From: "Jonathan Mills" <jwmills@moose.cs.indiana.edu>
Subject: Re: Stiquito, A Small Nitinol-Propelled Robot
Summary: More detail about a simple robot
Keywords: Stiquito, Sticky (Stiquito's daddy), circuit reference, LLAs
Organization: Indiana University, Bloomington
Date: Sat, 26 Sep 1992 17:32:52 -0500

In article <ws!p8+=.nagle@netcom.com> nagle@netcom.com (John Nagle) writes:
>       The document describes a rather simple version of the thing.

John is correct.  Stiquito _is_ very simple, but was intended to be
simple.  This is because we planned to, and are, using the robot in
volume ("ant colony").  Effort was made to make the walking part
buildable by students who might not have much mechanical expertise.
A consequence is that this "robot" will not compare favorably to
those with multiple-degree-of-freedom legs, or sophisticated grippers,
etc.  On the other hand, Stiquito is a good starting point to use
to investigate nitinol-actuated devices.

A more complex predecessor, "Sticky," has legs with two degrees of
freedom, nitinol actuators inside the body tubing, and can carry
6 to 8 ounces.  It is correspondingly more complex, and gains
structural stability with modularity at the expense of complexity.
Although Sticky can be assembled by hand, and disassembled with a
bent paper clip, it resembles a Chinese puzzle.  I'll be glad to
send photographs of Sticky, or perhaps digitized photos of a
disassembled robot, with the assembly sequence, that could be used to
show how to make one.  The cost of Sticky, minus electronics, is
about $20.  Sticky + miniboard may be more what the robotics
community currently expects.  I'll help all I can to satisfy that
expectation.


>The "robot kit" actually yields a six-legged device with the three legs
>on each side tied together electrically.  The legs advance in a rachet-like
>fashion, under the control of a pair of manually-operated pushbuttons.

Again, John is correct.  However, the legs do not have to be
hard-wired in a tripod gait.  As is, the kit can be used to experiment
with other gaits.  The manual controller is also useful to verify that
the legs work.  And, sad experience with early oscillator circuits
that powered the legs for too long, damaging them, led me to build the
manual controller so I could check the robot out quickly.


>References are made to future VLSI-controlled versions, but that's not
>what you get.

This is true.  The technical report, TR 363a, is one of a series of
reports on work with these robots.  Please accept my very sincere
apologies if you feel you have been mislead.  I pointed out in the
original post that you had to add a controller, etc.  I understand
the disappointment that Stiquito doesn't do more than it
does, but I have also received very encouraging notes from
others who plan to use Stiquito-clones in their research.  Don't
give up yet because...

A mailing list is being set up by folks at UC Berkeley to monitor
advances in projects, designs, and answer FAQs about Stiquito-style
robots.  Subscribe to this list (instructions should be posted soon),
and you'll get all the news as it breaks.

I plan to post descriptions of the VLSI circuits that John mentioned
within a few months in a draft of TR 363b (please note the "b"),
"Sensors and Controllers."  Other circuits will be posted next week.

Already built and tested is a Braitenburg Bug based on Stiquito that
is phototropic, and programmable as either a photophil or a
photophobe.  It uses two independent oscillators driven by photo-
transistors.  The photo-transistors can be placed in the circuit
to make it stroke-length-variable, or stroke-rate-variable.  The
circuits are similar to the incandescent lamp flasher found on
page 17 of Forrest M. Mims III pamphlet "Engineer's Mini-Notebook
Optoelectronics Circuits" available from Radio Shack as catalog
number 276-5012.  Although nitinol is similar to the tungsten
filament on a lamp, there are three legs to consider:  add extra
2N2222's, one for each leg, to avoid overheating.  Be sure to
hook up the legs before powering the circuit or you risk damaging
the transistors.  Be very careful that the circuit oscillates
slowly, or you may damage the legs.

Almost finished and next to be tested is an IBM PC interface that
can drive Stiquito from a serial port.  It may be possible to drive
Stiquito, each leg independently, from a PC parallel port.  I haven't
tried it yet, so check the load imposed on the port as a whole if
all six legs are driven at once:  that will draw about 1.2 amps, more
than the port may source.

The VLSI circuits John mentioned are the topic of current research.
The first types are field-programmable gate arrays from Actel that
my students and I are using to implement frequency-modulated
controllers for the robot. The idea is to sense light and pressure
then use the inputs to generate trains of pulses at intervals to
cause the legs to walk at different rates, turning the robot, moving
it backwards, etc.  The legs have ratchet feet angled in different
directions so the robot can walk backwards, sideways, etc.

The second type of VLSI circuits are custom analog circuits
fabricated through MOSIS.  They are called "Lukasiewicz Logic Arrays,"
and have been the topic of my research since 1990.  I built the robots
as a platform to work with these circuits.  These "LLAs" use a
continuous-valued logic that can be interpreted as both a logic and
an algebra.  Using the algebraic interpretation, LLAs act as single-
transistor directed differentiators.  Using the logical mode, the
LLAs can be used to build fuzzy inference engines.  Both modes use
the same device structure.  In my paper that appeared in the 1992
22nd Symposium on Multiple-Valued Logic ("Area-Efficient Implication
Circuits for Very Dense Lukasiewicz Logic Arrays), a simple but fast
silicon retina was briefly described that used one transistor per
pixel as the computational element.  The rest of the computation was
done with wire.  Using LLAs, and a fuzzy controller I simulated this
summer, my next step is to put both on a MOSIS tiny chip, and use it
to drive Stiquito as a Braitenburg Bug that responds to more complex
patterns, such as textures.

But until the thing walks and follows a texture, it's vaporware.
I'd feel comfortable sending you published papers, but contact
me directly for reports on the LLA project.

>
>       A $100 kit with more smarts would be much more interesting.
>
>					John Nagle

Very, very true.  For now, the ftp access to the report is working.
Try building a Stiquito, (the sources of all materials, including
telephone numbers are listed in the technical report -- you DON'T
have to buy the kit by any means), subscribe to the mailing list,
and let your creativity flow.  And have fun, everybody here who has
seen Stiquito the Braitenburg Bug walk has immediately thought of
six impossible things to do before breakfast.

"Sic ago!"

"Just do it!"

Sincerely,
Jonathan


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