py-crane 0.3.1

Getting Started

A concrete crane model should consist of an extension of the Crane object,

• defining general model variables like name, author, version, etc.

• defining the anticipated set of booms

• if there is a wish to keep parameters configurable, these can be kept as parameters of the extended model.

• In a separate script, instantiate the concrete crane, test it and run Model.build(…) to make the FMU.

See the file tests/resources/mobile_crane.py and related test files as an example on how a concrete crane can be defined and used.

Installation

pip install py-crane

Usage Example

This is a simple mobile crane, like they are used on e.g. building sites with

• a short pedestal, which can be turn around,

• one boom with variable length and which can be lifted

• one rope, where loads can be attached.

from py_crane.crane import Crane

class MobileCrane(Crane):
    """Simple mobile crane for FMU testing purposes.
    The crane has a short pedestal, one variable-length stiff boom and a rope.
    The size and weight of the various parts can be configured.

    Args:
        name (str) : name of the crane type
        description (str) : short description
        author (str)
        version (str)
        pedestalMass (str) : mass of the pedestal - quantity and unit as string
        pedestalHeight (str) : height (fixed) of the pedestal, with units
        boomMass (str) : mass of the single boom, with units
        boomLength0 (str) : minimum length of the boom, with units
        boomLength1 (str) : maximum length of the boom, with units
    """

    def __init__(
        self,
        name: str = "mobile_crane",
        description: str = "Simple mobile crane (for FMU testing) with short pedestal, one variable-length elevation boom and a rope",
        author: str = "DNV, SEACo project",
        version: str = "0.2",
        pedestalMass: str = "10000.0 kg",
        pedestalHeight: str = "3.0 m",
        boomMass: str = "1000.0 kg",
        boomLength0: str = "8 m",
        boomLength1: str = "50 m",
        rope_mass_range: tuple = ("50kg", "2000 kg"),
        **kwargs,
    ):
        super().__init__(name=name, description=description, author=author, version=version, **kwargs)
        _ = self.add_boom(
            name="pedestal",
            description="The crane base, on one side fixed to the vessel and on the other side the first crane boom is fixed to it. The mass should include all additional items fixed to it, like the operator's cab",
            mass=pedestalMass,
            massCenter=(0.5, -1.0, 0.8),
            boom=(pedestalHeight, "0deg", "0deg"),
            boom_rng=(None, None, ("0deg", "360deg")),
        )
        _ = self.add_boom(
            name="boom",
            description="The boom. Can be lifted and length can change within the given range",
            mass=boomMass,
            massCenter=(0.5, 0, 0),
            boom=(boomLength0, "90deg", "0deg"),
            boom_rng=((boomLength0, boomLength1), (0, "90deg"), None),
        )
        _ = self.add_boom(
            name="rope",
            description="The rope fixed to the last boom. Flexible connection",
            mass="50.0 kg",  # so far basically the hook
            massCenter=0.95,
            mass_rng=rope_mass_range,
            boom=("1e-6 m", "180deg", "0 deg"),
            boom_rng=(
                ("1e-6 m", boomLength1),
                ("90deg", "270deg"),
                ("-180deg", "180deg"),
            ),
            damping=50.0,
            animationLW=2,
        )
        # make sure that _comSub is calculated for all booms:
        self.calc_statics_dynamics(None)

    def do_step(self, currentTime, stepSize):
        status = super().do_step(currentTime, stepSize)
        # print(f"Time {currentTime}, {self.rope_tip}")
        # print(f"MobileCrane.do_step. Status {status}")
        return status

Testing and usage of the MobileCrane.fmu is demonstrated as part of related test_*** files.

Development Setup

powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

curl -LsSf https://astral.sh/uv/install.sh | sh

uv python install

winget install --id Python.Python

git clone https://github.com/dnv-opensource/py-crane path/to/your/dev/py-crane

cd py-crane

uv sync -U

uv run <command>

.venv\Scripts\activate.bat

source .venv/bin/activate

uv run pre-commit install

uv run pre-commit run --all-files

uv run git commit -m <MSG> --no-verify

uv run pre-commit autoupdate

uv run pytest

Meta

Copyright (c) 2025 DNV AS. All rights reserved.

Siegfried Eisinger - @LinkedIn - siegfried.eisinger@dnv.com

Jorge Luis Mendez - @LinkedIn - jorge.luis.mendez@dnv.com

Distributed under the MIT license. See LICENSE for more information.

https://github.com/dnv-opensource/py-crane

Contributing

Anybody in the FMU, OSPand SEACo community is especially welcome to contribute to this code, to make it better, and especially including other features from model assurance and from SEACo issues.

To contribute, follow these steps:

1. Fork it https://github.com/dnv-opensource/py-crane/fork/

2. Create an issue in your GitHub repo

3. Create your branch based on the issue number and type (git checkout -b issue-name)

4. Evaluate and stage the changes you want to commit (git add -i)

5. Commit your changes (git commit -am 'place a descriptive commit message here')

6. Push to the branch (git push origin issue-name)

7. Create a new Pull Request in GitHub

For your contribution, please make sure you follow the STYLEGUIDE before creating the Pull Request.