple, PDE(Partial Different Equations)
Models, since Modelica is equation-baed.[8]
3 Vehicle Dynamics library
Modelica can import libraries to model some specific model.[9, 10]Vehicle Dynamics library is
designed to model physical state of vehicle motion. This way to extend the Modelica environment
is using by many people who wants to model more.[11]
3
International Journal of Multimedia and Ubiquitous Engineering
Vol. 8, No. 3, May, 2013