I have a client who wants to do some experiments involving deliberate anten=
na
motion in a GPS-based system. He's done some simulations and likes what he
sees, so now it's my job to set up an actual prototype so we can see how we=
ll
it works in practice.

We have a small box of electronics that includes the GPS antenna and receiv=
er
that masses a total of about 0.5 kg. We want to move this box along a
horizontal linear track that's about 300 mm long, with a sinewave motion th=
at
has a period on the order of 1.0 seconds. This means that we need to be abl=
e
to generate a peak velocity of about 0.95 m/s and a peak acceleration of
about 6.0 m/s/s (and a force of about 3 Newtons).

We also need to know with fairly good timing precision (on the order of 0.5
to 1.0 ms and 0.5 to 1.0 mm) where the box is in its motion cycle. In case =
it
matters, the motion will likely not be continuous -- instead, the box will =
sit
most of the time at one end of the track, and on command, will make one tri=
p
to the far end and back.

I've never put together a motion control system before, but based on some
preliminary Googling, I would guess that given these speeds and loads, that
a belt-driven stage powered by a stepper motor would be the type of thing I
should be looking for, along with a high-level motion controller that can b=
e
programmed with the sinewave profile.

Secondary considerations are that the unit should be relatively compact --
our box of electronics is about 50 x 50 x 125 mm and we don't want somethin=
g
that completely dwarfs this. We don't want to spend more than about $1K to =
$2K
on this, but we want to buy as much of it off-the-shelf as possible. This i=
s
just a one-off for now, but if it works out, we'll want a cost-optimized
solution for a production design. The control interface would preferably be
RS-232 (with a separate hardware sync signal?), but we can adapt as needed.

Does anyone have any recommendations for vendors for this sort of thing, or
any other pertinent advice? Thanks in advance.

-- Dave Tweed
--=20
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