NEXUS Robot Controller Server

Description

Wraps ros2_control controller manager into a lifecycle node.

The controller manager manages the loading of hardware interface plugins and controllers. And this node manages the manager in accordance with node lifecycles.

Specifically, it does as appropriate at lifecycle transitions:

• Load/unload controllers
• Switch controllers
• Spin up or destroy the ros2_control controller manager instance

Usage

To interface with this server, you just need to set ROS 2 parameters!

Set These ROS Parameters

• The robot description on ~/robot_description
  • With the appropriate hardware descriptions
• The controller configs
  • Like in the ros2_control example)
• The controllers you want this server to load and activate on ~/managed_controllers

Transition The Server

Then you’ll just have to run the appropriate lifecycle transitions!

• Configure spins up the ros2_control controller manager instance, loads the hardware interface plugins, loads the robot description, and loads the managed controllers
• Activate switches the managed controllers on, allowing the robot to be controlled
• Deactivate undoes Activate
• Cleanup undoes Configure

Configure will spin the ros2_control controller manager in a separate thread, and in a separate node.

Interfacing with the Server

You should not be calling the ros2_control controller manager’s services!

To change what controllers you’re using, transition the server’s lifecycle to Unconfigured and change the ~/managed_controllers parameters to the appropriate controllers you want loaded and activated! The server will dynamically update what controllers are loaded! Fancy!

Demo

A simple demo has been provided, using the ros2_control RRbot.

Setup

You’ll need to install ros2_control_demos! This is to get the rrbot_description package that the demo relies on.

git clone https://github.com/ros-controls/ros2_control_demos

Also remember to install any dependencies!

rosdep install --from-paths src/nexus/nexus_robot_controller --ignore-src

Running

In one terminal run the demo launchfile, which starts the RRbot base, RViz, and the robot controller server:

ros2 launch nexus_robot_controller rrbot_demo.launch.py

In another terminal run a loop that sends commands to the controller we’ll start:

watch -n0.1 "ros2 topic pub -1 forward_position_controller/commands std_msgs/msg/Float64MultiArray '{data: [-5.0, -5.0]}' \
          && ros2 topic pub -1 forward_position_controller/commands std_msgs/msg/Float64MultiArray '{data: [5.0, 5.0]}'"

Finally, transition the robot controller server!

ros2 lifecycle set /robot_controller_server configure   # Loads the controllers
ros2 lifecycle set /robot_controller_server activate    # Switch the controllers on (the robot should start moving)
ros2 lifecycle set /robot_controller_server deactivate  # Switch the controllers off (the robot should stop moving)
ros2 lifecycle set /robot_controller_server cleanup     # Unloads the controllers

Changelog for package nexus_robot_controller

0.1.1 (2023-11-20)

0.1.0 (2023-11-06)

• Provides the robot_controller_node which wraps the ControllerManager from ros2_controls in a LifecyleNode.