Demos

This GitHub Repository provides templates for the development of ros2_control-enabled robots and simple simulations to demonstrate and prove ros2_control concepts.

If you want to have a rather step by step manual how to do things with ros2_control checkout ros-control/roscon2022_workshop repository.

What you can find in this repository

This repository demonstrates the following ros2_control concepts:

  • Creating a HardwareInterface for a System, Sensor, and Actuator.

  • Creating a robot description in the form of URDF files.

  • Loading the configuration and starting a robot using launch files.

  • Control of a differential mobile base DiffBot.

  • Control of two joints of RRBot.

  • Control of a 6-degrees-of-freedom robot.

  • Implementing a controller switching strategy for a robot.

  • Using joint limits and transmission concepts in ros2_control.

Goals

The repository has two other goals:

  1. Implements the example configuration described in the ros-controls/roadmap repository file components_architecture_and_urdf_examples.

  2. The repository is a validation environment for ros2_control concepts, which can only be tested during run-time (e.g., execution of controllers by the controller manager, communication between robot hardware and controllers).

Examples Overview

Example 1: RRBot

RRBot - or ‘’Revolute-Revolute Manipulator Robot’’ - a simple position controlled robot with one hardware interface. This example also demonstrates the switching between different controllers.

Example 2: DiffBot

DiffBot, or ‘’Differential Mobile Robot’’, is a simple mobile base with differential drive. The robot is basically a box moving according to differential drive kinematics.

Example 3: “RRBot with multiple interfaces”

RRBot with multiple interfaces.

Example 4: “Industrial robot with integrated sensor”

RRBot with an integrated sensor.

Example 5: “Industrial robot with externally connected sensor”

RRBot with an externally connected sensor.

Example 6: “Modular robot with separate communication to each actuator”

The example shows how to implement robot hardware with separate communication to each actuator.

Example 7: “6-DOF robot”

A full tutorial for a 6 DOF robot for intermediate ROS 2 users.

Example 8: “Using transmissions”

RRBot with an exposed transmission interface.

Example 9: “Gazebo Classic”

Demonstrates how to switch between simulation and hardware.

Example 10: “GPIO interfaces”

Industrial robot with GPIO interfaces

Example 11: “CarlikeBot”

CarlikeBot with a bicycle steering controller

Example 12: “Controller chaining”

The example shows a simple chainable controller and its integration to form a controller chain to control the joints of RRBot.

Example 13: “Multi-robot example (tba.)”

Example 14: “Modular robots with actuators not providing states and with additional sensors”

The example shows how to implement robot hardware with actuators not providing states and with additional sensors.

Example 15: “Using multiple controller managers”

This example shows how to integrate multiple robots under different controller manager instances.

Installation

You can install the demos locally or use the provided docker file.

Local installation

If you have ROS 2 installed already, choose the right version of this documentation and branch of the ros2_control_demos repository matching you ROS 2 distribution, see this table.

Otherwise, install ROS 2 iron on your computer.

Note

ros2_control and ros2_controllers packages are released and can be installed using a package manager. We provide officially released and maintained debian packages, which can easily be installed via aptitude. However, there might be cases in which not-yet released demos or features are only available through a source build in your own workspace.

Build from debian packages

Download the ros2_control_demos repository and install its dependencies with

mkdir -p ~/ros2_ws/src
cd ~/ros2_ws/src
git clone https://github.com/ros-controls/ros2_control_demos -b iron
cd ~/ros2_ws/
rosdep update --rosdistro=$ROS_DISTRO
sudo apt-get update
sudo rosdep install --from-paths ./ -i -y --rosdistro ${ROS_DISTRO}

Now you can build the repository (source your ROS 2 installation first)

cd ~/ros2_ws/
. /opt/ros/${ROS_DISTRO}/setup.sh
colcon build --merge-install

Build from source

  • Download all repositories

    mkdir -p ~/ros2_ws/src
cd ~/ros2_ws/src
git clone https://github.com/ros-controls/ros2_control_demos
cd ~/ros2_ws/
vcs import src < src/ros2_control_demos/ros2_control_demos.$ROS_DISTRO.repos
rosdep update --rosdistro=$ROS_DISTRO
sudo apt-get update

  • Install dependencies:

    rosdep install --from-paths src --ignore-src -r -y

  • Build everything, e.g. with:

    . /opt/ros/${ROS_DISTRO}/setup.sh
colcon build --symlink-install

  • Do not forget to source setup.bash from the install folder!

Using Docker

First, build the dockerfile with

mkdir -p ~/ros2_ws/src
cd ~/ros2_ws/src
git clone https://github.com/ros-controls/ros2_control_demos
cd ros2_control_demos
docker build . -t ros2_control_demos -f Dockerfile/Dockerfile

To view the robot

Docker now allows us to run the demo without the GUI if configured properly. Now we can view the robot by the following procedure:

After having ROS 2 installed on your local system (not inside the docker), we can use rviz2 to visualize the robot state and joint_state_publisher_gui package to give manual joint values to the robot. To install the package you can run:

sudo apt-get install -y ros-${ROS_DISTRO}-joint-state-publisher-gui ros-${ROS_DISTRO}-rviz2

Then we are ready to bring up all the components to view the robot. Let’s start with the docker container by running the following command:

docker run -it --rm --name ros2_control_demos --net host ros2_control_demos ros2 launch ros2_control_demo_example_1 view_robot.launch.py gui:=false

Note

Depending on your machine settings, it might be possible that you have to omit --net host.

Now, we need to start rviz2 to view the robot as well as joint_state_publisher_gui, each in their own terminals after sourcing our ROS 2 installation.

Terminal 1:

source /opt/ros/${ROS_DISTRO}/setup.bash
ros2 run joint_state_publisher_gui joint_state_publisher_gui

Terminal 2:

source /opt/ros/${ROS_DISTRO}/setup.bash
cd ~/ros2_ws
rviz2 -d src/ros2_control_demos/example_1/description/rviz/rrbot.rviz

Now, you can see the robot moving by changing the values of the joints by moving the sliders around in the joint_state_publisher_gui.

To run the ros2_control demos

The following command runs the demo without the GUI:

docker run -it --rm --name ros2_control_demos --net host ros2_control_demos

Note

Depending on your machine settings, it might be possible that you have to omit --net host.

Then on your local machine, you can run rviz2 with the config file specified:

cd ~/ros2_ws
source /opt/ros/${ROS_DISTRO}/setup.sh
rviz2 -d src/ros2_control_demos/example_1/description/rviz/rrbot.rviz

You can also run other commands or launch files from the docker, e.g.

docker run -it --rm --name ros2_control_demos --net host ros2_control_demos ros2 launch ros2_control_demo_example_2 diffbot.launch.py

Quick Hints

These are some quick hints, especially for those coming from a ROS1 control background:

  • There are now three categories of hardware components: Sensor, Actuator, and System. Sensor is for individual sensors; Actuator is for individual actuators; System is for any combination of multiple sensors/actuators. You could think of a Sensor as read-only. All components are used as plugins and therefore exported using PLUGINLIB_EXPORT_CLASS macro.

  • ros(1)_control only allowed three hardware interface types: position, velocity, and effort. ros2_control allows you to create any interface type by defining a custom string. For example, you might define a position_in_degrees or a temperature interface. The most common (position, velocity, acceleration, effort) are already defined as constants in hardware_interface/types/hardware_interface_type_values.hpp.

  • In ros2_control, all parameters for the driver are specified in the URDF. The ros2_control framework uses the <ros2_control> tag in the URDF.

  • Joint names in <ros2_control> tags in the URDF must be compatible with the controller’s configuration.

Examples