Introduction to Robot Operating System (ROS)

• ROS (Robot Operating System) serves as a flexible framework for writing robot software and facilitates communication between robot parts.
• It provides services for robotic applications like hardware abstraction, low-level device control, message-passing between processes, and package management.
• ROS promotes code reuse, collaboration between labs and companies, and provides an open-source ecosystem for the robotics community.

ROS History

• 2007: ROS began as an internal project at Willow Garage.
• 2008: ROS was released to the public.
• 2013: Willow Garage closed, and the Open Source Robot Foundation (OSRF) took over.
• 2015: OSRF evolved into Open Robotics.
• 2017: ROS2 development occurred.

Core Features

• ROS is modular and flexible, allowing for code reuse and easy integration of sensors and motors.
• ROS is utilized in universities, research, and industry.

ROS Architecture

• Node: A single program that performs one task, such as reading a sensor, moving motors, or processing camera images.
• Message: The actual data being sent, structured as pieces of information like temperature (float), GPS position (custom), or an image (array of pixels).
• Topic: A communication channel where nodes publish messages and other nodes subscribe to receive them, suited for continuous data.
• Service: A two-way communication method where one node calls and waits for a response, ideal for one-time commands or data requests.
• Use case: Useful when a robot needs to perform a one-off task, like taking a photo, getting the battery level, or resetting a map.
• Structure: A service server waits for requests, and a service client sends the request.
• Package: A folder containing related files such as code, message definitions, launch files, and configuration files; it is how ROS organizes a robot's software.

Basic Ubuntu Commands

• pwd: Displays the current working directory.
• ls: Lists files and folders in the current directory.
• cd foldername: Navigates into the specified folder.
• cd ..: Moves one directory back.
• mkdir myfolder: Creates a new folder.
• rm myfile.txt: Deletes a file.
• rm -r myfolder: Deletes a folder and its contents recursively.

Software Management Commands

• sudo apt update: Updates the package list.
• sudo apt upgrade: Upgrades installed packages.
• sudo apt install package-name: Installs a specific package.

File Creation and Writing Commands

• echo "Hello" > file.txt: Creates a file with the specified content.
• echo "Another line" >> file.txt: Appends content to an existing file.
• cat > file.txt: Allows writing multiple lines to a file.
• nano file.txt: Opens the nano editor to edit a file.

File Viewing Commands

• cat file.txt: Shows the contents of a file.
• less file.txt: Displays file contents page by page.

Permissions Command

• chmod +x filename: Makes a file executable.