Use ofSiesta in VIRGO commissioning

Lisa Barsotti University of Pisa – INFN Pisa

For the Virgo collaboration

Caltech, December 19th 2003

OutlinesOutlines

Introduction to SIESTA

SIESTA as locking tool: Commissioning of the central interferometer (CITF)

Commissioning of the first Virgo 3-km cavity

Recombined mode

Lock of the full Virgo

Towards a complete simulation:

Optics Modal simulation

Mechanics Superattenuator tuning

Inertial damping

Local controls

Hierarchical control

The SIESTA codeThe SIESTA code

SIESTA: time domain simulation of Virgo Objects defined as C structure

Sub-routines written for each sub-system

Signal structure used to relate the different elements of the simulation

Simulation parameters defined in ascii configuration files (SIESTA cards)

An example of configuration cardAn example of configuration card LASER

IOlaser laser 0 NULL 1.064e-6 0.14 NULL freq_noise.out 0. 2.15264e-2 .50 NO 2

P laser waist

m+nclock

PHASE MODULATOR

USignal carrier 0.96 USignal sb1 0.05 USignal sb2 -0.05

OPmod mod 0 laser.oBeam 3 0. 6.264080e6 -6.264080e6 carrier NULL sb1 NULL sb2 NULL

OPTICAL CONFIGURATION

OPcavity itf 0 mod.oBeam MiSuNIb MiSuNEf YES NULL

Dynamical simulationMirrors surface

MIrror MirNI 0 SuNI.dxyzt misNI.out NULL MiSuNIb 6.3807 0. 0. 1. 0. 0

MIsurf MiSuNIb 0. .1 0. 0. 0. 0.8819765 7.75e-6

CAVITY MIRRORS

R losses

Output frames: data fast Output frames: data fast visualizationvisualization

Time Plot

FFT Histogram 1-D

TFHistogram 2-D

FFT Time

Plots savable also as .C, .root, .ascii for deeper analysis (ROOT, VEGA, MATLAB)

SIESTA link to real time controlSIESTA link to real time control

SIESTA

Control signalsPhotodiodes signals

Algorithms running in the global control

SIESTA link to real time controlSIESTA link to real time control

Control signalsPhotodiodes signals

Algorithms running in the global control

VIRGO

Commissioning of the Virgo CITF - I

Study of the CITF lock acquisition

Gains and triggers computed by the simulation

Strategy directly transfered in the Virgo global control system

West and recycling mirrors controlled

Commissioning of the Virgo CITF - II

Recycling cavity power

Main trigger

Correction PR

Correction WI

Lock event

Commissioning of the north cavity

Feedback characterization:

• optical gain

• open loop transfer function

Analysis of the lock algorithm efficiency

• linearized error signal

• no linearized error signal

Comparison with real data (C1 run)

Real actuators, real photodiodes, computational delays included in the simulation

Commissioning of the north cavity - I

B1

T=8%

T=50 ppm

T=12%6 W

B5

B7

Optical scheme

Commissioning of the north cavity - II

Lock acquisition control scheme

B7

B1p

BS

NENIPR

Hz

|Gain

|

frequency

1 pole at 0.01 Hz

2 zeros at 10 Hz

2 poles at 800 Hz

1 pole at 1000 Hz

Commissioning of the north cavity - II

Asymmetric trigger on the trasmitted power

Trigger opening:

50 %Trigger closing:

1 %

Linearized error signal: Pr_B7_DC

Pr_B1p_ACp Switch to B1 with the OMC

locked

1/m 102.4 8Optical Gain: Measured

Simulated

Transfer Function Open Loop – Measured

Measured injecting white noise

M

G

zErr

zGc

zCorr

noise

Unity Gain @ 50 Hz

Gain margin:

3

Phase margin:

30°

Transfer Function Open Loop – Simulated

Gain margin:

3.3

Phase margin:

35°

Unity gain @ 55 Hz

Measured injecting white noise

M

G

zErr

zLock

zCorr

noise

Transfer Function Open Loop – Measured & Simulated

simulatedmeasured

Gain

Phase

Lock Algorithm Efficiency – I with the linearized error signal

24 locking events collected locking and delocking the cavity

for 20 minutes (GPS 752873880 – 752875080)

23 lock acquisition at the first attempt, only 1 failed locking attempt

A typical locking event

Lock Algorithm Efficiency – I Relative velocity between the mirrors computed for each locking attempt

8 m/s: maximum velocity for the lock acquisition success

12.5 m/s: velocity of the failed event

Failed locking attempt

v ~ 12.5

sμm

sμm

8

2.5 m/s: mean value of the

velocity

Lock Algorithm Efficiency – I

Gain due to the linearization:

Constraints on the velocity according to the theory:

10

33

m

Fv

λαBv

BΔt

MAXMAX

MAX

2

2

1

sμm

sμm

~ 10

Linearized error signal

No Linearized error signal

m

gain limited by the noise

~ 10

Lock Algorithm Efficiency - I Simulation

With velocity lower than 10 m/s lock at the first attempt

With velocity higher than 10 m/s lock at the second attempt

Lock failed

Sweep at 12 m/s :

Lock event

Lock Algorithm Efficiency – II

with the no linearized error signal

26 locking events collected locking and delocking the cavity

for 20 minutes (GPS 752873880 – 752876280)

14 lock acquisition at the first attempt, 12 after some

failed attempts

Locking always acquired in few

seconds

Lock Algorithm Efficiency – II

Failed locking attempts

Maximum velocity measured for a locking event: sμm3.5 Constraints on the velocity according to the theory:

m

Fv

λBv

BΔt

MAXMAX

MAX

2

2

1

3.3

3.3 sμm

sμm

Lock Algorithm Efficiency - IISimulation

Maximum velocity measured for a locking event:

With higher velocity, lock acquired after some attempts, in few seconds

sμm2

Sweep at 2.5 sμm

Recombined Optical Scheme

B1

T=8%

B5

B7

B8

B2

Reconbined Control Scheme

B1

B5

B7

B8

B2

north cavity controlled with B5

west cavity and michelson controlled at

the sime time

N_tras_power W_tras_power B1_power

Lock of the N cavity

Lock of W cavity and michelson at the same

time

to be tuned

Recombined: preliminary simulation

Lock acquisition of the full Virgo - I

Multi–states approach (LIGO scheme)

Dynamical inversion of the optical matrix

Lock acquisition of the full Virgo - I

Algorithm in a subroutine C++ in the global control use the same algorithm for the SIESTA simulation

simulation in progress

OutlinesOutlines Introduction to SIESTA

SIESTA as locking tool: Commissioning of the central interferometer (CITF)

Commissioning of the the first Virgo 3-km cavity

Recombined mode

Lock of the full Virgo

Towards a complete simulation:

Optics Modal simulation

Mechanics Superattenuator tuning

Inertial damping

Local controls

Hierarchical control

Modal simulation

High order modes (n + m ≤ 5 )

• compromise with the computational time 1 sec @ 20

kHz ⇒ 45 sec

Check with other codes in progress

0.113

misalignment of 2 rad in y of the curve mirror

Suspensions complete simulation: the SA

Transfer function betweeen force on steering filter and YAW mode of the mirror

RED simulation

BLACK measurement

Siesta file with the SA description

Inertial damping

Simulation tuning

zz

x

y

marionetta

reference mass

test mass

The Last Stage of the SA

Local controls system

Sensing: angular readout ( x e y ) of marionetta and mirror, position readout of the mirror along the optical axis;

Filtering: filtering of the signals achieved in the sensing phase;

Driving: control of the angular position of mirror and marionetta by feedback on the marionetta; control of the mirror position along the optical axis (z) by feedback to the reference mass.

MARIONETTA: x and y angular readout MIRROR: readout of x e y

and of the z position

measurement of the z position

SensingSimulation in

progress

Filtering & Driving

marionetta

reference mass

mirror

z

z Damping

x y

x y

marionetta

mirror

marionetta loop

mirror loop

Marionetta loop

action time

x y

Unity gain @ 5 Hz Unity gain @ 5 Hz

z Damping

action time

0.6 Hz excitation by white noise injection

Unity gain @ 2 Hz

0.6 Hz resonance compensation

Optimization of the z damping loop – I

10 sec

zCorr zMirrorm

Hz

Unity gain @ 0.65 Hz

measured

Open loop transfer function

Damping time sec

Optimization of the z damping loop – II

simulated

Open loop transfer function

Critical damping @

1.45 Hz

Hz

mV

zCorr zMirror

2 sec

Optimization of the z damping loop – III

measured after the optimization

mV

~ 2 sec

zCorr zMirror

Guadagno open loop

Hz

Critical damping @

1.45 Hz

Hierarchical control

marionetta

reference mass

mirror

z

Control from the reference mass

Control from the marionetta

Transfer function betweeen force on steering filter and z movement of the

mirror

simulation work in progress

North cavity complete simulation

Modal and dynamical optical simulation

Laser frequency noise

noise taken from the real data

Real actuators and real photodiodes

Computational delays

Asymmetry in the coils

6 dof superattenuators, with:

angular controls

longitudinal damping

inertial damping

Conclusions

Time domain simulation: mainly tool for locking studies

Frames output, link with real time control system

Now work on suspensions control and high order modes simulation:

improve the plane-wave lock acquisition algorithm

WFS

hierarchical control (marionetta)

Noise analysis