6.270 2001
Masters of the Universe
Team 43: LA CUCARACHA DE LA MANCHA
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INDEX
the team
the competition
the strategy
the robot
feedback and control
the code
the outcome
the team
Iahn Cajigas (from Puerto Rico, a junior in course 6)
Carlos Gomez (a junior in courses 6 AND 18, from Mexico DF)
Carla Pienknagura (a junior in course 2 from Quito, Ecuador)
the competition
6.270 is a yearly robotics competition that occurs here at MIT
right at the end of IAP. The contest itself changes every
year. The goal in this year's contest is to end up with more balls than your opponent at the end
of a 60 second round. The contest's table has 3 main regions "our" zone, the "other's" zone and a neutral zone (kind of like in hockey.. yeah hockey! go to the
womens ice hockey varsity team homepage ).. anyways.. each team aims to end up with more balls in their zone than its opponent.
For more information about the class, go to the 6.270 homepage.
The strategy we chose was to:
attack the center ball
steal all the balls on the opponents side
and defend our balls from being stolen at the very end of the round.
sure.. sounds easy.. but the tough parts are about to begin:
1- Build a robot and all mechanisms out of LEGO (except actuators) that will do all this
2- Make the robot do it all by itself
The functional requirements (aka the robot sould be):
1- Able to score many points (versatile)
2- Robust
3- Maneuverable
4- Easy to control
5- Complies with contest rules
6- Stable
7- Fast
8- Reliable ( behaves in a predictable manner every time)
in order to achieve all these requirements, the most important design parameters chosen were:
1-
fast, simple to grab first ball from center
repetitive, reliable mechanism to sent opponents ball to our side
2-
Use a lot of lego braces
make design modular so that it is easier to fix and assemble
drop test components to make sure they are robust
3-
rear wheel drive, each wheel with its own motors
two free wheels
no "shopping cart" wheels.. they stick when going into/coming out of a turn
avoid pieces that stick out of the robot and may get caught in corners, etc
4-
steering by difference between motor speeds on diven wheels
no complex mechanisms that need precise measurements
5- (no need to explain here...)
6-
4 wheele
wide wheel base
low center of mass that falls inside the 4 wheels
7-
gear motors down only as much as needed
make robot as light as possible
make simple, VERY robust gear train
ensure powered wheels have enough traction
8-
testing and fixing
testing and fixing
testing and fixing...
feedback and control
Once the robot was built, we needed to give it its own behavior. In order to do that, we must allow the robot to sense its environment and respond to it. For this, we had a large selection of digital and analog sensors, and infinite solutions to the many parts of the robot we needed to control. Because sensors themselves have dynamics, and a lot of them are not vewry reliable, we chose to depend on them as little as possible.
The sensors selected (in order of impotance) were:
2 shaft encoders: measures the angular displacement of each rear wheel; useful in making the robot travel specific distances and turn certain angles
switches: used to determine wether the robot hits a wall, ball or other robot
light sensors: only useful for orienting the robot.
the code
Now we have the robot, we have the sensors and now we need to program..
click to see the
code
The robot has qualified with a double win; that is, of course, after a double loss and disqualification (the other robot jammed, we forgot to turn on our batteries)
Thurs, Feb 1st
Second round was a sucess! robot behaved as always and we go on to the finals at night
later that day...
Robot jammed.. we dont understand what happened! This never happened befre in lab! La cucaracha de la mancha was eliminated!