A tiny robot with two wheels for sumo tournaments

Pint-sized Sumo Robot Is Adorable, Accessible And Totally Awesome

We’ve seen plenty of impressive robots of all sizes here at Hackaday, but recently we were particularly inspired by [Hans Jørgen Grimstad] and his thrifty mini sumo build.

Using the BBC micro:bit platform as a starting point, Hans seized the opportunity to build a competitive mini sumo bot without breaking the bank. According to his blog, the enchanting little machine uses commonly available parts and cost around $30 when built in 2020 (or $50 according to the more recent video, perhaps taking into account the cost of hardware in these trying times).

The results can be seen in the video below. Some sacrifices were made – Hans admits that the 3.3 V linear regulator gets a little toasty, but the design is kept much simpler by doing away with a switching regulator. The 700 RPM N20 motors are wired directly up to the 6 V battery pack, giving this plucky wrestler plenty of sumo-smashing power.

Hans hopes that the build can lower barriers to entry for new builders in robot tournaments, being something that can easily be put together in a garage or local makerspace for a low, low price. The mini sumo form factor is a great beginner or amateur project, made even easier when makers like Hans put all the nitty-gritty details up on GitHub. This is certainly not the first accessible sumo robotics project that we have covered, and it won’t be the last. We hope we see loads more of these endearing robotic gladiators at future events.

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SimpleSumo Bots Teach More Than Fighting

[MechEngineerMike] wrote in to share the enthusiasm over SimpleSumo, a series of open source, customizable robots he designed for mini-sumo battling and much more. For the unfamiliar, mini-sumo is a sport where two robots try to push each other out of a ring. [Mike]’s bots are simplified versions designed for education.

[Mike] was inspired by a video of some kids building mini-sumo bots who were doing anything and everything to personalize them. He vowed to make his own affordable, easy-to-build bots with education firmly in mind. His other major requirement? They had to be as easily customizable as that one potato-based toy that eventually came with a bucket of parts. As of this writing, there are 34 interchangeable accessories.

[Mike]’s first idea was to build the bots out of custom 3D-printed building blocks. He soon found it was too much work to print consistent blocks and switched to a modular cube-like design instead. SimpleSumo bots can do much more than just fight each other. [Mike] has written programs to make them flee from objects, follow lines, find objects and push them out of the ring, and beep with increasing frequency when an object is detected.

The bots are completely open source, but [Mike] sells kits for people who can’t print the parts themselves. He’s made a wealth of information available on his website including links to outside resources about mini-sumo, Arduino, programming, and 3D design. How about a complete series of assembly videos? First one is after the break.  Don’t know how to build a battle ring? He’s got that covered, too.

For a sumo bot that’s more brains than brawn, check out Zumo Red, the smart sumo.

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Glue Your Sumo Robot To The Mat With Custom Sticky Tires

Mini Sumo seems like one of those hobbies that starts out innocently enough, and ends up with a special room in the house dedicated to it. One day you’re excitedly opening up your first Basic Stamp kit, and the next you’re milling out mini molds on a mini lathe to make mini extra sticky tires.

[Dave] started out trying to find a part from the local big box store that was just a little bigger than the wheel he wanted to rubberize. He set the wheel inside a plumbing cap and poured the urethane in. It worked, but it required a lot of time with a sharp knife to carve away the excess rubber.

In the meantime he acquired a Sherline Mini Mill and Lathe. With the new tools available to him, he made a new mold out of a bit of purple UHMW and some acrylic. This one produced much nicer results. Using a syringe he squeezed resin into the mold through a hole in the acrylic. Much less cleanup was needed.

He later applied these methods to smaller, wider wheels as his mini sumo addiction took a stronger hold on his life.

Smart Sumo Seeks Central Security

[David] over at Pololu programmed a mini-sumo robot, Zumo Red, with some extra smarts.

The basic rules of sumo robotics is exactly like human sumo – push your competitor out of the ring. [David]’s robot is special because it not only detects the competition border but measures the robot’s angle to the perimeter circle. Knowing the angle, [David]’s robot can turn and run for the center of the arena, the safest location. Once safe it can attack competitors from a symbolic high-ground. Unfortunately, the robot was a light weight in an already low weight class competition. It failed to push any competitors out of the ring and did not fare well in face-to-face battles. 0J6807.550

[David]’s bot uses a three LED line sensor, pretty common today for line following, to detect the boundary. As the ‘bot is moving an outer sensor will detect the border. It continues to drive forward until the middle sensor gets a hit. That provides the measurements need to calculate the angle. Neat and simple! Knowing the angle, the robot scoots to the center to plan its next attack.

[David’s] made the code for his bot’s brain, an Arduino compatible ATmega32U4, available so it will be interesting to see if the competition picks up on this trick.

Zumo Red meets Sumo Necko and a few more competitors in the video after the break.

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Nano Sumo Robot Takes On All Comers


While most Sumo-style robots are fairly sizable, there is a subsection of the Sumo robot movement that focuses on making small robots. Really small robots.

[Patrick] wrote in to share his latest creation, a Nano Sumo robot measuring a scant 1 in. x 1 in. The Nano Sumo is operated by an ATMega 328 micro controller housed on a custom-built PCB. The board was designed to interface directly with the 1A Dual Motor Driver from SparkFun, which provides all of the PWM signaling to the motors for speed control and braking. A small 50mAh Li-poly battery is attached to the robot, which can be charged using 4 AA batteries via a custom charging circuit. The mechanical components of the bot were handled by his friend [Gary], which you can read about here.

As you can see in the video below, the bot does its job pretty well. It does seem like the object detection gets confused every once in awhile, but that can likely be remedied with a few software tweaks.

Check out his page for additional build videos, including the PCB construction and programming processes.

If you’re interested in learning more about Sumo bots, check out this slightly larger robot we covered a short while back.

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Sumo Style Robot

[Jeremy] really wants to compete in some sumo bot wrestling, and in order to have robotic sumo wrestling one needs to make some robots, which is what [Jeremy’s] build log is all about.

The framework is made out of 6mm thick Sintra (which is a type of closed cell pvc foam sheet) with the use of a CNC machine, using a “sliced” design style framework. Two geared motors fit snug inside of the internal frame and some wheels from solarbotics are attached to the ends. The arrangement of the drive wheels in the rear, and the large front end, seems like good design for the end application where robots doing turtle flips would be no fun.

Keeping in mind this is not a fully finished project and therefore does not have code or schematics posted, the brains of this beast are in a similar state, and should be pretty easy to figure out. The thinking is handled by an atmega328, and fed by IR sensor pair’s to detect light / dark patterns on the floor or table, and an array of proximity sensors along the front and sides to detect its opponent.

And while this project may not be completed, it at one point was dead and set aside, after some months [Jeremy] went back for a second look and found out that the only thing dead about it was the power regulator and h-bridge and quickly got it back up and working, which is a good reminder to not give up, even when it does go poof.