3D Printing Omni-Balls For Robot Locomotion

Wheels are all well and good for getting around, but they only tend to rotate about a single axis. Omni-wheels exist, but they’re still a little too pedestrian for [James Bruton]. His latest project involved 3D printing custom omni-balls which roll in all directions. (Video, embedded below.)

The omniball concept comes from earlier work by Osaka University, which also produced a treaded tank-like vehicle by the name OmniCrawler as well. The spherical design, fitted with an axle and casters as well, allows rotation in multiple directions, allowing for a platform fitted with such omni-balls to easily rotate and translate in all directions.

[James] set about creating his own version of the design, which relies on grippy TPU filament for grip pads to give the 3D printed hemispheres some much needed grip. There’s also bearings inside to allow for the relative rotation between the hemispheres and the internal castor, necessary to allow the wheels to move smoothly when sitting on either pole of the hemispheres.┬áSkate bearings were then used to assemble three of the omni-balls onto a single platform, which demonstrated the ability of the balls to roll smoothly in all directions.

While it’s just a demonstration of the basic idea for now, we can imagine these balls being used to great effect for a robot platform that needs to navigate in tight spaces on smooth surfaces with ease. The mechanical complexity of the omni-balls probably negates their effective use in dirtier offroad contexts, however.

We’ve seen [James]’s work before too – such as his compliant leg design for walking robots, and his active gyroscope balancer last week. When does [James] sleep?

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Hamster Goes On Virtual Journey

Hamsters are great pets, especially for those with limited space or other resources. They are fun playful animals that are fairly easy to keep, and are entertaining to boot. [Kim]’s hamster, [Mr. Fluffbutt], certainly fits this mold as well but [Kim] wanted something a little beyond the confines of the habitat and exercise wheel and decided to send him on a virtual journey every time he goes for a run.

The virtual hamster journey is built on an ESP32 microcontroller which monitors the revolutions of the hamster wheel via a hall effect sensor and magnet. It then extrapolates the distance the hamster has run and sends the data to a Raspberry Pi which hosts a MQTT and Node.js server. From there, it maps out an equivalent route according to a predefined GPX route and updates that information live. The hamster follows the route, in effect, every time it runs on the wheel. [Mr Fluffbutt] has made it from the Netherlands to southeastern Germany so far, well on his way to his ancestral home of Syria.

This project is a great way to add a sort of augmented reality to a pet hamster, in a similar way that we’ve seen self-driving fish tanks. Adding a Google Streetview monitor to the hamster habitat would be an interesting addition as well, but for now we’re satisfied seeing the incredible journey that [Mr Fluffbutt] has been on so far.

3D Printed Wobbly Wheels Put Through Their Paces

When we talk about wheels, the vast majority of the time we’re talking about ho-hum cylindrical rollers as seen on all manner of human conveyances. However, there are all manner of wild and wacky shapes that roll, and having had some experience with them, [Maker’s Muse] decided to take a shot at having a robot drive on them. (Video, embedded below.)

The benefit of a 3D printer is that it makes producing these parts with strange geometries a cinch. The video shows a variety of designs, from the wobbly “Nightshades” to the entertaining “Prongle” wheels being put through a variety of tests. In an attempt to equalise the playing field, each design was matched in its surface area so as not to artificially bias the results.

While the wobbly designs look strange, they also come with some benefits over simple disc wheels, providing extra traction on both carpet and sand. Particularly impressive was the performance of the 8-spoke wheels on the beach, though as this design mimics real-world sand tyres, we’re not surprised at the results. We’ve seen similar 3D printed parts do the job for driving on water, too.

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One Wheel Is All We Need To Roll Into Better Multirotor Efficiency

Multirotor aircraft enjoy many intrinsic advantages, but as machines that fight gravity with brute force, energy efficiency is not considered among them. In the interest of stretching range, several air-ground hybrid designs have been explored. Flying cars, basically, to run on the ground when it isn’t strictly necessary to be airborne. But they all share the same challenge: components that make a car work well on the ground are range-sapping dead weight while in the air. [Youming Qin et al.] explored cutting that dead weight as much as possible and came up with Hybrid Aerial-Ground Locomotion with a Single Passive Wheel.

As the paper’s title made clear, they went full minimalist with this design. Gone are the driveshaft, brakes, steering, even other wheels. All that remained is a single unpowered wheel bolted to the bottom of their dual-rotor flying machine. Minimizing the impact on flight characteristics is great, but how would that work on the ground? As a tradeoff, these rotors have to keep spinning even while in “ground mode”. They are responsible for keeping the machine upright, and they also have to handle tasks like steering. These and other control algorithm problems had to be sorted out before evaluating whether such a compromised ground vehicle is worth the trouble.

Happily, the result is a resounding “yes”. Even though the rotors have to continue running to do different jobs while on the ground, that was still far less effort than hovering in the air. Power consumption measurements indicate savings of up to 77%, and there are a lot of potential venues for tuning still awaiting future exploration. Among them is to better understand interaction with ground effect, which is something we’ve seen enable novel designs. This isn’t exactly the flying car we were promised, but its development will still be interesting to watch among all the other neat ideas under development to keep multirotors in the air longer.

[IROS 2020 Presentation video (duration 10:49) requires no-cost registration, available until at least Nov. 25th 2020. Forty-two second summary embedded below]

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Circle Guitar Creates Wall Of Sound

In the 60s a musical recording technique called the “wall of sound” came to prominence which allowed artists to create complex layers of music resulting in a novel, rich orchestral feeling. While this technique resulted in some landmark albums (Pet Sounds by the Beach Boys for example) it took entire recording studios and many musicians to produce. This guitar, on the other hand, needs only a single musician but can create impressive walls of sound on its own thanks to some clever engineering.

Called the Circle Guitar and created by [Anthony Dickens], the novel instrument features a constantly-rotating wheel around the guitar’s pickups in the body. Various picks can be attached in different ways to the wheel which pluck the strings from behind continuously. This exceeds what a normal guitar player would be able to do on their own, but the guitarist is able to control the sounds by using several switches and pushbuttons which control a hexaphonic humbucker and are able to mute individual strings at will. Of course, this being the 21st century, it also makes extensive use of MIDI and [Anthony] even mentions the use of a Teensy.

While details on this project are admittedly a little fleeting, the videos linked below are well worth a watch for the interesting sounds this guitar is able to produce. Perhaps paired with a classic-sounding guitar amplifier it could produce other impressive walls of sound as well. Either way, we could expect someone like [Brian Wilson] to be interested in one once it is in production.

Thanks to [Mel] for the tip!

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Super Easy Small Robot Wheels

Anyone who has delved into DIY wheels knows that they are a trickier than it may seem, especially if the wheels aren’t just for show and need to provide things like decent traction and durability. 3D printers have helped a lot, but they’re not a cure-all.

Check out how [Robert K.] makes wheels from segments of automotive silicone hose, which are constructed with fibers embedded within them for durability and structure. Not only are these hoses easily sourced, but the silicone makes a great wheel surface and the hoses themselves are highly durable. He uses a 3D printed jig to cut a slice of hose that press-fits perfectly onto a 3D printed hub. [Robert] finds that a 28 mm hose pulled over a 35 mm diameter wheel is a perfect fit.

These wheels are for a Beetleweight class combat robot, which are limited to three pounds (1.36 kg) or less. You can see some video of [Robert]’s previous Beetleweight robot named ‘Bourbon’, and we have featured what goes into the even-smaller Antweight class (one pound or less) in the past.

Simple “Computer” From The ’60s Now 3D Printed

Now is an amazing time to be involved in the hobby electronics scene. There are robots to build, cheap microcontrollers which are easy to program, and computers themselves are able to be found for very low prices. That wasn’t the case in the 1960s though, where anyone interested in “electronics” might have had a few books about ham radios or some basic circuits. If you were lucky though, you may have found a book from 1968 that outlined the construction of a digital computer made out of paperclips that [Mike Gardi] is hoping to replicate.

One of the first components that the book outlines is building an encoder, which can convert a decimal number to binary. In the original book the switches were made from paper clips and common household parts, but [Mike] is using a more reliable switch and some 3D prints to build his. The key of the build is the encoder wheel and pegs, which act as the “converter” between decimal and binary and actually performs the switching.

It’s a fairly straightforward build, but by working through the rest of the book the next steps are to build two binary encoders and hook all of them up to an ALU which will give him most of a working computer from long lost 1960s lore. He’s been featured recently for building other computers from this era as well.

Thanks to [DancesWithRobots] for the tip!