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Thread: RX-28 Darwin OP Based Mech: Tychus

  1. #11
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    Re: RX-28 Darwin OP Based Mech: Tychus

    Update:

    Video of some progress with actually walking:



    Right now it doesn't have the fit-pc on it, just a cm-700. I wrote an excell program that allows me to tune body shifting, step length, offsets in servos, and walk speed. It then generates a series of poses that i copy into roboplus motion. This will help me learn how to make it walk successfully and create my gait before i write the actual program.

    Next to do is to add the arms, and then retune the walking including arm swing, which i believe will be beneficial.

  2. #12
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    Re: RX-28 Darwin OP Based Mech: Tychus

    I modified the walking gait a bit by shifting the body earlier, and added rubber pads to the bottoms of the feet. The feet previously were sliding a lot, which messed up the body shifting.



  3. #13
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    Re: RX-28 Darwin OP Based Mech: Tychus

    Cire...I'm really impressed. This is great progress, and so quickly too! Amazing.

    DB

  4. #14
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    Re: RX-28 Darwin OP Based Mech: Tychus

    Thanks DB, I have some more progress from this weekend as well:


    I decided to move on from the CM-700 and start using the Arbotix 2. I felt that I understand how to generate a gait well enough with the spreadsheet I had created previously to write something that generates it on the bot itself. I used Immortal's code structure (a NUKE export originally) and rewrote the Inverse kinematics and gait generator for my biped, as well as added some tuning variables. I probably spent as much time tuning the robot as I did writing the actual code, as i was plagued by a few issues in the legs not being exactly the same and a previous shortcut I had taken on my spreadsheet generator to compensate for the differences in the legs. I still plan on adding some more features to the gait generation as it doesn't walk as reliably as I want it to yet. Here is a video of the progress so far:




    I still have a few issues to work out - right now the knees overheat after it stands/walks for too long. one of them also tends to run a few degrees above the other one, which I think may be due to a slight difference in the legs or the servo's themselves again. Also the surfaces and directions it can walk are fairly dependant on how the robot is tuned - one set of tuning allows me to walk on carpet, while another allows me to walk backwards on tile floor, but not both at the same time. I also need to get the rest of the payload on the robot before i spend too much time tuning it. I think more mass will make it easier to tune, but hurt my overheating issue with the knee servo.

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    Re: RX-28 Darwin OP Based Mech: Tychus

    That is really amazing work. Really it makes the argument for IK more than clear. I'm especially impressed with how Tychus is walking on carpet and can walk in curves like that with such small feet!

    I can't wait to share this video with my students.

    DB

  6. #16
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    Re: RX-28 Darwin OP Based Mech: Tychus

    Yea, allot cleaner than my pose method with dynamic turning. I need to dust Odin off and work on him again.. But, other stuff taking my time these days. Nice work Cire! Also, no fair using my Minigun look on Tychus.

  7. #17
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    Re: RX-28 Darwin OP Based Mech: Tychus

    @connor, my gun probably wont look anything like that, but i think i did subconsciously stole that from your mech

  8. #18
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    Re: RX-28 Darwin OP Based Mech: Tychus

    @Cire - What are your thoughts/feelings on the RX-28's now that you have had a chance to use them? I assume they are the being used in the legs exclusively, but can you confirm that?

    Thank you for showing us what they are capable of!

    Cheers,
    Scott

  9. #19
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    Re: RX-28 Darwin OP Based Mech: Tychus

    Quote Originally Posted by sarendt View Post
    @Cire - What are your thoughts/feelings on the RX-28's now that you have had a chance to use them? I assume they are the being used in the legs exclusively, but can you confirm that?

    Thank you for showing us what they are capable of!

    Cheers,
    Scott
    I haven't completely decided yet how i feel about them. I say this because I haven't figured out why the right knee heats up a lot more then the left knee yet. I actually replaced the left knee early on because the servo i was using had a huge amount of backlash (relative to the other rx-28) for some reason. Both knees originally were older servo's i think, which may have been the source of all the issues. I think I am going to swap out the right knee and see how it affects the heat buildup. According to the load reading, it sees about 16% of max load (although i heard the load readings are pretty much useless) and it heats up continuously to thermal shutdown (80C). I'm not too impressed with the efficiency/heat dissipation of it from that aspect, although that appears to be out of the norm for the knee.

    Torque wise - They have more then enough torque available to them - I haven't had many issues doing the walking motions (although i did have to play with compliance's a bit).
    Response wise - They are really fast, i send 20 position commands a second and they follow just like they are supposed to... Depending on how i tune the robot they are either really smooth or a little jerky.


    Overall, I wish I had MX-28's to utilize all the nice features (PID, 4096 res, 360 degree rotation, 3mbps bus, 12v rather then 16v), as well as the fact that RX-28's will be phased out for the mx-28 soonish I believe. Which means I will be stuck when it comes to finding replacements in the future (i have 4 spares if i pull them out of the arms, so i am not too worried about that).

  10. #20
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    Re: RX-28 Darwin OP Based Mech: Tychus

    Would you be conserned with the lower torque on the MX-28's? Looks like 24 Kg/cm vs. 37 with the RX-28's.

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