freedyn 1.0.0

Python bindings for FreeDyn Multi-Body System (MBS) simulator - Windows only

FreeDyn

Multi-Body System (MBS) Simulation and Analysis Software

What is FreeDyn?

FreeDyn is a powerful simulation software for modeling and analyzing Multi-Body Systems (MBS). It supports:

• Rigid and flexible body dynamics with arbitrary kinematic structures
• Advanced constraint modeling (joints, contact, etc.)
• Multiple force models (springs, dampers, external forces, etc.)
• HHT time integration solver for implicit integration
• Python/MATLAB/Scilab interfaces for custom analysis
• GUI and command-line tools for pre- and post-processing

Documentation

• Getting Started - Installation and first steps
• Examples - Code examples and tutorials
• Release Notes - What's new

Quick Start (Python)

1. Install from the extracted release directory:

pip install .

2. Run a model from the CLI:

freedyn-run path/to/model.fds

3. Or script it:

import freedyn as fd

fd.initialize()  # loads freedyn.dll
with fd.Model("path/to/model.fds") as model:
   model.solve()
   for idx, time, states in model.iterate_time_steps():
      print(idx, time, states["Q"][0, 0])

More detail: docs/GETTING_STARTED.md

Features

Simulation Capabilities

• Kinematic and dynamic analysis
• Time-domain simulation with implicit integration
• Automatic constraint handling
• Flexible body dynamics
• Contact models

Analysis Tools

• Jacobian extraction - System matrices at any time point
• Force/motion analysis - Extract forces, accelerations, constraint forces
• Parameter sensitivity - Analytical jacobians w.r.t. parameters
• Custom measures - User-defined outputs

Integration Options

• Python API - Programmatic simulation and analysis
• MATLAB interface - Integration with MATLAB workflows
• Scilab interface - Open-source alternative to MATLAB
• C interface (CDLL) - Direct DLL linking for other languages

Architecture

FreeDyn consists of several core components:

• freedyn.dll - C-interface Dynamic Link Library (core solver)
• Python bindings - High-level API (Model, ModelInfo, analysis functions)
• CLI tool - Command-line interface (freedyn-run)
• GUI/CLI tools - Pre- and post-processing

Requirements

Runtime

• Windows (tested on Windows 7, 10, 11)
• Visual C++ Redistributable (included in release)
• Intel MKL library (included in release)

Development (for bindings)

• Python 3.8+
• numpy
• scipy

License

FreeDyn is released under the GNU Lesser General Public License v3.

See LICENSE for details.

Support & Issues

• GitHub Issues: Report bugs
• Documentation: See docs/ folder
• Examples: See examples/ folder

Release Notes

Latest Release

• Initial public release
• Complete Python bindings refactoring
• High-level API (Model, ModelInfo, analysis functions)
• Command-line tool (freedyn-run)
• Core MBS simulation capabilities
• Matrix/vector extraction functionality
• Comprehensive documentation

Contributing

To contribute to FreeDyn, please:

1. Check existing issues
2. Follow the coding guidelines
3. Submit pull requests with clear descriptions

Citation

If you use FreeDyn in your research, please cite:

@software{freedyn2025,
  title = {FreeDyn: Multi-Body System Simulation Software},
  author = {Oberpeilsteiner, Stefan and others},
  year = {2025},
  url = {https://github.com/freedyn-org/freedyn}
}

Author

Stefan Oberpeilsteiner (FreeDyn Development Team)

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Repository: https://github.com/freedyn-org/freedyn
Version: See _version.py for current version