I propose, as a thought experiment, a robot contest.

  A series of typical small mobile robots are constructed
to a standard design - perhaps wheeled "turtles".

  One of these robots is equipped with a remote control unit.
The others are distributed to the contestants. The contestants
equip their robots with an autonomous control system and a set of
sensors. Contestants are forbidden to modify the mobility mechanism
(no fair making the robot fly, for example).

  A bare room is constructed with a solid floor and walls, except
for a "ditch", say 4' wide and 4' deep, which bisects the room
and which is not navigable by the robots.
Robots start on one side of the ditch, and navigate towards a
well_marked goal on the other.
The ditch is spanned by two replacable tiles, creating a binary
choice - to reach the goal by crossing tile A, or by crossing tile B.
Each tile covers half the ditch's length, so there is no question of missing
the tile entirely.

An assortment of these tiles, of varying construction, are available.

  A tile is placed across the ditch, the remote control robot is then placed in
the room and
driven to the goal by a human driver. Those tiles which the robot
crosses are called "crossable" and the others "uncrossable".

The two tiles are selected at random from an assortment, always one from
the crossable tiles and one from the uncrossable.

Each robot is repeatedly released into the room to cross the ditch, with
different sets of tiles.  The one which successfully reaches the goal the
largest percentage of times wins.

Now, my question is, how shall we design a robot to win this contest?
We have no prior knowledge of the nature of the tiles.
One might be bisected by a wall, another simply an open frame that
will drop the robot into the ditch, another might have a hole only
in one portion.

It seems that many robot navigation problems (and I freely admit my
robot building experience is limited) revolve around winning my little
contest.

And clearly there are some problems for which there is no solution.
Suppose you are designated to drive the remote control robot, and you
are confronted with two tiles which appear identical, both "boxes" that
form a barrier across their whole width, but with an entry and exit door.
What isn't known is that the floor inside one box is solid, the other
a trapdoor.

So, I invite you all, how does one construct such a robot?

--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html