> Now it gets harder :-)
> Depends on how many trials you are allowed.
> If number of trials is staistically small and tiles are cunningly designed
> to fool an only moderately smart robot then option 1 to 3 may well be
> better (Use the Force, Annie).

No, I think I implied that the # of trials is statistically large. And presumabl
y
the right/left position of the crossable tile is random.

> eg 2 tiles, one with a clear optical path but uncrossable, the other with a
> zigzag path so no line of sight but crossable, would lead a "I can see
> across  - it must be OK"decision maker to die every time.

>
> Assuming the uncrossable tile does not give itself away and allow you to
> leave after entry - ie you must commit to one or other and then enter, then
> one could design various sensors to sense probable problems.

no reason to think it would be so designed.  I was thinking of tiles with
more likely 'real world' situations - like, for example, a tile with a number
of office chairs sitting on it, or a tile with a number of those wire mesh
trash cans, or one littered with clothes.

> IF the tile
> designer is TRYING to trap you then he will win as he (she probably in this
> case ;-)) has a brain and the robot is only programmed using a brain.

that's not the objective, and of course making an uncrossable tile is as
simple as making the tile be "nothing" - the robot physically can't cross.
I'm not seriously suggesting we do this as a contest,
I'm suggesting thinking about it might lead to understanding some piece of
robot navigation.

>
> THUNKS
>
> I reckon option 3 is liable to be pretty good :-)
>
> I may have missed what you were driving at. Maybe a bit more description
> would be useful.


> Various assumptions need also to be laid out eg
> - Can you only test before entry to tile.

no. You can do anything physically possible except change the robot's locomotion
or add a human driver. Indeed, I'd be very suprised if the robot's algorithm was
n't
something along the lines of wall following. examine patches in front of you. If
 you
think they're not safely passable, consider them walls and use a wall following
algorithm.

> - May you "save" yourself by leving an uncrossable tile if you detect it.

sure.

> - Can extra sensors be mounted?

yes.  I said that in the original post.

The physical setup seems pretty straightforward.
Here's a little robot, it needs to navigate from A to B, and in between is
known to be a path.  That's the navigation problem.
What I've done is reduce it to the problem of not getting stuck. Since there's n
o
requirement for speed getting to the goal, even an algorithm of moving randomly
into
'safe' areas will work.