#RBE 500 Fall #Made by Prof. Berk Calli and Yash Patil In this tutorial we will install Gazebo 11 and all its supporting files that will aid us in robot simulation.
Use the following commands to install Gazebo and its supplementry files
sudo sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu-stable
`lsb_release -cs` main" > /etc/apt/sources.list.d/gazebo-stable.list'
wget https://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
Once this is done, update using and make sure it runs without any errors
sudo apt-get update
now install Gazebo using
sudo apt-get install gazebo libgazebo-dev
You can check your installation by running this in a new terminal
gazebo
To use Gazebo with ros2, there are certain packages that need to be installed
sudo apt install ros-humble-gazebo-ros-pkgs
Now we will install simulated robot controllers
sudo apt-get install ros-humble-ros2-control ros-humble-ros2-controllers
sudo apt-get install ros-humble-gazebo-ros2-control ros-humble-xacro
sudo apt-get install ros-humble-joint-state-publisher ros-humble-joint-state-
publisher-gui
Now your system is ready to simulate any robot.
These are optional steps just to make sure everything is alright.
Please find the zipped package that has one of many ways to spawn an URDF in Gazebo
using ROS2.
Extract the package to your workspace/src.
Before doing colcon build we have to install some dependencies for the package to
function correctly.
Run the following commands in terminal
sudo apt install python3-pip
sudo pip3 install transforms3d
Once you have successfully installed all the required packages, find the supporting zip file that contains rrbot simulation files.
That zip file contains 2 packages rrbot_description rrbot_gazebo
This package contains the description files for the rrbot such as its urdf, gazebo plugins, ros2 control definitions etc. Xacro has been used instead of URDF to keep the description more modular, you will find that the main file rrbot.urdf.xacro includes a bunch of different files, so you don't have to deal with a very large file. The important files for us are rrbot.gazebo.xacro and rrbot.ros2_control.xacro, these contains the configuration for ROS2 Control. Visit this link for understanding how to configure ros2 control for your robot: https://github.com/ros-controls/gazebo_ros2_control
This package launches the actual simulation environment. The gazebo_controllers.yaml file in config helps us define what kind of controller we want to use, here we are using a forward_command_controller that just takes the command and applies it as it is, we have selected position as the command interface, i.e. we will control the position of the joints, reset all will be calculated by the controller. We can also use velocity or effort (torque) as the command interface. The state interfaces is what kind of feedback we will receive from JointStateBroadcastser, here we are taking position, velocity and effort feedbacks from the robot. JointStateBroadcaster is a different type of controller, it basically reads the current joint states from simulation environment and publishes it on the topic /joint_states. The launch folder contains a launch file rrbot_world.launch.py which will be used to launch every thing, gazebo simulation environment, controller manager for ros2 control, robot state publisher.
Extract the zip file to your ros2 workspace and cd in your workspace
colcon build --symlink-install
. install/setup.bash
As we are using some gazebo plugins for camera, we need to source the gazebo setup bash file too
. /usr/share/gazebo/setup.bash
you can also put this in your .bashrc by doing
echo ". /usr/share/gazebo/setup.bash" >> ~/.bashrc
Now open a new terminal and run
ros2 launch rrbot_gazebo rrbot_world.launch.py
This should result in a new Gazebo window popping up with rrbot spawned, Now if you do ros2 topic list, you will be able to see a bunch of different topics /joint_states : This topic will have the robot's current state, i.e. position, velocity and efforts of each joint /forward_position_controller/commands : This is the control topic, this will be used to control the robot joints /camera1/image_raw : On this topic the robot will publish the camera feed, to visualize what the camera is seeing we can use rviz2. open a new terminal and run
ros2 run rviz2 rviz2
A new window with Rviz should open up, first set the 'Fixes Frame' to world, and then click on 'Add', Select 'By Topic', and then select 'image'. You will be able to see a small dialog box on left hand side with the current feed of camera. Now open up a new terminal and run
ros2 run rrbot_gazebo publisher
Note: This can also result in your system getting hanged for a few minutes, this is just a first time thing and please don't kill the node if this happens, average hang-time is around 2-3 mins, if it goes above 10 mins kill the launch file.
Gazebo.