Progress on stabilisation issues

1
Progress on stabilisation issues

• A.Jeremie, L.Brunetti, B.Bolzon, N.Geffroy
• LAPP, Annecy

2
Program

• Introduction
• Nanometre scale instrumentation
• Active stabilisation gt simulation and
  experimental results
• Combine passive and active stabilisation
• Conclusion

3

• Introduction

4
Beam sizes in the nanometre range
The CLIC luminosity performance critically
depends on the main linac quadrupole vertical
stability (lt1nm _at_ 1Hz) and the final doublet
stability (lt0.1nm _at_ 4 Hz) in noisy site
Linac
1.3nm
FF
0.2nm
Measurement of the quadrupole vibrations on
active table in vertical direction compared to
linac and Final Focus (FF) tolerances at 4Hz (in
2003)
4 Hz
S.Redaellis PhD 2003
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Introduction
Example of spectral analysis of different
disturbance sources

• Ground motion

• Acoustic disturbance

A pink noise on a large bandwidth
Seismic motion
Cultural noise

• Amplified by the structure itself the
  eigenfrequencies

gtneed to isolate and compensate
6

• Nanometre scale instrumentation

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First results of stabilisation in the nanometre
scale
Experimental set-up
Feedback input Sensor at the free-part of the
beam
Feedback output Actuator at the fixed-part of
the beam
PCI6052 DAQ Sensor acquisition and actuator
control
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State of the art inertial sensors

• NI PCI-6052 Multifunction DAQ

Fast card
Low noise card

• Compatible Matlab/Simulink (Softwares used for
  the algorithm)

nm stabilisation equipment exists
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• Active stabilisation gt simulation and
  experimental results

10
Active compensation
The prototype

• The large prototype and its instrumentation

2.5 m long

• Actuators used for the active control of
  vibration

• Force 19.3 N
• Maximal displacement 27,8 µm
• Resolution 0,28 nm

- A stacking of PZT patches -
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Why a fixed-free configuration?
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Active compensation
Another approach of the problem
L.Brunetti

• Test an intermediary solution to control a
  larger bandwidth

A local model of the process
A local model of the process
A complete model of the process
A knowledge of the process at strategic points
f0
f1
fi
1 - A complete model of the structure too
complex
2 - A knowledge of the structure at strategic
points the initially developed algorithm
3 - A local model of the structure for the
disturbances amplified by eigenfrequencies.
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Brief summary
Results
Rejection of 6 resonances (without and with
rejection)
by L.Brunetti
Resonances of -beam -support
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Active control CIM
Tests in simulation

• Integration of a finite element in a feedback
  loop

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Active control CIM
Tests in simulation

• Integration of the finite element model in the
  feedback loop

• Example of result

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Active control CIM
Tests with the large prototype

• Results Power spectral density

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Active control CIM
Tests with the large prototype

• Results integrated displacement RMS

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Tests with the large prototype quiet room
integrated displacement RMS (with active table ON)
1 nm
Actuator electronic noise at 50 Hz
Combining isolation and compensation
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Combine passive and active stabilisation
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Active isolation
Reasons of this study and the STACIS feet

• In the case of a possible partnership, we have
  no competence about active isolation.
• In the case of the development of a low cost
  table (this one is very expensive), we have no
  information about the mechanism (mainly the
  feedback loop).
• STACIS foot

(Thesis of S. Redealli)

• Passive isolation attenuates all the high
  frequency disturbances but amplifies the low
  frequency disturbances (like a resonant filter).
• Active isolation attenuates the disturbance
  amplified by the passive isolation (low
  frequencies disturbances).

• Test of active isolation on a small mock-up

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Active isolation
The small and elementary mock-up

• Association of active and passive isolation

• The passive layer

Require active isolation ?f
Passive isolation is efficient
Resonant frequency of the rubber
? Not heavy enough to use industrial products,
but it is possible with a larger prototype.
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Conclusions

• Hardware

• Acquisition chain able to measure at a nanometre
  scale
• Actuators to create nanometre displacements
• A real time solution to run automatics algorithm

• Control

• 2 types of algorithms for active compensation
• A beginning of study for active isolation

• We have succeeded in stabilizing an elementary
  structure at a nanometre scale with a natural
  environment.

• Future prospects

• The purpose now is to obtain the best possible
  stabilization all along the elementary mechanical
  structure (lower or equal to the imposed
  tolerance)