Alt-BEAM Archive
Message #08856
To: beam@sgiblab.sgi.com
From: David Stafford write2dave@yahoo.com
Date: Thu, 6 Jan 2000 06:31:27 -0800 (PST)
Subject: [alt-beam] Re: Biped Beam Bots
When I was in Engineering Collage at U of Houston 8 years
ago, Someone had a class project to balance a stick on end.
They connected the stick to a printer head. They
controlled the position of the printer head with a pot
attached at the base of the stick. So if the stick leaned
to the left the head would rush to the left to overcome the
off centered ballance. There were extra tricks added of
over travel (cause if you just made it verticle, it would
still need to stop the left moving mometum) It only moved
left and right, the stick could only fall left or right
because of the way it was hinged. All of the circuitry was
opamps and resistors and caps ie there was no PIC. Sorry,
I don't know any more about the project.
You did get me thinking last night about 2 leggers. I
remember I saw a street performer climb a 8 foor ladder
(that was not leaning against anything) and made the ladder
walk around (on 2 legs). I think this 'balancing' trick of
teatering from side to side making little steps back and
forth just to stand still would be a start (a huge start).
Like Mark Tilden said 'walking is meerly controlled
falling'(most likely i am miss quoting him). The next step
would be to lean the bot forward to make it walk.
I think the next step would be to have it be able to stand
up after it falls (or gets tripped) so it could survive in
a RJP. Then of course Kicking other critters would follow
:)
My $.02
Dave Stafford
--- Evaristo Westplate wrote:
> Hi,
>
> >As far as I've seen...MIT's "tail" comes in contact with
> the ground from
> >time to time, though. This tail would probably do
> better between the legs
> >than up in the air.
>
> When you place the tail between the legs then it will be
> impossible to let
> the walker stand on one leg because the center of gravity
> will remain
> between the legs. Suppose the tail is behind the legs so
> it can swing
> freely to the left or right. No then the whole center of
> gravity would be
> so low that it will take a lot of efforts to get the
> robot stand on one
> leg. The whole issue is center of gravity. The higher it
> is the easier it
> is to shift it. Besides isn't a tail designed to prevent
> an animal/robot
> from falling when the body bends forward towards the
> ground? A can remember
> a walker which had a rod mounted on the waist. The rod
> pointed upwards and
> at the end of it there was a weight attached. By moving
> the rod the robot
> could control the center of gravity. I have seen a video
> of this robot
> walking and you could see very clearly how the rod
> controlled the balance.
>
> I have a presentation about the walker which I build but
> it was made on an
> amiga computer. It explained the whole concept (it was my
> school project on
> which I graduated).
>
> See'ya
>
>
> Evaristo
>
> Gizmo homepage: http://www.crosswinds.net/~evaristo
> Biped photos :
> http://www.crosswinds.net/~evaristo/biped.html
>
>
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8857 Wed, 5 Jan 2000 21:14:47 -0800 [alt-beam] Re: Biped Beam Bots "Dane Gardner" > When you place the tail between the legs then it will be impossible to let
> the walker stand on one leg because the center of gravity will remain
> between the legs.
I didn't mean to leave it there. I meant for it to be able to swing outward
(either forward or behind) from in between the legs. If you leave enough
room...and don't want a head...you could have the tail swing completely
around the center of the body, in a vertical fasion.
> Suppose the tail is behind the legs so it can swing
> freely to the left or right. No then the whole center of gravity would be
> so low that it will take a lot of efforts to get the robot stand on one
> leg. The whole issue is center of gravity. The higher it is the easier it
> is to shift it.
Yes but a top heavy two leged bot would never be able to just sit still. I
would have to be able to move constantly. And unless you build something in
that allows the bot to get up from a fall, you would be condeming the bot to
a lack of sleep.
> Besides isn't a tail designed to prevent an animal/robot
> from falling when the body bends forward towards the ground?
Not only that. It helps it to get up without the help of arms and hands.
> A can remember
> a walker which had a rod mounted on the waist. The rod pointed upwards and
> at the end of it there was a weight attached. By moving the rod the robot
> could control the center of gravity. I have seen a video of this robot
> walking and you could see very clearly how the rod controlled the balance.
I'm just saying that unless you want a HUGE bot with a lot of body mass,
you're going to end up with a really top heavy system.
CYA,
Dane
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