How do you set up ROS for multiple sensors and actuators?

1 Install ROS

The first step is to install ROS on your computer or robot. ROS supports several operating systems, such as Ubuntu, Debian, and Windows, but the most widely used and recommended one is Ubuntu Linux. You can find detailed instructions on how to install ROS on different platforms on the official ROS website. Depending on your needs, you can choose between different distributions and packages of ROS, such as ROS Noetic, ROS Melodic, or ROS Kinetic. Make sure you install the full desktop version of ROS, which includes the core packages, the graphical tools, and the simulation environment.

2 Create a workspace

The next step is to create a workspace where you will store your ROS projects and packages. A workspace is a directory that contains all the source code, configuration files, and build files for your ROS applications. To create a workspace, you need to use the catkin tool, which is a build system for ROS that automates the compilation and installation of your packages. You can create a workspace by running the following commands in a terminal:

mkdir -p ~/catkin_ws/src
cd ~/catkin_ws/
catkin_make
source devel/setup.bash        

The first command creates a directory named catkin_ws in your home folder, and a subdirectory named src where you will place your packages. The second command changes the current directory to catkin_ws. The third command runs the catkin_make tool, which creates the build and devel directories where the binaries and scripts will be generated. The fourth command sources the setup.bash file, which sets up the environment variables and paths for your workspace.

3 Write nodes

The third step is to write nodes for your sensors and actuators. A node is a program that performs a specific task in ROS, such as reading data from a sensor, processing data, or sending commands to an actuator. Nodes communicate with each other by exchanging messages through topics, services, or actions. You can write nodes in different programming languages, such as C++, Python, or Java, using the ROS client libraries, such as rospy, roscpp, or rosjava. You can also use existing nodes from other packages, such as sensor drivers, filters, or controllers. To create a package for your node, you need to use the catkin_create_pkg tool, which generates the necessary files and dependencies for your package. You can create a package by running the following command in a terminal:

cd ~/catkin_ws/src
catkin_create_pkg my_package rospy roscpp std_msgs        

The first command changes the current directory to src. The second command creates a package named my_package that depends on rospy, roscpp, and std_msgs, which are common ROS packages for Python, C++, and standard messages. You can then write your node code in the src subdirectory of your package, and edit the CMakeLists.txt and package.xml files to configure the build and installation options for your package.

4 Launch the system

The final step is to launch the system and test the communication and coordination between your sensors and actuators. To launch the system, you need to use the roslaunch tool, which starts multiple nodes and sets up the parameters and environment for them. You can create a launch file for your system, which is an XML file that specifies the nodes, arguments, remappings, and other options for your system. You can create a launch file by creating a launch subdirectory in your package, and writing the XML code in a file with the .launch extension. You can then launch the system by running the following command in a terminal: roslaunch my_package my_system.launch The command launches the system using the launch file named my_system.launch in the my_package package. You can then use the ROS tools, such as rostopic, rosnode, rqt, or rviz, to monitor, visualize, and debug your system. You can also use the rosbag tool to record and playback your data for analysis and testing.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?