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Thread: Malum IK

  1. #31

    Re: Malum IK

    So much still to do. Also, broke another tap in the deep holes in the magazine bottom, so had to re-do that one, too.

    But this gun seems to mostly work, and not jam very often.

  2. Re: Malum IK

    Well, at least you are only a short drive away still, right? So you don't have to burn a travel day like most of us!

    Click image for larger version. 

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    I already had to pack up...

  3. #33

    Re: Malum IK

    Yes I have that going for me. Pop on home to turn out another bracket on the mill in between matches :-)

    Gun, magazine, electronics all mounted. Still need to figure out how to mount video and make some brackets for the front/back scoring panels. If I don't crash and burn, I may actually make it!

    Leaving all software improvements for the in-between-bouts time ...

  4. #34
    Join Date
    May 2010
    Princeton University
    Rep Power

    Re: Malum IK

    That all aluminum gun assembly is a thing of beauty.

    Props on a nice build in two weeks.

  5. #35

    Re: Malum IK

    Ready or not, I'll be there tomorrow.

    The magazine feeder motor has an encoder on it, wired to my Teensy, but no software. Maybe I'll work on that tomorrow between bouts.

    I grew tired of hand tapping and finally worked up the courage to try my M2.5 thread mill. Dialed it in in Fusion, set the height in the mill, started the program, and .... flawless threads! The Fusion CAM rapids to right above the hole center for the thread program, so I thought for sure I'd crash and bust the expensive bit, but it just shoved a 1.95mm cutter down a 2.05 mm hole and started threading it bottom up. Groovy! (Sandvik-Coromant tools are high quality, but usually > $200; I found this listing for $35 on Amazon a few days ago and got it; it's now back over $200. Bill says I paid $35 though, so yay glitches in the system!)

    I still haven't written the code to aim with IK; right now I can walk and turn and actuate the gun. Haven't even fired a single shot through the fully-assembled system. But the night is young!

  6. #36
    Join Date
    Sep 2010
    Rep Power

    Re: Malum IK

    The night is young indeed! I just fixed my wireless camera so it no longer overheats every few minutes...

  7. #37

    Re: Malum IK

    Each piece of the gun system was tested separately, but in integration, something causes a BB jam that doesn't clear up :-(
    There's plenty of possible pinch points on the inside; I removed some in design, but I also rounded corners which I now realize ended up creating more pinch points.
    Trying to fabricobble some kind of insert to avoid those. Maker Faire doesn't open until 10am, right?!

  8. #38

    Re: Malum IK

    Good news: Advanced composite-metal fusion additive machining solved the gun jamming problem, just in time to place for the sharpshooting qualifiers!

    (Some people will just say I just put on a glob of hot glue inside the aluminum magazine bottom. Philistines.)

    More good news: I could actually shoot and hit some things while aiming with the body! The floating barrel is not yet tuned for peak accuract, though.

    (Some people will say that my "floating barrel" is just "jammed in there, hanging on by the bucking," but they clearly don't have good marketing sense!)

    I jammed in the code for body aiming while standing still, rotating the target IK points around the center of the mech based on control input. I yawed left and right, and it worked fine, but was mirrored from what I wanted (easy fix.) I pitched up and down, and the mech rolled left/right around the center. Turns out I flipped my X/Z in the math :-)

    Good news: I figured out that I could increase my step rate 50%, which leads to faster mech movement!

    Bad news: I figured this out after we had already done the "speed run" qualifier.

    Ambivalent news: I ended up seeded in the "veteran" division, meaning I probably won't place this year. So many good teams, so many cool mechs! And I have zero practice actually driving mine or knowing what to do in a fight ...

  9. #39

    Re: Malum IK

    I beat Odin! I lost against '99!

    One or the servos lost its position, and curled in on itself during that second fight today, so I was walking three-legged. Checking afterwards, I can't compensate in software, because the off-ness drifts (I saw up to a quarter turn off.)
    Likely the hall position sensor magnet has come lose?
    And, because it kept driving itself into interference, it overheated the motor, so it's now a "sticky MX-64" servo. I'm going to have to send it to Robotis for service :-(

    Luckily, I have four more in the garage, mounted to the wheels of the Money Pit rover. (I may have posted pictures before -- six wheels, individual steering and suspension on each arm.)

    Anyway, I took off those servos, and attached one to Dynamixel Wizard to configure it. Wizard asked me to update the firmware. I said OK, and the servo never came back. Doesn't respond to firmware update, doesn't repond to scan on any of the common baud rates.
    Given that the rover had crashed and burned, I thought maybe this servo was the cause (I never did diagnose that,) and tried with the next one. Same thing there -- offer to update firmware, brick the servo. I spot a trend!
    I canceled the recommended update, and saw that a bunch of the parameter RAM values were kind-of weird, but I only changed the ones I needed to set up for Malum, and then left the rest alone, so at least I had a working spare now.

    What do I do with the bricked MX-64 servos? Send them back for RMA, too? Is this a known problem?

    My gun agitator/magazine still has some clogging problems. I was looking for design rules online, and ended up in reasonably modern mechanical engineering research papers, and .... this is not a solved problem! "Add vibration" or "shoot it with an airgun to unclog it" seem to be the accepted solutions in industry.

    The more I investigate this, the more I think that my initial simple design with a single hole, and a wiper that rotated BBs right around that hole, was actually one of the better ways of getting a bunch of BBs to line up in single file in a tube ...
    This all took too long, so I STILL

  10. #40

    Re: Malum IK

    Hi @jwatte,

    Wonder if it maybe was a protocol2 version of firmware?

    Have you tried talking to it using the R+ Manager?

    Or maybe try the Dynamixel Manager 2 beta?
    Although I think this one mainly only supports U2D2 or USB2Dynamixel...

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