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robotics_fundamentals_ros_gazebo repository

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robotics_fundamentals_ros_gazebo

Repository Summary

Checkout URI	https://github.com/andreasbihlmaier/robotics_fundamentals_ros_gazebo.git
VCS Type	git
VCS Version	main
Last Updated	2023-11-23
Dev Status	UNMAINTAINED
CI status	No Continuous Integration
Released	UNRELEASED
Tags	No category tags.
Contributing	Help Wanted (0) Good First Issues (0) Pull Requests to Review (0)

Packages

Name	Version
robotics_fundamentals_ros_gazebo	1.0.0

README

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:

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

Create ROS-Gazebo bridge:

  ros2 run ros_gz_bridge parameter_bridge \
    '/world/stiff_one_armed_bandit/model/double_pendulum_with_base/joint_state@sensor_msgs/msg/JointState[gz.msgs.Model' \
    '/model/double_pendulum_with_base/joint/upper_joint/cmd_force@std_msgs/msg/Float64]gz.msgs.Double' \
    '/model/double_pendulum_with_base/pose@tf2_msgs/msg/TFMessage[gz.msgs.Pose_V'
  

Unpause Gazebo
Add /world/stiff_one_armed_bandit/model/double_pendulum_with_base/joint_state/lower_joint/position to PlotJuggler
Add /model/double_pendulum_with_base/pose/double_pendulum_with_base/double_pendulum_with_base/lower_link/translation/y and z as XY plot to PlotJuggler

R2:

Start Gazebo:

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

Create ROS-Gazebo bridge:

  ros2 run ros_gz_bridge parameter_bridge \
    '/world/damped_stiff_one_armed_bandit/model/double_pendulum_with_base/joint_state@sensor_msgs/msg/JointState[gz.msgs.Model' \
    '/model/double_pendulum_with_base/joint/upper_joint/cmd_force@std_msgs/msg/Float64]gz.msgs.Double' \
    '/model/double_pendulum_with_base/pose@tf2_msgs/msg/TFMessage[gz.msgs.Pose_V'
  

Setup plots in PlotJuggler, similar to R1.
Set torque on upper_joint:

  ros2 topic pub --once /model/double_pendulum_with_base/joint/upper_joint/cmd_force std_msgs/msg/Float64 'data: 3.0'
  sleep 3
  ros2 topic pub --once /model/double_pendulum_with_base/joint/upper_joint/cmd_force std_msgs/msg/Float64 'data: 0.0'
  

Set friction coefficient of the upper_joint to zero and set the damping coefficient to 0.5:

  <joint name="upper_joint" type="revolute">
    <parent>base</parent>
    <child>upper_link</child>
    <axis>
      <xyz>1.0 0 0</xyz>
      <dynamics>
        <damping>0.5</damping>
        <!-- <friction>1.0</friction> -->
      </dynamics>
    </axis>
  </joint>
  

Restart Gazebo and repeat the torque command. Observe the difference in the plots.

R3:

Start Gazebo:

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

Create ROS-Gazebo bridge:

  ros2 run ros_gz_bridge parameter_bridge \
    '/world/one_armed_bandit/model/double_pendulum_with_base/joint_state@sensor_msgs/msg/JointState[gz.msgs.Model' \
    '/model/double_pendulum_with_base/joint/upper_joint/cmd_force@std_msgs/msg/Float64]gz.msgs.Double' \
    '/model/double_pendulum_with_base/pose@tf2_msgs/msg/TFMessage[gz.msgs.Pose_V' \
    '/joint_lower_joint_cmd_pos@std_msgs/msg/Float64]gz.msgs.Double'
  

Setup plots in PlotJuggler, similar to R1.
Set torque on upper_joint:

  ros2 topic pub --once /model/double_pendulum_with_base/joint/upper_joint/cmd_force std_msgs/msg/Float64 'data: 50.0'
  

Set joint position on lower_joint:

  ros2 topic pub --once /joint_lower_joint_cmd_pos std_msgs/msg/Float64 'data: 0.0'
  

Change the joint position of lower_joint and observe the resulting settling position of the pendulum.
You can also vary the lower_joint position more continuously:

  for q in $(seq 0 0.1 6.28); do
    ros2 topic pub --once /joint_lower_joint_cmd_pos std_msgs/msg/Float64 "data: ${q}"
  done
  

C1:

Start Gazebo along with a simulated UR5e robot:

  ros2 launch ur_simulation_ignition ur_sim_control.launch.py

Plot the robot’s joint efforts via the /joint_states topic.
Command trajectories to the simulated robot:

  ros2 launch ur_bringup test_joint_trajectory_controller.launch.py

CONTRIBUTING

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