DRO: Inductosyn-2
Posted by
Arne Chr. Jorgensen
on 2000-03-16 17:40:23 UTC
Hi,
I just add a few more words:
If " the square wave shaped ribbon" - that is the primary inductor,
(pick-ups=secondary ) is driven with a voltage U, then the secondary windings
would have:
u1= U*sin("omega" t) *sin("theta"),
u2= U*sin("omega" t) *cos("theta").
"omega" = angular frequency
"theta" = mechanical angle
( You would probably write this more correctly - but I don't have "greek"
letters )
These secondary windings is placed 90 degrees out of position to each other.
(just like "optical" sensor)
Often used frequency is between 400-1200Hz on the primary. Because the
"pick-up" windings will cover several of the primary windings, - the mechanical
layout is not critical, as you will have an average measure. It is not
sensitive to voltage, but phase. The signal you pick up, - will have a cosine
function with periods of 2p, - that is the same as one period of my "square
wave shaped winding".
( on the mentioned IBM printer - if I remember right - the" square wave shape"
was like 0.4" for one "period". But the resolution is much higher, depending
on how many bits your ADC use. It will typical measure increments in 1 micro
meter. ( should be something like 0.0004" )
So, compared to a "home-brew" linear optical system, - this is much more
promising, if you would like to get high resolutions. It would be much
simpler to make the "stator" or "square wave shaped ribbon" - then a high
resolution optical film. For long tracks, they just add more "PCB-boards" with
this "square wave shape" together. It would also be possible to use a lenght
of copper wire, and bend it into shape.
( If any have some schematics of the electronics, I would like to know. Even
close up pictures of a pcb board could in fact help. Also anyone having
anything on ordinary rotary resolvers, could help here. )
Well, I just added this because I think many would be surprised about the
resolution you may get, compared to the "coarse sq. wave ribbon".
( I have waited a long time - wondering why no one said anything about this
subject, but I am not a machine operator, - so I just thought this was common
knowledge, - as this is an old and common way they make read out devices. It
is also the same kind of stuff used on resolvers. Hmm... I know many of you
have some of those. Hmm... in some cases you may add a few modern ADC
circuits, and outperform many optical encoders ? I just wish I had some to
play with :)
//ARNE
I just add a few more words:
If " the square wave shaped ribbon" - that is the primary inductor,
(pick-ups=secondary ) is driven with a voltage U, then the secondary windings
would have:
u1= U*sin("omega" t) *sin("theta"),
u2= U*sin("omega" t) *cos("theta").
"omega" = angular frequency
"theta" = mechanical angle
( You would probably write this more correctly - but I don't have "greek"
letters )
These secondary windings is placed 90 degrees out of position to each other.
(just like "optical" sensor)
Often used frequency is between 400-1200Hz on the primary. Because the
"pick-up" windings will cover several of the primary windings, - the mechanical
layout is not critical, as you will have an average measure. It is not
sensitive to voltage, but phase. The signal you pick up, - will have a cosine
function with periods of 2p, - that is the same as one period of my "square
wave shaped winding".
( on the mentioned IBM printer - if I remember right - the" square wave shape"
was like 0.4" for one "period". But the resolution is much higher, depending
on how many bits your ADC use. It will typical measure increments in 1 micro
meter. ( should be something like 0.0004" )
So, compared to a "home-brew" linear optical system, - this is much more
promising, if you would like to get high resolutions. It would be much
simpler to make the "stator" or "square wave shaped ribbon" - then a high
resolution optical film. For long tracks, they just add more "PCB-boards" with
this "square wave shape" together. It would also be possible to use a lenght
of copper wire, and bend it into shape.
( If any have some schematics of the electronics, I would like to know. Even
close up pictures of a pcb board could in fact help. Also anyone having
anything on ordinary rotary resolvers, could help here. )
Well, I just added this because I think many would be surprised about the
resolution you may get, compared to the "coarse sq. wave ribbon".
( I have waited a long time - wondering why no one said anything about this
subject, but I am not a machine operator, - so I just thought this was common
knowledge, - as this is an old and common way they make read out devices. It
is also the same kind of stuff used on resolvers. Hmm... I know many of you
have some of those. Hmm... in some cases you may add a few modern ADC
circuits, and outperform many optical encoders ? I just wish I had some to
play with :)
//ARNE