Controlling My ROS 2 Omni-Wheeled Robot: Need Help with ros2_control and Communication

Question

I embarked on a final year project to build a robot powered by ROS 2, despite my initial lack of familiarity with the framework. I'm inspired by the TurtleBot and plan to incorporate ROS 2 Navigation 2 (nav2) and other autonomous navigation features into my robot's design. The robot features triple omni wheels, which presented a challenge. I couldn't find existing URDF files online that matched my wheel configuration, and I lack the expertise to create them myself.

To begin, I decided to set up ROS 2 on a Raspberry Pi and Arduino Mega for my robot. My goal was to establish basic control using a joystick. However, I hit another roadblock. I couldn't find any ros2_control demo packages or examples that matched my wheel configuration.

My question is whether there's a straightforward approach for sending X and Y speed variables from the Raspberry Pi to the Arduino and receiving position coordinates (calculated by the Arduino using encoder values) in return. Alternatively, I'm open to suggestions for a simpler and more effective way to control my robot in this configuration.

Answer 1

The very first entry after a google search point to this repository. It is written for ROS 1, but you can maybe directly use/adapt the URDF. If you are not familiar with this, have a look at the vast amount of URDF tutorials and tools like phobos etc.

I fear that there doesn't exist a ros2_controller matching your setup. You could write a new plugin using the steering controller library, we are happy for your contribution to ros2_control.

Start with getting familiar of the forward and inverse kinematics of your robot, e.g

• https://physics.stackexchange.com/questions/679888/kinematics-of-a-3-wheeled-omnidirectional-robot
• https://www.scirp.org/journal/paperinformation.aspx?paperid=102349
• or any other of the ressources found on google.

Then create a new controller plugin, maybe by copying the tricycle controller as a starting point. There you have to implement the kinematics from above etc.

Answer 2

I developed a simulation environment to 3-wheeled omnidirectional robot as as a project for my master's degree. Take a look in the axebot repository. The URDF is in the axebot_description package. Additionally, I created based on the diff_drive_controller my own omnidirectional_controller. Take a look in the Omnidirectional Robot Kinematics and Odometry which explain the application of the forward and inverse kinematics for the 3-wheeled omnidirectional robot that I worked.

I think that these resources may guide you to develop a simulation environment to your robot. However, to control the real robot, you will also need to create a hardware component.