DRO stuff 2

Hi,

Thanks Jon, but you make me wonder a bit, so to clarify things a bit:

1. DRO - a digital read out device:

As far as I understand it, you would use this in a manual manner. To see your
position, instead of reading the dial on the cranks and keep counting cranks.

2. Linear encoder:

This seems to be what you have in mind - connect it to EMC or similear.

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Sure, both could be done. But there is a difference: You don't need a high
update on a "DRO", and interpolation or other stuff don't matter much. But
used together with a machine controller, - then you do need at least 1kHz
update. ( you would probably like much more )

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3. - a 3rd option:

Let say you used a machine controller, using encoders as a course reference,
then homing in on a very accurate position, you would do a mode shift. Turn on
some interpolation. Even if this would take some more update time, your
feedrate is low - so I see no reason why this could not work.

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Here is another idea:

I once made the logic for encoders, with 1x, 2x, 4x selection. I have not
worked it out yet, - but here you use 2 sensors, - 90 degrees apart. Well, say
you use 4 - 45 degrees apart. You should be able to increase the resolution.
Call it a "octoture" encoder :)
There may be some flaws in my "brain-computer" - but a few ideas here looked
like it should be possible.

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Ball bearing DRO:
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If you used some winding around the tube, making a transformer with the balls
as the core. ( I would like to know what size these balls have ) This should
be enough for a crude sensor. Other ideas ?

( In the back of my mind, I think I have seen some small sensors that SKF -
maker of ball bearings - used for speed/wear sensing in a ball bearings,
hmm.. )

( I have even thought of some crazy optical system - balls have been used in
holographics with lasers .. but that's me - crazy stuff :)

While I crank out "crazy" stuff - the read/write heads on a HD could be used
as sensors, and of course hall devices could be used.

In closing:
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We should have indexed this stuff a little better. Like I started, I would
subdivide between encoders for machine feedback, and DRO. In each group we
have mentioned, further subdivisions is called for.

Jon pointed out the update speed, and this could rule some form of
interpolation - but there is other ways to do this.


Question: Does anyone have something on "self-decoding V-scan encoders" ?

//ARNE