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Re: [SeattleRobotics] Re: Beyond tripods...

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  • Peter Balch
    Dan ... I was calling it sprawled because it has a 90deg bend at the coxa/femur joint. The femur/tibia joint stays pretty straight when the foot is down so
    Message 1 of 192 , Jun 1, 2009
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      Dan

      > We certainly have differing perspectives. It seems to
      > me BD is a "sprawled" posture to exactly the same
      > extent that the 2 humans in the Beta costume version
      > that BD was based upon are sprawled posture.
      >
      > Just because you bend your legs doesn't mean you've shifted from upright
      > to sprawled.

      I was calling it sprawled because it has a 90deg bend at the coxa/femur
      joint. The femur/tibia joint stays pretty straight when the foot is down so
      it's equivalent to the leg of a "standard quadruped robot" except that it's
      H-plan rather than X-plan. That's totally unlike the "robot" shown in the
      Beta costume version.

      Aha, I think I may see why we have such differt perspectives.

      I'm referring, of course, to last year's model (the latest, I think) as
      shown in the 17 Mar 2008 video
      http://www.youtube.com/watch?v=W1czBcnX1Ww

      The older model from a year before _was_ like the Beta costume version, see
      the 20 Apr 2007 video
      http://www.youtube.com/watch?v=qEbxhy9qa8M

      The old model certainly had a "mammalian" stance. I agree with all of your
      arguments about Old Big Dog. But for New Big Dog, the designers have decided
      that an H-plan "lizard" stance is superior.

      Peter
    • dan michaels
      ... It s difficult to say how the horse and mule would walk differently, just by looking at those pictures. But they do seem to have the same set of bones and
      Message 192 of 192 , Jun 5, 2009
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        --- In SeattleRobotics@yahoogroups.com, "Randy M. Dumse" <rmd@...> wrote:
        >
        > dan michaels said: Friday, June 05, 2009 3:38 PM
        > > Did you get the message about how they all have an "extra"
        > > short bone and joint right up at the torso, just like Big
        > > Dog. one end is pelvis, other end is clavicle. These joints
        > > aren't so obvious, since they're kind of hidden on the body,
        >
        > Yes, I saw that, but the question is do donkeys and mules have
        > the same additional bones (yes), and how are they oriented
        > differentyl between them. The front end of a mule is much more
        > vertical, with legs more straiht down from chest, while the
        > horse legs are set back further allowing more muscling infront
        > of the legs. Or at least that is as it appears to me.
        >


        It's difficult to say how the horse and mule would walk differently, just by looking at those pictures. But they do seem to have the same set of bones and joints. For that matter, so do dogs and cats, and also Big Dog, except that the leg proportions are a little different in dogs and cats, and Big Dog is missing "feet" (except in some pictures where it appears to be wearing human style shoes).

        >
        http://upload.wikimedia.org/wikipedia/commons/4/46/\
        Penn_state_old_coaly_work_mule_skeleton.jpg
        >


        Birds are especially funny-looking, because they seem to have their rear legs on backwards, but it's just an illusion. They have the usual "knee" way up near the body under the feathers, and a very elongated foot, so the ankle comes across as a backward pointing knee, on first glance. Each leg adapted during evolution for slightly different use.


        >
        > Said another way, the horses rib cage appears further forward,
        > so has a larger chest, and ends more forward, less toward the
        > hips.
        >
        > Yes, those extra bones are almost hidden under flesh, and they
        > are difficult to perceive as "leg" unless you really pay
        > attention to the musculature around them when they are in
        > extended or odd positions. At least while still with their skins
        > on.
        >
        > Randy
        >
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