Opensource robotic arm

arm

[oomlout] has released this Opensource robotic arm. It is 5 axis, using cheap hobby servos. The total cost, including having it cut at thingaiverse.com is roughly $150. The plans include all the pieces, down to the servo controller. This means that you’ll have to supply your own microcontroller and programming. They do state “We can guarantee it is loads of fun to play with, and we think potentially very useful for more serious pursuits.” and we would like to test that guarantee. We’ve been keeping an eye out for this ever since the servo switch assemblies.

[via Hack a Day flickr pool]

Comments

  1. transhuman says:

    this is quite simply: awesome.

    keep up the good work oomlout

  2. cyrozap says:

    oooh… clear plastc…

  3. Tachyon says:

    Why would you pay to have a laser cut that plastic for you when you could do it yourself at home (the old fashioned way or with a DIY CNC machine of course). Mounting the servos like that rather than using linkages is a pretty inefficient design since each additional servo weighs on all the ones that came before it. A better idea is the old Armatron I think it was called, it had all the motors in the base with linkages going to all the arm joints.

  4. transhuman says:

    linkages would take more effort. Its easier to source stronger servos rather than designing the linkage.

    Granted the linkage is more efficient and is seen w/ industry level arms, the current design makes sense for something of this scale.

  5. jack says:

    Just a trick to sell you some laser cut at an incredible price
    “material and cutting cost about USD$150″

  6. Haku says:

    One of the problems with the Armatron is that because of the rotational nature of the linkages, when you move the wrist section up/down it causes the wrist to rotate.

    I’d like to see a miniature robot arm using the micro servos used for tiny R/C helicoptors, or a less bulky design that uses micro servos.

  7. Xander says:

    Robotic arms that make extensive use of linkages also run into significant lash problems which leads to poor accuracy. Resolving that requires higher quality parts, and all of a sudden we’re not really in “hobby” territory anymore.

    Which is not to say that it’s a bad idea, but I think you dismiss this one too easily.

  8. Toby says:

    Is there a video around?

  9. quig says:

    @xander

    We’ve been using one of these from Crustcrawler for a while in a class. Similar in design to the above with the servos in direct drive.

    I can tell you that linkages alone do not cause positioning slop. Positional accuracy suffers a lot from gravity at the extremities, even with springs to help with the load. The aluminum frame flexes pretty easily. Not sure how the acrylic would hold up. The servos also are to be blamed for the slop unless you’ve got good feedback (externally) on your position.

  10. anon says:

    stupid project

    ohhh i built an arm! look at me. Big shit. Can it give you a hand job? No? then i dont want it.

  11. Xander says:

    @quig

    Sure, linkages arent the only cause for slop. But it will tend to make most situations a little worse (accuracy-wise) and can be harder to fix than the other issues. Structural elements can be reinforced, better servos can be used, but only very tight tolerances and high quality bearings can help with linkage slop. Simply put, it’s even an issue in some industrial arms.

    Anyway, robots using linkages certainly do have their uses, I was just pointing out that they’re far from being automatically better than the design in this post.

  12. TJHooker says:

    This is like the configurations currently used in updated manufacturing plants minus the network interface. The big ones just use more power and bigger motors, and have stronger structure of course being made from casing and frame.

    The last one I worked with sent back real time data and fetched instructions from a server running embedded xp. It had some proprietary firmware using HTC++ and java on top of some risc chips.

  13. thefekete says:

    I’ve been messing around with an AL5D from lynxmotion (http://www.lynxmotion.com/Category.aspx?CategoryID=130) for a while. As far as slop is concerned, the main issue is with beam rigidity and weight causing the servos to sag.

    The main problems I had with it is the jerkiness of motion. I’m going to use it in a light automation role at my company (gphirrigation.com) for an intermediate step in assembly. The problem is, the parts aren’t welded yet. So if it jerks them around, the parts go all over the place.

    I ended up writing a few python modules to calculate servo values from a gripper position (x,y,z) and angle. Then it calculates intermediate positions for a sine wave like motion to that position.

    Once I get the thing nailed down, I’ll open source the software. If anyone wants it now, drop me a line at thefekete on google mail.

    Anyways, here’s some videos:

    It was about 3:00am, so I was a little spacey for the commentary…

    The arm has all digital servos except the gripper and wrist. The shoulder and elbow are 1/4 scale digital robotics servos. All in all I like it alot, and would recommend it to anyone with $600 lying around.

  14. John says:

    Hi, i’d like to talk with you about the arm. I’m in the middle of a project where i require some of this technology. I’m interested in purchasing it.

    Could you contact me at the given email address?

    Cheers,
    John

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