Pi Wars 2024 Challenge 2 – Eco-Disaster

Pi Wars 2024 Challenge 2 – Eco-Disaster

In this post we will focus on the second Pi Wars Challenge – Eco Disaster

We will first have a look at the rules as set out by the Pi Wars organisers, and then write our specific thoughts, actions, trials and errors underneath in date order. Follow us along as we get prepared for this second Pi War Challenge.

Aim of the challenge

A truck has over-turned, spilling its cargo of drums containing toxic slime. One of the drums has split and contaminated some of the others. There are 6 clean drums (which are green) and contaminated (red) drums. Your robot must deliver the clean drums to the clean zone (which is blue and on the left-hand side of the arena) and the contaminated drums to the contaminated zone (which is yellow and on the right–hand side of the arena). Your robot can push the drums across the arena or pick them up and carry them.

Time is of the essence; the task must be completed as quickly as possible to avert an Ecological Disaster!

Watch the video of Doofus showing how it should be done.

Control method

Remote control or Autonomous.

Please note: Teams in the Young Persons, Beginner and Intermediate category may choose to use remote control. Advanced category teams must do the challenge autonomously.

Time limit

Robots will be allowed 5 minutes to correctly sort as many of the barrels as possible.

An additional 1 minute at the start of the challenge can be used for calibration.


  • Robots will be placed in a starting box.
  • The challenge arena is shown as a diagram below (click to embiggen). Dimensions are in mm:
  • The arena has a perimeter wall which is 300mm tall. The dimensions in the diagram define the inside edge of the wall.
  • The arena floor and walls are painted matt black apart from the clean and contaminated zones. The wall behind those zones bears the appropriate colour for the zone for the entire height of the wall. Decorative decals will be applied to the arena, these are only grey scale in colour.
  • The barrels are curved and are 80mm high and 56mm in diameter. They weigh 46g and are 3D printed in PLA. They slide easily on the arena floor so long as they are pushed gently from a position low on the drum. Push them too hard and they may topple and start rolling around; this makes the game much more difficult! There will be 12 barrels in total
  • The barrels are 3D-printed in red and green. (Previously they were going to be painted, but they were white underneath and we thought that chips could occur throughout the day, so we’ve changed to 3D-printing).
  • Multiple drums can be pushed/carried at once but you are not allowed to touch the drums by hand.
  • White circles labelled “R” and “G” will be marked on the arena floor showing the start locations of the red and green drums which will be the same for all teams.
  • Drums will be placed within a designated box which leaves a 300mm space between the walls and drums; this is to allow space for robots to manoeuvre between the drum and wall if required.
  • We will attempt to provide even, diffuse, white lighting across the entire arena to assist with autonomous vision systems. However, teams should try to build vision systems which are robust under non-uniform lighting conditions.
  • At the end of the allotted time, the Judge will count the number of drums successfully delivered to the appropriate zone. A drum will be deemed delivered if any part of it is touching, or positioned over, the appropriate coloured floor patch.
  • If a drum is delivered but is then inadvertently pushed out of the zone, then it will no longer be “delivered” unless it is returned to the zone.

Vision System Calibration

A small area will be created next to the main arena which will contain boards bearing the colours of the clean and contaminated zones. Drums in the appropriate colours will also be provided. This will enable teams to calibrate the colours within their control systems for autonomous machines outside of their designated competition time. However, teams may also calibrate their machines in the live arena for two minutes before their 5-minute run.

Detail of the manufacture used for the arena and drums will be published prior to the games. Hue values will also be provided to assist with vision system calibration.


For ranking purposes, robots will be timed. Tie-breaks will be settled based on the highest number of barrels sorted in the shortest time. Points will be awarded according to rank using the Formula Scoring System. Only robots delivering all the drums correctly will be eligible for these ranking points, but of course will accumulate additional points as below.

Autonomous robots

  • 80 points will be awarded for each barrel sorted correctly.
  • 40 points will be deducted for each barrel sorted incorrectly.
  • An additional 50 points will be awarded for correctly sorting 6 barrels.
  • An additional 150 points will be awarded for correctly sorting 12 barrels.
  • An additional 250 points will be awarded for attempting this challenge autonomously.

Remote-controlled robots

  • 50 points will be awarded for each barrel sorted correctly.
  • 25 points will be deducted for each barrel sorted incorrectly.
  • An additional 50 points will be awarded for correctly sorting 6 barrels.
  • An additional 150 points will be awarded for correctly sorting 12 barrels.


There will be no penalties applied for rescuing the robot however the clock will not be stopped for rescues. You may not touch the barrels by hand at any time.

Initial thoughts

Key is speed and accuracy. Knowing the placement of barrels up front means can gauge route beforehand (serving purpose of) avoiding knocking any barrels over. But of course, if pushing nominated barrel to appropriate zone will need to think carefully beforehand about what order to go in. In terms of control, Wrecks mustn’t thrust too fast forward or backwards. No jerky movements, must be smooth. What can be attached to front to push (some sort of widened scooper) but not too wide, or even better something that can be controlled (possibly by servo motors) to open and close. That would be good. What do you use to recognise colours – is it a camera sensor? Need to explore this. How do you set the parameters?

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