FlexiForce: EMG-Driven Robotic Resistance Training Simulator

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Overview

FlexiForce simulates a personalized fitness and rehabilitation system where a redundant robotic arm (Franka Emika FP3) dynamically adjusts resistance based on real-time EMG data. Using MuJoCo for robotic simulation and OpenSim for muscle modeling, it implements a hybrid force-position controller that modulates end-effector resistance to keep user exertion aligned with a target % of max voluntary contraction.

Key Highlights:

• GUI for user-defined effort
• Real-time EMG feedback
• Redundant robot arm simulation
• Modular controllers for benchmarking

Features

• Closed-loop EMG feedback control
• Real-time GUI-based effort input
• Force-position hybrid control architecture
• Support for both OpenSim and custom muscle models
• Performance-optimized simulation in MuJoCo

Architecture

[ GUI Input (Target Effort) ] 
        ↓ 
[ Controller: Hybrid Force-Position ]
        ↓
[ MuJoCo Robot Arm ] ←→ [ OpenSim / EMG Model ]
        ↑                            ↓
    [ Force Output ] ←── Feedback Loop ──→ [ EMG Activation ]

Installation

1. Clone the Repository

git clone --recurse-submodules https://github.com/aaronjohnsabu1999/flexiforce.git
cd flexiforce

If you forgot --recurse-submodules:

git submodule update --init --recursive

2. Create a Virtual Environment (Recommended)

python -m venv venv

Activate it:

• macOS/Linux: source venv/bin/activate
• Windows: venv\Scripts\activate

3. Install Dependencies

pip install -r requirements.txt

On Linux:

sudo apt update && sudo apt install -y python3-tk

On Windows:

Tkinter is bundled with Python. To check:

python -m tkinter

🐧 WSL2 Setup Instructions (Ubuntu/Debian)

Step 1: Install Required Packages

sudo apt update
sudo apt install -y python3-tk libgl1-mesa-glx libglu1-mesa mesa-utils

Step 2: Launch X Server on Windows

Install and start VcXsrv:

• ✅ Multiple windows
• ✅ Start no client
• ✅ Disable access control
• 🔁 Try both with/without Native OpenGL

Step 3: Export Display Settings

In ~/.bashrc or before running:

export DISPLAY=:0
export LIBGL_ALWAYS_INDIRECT=0

Reload with:

source ~/.bashrc

Step 4: Test with glxgears

glxgears

If gears spin, OpenGL is working.

Step 5: Run the Simulation

python3 main.py

• ✅ GUI will open via Tkinter
• ✅ MuJoCo viewer will render (if OpenGL works)
• 🔁 Headless fallback if viewer fails

Troubleshooting

• No MuJoCo viewer? Ensure VcXsrv is running and DISPLAY is set.
• OpenGL errors? Try export LIBGL_ALWAYS_INDIRECT=1
• Still broken? Run in native Windows with Python + MuJoCo setup.

License

MIT License. See LICENSE.md.

Authors

• Ben Forbes
• Samantha Herman
• Aaron John Sabu

Course project for MAE 263C – University of California, Los Angeles

License

MIT License. See LICENSE.md for details.

Acknowledgments

• Dr. Veronica Santos – MAE 263C
• OpenSim and MuJoCo dev teams
• Everyone who tolerates noisy EMG data and still finds signal in the chaos