FMI export with OpenModelica

estim8 uses models distributed as Functional Mock-up Units (FMUs) and executes them via the FMPy library. Any tool that exports FMI 2.0-compliant FMUs can be used; OpenModelica is the recommended open-source option.

FMU compilation

1. Download OpenModelica and follow the installation instructions

2. Open OMEdit

3. Load a Modelica class via File → Open Model/Library File(s), or implement a new one

   

4. Optional: For CoSimulation, open Tools → Options → FMI and set the solver to CVODE

   

5. Right-click the model class in the model browser and select Export → FMU

   

Alternatively, compilation can be scripted with OMPython:

from OMPython import ModelicaSystem

model = ModelicaSystem("MyModel.mo", "MyModel")
model.convertMo2Fmu()   # writes MyModel.fmu to the working directory

Important

FMUs are platform-specific. An FMU contains compiled native binaries (e.g. binaries/linux64/MyModel.so on Linux, binaries/win64/MyModel.dll on Windows). An FMU compiled on one operating system will not run on another.

Always compile the FMU on — or for — the platform where parameter estimation will be executed. When running on a compute cluster or inside a container, compile the FMU in the same environment.

Using the FMU in estim8

Pass the path to the compiled FMU to FmuModel:

from estim8 import FmuModel

model = FmuModel(
    path="MyModel.fmu",
    fmi_type="ModelExchange",   # or "CoSimulation"
    default_parameters={"k": 1.0},
)

Both the ModelExchange and CoSimulation FMI interfaces are supported. ModelExchange integrates the model equations directly using a Python-side ODE solver, while CoSimulation delegates time integration to the solver embedded in the FMU.