Alt-BEAM Archive

Message #02892



To: Chiu-Yuan Fang chiumanfu@home.com, Andrew Miller amiller@golden.net
From: Dave Hrynkiw dave@solarbotics.com
Date: Mon, 03 May 1999 01:31:49 -0600
Subject: [alt-beam] Re: Caterpillar


At 03:09 PM 4/30/99 , Chiu-Yuan Fang wrote:
>Dave was telling me about "PhotoPheeder". What kind of circuit did you use to
>control it? I'm trying out different circuits in my ATpV
>http://www.geocities.com/SouthBeach/6897/atpv.html
>and would love to see your solution.

Here's a bit of historia from when I was just getting into BEAM. Miller put
together a "bio" sheet for his better robots (hmmm, pre-genome!). The copy
he gave me has these details for the "PhotoPheeder II". Feel free (pending
Miller's approval) to copy this into any GENOME project. Best I can tell,
this device was constructed in early 1992, based originally on Mark
Tilden's HBS BEAMants:

Solarcells - 2 multicell packets, calc. cells; 5V nominal each

Caps - Twin 94000uF 5V drive supplies; one 4700uF 5V "reverse panic" supply

Battery - Two 3V lithium cells (currently dead, source for "reverse panic"
(Dave's note: the original photovore contest as per the BEAM rules allows
these lithiums)

Engine type - Twin HBS drive engines with 3.3k bias; nominal trigger 3.1V
- Single HBS reverse engine Nominal 2.7V trigger

Drive - Gear reduction; 3V cassette motoer; Tani type final drive from
modified printer paper feeders

Chassis - Paper feeders bridged by glued perf board; brass tubing and
stainless steel wire; Removable solar array and cct board.

Behavior:

The is the most complex of my machines. It starts with the most simple of
behaviors. Basic Phototropic behavior, with mechanical tactile sensors for
obstacle avoidance. A more difficult behaviors was introduced to allow the
machine to "aback up" should it enter a zone of darkness such as a cave.
This is accomplished by using a photo resistor to trigger the "reverse
panic" system powered by the lithium batter "body fat". In an attempt to
avoid potential problems with other competitors who follow the classic
phototropic behavior, this machine was created as a "semi light pool
avoider". That is to say that it begins its behavior with phototropic
intent, but when the light intensity becomes greater than a preset level
the machine will become "semi-photophobic". This behavior could be
considered self preservation, as the robot now avoids conflict with other
competitors who are holding Tilden's third law of robotics as the highest
priority. This light pool avoidance technique works best in low light
conditions such as 100W bulbs, but can be carried to situations with much
brighter and more uniform lighting. The introduction of a moving light
source, such as sun up/sun down, creates even more possible behaviors.


Background: As this was my first attempt at creating a photovore, it proved
to be quite a "voyage of discovery". Countless hours of frustration can be
directly attributed to this machine. The basic chassis was created to
challenge the line from the BRO guidebook which stated "... a photovore
need not be a modified tank to compete." in fact this was the second
chassis based on a modified printer feed mechanism. There are some obvious
disadvantages to making such a "heavy duty" driveline, but the most obvious
of which is partially compensated for by LOTS of solarcells. The machine
has, however, proved its worth as an All Terrain Vehicle. At one point
during the last competition, PHOTOPHEEDER actually climbed over another
competitor and dragged it around for almost an hour. The light pool
avoidance technique, although great in theory , aw immensely difficult to
implement. The analog nature of most electronic components, and the
resulting power losses caused endless problems. A functional circuit was
finally created using a photocell and a photoresistor in series to give a
current vs intensity rise that was much closer to a digital response.
PHOTOPHEEDER II was the 1993 world champion. I hope to expand this machines
"All terrain" style into larger robotic life forms in the future.

Regards,
Dave
---------------------------------------------------------------
"Um, no - that's H,R,Y,N,K,I,W. No, not K,I,U,U, K,I,_W_. Yes,
that's right. Yes, I know it looks like "HOCKYRINK." Yup, only
2 vowels. Pronounciation? _SMITH_".
http://www.solarbotics.com

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