Re: Hexapod question

Hello everyone,
Can someone answer this stupid question for me????
What would be the need for a hexapod machine anyway?
I think it is cool & would probably build one myself if I had the
time, but can't seem to figure out a use for one??? haha!!
Any Ideas?
Thanks, Tim Bostic

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Ray Henry <rehenry@u...>
wrote:

>
> > From: Jon Elson <elson@p...>
> > Subject: Re: Hexapod question
> >
> > Simon M. Arthur wrote:
> > >I've started building a hexapod on the cheap. Some photos:
> > >http://www.tinyplanet.com/images/hexapod-portrait-reduced.jpg
> > >http://www.tinyplanet.com/images/dscf0011-reduced.jpg
> > >
> > >I noticed that the platform can be rotated and tilted more or

less

> > >freely, even with power going to the steppers. Translational

movement

> > > is a lot harder. This makes me think that I misunderstood

completely

> > > how a hexapod is supposed to work. I have a universal joint on

the

> > > frame so that the motor can tilt, and another on the platform.
> > >
> > >Can this setup be made to work? Why doesn't my hexapod lock the
> > > platform in place?
> > >
> >
> > The only way a hexapod (Stewart platform) maintains alignment of

the

> > platform
> > is by controlling the lengths of all 6 struts in a coordinated

way.

> > EMC can drive a hexapod, but it doesn't really allow tilting of

the

> > platform. But, you can translate the platform in 3 cartesian
> > coordinates rather nicely.
> >
>
> Hi Jon, Simon
>
> As of a while ago, the EMC motion planner can tilt the hexapod's

platform.

> Till Franitza in Stuttgart has been doing this with his desktop

models.

> You can see both stepper and servo version photos and a movie at
>
> http://www.isw.uni-stuttgart.de/personen/t_franit/modell/index.html
>
> There is some pretty novel work on platform geometry with Model 2

where

> three of the the struts interact with the three other struts rather

than

> with the platform itself. This allows for a much larger angle of

tilt

> before the system approaches a singularity.
>
> If your German conprehension is as poor as mine, there is a Queen's
> English version that can be reached by clicking on the Brit flag.
>
> Ray