Our Robot

We built a symmetric "vehicle" whose front and back are virtually indistinguishable. The robot is capable of passing the balls underneath itself, and it has two gates on both the front and the back. These gates can be raised or lowered in order to capture and release the balls.

Structure

Our robot consisted of two side walls with a horizontal square platform on top. Each wall contained three motors that powered a gear chain extending down to a pair of wheels. In addition, each of the two walls had a shaft encoder (break beam sensor) to measure the spinning rate of the wheel pair attached to that wall, as well as a servo motor responsible for lifting one of the gates. Finally, mounted into the walls were pairs of sensors transmitting/receiveing infra-red light (an IR LED on one wall emitted light to be received by a phototransistor on the opposite wall). These sensor pairs were to tell the robot if there were any balls in its interior (the balls would break the IR beam between the sensors in the pair, i.e. the transistor would receive no light).

The platform was used to hold the motherboard and the battery pack, as well as the IR beacon tower (an IR transmitting device that could receive the signal from the same device on the other robot).

Strategy

We decided to go for the "blocker"-type strategy. Namely, our robot would knock in the two balls closest to it, and then race to the opponent's half of the table, wait for it, and prevent it from scoring points by resisting its motion. The symmetry of the robot was very useful, as it only needed to turn at most 90 degrees in order to score two balls in the beginning of the round. We were also hoping that our robot would be one of the fastest in the competition, as we used all six motors to drive the wheels and a 27:1 gear ratio.

Outcome

Our best matches were played in the lab. The robot usually performed very well there. Things were different in 26-100, though. We were extremely unlucky in the first round, as we had one of the very few robots that could score more than one point but were set to play against another such robot. At that point we haven't developed the resistance part of our strategy, and despite having scored three points our robot was too weak to overpower the opponent, which managed to get the deciding ball in towards the end of the round. It should be noted that this match was one of the most spectacular in the first round. Bottomline: we lost, 3-6.

The first round was bad luck; the second one was a disaster. After the organizers had repainted the table surface the night before the contest and changed the friction on the playing surface, our robot failed to make a 90 degree turn properly. Even our carefully designed calibration routine couldn't help us fix the problem. The robot made a heroic effort to grab the first ball but then didn't manage to allign itself correctly against the boards and ran into the obstacle seconds later. That ended the competition for us as we lost our second game, 0-3.

In the mock contest held five days before the main event we made it to the second round with a 3-0 win over Team 13. We then lost 1-3 to Team 25 due to a gate failure.

Summary
 
Although we were very unlucky during the contest, we had a lot of fun during the IAP. This class is something MIT is famous for; this is something that makes this place special. We are proud of being part of this year's 6.270.