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Subject: 
Re: Two New Contests at BrickBots.Com
Newsgroups: 
lugnet.robotics
Date: 
Mon, 26 Feb 2001 22:21:06 GMT
Viewed: 
720 times
  
In lugnet.robotics, Ralph Hempel writes:
Am I completely thick or is the problem simpler than I'm imagining? Way
back when at the University of Waterloo, we designed a 2D
inverted pendulum
balancer on a plotter bed. The pendulum rotated a sensor, and we had to
move the bed to keep it stable. You'd get bonus points for moving the bed
in 2 dimensions....

Nope your not thick, but the RCX is! It seems to be simple problem, but I
suspect the limitations of the RCX / LEGO's will make it difficutlt.


I just don't understand the statement "Build a robot that stabilizes the
inverted pendulum by rotating it" or the picture (which should be enclosed
in a <pre> tag to display properly.

OK, now that I've figured out what the pendulum base looks like, I can
see the advantage of the rotating base, namely that we eliminate the
need for detecting the end of the range of motion!


Wow, I just now finally understand!  The picture B. Shahian linked to
finally make it clear for me.  I have included the URL for the picture in
the official rules, and I hope nobody sues me for it!

Yep, it should have been <PRE>'d but I dont write static pages (Well, If I
can help it!).  All the BrickBots content comes out of a database as plain
text and is converted to HTML (Replacing CR/LF with <BR> etc).  There was no
easy way to pre the text <PRE> would actually come out &lt;PRE&gt; , but
this should all be cleared up with this picture.  BTW: This also answers the
question "Why not inline the picture.." :-)


Thanks to all who helped in my quest for understanding. Now I have to
figure out if I can build this with touch sensors or if I should use
a rotation sensor...


My big uncertainty with this is how to measure the movement of the pendulum.
If I attach a rotation sensor to the shaft that allows the pendulm to swing,
then I am going to be slowing the swings of the pendulum with the friction
from the rotation sensor (kinda seems like cheating).  The more I gear up
the signal (less motion of pendulum=more rotations) the more I will be
amplifying the friction of the sensor.  If I put enough gears, the pendulum
will just sit there :-O.  I suppose I can add more weight to the end of the
pendulum to conteract this, or pehaps there is not enough friction in the
sensor to really make a difference.

I look forward to seeing everyones entry, but lets not forget about those tops!

Rich

rich at brickbots dot com



Message is in Reply To:
  RE: Two New Contests at BrickBots.Com
 
(...) OK, now that I've figured out what the pendulum base looks like, I can see the advantage of the rotating base, namely that we eliminate the need for detecting the end of the range of motion! Thanks to all who helped in my quest for (...) (24 years ago, 26-Feb-01, to lugnet.robotics)

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