Botball

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In 2018, a few friends and I were convinced to represent HTL Spengergasse at ECER Botball, the European Conference on Educational Robotics. Our school had not fielded a team in previous years, so we had no accumulated knowledge to draw from. None of the four of us had any background in robotics or C. We went with Bluescreen Factory as our team name, which felt appropriate.

The Competition

Each team is given two robots. One is a repurposed Roomba and the other is a custom-built bot with servo motors driven by a KIPR controller board. The arena is a table populated with props, small fluffy balls representing water, and wooden figures representing people. The theme for our year was fire rescue. You scored points by collecting water or people and delivering them to a dropoff zone, all autonomously.

Schematic 3D view of the Botball arena table
A schematic overview of the arena table. Props, people, and water balls are distributed across the surface for teams to collect and deliver.

We met every week for a full afternoon throughout the school year, building a local replica of the arena, writing and testing code, and trying to make our routines reliable enough to trust in competition. Hardware faults developed along the way. The Roomba stopped charging reliably and the GPIO ports on the second robot would simply stop responding.

Programming

The KIPR SDK is written in C, which none of us knew coming in. Rather than learn just enough C to get by, I spent a significant portion of our preparation time porting the library to Go. A surprisingly tricky part of that work was making the robots drive straight and travel exact distances, something that sounds trivial until you are dealing with imprecise motors and no closed-loop feedback.

Roomba bot collecting wooden figures
Our roomba bot attempting to collect wooden figures representing people during practice.
Custom-built bot funneling fuzzy balls
The custom-built bot collecting fuzzy balls representing water into a bucket.
Roomba bot rescuing plush figures
The roomba bot performing a rescue on plush figure during practice.

The Tournament

When we arrived at the competition in spring 2019, the arena floor turned out to have a raised gravel texture and was not flat. We knew it would be plastic plates, but the texture and the ridge running along the seam between them were not mentioned anywhere in the specifications we had practiced against.

The texture cost our lighter robot traction, causing its wheels to slip mid-routine. The ridge was worse. Our Roomba used a cage that slid along the floor surface and it got stuck every time it crossed the join. A plan we were confident in fell apart on details that were, by the rules, never supposed to exist. Safe to say, we did not return the following year.

The Bluescreen Factory team holding the Outstanding Programming award
Bluescreen Factory with the Outstanding Programming award for porting the KIPR C library to Go. Left to Right: M. Mayerhofer, C. Hahn, W. Muth and L. Marx

Looking Back

This was seven years ago now. The result on the day was frustrating, but looking back it was a genuinely fun project to be part of. We built something from nothing, no seniors to learn from, unfamiliar hardware, a language none of us knew, and we walked away with the Outstanding Programming award for the library port. HTL Spengergasse also covered the competition in a short news post.