In my opinion there would be allot of problems with cross modulation,
filters tend to be bulky and hard to get accurate filtering with expense.

At the end of the day what is wrong with a single wire protocol as discussed
in another thread were each device has individual address and all devises
respond to a broadcast address - all return to neutral.

*************************************************
Roy Hopkins   :-)

Tauranga
New Zealand
*************************************************

----- Original Message -----
From: "Robert B." <piclist@NERDULATOR.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, June 25, 2004 6:48 AM
Subject: [EE:] Analog signaling


> I recently had an idea (probably ages old) for the transmission of data on
a
> continual basis using analog voltages, and would like to get some
criticisms
> on it before I get too deep into trying to make it work.  The basic idea
is
> to use frequency-dependent filters to determine the amplitude of some
analog
> signal at a given frequency.  Perhaps the best way to explain the idea is
> with an example:
>
> Example:  Take a robot with 40 separate actuator "muscles".  For now just
> consider the actuation control and disregard the feedback mechanisms. To
> establish real-time control of 40 actuators on a digital link would not be
> impossible, but would perhaps restrict expandability, etc.  So we assign
> each "muscle" a control frequency based around a signal amplitude.  Muscle
1
> gets 20khz, 10vpp centered on 0v.  To move it from neutral, the amplitude
of
> the 20khz signal drops to say 5vpp or rises to 15vpp.  The actuators are
> tuned to listen on a specific frequency, which is then smoothed to a
> relatively DC voltage.  All 40 actuators are installed as said, at perhaps
> 22khz, 24khz, ... and so on (no calcs yet, but assume there is enough
> bandwidth), each with an independent filter to see what component of its
> tuned control frequency is present.  So now to control all 40 actuators at
> once it would (only?) be necessary to sum 40 separate control signals into
> one analog signal, and inject that to the backbone where each actuator
will
> single out its respective command.
>
> The apparent advantage of this method (to me) would be the increased
amount
> of data transfer on a single wire, with the primary disadvantage being
> somewhat imprecise control all around.
>
> The way I would envision it working is having a powerful processor to
> generate the analog stream, and multiple PICS spread around the network to
> read the filtered frequency and do the actuator control, then perhaps
> eventually "capturing" analog streams to memory for replaying, for
example,
> a walking routine for a humanoid robot.
>
> Is there any major problem I'm overlooking in a network like this?  It
seems
> pretty sound to me, but I'd really like to get some expert opinions, or
> maybe advice from someone experienced with a similar network.  If it looks
> feasible I very well may be turning it into an "open hardware" project for
> robotic control, but I'd hate to take it that far and have a miserable
> failure!
>
> --
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> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>


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