RE: [CAD_CAM_EDM_DRO] Re: Stewart Platforms...

Frank,

I use several programs, each of which, unfortunately for overall
development time, I've written.

The first is the low-level I/O driver which operates the 6 stepper
motors. This runs as a Linux kernel driver. I looked at real-time linux,
and worried about the patent situation. I also failed on my first attempt
to patch the kernel I was using. It may have been because I'm running on a
SMP (multiprocessor) motherboard.

The low-level I/O driver also scans the pendant, which has some buttons,
LEDs, and the panic button.

To get high enough time-resolution without using real-time linux
extentions, I changed the base operating frequence from 100 HZ to 1000
HZ. The next incarnation will probably run at a higher rate.

The second is a program, "runlist", that reads a list of poses (positions
in xyzPRW space) and other commands, and sends leg-coordinate move commands
to the low-level driver. It is the workhorse of the software, and is
functionally equivalent to some of the functions of a g-code interpreter. A
descripton of the "runlist" command is found at:
http://www.foxkid.net/cgi-bin/notebookpage.pl?pdp=/home/httpd/html/&name=/cmm/platform/runlist.page&imagedir=/Processed/Carl%27s%20Projects

"runlist" uses a library of kinematics functions which are shared with
other programs. Some of these programs are:
"xyzPRW" use the keyboard or pendant to provide 6-axis "jog"
functions.
"diddle" uses the keyboard or pendant to give leg-space moves.
"one" sends a command to the low level driver from the cmd line
(rarely used).
"findtouch" uses the touch probe to map the surface to be
cut. This is particularly helpful with warped wood.

The kinematics programs are controlled by a file, "/usr/etc/joints.txt",
which gives the Cartesian coordinates of the leg attachments points, both
the fixed and and the moving end. Based on the joint locations, the
software performs the forward and reverse kinematics, as well as preventing
the platform from attempting poses which exceed the limits of the leg
attachment joints.

Another global file, "/usr/etc/tool_table.txt" includes the definitions of
the available tools. No program currently auto-selects a tool, but this is
a convenient place to put the tool definitions. The software knows about
ball-end, flat-end, V-end tools.

Another set of programs helps with creating the lists of poses processed by
"runlist".

One of these, "toolpath", converts raster files to pose lists. It takes
input of a raster in any of the standard forms, along with parameters
specifying which tool to use, how to scale the raster, and which algorithm
to use.

Others implement atomic geometric cuts, such as "ringhole", "recthole",
"spherehole", "circle", "spiral".

I'll be pleased to answer other questions, and will rely on Bill's
(listmom's) judgement for when this drifts too far off the list's charter.

-- Carl




At 09:53 PM 11/11/2002 +0100, you wrote:

>Hi Carl,
>
>What program do you use for controlling your Stewart platform?
>
>Frank de Beer
>
>
>
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Carl Mikkelsen
Oasis Semiconductor, Inc.
201 Jones Road
Waltham, MA 02451
(781) 647 8775