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Rhymes With "Biscuit": P1-powered rolling-ball sculpture — Parallax Forums

Rhymes With "Biscuit": P1-powered rolling-ball sculpture

This is a piece I've been working on for too long; I'm hoping I can declare it done now: 3:30 YouTube video

In a typical rolling-ball sculpture, the balls are raised by some mechanism and then they roll down various interesting routes. Rhymes With 'Biscuit" is a little different in that the balls roll around and round without going up or down (very much).

There's a P1 inside controlling five servos. Hope you like it!

Comments

  • VonSzarvasVonSzarvas Posts: 3,335
    edited 2023-04-17 07:06

    Rhymes With "Biscuit" , and very Artistic!

    Congratulations on a wonderful achievement.

    Super impressive; gifted me a big smile to lift the start of the day !

  • Excellent! I couldn't quite correlate the servo noise with anything on the model until you zoomed in on the track switch, and then kept getting a little nervous hoping it wouldn't lose sequence but it never did. Really cool display!

    Cheers,
    Jesse

  • That's really cool! Still trying to decipher the name, though.

    Doc

  • @mpark said:
    This is a piece I've been working on for too long; I'm hoping I can declare it done now: 3:30 YouTube video

    In a typical rolling-ball sculpture, the balls are raised by some mechanism and then they roll down various interesting routes. Rhymes With 'Biscuit" is a little different in that the balls roll around and round without going up or down (very much).

    There's a P1 inside controlling five servos. Hope you like it!

    Hi, that is nice!
    If You like, you could share a little bit, how it is done. For example I would like to know, how you detect the position of the balls. :-)
    Christof

  • I would like to know, how you detect the position of the balls.

    That has crossed my mind too but maybe it's not necessary... I'm still thinking about it.

  • mparkmpark Posts: 1,305

    Thanks for the nice comments!

    If You like, you could share a little bit, how it is done. For example I would like to know, how you detect the position of the balls. :-)

    Well, to let you in on a little secret, RWB has no idea where the balls are. It's completely open-loop. The up-and-down movements of the four track segments produce a kind of traveling wave. If you start a ball at the right time with the right speed, it will catch the wave and be propelled. It's even self-correcting (to a point): a ball that's a little behind the wave gets accelerated, a ball that's ahead gets slowed down.

    In the 1- and 3-ball cases, there's never more than one ball on a track segment and the system can be very stable. When five balls are in play, however, each segment will have two balls at some times, which makes things trickier. I did some simulations and was pretty optimistic, but I was still amazed to actually see five balls working in real life!

    There's a bunch of parameters to tune the thing, so there's a Parallax wireless card inside so I can tweak numbers via a web interface.

    Happy to answer any more questions.

  • Great!

    Do you really need the switch in the middle?
    I expect the balls keep rolling in there directions.
    Or is the track-width who is making mechanical noise

  • mparkmpark Posts: 1,305
    edited 2023-04-17 19:24

    My first prototype did not have a switch (https://youtu.be/PTdX74ys4gQ), so I could have (and probably should have) avoided the complications of adding a switch, but where's the fun in that?

  • ElectrodudeElectrodude Posts: 1,644
    edited 2023-04-28 13:44

    Lemniscate

    (It's been a week and a half now and nobody else seems to have guessed yet, unless I missed something on a Live Forum.)

  • mparkmpark Posts: 1,305

    Yes, finally! Well done, @Electrodude!

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