Alt-BEAM Archive
Message #08869
To: beam@sgiblab.sgi.com
From: Senior kyled@cruzers.com
Date: Thu, 06 Jan 2000 18:02:30 -0700
Subject: [alt-beam] Re: Biped Beam Bots
Sounds cool. But how does it shift wait onto one leg so it can move the
other one?
-Kyle
Evan Dudzik wrote:
>
> well, i have a 5-motored 2 legged bot, in which one
> motor would be like a knee, only facing backwards, and
> the other would be a hip... like those big two legged
> walker things in star wars (remember the ones that
> hunted them in the woods???)... thats only four motors
> (servos)... the fifth??? it goes at the top, and faces
> straight up. affixed to the horn is one of those 4X
> AA battery holders, in which two rows of 2 AA's are
> side by side, so it is long... this way, no weight is
> added to shift the center of gravity left and right
> save that of the servo... no extra weight to lug
> around...and the battery pack could be shifted closer
> to being centered over the servo... if centered, when
> rotated, it wouldnt shift the center of gravity left
> or right... but if all the way out as you could put
> it, it would practically tip the bot over. This would
> make it easy to fine-tune the shifting of weight. the
> feet would be little tripods of coathanger wire, with
> rubber nubs on the end of each foot. The feet would
> be wide enough so that they ALMOST touch in the middle
> of the bot, so as to make as little weight as possible
> necessary to shift... I might do that LATER when i
> actually HAVE 5 servos...
>
> --- Dane Gardner wrote:
> > > 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
> >
> >
> >
>
> =====
> +------------------------+
> |http://surf.to/photovore|
> |Photovores online! |
> |Evandude Dudzik |
> +------------------------+
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8870 Thu, 06 Jan 2000 21:14:28 -0500 [alt-beam] Re: Pressure Sensors George Rix > Hi, I was just looking around for pressure sensors to use on my biped
> walker. The first place I looked was Jameco and I found one that looked
> good. I thought to myself "I'll get on the net and order 8 of them". That's
> when I looked at the price and noticed that they were $10 each. No way I
> could spend that much money. I then checked DigiKey. Prices there range from
> $13 to $150. Ouch! I then checked that web site that Evaristo posted but I
> couldn't find any prices on their site. Anyone know of a cheap source for
> pressure sensors? Thanks
Well, if you didn't mind some extra effort, you could attach a small gear to
the end of a pot, and then use a rack (like in rack and pinion steering) to
change the resistance. Just give it a spring to go back to normal, and
voila! A pressure sensor (I hope).
Peace out!
Rob Rix
P.S. Was that clear? If not, I'll try better next time...
God knew what he was doing when he deprived man of wings.
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