ROSCon DE 2023 talk “Learning Robotics Fundamentals with ROS 2 and modern Gazebo”

Slides available here

Setup:

• Follow the official installation instructions at https://docs.ros.org/en/humble/Installation/Ubuntu-Install-Debians.html.
• In the step “Install ROS 2 packages”, install the packages ros-humble-desktop and ros-dev-tools.
• In addition, install the following packages

  sudo apt install \
    python3-colcon-common-extensions \
    ros-humble-ign-ros2-control \
    ros-humble-plotjuggler-ros \
    ros-humble-ros2-control \
    ros-humble-ros2-controllers \
    ros-humble-ros-gz-sim-demos \
    ros-humble-ros-ign-gazebo \
    ros-humble-rqt-joint-trajectory-controller \
    ros-humble-rqt-tf-tree
  

M1:

• Start (modern) Gazebo:

  ros2 launch ros_gz_sim gz_sim.launch.py gz_args:="empty.sdf -r"
  

• Spawn a simple mobile robot in Gazebo:

  ros2 run ros_gz_sim create -file $(pwd)/vehicle_blue.sdf -z 0.325
  

• Create a bridge between ROS and Gazebo:

  ros2 run ros_gz_bridge parameter_bridge \
    '/model/vehicle_blue/cmd_vel@geometry_msgs/msg/Twist]gz.msgs.Twist' \
    '/model/vehicle_blue/pose@tf2_msgs/msg/TFMessage[gz.msgs.Pose_V'
  

• Start PlotJuggler

  ros2 run plotjuggler plotjuggler
  

• Add plots:
  • ROS2 Topic Subscriber -> Select /model/vehicle_blue/pose
  • Drag and drop /model/vehicle_blue/pose/empty/vehicle_blue/translation/x from Timeseries List to the plot area
  • Split the plot vertical twice
  • Add Custom Series -> Input timeseries: Same x as above; Function library: backward_difference_derivative; New name: v; Create New Timeseries
  • Drag and drop v from Custom Series to the middle plot and to the bottom plot
  • Apply filter to data on the bottom plot -> Derivative
  • Now the top plot shows the position x, the middle plot shows the velocity v, and the bottom plot shows the acceleration a.
• Command the mobile robot to move forward:

  ros2 topic pub --once /model/vehicle_blue/cmd_vel geometry_msgs/msg/Twist '
  linear:
    x: 0.1
    y: 0.0
    z: 0.0
  angular:
    x: 0.0
    y: 0.0
    z: 0.0'
  

P1:

• Start Gazebo:

  ros2 launch ros_gz_sim gz_sim.launch.py gz_args:="$(pwd)/falling_world.sdf"
  

• Create ROS-Gazebo bridge:

  ros2 run ros_gz_bridge parameter_bridge '/model/sphere/pose@tf2_msgs/msg/TFMessage[gz.msgs.Pose_V'
  

• Record pose of falling sphere:

  ros2 bag record /model/sphere/pose
  

• Unpause Gazebo
• Wait for sphere to hit the ground. Stop recording.
• Open bag file in PlotJuggler

P2:

• Start Gazebo:

  ros2 launch ros_gz_sim gz_sim.launch.py gz_args:="$(pwd)/slippery_slope.sdf"
  

• Create ROS-Gazebo bridge:

  ros2 run ros_gz_bridge parameter_bridge \
    '/model/sphere/pose@tf2_msgs/msg/TFMessage[gz.msgs.Pose_V' \
    '/model/cylinder/pose@tf2_msgs/msg/TFMessage[gz.msgs.Pose_V'
  

• Record pose of falling sphere:

  ros2 bag record /model/sphere/pose /model/cylinder/pose
  

• Unpause Gazebo
• Wait for both objects to have rolled down the inclined plane. Stop recording.
• Open bag file in PlotJuggler

R1:

• Start Gazebo:

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