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Here's next week's video, early for Patrons. This one goes out on Tuesday 8th March.

Pretty happy with the mechanism in this one, there are still a few issues so I'll probably be attempting a larger version (with large 'little' wheels) at some point.


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Previews only

V2 Active Omni-wheel PREVIEW VERSION

Last time I tried to make a robot which balanced on one actively-driven two-axis omni-wheel. This wheel is driven by two motors in a differential drive configuration so it can drive sideways as well as forwards and backwards like a normal wheel. The design was mostly taken from a Honda Patent and Honda had showcased a proof-of-concept machine called the U3-X. The original design showed all the wheels around the circumference being driven together by a flexible shaft, but this is very hard to reproduce, so in my version I just attached all of the wheels to a central hub. Those wheels are driven by two hubs with rollers mounted on them at 45 degrees. This causes the wheels to rotate as the hubs are turned in opposite directions on either side. It worked well during low-speed testing, but I couldn’t get enough traction while accelerating fast to make the device balance. This was largely down to slippage between the rollers on the hubs and the wheels around the circumference. There’s also quite a lot of friction between all of the rollers and wheels, so it’s probably not very efficient. I’d also looked at another wheel design called OmBURo. This robot uses helical gears to translate the motion to drive the wheels around the circumference with a motor mounted in line with the main wheel axis. This design uses shorter flexible shafts so that each helical gear drives three wheels, although I guess more helical gears could be added, so there’s one for each small wheel. This time I decided to make something totally different, using a twisted belt to translate the motion from a central hub to the small wheels around the circumference. Links: https://www.youtube.com/watch?v=avtlx1-X3lo https://arxiv.org/pdf/2001.07856.pdf https://patents.google.com/patent/US8342270 https://patents.google.com/patent/US8758191 You can support me on Patreon or buy my Merchandise: *************************** Patreon: https://www.patreon.com/xrobots Merchandise: https://teespring.com/stores/james-bruton *************************** Affiliate links - I will get some money of you use them to sign up or buy something: *************************** Matterhackers 3D printing supplies: http://www.matterhackers.com?aff=7500 Music for your YouTube videos: http://share.epidemicsound.com/xrobots *************************** Other socials: *************************** Instagram: https://www.instagram.com/xrobotsuk Facebook: https://www.facebook.com/xrobotsuk/ Twitter: https://twitter.com/xrobotsuk *************************** CAD and Code for my projects: https://github.com/XRobots Huge thanks to my Patrons, without whom my standard of living would drastically decline. Like, inside out-Farm Foods bag decline. Plus a very special shoutout to Lulzbot, Inc who keep me in LulzBot 3D printers and support me via Patreon. HARDWARE/SOFTWARE Below you can also find a lot of the typical tools, equipment and supplies used in my projects: Filament from: https://www.3dfuel.com/ Lulzbot 3D Printers: http://bit.ly/2Sj6nil Bearings from: https://simplybearings.co.uk/ Lincoln Electric Welder: https://bit.ly/2Rqhqos CNC Router: https://bit.ly/2QdsNjt Ryobi Tools: http://bit.ly/2RhArcD Axminster Micro Lathe: http://bit.ly/2Sj6eeN 3D Printer Filament: http://bit.ly/2PdcdUu Soldering Iron: http://bit.ly/2DrNWDR Vectric CNC Software: http://bit.ly/2zxpZqv Why not join my community, who are mostly made up of actual geniuses. There’s a Facebook group and everything: https://www.facebook.com/groups/287089964833488/ XROBOTS Former toy designer, current YouTube maker and general robotics, electrical and mechanical engineer, I’m a fan of doing it yourself and innovation by trial and error. My channel is where I share some of my useful and not-so-useful inventions, designs and maker advice. Iron Man is my go-to cosplay, and 3D printing can solve most issues - broken bolts, missing parts, world hunger, you name it. XRobots is the community around my content where you can get in touch, share tips and advice, and more build FAQs, schematics and designs are also available.

Comments

Anonymous

Really enjoyed these episodes! I had no idea mechanisms like this existed and it’s fascinating seeing them put together (and taken apart)!

Jeffrey Cutler

How many printers are you running these days? You get so much done! Do you have to do a lot of maintenance on them? Might make an interesting video to do a "State of XRobots" about your equipment sometime.

XRobots

There's nine at the moment and they're pretty reliable so I don't have to do much. The rest of my work area is literally three Ikea tables ;-)

Richard Hackathorn

Amazing, once again! It really is "a completely new design" for driving those little wheels. Congrats...

XRobots

Thanks, yep - pretty happy it worked out. I'm wondering how many other solutions there could be.

Richard Hackathorn

I am sure that you will eventually enumerate them. I can see you riding that new fancy uni-cycle around the parking lot.

Anonymous

I'm genuinely impressed, really a neat design. Also for your endurance with the different not very well working designs.

Matt Keveney

Brilliant mechanism. Thanks again for sharing your research. Since you have an encoder on each motor, it seems that you could use the motor position on the fixed side of the wheel to tell which point of the lowest tire is touching the ground. Then plug the tire circumference at that point into your side-to-side motion computations. Might tame that irregular acceleration due to tapered-tires issue you mention. Sound feasible?

Thomas Messerschmidt

Looks like it is really coming along well. ! I had never realized how complex that toy motorcycle was. By the way, what brand and model of a 3D printer do you feel to be the most reliable? I am looking to replace the old one that I have now.

XRobots

Yes that would be possible - I'd have to scale the output as the wheels from the small to large part of the cone all around. The other issues is twisting in yaw which the toy motorcycle does as well, so I think 'straight' wheels would probably be a better solution.

XRobots

I've only ever used Lulzbot printers since 2012, so I've not really got any experience of anything else. They have some lower priced models now - the SIdekick range.

Dan Kramer

Fantastic work James. I could see your design being used in all kinds of other robots, not just one wheel. Imagine an R2 with a small pair of your wheels in each foot. It could drive sideways, spin in place, any possible direction would be an option. That would be a fun time making people at conventions wonder how it's done.

XRobots

Thanks, yep - that would probably be easier than three omni wheels at 60' to each other.

Anonymous

What an awesome design! I think it would be worth making the outer wheels uniform just for the satisfaction of seeing this work better! Maybe a faster balance loop or taller pendulum would help. Pivot control would be a nice addition if you could use acceleration of a flywheel to do that! And then lastly, aesthetics. I'm sure there's a few robots in pop culture to choose from or make up your own.

XRobots

My concern with 'straight' wheels is that the wheel isn't round enough in the other axis - I think it would have to get a lot bigger to get another eight wheels in but then the circumference gets bigger as well so I'd just end up with longer straight lines again. I think I might need to investigate short bits of flexible shaft like OMBuro, so I'm thinking about that.

alicetaur

You should head back to our SW droid side and build a non-canon star wars droid with your omiwheel give me D-O vibe

XRobots

I have another method for balancing on one wheel potentially coming up soon, so I'm going to decide what the best way to proceed is. I keep thinking about BB-8 again too ;-)

Anonymous

I just saw your reaction wheel video. That's basically the same idea I was thinking here, but you would slowly decelerate to try and use the higher friction of slower pivoting. It's kind of like trying to spin on an office chair without touching anything around you. It's tricky, but you can indefinitely spin on the office chair by flailing your arms around. 😆 weird, but fascinating how it seems like it should be impossible.

XRobots

A horizontally mounted reaction wheel would definitely make this yaw, but it would be ideal if it didn't turn by itself in the first place. I'm currently experimenting with a one wheel balancing robot which used only reaction wheels though.

Anonymous

That's awesome! The quality of this channel is just awesome. I like the stuff made here channel, but the satire is slightly annoying. Much nicer format here I think!