Ball and plate doohickey

ball table

So, if you were wondering what [Kenn Sebesta] was working on that needed yesterday’s hack, this is it. The plate can maintain the cue ball in its current position or make it travel an arbitrary path like a circle or figure-eight. It can also avoid obstacles placed on the plate. Kenn has documented his project thoroughly and covers many of the problems he faced along the way, like how to find the ball in the webcam image. Like most quality thesis projects, it’s constructed out of LEGO.

UPDATE: Now with video!

20 thoughts on “Ball and plate doohickey

  1. Thanks! Otherwise, yes, I know that there are lots and lots of errors. I tried to update my site, and either Pages ’06 or my the new UK websever just wreaked havoc with the HTML. I don’t know what’s up, nor why I can’t see the errors on my computer, but I’m working on it.

    Soon I will link to a video of the table in action. Come back in an hour.

  2. doing this in one axis on a tilting rail was the bread-and-butter of controls classes at my college…kudos for doing the much harder 2d version! now, what about building levels like marble madness, with pits and ramps etc? ;)

  3. I can understand some of it. Three years of french didn’t go to waste. A very nice project. Consider changing the platform to a Labyrinth game and you could have it self solve. Just a suggestion. Nice work.

  4. “Three years of french didn’t go to waste. A very nice project.”

    That’s okay. My limited French skills were shown off when someone asked what use this had, and I said, “So when you throw a lightswitch, Paris doesn’t fart.”

    We had considered labrynth, but then let it go because it was too easy to program and too hard to build. Getting it to roll to a certain spot with a certain orientation was deemed “more scientifically interesting”.

  5. That is really, really impressive, especially with the obstacles! Wow.

    Can you explain what happened when the ball fell off the platform? How does the computer respond to that, when it can’t find the ball, and how to you start the program back up again when you are placing the ball back on the platform?

  6. “Can you explain what happened when the ball fell off the platform?”

    Matlab, matlab, and matlab. When I changed programed trajectories, matlab would hesitate, and all too often that hesitation was fatal.

    “How does the computer respond to that, when it can’t find the ball, and how to you start the program back up again when you are placing the ball back on the platform?”

    At the time, it didn’t respond too well, but now I’ve programmed it to simply go to sleep if it doesn’t find anything that even remotely resembles the ball.

    To stop it, I just hit CTRL-C, and to start it I just ran the command again. Now, I can more or less throw the ball on the table and it’ll catch it. Even better, I can stabilize one pool ball, careem another pool ball into it– knocking off the first– and the computer will simply stabilize the second ball!

  7. “That is awesome man, I understood most of the french since im from canada.”

    Then I apologize to you for my hamfisted-ness with such a beautiful language. After 23 years in Kentucky, I never learned to talk like a hillbilly, so 4 years in France has done surprisingly little for my accent.

    “By the way, how long did that take you?”

    Well, either 2 days or 6 months, depending on how you count it. Research is spending half a year to figure out which week you should have shown up to work. So the total time required to do this from scratch again is really quite short. (I’ll give the well-commented matlab code to anyone who wants it.)

  8. nice. i’ll have to build one. drive my cat crazy. i like driving people crazy. if u havent noticed. |-|4|>|>y |-|4|>|>y 24|)

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