[Adam Y.]

Because various things can affect how far your robot travels in the period of the counter. A fully charged battery will cause a robot to travel significantly faster and thus farther in the same amount of time compared to a somewhat depleted battery. If someone sets bins in front of your robot it will probably slow you down and screw up your timing as well. This is a fundamental problem with dead reckoning.

Actually there is a way to implement dead reckoning that gets rid of the above problems. Use an encoder disk. These things are circular disks with stripes of black and white running down them. Mount this disk somewhere onto the drive train. Using this and a sensor (usually infrared or banner sensors would even work) you can now calculate how far your robot has gone by reading the pulses of the sensor. A little gear ratio math and you can now figure out how far the robot is going in each pulse. Although using the timing of the controller is almost the same idea this will not get the robot off track due to differnces in speed from a fresh battery. Of course nothing can really correct a big change in the course of the robot. I am just surprised that far fewer teams went the more complicated way to do it than the simpler way.

Break the walls? Dang... they must be really cheap then! Our team made a practice ramp and used 1/4 in. plexiglass or lexion or whatever that cheap plastic stuff they have, and I've run into it many times at full speed when testing our autonomous programs.. hasn't broken yet

It must be lexan because Plexiglas has been used at hockey games to protect the people but the barriers have been known to shatter. I think? Plus lexan is used in bullet proof windows so that does not shatter easily.