Alt-BEAM Archive
Message #05900
To: beam@sgiblab.sgi.com
From: "Jason -" evenflow88@hotmail.com
Date: Sat, 28 Aug 1999 00:41:11 GMT
Subject: [alt-beam] Re: Walker leg centralizing info
>From: Bruce Robinson
>Reply-To: beam@sgiblab.sgi.com
>To: beam@sgiblab.sgi.com
>Subject: Re: Walker leg centralizing info
>Date: Fri, 27 Aug 1999 12:55:33 -0700
>
>Jason - wrote:
> >
> > Hi all, recently the thing that made me dislike
> > or bored of building bots is the fact that how
> > to centralize a leg in a two motor walker....i
> > heard stuff like mechanical stops and springs
> > and etc. i am all tired of that and it can make
> > the ot reall uncool and messy....
>
>I'm surprised no one jumped on this one. So from me you get a long,
>technical discussion.
>
>The legs on a walker form part of a system. As they oscillate, you want
>them to remain centred about one spot. So the goal of the system is to
>keep moving the legs back toward the centre whenever they move away from
>it. However, you don't want the system to respond TOO quickly, or the
>legs will never move.
>
>What this means in practical terms is this. You need something that will
>measure where the legs are relative to the centre, and exert an
>appropriate force to direct them back to the centre whenever they drift
>away.
>
>Springs do this very nicely when you arrange them proplerly. Electronics
>can do it too, but you need to sense the position of the legs. I devised
>a purely mechanical device that determines when the legs are moving too
>far in one direction, and changes the bias on the microcore to prevent
>it -- but if you though SPRINGS were ugly, you definitely will not like
>this design (and it's very complicated).
>
>The one thing that is very elegant is gravity. If you can arrange the
>geometry of your motors and legs so that they will be centred when the
>body is lowest (relative to the feet), then you may find your legs
>staying centred. If you look carefully at some of Tilden's walkers,
>you'll notice that the motors are often mounted so the shafts are NOT
>perpendicular to the ground. This means that there will always be some
>kind of restoring force caused by gravity.
>
>The bottom line is, whatever method you use, there has to be some kind
>of feedback that tries to restore the legs to centre: springs, gravity,
>electronics. Gotta have something.
>
>Regards,
>Bruce
well...not that i say spring is ugly but it is kinda hard for me to find it
here....and it is quite expensive too..i tried some small springs bbut it
didnt work at all.....so do any of u guys know any electronics that could
solve this problem like the encoder wheel that tilden mentioned.....and
another thing is bruce what do u mean by some of Tilden's walkers,
>you'll notice that the motors are often mounted so the shafts are NOT
>perpendicular to the ground. This means that there will always be some
>kind of restoring force caused by gravity.
thanks a lot
jason
______________________________________________________
5901 Fri, 27 Aug 1999 12:56:45 -0700 [alt-beam] Re: proximity sensors beam@sgiblab.sgi.com Bruce Robinson Ivan patrick Codd wrote:
>
> does anyone know of any small low power reflective proximity
> sensors with a range of about a few centimetres, maybe four or
> five.
Sparky posted a diagram showing an infrared light beam bouncing off a
surface and reflecting back to a receiver. The trick was to have the
beam strike the surface at an angle, so it would only be received if the
surface was a certain distance away.
This may be more useful then it first appears -- definitely worth
experimenting with. For example, I've been controlling my stereo by
"bouncing" the signal from the remote off the ceiling: I need only point
it at a spot roughly halfway between the remote and the stereo. The
important point about this is, the ceiling is wood -- unfinished red
cedar to be precise. Definitely non-reflective in the normal sense, yet
it bounces an infrared signal very nicely.
Bruce
5902 Fri, 27 Aug 1999 21:10:29 -0500 [alt-beam] Re: New bot on the way(non BEAM) beam@sgiblab.sgi.com Richard Piotter Remeber how "packed" Japan is though! How many more people there do you
thing live in apartments that don't allow pets or animals. Now imagine
how many kids would be desparate for a robotic pet? My apartment doesn't
allow pets, and though I don't have cash for much, I do like robots.
They aren't pets, but they are a good show stopper! People gather around
them like it had fur and cute round eyes like it were a kitten! :)
Bruce Robinson wrote:
>
> Don Papp wrote:
> >
> > Slashdot (www.slashdot.org) had a story about
> > it yesterday, so if you look in the old news
> > you can check it out. Not sure if they had a link.
> >
> > There are no plans for an english version,
> > though the designers say it would be
> > theoretically possible.
>
> Which leads one to wonder just how successful the Aibo sales were in the
> U.S. The Japanese do seem to be more interested in these types of
> technological gadgets then North Americans.
>
> Bruce
--
Richard Piotter
richfile@rconnect.com
The Richfiles Robotics & TI web page:
http://richfiles.calc.org
For the BEAM Robotics list:
BEAM Robotics Tek FAQ
http://people.ne.mediaone.net/bushbo/beam/FAQ.html
5903 Sat, 28 Aug 1999 10:30:12 +0800 UJT/PUT as replacement for 1381? Arno Jansen
> I have just spent 4 hours to test the circuit of the photopopper I wnt to
> make. Just a standard circuit, but without the 1381's. There aren't any
here
> in Holland. I am quite annoyed that it doesn't work yet, but it's quite
> educative.
>
> As I first thought the 1381 was there to deliver a more or less stable
> voltage, I found out that it is there to swith the motor on to move to the
> light, and once there, stay there and not drive further. We spent four
hours
> to find a solution to replace the 1381. And we came to the idea that it
> might be a Uni Junction Transistor (UJT) or Programmable UJT (PUT). Is
that
> it? Am I right? If so, I just sleep in front of the electronics-shop
tonight
> and get a few UJT's tomorrow morning!!!
>
> So, my question in short: is the 1381 a UJT, or is a UJT a good
replacement
> for a 1381? I like to think so, but I am not a pro, so maybe some of you
> guy's can help me out here. Please......
>
> Best,
> Arno
Home