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Comment by smusamashah | Hacker News Reader

    A tile with ultrasonic array of transducers are provided as in the assembly to provide instantaneous friction control for any objects contacting or supported on the contact/upper surface. [1]

So that's what these tiny tiles are, something ultrasonic, not tiny wheels.

EDIT: Found some more explanation in a reddit comment. [2]

    Ultrasound vibration makes it slippery, then it has an X-Y pistons underneath. So it makes itself slippery when it wants to reset position, then makes itself sticky again when it wants to move you back into position. Now repeat this process to fast for you to tell anything is happening.

[1]: https://image-ppubs.uspto.gov/dirsearch-public/print/downloa...

[2]: https://www.reddit.com/r/BeAmazed/comments/19eef29/comment/k...

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Interestingly, on the video it appears as rotating wheels that change inclination: https://www.youtube.com/watch?v=68YMEmaF0rs&t=203s

From the close-up shots, you can clearly see them rotating and changing inclination.

By changing inclination they can control the contact surface of the rotating wheels and as a result control the direction of your movement. Very clever and simple but might be dangerous(you wouldn't want to have your pinky stuck between load bearing rotating wheels) and prone to tear and wear due to the high dynamic friction.

However, if there's actually a way to make it sticky or slippery with ultrasound then you can get away with a partial rotation back and forth while turning it sticky in one direction to push the objects in that direction and turn it slippery to reset its own position and get ready for another push. This probably will make it quite safe.

That's what I am still confused on how these discs look like wheels to people because lots of comments are saying that. All I see is discs changing angles and can't see them rotating like rotating wheels.

At 3:33 there's a close up and you can see dirt stuck on the edge of some wheels and it clearly goes around.

Maybe, the part that goes from slippery to sticky with ultrasound is beneath the rubber disks and when there's no load they just rotate freely?

It looks to me that they're spinning than rotating; in other words, rotate around an axis that is perpendicular to the ground, instead of parallel to the ground.

And because of this, the person above is stepping on the "spinning surface" (the "base" surface of a cylinder) of these tiny disks, instead of the curved surface like a normal wheel or some industrial conveyor wheels (as someone linked below, https://www.youtube.com/watch?v=PRS0Uj2WdpA ).

So in a sense, they're not "rotating like rotating wheels" despite being wheels/disks.

BTW, it looks like they also can adjust its axis angle slightly (less than 30 degree), which I imagine is also crucial to how it works.

That's what I mean. Rotating around their axis, which is spinning. Like the world rotates or spins. And by wheels I also mean disk, probably disks is more precise just as the spinning but really don't see why anyone would be confused when there's a video.

But anyway, thanks for improving my English.

(Text here is removed due to bad wording.)

To mrtksn: yeah I think your original post is pretty clear. But there are indeed other comments in this thread that are confusing the two.

Yeah probably but there's a minutes long video with close ups.

In my mental model its wheels attached in different way that rotate around an axis perpendicular to the ground. I call in wheels because moves the things around.

I'm really confused by the confusion. Isn't it obvious on the video that its cylindrical objects that can be considered thick disks and wouldn't all disks rotate on the round surface around the axis?

I also found the close up video to be self explanatory but I understand the confusion. People are thinking of it as multiple tiny treadmills that change direction rather than the spinning disc it actually is.

English isn't my first language but if it people were referring the motion as spinning instead of rotating and discs instead of wheels it wouldn't be confusing.

Yep, and by tilting the spinning discs/cylinders you can have omnidirectional control by changing which part of the edge of the rotating cylinder is in contact with the surface above it. You don't need the ultrasound thing posted in the other comment, that patent may be a different path they've also tried.

Yeah, I think this is right too. It'd also explain the sound.

Feels like a very mechanically-simple strategy, but hard to make durable / safe from fingers (and detecting "skin" vs "shoe" doesn't seem like something you can make foolproof) / that would hurt to fall onto.

Society says that progress goes forward. Toes? Not always.

Beautifully simple that it only has to spin the wheels one direction! I do imagine it has to stop though when the person stops walking.

The drawback of this is that it requires a firm contact point like shoes to work. You wouldn't want to walk in socks on this. You also couldn't have a performer lay directly on the surface and transport them across the stage, nor allow them to have baggy clothing near it. Running would be difficult from a balance perspective, not to mention holding a wheel at a particular tilt would require quite a bit of force if someone runs on it. It's going to have a very particular use case for Disney.

That's pretty gnarly. So the discs are basically doing little inchworming steps back and forth but never has to break contact by modulating the friction? Very much a bit of cleverness turned magic.

The one thing that I notice is item 726/Fig 7./PDF pg 10, it has "with the soles and attached/embedded ultrasonic transducers". Is that maybe a different or older envisioning of this system? His shoes seemed totally normal.

Just trying to wrap my head around how much the friction can be changed by vibration, like a solid-ish state fluidized bed. Don't know it both contact surfaces need to be vibrating.

That's a cute system.

Moving stuff around with controlled vibration is known. There's a cute trick where you drive a flat horizontal plate in three axes (X, Y, and rotate about Z). Sawtooth waveforms will move things around; the slow part of the sawtooth produces motion, and the fast part yanks the plate back to the starting point, breaking from static friction to weaker sliding friction. It's even possible, by using combinations of translation and rotation, to move multiple objects in different directions. The original research was funded by United Parcel Service. They wanted to take a table full of boxes, separate them, align them, and send them to a conveyor. Didn't work well enough, although someone did a chessboard demo where multiple pieces were moved around separately.

This is a similar idea, but at a finer scale.

> "with the soles and attached/embedded ultrasonic transducers"

That suggests doing this in the shoe, instead of in the floor. Different system. Disney might license that to Nike.

I can't see it for theme park customers. This system can make people fall down.

Performers, though...

Oh, okay, I see, in that alternative system, the tiles still move, but your shoe with transducers is used to adjust the friction.

The normal model of friction already has static vs moving friction. They just vibrate to switch between them.

Conceptually, the demo is showing a kind of omnidirectional conveyer. It’s a fun implementation of tech that has been used in shipping and fulfillment for a while.

https://youtu.be/HV2zh6ZDgUs https://youtu.be/XAokGOEjAFs

Companies tend to shotgun out a bunch of patent soup unrelated to actual working prototypes during R&D. The media latches on to the most interesting sounding thing they can find relating to a demo so you end up with “ai controlled space lasers” describing something that’s actually much more mundane.

That definitely doesn't look like something that could handle a human walking, and seems to be using a very different technique.

They must be vibrating the surface of those picks with ultrasound to modulate the friction. Pretty clever.

How does that work for moving the box then?

Sorry but if I input energy into the system by walking, and the holotiles input energy by producing ultrasound… how is this energy dissipated?

heat

Heat, and not very much

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