Capabilities and limitations

This section deals with capabilities that are common to the Model Exchange and Co-simulation import.

The FMI 1.0, 2.0, and 3.0 specifications define rules and limitations about the content of the XML Model Description File. In addition to these rules, the Import Tool has some known limitations:

• Scalar variables of type "String" with variability other than "Parameter" are not supported. This means that Simcenter Amesim does not support input, output or discrete state variables of type string.

• Enumeration-type, Boolean-type and integer-type variables are partially supported as double variables. This means that these variables are cast to or from double each time the import submodel needs to access these variables. This restriction only applies to variables, not parameters since Simcenter Amesim only support double type variables. Enumeration, Boolean and integer parameters are fully supported as such by Simcenter Amesim.

• Source-only FMUs are not supported, since there is no standard way to build the binary part of an FMU from its sources.

• The debug logging status cannot be changed during simulation, it can be selected only once before the beginning of simulation.

For FMI version 1.0, the following specific rules are also applied:

• A scalar variable with variability "Parameter" cannot be an alias of another scalar variable with variability "Parameter", since this situation creates a non-deterministic assignment of the parameter value.

• A scalar variable cannot have more than one start value through its aliases, since it creates a non-deterministic initialization sequence.

• A scalar variable with causality "Input" cannot be an alias of another scalar variable with causality "Input" to avoid non-determinism in model evaluation.

• Scalar variables with variability "Constant" and causality "Input" are forbidden.

If the Import Tool encounters one of these limitations in the XML Model Description File, it reports an error message and stops the import process.

Note

For FMI version 3.0, the following limitations apply:

• Variable aliases are ignored

• Optional terminals are ignored; This means that each variable with input or output causality is wrapped into one signal-type port

• Configuration and re-configuration modes are not supported; This means that structural parameters cannot be changed and therefore the size of array variables is fixed

• Binary-type variables are not supported and are therefore ignored

In addition to these unsupported features, some other features are simply ignored. A warning message is simply reported and the import process is carried on:

• Display units declared in the FMU are ignored, since the choice of a display unit is made at model level or at application level in Parameter or Simulation mode, but not at submodel level.

• Vendor annotations are ignored.

• Default experiments are ignored, since this is only meaningful for a full assembled model.

Note

It is always possible to use several different imported FMU on the same Simcenter Amesim sketch.