🚀 ROS 2 Motor Control Progress Log — Week in Review

I’ve finally begun the real-world hardware integration phase of my autonomous rover project. This week marks solid progress on multiple fronts, from hardware wiring to ROS 2 integration and testing.

🛠️ Hardware Setup Complete

The physical platform is now up and running:

  • Chassis: Lynxmotion A4WD3 Rugged Wheeled Rover
  • Motor controller: Single Sabertooth 2x12 motor driver in packetized serial mode
  • Microcontroller: Arduino Mega, interfacing with encoders and Sabertooth
  • Host PC: Laptop running ROS 2 Humble via USB serial

✅ Serial communication, motor control, and encoder feedback have been successfully tested.

🧠 Arduino Firmware

A custom Arduino sketch has been developed which:

  • Receives velocity commands in rad/s from ROS
  • Computes PID control loops for each wheel
  • Drives motors using the Sabertooth serial protocol
  • Samples encoder ticks to calculate wheel velocities

🔧 PID tuning has been challenging — initial values led to slow or unstable responses. Compensation for deadband and better control loop tuning are in progress.

🧪 ROS 2 Integration

A custom ROS 2 node motor_controller_node was implemented in C++ to interface with the Arduino:

  • Subscribes to sensor_msgs/msg/JointState to receive wheel velocity commands
  • Sends those commands to the Arduino via serial
  • Plans underway to publish feedback and diagnostics

A dedicated driver library abstracts the serial protocol, separating logic from ROS-specific code for reusability and testability.

✅ Unit Testing & GitHub Actions

To improve robustness and CI/CD:

  • Unit tests validate packet structure, byte formatting, and checksum logic
  • GitHub Actions run tests and format checks on push
  • Clang-format is enforced using .clang-format and a required status check on the main branch

🧰 Tools & Debugging

  • A standalone serial tool was created to send test commands and receive feedback from the Arduino
  • CuteCom and minicom were used to manually test serial commands and response structure

🔮 Next Steps

  • 🔧 Add configuration interfaces: Expose PID values and other tuning parameters via ROS 2 services
  • 🔩 Hardware mounting: Secure Arduino, Sabertooth, and power system on the Lynxmotion chassis
  • 🧪 Improve PID tuning: Address deadband issues, overshoot, and convergence delay
  • 📡 Feedback publishing: Send total wheel distance from Arduino to ROS

Stay tuned! This project is evolving quickly now that the hardware and communication stack are working.
👉 Check the repo: GitHub - rugged_rover