Alt-BEAM Archive
Message #06977
To: beam@sgiblab.sgi.com
From: Sean Rigter rigter@cafe.net
Date: Thu, 21 Oct 1999 18:33:52 -0700
Subject: [alt-beam] Re: bicore
Hiya Robert,
That is caused by some imbalance in the bicore pulsewidth or friction in
each direction. There are ways to tweak (influence) the bicore waveform
symmetry to minimize the imbalance but even small offsets would accumulate
and slowly index the output shaft.
The common solution to deal with this problem in 2 motor/4 legged walkers is
to restrain rotation beyond certain limits. Since it is normal to mount
the front motor with the output shaft at such angle that the legs rise up as
well as move forward, the effect of gravity will help center the legs. For
the rear motor, which is usually mounted with the shaft vertical, it is
necesary to add a spring from each leg to the body to center the legs.
These are examples of mechanical restraints.
There are also several simple circuits which constrain rotation beyond the
limits: for example using the pot of a modified hobby servo to center the
rotation.
enjoy
wilf
Robert Stein wrote:
> Hello all. I hava a quick question. I just breadboarded a bicore. I
> was watching the motor go and I noticed something peculiar. I was
> watching the gear that eventually will be attached to the legs, and
> noticed that the gear was indexing around as well as the oscellation
> that it is suppose to do. I am assuming it is because in the difference
> in the two .22 uf caps. Am I wrong, or is there something else going on
> that I havn't thought about? Thanks for any input!
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