bluetech_simulation

Contains the ROS2 package for bluetech navigation simulated in Gazebo.

Installation

Requirements

Make sure you have the following installed/running on your machine.

• git must be working correctly. Since we will be pushing to private remote repositories, make sure you have git setup correctly, use the Git Credential Manager to make sure git commands work correctly without permission errors.
• Ubuntu 22.04
• ROS2 - Humble (do NOT build from source, the debian packages are what is required for proper installation. In general, for any ROS related packages, do not build from source unless absolutely necessary)
• colcon

Creating a ROS2 workspace

Create a ROS2 workspace called ros2_ws (in your home directory) - instructions to do so can be found here. Once you have made a workspace you will have an src folder, enter this folder.

cd ~/ros2_ws/src

Dependencies

Before running any files, make sure you have to following dependencies installed.

• ros2_control
• custom_gazebo_pkgs
• classic gazebo 11

Cloning the package

Inside the src folder, clone the repository. This is a ROS2 package and has to be built after cloning.

git clone <link_to_repo>

Buidling

You need to source the ROS installation everytime you open a new terminal using the following command.

source /opt/ros/humble/setup.bash

If you do not want to source the installation every time add this line to the end of your .bashrc file in your home directory using

echo "source /opt/ros/humble/setup.bash" >> ~/.bashrc

It’s good practice to run rosdep in the root of your workspace ros2_ws to check for missing dependencies before building:

rosdep install -i --from-path src --rosdistro humble -y

After cloning the repository go to the root of the workspace you just created and build the package using colcon. Any ROS2 package needs to be built by going into the root of the workspace. Use the --packages-select argument to build only the needed packages.

cd ~/ros2_ws
colcon build --packages-select bluetech_simulation

Source the install setup.bash from the ros2_ws you just created.

source ~/ros2_ws/install/setup.bash

That's it! You have successfully built the bluetech_simulation package!

Usage

There are several ROS nodes and launch files in the package which can be used to spawn robots, add forces, toggle parameters.

To understand what each function/node does please refer to the following readme.

Structure

The package has the following sub-directories

• bluetech_simulation contains all the ROS2 nodes
• config contains all the .yaml files
• description contains all the urdf.xacro files
• launch contains all the launch.py files
• worlds contains the sdf files that describe the gazebo worlds.

Contributing

Anytime a new change is made which involves a new dependency, please make sure to update the package.xml file so that the package builds correctly.
Ideally when developing, create your own branch with an appropriate name.

Testing

To check if your package has been built and dependencies have been installed correctly run the code for basic robot walking.
Make sure you have sourced the ros2_ws and the ROS2 installation. In the root of your ros2_ws launch the world file using:

cd ~/ros2_ws
ros2 launch bluetech_simulation bluetech_sim.launch.py

This should open a gazebo window and RViz to visualize the static and dynamic transforms. In another terminal check to see if the effort controllers have been spawned correctly.

ros2 control list_hardware_interfaces

You should see the following output:

command interfaces
	left_wheel_joint/effort [available] [claimed]
	right_wheel_joint/effort [available] [claimed]
state interfaces
	left_wheel_joint/effort
	right_wheel_joint/effort

In another terminal check for the following ROS2 topics.

ros2 topic list

or use the -t argument to check the type of message on the topic.

ros2 topic list -t

There will be many topics listed, make sure you have the following topics listed (this output is without the -t argument):

/joint_states
/left/friction
/left/friction_status
/left_wheel_effort_controller/commands
/left_wheel_effort_controller/transition_event
/right/friction
/right/friction_status
/right_wheel_effort_controller/commands
/right_wheel_effort_controller/transition_event
/robot_description
/rosout
/tf
/tf_static

In another terminal run the feed_forward node to move the robot using with a specific effort for example:

ros2 run bluetech_simulation feed_forward 1

Problems

Gazebo

Often the gazebo server will crash unexpectedly and needs to be restarted. Make sure to kill the gazebo client and server completely before restarting gazebo using:

killall -9 gzserver
killall -9 gzclient

Gazebo + ros2_control

While controlling joints using ros2_control make sure to use effort_controllers and not position_controllers or trajectory_controller, they force gazebo to turn the joints to a specified position and may result in unexpected or unrealistic behaviour.

Ideally use a custom PID controller with the effort_controller and command a setpoint in position to move the joint to. This is under development here