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Subject: 
Re: Just a few highlights and points...
Newsgroups: 
lugnet.org.us.laflrc, lugnet.robotics
Date: 
Wed, 28 Sep 2005 14:49:48 GMT
Viewed: 
1396 times
  
Brian, don't read this.  (he's trying to work it out for himself...)  :)

On Wed, September 28, 2005 8:24 am, Brian Davis wrote:
In lugnet.org.us.laflrc, Thomas Chesney wrote:

...one way to do it is to use the 'always turn left
(or right)' technique... recording the (x,y) position
of each turn... Getting accurate (x,y) data is a pain
though.

   Agreed. Using two rotation sensors could certainly work, but that takes two
RCX inputs, leaving me only one light sensor for line following (OK most of the
time) and detecting & describing junctions (rather more difficult with a single
light sensor). Timing the distance might work in some cases, but here it would
be tough - the time between two nodes in this maze isn't a nice, constant
function, and a long straightaway could really mess up this method. Still, it
might be a possibility (& it might help with another problem I've had, see
below)

While this is a good "brute force" method of mapping a maze, you'll be saving, and
trying to use quite a bit of information that you don't need.

Assuming you can identify an intersection, all the robot really needs to know is
where to go when it gets to an intersection.  It doesn't need to track intersections
it won't visit in the correct "solution" to the maze.

It also doesn't need to know the distance between intersections, and it doesn't need
to identify turns that are NOT intersections.

From the robot's point of view, it has three options at an intersection, go right,
straight, or left.

I think I have my program set to track 36 intersections (not sure where I got that
number from)  In reality, I suspect you'll need to remember less than 10.


   Good, although I want to apply at least one other optimization. At a
junction, the first choice of direction to explore should be either straight
(turns take time) or towards the exit (this maze starts at grid coordinate (0,0)
and finishes at (6,6) - I might end up taking advantage of that, if I (the
programmer) get time).

I don't think this is a good idea.  It could easily cost you much more time than you
save.  Of course during your "mapping" run, it really doesn't matter how long it
takes.

Steve



Message has 1 Reply:
  Re: Just a few highlights and points...
 
(...) I didn't read it. But if I had... (...) Agreed. although if we start running mazes with loops (like Alegomazer did) I think mapping, physically, the maze will likely be needed - if for no other reason than to know when you've closed a loop. (...) (19 years ago, 28-Sep-05, to lugnet.org.us.laflrc, lugnet.robotics)

Message is in Reply To:
  Re: Just a few highlights and points...
 
(...) Agreed. Using two rotation sensors could certainly work, but that takes two RCX inputs, leaving me only one light sensor for line following (OK most of the time) and detecting & describing junctions (rather more difficult with a single light (...) (19 years ago, 28-Sep-05, to lugnet.org.us.laflrc, lugnet.robotics)

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