Re: [cad-cam] [CAD_CAM_EDM_DRO] Re: Hexapod question

On Wed, 10 Dec 2003 16:27:43 -0000, you wrote:

>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?

Think of how many different ways you can move the tool, up, down, in
at any particular angle, left, right, etc.

Now imagine what you'd have to build to get this to work with a
conventional setup. I'd think 4 axis, if not 5 or more....


The advantage here is that all the axis setups are identical.

Harvey

>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
>
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