Alt-BEAM Archive

Message #04852



To: beam@sgiblab.sgi.com
From: Sean Rigter rigter@cafe.net
Date: Thu, 24 Jun 1999 19:04:51 -0700
Subject: [alt-beam] Re: Ah! Blessed Skepticism! (was: Feedback explained?)


Hello Bruce,

Fair comments! Am I SURE I really want to get into this? The "voltage
drop" feedback question can be readily answered with a simple
experimental setup on almost any walker with "end of leg travel" stops
or the commonly used leg centering springs. Just do four comparisons to
measure the effect of the four combinations of "power supply impedance"
and "end of travel motor loading" on process duration. Now there must be
hundreds of suitable candidates in tens of RJPs out there. Any
volunteers? (grin)

regards

wilf

Bruce Robinson wrote:
>
> Wilf Rigter wrote:
>
> > To a standard suspended Bicore add a BG micro motor directly to the
> > Bicore outputs. Observe the rotation and Bicore pulsewidth is about 90
> > degree each way and 1 second pulsewidth duration. Now load the output
> > shaft with some finger pressure (not a complete stall) ...
> >
> > If the Bicore output is buffered before connecting to the motor, the
> > output pulse duration is actually slightly longer when the motor is
> > loaded even if a small resistor is introduced in series with the
> > powersupply to reduce supply voltage under load (so much for powersupply
> > feedback)...
>
> You know, Wilf, after thinking about this a bit, I infer a small
> experimental flaw. Ben's comments set me on the right track, and I did
> some theoretical calculations for various stalling conditions.
>
> Theory suggests that a generally restrained robot (e.g. it's caught in a
> pool of molasses) will not experience a shortened Nv cycle due to
> voltage drawdown.
>
> The most pronounced effect OUGHT to occur when the leg gets seriously
> stuck half way through it's movement cycle. Experimentally, this would
> involve applying a major load half way through the time delay.
>
> Are you SURE you really want to get into this ?
>
> Regards,
> Bruce

--
Hey, come visit my homepage at
http://www.geocities.com/Area51/Nebula/1710/
Southpark, Mechwarrior2, V&V, Al-Qadim, and Milla Jovovich!

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