Rhyme of the Modern Submariner Concluded
camera whose output we could see
on one of the three monitors we were
allowed for the competition, but we
couldn’t do much besides look at the
OBS and vent. The OBS is three newtons
positively buoyant, but that still means
every 2 lb weight needs to be dislodged to free the OBS. We supposed
that the ROV might be capable of
such a brute force feat, but we were
looking for a more elegant solution.
It was time to pull out the drawing
board and design our own solution.
Our initial design was created in
the tradition of cool factor engineering.
We thought it would be easy to lift
everything at once—OBS and 16 lbs of
weights—with a crane type assembly.
The crane would remain on the surface
of the pool buoyed by pontoons, and
a powerful winch would lift everything
out once the ROV had latched onto to
the top of the OBS. Our design was
brilliant, it was elegant, it was simple,
it was effective, and it was against the
rules. We thought we had passed
muster on the restrictions on multiple
robots — our ROV and topside crane
would be physically attached and
operating from the same power source.
But no matter how intertwined we
were able to design our ROV and
pontoon borne crane, topside cranes
were against the rules.
It was time for Plan B, which
actually included a host of other
designs before we settled on our final
game plan. After considering vacuums,
claws, and pneumatic bladders, we
agreed upon a simple sweeping arm
mechanism and hopper. A simple one
degree of freedom arm would sweep
the weights into a hopper on the
bottom of the ROV so that they could
be taken to the surface. For our
temperature reading, we used an RTD
(resistance temperature detector) that
would be read by a panel meter. Now
that we had our design, all that was
left to do was everything.
Everything
Our first order of business was
to acquire the necessary parts.
Thanks to years of robot building and
competitions we had plenty of extra
parts to donate to Tau Beta Pi’s bot.
One of the biggest parts donors was
actually one of our Vex Robotics kits.
The Vex frame pieces happened to be
the perfect size for the hopper frame,
and a plate from the Vex kit was
perfect for our arm — the pattern of
holes would nicely minimize our water
resistance. We also used Vex pieces
for a guide and shield for our RTD
temperature probe.
The material for the hopper itself
was also scavenged from another
robot — we borrowed a green mesh
from Delta MO, Team 1079’s robot
from the 2006 FIRST season. We still
needed a motor for our arm mechanism, and our search was complicated
by the fact that it needed to be waterproof. The motor also needed to have
the right balance of torque and speed
— enough torque to push around the
weights and a slow enough speed to
be controllable.
We decided on a type of motor
that had served us well in the past.
A Maxon motor, used by Cosworth
Racing to operate the butterfly valve
on the air intake manifold on a racing
engine was what we used for the
drive trains in our combat robots. The
motors were robust, high torque, and
environmentally sealed. They were
also lightweight and small, so they fit
perfectly with our compact ROV.
Some extra all thread, wires, and
a switch were all we needed to wire up
our arm mechanism. Adding our new
switch into the existing wiring of the
ROV proved to be taxing because the
overcrowded control box was difficult
to navigate safely with a soldering iron.
Thankfully, the necessary wiring was
fairly minimal and by following the
example of the original control box we
had another working switch in no time.
The last component of our ROV
was the temperature probe. We
wanted to use an RTD instead of a
thermocouple, and finding the right
parts proved to be laborious. We
eventually found what we were
looking for from Omega, and we also
purchased a 50 ft RTD extension wire
for a grand total of about $150.
The last piece of our ROV puzzle
was a panel meter. We found the
A HYDROTHERMAL VENT.
perfect solution from Automation
Direct — a panel meter that could
take input from RTDs and output
temperatures in Fahrenheit or Celsius.
The panel meter cost about $150,
but we thought the expense was
worth the convenience and accuracy.
Now it was time to make the final
preparations before the competition.
What We Have Here
is Not a Failure To
Communicate
Most robotics competitions simply
ask teams to build a robot and bring it
to the event. There’s nothing wrong
with that, but the MATE Competition
asks a bit more of teams so that they
can practice the valuable skill of
engineering communication. As a
part of the MATE Competition, teams
are asked to prepare an engineering
presentation, a technical report, and
a poster display.
After scrambling to finish a robot
BRANDON LAUNCHES THE ROV.
SERVO 09.2008 15
