process
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Kickoff
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The FIRST Robotics kickoff occurred on January 8th. At this time, the game, “Triple Play,” was first revealed to us. The object of the game is to score as many points as possible; and you can only score points by:
3 points for putting a small tetra onto a large tetra
"Owning” 3 goals in a row (like tic-tac-toe) by capping with your alliance’s tetras
Placing a small tetra inside a large tetra will score 1 point for your team.
Being inside your specified "zone" at the end of the match will score an additional 10 points for your team.
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Brainstorming
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Cybersonics attended a local kickoff event at Upper Darby Area High School. Afterwards, the team met to discuss the game and brainstorm concepts for the robot. A list of important attributes was created from this brainstorming:
High torque/power at low speeds for battling at goals
Closed-loop drive control
“Stang PS”-type virtual position control may be necessary for autonomous
Autonomous with camera
Tetra gripper and tower (arm or forklift)
High speed for autonomous, to create and maintain rows, then return to position at end of game
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Student portraying her
idea visually.
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Two students pitching
an idea to the group.
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Entire group learning about
the game and how the
robot will play.
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Mentor explaining the
rules one more time so
that nobody is
confused.
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Game Simulation
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Each student was given the opportunity to present his/her ideas to the team and later simulate them on the playing field. Then the mentors and students assessed the effectiveness of the design ideas based on the list of important attributes that was created in the brainstorming session.
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A tetra "hugger" idea being
tested with simulation.
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Attempting to create a
stacking system involving
the manual tetra loaders.
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Overall Look At The Game
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After the team discussion and simulations, we reached several conclusions about the tower system. The first was that we should utilize our limited height capacity by gripping the tetras toward their base and tilting them over the top of the goals. Our second decision was that the tower would need to be quite fast and have the capability to cap at least six tetras on the center goal. We also concluded that the drive system should be both powerful and fast so that we can push opponents aside when necessary yet still move quickly when we have an unobstructed path.
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Tetra Gripper
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Click Here To Go To Design Page
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Team members in the manufacturing and inventor departments divided in to four groups that each tackled an individual design concept for stacking tetras. After utilizing the inventor program and constructing prototypes, the groups enacted their designs on the playing field. The pros and cons of each prototype were discussed until the departments reached a consensus on which design idea to pursue.
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Click Image To View Animation (DivX required)
A design that would mesh inside the
tetra before a locking mechanism
rotated in to place.
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A gripper concept that pushes out
on the tetra, applying pressure and
forcing the tetra to stay in until it’s
released.
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Another concept that would use
pneumatics to close two fingers
inside the top of the tetra.
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Click Image To View Animation (DivX required)
This concept works similar to a forklift.
Two lifts slide under the tetra while
two grippers attach securely to the
sides.
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Tower System |
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Click Here To Go To Design Page |
Three ideas we considered for the tower system were:
multi-axis arm on a swiveling base (like a construction track-hoe);
three-axis arm;
telescoping, fork-lift tower
We needed a system that wouldn't create high torque loads at the joints but would be able to go high enough to cap the center goal with a number of tetras already in place. Since there is never enough time in a match, the tower’s lifting speed is critical. If possible, we would want to be able to raise the tower while maneuvering the robot without risk of tipping over.
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Model of a multi-axis arm concept which was abandoned early in the design process because the highly loaded joints would require fabrication techniques not available in our facility. Another drawback of this type of arm is that its high moment of inertia and complex motion characteristics would make it difficult to position the tower with a tetra on board while the robot was in motion.
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The tower on our 2004 robot used interlocked aluminum extrusions and cable drive to telescope up to 11 feet to reach the bar. This system was proven robust and reliable – able to lift our robot with two other robots partially supported. We selected this configuration for our tower, with one significant change: this year we would use chain drive instead of cables for greater strength and positioning accuracy. Two telescoping sections ride on a pivoting base section to give adequate reach and positioning range.
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Simplified layouts were used to find the reach and angles needed to position the tetras on the goals. Our target was to be able to place one or more tetras on top of a stack of up to six already there.
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Chassis & Drive
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Click Here To Go To Design Page
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The team initially constructed the drive system FIRST provided in the Kit of Parts. However, after the brainstorming process, we had decided that we needed a wider range power and speed. The gearbox in the kit was unable to meet our requirements, so we searched for a more adequate system. Eventually we settled on an Andy Mark gear box.
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Performance models were
generated in excel for the drive
system using the CIM motors and
various gear ratios. John V-Neun’s
DesignCalc worksheets proved
invaluable in this exercise and
enabled us to quickly select the
drive ratios for the speed ranges
targeted.
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The need for high manuverability
and power at low speeds,
contrasted with the possibility of
last-second dashes to cap and
return to end zone, lead us to
believe that a multi-speed
transmission would be a
requirement to compete at the
top levels. Though Cybersonics had
developed a two-speed
transmission for the 2003 robot, the
apparent robustness and ready
availability of the AM Shifter from
AndyMark, Inc. made it our choice.
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Constructed kit robot to learn its
capabilities and to serve as a
platform for the programming team.
Considered the kit frame too limiting
to use for our competition robot and
decided to use 8020, Inc. extrusions
as used by Cybersonics previously.
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The current competition frame
has a decisive edge visually and
performance wise over the
aluminum kit frame. The extruded
8020 aluminum provide the
strength of a solid rod, yet the
weight reduction to allow for greater
speed and load capabilities.
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