Alt-BEAM Archive

Message #00052



To: beam@corp.sgi.com
From: Noam Rudnick rudnick1@cwix.com
Date: Sun, 31 Jan 1999 10:51:11 -0500
Subject: [alt-beam] Adaptability in Two Motor Walkers


So I built my first walker using those sweet bgmicro lens motors, and It
works pretty well, but due to some variations in the exact values of my
components (they all say they are the same value, just slight errors in
manufacturing probably), each legs goes one way slightly more than the
other way. This behavior is tolerable for short periods of time, but
eventually it causes the robot to flip over (quuite interesting to watch
actually =)) Anyway, this problem could probably be easily fixed by
adjusting the RC time constants with a potentiometer, but if I where to do
this, then the robot would have trouble when it encountered terrain which
required a slightly different walking gait. So this is where I thought
feedback came in, until a few weeks ago when I was told that the 245 chip's
inputs are isolated from its outputs. Then I was told that by adding 47K
resistors across the inputs and outputs of the 245 chip, one could achieve
feedback. So I tried this, only to find virtually the exact same behavior
in my walker as before. I really would like to give my robot the ability
to adapt to terrain, and I was wondering if any of you could help me out.
Currently, I am using three stacked 245 chips because I needed all of them
with my old motors, and I never bothered to take them off. Would this make
any difference? Should I choose resistances lower than 47K because of
this? I would really appreciate any advice.

Thanks a Lot,
Noam

P.S. I decoupled all of my chips from the power supply as well, but I
really can't imagine that this would make much of a difference...would it?

thanks again


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