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Thread: Numa V2 - Quad Mech

  1. #31
    Join Date
    Sep 2008
    Toronto, Ontario
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    Re: Numa V2 - Quad Mech

    Looking good Gertlex!

    Can't wait to see some more video.

  2. #32
    Join Date
    Jun 2011
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    Re: Numa V2 - Quad Mech

    looks at calendar

    So, in the last ten months, I've been very slowly progressing... Hasn't helped that (1) I'm always busy with work and (2) work is very similar, cognitively to the stuff I am doing on a mech. My next milestone is to design and make new legs. (After that I can do full robot testing/debugging/take-over-the-world!) The first step of that has been determining leg geometry, and creating tools to tell me if that geometry is better/worse, and whether it self-interferes.

    (I've managed to forget a lot of the leg terminology... tibia, femur, coax, shoulder, elbow, pan... I may be miss-using terms below)

    Numa V1 vs Numa V2; To get new numbers to plug into analysis, I needed new models. A profile of the AX12 servos is easy to work with in Solidworks sketch mode, so I did that; screenshots below. More compact leg design is my goal. I'll likely remove the 4th servo, too, eventually.
    Click image for larger version. 

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    Numa V1 vs Numa V2; I've got jupyter notebooks that reuse the same python3 code the robot uses for IK, but pipes that workflow into a visualization approach shown below. The leg shown is moving through a gait cycle where it spends part of the time on the ground and part of the time in the air.

    I've got the body closer to the ground now (but also, Numa V2 is also a double-decker chassis currently; maybe I'll move the pan servos to the bottom level though...). The below are likely confusing as they show additional lines that represent edges I'm concerned may intersect (namely, the servo bodies)... But now that I'm reviewing all this I'm slightly facepalming, as I can of course just replace the 4th servo with a long curved or open tibia, and could have skipped most of this intersection work.

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    Name:  Numa2LegPoses.png
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    Numa V1 vs Numa V2: I wanted to be able to view the nominal torque at different points in the leg's movement. Torque is arbitrary units here, and arbitrary numbers, even, as I'm just using approximate weight values for leg segments. Along the way I did better prove to myself that the weight that matters is the weight of the body, and not the weight of the legs, though! Numa V2 below here has higher torque due to the foot contact point currently being further from the shoulder joint.
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    Name:  Numa2Torques.png
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    I'm of course reinventing a lot, and not doing purely the essentials, but it's all worth it (except the sad part where this leaves my C/C++ skills to atrophy, probably). In particular, some skills-y takeaways from the past many months are (1) better code that's easier to test and answer questions with; (2) appreciation for what tf does for ROS; (3) using jupyter notebooks more, and better understanding how to fit them into my software development workflows.

    Next I should explore what removing that 4th servo *really* does for me (and I expect it to make plenty of sense to do so, of course).
    Last edited by Gertlex; 09-09-2018 at 10:06 PM.

  3. #33
    Join Date
    Feb 2012
    Tucson, Arizona
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    Re: Numa V2 - Quad Mech


    Myself and all the guys in Tucson are looking forward to the next V2 step in the Numa Mechwarfare line. It will be great to have a 2 time winning veteran back in the mix. If there is anything we can do to help, let us know.

    The bbs go in here
    Click image for larger version. 

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    Last edited by giantflaw; 09-12-2018 at 01:09 PM.

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