Alt-BEAM Archive
Message #05398
To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@bc.sympatico.ca
Date: Fri, 23 Jul 1999 23:29:56 -0700
Subject: [alt-beam] Re: walker
matthew landry wrote:
>
> ... the thing that drives me crazy is that the servos will turn more in
> one direction than the other, how could this possible work for a walker
> if it's legs would turn all the way around over a period of 10 steps?
Noise is probably not the main problem, Matthew. The electronics have
pretty loose tolerances -- caps = +/- 10%, resistors = +/- 5%, that
alone can give you a 30% time difference between the two motor
directions (if you're unlucky). Also, gearmotors/servos often have more
friction in one direction than the other.
The quick way to deal with this is to change the resistance on one of
the Nv's feeding your motor. This will change the time constant and
balance the motion. You DID use variable resistors didn't you???
Even when you get things as perfectly balanced as you can, there will
inevitably be some variation in the amount the motor turns. For example,
friction losses can change as the motor/gearbox warms up.
So after adjusting the electronics as best you can, you may have to rely
on some mechanical means to keep the legs centred. Springs are often
used -- the further the motor moves off centre, the greater the force
trying to return it to centre. Better yet, if your motor is tilted,
gravity will tend to equalize small differences.
Regards,
Bruce
5399 Sat, 24 Jul 1999 22:36:21 +1000 Photopopper Woes Pete McCarthy
> Hello Again BEAM Group,
> I need help. When I was soldering my photovore, the transistors just
broke
> apart from each other. Does anyone know a strong glue that would survive
> soldering??
>
>
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