Rolly Bot Puts a New Spin on Independent Wheel Control

rolly bot

All of [Darcy]‘s friends were making wheeled robots, so naturally, he had to make one too. His friends complicated theirs with h-bridges and casters for independent wheel maneuvering, but [Darcy] wanted something simpler. A couple of 9g servos later, the Rolly Bot was born.

Rolly Bot is self-balancing because of its low center of gravity. Should it hit a wall, the body will flip over, driving it back in the other direction. The BOM comes to a whopping $10, and that includes continuous rotation servos. It does not include the remote control capability he added later, or the cost of the CNC you would need to completely replicate this build. He even made a stand so he could test the wheels during programming.

[Darcy]‘s code is on his site along with some pictures of another version someone else built. Watch Rolly Bot roll around after the jump.

How would you make this build even simpler? Tell us in the comments.


  1. gjiij says:

    How is this a hack? Wait… “Filed Under: Arduino Hacks”. That explains everything. I really need to write myself a plugin that will hide all this arduino/raspi crap.

  2. janostman says:

    “Should it hit a wall, the body will flip over, driving it back in the other direction”

    No, it won’t.
    The direction is still the same.

  3. LouLou says:

    I’m loving the single spoke wheel way more than I should.

  4. To make it simpler – use CDs or DVDs for wheels – it been done before

  5. Jack says:

    Can I hate Arduinos irrationally, too? I want to be in the cool kids club.

  6. Jon says:

    A good way to improve this would be to print everything within the diameter of one wheel, maybe by making each wheel have half of a “big diameter” and half of a “small diameter”. Make it laser-cuttable within a single A4/letter sheet of paper.

    • Darcy says:

      The layout of the parts on the raw material is an interesting area to explore. I went with six inch wheels to make sure it could fit a bread board and lots of room to get your hands in through the spokes to work on it…

      As things stand, there is a fair amount of wasted material. So that invites more parts. I added a kickstand. Perhaps a handle next. I noticed people don’t know how to pick it up. Or parts to assist with fixing the battery.. or perhaps some arms to have sensors away from the board.

    • Can you explain the biz about the wheel’s half of a big diameter again?

  7. Jack says:

    The same thing in big.

  8. John says:

    Can someone add inertia compensators to stabilise the load?

    • Darcy says:

      Thanks for the comment! What a great idea. Actually, the program I posted can make smooth transitions. I only implemented one (smooth stop). But I think that’s a great area that the programmer can experiment with.

      This weekend at our local arduino meetup I might work on a bunch more smooth transitions. In the mean time I have chosen two servos that don’t match well. I’m debating if I should make some sort of array to correct the power or just find two servos that match…

      • FlippyBits says:

        Can you use your CNC to burn encoder stripes into the wheels so you can use IR sensors as feedback?

        • I guess that could work. One could print an encoder wheel on a printer too and then stick it on…There’s be a lot of noise with all that swinging of the gondola though…..

          wait, that might not matter… so as it swings it creeps forward and back a bit.. might not matter…

          I wonder if the two spokes would work?

  9. Lars says:

    Would it be possible to add a $1.5 line follower sensor?

  10. pieter says:

    Did you see this one. Each wheel driven separately and XXL size:

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