Robot ``Easter Egg Hunt'' discussion digest

                                                                                                               
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Date: 18 May 1999
DJ: Darrell Johnson
BH: Ben Hitchcock
KH: Ken Huntington
SB: Steven Bolt
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Obstacle min/max. diameter


If no objections are received before June 1, this proposal will be
copied to the Playground definition:

SB> Ten obstacles: cylindrical, 2cm high, matt finish, kept in
SB> position with a central pin. The distance between them and
SB> between any obstacle and the border is 10cm or more. They may be
SB> anywhere on the Playground, except in the gathering area.
SB> Diameter between 2cm and 20cm.

Modulated IR Beacon


If no objections are received before June 1, this proposal will be
copied to the Playground definition:

SB> Modulated IR Beacon: Optional. Participants who wish to use an IR
SB> beacon must provide their own. The average current consumption
SB> must not exceed 10mA at 9V, and the emitter(s) must be at a
SB> height of no more than 5cm above the Playground floor, at the
SB> center of the gathering arc (as shown). If the beacon is to stand
SB> in the gathering area (instead of outside the Playground), it
SB> must occupy less than 25cm2. An unstabilized 9V source will be
SB> available.

Other topics being discussed:

Height of the Playground border


SB> The present obstacle definition allows for colors other than white;
SB> I was thinking of a little color to make photos more attractive.
 
KH> I would suggest that if colour is used, it be restricted 
KH> to the tops of the obstacles but even then one might 
KH> attempt to use that to an advantage but so what.

SB> I believe that Darrell is the only one seriously working on color
SB> discrimination. Let's wait until a real need develops, before
SB> limiting the obstacle colors?

Black walls for the Egg Hunt gathering corner


KH> There is one further argument. One may choose to
KH> use touching the black border to confirm that the
KH> hunter is in the gathering area to make use of an
KH> existing optical sensor rather than black of the
KH> gathering area floor. Of course, it makes little
KH> difference as the only obstruction which may be found
KH> in the gathering area must be part of the border
KH> or be attached to it (Easter Eggs an exception).

SB> That existing sensor would have to be low enough to see the wall,
SB> which means that elsewhere on the Playground, it may not be able to
SB> see the beacon - if that is the sensor you were thinking of.
SB> Imho a down looking sensor will reliably detect the difference
SB> between black and white surfaces. A forward looking sensor won't
SB> have its target at a fixed distance, and may be distracted by
SB> environmental factors. Touching a wall won't always save you, as
SB> the robot may touch several obstacles while transporting an Egg to
SB> the gathering corner. And it doesn't know the distance between
SB> itself and the beacon.
 
KH> What if one is using the sensor for collision avoidance 
KH> or egg detection and what if the beacon is not being 
KH> used at all? Then nothing above 1cm +/- 1cm means 
KH> anything. My thinking is out of step with yours but 
KH> this is a "Contest" :) Besides, my paper design is not 
KH> as far along as yours, yet :)

SB> Plenty of contest here. Competition is great for lifting the game!
SB> But I hope to read more about your Egg Hunting `eyes' :)

SB> My own new gimmick is a hopefully efficient tactile sensor, based
SB> on measuring the current consumption of the motors. If only one
SB> motor is active at any time, identifying the cause of a high
SB> current is easy, and can be any one of six: obstacle in front of or
SB> behind the left or right wheel, or difficulty further opening or
SB> closing the jaws. If it works, I get a lot of mileage out of a
SB> single sensor, which may consist of 3 resistors and a little
SB> software. 

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