High precise rotary movement/measurement
High precise rotary movement/measurement
(OP)
Hello,
I have a 50mm x 25mm x 4mm glass plate. It will rotate (CW and ACW) along its middle axis, about 20 times in a second, but only in a range of (+1°-1° to +20°- 20°). Very precise measurement upto 0.5 arc seconds accuracy is required.
To move the plate, I may use a high precise motor. To achieve high degree of precession level, I may possibly use backlash free high down gearing (upto 500 - 1000). Additionally, I may use a high resolution encoder (with interpolated output).
This is just an idea at the moment. One of the practical concerns could be the mechanical play in design assembly.
I may also use a plate, comparatively bigger in size. Instead of moving the mirror angularly, I may also be able to perform my desired operation by moving it linearly back and forth (+10mm to -10mm). But this would be the second preference.
I hope for some assistance in this forum regarding the followings.
Mechanical feasibility
Suggestions regarding high precise motors/encoders/gearboxes for such an application
Any other alternative suggestion/mechanism
Regards
Thanks in advance
Sims
I have a 50mm x 25mm x 4mm glass plate. It will rotate (CW and ACW) along its middle axis, about 20 times in a second, but only in a range of (+1°-1° to +20°- 20°). Very precise measurement upto 0.5 arc seconds accuracy is required.
To move the plate, I may use a high precise motor. To achieve high degree of precession level, I may possibly use backlash free high down gearing (upto 500 - 1000). Additionally, I may use a high resolution encoder (with interpolated output).
This is just an idea at the moment. One of the practical concerns could be the mechanical play in design assembly.
I may also use a plate, comparatively bigger in size. Instead of moving the mirror angularly, I may also be able to perform my desired operation by moving it linearly back and forth (+10mm to -10mm). But this would be the second preference.
I hope for some assistance in this forum regarding the followings.
Mechanical feasibility
Suggestions regarding high precise motors/encoders/gearboxes for such an application
Any other alternative suggestion/mechanism
Regards
Thanks in advance
Sims





RE: High precise rotary movement/measurement
The weight of the plate is substantial, at least if you are going to move it 20 times per second. I doubt if any motor can do that with the required precision in the available time.
The limited movement can be positive factor since a two-wire galvanometer arrangement could be used for low friction and infinite resolution. But the weight of the glass plate is a problem.
In any case, there are no mechanisms that can produce the desired accuracy directly. You need to measure the angle and use the result in the outer position loop. Even the measurement can be very difficult because any displacement of the center of rotation ruins precision.
I have never been able to get better than a few arc-seconds. I did it with a modified (other, tighter, bearings) stepper motor that I calibrated and applied micro-stepping to. PWM made motor current resolution easy. And I didn't need to move as fast as you do.
A very interesting challange. But I am sure someone has done it. Watching answers with great interest.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: High precise rotary movement/measurement
Would seem a galvanometer is perfect for this and could be bought off-the-shelf.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: High precise rotary movement/measurement
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: High precise rotary movement/measurement
I don't know...
Some of these mirrors look like they mass way more than the described piece of glass. See the ones pictured in the PDF.
http://www.camtech.com
http:/
htt
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: High precise rotary movement/measurement
respectfully
RE: High precise rotary movement/measurement
It is a lot more difficult than you think. And that is probably why the OP asked in the first place.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: High precise rotary movement/measurement
General Scanning and Cabridge Technology are two companies that supply commercial scanners. Their specs are way worse than your requirements.
TTFN
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RE: High precise rotary movement/measurement
For +/- 40 deg, I'd look into a constantly spinning optical polygon.
Mike Halloran
Pembroke Pines, FL, USA
RE: High precise rotary movement/measurement
If you need only one then be prepared to pay $$$.
Peter Nachtwey
RE: High precise rotary movement/measurement
RE: High precise rotary movement/measurement
TTFN
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RE: High precise rotary movement/measurement
RE: High precise rotary movement/measurement
http
IRSTUFF is correct, 0.5 arc second accuracy is very difficult. But is it really 0.5 arc second resolution you need? If so, that can be done using, say, Heidenhain's flash/parallel output interpolator boards.
Forget gearboxes and think about direct drive and air bearings (New Way Air Bearings).
RE: High precise rotary movement/measurement
The 0.5 arcsec accuracy and 20 Hz is presently required for my system. If I could be able to solve some other adjacent constraints, I may be able to come down to the requirements of 1-2 arcsec and 5 Hz.
@ Blacksea, @sreid
Use of Heidenhain's solutions seems to theoretical approaching the requirements. A concern could also be to find a drive with minimum play (repeatability/accuracy). Min. I found is +/- 10 arcsec. Some assistance in this regard would be really be desirable!
Due to inertia concerns (mass of the plate 8-10 g) “Galvo meter” seems to be a hard choice. If I could ensure a “Galvo meter” for my application, solution by “waross” would be the smart one. @waross; could you please further assist which kind of light beam you mean for such a solution.
Thanks and Reagrds
sims
RE: High precise rotary movement/measurement
http://www.renishaw.com/en/6482.aspx
These tend to be very accurate especially in a vacuum. In air you need to control temperature, pressure and humidity ( or the compensate for changes). High speed, high resolution and the retro reflector is light weight.
Heidenhain has a similar product.
RE: High precise rotary movement/measurement
http://www.renishaw.com/en/6486.aspx
But sin/cos 1Vpp encoder from Heidenhain maybe cheaper solution vs laser one.
RE: High precise rotary movement/measurement