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Thread: MX64 Biped

  1. #1

    MX64 Biped

    I've seen all the amazing things people here are doing. Guess I caught the bug to build something that walks from all these great projects I see.
    I've purchased 8 MX-64T Dynamixels and plan to start here. I'm taking my inspiration from the walker project in the Bioloid build book. My plan is not to buy any ready made brackets, I'd like to CNC my own and do something a little more custom.
    All the brackets will be 6061 to start. I'm using .25 thick stuff for now. With some creative pocketing I can lighten up the brackets pretty well.
    First, I pocket out the center of the brackets and drill for the Dynamixel horn pattern. Then I cut the brackets out of the larger piece by screwing the bracket down to a fixture block I've indicated zero on. The great thing about this fixture block is I can make minor changes to the part even if I remove it. The 8 screw pattern in the center locates the part back on the indicated fixture block should changes need to be made.
    Here's some work so far:
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  2. #2
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    Re: MX64 Biped

    Very nice.

    I can't be sure,but I think that 1/8th might be enough strength for you needs and only half the weight. I don't have a mill any more, so I'm going to have to try cutting and bending my brackets by hand.

    I wish you luck. May I ask what your plans for your as yet unnamed hexapod are?

    Me, I'm mainly into experimentation and art. I build robots for fun with little practical purpose.
    -
    A little learning is a dangerous thing.

  3. #3

    Re: MX64 Biped

    Good thinking on the fixture!

    I've found that 1/8 is plenty thick enough -- 2mm is sufficient. I made some brackets from 3/16 thick 6061 where I milled most of it to 2mm thickness, leaving only a 2 mm edge thicker for the "L-shape" stiffness advantage. And, as you, pocket out the middle to further lighten the part. 3/16 with light surfacing gives me about 4.5mm, which is 2mm for thickness, and 2.5mm edge for wrapping the horn without hitting the case itself.

    Same thing on things that screw into the case: any thicker than 2mm on the front and you'll start seeing the screw heads hit the moving brackets.

    The good news with 1/4 plate is that you can mill the entire thing while keeping a nice 1.5-2mm bottom untouched, and then just flip it over and take off that 2mm and the part pops right down. May want to use minimal tabs to make sure it doesn't come flinging when the last bit is removed...

  4. #4

    Re: MX64 Biped

    The first couple of prototype brackets turned out nice. I still haven't cut the bottom parts yet that will connect the two halves together.
    The pockets are cut down .180 leaving about .070 bottom thickness. The sidewalls are about .050. The whole bracket is light and has a nice sturdy feel to it. I started the second set of angle brackets a little while ago. I have to make 4 total.

    I'm right there with you on the "experimentation and art" of building these things. My bots rarely end up having a real life purpose. lol
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  5. #5

    Re: MX64 Biped

    I should have posted this to begin with. This is what I'm building, only with MX-64 actuators. I'll use a Arbotix-M as well.

    I know dynamixel has a program that allows you to see the numerical position of each AX-12 actuator and record it. Does anyone know of a program like that which will work with MX-64T actuators?
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  6. #6

    Re: MX64 Biped

    Oh, nice, a biped walker!

    I know that Dynamixel Wizard works fine with the MX-64 in addition to the AX-12. I don't know if the other tools from RoboPlus will work the same; I'd expect them to but haven't tried it.

    I just built the "read the pose when the button is pressed and store in a file" tool myself (on Linux.) It was a nice distraction :-) Not very hard, either -- the Dynamixels and the serial bus are pretty nice to work with! (Except once in a while they will miss a command and need a re-try.)

  7. #7
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    Re: MX64 Biped

    Quote Originally Posted by Machine27 View Post
    ... I'll use a Arbotix-M as well. ... Does anyone know of a program like that which will work with MX-64T actuators?
    You can use pypose, it is the default firmware loaded on the Arbotix.

  8. #8

    Re: MX64 Biped

    Pypose...
    I'll give it a try. Thanks very much.
    I'm running the foot pads as I type this. Should have a picture of the finished pad tomorrow. The second set of angle brackets turned out nice!

  9. #9
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    Re: MX64 Biped

    Ah, the Gerwalk. Sadly the series they got the name from was before my time. For a biped, it is surprisingly easy to make walk without falling, but turning requires skid-steer so its performance varies with the ground surface. With 8 servos, I was kind of expecting two servos for the ankle, one servo for knee, and one servo for hip pitch. It is a bit more difficult than the Gerwalk to make climb up stairs because the width between the feet changes as weight shifts, but a little bit easier to make walk since the weight shifting is performed at the ankle instead of the 'head'.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  10. #10

    Re: MX64 Biped

    I saw a biped on Youtube that Zenta made. It has two servos on the foot and two on each side of the hip. One servo on the knee for a total of 10 or 11 I think. Mine may progress to that eventually. Gotta buy more MX-64s for that upgrade. I believe that setup would turn easier vs the skid steer.

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