GEERHEAD
This is the puck striker. The
puck striker attaches to the end
of the robot arm in order to
increase the speed at which the
robot strikes the puck. The image
shows the striker without the
motor, the cam, the springs, and
three of its disc quarters. The
image also shows the base and
one disc quarter.
The motor would appear
in the large hole on top of the
striker. The shaft would turn
and its cam would strike the
half-circle protrusion on top of
the disc quarter (shown). This
would push the disc quarter
out for a split second until a
spring would bring it back in
again, according to Dr. Adam
W. Stienecker, PhD, assistant
professor, Department of
Technological Studies, Ohio
Northern University.
puck to them again. The system senses
when the puck has been delivered
to the robot’s goal and returns it
beneath the table to a receptacle in
front of the person. When the human
opponent does score, the system
lights up indicating their success.
Programming
A human competitor keeps the
puck moving during play to provide
motion similar to what the robot
might experience when picking a part
in motion in an industrial setting. The
robot uses a machine vision system to
see the puck and original programming created by the team in the
Department of Technological Studies
to strike the puck repeatedly (to play
air hockey).
The air hockey robot vision
system uses a Point Grey Flea2 model
camera. The camera attaches to the
robot’s frame. The firewire camera
is a one-third inch, color CCD. The
camera (with the help of the VisionPro
Quickbuild software application)
snaps 30 images of the entire
table view every second. The
camera transmits each image to a
computer. The computer
uses a non-linear
equation to remove
image distortions so the
current position of the
puck can be clearly
distinguished in the
image. The VisionPro machine
vision software then distinguishes
the puck and transfers its x,y
coordinates to another algorithm
on the computer.
Still on the computer, a VB
.NET program keeps track of
previous and current x,y values.
This helps the program to
determine the trajectory of the
puck. This program uses those
values to determine where the
robot should move in order to
strike the puck. The algorithm
sends this new value — a point
on the table near the puck — to
the robot controller. The robot
controller completes some
additional math to decide how
the robot should move to get to
that point on the table. SV
A close-up of part of the air hockey
puck return system.
Another view of the air hockey robot and table.
RESOURCES
The Point Grey camera
(the Flea2 model) used in the
air hockey robot experiment.
Department of Technology,
Ohio Northern University
www.onu.edu/a+s/techno/
KUKA Air Hockey Robot
on You Tube
www.youtube.com/watch?v=
AidLoq9eW8M
KUKA, makers of the robot used
in the air hockey experiment
www.kuka.com/usa/en
Rapid prototype 3D printer
www.dimensionprinting.com
SERVO 06.2008 13
