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FRC 2013 - Ultimate Ascent

This was our rookie year of competition, and our robot was named Holly, after our holonomic drive base.  As you can guess from our rookie status and robot name, this was quite an ambitious (triangular!) drive base consisting of three omniwheels, located at each corner of an equilateral triangle.  This unique design meant that Holly was extremely maneuverable robot, but due to some time management issues, she had a bit of a last minute game piece (Frisbee shooter).  Holly has turned out to be a very durable robot and since the competition she has been used for outreach, practice, and was even adapted as a second competing robot for the 2014 DDU.

We were awarded the Rookie Inspirations Award that year, and are very proud of our achievements with Holly.

holly_2

Holly in the pits just before competition. This was taken before we re-branded to The Drop Bears, hence the blue shirts.

Game

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The game for the 2013 FRC competition was Ultimate Ascent.  During this competition the robots had to team up and shoot frisbees into one of three goals.  Additionally, you could earn extra points by climbing up the towers in the middle of the field, and the higher the robots got, the more points were awarded.  However, the robot had to end the game on top of these towers for the climb to count, which introduced an element of strategy. This lead to some teams specializing as shooting robots, and others as climbing robots.  We were a shooting robot.

workingGame Piece

The game piece (Hopper) was designed to intake frisbees, index and feed them, then fire at the goals. We opted to receive our frisbees from the feeder stations at the end of the field. We figured this was the safest option as the frisbees would be in a reliable and predictable configuration as opposed to collection off the floor. Our hopper was a curved track holding 4 frisbees as many as the rules allowed. A number of servos indexed the frisbees into the firing position.

Shooter DiagramFiring

The frisbees were forced between the spinning wheels and a high friction rail. This method imparted spin to the frisbee, the spin was vital to a stable flight. The frisbee was pushed into the wheels by the firing pin. 

A schematic of this system is shown to the right.

vectorCrossoutOutcome

The design proved to be sound in theory and when everything worked it was very effective. However, over distance the frisbees would become unstable making a reliable shot on goal difficult. As a result we adopted a very steep firing angle and shot close to the goal. The hopper had a tendency to jam as the servos and firing pin where all manually controlled by the co-driver. This system needed to be automated to improve reliability and to free up the co-driver. Unfortunately our team didn’t have the programing skill at the time to build or test this system.

Drive Baserobot_omni_3wheels

Holly is really defined by her unique hexagonally shaped drive base, one that has continued to prove useful over the years. The three wheel holonomic drive system sometimes called a kiwi drive. It utilises three independently powered omni wheels, which resemble normal wheels with a series of free spinning rollers perpendicular to the axis of rotation. These wheels are mounted 60 degrees from each other allowing vector cancellation  facilitating a huge degree of mobility and flexibility when driving.



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