Renegade
Team 9: The Outlaws

Renegade In Action

Renegade rocking the battlefield

During the competition, Renegade won its first three matches, but lost to the #1 and #2 teams in two consecutive semifinals to take third place overall.

Top View

A better view of the arm

The HappyBoard is secured under the gray roof. The battery and the gyro rest on top of it.

Back View

Remnants of our bomb release mechanism

This motor is impossible to remove because it is so strongly attached to the back of the robot. The HappyBoard is secured vertically in the empty space inside the robot.

Bottom View

The chassis of renegade

These are the gearboxes for our wheels. Each one has a 75 : 1 gear ratio. Our robot was sturdy enough to survive the three-foot drop test.

Bomb-release mechanism

Our failed attempt at releasing the bomb

We planned to use this to release the bomb, but it was too hard to implement, because it had to line up perfectly with the gear box, a feat that was beyond the reach of Renegade's claws.

Renegade In Progress

20-something hours before the competition

The funky pattern you see on top the robot is called the fiducial pattern. It tells the vision positioning system that our robot is part of team #9.

The Outlaws

Ordered alphabetically and by decreasing height order

This photo was taken after we won third place in the competition. From left to right: Charlie Gordon, Carrie Liang, and Qian Long.

About

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» Challenges
» Tips & Downloads
» About Renegade
» About The Outlaws

Home

Welcome to our website, featuring our robot, Renegade, who placed 3rd in the competition. Feel free click on the tabs to the right to find out more about the team and the robot. In the depths of these pages, we have documented the highlights of our IAP experience regarding designing, building, and programming our autonomous Lego robot. We hope this site provides guidance for any future or current 6.270ers out there.

Check out the competition webcast at 0:45:45, 1:45:30, 2:18:00, 2:37:00, and 2:53:00 to see Renegade in action.

Robot Design

The basic design of Renegade consists of a claw and arm mechanism which traps balls in its claws and dumps the balls over its back. The claws are turned using four gears, and a servo, attached to another gear is used to turn those four gears. There are plates attached to the bottom of the claws that are used to hold balls that it grabs. Since the servo used for the claws has a lot of weight, two servos are needed to power the lever arm, so that it is able to successfully lift a tennis ball and dump it (hopefully) over the rift.

The chassis of Renegade follows a differential model, in which the two back wheels are each powered by a different motor and the two small wheels in the front are free rotating wheels. The gear box for each wheel has a 75 : 1 gear ratio.

Strategy

Since Renegade is mainly designed to pick up tennis balls, our strategy consisted of initially pushing the four tennis balls near the rift and then going for the tennis balls. There is an algorithm in the code that ranked the balls on the field by radius and then distance from Renegade. This ensured that our robot targeted the closest tennis ball after the initial sweep of the four golf balls in the front.

After Renegade traps a ball in its claws, it moves backwards until it hits the beam in the middle of the playing field and then dumps its contents over to the opposing side. In the case where our robot gets stuck, there is a timeout in place to let it skip to the next command. If all the tennis balls are removed from our side, then Renegade will target the golf balls with similar commands. Sometimes, Renegade is not very accurate, but it can try to account for that in its speed.

Challenges

We had several challenges in the construction and design of our robot.

In our original design, we wanted our claws and arm to lift balls into a basket on the back of the robot which dumped its contents over the middle beam once it was full. However, because the vision position system that allows our robot to navigate required a fiducial pattern directly on top of the robot, it was no longer possible to have a basket into which balls are dumped. Our next and final design simply had Renegade dump balls over the top of the robot, which ended up being an effective strategy.

Initially, we tried using one servo to lift the arm, but since the servo and gears attached to the claws contained so much weight, it was not strong enough to lift the entire contraption, so we ended up using two servos to lift the arms. The crucial element in this design was that the servos have to be exactly aligned to obtain maximum torque.

Our most difficult challenge, one that we were unable to resolve, was attempting to release the rift ceiling bomb. Not only was it difficult to construct a gear box with enough torque to spin the gears for releasing the bomb, it was also extremely difficult to navigate Renegade so that it aligned up properly with the bomb's gear box. The first few gear systems that we constructed often overheated the motors due to high speeds, and we ended up making a 25 : 1 ratio gear system that seemed to be able to turn the bomb's hear box without overheating the motors. However, we were unable to navigate the robot backwards to the target consistently, and when the robot did reach the target, we had trouble getting our robot in the right position to exert enough pressure for the gears to spin. In the end, we decided that this endeavor was too hard and that we had spent too much time (36 hours) trying to implement this strategy, so we stopped trying and moved on to other things.

Tips & Downloads

Tips

— Look through the course notes before you begin

— Work near the practice playing field where the TAs are clustered

— Solder well in the beginning so motor wires don't break in the middle of the course

— Come to lab every day

— Know when to give up and move on

Downloads

Download our umain.c file, released under the MIT license.

About Renegade

The name "Renegade" comes from the game Bang!, in which the player who is the Renegade must be the last player standing to win.

Renegade is superior to all other 6.270 robots in both design and implementation, in both mechanics and programming, in both speed and strength, in both precision and accuracy, and in both brains and brawn.

About The Outlaws

Our team name, The Outlaws, is another reminder of how much we like to Bang!

We are three freshmen from New House, Charlie Gordon, Carrie Liang, and Qian Long. We are awesome.

Charlie Gordon was the programmer. He was also just awesome in general. He also designed the website (kind of).

Carrie Liang was our mechanical genius. She also built the arms.

Qian Long was our Innovator and Implementor of Ideas. She also soldered each of our motors again and again.

"I the Renegade. I squeeze and dump." — Renegade

Renegade Team 9: The Outlaws