by John Blankenship
and Samuel Mishal
If you visit a robot club or any
robotic function for that matter, it
is likely that you will meet someone
who is interested in humanoid robots.
Often, these enthusiasts are not particularly interested in building robots
that perform useful tasks. Instead, they
wish to build a robot that looks and
moves like a real person. They may or
may not want to endow their creation
with artificial intelligence (AI), but they
nearly always want to create the
illusion of life.
My interest in robotics has always
been very diversified and I too have
FIGURE 1.
Epoxy putty
was used
to turn a
Halloween
decoration
into this
head.
always been fascinated with the idea
of creating the illusion of life. Perhaps
that was a motivating factor that pushed
me towards another of my hobbies —
ventriloquism. It occurred to me that
the techniques used in puppet construction might be of interest to many
hobbyists interested in animatronics.
A typical ventriloquist puppet is
carved from wood or molded from some
form of composite material such as
plastic wood or papier-mâché. In either
case, the head cavity must be open
enough to add mechanisms such as
pulleys and levers to control the movement of the mouth and other
optional features such as moving
eyes, eyebrows, and eyelids.
If we are creating a robotic
puppet, the head must contain
all the moving parts found in
a standard puppet plus
appropriate actuators (motors
or solenoids) to effect the
movements. Since I wanted
the puppet to appear life-like,
it was important to animate
some body movements in
addition to the facial features.
In order to simplify the
programming aspects of the
project, servo motors were
used as actuators. This meant that the
overall size and weight of the puppet
had to be kept to a minimum. Keeping
the puppet small was no bother. To the
contrary, it was actually very intriguing.
Normally, a ventriloquist’s puppet has
to be big enough so that a hand can
be placed inside it to perform the
manipulations. With a small puppet,
everyone would know it was not being
controlled in the normal manner.
The puppet’s head in this project
is smaller than normal and it has to
contain even more mechanisms than
a standard puppet. If the head was
made from wood or composite materials, the required wall thickness would
reduce the size of the head cavity
even further, adding to the problem.
One solution is to use a plastic head
from a doll or holiday decoration. The
thin plastic shell would provide the
maximum interior space.
I found a Halloween prop that
was the perfect size, but (as you
would expect) it had a ghoulish look
that was not appropriate. I used
epoxy putty to fill in unsightly
wrinkles, alter the lips, add teeth, and
lift the cheeks. Epoxy putty is as easy
to work with as clay — but for only 10
or 15 minutes — so don’t try to do too
36 SERVO 11.2008
