+2 votes
in Eurobot rules by (0 points)


- For the past 2 years ArUco tags are available on elements

- For the past 4 years ArUco tags are part of the game

- In the past ArUco were mainly justified for elements with unknown position

- This year all elements are in unknown position (or depending on updates, at least several of them)

- Elements (plants) are known to fall easily, making it even more dificult to locate and manipulate

- While other vision technics might help, ArUco tags offer a very precise position/orientation helpful for teams. This means tags are mailnly useful for close-up manipulations, rather than far-away detections.

- Teams have developped ArUco detectors, already used for robots hats, solar panels and table. So forcing the development of another vision technic might not be desirable.


As plants are curved, it could seem unpossible to find a flat surface for the ArUco tags, and indeed, a curve is not flat.. Hovever, due to machine vision constraints and imprecisions, detectors are already used to handle small deformations. They are base on edge and corner detection, and use averages in zones to define if it's white or black.


The size of the tags just has to be adapted to the shape to minimize deformation while remaining usable. After a few tests, 13.5mm tags (the black area) gave the best results. They are less impacted by deformations, and remain very visible for manipulation purposes.


To select the tag itself, more tests shown that "simple" tags (like n°17) gives best results.


Applying a tag arround a curve object deforms its dimensions, but we can counter it with some inkscape magic.


by (0 points)
Warning: ArUco tag 17 is so simple it can randomly appear in the environnement (ex: the 2020 boats)
by (0 points)

I remember the boat-gate, but it didn't prevented the robots to detect what they should. And while there is a risk, the table has been tested for hidden arucos, and the rules already precise that robots should not present multiple ranges of aruco tag. Moreover teams should ALWAYS filter their detection based on size/orientation/etc. 

While we should take care, I think the tradeoff is still in favor of tagging the plants with it.

By-the-way, I've generated the SVG for both plant types.

- It uses tag 37 for violet plants, and tag 17 for white ones

- It fixes the shape of the arcs so they actually matches the plant (while keeping a 6mm overlap for perfect junction). (The arc in the beta vinyl doesn't properly align with the plant pots, the curvature is wrong)

- And yes, a light violet backgound is OK, because it's not a white color that matters, but a high differential to allow contour detection.

- This was printed on paper and tested arround the plants. And it fits soooo well. (see bellow)

by (0 points)

"Moreover teams should ALWAYS filter their detection based on size/orientation/etc. "

It is not possible to discriminate between a small tag up close, and a large tag far away. 
I agree that you can filter for only upright tags in this case, but in 2020 the goal was to check the orientation :p

Anyway it is doable, I just think that using the tag 17 (rather than any other) induces unnecessary obstacles

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+1 vote
by [Referee] (100k points)
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