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[SeattleRobotics] Re: Legs not wheels

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  • Rich Chandler
    ... No, that s not quite what I m talking about. Although I suppose in a way, it s related. Way too many folks design the legs so that the entire torque of
    Message 1 of 533 , Sep 1, 2007
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      At 3:34 PM +0000 8/31/07, dan michaels wrote:
      >--- In SeattleRobotics@yahoogroups.com, Rich Chandler <rchandler@...>
      >> Actually, One thing I'm interested in is an improved mechanical
      >> design that avoids supporting the weight of the robot via the force of the
      >> servos. And from there, I'm interested in programming the motion so that
      >> there isn't any sideways force on the feet as it walks or turns. Those
      >> things interest me.
      >The easiest way to do the former is use "upright" or rotated-under-
      >the-body leg design, rather than sprawled leg design.

      No, that's not quite what I'm talking about. Although I suppose in a way,
      it's related. Way too many folks design the legs so that the entire torque
      of the horizontal "Thigh" is directed through the servo, with the servo as
      the pivot point. My idea is to design the leg so that the thigh is lifted
      and lowered by the servo, but a) the pivot point is not the servo and b)
      that when the leg is supporting weight, there's no torque on the servo. So
      like the leg you're talking about, the force against the servo is radial to
      the axis of the servo, like a locked knee. (Alternatively, I was thinking
      a spiral cam for raising and lowering the leg, which would never torque the
      servo in any position).

      >Regards the later comment, you will observe that a certain amount of
      >sideways force on the feet is necessary in order for the frame to
      >have stability. Rbt Full calls this "lateral self-stabilization", and
      >it's a MAJOR factor in reducing the amount of processing power [ie,
      >brain power in animals] required to produce stable locomotion.

      On this point I'm talking about the kinematics of the foot end of the leg,
      because so many designs (other than that cool five-legged robot we've seen
      at various meetings) don't pay enough attention to the tracking of the foot
      on the ground, and tend to slide or drag their feet while turning. For
      that I'm looking at the lower leg (shin?) being able to track in and out.
      And again, I don't plan to support the weight through the servo, which
      should significantly reduce power consumption.
    • Robert F. Scheer
      ... Good reading! Thanks. I m glad I abandoned earlier thoughts of writing about the post-biological future. He s 20 years ahead of me and so much better a
      Message 533 of 533 , Oct 16, 2007
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        dan michaels wrote:
        > --- In SeattleRobotics@yahoogroups.com, "Robert F. Scheer"
        > <rfscheer@...> wrote:
        >> What are some of the desired outcomes in robotics?
        > For my part, I had always liked some of Hans Moravec's ideas for
        > future robots, eg, as expressed in some of the books/papers lower-
        > right on this page ...
        > http://www.frc.ri.cmu.edu/~hpm/
        > http://www.frc.ri.cmu.edu/~hpm/project.archive/robot.papers/2000/puddl
        > e.html
        > http://www.frc.ri.cmu.edu/~hpm/project.archive/general.articles/1993/R
        > obot93.html
        Good reading! Thanks. I'm glad I abandoned earlier thoughts of writing
        about the post-biological future. He's 20 years ahead of me and so much
        better a thinker. The only complaints I see in Moravec's vision are:
        1. it isn't integrated into a viable energy supply vision; robots must
        either result in less net energy used or more energy "produced" such as
        by solar collection;
        2. it doesn't manage the growth of human population on earth and in
        fact could produce unprecedented compounding; I have no answer to this;
        3. the impact of vastly greater numbers of people and robots with
        vastly greater economies on the natural ecology is almost certainly
        totally destructive or transformational in the extreme; will Greenpeace
        be content with a virtual version of the natural history of Earth and
        does it matter?

        So, we should be actively working to make Moravec's First-Generation
        Universal Robots a reality. We only have 3 more years to go.

        This should be a good discussion.

        - Robert
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