Sortarm Project Log #3

November 20th, 2010

It’s been a long time. But finally some great news!

So I’ve managed to finish the whole structure of the arm and I ran into some trouble, a couple servo gears melted because of the load. From now on, I’m using only metal gear digital servos. Already replaced two, the others seem to be doing fine, but their not as stable as they could be, so I’m going to replace them soon.
After finishing the structure I’ve started to code the example applications. Initially there we’re supposed to be three demo apps:

  1. IrcArm – The Arm would have an IRC client, and it would obey the commands of users in a certain channel
  2. PS2Arm – The Arm would be controllable by a ps2 mouse.
  3. HIDArm – The Arm would be controllable by a USB HID gamepad

I’ve finished the IrcArm example and tested it live with GZORG and a couple of friends from freenode using the help of ustream so that users could actually see what they were doing with the arm :]. After that I’ve made the PS2 example which you can see in the video, but I haven’t decided on doing the HIDArm example. Right now it all depends if opendingux (a linux kernel for the Dingoo handheld gaming device) will be adding HID support for the device to act as a usb gamepad. If they, won’t I don’t see any reason to make the HIDArm example.
So the cad design modification and publication is next in my scheme, I’ll probably release these design without testing them myself so be sure to watch out for an “ALPHA” label, I’ll remove it once I test the designs myself. After that I’ll probably clean up the example code, release all of them and move on to the main Sortarm project, maybe make a Little breakout board for the mbed in between.
And finally I’d like to say thanks to Oleg of Circuits @ Home for the inverse kinematics function, to zear, z_man3007, ladderjack and GZORG for testing out the IrcArm.
See you next time!

Posted by mindw0rk
  1. […] and filmed a little demo for the Sortarm, the PS2 arm specifically. You can read more about it here Apart from GZORGs shaky hands and my indecipherable voice, the video was a pretty good success. […]

  2. Julius Ĺ ustarevas

    nice… very very nice..

  3. Greg
    1:55 pm on February 3rd, 2011

    Great project!
    We build some (manual control) robot arms using metal gear servos too (for Science Olympiad). We had a similar problem that I notice in your video, the stiff positional control of the servos leads to a lot of jerkiness in the arm motion due to the inertia of the arm.
    An improvement would be to design a different servo controller inside the servo itself (the small PCB inside the servo), to change the current to the motor more slowly and carefully, and to tune this loop to the mechanical time constant (mechanical resonance) of the arm mechanics. (The new servo PCB could be inside or outside the servo case.. if outside you modify the servo to bring out the motor and potentiometer feedback wires)
    Have you thought about doing this to get smooth arm motion?

  4. mindw0rk
    5:00 am on July 11th, 2011

    Hey Greg,

    Sorry, that my response is 4 months late, I somehow managed to overlook your comment. Thank you for the advice! You see, the servos that I initially used for this project were extremely cheap ones. A mistake I have learnt from, rev 2 of the arm should be coming up in 3 months time, I revised the design, parts and will see how things go with everything redone from scratch. As for your approach to solve the problem is rather complicated, though it does make sense and I’ll leave it as my second option if something goes wrong. Oh and hope you and your team do/did great in the science olympiad! Cheers!

  5. 10:21 am on May 20th, 2013

    Superb, what a website it is! This website gives valuable facts
    to us, keep it up.

  6. malhar kurange
    5:55 am on June 17th, 2013

    hey i am studying mechatronics diploma and i was working on a project, which needs some help. i just needed the dimensions of your sortarm as i was planning to build it. please do reply as soon as possible.. thanks

Leave a Reply