What is ROS?
ROS is a modular robotics platform that allows hardware and software components to work together. It's the middleware that links sensors, actuators, and programs. ROS organizes systems as nodes that communicate by passing messages, making it easier to build, test, and scale robotic applications with reusable tools.
Robotic Operating System 2 - Version Humble Hawksbill
ROS was started by Willow Garage Labs in 2007. In 2017, ROS 2 was released as a more secure, real-time-capable upgrade. ROS 2 Humble, released in 2022, is a stable long-term version used in many real-world robotics projects today. Version Humble was chosen for its vast documentation and freely available resources.
Breakdown of LAIKA stage 1 - Gaining an understanding, defining the space.
This section is focused on gaining a deep understanding of the core ROS 2 (Robot Operating System 2) framework, both in terms of practical implementation and the underlying theory.
This includes building familiarity with the architecture, message-passing mechanisms, nodes, topics, services, actions, parameters, and the ROS 2 build system (colcon, workspaces, and packages). My goal is not just to use ROS 2, but to understand how and why it works, and teach this to the members of Lehigh Rocketry so we can have effective payload development team.
In this section I'll work on documenting what already exists out there- what nodes and packages are in place, what topics are active, and what still needs to be created for the quadruped. This helps me figure out where to start, what gaps need to be filled, and how everything communicates. I'll be digging deep into the code bases and libraries that exist online, and code developed by the Robotics group Yahboom- who provided much of the open source code and hardware to start building up the Laika Program.
Below you will find notes on ROS2 Humble, that I took while learning the operating system. I'll also include links to any resources I used, videos I watched, and repositories I sourced.
Testing serial BUS connection from the RPI5 to the LUWU dynamics ESP32 lower computer. Using the LAIKA library (Github repository above) LAIKA is able to be controlled in pitch, roll, and yaw. Motors are not being directly controlled here, rather input is being fed into the lower board, which calculates joint position via an inverse kinematic algorithm. Individual motor control, which bypasses calculated inverse kinematic limits will be necessarily explored and performed in a later stage.
Notes on ROS2, Vol. 1
This section of notes covers the entire beginner CLI tools, includes useful code and a few pictures of ROS2 examples
A pull-pin start (AKA grenade pin starter)
Other than looking cool a pull pin/turn key start is a requirement for the electronics of sounding rockets of the SDL competition. The ability to arm, and disarm the dog from within the LV body is also essential for future testing. Using a small pull pin, the switch is physically accessible from the outer body of the payload bay via an access hole. A small green light allows the operator to see the state of the dog. A Dunkin' Doughnuts straw was used in this build... Spot it?
Experimental thermal testing
Launch day will be hot, occurring in the American south in June, thermal testing is a must. With all the electronics powered up and the the servos holding launch position prone, Laika underwent thermal testing, achieving a safe margin of ~1 hour pad time.
Notes on ROS2, Vol. 2
This section of notes covers the use of workspaces, node creation in python, building using colcon and the process of creating packages
Video review from an online teacher
Other than the official documentation, a number of YouTubers have provided basics courses in ROS. These fast moving, visual courses, are a fantastic spot to really solidify the learning from the written documentation. I recommend practice with the the official docs first, then reviewing it with Kevin Wood here on youtube.
