Re: Dropping marker signals?

[Joyce Poon <poonj@ecf.utoronto.ca>]

I hope everyone has had a fun Christmas holiday.  Yummy turkeys and good
presents. 

To tell you the truth, I haven't given map construction too much thought. 
But I will now... 

Here are my 2 cents on Tim's ideas: 

Dropping extra beacons in strategic areas is a novel idea (it's something
that I believe the milllirobots have to do).  However, I am not sure how
difficult it will be to build transmitters and to build some sort of
dropping mechanism. 

Secondly, I wonder whether this sort of transmitter will actually make a
significant difference.  If we have to build sensors with a good enough
range to pick up our rebroadcast signals, these sensors may be good enough
to pick up the enemy robot itself (unless we have a lot of rebroadcast
transmitters).  These extra transmitters will only be super-effective if
we can place them just at the limit of our sensor range (maybe in a grid
type formation).  But how can we do that?  I don't want the robot to waste
time trying to position all these extra sensors only be tagged during this
process.  Moreover, since we move around a lot in the playing field, we
might have to drop several (3-5? at least) sensors to make full use of
them.  Will we actually have the luxury of time to do so? 

However, in theory, even dropping 1 beacon will reduce the desired sensor
range in half (if the beacon is at the right place...).  Hmm... since the
TA (or Malone) picks the starting position for our robots, how can we
intelligently find out where to drop this beacon? 

What type of sensor will be on this extra transmitter?  If we are doing a
really simple type of transmission (ie a "yes, enemy is here" and a "no,
enemy is not here" message), it just has to be the same as the ones on the
robot.  But if we do fancy stuff, we can maybe equip it with an IR sensor
to detect obstacles <ie this extra beacon will gather info about the
surroundings>.  However, this may actually not be so helpful, since the
robot will already have traversed that area... 

What type of transmitter will we need?  Maybe a radio signal?  The beacon
can emit a radio signal when it sees something.  IR may not work, since
our robot may not be able to distinguish IR from the beacon on the enemy
and IR of the transmitter.

Can the beacon be an interference-generator?  Sure.  But, for some strange
reason, I think a rotating mirror will confuse us as much as the enemy... 

Other silly ideas for interference: How monochromatic is IR light?  If we
can somehow diffract the light emitting from us, we coud mask ourselves
(stealth!).  Or we could drop a diffraction grating and stand behind it... 
then there would suddenly be a bunch of IR signals -- that should confuse
the enemy.  Physics at work. :)

Speaking of things rotating... maybe we can encode our beacon signal if we
place a sheet of etched rotating glass/plexiglass in front of the emitter. 
But this definitely takes up more energy than just figuring a way of
turning the light on and off... 

Can we use the beacon to calculate our speed?  Hm... probably... but it
won't be easy (& probably not the best way to go about the speed feedback
problem).  V=D/T. If our robot runs on a clock (which I think it will),
then we know the time.  To find distance, I guess we can keep track of the
relative distance to the beacon (but that will require some sort of analog
process and the beacon will always have to be in the robot's sensor
range).  Hm... not so efficient...  I will look into the Hall effect
sensors some more. I think that's what they use in cars. 

Here's my feedback for now.  I have to think more about map
construction... Can't a simple map be built just by assuming that our
starting position is the origin and noting stuff like, "there is nothing
to the right" "there is something to the left" etc.?  I will think about
this extra-transmitter idea some more.  I think the most effective
approach is just to maximize the sensor range on our robot.  Dropping
extra sets of "eyes" around the playing field will definitely complicate
the design...

Oh yes, we should definitely check with Malone on dropped objects. 

New Year is just around the corner.  Enjoy the last days of 1999. 

Joyce :)