Hexapods / Stewart Platforms

Well, I just finished going through some more of the files section, and
I found an interesting little directory called HEXAPOD. Obviously
someone has given this some thought, as there are photos of real
actuator legs there.

So, I'll word my questions carefully. The hexapod (Stewart Platform)
design holds some interest for me, but while the mechanical side of it
is relatively straightforward, the algorithms for controlling the motion
of the platform, are not.

<http://f4.grp.yahoofs.com/v1/oPXfPtz9G29D8Bgj4IfSmH01Nv-1am3zEKWeWoCXoiFWAt3yRZm1byhZhEfRClDuRmSw5U-2Kk_IKerQ/Hexapod/animated_hexapod.gif>
is a direct link to an animation showing how it moves.

I was going to ask if anyone had any experience with this type of
mechanism, and whether anyone had built one. Obviously from the
pictures, it's at least crossed someone's mind, and at least a little
work has been done in this direction. Considering this, are there any
updates on the project?

Now, my real question. Is there any (easily available) software which
controls this type of mechanism? Preferably something free or low cost,
like TurboCNC... The mechanical side, while not simple, seems to be of
a relatively straightforward design. My concerns lie with the control
sequences needed.

If such software is not available, could anyone here help me understand
the algorithms involved in controlling one of these things? I could
probably program a controller for a hexapod, but I'd have to understand
the math involved...and currently, I don't understand it at all.

-- Chuck Knight