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A Trio of Balance Bots — Parallax Forums

A Trio of Balance Bots

Martin_HMartin_H Posts: 4,051
edited 2014-12-30 07:16 in Robotics
Here's a Stuart platform with a touch panel for feedback.

[video=youtube_share;j4OmVLc_oDw]

Nice but I think this is overkill as it requires six servos, and here it's being done with two:

[video=youtube_share;uERF6D37E_o]

Here's a beginner project that scales the problem down to one dimension, but is creative and interesting nonetheless:

[video=youtube_share;r5VaAP09BPA]

Comments

  • ercoerco Posts: 20,257
    edited 2014-12-14 18:56
    Those are all FABULOUS! Never seen a Stuart platform. A must-build! Great damping (PID props) in the first two videos, and a great effort by the young man in the last one.

    My favorite post in Robotics in ages. Well done, Martin_H! Keep 'em coming!
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-12-15 01:37
    Very, very impressive ! ! !

    It would be interesting to take it to the next level and see how the table could interact with a bouncing ball.
  • Martin_HMartin_H Posts: 4,051
    edited 2014-12-15 04:33
    Glad you both liked them. There's a neat difference between the Stewart platform and the other balance table, a Stewart platform can move up and down as well as tilt. So it's possible to bounce a ball on one.
  • ercoerco Posts: 20,257
    edited 2014-12-15 10:26
    This related video shows how the 6 servos (actuators) in the first video make the Stewart platform a full motion simulator, not just a 2 DOF system.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-12-15 10:30
    Martin_H wrote: »
    Glad you both liked them. There's a neat difference between the Stewart platform and the other balance table, a Stewart platform can move up and down as well as tilt. So it's possible to bounce a ball on one.

    Excellent point. So it can dampen the bounce. That might inspire some one to build a Propeller solution as the next step forward.
  • ercoerco Posts: 20,257
    edited 2014-12-15 18:35
    Before & After (a la Wheel of Fortune):

    A Martha Stewart Platform Bed: http://www.marthastewart.com/998801/how-make-wooden-platform-bed-part-2#998801
  • Martin_HMartin_H Posts: 4,051
    edited 2014-12-29 09:58
    The forum software is giving me grief uploading this, so here's a link instead:

    http://ppl.ug/jFSaNjODWbo/

    The blue servo brackets and right angle brackets are from Gordon's website, the ulinks are from Tamiya, and the plywood is from the local craft store. Things went together quickly once all the cutting and drilling was complete.
  • ercoerco Posts: 20,257
    edited 2014-12-29 10:39
    Daddy like! But I suspect you'll need longer servo arms for a bigger range of motion.

    Propeller controller? Big coding job to make sure your servo pairs aren't fighting each other. Cool project!
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-12-29 11:09
    erco wrote: »
    Before & After (a la Wheel of Fortune):

    A Martha Stewart Platform Bed: http://www.marthastewart.com/998801/how-make-wooden-platform-bed-part-2#998801

    @Erco -- Why Martha Stuart beds in this thread? Really bizarre. (OK, the first device is a Steward Platform.)

    Where did Martha learn to make beds? In jail?

    Use two sheets of 5' x 9' ping pong table plywood, not 4 sheets of 4' x 8'. You can get a platform up to Queen size.
  • Martin_HMartin_H Posts: 4,051
    edited 2014-12-29 12:05
    erco wrote: »
    Daddy like! But I suspect you'll need longer servo arms for a bigger range of motion.

    Propeller controller? Big coding job to make sure your servo pairs aren't fighting each other. Cool project!

    What I can do if the arms need to be longer is flip the servos around and make arms from hobby plywood. I've already got C IK software that's parameterized so I would only need to plug in some new values.

    I do plan to use the Propeller and SimpleIDE since I have all the code in C. It's definitely a big coding job, even with the headstart I have from previous IK projects.
  • ercoerco Posts: 20,257
    edited 2014-12-29 13:11
    Loopy Byteloose wrote: »
    (OK, the first device is a Steward Platform.)

    My WikiLeaks sources say Stewart...

    http://en.wikipedia.org/wiki/Stewart_platform
  • ercoerco Posts: 20,257
    edited 2014-12-29 13:14
    Martin_H wrote: »
    What I can do if the arms need to be longer is flip the servos around and make arms from hobby plywood.

    That's starting to sound like a lot of work! Another option is to move the brackets on the top platform closer to the center, as shown in the very first video you posted. Half the radius there yields twice the travel.
  • Martin_HMartin_H Posts: 4,051
    edited 2014-12-29 17:42
    erco wrote: »
    That's starting to sound like a lot of work! Another option is to move the brackets on the top platform closer to the center, as shown in the very first video you posted. Half the radius there yields twice the travel.

    That might work, but I was shooting for an equilateral triangle for the length of the rods versus their separation on the top disk. This is roughly in line with other Stewart Platforms I've seen. But we'll see how it goes. In the meantime there's a bunch of C++ code to write.
  • ercoerco Posts: 20,257
    edited 2014-12-29 17:59
    I have no doubt that you will get it working. A must-see!

    I'm impatient. How about giving yourself a midnight New Year's Eve deadline? Pleeeeeeeeeeeeeez? :)
  • Martin_HMartin_H Posts: 4,051
    edited 2014-12-30 07:16
    erco wrote: »
    I'm impatient. How about giving yourself a midnight New Year's Eve deadline? Pleeeeeeeeeeeeeez? :)

    Wow, you're a tough customer. Unfortunately family commitments will prevent me from working on this until Thursday night.
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