Mobile Differential Drive Robot - SLAM Project

A ROS 2 workspace for 3D SLAM using RTABMap with a 6-wheel differential drive robot equipped with Intel RealSense D455 camera.

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Overview

This project implements RGB-D SLAM (Simultaneous Localization and Mapping) using RTABMap on a custom differential drive robot. The robot can build 3D maps of indoor environments and localize itself within those maps.

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Robot Specifications

Hardware

• Type: 6-wheel differential drive robot
• Camera: Intel RealSense D455 (RGBD)
• Sensors: Wheel odometry, depth camera

Software Stack

• ROS 2: Humble Hawksbill
• SLAM: RTABMap 0.22.1
• Simulation: Gazebo 11
• Visualization: RViz2, RTABMap Viz

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Quick Start

Prerequisites

# ROS 2 Humble
sudo apt install ros-humble-desktop

# RTABMap
sudo apt install ros-humble-rtabmap-ros

# Gazebo
sudo apt install gazebo libgazebo-dev

# TurtleBot3 Gazebo ( for worlds )
sudo apt install ros-humble-turtlebot3-gazebo

# Additional dependencies
sudo apt install ros-humble-robot-state-publisher
sudo apt install ros-humble-xacro

Installation

1. Clone the repository

git clone <repo-url>
cd ws_ddmobile

2. Build the workspace

colcon build --symlink-install

3. Source the workspace

source install/setup.bash

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Usage

SLAM Mode (Mapping)

Launch SLAM mode to build a new map:

# Launch Gazebo, RTABMap SLAM, and RTABMap Viz
ros2 launch mobile_dd_robot rtabmap_slam_robust.launch.py

# Launch RViz2 separately
cd ws_ddmobile
source install/setup.bash
rviz2 -d src/mobile_dd_robot/config/rtabmap.rviz

Localization Mode (Navigation)

Launch localization mode to use a pre-built map:

# Launch Gazebo, RTABMap Localization, and RTABMap Viz
ros2 launch mobile_dd_robot rtabmap_localization.launch.py

# Launch RViz2
cd ws_ddmobile
source install/setup.bash
rviz2 -d src/mobile_dd_robot/config/rtabmap.rviz

Driving the Robot

Use keyboard teleop to drive the robot:

# Terminal 3: Keyboard control
ros2 run teleop_twist_keyboard teleop_twist_keyboard

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Package Structure

ws_ddmobile/
├── src/
│   └── mobile_dd_robot/
│       ├── launch/
│       │   ├── rtabmap_slam_robust.launch.py      # SLAM mode
│       │   └── rtabmap_localization.launch.py     # Localization mode
│       ├── model/
│       │   ├── robot_with_camera.xacro            # Robot URDF
│       │   ├── robot.gazebo                       # Gazebo plugins
│       │   └── camera.xacro                       # Camera model
│       ├── config/
│       │   └── rtabmap.rviz                       # RViz configuration
│       ├── CMakeLists.txt
│       └── package.xml
├── build/              (gitignored - build artifacts)
├── install/            (gitignored - install files)
├── log/                (gitignored - build logs)
└── README.md

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Configuration

RTABMap Parameters

The launch files include optimized RTABMap parameters for robust SLAM:

Key Parameters

• Grid Resolution: 5cm cells for occupancy grid
• Feature Detection: GFTT (Good Features To Track) with 1200 features
• Loop Closure: Threshold 0.10 for moderate-aggressive detection
• Ground Filtering: Points below -10cm filtered out
• Optimization: 30 iterations with g2o optimizer

Parameter Highlights

'Grid/CellSize': '0.05'                    # 5cm resolution
'Grid/MinGroundHeight': '-0.1'             # Filter underground artifacts
'Grid/MaxGroundHeight': '0.05'             # Ground detection
'Vis/MaxFeatures': '1200'                  # Visual features
'Rtabmap/LoopThr': '0.10'                  # Loop closure threshold
'Optimizer/Iterations': '30'               # Graph optimization
'RGBD/OptimizeMaxError': '3.0'             # Max optimization error

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Testing

Verify Installation

# Check if RTABMap is installed
ros2 pkg list | grep rtabmap

Run System Tests

1. Launch SLAM mode
2. Drive robot for 2-3 minutes
3. Check map is being built in RTABMap Viz
4. Verify occupancy grid in RViz2
5. Look for loop closures in console

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Building

cd ws_ddmobile
colcon build --symlink-install

Testing Changes

# Rebuild single package
colcon build --symlink-install --packages-select mobile_dd_robot

# Source and test
source install/setup.bash
ros2 launch mobile_dd_robot rtabmap_slam_robust.launch.py

Adding New Features

1. Modify launch files in src/mobile_dd_robot/launch/
2. Update robot model in src/mobile_dd_robot/model/
3. Rebuild: colcon build --symlink-install
4. Test in simulation

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ROS 2 Topics

Published Topics

• /odom - Wheel odometry
• /camera/d455/image_raw - RGB image
• /camera/d455/depth/image_raw - Depth image
• /camera/d455/camera_info - Camera calibration
• /camera/d455/points - Point cloud
• /map - Occupancy grid map
• /rtabmap/grid_prob_map - Probability map

Subscribed Topics

• /cmd_vel - Velocity commands for robot control