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1
THE GONIOMETERS
Yury Gavrikov25/03/2009
2
Looking back
1 year ago… I met with two very nice g…oniometers
3
Because we decided to adapt their for a new experiment
The idea of mechanicsLinear movement
Gear boxBelt drive + “virtual”
screw
Engine DC-servo motor
Carriage slides on the 2 guides
4
Linear motion
(full range = 90mm)(full range = 90mm)
Inside of beam
Outside of beam
5
The idea of mechanics Angular
movement
1mm~
63m
m
AxisAxis
PusherPusher
Angle Stepper motor
&Belt driveMicroscrew
6
ModernizationUnificated solution for angular & linear
motion:
• Stepper motor for driving
• LVDT for position measurement
• Common Control system for all devices
It was needed the mashining of original parts
7
Mechanical revision
After modernization during last month before installation :
- 4 revisions and full disassembling- A lot of motion tests and measurements- Fixing of sources of the problems
8
9
Measurement & Calibration
Angle measurement Digital Autocollimator specially
designed for the experiment
Range: ~ 8000 mrad (horizontal)~ 6500 mrad (vertical)
Resolution: < 0.5mrad10
Angle measurement
The general Idea of angle measurement
Mirror
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Angle calibration The Idea of crystal angle calibration
Reference mirror
Crystal
12
Angle calibration Angle vs. LVDT position
-50000 0 50000
-7500
-5000
-2500
0
2500
5000
7500
An
gle
, u
rad
LVDT, uV
Goniometer 2Goniometer 1
-50000 0 50000
-7500
-5000
-2500
0
2500
5000
7500
Ang
le, u
rad
LVDT, uV
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Nonlinearity of goniometers
Periodical structure corresponds to the motor revolutionNonlinearity : about +/- 50mrad
-30000 -20000 -10000 0 10000 20000 30000-50
-40
-30
-20
-10
0
10
20
30
40
Non
linea
rity,
ura
d
LVDT, V
-30000 -20000 -10000 0 10000 20000-60
-50
-40
-30
-20
-10
0
10
20
30
No
nlin
ear
ity,
rad
LVDT, V
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Stability
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The goniometers are very SENSITIVE to any mechanical disturbance
The design is SOFT. “Don’t touch” should be placed everywhere
We can move it only in work direction to avoid all gaps
Mechanical stability
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Stability Stability of LVDT during 14 hours looks quite good (*)
Gonio2, LVDT
3-5 mrad
(*) with averaging to reduce the noise
Repeatability Preliminary estimation for angular motion
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-30000 -20000 -10000 0 10000 20000 30000
-70-60-50-40-30-20-10
0102030405060708090
No
nlin
ea
rity
, ra
d
LVDT, V
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Alignment system
Crystal align andAngle measurement on the tank
T ank
D i g i tal Auto c o l l i m ato r
P e ntapr i zm 1
P e ntapr i zm 2
C r ys tal 1 C r ys tal 2
R e fe r e nc e m i r r o r
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Crystal 1
Crystal 2
Ref. mirror
Photos of alignment system
Digital autocollimator
Reference mirror
Laser
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Penta prizm
Viewport
Sources of uncertainty• Initial orientation of the alignment rail to
the tank geometry +/- 350mrad• Nonlinearity of goniometers +/- 50 mrad
21
Conclusions
We can use this goniometers with some magic gestures right now
BUT
To reach better results in the future we have to develop a new goniometer
22