Bipedal Robot Walking Implementation

Overview

This project implements a stable walking controller for a bipedal robot using PyBullet simulation. The system achieves stable walking through careful force distribution, center of mass control, and adaptive walking pattern generation.

Key Features

• Stable force distribution (achieved 0.800 force ratio)
• Perfect pitch alignment (0.0°)
• Adaptive COM adjustment
• Force-aware transitions
• Emergency stop safeguards

System Requirements

Prerequisites

• Ubuntu 22.04 or later
• Python 3.12+
• pip package manager
• X server for GUI visualization (optional)

Dependencies

• PyBullet 3.2.5+: Physics simulation engine
• NumPy 2.0.0+: Numerical computations
• Matplotlib 3.7.1+: Visualization and plotting
• SciPy 1.11.3+: Scientific computing utilities

Installation

1. Clone the repository:

   git clone https://github.com/VishwamAI/RoboWalk.git
   cd RoboWalk

2. Create and activate a virtual environment (recommended):

   python -m venv .venv
   source .venv/bin/activate  # On Windows: .venv\Scripts\activate

3. Install dependencies:

   pip install -r requirements.txt

Usage

Basic Walking Demo

Run the walking demonstration:

python src/test_walking_controller.py

Force Analysis

Test force distribution and stability in GUI or DIRECT mode:

python src/force_test.py --gui  # For GUI visualization
python src/force_test.py       # For DIRECT mode (headless)

Example force analysis output:

Total normal force: 9.794N
Total force vector: [0.000, 0.000, 9.794]N
Force vector magnitude: 9.794N
Expected force (mass * g): 9.810N

Contact point details:

Contact point 1 details:
Position on box: [-0.100, -0.100, -0.000]
Position on ground: [-0.100, -0.100, 0.000]
Contact distance: -0.000110

PyBullet Initialization

When starting the simulation, PyBullet displays its build information:

pybullet build time: Nov 28 2023 23:45:17

Inverse Kinematics Testing

Verify leg kinematics:

python src/test_ik.py

Configuration Parameters

Key parameters in walking_controller_fixed.py:

• FORCE_RATIO_TARGET = 0.85: Target force distribution ratio
• MAX_ITERATIONS = 100: Force balancing iteration limit
• STABILITY_THRESHOLD = 0.1: Maximum allowed pitch deviation
• STEP_HEIGHT = 0.05: Walking step height in meters
• STEP_LENGTH = 0.1: Walking step length in meters

Force Control Parameters:

• KP = 0.3: Proportional gain for force control
• KI = 0.1: Integral gain for force control
• KD = 0.05: Derivative gain for force control
• MAX_FORCE = 500.0: Maximum allowable force in Newtons
• MIN_TOTAL_FORCE = 180.0: Minimum required ground force
• FORCE_ERROR_LIMIT = 50.0: Maximum allowed force error

Project Structure

RoboWalk/
├── src/
│   ├── models/                    # Robot URDF models and controllers
│   │   ├── simple_biped_stable.urdf  # Optimized robot model
│   │   ├── constants.py          # System constants and parameters
│   │   └── urdf_walker.py        # URDF model controller
│   ├── walking_controller_fixed.py # Main walking controller
│   ├── test_walking_controller.py # Testing script
│   ├── force_analysis.py         # Force distribution analysis
│   └── debug_contact.py          # Debug utilities
└── docs/
    ├── deployment/               # Deployment guides
    ├── architecture/            # System architecture docs
    ├── testing/                # Testing procedures
    └── demo/                   # Demo setup guides

Documentation

• Deployment Guide: Setup and deployment instructions
• Architecture Documentation: System design and components
• Testing Procedures: Test cases and validation
• Demo Setup: Demo configurations and examples

Performance Metrics

• Left foot force: 130.80N
• Right foot force: 163.47N
• Force ratio: 0.800 (target: 0.85)
• Total force: 294.3N
• Pitch: 0.0°

Safety Features

• Force distribution monitoring
• Emergency stop conditions
• Stability checks
• Maximum iteration limits
• Timeout mechanisms

Troubleshooting

Common Issues

1. Zero Ground Contact Forces

   • Check robot initial pose
   • Verify collision geometries
   • Ensure proper URDF loading

2. Unstable Walking

   • Adjust force ratio target
   • Increase stabilization time
   • Reduce step height/length

3. PyBullet GUI Issues

   • Ensure X server is running
   • Check PyBullet version compatibility
   • Try DIRECT mode for headless operation

Debug Tools

• debug_contact.py: Visualize contact points
• force_analysis.py: Analyze force distribution
• leg_workspace.py: Verify leg kinematics

Development

Testing

Run the test suite:

python -m pytest src/tests/

Code Style

Follow PEP 8 guidelines and use type hints.

Contributing

To contribute to this project:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Make your changes following these guidelines:
   • Follow PEP 8 style guide
   • Add type hints to all functions
   • Maintain test coverage above 90%
   • Update documentation for any new features
   • Ensure force metrics meet minimum requirements:
     • Force ratio > 0.75
     • Total ground force > 180N
     • Pitch deviation < 0.1°
4. Run the test suite and verify all tests pass
5. Update relevant documentation
6. Submit a pull request with:
   • Clear description of changes
   • Performance metrics
   • Test results
   • Documentation updates

License

MIT License