🚶‍♂️ GaitSim Assist: A Python Library for Gait Simulations and Assistive Device Design

GaitSim Assist is a comprehensive Python library for biomechanics researchers and wearable device engineers. It provides a high-level API for running gait simulations, testing assistive device parameters, and optimizing cost function settings without deep diving into low-level OpenSim code.

🌟 Features

• Unified Gait Simulation API: High-level Python APIs to load gait datasets, run simulations (tracking or predictive), and retrieve joint kinematics & kinetics results.
• Cost Function Modules: Built-in library of cost functions (metabolic cost, fatigue, effort, etc.) that can be swapped or combined to see how assistive outcomes change.
• Assistive Device Modeling: Tools to model simple assistive device effects (like exoskeleton torques or prosthetic joint limits) and incorporate them into simulations.
• Visualization & Analysis: Automatic generation of gait plots – joint angle curves, ground reaction forces, muscle activations – for both experimental and synthetic gait data.

📋 Installation

Using pip

pip install gaitsim-assist

From source

git clone https://github.com/yourusername/gaitsim-assist.git
cd gaitsim-assist
pip install -e .

Dependencies

GaitSim Assist requires:

• Python 3.9+
• OpenSim 4.3+
• NumPy, Matplotlib, Pandas, SciPy
• CasADi (for optimization)

🚀 Quick Start

Basic Simulation

import gaitsim_assist as gsa

# Create a simulator with default 2D walking model
simulator = gsa.GaitSimulator()

# Run a predictive simulation with cost of transport cost function
results = simulator.run_predictive_simulation(
    cost_function='cot',
    time_range=(0.0, 1.0)
)

# Visualize the results
from gaitsim_assist.visualization import GaitPlotter
plotter = GaitPlotter()
plotter.plot_joint_angles(results)
plotter.plot_ground_forces(results)

Example Scripts

We provide several example scripts in the examples/ directory:

• basic_simulation_moco.py: Run a simple walking simulation using OpenSim Moco
• compare_cost_functions.py: Compare different cost functions (muscle effort, joint torque, hybrid)
• analyze_opensim_results.py: Analyze and visualize existing OpenSim simulation results
• batch_processing.py: Run multiple simulations with different parameters
• assistive_device_optimization.py: Optimize assistive device parameters
• custom_cost_function.py: Create and use custom cost functions

To run an example:

cd examples
python basic_simulation_moco.py

Adding an Assistive Device

# Create an ankle exoskeleton
exo = gsa.devices.Exoskeleton(
    name="ankle_exo",
    model=simulator.model,
    joint_name="ankle",
    mass=1.0,
    max_torque=50.0
)

# Run simulation with the exoskeleton
exo_results = simulator.run_predictive_simulation(
    cost_function='cot',
    time_range=(0.0, 1.0),
    assistive_device=exo
)

Comparing Different Cost Functions

# Create a hybrid cost function
hybrid_cost = gsa.cost_functions.Hybrid(
    simulator.model,
    cost_functions={
        'cot': 0.5,
        'muscle_effort': 0.5
    }
)

# Run simulation with the hybrid cost function
hybrid_results = simulator.run_predictive_simulation(
    cost_function=hybrid_cost,
    time_range=(0.0, 1.0)
)

# Compare results
plotter.compare_simulations(
    results_list=[results, exo_results, hybrid_results],
    labels=["Baseline", "Exoskeleton", "Hybrid Cost"],
    plot_type="joint_angles"
)

📊 Example Visualizations

Joint Angles

Detailed view of joint angles for hip, knee, and ankle joints throughout the gait cycle.

Ground Reaction Forces

Ground reaction forces showing both vertical and anterior-posterior components during walking.

Muscle Activations

Muscle activation patterns during the gait cycle, showing the timing and magnitude of major muscle group activations during walking.

📚 Documentation

For full documentation, visit docs.gaitsim-assist.org.

Tutorials

• Getting Started
• Creating Custom Cost Functions
• Modeling Assistive Devices
• Analyzing Simulation Results

🛠 Project Structure

gaitsim_assist/
├── __init__.py
├── simulation/           # Core simulation capabilities
│   ├── __init__.py
│   ├── gait_simulator.py
│   ├── tracking.py
│   └── predictive.py
├── cost_functions/       # Cost function implementations
│   ├── __init__.py
│   ├── base.py
│   ├── cot.py
│   ├── muscle_effort.py
│   └── ...
├── devices/              # Assistive device models
│   ├── __init__.py
│   ├── base.py
│   ├── exoskeleton.py
│   └── ...
├── visualization/        # Visualization tools
│   ├── __init__.py
│   ├── gait_plotter.py
│   └── ...
└── analysis/             # Analysis tools
    ├── __init__.py
    └── ...

🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• OpenSim community for their excellent tools and documentation
• Contributors to the biomechanics research community