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Leadscrew-Driven Joints in Arm — Parallax Forums

Leadscrew-Driven Joints in Arm

ercoerco Posts: 20,256
edited 2012-02-02 16:45 in Robotics
Crude but effective! Fast forward to the 1-minute mark to avoid silly cartoon: http://www.youtube.com/watch?v=GdTX1fYzmYM

These leadscrew joints are bound to be a lot more accurate and durable than your average hobby servo joint on a homebrew robot arm. Probably stepper motors used here.

Daddy like. Could mod regular servos to do this. Make a continuous rotation servo out of it to drive the leadscrew, then mount the pot externally at the joint to measure the angle. Hmmm...

Duane! Martin_H!

Comments

  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-01-30 13:07
    erco wrote: »
    Crude but effective! Fast forward to the 1-minute mark to avoid silly cartoon: http://www.youtube.com/watch?v=GdTX1fYzmYM

    These leadscrew joints are bound to be a lot more accurate and durable than your average hobby servo joint on a homebrew robot arm. Probably stepper motors used here.

    Daddy like. Could mod regular servos to do this. Make a continuous rotation servo out of it to drive the leadscrew, then mount the pot externally at the joint to measure the angle. Hmmm...

    Duane! Martin_H!

    To think, earlier today I actually wondered if I should start adding background music to my YouTube videos. Now I know the aswer will be NEVER. You could have at least warned us about the awful music. (Not that the music itself was so bad, it just was way out of place in a robot arm demo.)

    I think using an external pot with a continuous rotation servo has been patented by the guy at Servo City as well as adding a gear instead of a servo horn to a servo. Oh, no! I hope he doesn't see the S9254 servo thread. I show the gear I attached to the servo! Okay, enough about bad patents.

    The threaded rod looks like it's practically in the center of each arm segment. The arm will likely have trouble reaching "into" things. I don't see one in my near future.

    Isn't this too similar to a worm drive for your liking erco?
  • ercoerco Posts: 20,256
    edited 2012-01-30 13:18
    XLNT memory Duane! While I am no fan of worm gears, leadscrews are more appealing. Especially if they are of the ground leadscrew/recirculating ball type... :)
  • Martin_HMartin_H Posts: 4,051
    edited 2012-01-30 13:24
    The lead screws are an interesting idea, but the robot is even shakier than some Lego Technic arms I've built. For raw accuracy I haven't seen anything that beats this guys robot arm:

    and it uses servos with custom sensors.
  • ercoerco Posts: 20,256
    edited 2012-01-30 14:24
    Nice lead threader, wow that's a lot of hardware for that one task. I gotta have more bang for the buck. :)

    I'll be happy just stacking wooden cubes and stacking my wooden robots for ~$30 total, including the uC!
  • schillschill Posts: 741
    edited 2012-01-30 15:03
    From Radio Electronics, August 1980: A robot with threaded-rod based arm.

    http://www.bot-thoughts.com/2010/01/unicorn-1-arm.html

    http://www.scribd.com/Lima-1/d/3231860-Unicorn1-Robot-Articles-in-Radio-Electronics-

    I wanted to build one back then (the arm part) but didn't really have the means.
  • davejamesdavejames Posts: 4,047
    edited 2012-01-30 15:19
    At 5:40...after all the wiz-bang screws, motors, and linkage...input is via an Atari 2600 game controller!

    Gotta love it!
  • ajwardajward Posts: 1,130
    edited 2012-02-02 16:45
    I'd been thinking about something like this for a while. I picked up some brass and aluminum stock a few weeks back and began cad'ing some of the linkages.
    Just finished a plastic mockup of one of the links today. Not terribly happy with the result, but plastic is cheap! :-)

    Amanda
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