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November 2014

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First Lego League in Virginia and DC <[log in to unmask]>
Subject:
From:
Fredrik Nyman <[log in to unmask]>
Date:
Tue, 25 Nov 2014 10:07:14 -0500
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Fredrik Nyman <[log in to unmask]>
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If I were smarter, I'd have thought of this at the beginning of the season:

This might make for some worthwhile experiments for your teams to do.  The
challenge: prove (or disprove) my assertions below.

For example: start the robot in the NE corner of base (i.e. manually aimed)
and have it run some simple program where the robot drives 5-6 feet in all.

Record the robot's ending position.  Repeat several times, and record the
results.

Next, start the robot in the SE corner of base (butted up against the W and
S wall; use bumpers or a jig).  Repeat the experiment.  This will give you
a good idea how much variability, if any, is added by aiming the robot.

You can similarly experiment with the light situation.  Record the
reflected light values when the color sensor is over various spots on the
field.  Open or close the shades as appropriate, then measure reflected
light again.  How do the values change?  Then run the experiment again,
this time calibrating the color sensor right before measuring.  What
changed?

On Tue, Nov 25, 2014 at 8:14 AM, Fredrik Nyman <[log in to unmask]>
wrote:

> I think that you can generalize the lesson even more, into "variability is
> built into the robot game, and the key to success is building robust
> solutions that take that into account".
>
> Consider: from game to game (on the same table), battery power level might
> change.  Models might be put in slightly different positions, and the robot
> might be in a slightly different starting position.
>
> Between tables, additional factors come into play: the illumination is
> different, the mats aren't the same distance from the walls, and so on.
>
> Then there's the variability built into the equipment: traction will vary
> from tire to tire, there's slack in the motor gearing, and so on.
>
> (Calibrated) sensors will help you build robust solutions, as will simple
> things like starting jigs and bumpers so that the robot can drive into a
> wall to square up itself.
>
> On Tue, Nov 25, 2014 at 5:44 AM, John Davison <[log in to unmask]>
> wrote:
>
>> As part of our rookie lessons learned for next season, does anyone have
>> thoughts about the pros and cons of using rechargeable vs. regular
>> batteries?  Early on, we found that our robot performance varied quite a
>> bit based on how fresh the batteries were, and we seemed to be burning
>> through lots of regular batteries.  So we switched to rechargeable
>> batteries soon before the competition, but then had to tweak our
>> programming because the output of rechargeable batteries is different from
>> regular batteries!  If we stick with rechargeable batteries for our next
>> robot design, are there any potential problems or downside that others have
>> experienced?
>>
>> John Davison
>>
>> Sent from my iPhone
>>
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