Alt-BEAM Archive
Message #08356
To: beam@sgiblab.sgi.com
From: Senior kyled@cruzers.com
Date: Fri, 17 Dec 1999 23:27:01 -0700
Subject: [alt-beam] Re: Bi ped
Eh hahah yeah, I kinda get stuck :)
Hmm, when I thought it up it worked in my head! :)
Kyle
Ian wrote:
>
> Hi
>
> > An idea I had a ways back for a four-legged walker's feet:
> > Gvie the feet/ankle one degree of freedon, paralell with the direction
> > of walking. Let them swivel freely or give them a bit of resistance with
> > springs. Use a solenoid, a brake, or something of that sort so that all
> > we have to do is put the foot down, and it will automatically match the
> > angle of the surface, and then lock it in that position before any
> > weight is put on it.
>
> Yes I had that idea (don't know why it left my mind). It would seem like it
> would be the best but after looking at the walking video @:
>
> http://www.inrialpes.fr/bip/
>
> It seems that the ankle idea in an email I just sent would give the same
> motion. Do you think so?
>
> I just had a thought.... Your saying that as soon as the foot touched down
> it would lock in place right? Then say, take a step forward and lock your
> ankle. Your kind of stuck right?
>
> Laterz
>
> --------
> O o
> _\_ o There is only one true "SyNeT"
> \\/ o\ .
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8357 Fri, 17 Dec 1999 23:34:25 -0800 (PST) [alt-beam] Re: Bi ped beam@sgiblab.sgi.com Darrell Johnson here's an interesting link:
http://www.msc.cornell.edu/~ruinalab/pdw.html
it's a strictly mechanical approach that will let the
device walk bipedaly down gentle slopes without any
power source or controls.
> Ian wrote:
> >
> > Hey, I was just browsing some web sites related to
> biped walkers and it
> > seems most are 10 motors designs ...
>
>
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8358 Fri, 17 Dec 1999 23:54:33 -0800 [alt-beam] Re: Bi ped beam@sgiblab.sgi.com Bruce Robinson Ian wrote:
>
>> IMHO, you'd be better off spending your energy
>> elsewhere..
That's more or less what a university professor told his student, Fred
Smith. Fred ignored the advice, and started the business he was
proposing. Successful? I dunno. Ever hear of and outfit called FedEx :)
> Your probably right but I'd like to at least give it a try. If I can at
> least get it to stand up and balance I'll be happy.
Go for it. You might want to use the static balance approach to start.
That'll teach you a lot about leg and balance control systems. And it's
a heck of a lot easier to tell what's going wrong when it falls over.
Bruce
8359 Fri, 17 Dec 1999 23:58:12 -0800 (PST) [alt-beam] Re: Bi ped beam@sgiblab.sgi.com Darrell Johnson
--- Ian wrote:
> Hi
>
> > yeah, you are going to need *at least* 10 motors
> to
> > make a biped walker that can actually walk.
> I'm watching a movie of a 4 motor biped walker
> walking fine right now so it
> isn't "required" but if you want more
> maneuverability to turn and stuff your
> going to need more.
That's what I thought you were trying to do.. a 3D
walker.. of course less motors will work for a 2D
walker.
>
> > Say you want the bot to lift one leg while
> standing.
> > You are going to have to shift the center of
> gravity
> > 'COG' over the foot that is still planted on the
> > ground. This is where your original pic that you
> > posted fails. you have no DOF to accomplish this
> > shift.
> Um, no. Not from what I see. I have a side-to-side
> motor in each ankle. Just
> turn that and raise the opposite leg and it will
> rest one leg. Then you are
> able to lift the leg and move it around. Keeping the
> balance using the ankle
> motor and hip motors of course.
>
Um, yes.. I'd like to see you lift one of your feet
off the ground by flexing the opposite ankle.. ain't
gonna happen.
You have two feet planted squarely on the ground. the
COG is directly between the feet. Rotating that one
ankle motor isn't goinng to lift all that weight of
the other leg off the ground without tipping over..
Don't believe me? Go ahead and do it your way. When it
doesn't work, I *will* say "I told you so, Ian" and
then sit here and laugh. ;)
-darrell
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8360 Sat, 18 Dec 1999 01:29:41 -0700 [alt-beam] Re: Bi ped Ian Hi
> Um, yes.. I'd like to see you lift one of your feet
> off the ground by flexing the opposite ankle.. ain't
> gonna happen.
> You have two feet planted squarely on the ground. the
> COG is directly between the feet. Rotating that one
> ankle motor isn't goinng to lift all that weight of
> the other leg off the ground without tipping over..
Well ya. If you just stand there and lift one leg your going to fall over.
You need to first get the COG over one of the feet by lowering just the leg
your going to balance on and rotate at the ankle at the same time. You are
now standing at a slight angle with the COG over the foot with the lowered
leg. I'm I missing something here?
Laterz
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