Alt-BEAM Archive
Message #05542
To: beam@sgiblab.sgi.com
From: Sean Rigter rigter@cafe.net
Date: Thu, 05 Aug 1999 15:34:34 -0700
Subject: [alt-beam] touch sensor, Robot Jurasic Pond, etc
Summer time and the living is easy!
What's that? Help wanted to design a RJP type environment for aquabots?
Robot Jurasic Tank/Pond/Pool/Lake/Sea/Ocean?.
Well more on that later but first:
cbrenizer wrote:
>Anyone have any experience 'hacking' resistive sensors like this?
Great potential! "Nudge, nudge, wink, wink, say no more".
These particular transparent touch sensors are used as overlays for monitor or
LCD screens but similar technology can be used for digitizing pads ie mouse
pads. In general, these use two resistive sensor sheets superimposed but
separated by a thin layer of air. Each sensor sheet has contact strips along two
of the four edges ie. one sheet = top and botom edges / the other = left and
right edges. Similar to a PC joystick, these sheets act as X and Y axis
potentiometers when a voltage is applied across each sheet through the
conductive strips, alternately first to one sheet then the other. When pressing
down on the sensor, the location of the "point of contact" on each sheet is
determined with a 2 channel A/D converter to sense the X and Y potentials at
the point of contact. These two values provide the coordinates of the point of
contact.
A PC joystick can be used in a Bicore or Monocore servo loop to position a 2DOF
head (with an arm attached?), this touch tensor could provide a similar
function. A simpler touch "ribbon" around the circumference of a bot can be used
to determine the "potential" (ie location) of a "point of contact" and (with a
sample and hold device) could use this to directly influence Microcores or
Bicores to generate a corrective action or motion.
Riding along a nice little Beam of "techciting" ideas if water is thought of as
a resitive fluid ocupying a 3D volume, then similar to a touch sensor, a voltage
alernately injected between a number of points (sides, corners etc) in this
volume will set up potential gradients which can be detected. One could use the
touch sensor principle to create a 3D joystick by using a "potential" probe with
a conductive tip inserted into the tank. Of course the "tank" in this case can
be quite a small volume (eg 1 cubic inch).
Speaking of a Robotic Jurasic submarine park, a submerged "Subbot" could use
the same principle to determine it's position coordinates in a much larger
volume of water. Instead of fancy A/D converters, Beam aquabots could use
"potential" gradients in a servo loop sliding along potential gradient lines
perhaps "feeding" on the larger gradients (or directly from the electrodes).
Similarly motion/behaviours in response to stimuli other than light eg
Thermotropic or Iontropic behaviours (eg underwater thermal and ionic gradients)
thereby creating an different kind of autonomous 3DOF aquabot. Well just a start
but maybe the stuff contests are made of!
enjoy
wilf
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