6.270 Autonomous Robotic

Competition

IAP 2003

Robot Sucker

Overview From the very beginning we were creating a robot that would consist of the four major parts: feeding mechanism to grab the balls inside, lifting mechanism to lift them at least two inches high above the playing ground, storage chamber and releasing mechanism to deposit the balls to the lava island. Step by step we designed and redesigned all the mentioned parts of until we finally came up with: rotating wheels at an axle in front, at the ball's height along with plates on both sides to grab the balls in the robot once stuck onto them; freely rotating ramp to lift the ball once inside, plate with a clamp above it to store and deposit the ball to either side of the back of the robot. The back of the robot was triangle - shaped facilitating the deposition of the ball to left or right side so that lava island could have been approached from both.

Navigation At first we tried to ensure precise navigation by means of line following. The project finished at the stage of mounting the color sensors when we decided that wall following would be faster and more robust. Our idea was to implement wall following without bumper sensors but rather hug the wall sliding along its side using small wheels attached onto both sides of the robot and constantly driving towards the wall at an angle of about 6 degrees (big enough to stay close to the wall, small enough not to get stuck on it). In the end however, the wheels made our robot wider than one foot so we had to detach them. Our robot was thus, hard coded in this respect and did not use any sensors to move straight. For turns, we tried hard coding at first but this method generated different results in each run, so we used shaft encoders on each wheel. After a couple of tests our robot reliably turned at around 90 degrees to each side.

Power We used all six allowed motors and all of them at the maximum speed :) We used two to power each of wheel and two to power the sucking mechanism which was composed of a rotating wheels placed on an axle coming out of the gearbox and extended by means of chains. We used 27:1 gear ratio on the wheels and 15:1 reduction on the sucking arm. The robot was therefore very fast (escaped us very often:)) and the sucker was powerful enough to suck the ball up the robot at the distance of about 6 cm where it was later transported by the freely rotating ramp.

Sensors A few. Phew! (The winning robot this year had only four of them; we were close to this number; we were close to winning. ;P)

Construction The skeleton of the construction was the combination of the two gearboxes on the sides with the plate at the back; everything supported by three wheels arranged on vertices of a triangle (one big stuffed wheel on each side plus another small wheel attached to a turntable powered by a servo at the back). All parts were strongly braced providing a sturdy structure supported by the axle under the ramp as well as the sucking mechanism topped with a roof where the handyboard resided. The batteries were spread on the sides and at the back to maintain balance. A pearl of mechanical design!