At Penn State Abington’s annual robot contest, we observed the designs and features of the competition.  We kept an eye on   to note what works and what doesn’t.

Tread robots

The majority of the robots in the competition were slight variations on a fantastically simple tread-based design.  Two pairs of wheels joined by tank-style treads were attached to a simple solid body approximately the same size as the handy board.  Instead of using the wide, short treads provided in the Mindstorms kit, most teams opted for chain link treads which are more nubile, yet still provide adequate traction on the maze's wooden floor.  The chain links fit nicely in the teeth of Lego gears - 48 tooth size seemed to be the popular choice.  The robots require two motors for navigation, one for each wheel set.  All the tread robots I saw ran off hard-coded navigation directions.  For this reason, many teams worked in single-room mode, but a few successfully navigated the entire maze.

XY robots

A handful of the competition's participants experimented with xy robot designs, wherein the robot's motion is limited to motion in two directions.  This usually involves two sets of wheels, each aligned to move forwards and backwards in one direction.  The simplest and most successful xy robots were built atop a modified remote control xy car.  I'm told that this car may be purchased at Radio Shack, though it's not in the curent online catalog.  The teams I spoke with said that a fair amout of re-wiring was needed to adapt the base to be compatible with the handyboard, and that the base drained the HB's batteries quite quickly.  (If you would like advice on building this robot, you may wish to contact the kind folks at Penn State Abington).   That said, these robots, all hard-coded, navigated the maze extremely quickly and fairly accurately.  If the robot was not perfectly positioned to be absolutely parallel to the wall, it had a tendency to run into walls.  Since the robot was so limited in its direction of motion, it could not free itself.  Also, the sheer size of the base made it difficult for the robot to get close enough to extinguish the candle.  In one case, the robot edged the room and detected the candle in the far corner.  However, the robot was not entirely clear of the side wall; when it tried to advance towards the candle, it entangled itself with the maze wall.  Unable to advance or retreat, it wore down its batteries and motors.  None of the robots successfully extinguished the candle, but, despite their weaknesses, these were some of the neatest and most creative robots in the competition.
For information on our naive xy robot, click here.

Two wheeled robots

Two parallel-mounted wheels at the east and west compass points, and some sort of skid pad or caster at the north and south compass points.  In other words, looking from above, something like this:

(picture)