[Tom Ore]

We also were concerned about this problem - we didn't want to run the motors against the hard stop at the top and bottom of the elevator travel.

We use a pot to control travel of the elevator. Since it's possible for the pot to come loose and change value we put a second pot on the other side and compare the two to make sure they agree. We also added a light sensor that checks the position of the elevator in the middle of its travel as another check. (We've never made a robot with an elevator before so we were a bit cautious.)

If the elevator comes down on top of a tote it's possible for the elevator to tip the robot over. (This happened at our week 0 event when the HP tried to add a 7th tote and the co-driver tried to block it by dropping the elevator.) To stop the robot from tipping over, the software/electrical team added a sensor that detects when the front of the robot lifts off the ground. (I'm not sure what sensor they added.)