Mecanum wheel | Hacker News Reader

Mecanum wheel

en.wikipedia.org

169 pointscurtis50 comments

Intralox belts are sold under all sorts of names...mecnasort and tabletronix were a few older ones I recall when I first started as an industrial machinist 15 years ago. The problem with intralox is theyre relatively sensative to weight and if one row or cluster of links goes down, it can very quickly take the entire table down.

Mecanums on the other hand are incredible. If you need to service a four thousand pound part, you can drag it around on a table of mecanums like its a childs toy. Mecanums pods are even individually addressable, so you can get an email or alert to exactly which one is under too much load, or failing.

You referring to intralox's ARBs?

These are so damn cool. My old FIRST team wanted to use these but the lack of traction was a real problem. Great for moving heavy & slow, not so great for fast turns (even with relatively low center of gravity).

My FIRST team did use them and loved using them. For our use case it was great

That's awesome! I think the year we considered it was "Aim High" (https://en.wikipedia.org/wiki/Aim_High) or one of the adjacent years. We used our previous year's robot as a test bed and found regular wheels could too easily push our Mecanum wheel robot out of the way / knock it off balance. Do you remember which competition you used the wheels? What did you end up using for a driver control layout?

Same problem we had this year (Power Up). We built two drive bases, and when we tried the Mecanum one against our 2017 robot, it just got pushed right out of the way. No friction.

We used it for Steamworks (https://en.wikipedia.org/wiki/FIRST_Steamworks), where speed was a priority for our light robot. Unfortunately, defense was utilized to our detriment.

Where does one get Mecanum wheels of a size (durability) suitable for robots?

Andymark (http://www.andymark.com/Mecanum-s/53.htm) sells mecanum wheels durable and large enough for some robots.

Thanks. I think I searched years back and came up with very small hobby wheels. It looks like there are a lot more options now.

I played in 2002 -- team 278.

https://en.wikipedia.org/wiki/Diabolical_Dynamics

The field was carpet, and we put treads on the wheels for traction. Our most common problem was blowing our fuse due to using drill motors for the drive train! (Low speed, high torque, high power draw.) But until that fuse blew, those goals moved where we wanted them to!

It was our rookie year this year, and after watching how great some other teams were with mecanum wheels, we decided to look into them over the summer. To be honest, I'm just excited to try driving them :)

Yup, like the article notes, we use these on ships where there are often times when you need to transport large pallets of material through a maze of passages and you often don't have enough reserved deck space to accommodate the turning radius of a normal pallet jack or 'walkie'. Material Handling Equipment with Mecanum wheels are omnidirectional (no turning radius), so you can transit heavy/bulky cargo through very tight passageways that would otherwise be virtually inaccessible.

Here's a forklift with mecanum wheels (1 min)

https://www.youtube.com/watch?v=ZW3OBb_b89k

Neat! I built a little mobile robot that uses omni-wheels[1], a related style wheel. Build report here[2] (forgive the lousy website, I'm a mech guy just starting to learn software)

The wheels allowed some neat driving tricks, but it also made it really difficult to drive in a straight line. You don't get the normal tracking behaviour that wheels give you, and differences in traction from wheel to wheel also tend to distort your course. Adding a gyro for use in a closed-loop angular control system really helped this a lot.

[1] https://en.wikipedia.org/wiki/Omni_wheel [2] http://willbeattie.ca/Projects/Twitch/Twitch.html

Reminds me of Intralox belts[0], which are used extensively in manufacturing and warehousing. Intralox belts are conveyor belts made of tiny wheels pointed 90 degrees (usually) off of the direction the belt is traveling.

[0]https://www.youtube.com/watch?v=tqLYhhV7u7Y

Demo: https://www.youtube.com/watch?v=Ne09Y72zW_Y

When reading the wikipedia page I was surprised to learn that: "In 1997, Airtrax Incorporated and several other companies each paid the US Navy $2,500 for rights to the technology, including old drawings of how the motors and controllers worked, to build an omnidirectional forklift truck"

This was more than 20 years ago, but $2,500 seems on the low end for a usage-license. This patent is pretty interesting after all. Does anyone have any knowledge in this area? Is that average for these types of patents, or is the Navy giving it away for cheap to incentivize new innovation?

'97 was 25 years after the original patent was filed, so the original patent was well expired.

I would guess that what they were buying from the Navy were literally just the implementation notes, because even if the patent covers all of the original, key, patent-able ideas, it can still be a bitch to go from that to an actual working implementation.

This video explains it well:

https://www.youtube.com/watch?v=O7FbDy-gE70

It's a pity that they got the orientation of the rollers wrong.

The wheels should have been oriented either like this:

      ___
  [\]|   |[/]
     |   |
  [/]|___|[\]

or like this:

      ___
  [/]|   |[\]
     |   |
  [\]|___|[/]

instead, they managed to mount them like this:

      ___
  [/]|   |[/]
     |   |
  [\]|___|[\]

Does that explain why it's so wobbly when going sideways, or is it always going to give some wobble on a very light object like that?

> Does that explain why it's so wobbly when going sideways

Yes. Check out the smooth movement of a vehicle with properly oriented wheels:

https://news.ycombinator.com/item?id=16994136

Thanks for pointing that out, might be unrelated but I wasn't impressed by the video because it didn't seem to work right, i.e. the robot didn't travel straight, just did a series of small turns to go in one direction.

The only correct configuration is the middle one. If you have the rollers making an X then the vehicle is unconstrained about Z.

Could you explain that deeper?

I see where they're going now that it's pointed out.

The X pattern defines a single point of control where the lines cross, while the 'diamond' pattern creates (roughly) four outer lines of contact and thus for a complex terrain beneath allows for better control in the location on top of that uneven field.

Theyve been made for lego robots as well: http://thekidshouldseethis.com/post/lego-mindstorm-mecanum-w...

If the original patent was November 1972, then surely it had long-since expired by 1997, which then begs the question of why it was necessary that: "In 1997, Airtrax Incorporated and several other companies each paid the US Navy $2,500 for rights to the technology"

Is there something about US patents not mentioned in https://en.wikipedia.org/wiki/Term_of_patent_in_the_United_S... ?

I'd expect it's a submarine, which are mentioned in the page you link, https://en.m.wikipedia.org/wiki/Submarine_patent -- largely only a thing in the USA's former first to invent system AFAIK.

It seems there is some complexity and other patents involved.

From their SB2 form:

A form of our Omni-Directional technology was originally patented in 1973 and was sold to the US Navy. We secured a transfer of this technology from the Navy in 1996 under the terms of a CRADA agreement (Cooperative Research and Development Agreement) and we have worked since that time to commercialize Omni-Directional products. We received 3 patents regarding the "redesign" of the wheel. In addition, we have a license agreements for the algorithms used to control vehicular movement, and a patent for this technology has been applied for. (...) The patent for the Omni-Directional wheel expired in 1990.

https://www.sec.gov/Archives/edgar/data/1081372/000101376207...

Probably improvements later on

If I describe an API and the algorithm used to implement it (a patent) that doesn't necessarily mean the source code I used isn't still useful (a copyright).

They were paying for the Navy's implementation of the technology - a bunch of copyrighted notes, drawings, and details - rather than starting from scratch. They were not paying for the idea of the technology (because the patent had expired).

Plenty of options here if you're interested: https://www.thingiverse.com/search?q=mecanum&sa=&dwh=585aec7...

Shows no results found.

go to https://thingiverse.com, search for mecanum. Done!

Airbus uses them to move A380 parts around their factory: https://www.youtube.com/watch?v=RZ_8xhCi72w

The alternative is using Omni Wheels mounted at 45 degrees, which lets you do translations without rotations.

https://en.wikipedia.org/wiki/Omni_wheel

Liddiard wheels are a bit of an iteration on this concept: https://www.youtube.com/watch?v=jas_y1cUndI

They seem much closer to omniwheels, and largely inferior for the mecanum's actual purpose: if you check out youtube videos, mecanum-equipped heavy lifters (e.g. KUKAs on the A380's assembly line) are way more reactive, fast and flexible despite being humongous.

Is it just me, or do the physics of the tire not make sense here? I'm clearly missing something, given that they have a working demo.

But it seems to me that the surface area of the tire is getting stretched and squashed as it spins horizontally.

Yep you are correct. It seems like the tires would have to consist entirely of a fairly elastic material, preventing the use of banded or radial designs.

the mythbusters had a forklift or something with these wheels I believe

Yeah, they had an ATX-3000 Sidewinder.

http://www.vetexinc.com/vehicles/sidewinder.html

Has anyone looked into these for an Omni directional treadmill?

Smarter every day had video recently about it used in VR company

how well do they roll on tarmac?

Imagine an electric car that can park and drive in tight spaces.

Neither surface nor weight seem to be issues: they're used for multisurface forklifts, they do fine on grass or dirt or sand, they're used for heavy lifters. They're expensive and heavy though.

But I'd be more worried about operating speed, mecanums have maybe 60~70% of the traction of a regular threaded wheel, and probably behave much more poorly at high speed.

On a regular car, you're probably better off with auto-parking (the tech is getting pretty damn reliable, it's just a question of having it trickle down from the luxury segments) or even just parking assist.

I think my nephew's toy robot puppy moves around on these.

That's one the few cases where it made sense to [puts sunglasses on] reinvent the wheel.

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