2D-Drone: Open-Source Mobile Robot from the SwissCAT+ Lab

Open-source mobile robot for laboratory automation and SBS plate handling.

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Table of Contents

1. Overview
2. System Architecture
3. Deployment of a New Robot
4. Docker Installation (recommended)
5. Local Installation (advanced)
6. How to Run
7. ROS 2 Interfaces
8. Project Structure
9. Improvements & Roadmap
10. License

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Overview

The Swiss CAT+ 2D-drone is an open-source mobile robot platform developed at the SwissCAT+ laboratory for laboratory automation.

Built to transport SBS-format plates along a dedicated track on top of the lab, the 2D-drone provides a robust foundation for developing and deploying modular, automated workflows in research and production environments.

The robot localizes itself using a top-mounted camera that detects a network of ArUco markers placed above the track, enabling precise and repeatable navigation without external localization systems.

The EM_fleetmanager coordinates multiple 2D-Drones, manages map and marker deployment, and ensures synchronized operation across the SwissCAT+ laboratory.

A markerless visual SLAM module is currently in development and will extend the 2D-Drone’s capabilities beyond track-based navigation to more general indoor environments in upcoming releases.

The EM_onrobot repository contains the complete software and hardware resources required to build, configure, and deploy the 2D-Drone

Software

• Controls the two DYNAMIXEL XC430-W150 differential-drive motors.
• Reads and compute encoder odometry directly through the Dynamixel SDK.
• Collects IMU data from the Bosch BNO055 sensor.
• Runs an Extended Kalman Filter (EKF) to fuse IMU and wheel odometry.
• Uses the camera with ArUco markers for drift correction in odometry (map correction).
• Publishes ROS 2 topics for robot localization and subscribes to /cmd_vel for motion commands.

Hardware

• Includes the 3D-printable mechanical design of the robot’s case (recommended material: PLA) :
  • EdyMobileAssembly contains the full CAD for SolidWorks
  • EdyMobileURDFAssembly contains the CAD ready for URDF export
  • EdyMobile_URDF_screencast_ROS contains the URDF
  • Edymobile_STL_And_BambuPrintables contains the STL files and a read-to-print file for bamboo lab PS1
• Provides the electrical schematics for wiring and integration.

Deployment

• Supports containerized deployment with Docker for easy setup and reproducibility.

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Versions & Software

• OS: Ubuntu 22.04 (on Raspberry Pi OS 64-bit for Raspberry Pi 5)
• ROS 2: Humble
• Docker image (recommended):

  ghcr.io/swisscatplus/em_onrobot/em_robot:latest
  

• Dependencies (local runs): see Local Installation

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System Architecture

• Hardware

  • Raspberry Pi 5
  • 2x DYNAMIXEL Motors (XC430-W150)
  • DYNAMIXEL U2D2 Power Hub
  • DYNAMIXEL U2D2
  • 2x Pololu Scooter/Skate Wheel 70×25mm - Black (3272)
  • Bosch BNO055 IMU Adafruit Board (2472)
  • Raspberry Pi Camera Module 3 Wide
  • Bosch Professional GBA 18V (5AH recommended)
  • Converter DC/DC to 5V (DTJ1524S05)
  • Converter DC/DC to 12V (DTJ1524S12)
  • 3D printed Mobile Robot Case

• Software

  • OS installed on the RPi5 (recommended : Raspberry pi OS using Imager software)
  • ROS 2 packages (all inside Docker):
    • em_robot → motor control and odometry
    • bno055 → IMU driver (The src/bno055 package in this repository is a modified version of the original flynneva/bno055 code, adapted to work with this application.)
    • em_robot_srv → service definitions

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Deployment of a New Robot

Hardware Setup

• Mount and wire the robot according to the CAD and Electrical Schematics
• Insert the fully charged battery into the back holder
• Wait some time for the Raspberry Pi to initialize
• Place the RPi within Wi-Fi range.

Networking

• Ensure PC and RPi are on the same network.
• For that, configure a static IP on the RPi which should be the same as the one found in fastdds.xml (for example : 192.168.0.101)
• Match the ROS_DOMAIN_ID on both PC and RPi (default = 10):

  echo "export ROS_DOMAIN_ID=10" >> ~/.bashrc

  Or in the Dockerfile:

  ENV ROS_DOMAIN_ID=10

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Docker Installation (recommended)

1. SSH into the RPi:

   ssh <rpi-name>@<robot-ip>

2. Install Docker on the RPi:

   sudo apt-get update
   sudo apt-get install ca-certificates curl gnupg
   sudo install -m 0755 -d /etc/apt/keyrings
   curl -fsSL https://download.docker.com/linux/debian/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
   sudo chmod a+r /etc/apt/keyrings/docker.gpg
   
   echo      "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/debian      $(. /etc/os-release && echo "$VERSION_CODENAME") stable" |      sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
   
   sudo apt-get update
   sudo apt-get install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
   sudo groupadd docker
   sudo gpasswd -a $USER docker
   newgrp docker
   docker run hello-world

3. Pull the container image:

   docker pull ghcr.io/swisscatplus/em_onrobot/em_robot:latest

4. Run the container:

   ./deploy.sh

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Local Installation (advanced)

Running outside Docker is not the primary workflow, but it is possible.
From the Dockerfile, the required local dependencies are:

System packages

sudo apt update
sudo apt install python3-smbus i2c-tools python3-dev

Python packages

pip install smbus2

ROS 2 packages

Make sure you have ROS 2 Humble installed with colcon and build tools.
Then build the workspace:

cd ros2_ws
colcon build --packages-select em_robot em_robot_srv bno055

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How to Run

1. Connect to the RPi:

   ssh <rpi-name>>@<robot-ip>

2. Start the container:

   ./deploy.sh

3. Test movement:

   Important: This is a two-wheeled differential drive robot. That means it can only move using:

   • Linear X → forward/backward motion (both wheels turning in the same direction).
   • Angular Z (yaw) → rotation on the spot or turning (wheels turning at different speeds).

   All other fields (linear.y, linear.z, angular.x, angular.y) are ignored.

   You have two options for testing:

   • Direct velocity commands (use with caution):

     You can publish a velocity command directly, but be aware that the robot will keep moving until you explicitly send another command with zero velocity. For example:

     ros2 topic pub /cmd_vel geometry_msgs/Twist "linear:
       x: 0.3
       y: 0.0
       z: 0.0
     angular:
       x: 0.0
       y: 0.0
       z: 0.5"

     To stop the robot, send the same command again but with all values set to 0.0.

   • Safer option: use teleop:

     The recommended way to test is to use the teleop_twist_keyboard package. This allows you to control the robot interactively from your PC with the keyboard:

     ros2 run teleop_twist_keyboard teleop_twist_keyboard

     You can also connect a gaming controller and map the joystick to publish commands on /cmd_vel for smoother and safer manual control.

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ROS 2 Interfaces

Topics

Topic	Type	Description
/left_ticks_counts	std_msgs/Int16	Encoder ticks from left wheel
/right_ticks_counts	std_msgs/Int16	Encoder ticks from right wheel
/bno055/imu	sensor_msgs/Imu	Orientation and acceleration from BNO055
/edi/cam	geometry_msgs/PoseWithCovarianceStamped	Pose correction from camera + ArUco markers
/cmd_vel	geometry_msgs/Twist	Input velocity command for differential drive

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Project Structure

EM_onrobot/
├── Dockerfile            # Build instructions for em_robot image
├── Dockerfile.base       # Base image with ROS 2 and dependencies
├── entrypoint.sh         # Container entrypoint script
├── fastdds.xml           # Fast DDS configuration
├── src/
│   ├── em_robot/         # Main robot package (motors, camera, odometry)
│   ├── em_robot_srv/     # ROS 2 service definitions
│   ├── bno055/           # External Bosch BNO055 driver
│   └── test.py           # Example script
├── images/logo.png
└── README.md

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Improvements & Roadmap

• Expand documentation with troubleshooting and advanced usage examples.

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License

This project is licensed under the MIT License.

It also includes code from flynneva/bno055, which is licensed under the BSD 3-Clause License.