Transcript Characterization of PZT Coupling between the two axis

Actuators for Wavefront Scanning and Fast
Quadrant Alignment
S. Avino, E. Calloni, R. De Rosa, L Di Fiore, M. Parisi, A. Tierno
Detector Meeting – Amsterdam, July 5 2006
Summary
- Motivation
- Description of the set-up used to characterize the Tilting Mirrors
- Measurements: TF, Linearity, Repeatability
- Comparison between the actuators
- Proposed implementation of Scanning PZT – Hardware and Software involved
- Proposed implementation of Fast Quadrant Alignment – Hardware and Software involved
Detector Meeting – Amsterdam, July 5 2006
Motivation
The activities on the Wavefront Scanning System and the Fast Quadrant Alignment involve the
testing and the set-up of very similar optical system, that is a tilting mirror used to scan the beam in
the first case and to center the beam on the quadrant in the other case.
Two actuators were characterized to understand their effectiveness and their compliance with the
requirements.
A possible implementation scheme, for both the application, is also presented (Discussed with LAPP).
Detector Meeting – Amsterdam, July 5 2006
Characterization of the devices
PZT/FSM
To characterize both the PZT tip/tilt mirror and the FSM we used the same optical set-up
-Laser source
-Tilting mirror (PZT or FSM)
-Position Sensing Photodiode and related electronics (Same used for VIRGO local controls)
Tilting Mirror
Driver
DAQ
PSD
Electronics
PSD
Tip/Tilt
Mirror
He-Ne Laser
Detector Meeting – Amsterdam, July 5 2006
Characterization of PZT
Transfer Function Measurement
The transfer function of the PSD
electronic readout was measured to
correct the results.
Mag (V/  m)
The transfer function was measured by
injecting white noise to one input
channel of the tilting mirror driver.
The measure was performed in both
open loop and close loop conditions.
10
x OL
x CL
3
2
10
-1
10
10
1
0
10
Frequency (Hz)
10
2
200
100
Phase (deg)
The figure shows the behaviour of the x
axis. The y axis is very similar.
0
-100
-200
-1
10
10
0
1
10
Frequency (Hz)
Detector Meeting – Amsterdam, July 5 2006
10
2
Characterization of PZT
Comparison between the axis
The difference is not related to a bad
tuning of the loop electronics (the
comparison performed in OL conditions
shows the same difference).
Mag (  m/V)
The PZT actuator shows a difference in
the calibration of the x and y axis.
The ratio between the x and y calibration
is about 1.4 in CL and 1.5 in OL.
x
y
3
10
2
10
-1
10
The figure show the result obtained in
close loop conditions
0
10
1
10
2
10
Frequency (Hz)
200
Phase (deg)
100
0
-100
-200
0
10
1
10
Frequency (Hz)
Detector Meeting – Amsterdam, July 5 2006
2
10
Characterization of PZT
Coupling between the two axis
The PZT actuator also show a small
coupling of the channels.
Mag (  m/ V)
The figure shows the direct and the
indirect transfer function.
10
In the worst case the coupling is 2.5% in
CL and 0.5% in OL.
10
2
0
10
-1
10
0
1
10
Frequency (Hz)
10
2
200
100
Phase (deg)
This difference may be related to a
coupling between the sensors.
10
4
0
xx
xy
yx
yy
-100
-200
-1
10
0
10
1
10
Frequency (Hz)
Detector Meeting – Amsterdam, July 5 2006
2
10
Characterization of PZT
Linearity
The linearity of the actuator was tested
by separately scanning the two axis with
a ramp.
2500
2000
1500
The measurement was performed in OL
and CL condition.
The figure shows the results for the x
axis. Similar results were found on y
axis.
1000
Position (  m)
As expected, in OL the hysteresis is
evident.
OL
CL
500
0
-500
-1000
-1500
-2000
In the central zone, where the PSD is
very linear, the measured linearity was
about 0.4%
-2500
-3
-2
-1
Detector Meeting – Amsterdam, July 5 2006
0
1
Voltage on x input(V)
2
3
Characterization of PZT
Repeatability
The repeatability of the PZT device was
test by applying a square wave signal in
input and by monitoring the position of
the beam on the PSD.
The figure refers to a motion along the x
axis
7000
The measured repeatability is 25 rad.
The results are similar on each axis.
6000
5000
7000
Counts
6000
Counts
5000
4000
3000
4000
2000
3000
2000
1000
1000
0
120
125
130
135
0
-200
-150
-100
Position (m)
Detector Meeting – Amsterdam, July 5 2006
-50
0
50
Position (m)
100
150
200
Characterization of FSM
Transfer Function Measurement
The ratio of the x and y calibrations is
suspiciously close to the PZT value (x/y
about 1.4). Anyway from other tests
performed using a different electronic
set-up we found the same result.
10
Mag (  m/V)
The transfer functions of the FSM were
measured in the same way as for the
PZT. The result are similar.
10
10
4
x
y
3
2
1
10
-1
10
10
0
10
Frequency (Hz)
1
10
2
200
Phase (deg)
100
0
-100
-200
-1
10
0
10
1
10
Frequency (Hz)
Detector Meeting – Amsterdam, July 5 2006
2
10
Characterization of FSM
Coupling between the two axis
The worst coupling between the two axis
is about 4%
10
Mag (  m/V)
Also the coupling between the twe
degres of freedom was evaluated. The
result are similar to the PZT actuator.
10
10
10
4
2
0
-2
10
-1
10
0
1
10
Frequency (Hz)
10
2
Phase (deg)
200
100
0
xx
xy
yx
yy
-100
-200
-1
10
10
0
Detector Meeting – Amsterdam, July 5 2006
1
10
Frequency (Hz)
10
2
Characterization of FSM
Linearity
The graph shows the linearity of the
FSM on both axis, measured in the
middle zone of the PSD (2 mm side).
1500
1000
The estimated linearity is about 2%
Position (  m)
500
0
-500
-1000
-1500
-2
-1.5
-1
-0.5
0
0.5
Driver Voltage (V)
Detector Meeting – Amsterdam, July 5 2006
1
1.5
2
Characterization of FSM
Repeatability
Also the repeatability of the FSM device
was test by applying a square wave
signal in input and by monitoring the
position of the beam on the PSD.
The figure refers to a motion along the x
axis
8000
The measured repeatability is 75 rad.
The results are similar on each axis.
7000
6000
5000
4500
5000
Counts
4000
3500
Counts
3000
4000
3000
2500
2000
2000
1500
1000
1000
500
0
70
75
80
85
Position (m)
90
95
100
0
-100
-50
Detector Meeting – Amsterdam, July 5 2006
0
Position (m)
50
100
Characterization of device
PZT vs FSM
Here follows the main characteristics of these two devices.
PZT
FSM
Requirement
Bandwidth
40 Hz
30 Hz
50 Hz
Linearity
0.4 %
2%
Repeatability
25 rad
75 rad
Detector Meeting – Amsterdam, July 5 2006
20 rad
Implementation
Proposal for Scanning PZT
The most efficient solution seems to be:
- Make 2 DAC channels available (May be in DAQ Room);
- Use the CaRT servers to produce the scanning pattern to drive the tilting mirror;
- Standard Readout for the photodiode (Detection Lab);
- Probably (?) 2 ADC channels to acquire the scanning pattern from the monitor signals of the Tilting
Mirror Driver.
Detector Meeting – Amsterdam, July 5 2006
Implementation
Proposal for Scanning PZT
Photodiode
Electronics
Tilting Mirror
Tilting Mirror
Electronics
Optional
RIO
Dem
Board
ADC
RIO
DAC
CaRT
Pr
D2
D2
Detector Meeting – Amsterdam, July 5 2006
Analog connection
VME BUS
Processes
VME level ShMem
Data Flow
Implementation
Proposal for Fast Quadrant Alignment
For this application the solution seems more clear:
- Quadrant DC are already read by the Pr server;
- The new Pr server (thanks to Alain and Edwige) is able to perform simple math on the input
channels. In this way it become possible to build the error signals. Also a minimal signal filtering is
already possible inside the Pr. These correction signals are sent to two DAC channels (2 for each FQa).
This new functionality should be completed within this week.
- The correction signals, that are proportional to the beam misalignment, can be sent to the DAQ
directly by the Pr.
Detector Meeting – Amsterdam, July 5 2006
Implementation
Proposal for Fast Quadrant Alignment
To other stages
Quadrant
Electronics
Tilting Mirror
Translation Stage
Driver
Translation stage
Translation Stage
Driver
Translation Stage
Driver
Tilting Mirror
Electronics
RIO
ADC
Qa
RIO
DAC
Qa
Pr1
DAQ
Pr
Pr2
D1
D2
Detector Meeting – Amsterdam, July 5 2006
Analog connection
RS232 connection
VME BUS
Processes
CPU level ShMem
VME level ShMem
Data Flow
New Connections
(dashed)