FMI/FMU co-simulation toolbox for PathSim

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PathSim-FMI extends the PathSim simulation framework with block wrappers around the Functional Mock-up Interface (FMI 2.0 / 3.0). Drop an .fmu file into a PathSim simulation as either a co-simulation slave or as a model-exchange system driven by PathSim's own integrators. Built on top of FMPy.

Blocks

Block	Description	Key Parameters
CoSimulationFMU	Wrap a Co-Simulation FMU, advanced on a fixed grid dt via fmi*DoStep	fmu_path, dt, start_values
ModelExchangeFMU	Wrap a Model-Exchange FMU, integrated by PathSim's solver of choice	fmu_path, start_values

Both blocks build on FMUWrapper, a lower-level version-agnostic wrapper around FMPy (FMI 2.0 / 3.0) that you can use directly if you need finer control than the block API offers.

Install

pip install pathsim-fmi

In the PathView web app: install fails on purpose (the FMU runtime needs to load a native binary via ctypes, which Pyodide can't provide). Use the standalone PathView desktop app or any local Python environment.

Quick Example

from pathsim import Simulation, Connection
from pathsim.blocks import Scope
from pathsim_fmi import ModelExchangeFMU

fmu = ModelExchangeFMU("VanDerPol.fmu")
sco = Scope(labels=["x0", "x1"], sampling_period=0.02)

sim = Simulation(
    blocks=[fmu, sco],
    connections=[
        Connection(fmu[0], sco[0]),
        Connection(fmu[1], sco[1]),
    ],
    dt=0.01,
)
sim.run(5.0)
sco.plot()

Development

pip install -e ".[test]" fmpy ruff mypy
ruff check src/ tests/      # lint
ruff format src/ tests/     # format
mypy src/pathsim_fmi        # type check
pytest tests/ -v            # run tests

The test suite uses the official Modelica Reference-FMUs under tests/data/reference/ for portable smoke tests, plus a handful of legacy FMUs (under tests/data/) carried over from pathsim-core. The legacy FMUs ship darwin64 binaries that are x86_64 only, so the corresponding tests are auto-skipped on Apple Silicon; CI on Linux runs the full suite.

License

MIT