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| FIRST Robots
BUILT TO BE
TOUGH
While other FIRST teams build robots, FIRST Team 141
from West Ottawa, Michigan Public Schools annually builds
a WO-Bot. With participation in FIRST Robotics
Competitions dating back to 1999, the team has many
years of experience to draw upon. Based on the expected
intensity of the 2006 FIRST Robotics Competition, the team
decided that a strong drive system and a solid robot base
would be essential. Experience served them well, as the
team designed a robot capable of delivering and receiving
aggressive play on the field.
Quality is a measure of a system’s ability to meet design
goals. A robust robot is one that is well designed and
constructed to operate match after match. Over the course
of the season, Team 141 played 46 matches and never had
a component fail. By anticipating the on-field action,
Team 141 designed a robot to maximize performance and
minimize maintenance.
Developing a Design Plan
The team’s on-field success began with a structured
approach for decision-making. An analysis process known as
the Pugh method was used to examine the competition and
develop initial plans for the robot.
The Pugh method was applied to evaluate design choices
against performance criteria. Used with three or more alterna-
tive choices, the Pugh method designates one choice as a
benchmark and then compares every other choice to that
standard for each design criteria. The value of the criteria can
be weighted to emphasize the importance of some criteria in
comparison to other design factors.
ONE ROBUST
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TEAM 141
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Quality Award
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Design alternatives for shooting,
propulsion, ball pick up, and storage
were evaluated against a list of 40
design attributes. One design was iden-
tified as the baseline option, and other
alternatives were compared against the
baseline to determine if the alternative
was better than, the same as, or not as
good as the option. A point value was
assigned to each evaluated option (1, 0
or –1) and multiplied by a weighting fac-
tor for each design attribute. The sum
of the scores for each alternative identi-
fied the optimal design.
As an example, three driving meth-
ods were examined: a four-wheel drive
system where each wheel had its own
motor, two wheels that could be
steered (much like a car), and a design
that used retractable wheels. Some of
the important design attributes included
serviceability, ability to be manufactured
in four weeks, traction, and maneuver-
ability. The Pugh analysis guided the
team to a drive system that maximized
pushing power when going straight and
used retractable wheels for increased
maneuverability during turns.
In addition to using the Pugh method
to make design choices, the weighted
design attributes were a declaration of
principles that helped keep the team
focused throughout the design and
construction process. A team member
began to stray from the design guide-
lines, could be reminded of the estab-
lished design requirements and so
realign that creativity to honor the
team’s ranked list of design attributes.
Team 141 also applied this structured
decision-making method during the
competition when teams selected part-
ners for the final rounds of play. A list of
team and robot attributes was identified
and potential alliance partners were
evaluated based on their predicted per-
formance in each category. With this
decision-making methodology, Team
141 strategically evaluated all factors
and selected the optimum partners to
create a winning alliance.
Evolutionary Design
Improvements
A series of tests and reviews advanced
the robot’s performance. Balls were col-
lected from the floor and lifted to the top
of the robot, where they were shot or
stored. Large-diameter wheels provided
clearance to collect balls at the front of
the robot, with a set of brushes placed
in front of the wheels to prevent the
robot from running over any balls. Once
under the robot, the balls were guided
by a set of rails to an elevator that lifted
the balls from the floor.
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Large, pneumatic wheels provide ample
clearance for a frame that doesn’t interfere with
ball collection. Brushes in front of the wheels
deflect the balls away and prevent the wheels
from running over balls and possibly interfering
with the drive system.
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