GEERHEAD
Full view of air hockey robot, table, computer, and system.
Close-up of air hockey robot.
forms the side rails of the air hockey
table. Because the MDF walls were
deflecting the puck on impact, the
trajectory of the puck moving away
from the walls was different than the
team’s algorithm had accounted for.
The new trajectory affected the puck’s
speed and angle of deflection off the
walls. This had a negative affect on
their algorithm.
According to Dr. Stienecker,
because the algorithm assumes
that the angle of incidence equals
the angle of deflection (that
the puck hitting the wall at a
45-degree angle will bounce off at a
45-degree angle as well, for example),
and because the MDF walls moved
when struck by the puck, the puck
would bounce off the walls at a
different angle than the algorithm
could predict.
To resolve the issue, the
Department of Technological Studies
team fabricated aluminum sides for
the air hockey
table. The
aluminum does not deflect the puck
in a way that is out of synch with
the team’s equations and algorithm.
“This is similar to the difference
between bouncing a basketball on
cement and bouncing it on a
trampoline. If I were to bounce-pass
a basketball to you on cement, it is
pretty easy for me to judge were I
should aim to bounce, but on a
trampoline it would be anybody’s
guess as to where it would bounce,”
says Dr. Stienecker.
According to Dr. Stienecker, the
robot employs an automatic puck
return system so that if the human
player scores, the system delivers the
The Department of
Technological Studies at
Ohio Northern University
built this air hockey puck
return system. The ONU team
created the return system to
relieve the human opponent
of manual retrieval of the
puck after a score. The
return system uses a chute
and conveyor to bring the
puck back to the robot’s
human competitor.
“The puck enters the
score pocket, slides down
the chute, triggers a
photo-electric sensor, and
falls onto the conveyor,” says
Dr. Adam W. Stienecker, PhD,
assistant professor,
Department of Technological
Studies, Ohio Northern
University. After the puck
triggers the sensor, the
conveyor activates long
enough for the puck to travel
and fall into the container at
the opposite end. Then, the
system flashes the lights at
the top of the frame, alerting
the human player that they
have scored against the
robot.
“The container is
located beneath the human
opponent’s score pocket
and is easily retrievable,”
says Dr. Stienecker.
12 SERVO 06.2008