Autonomous Robot Design Competition - 6.270

Team 24 members: Punyashloka Biswal '05, Andreea Chisca '05, Giovanni Talei Franzesi '05. Time: IAP 2003.

Our robot, "The Uncrushable Mother Russia", took the challenge prepared by the 6.270 organizers and prevailed in true communist fashion.

Strategy The robot moves down to the lava island, places a lego box with a moving top over the cup, goes back up to the top of the competition table. It searches for a ball of its own color in all possible corners until it finds a ball. It picks it up with its arms. Then the robot moves nack to the lava island. Since the box is controlled by a servo connected to the main robot, the moving top opens once the robot arrives there. The ball is placed in the cup, and the robot starts 'defending' the cup from the opponent's robot.
Design The robot has two wheels controlled by a differential drive. The motors control the wheels through a gearbox with a 1 to 45 ratio. THe two arms are mounted at the front of the robot, between the wheel gearboxes. Each arm is controlled by a motor and a servo. The servo controls the horizontal movement of the arm, while the motor controls its vertical movement. The gearbox for the arm motor has a gear ratio of 1 to 225. Such a large value is necessary for a successful raising of the ball, which is 4 inches in diameter. The ball is recognized by light sensors, and then the arms move horizontally toward each other and then vertically together. The ball is released simple by opening the arms horizontally. The lego box which must cover the island is controlled by a servo connected to the main board. The mechanism for releasing the box is fairly complex: the servo, in the innitial position, controls a gear which can rotate and thus lower the box from a vertical to a horizontal position. Once in the horizontal position, the robot pulls away and thus releases the axles connecting the box and the main robot. The connection between the two is made through the servo wire and a required lego tether.
Implementation and Details The majority of the movements of the robot are controlled by the software loaded on the handy board and by the sensors mounted on the robot. The different sensors are: CDS cell for the starting light, CDS cells in connection with LEDs for reading the color of a ball and for following the back and white lines on the contest table. Three CDS/LED pairs are mounted colinearly on the bottom of the robot to facilitate line following, as determined by the software. Bump sensors allow it to react when it hits the cup or the walls. Shaft encoders and rotational potentiometers measure allignment on the wheels and arms: in order to get perfectly straight movement, the shaft encoders on the wheels control fow fast the wheels are turning in relation to each other. Similarly, the potentiometers control the vertical movement of the arms, which must move together in order to lift the ball successfully.
Practical and Amuzing Facts The robot building is much more complex than described above. Each piece of hardware and software must be tested and modified many times before it acquires its final shape and control mechanism. Lego parts are sometimes difficult to use and the different electronic parts seem to have lives of their own at 5 am. Otherwise, building, testing and controlling the robot was a lot of fun and taught us many useful things about engineering.