Subject:
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Re: Almost 300! And another Mindstorms Challenge! And more!
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 22 Jul 2006 11:30:06 GMT
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Original-From:
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steve <sjbaker1@airmail.netANTISPAM>
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Viewed:
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3577 times
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bobcrean wrote:
> I read the entire thread, and the rules and ask the question: Why must it
> ROLL at all? If friction is the name of the game, and if the wheels (tires)
> are the parts that have the "stickiest" qualities, then why not maximize the
> surface area of those. To do that, you lay them on there side and inch the
> robot along, barely lifting half of them alternatively, inching them
> forward.
So you have (in essence) a walking robot - but you wouldn't want to
halve your traction by having only half of your feet on the ground at
any one time - you'd want to have a robot with LOTS of feet and pick
up just some tiny fraction of them at any one time. Something with a
hundred little feet which only lifted one of them at a time would have
almost twice as much surface on the ground as a biped.
However, surface area on the ground isn't everything. The pressure
exerted onto the ground matters too. With more area but the same weight
of robot, you have less pressure at each point. Whether this is a
terrible thing or not depends on the nature of the surfaces in contact.
For some surfaces, it's almost irrelevent what the surface area is - the
amount of friction depends only on the weight of the object and the
coefficient of friction. For other surfaces, both the weight and the
surface area matter. That's one of the things that makes this tricky.
> In this arrangement, "speed" becomes irrelevant, in that you are not relying
> on the torqe of the motors to do anything but lift the "pads", scooch them
> forward and put them down and drag them backwards.
That's not true. There are two parts to walking - one is the trivial
act of lifting an unloaded foot and moving it forwards - but the power
is required in pushing down on that foot such that it propels the body
of the creature forwards.
So - no - you are completely incorrect. The torque of the motors still
matters a lot.
> Wouldn't this approach "walk away" with the prize vs. any rolling robot
> using the same wheels?
Not necessarily.
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