Page 3 of 4 FirstFirst 1234 LastLast
Results 21 to 30 of 35

Thread: RX-28 Darwin OP Based Mech: Tychus

  1. #21
    Join Date
    Sep 2010
    Posts
    206
    Images
    16
    Rep Power
    39

    Re: RX-28 Darwin OP Based Mech: Tychus

    No, as my limitation currently isn't max torque, but the heat dissapation of the motors. The mx has a similar thermal model, but I think the pid would allow more efficient use.

    Also, darwin useS mx28 and do not appear to have this issue, although I have never played with one.

  2. #22
    Join Date
    Sep 2010
    Location
    ಠ_ಠ
    Posts
    2,297
    Images
    27
    Rep Power
    278

    Re: RX-28 Darwin OP Based Mech: Tychus

    The theatre students have yet to complain about any thermal overload issues in the DARwIn-OP (they have abused it so. It face planted enough times to knock the clear plastic of the forehead into the skull), and I cannot remember any occurrences of overload when it has been in the lab. It is built from the first batch of MX-28, with all of them still labeled 'RX-28M'. The lower voltage limit of the MX-28 might also have an influence on the likelihood of thermal shutdown, as well as any potentially upgraded parts like an on-board voltage regulator or H-Bridge. Talking out of my bum a bit, given that I have not taken apart any of the MX-28 and there are no RX-28 in the lab for me to make an internal comparison of the two models.
    I have maybe two real complaints about the DARwIn-OP, first is the small battery compartment (3S 1000mAh lasts maybe 20 minutes if you are really lucky) and the second is the power input board. That little board has a standard barrel plug connector, a Deans connector, and the power switch in very close proximity, which makes replacing the quickly discharged batteries without bumping the power switch a bit difficult if you do not have small and nimble fingers. Also, the barrel plug has only one detente level making it disconnect when there is much movement. When testing it very much without the battery, it is best to use/make a barrel plug to deans adapter.
    Last edited by tician; 11-02-2011 at 04:33 PM.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh
    more bleh

  3. #23
    Join Date
    Feb 2010
    Location
    Northern, VA (Fredericksburg)
    Posts
    104
    Images
    10
    Rep Power
    33

    Re: RX-28 Darwin OP Based Mech: Tychus

    @Cire - thanks for the info; I am hoping the MX-28's will work out for me. It seems like a good time to get them as they should be fairly good with the realitivly recent release date.

    @Tician - Thank you as well! You seem to have a bit more exposure to the MX-28's release and Darwin OP. Do you think that the DarwinOP is designed fairly well from the hips down? I don't care much about the chest and arms as I won't be using them if I do Mech warfare.

    Cheers,
    Scott

  4. #24
    Join Date
    Sep 2010
    Location
    ಠ_ಠ
    Posts
    2,297
    Images
    27
    Rep Power
    278

    Re: RX-28 Darwin OP Based Mech: Tychus

    Not sure how I forgot to give props to cire for making yet another very impressive bot so very quickly. I am one of those nutjobs who thinks a lot of mechanical and electrical devices designed for a variety of useful purposes can be far more innately beautiful than most things created solely as 'art', and immortal is pretty high up on the list (kind of like an axial piston pump or an old mechanical clockwork or a Tesla coil or many, many, many others, something about watching it move is just a bit mesmerizing).

    Careening off topic:
    The servos in the DARwIn-OP are basically in the same layout (joint positions and orientations) as the Type-A Premium Humanoid with additional pan and tilt servos for the head. The big difference is in the proportions and materials of the servos and frames; all frames are aluminum sheet (1.5~2.0mm of 5052) and all of the MX-28 have fully metal gearsets. This combination means there is none of that weak knee business I have seen in the Type-A and Comprehensive Humanoids where the entire leg kind of bends or flexes even when the servo is staying put. Having seen aluminum frames in action, if I were given the choice I would always use aluminum over plastic. It's a lot stronger/more resilient, a lot stiffer, self tapping, doesn't melt or weld itself together with Loctite, relatively inexpensive in sheet form, and pretty easy to make into frames with fairly simple tools. Combine that improved positional accuracy with the IK engine of the 'walking' motion module in the open source framework and you get really nice motion (except at metal transitions sticking up several mm above grade as the foot kept catching and tripping it. I'm not sure I have the programming prowess to ever code any compensation/reaction system, although I'm know plenty of others do).
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh
    more bleh

  5. #25
    Join Date
    Sep 2010
    Posts
    206
    Images
    16
    Rep Power
    39

    Re: RX-28 Darwin OP Based Mech: Tychus

    tician, I am the same way you are about electro mechanical devices (or purely mechanical), so thanks for the compliment . I am planning on redesigning the mechanical aspect of this robot in the near future to give it a more interesting look. I also hope to make the movements fluid like a living organism, drawing from work done by Zenta, or Crabfu - they both seem to manage fluid moving robots.

    For the update:

    I replaced a bracket that was a slightly different length, and adjusted the standing position in an attempt to balance out the force between the 2 legs. This appears to have fixed the overheating in the right knee, they both hover within 2-3C of each other which I think is pretty good. I also have been unsuccessful at overheating the motors, topping out at around 72C while walking arround. I am pretty happy with that for now!

  6. #26
    Join Date
    Jan 2008
    Location
    Norway, Stavanger
    Posts
    790
    Images
    276
    Rep Power
    80

    Re: RX-28 Darwin OP Based Mech: Tychus

    Hi,

    I'm very impressed by your fast progress on the walking part! Looking very good. Do you use full 6 DOF IK or a combination of some FK and IK? Your youtube channel was worth subscribing.
    Kåre Halvorsen aka Zenta
    ---------------------------------
    Zenta's YouTube channel
    Zenta's Blog
    Zenta's Instagram

  7. #27
    Join Date
    Sep 2010
    Posts
    206
    Images
    16
    Rep Power
    39

    Re: RX-28 Darwin OP Based Mech: Tychus

    Hi zenta,

    The ik engine only has 4 inputs x,y,z, yaw. it solves assuming foot is parallel to the ground. this simplification helps allow me to update positions at 20 hz, although I may add body tilt and roll in the future to see what kind of benefits i can get.

    of course more inputs means more stuff to edit when tuning. My goal is to have a minimal amount of adjustable parameters that allow quick tuning of a robot.

  8. #28
    Join Date
    Sep 2010
    Posts
    206
    Images
    16
    Rep Power
    39

    Re: RX-28 Darwin OP Based Mech: Tychus

    I owe an update on here... Not that I've made a lot of changes since my last update...



  9. #29
    Join Date
    Sep 2009
    Location
    Baumholder, GE
    Posts
    284
    Images
    51
    Rep Power
    40

    Re: RX-28 Darwin OP Based Mech: Tychus

    Looks like it is coming along very nicely

  10. #30
    Join Date
    Sep 2010
    Posts
    206
    Images
    16
    Rep Power
    39

    Re: RX-28 Darwin OP Based Mech: Tychus

    Added a video from Robogames:


Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. For Sale: Kondo KHR-3HV Based Mech (heavily modified)
    By DresnerRobotics in forum Garage Sale
    Replies: 11
    Last Post: 11-10-2011, 01:56 PM
  2. Project Upgrayd's AX-12 Darwin
    By Upgrayd in forum Project Showcase
    Replies: 35
    Last Post: 09-12-2011, 08:09 PM
  3. Question(s) What do you want to know about DARwin-OP?
    By Xevel in forum Robotics General Discussion
    Replies: 3
    Last Post: 03-27-2011, 04:45 PM
  4. A BRAT based Mech, "Miss Alignment"
    By darrellt in forum Mech Warfare
    Replies: 33
    Last Post: 04-28-2010, 05:39 PM
  5. BRAT Based Mech?
    By Roboman in forum Mech Warfare
    Replies: 102
    Last Post: 09-18-2009, 06:23 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •