Control strategy in the vibrtion isolation system for KAGRA Ryutaro Takahashi (Institute for Cosmic...
-
Upload
theresa-nicholson -
Category
Documents
-
view
216 -
download
0
Transcript of Control strategy in the vibrtion isolation system for KAGRA Ryutaro Takahashi (Institute for Cosmic...
Control strategy in the vibrtion iControl strategy in the vibrtion isolation system for KAGRAsolation system for KAGRA
Ryutaro TakahashiRyutaro Takahashi(Institute for Cosmic Ray Research, Univ. of Tokyo(Institute for Cosmic Ray Research, Univ. of Tokyo
/ / National Astronomical Observatory of Japan)National Astronomical Observatory of Japan)
The 3rd Korea-Japan workshop on KAGRASogang University, Seoul 21-22 December, 2012
ContentsContents1.1. VVibration isolation systemibration isolation system for KAGRA for KAGRA2.2. Control systemControl system3.3. Low frequency disturbanceLow frequency disturbance
1.1. Seismic noiseSeismic noise2.2. Ground strainGround strain3.3. Thermal driftThermal drift4.4. Newtonian noiseNewtonian noise
4.4. Control strategyControl strategy1.1. Hierarchical contolHierarchical contol2.2. Common mode rejectionCommon mode rejection3.3. Feed-forward controlFeed-forward control
5.5. ConsiderationConsideration6.6. SummarySummary
11.. V Vibration isolation systemibration isolation systemfor KAGRAfor KAGRA
Top filter[Filter0]
Inverted Pendulum (IP)
Bottom Filter (BF)
Test Mass (TM)Recoil Mass (RM)
Pre-isolator
Payload
Filter chain
Schematic Schematic view of Seiview of Seismic attenusmic attenuation systeation syste
mm(SAS)(SAS)
Type-A/BType-A/B
Intermediate Mass (IM)Intermediate Recoil Mass (IRM)
Geometric Anti-Spring (GAS)Filter1 (Filter1~3 in Type-A)
Type-AIP + GAS Filters (5 stages)
+ Payload (23kg, cryogenic)
Type-BIP + GAS Filters (3 stages)
+ Payload (10kg/20kg)Type-C
Stack + Single/Double-pendulum (~1kg)
Disposition of vibration isolation systemDisposition of vibration isolation system
Type-A (2-layer structure) Type-A (2-layer structure)
Upper tunnel containing Upper tunnel containing pre-isolator (short IP pre-isolator (short IP and and ttop filter)op filter)
1.2m diameter 5m tall 1.2m diameter 5m tall borehole containing borehole containing standard filter chainstandard filter chain
Lower tunnel containing Lower tunnel containing cryostat and payloadcryostat and payload
8m
5m
7m
1F
2F
Type-BType-B
IP base is supported IP base is supported by the outer frame.by the outer frame.
Pre-isolator is the Pre-isolator is the same as Type-A’s.same as Type-A’s.
Type-B Payload
Rigid table
Type-C Payload
Stack
Type-CType-CType-B payload Type-B payload
on on rigid tablerigid table
22.. Contol Contol system system
Pre-isolatorPre-isolator
Type-B PayloadType-B Payload
Linear variable differencial transformer (LVDT) and Voice coil actuator
Embeded LVDT-actuator unit on the inverted pendlum.
Evaluation of LVDT. The noise level was less then 0.1m at 0.01-0.1Hz. The noise level is proportional to DC offsets.
Prim
aly
co
il
Se
con
da
ly c
oil
Yo
ke
Co
il
Magnet
VC
LVDT
Evaluation of L4-C geophones in Kamioka. The noise level was 5x10-11 m Hz1/2 at 1Hz. Test of geophones and preamplifirs
in Kashiwa.
Vertical
Velocity responce of L4-C geophone.
Ground 1
Ground 2
Differential
Inertial sensor(Geophone)
Motor slider and Hydraulic leveler
Level of the IP base is tuned by the tripodal hydraulic piston.
Position of the IP is tuned by the motor sliders to compensate the DC component of the feedback signal to the actuator.
The sensitivity is ~ 2.5x10-10 m/Hz1/2 at 1 Hz, and ~7x10-10 m/Hz1/2 at 0.1 Hz.
The linear range is ~ 1mm.
Optical sensor and electro-magnetic actuator(OSEM)
Optical lever
by K. Agatsuma
Type-B
Control of IPControl of IP(example of (example of
TAMA)TAMA)PS
Length
ACC, LVDT
X
ACC
LVDT
Actuator
X
Y
Global control of cavity Length after cavity lock
Damping of excited torsion mode using Position Sensor
33.. Low frequency disturbance Low frequency disturbance
Peterson noise model
Acceleration spectrumDashed lines: Peterson high and low noise modelsSolid lines: noise spectral level for IRIS station (3 components)
Global high (NHNM) and low (NLNM) noise models represent upper and lower bounds of a cumulative compilation of representative ground acceleration power spectral densities.
3-1. Seismic noise
J. Havskov and G. Alguacil, “Instrumentation in Earthquake Seismology”, Springer, 2009
Origin of seismic noiseMan made noise (Cultural noise)•Originates from traffic and machinery with high frequencies (>2-4Hz).•Propagates mainly as high-frequency surface waves which attenuate fast with distance and decrease strongly in amplitude with depth.•Has a large difference between day and night.
Wind noise•Makes any object move.•Usually high frequency, however large swinging objects can generate lower frequency signals.
Horizontal noise attenuation (dB, spectral acceleration density) as a function of depth and period
Ocean generated noise (microseisms, microseismic noise)•Seen globally.•Long period (10~16s): generated only in shallow waters in coastal region.•Shorter period (peak~5s): generated by the superposition of ocean waves of equal period traveling in opposite directions.
3-1. Seismic noise
3-2. Ground strain
JGW-G1000063 by A. Araya
Tidal variation
3-3. Thermal drift
R. Takahashi, et al : Rev. Sci. Instrum. 73 (2002) 2428
Stack isolation in Type-C system
NaNaiive estimationve estimation
Generally this noise is Generally this noise is smaller in underground.smaller in underground.Large amount of moving Large amount of moving water due to melted snow water due to melted snow may make effective noise may make effective noise in spring around Kamioka.in spring around Kamioka.
3-4. 3-4. Newtonian noiseNewtonian noise
Ambient seismic waves induce density perturbations, which produce fluctuating gravitational forces.
Estimated Newtonian noise in LIGO (Hughes and Thorne, PRD 58 122002)
44.. Control strategy Control strategy
4-1. Hierarchical control4-1. Hierarchical control
Actuation Sensing Control Band
Moter Slider on IP
Offset of VC
1/day
Voice Coil on IP
LVDT <0.1Hz
Geophone 0.1-1Hz
Global <0.1Hz
Intermediate Mass
OSEM <1Hz
Global 0.1-1Hz
Test Mass Global 1-1kHz
Actuation Sensing Control Band
Moter Slider on Filter0
Offset of VC
1/day
Voice Coil on Filter0
LVDT <1Hz
Voice Coilon Filter1-3
LVDT 0.1-1Hz
Intermediate Mass
OSEM <1Hz
Displacement
horizontal vertical
4-1. Hierarchical control4-1. Hierarchical control
Actuation Sensing Control Band
Hydraulic leveler on IP
Offset of VC
1/day
Moter Slider on IM
Offser of TM
1/day
Intermediate Mass
OSEM <1Hz
Test Mass Optical Lever
<1Hz
Global <0.1Hz
Actuation Sensing Control Band
Moter Slider on Filter0
Offset of TM
1/day
Voice Coil on IP
LVDT <0.1Hz
Geophone 0.1-1Hz
Intermediate Mass
OSEM <1Hz
Test Mass Optical Lever
<1Hz
Global <0.1Hz
Angle
pitch yaw
4-2. Common mode rejection (CMR)4-2. Common mode rejection (CMR)
The interferometer senses The interferometer senses not local displacement but lenot local displacement but length between mirrors.ngth between mirrors.The mirrors move in commThe mirrors move in common mode at low frequencies.on mode at low frequencies.Microseismic noise was redMicroseismic noise was reduced by the common mode ruced by the common mode rejection in TAMA or CLIO.ejection in TAMA or CLIO.Such a reduction is not expSuch a reduction is not expected in the 3-km cavity of Kected in the 3-km cavity of KAGRA.AGRA.
Witness sensor is effected by Witness sensor is effected by the the feed-back feed-back control.control.Witness sensor is NOT effected by Witness sensor is NOT effected by the the feed-forwardfeed-forward control. control.
4-3. 4-3. Feed-forward controlFeed-forward control
WitnessSensor
FilterWitnessSensor
Filter
Targetsignal
Targetsignal
WitnessSensor
Filter
Targetsignal
feed-backfeed-back feed-forwardfeed-forward
feed-forward (offline)feed-forward (offline)
Comparision with feed-back control
55. . ConsiderationConsideration There are many kinds of servo loops. Control bands arThere are many kinds of servo loops. Control bands ar
e limited by the sensing noises.e limited by the sensing noises.
A large disturbance at low frequencies should be fedbaA large disturbance at low frequencies should be fedback to the upper reaches considering phase delay.ck to the upper reaches considering phase delay.
Sensing signals must be diagonalized well for independSensing signals must be diagonalized well for independent controls.ent controls.
CMR at the low frequencies is not effective in the lengtCMR at the low frequencies is not effective in the length control of the 3-km cavity, it is expected only in the ceh control of the 3-km cavity, it is expected only in the center area.nter area.
Feed-forward control is useful in the cace of having indFeed-forward control is useful in the cace of having independent monitor like seismometer (seismic noise), strependent monitor like seismometer (seismic noise), strain meter (tidal variation), or gravity gradiometer (Newtain meter (tidal variation), or gravity gradiometer (Newtonian noise).onian noise).
66. Summary. Summary KAGRA employed the SAS which consists of an KAGRA employed the SAS which consists of an
inverted pendulum and geometric anti-spring filters.inverted pendulum and geometric anti-spring filters.
There are some kinds of displacement noise sources at There are some kinds of displacement noise sources at frequencies lower than 1Hz as well as observation banfrequencies lower than 1Hz as well as observation bandd..
The The vibration isolation systemvibration isolation system is controled by multiple sis controled by multiple servo loops using many kinds of sensors and actuatorservo loops using many kinds of sensors and actuators..
Hierarchical control is required considering sensing noiHierarchical control is required considering sensing noises, CMR and feed-forward loopsses, CMR and feed-forward loops..