FIGURE 8. An extended joystick provides
control of the puppet’s functions.
easy while being hidden from view.
The clothes for a small puppet are
not easy to find. An outfit for a 12-18
month old child was tailored and modified to give it the correct proportions.
The features on this puppet allow
for a variety of emotions. When the
puppet lowers his eyebrows, for
example, he looks mad. Raising the
eyebrows while keeping the mouth
open will express surprise.
In order to make control of the
puppet as intuitive as possible, all the
movements on the puppet were
associated to similar movements
on an extended joystick. Figure 8
summarizes these movements.
Some of the puppet’s actions are
provided automatically by the computer,
thus making the manipulation easier
for the user. Buttons on the extended
joystick, for example, can be programmed to provide specific movements
for the arms, or head movements for
yes and no. All of these motions could
be created by controlling the puppet
manually with the joystick, but
preprogrammed movements can have
pre-selected servo speeds and limits so
that the automated movements can
be as lifelike as possible. Furthermore,
• Twisting the stick
• Moving the stick forward/backward
• Moving the stick left/right
• POV hat left/right
• POV hat forward/backward
• Trigger (firing) button
the arms, head, and body all have
small random movements programmed into them even when the
puppet is not being controlled. This
simulates life-like restless shuffling.
At this point, we are ready to
create the program to bring the
puppet to life. We used RobotBASIC
because it has the ability to read and
write to all the ports on a PC (parallel,
serial, and USB). A Parallax USB multi-servo motors controller www.Parallax.
com) makes it easy to control the
servos because it will simultaneously
move the servos using the positions
and speeds requested by the
controller program and maintain those
positions without further intervention.
The RobotBASIC program reads the
joystick and then commands the servo
motor controller module to position the
motors accordingly, reflecting the positioning of the joystick and/or button
presses. The program is too long to list
here in full, but the listing in Figure 9
• Rotates the puppet’s head
• Tilts head forward/backward
• Tilts the body left/right
• Moves the eyes left/right
• Moves the eyebrows up/down
• Opens the mouth
shows a representative sample of some
of the subroutines. You can download
the full program from www.Robot
BASIC.com. It is well commented so
it should be easy to follow the logic.
The techniques demonstrated in
this article can be valuable in a wide
variety of projects. Even this project
itself can be the starting point for further
ideas. For example, instead of using
the humanoid form as a manually
controlled puppet, you could place it
under automatic computer control. If
you combine voice synthesis and voice
recognition with the puppet’s ability to
simulate emotions, it is easy to imagine
an amusing interactive robotic display.
Of course, the techniques shown
here can be utilized in robotic projects
involving humanoid forms and other
animatronic characters. Constructing
your own computer-controlled puppet
allows you to have the features you
want along with the ability to control
it as you see fit. SV
Announcing the Gears Heavy Metal Robot Kit
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Heavy Metal is engineered for rigors of daily use in classrooms, standing weight!
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All drive components are keyed and broached.
Competition all-metal gearhead motors, gearbox
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Contact Mark Newby the World's
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*VEX Robotics is a mark of Innovation First, Inc. and FIRS T refers to © US FIRS T (Foundation for the Inspiration and Recognition of Science and Technology)
SERVO 11.2008 39