A Gentle Introduction to ROS2 and Gazebo

The goal of the session is to get a helocopter view of what ROS2 is and how it works. To do that we are going to leverage the official Tutorials and the Gazebo simulation environment. To get get up and running quickly and to avoid installing everything locally we've created a Docker image that has everything we need.

• ROS2 Galactic Geochelone
• Gazebo Simulation Environment
• TurtleBot3 Simulation

TurtleBot is a low-cost, personal robot kit with open-source software. Instead of purchasing expensive hardware to try some things out we are going to simulate a TurtleBot3 instead! The simulator is complete with LIDAR, a camera, a gyro and many other sensors and actuators.

Setup

1. Clone the repository

The first thing we need to do is to clone this repository contaning the tutorial. It contains a Dockerfile that creates an image providing an HTML5 VNC interface to access a Ubuntu LXDE environment. Clone the repository using the following URL

git clone ros2-turtlebot3-sim

Now we need to use git to update the submodules containing the ROS2 tutorials

git submodule update --init --recursive

2. Get the docker image

It is recommended to use the prebuilt image from dockerhub. This is the quickest option and lets you get going now by running the command

docker pull andrewpresland/ros2-turtlebot3-sim:latest

If you have you have time of want to make changes you can build it yourself by navigating to the repositiry directory and running the command

docker build -t turtlebot3 .

3. Run the container

Once the image is built run the container. If you are running on Windows replace $PWD with %cd% for current directory.

docker run --rm -it -v $PWD/workspace:/home/ubuntu/dev_ws -p 6080:80 andrewpresland/ros2-turtlebot3-sim

4. Access the Desktop

When the image has booted go to http://127.0.0.1:6080/ in any browser to be greeted by the VNC desktop goodness.

5. Build some packages

One last thing needs to be done before we can get hands-on with the Tutorials. We need to build some base packages from the source code already installed in the Docker. We just need to open a terminal in VNC desktop (Menu -> System Tools -> LX Terminal) and build the stuff.

Navigate to the ROS2 workspace inside LX Terminal

cd ~/dev_ws

Build and install (ignore the warnings).

colcon build --symlink-install

Tutorials

Now that we have everything setup we are ready to look at the ROS2 Tutorials. These will help you learn about ROS2 with some hands-on exercises. Everything you need should already be installed in the container and you can work through at your own pace. There are a lot of turorials so do not expect to complete them all. We have some resources setup we can come back on another day and continue the fun.

Gazebo Simulation

We have also installed a Gazebo simulation of the Turtlebot3. To run it first setup the environment to run the simulation (make sure you are inside dev_ws).

source ./install/setup.bash
source ./setenv_gazebo.bash

Now you can use the simulation by launching with different worlds:

• turtlebot3_house.launch.py
• turtlebot3_world.launch.py
• empty_world.launch.py

If you run into trouble because of windows \r characters when launching the simulation you probably need to run.

dos2unix setenv_gazebo.bash

This will convert the script back into Unix.

ros2 launch turtlebot3_gazebo empty_world.launch.py

Now its time to interact with the simulation so start another LX Terminal and setup the environment once again

source ./install/setup.bash

Launch keyboard teleop and use the keys (a,w,d,x,s) as instructed to send command velocities to the TurtleBot3 and make it move around its world.

ros2 run turtlebot3_teleop teleop_keyboard