Overview of ACIGA high performance vibration isolatorOverview of ACIGA high performance vibration isolator
Jean-Charles DumasJean-Charles DumasEu-Jeen ChinEu-Jeen Chin
Chunnong ZhaoChunnong ZhaoLi JuLi Ju
David BlairDavid Blair
Inverse pendulum
LaCoste stage
Self-Damped pendulums
Control mass
Test mass
Roberts Linkage
Euler stage
1
5
4
32
4
4
5
5
The AIGO vibration isolator combines several techniques.
Anti-Springs in most stages reduce mode frequencies.
The Pre-isolator combines two horizontal stages, an inverse pendulum and a Roberts Linkage, and one vertical LaCoste stage, all with resonant frequencies below 0.1Hz.
– The inverse pendulum.– The LaCoste linkage provides vertical pre-isolation.– The Roberts linkage.
The isolation consists of three similar stages.– A 40kg pendulums with Euler spring vertical
suspensions.– Each stage comprises a rocker mass and self
damped pendulum with eddy current damping.
Local control implemented at pre-isolation stage:– Coil and magnet actuation for positioning and
damping for both the inverse pendulum and LaCoste stages.
– Slow vertical control by coil spring heating in the LaCoste stage for thermal drift and creep correction.
– Slow position control using the Roberts linkage by heating suspension wires.
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Vibration Isolation TechniquesVibration Isolation Techniques
(analogue control)
What is an anti-spring?
An anti restoring forcei.e. instability
Example: an inverse pendulum
mass
kspring kantim
Inverse Pendulum
Lacoste Linkage
Mass
rigidlinks
platform
springs
Pre-isolation local control
• Horizontal (inverse pendulum) position control with magnetic actuators
• Vertical (LaCoste linkage) position control
– with magnetic actuators
– heating of springs
Roberts linkage
Roberts Linkage Frequency Response
Self-Damped pendulums(3 Stages)
Viscous damping
Pivot
Double wire suspended on a pivot, free to swing.
40kg Rocker mass, high moment of inertia.
Self-Damping SchematicSelf-Damping Schematic
Vertical Euler Springs(3 Stages)
Load
Euler Springs Clamps
Flexure
Rotationalarm
0.2 0.5 1 2 5FrequencyHz
-80
-60
-40
-20
0
20
40
Bd
Horizontal Frequency Responce3 Stage Horizontal Frequency Response
Model assuming Q = 20
with Self-Damping
without Self-Damping
Al web rigidly clamped to the suspension tube
Copper plates attached to Al web, rigid with respect to suspension tube
Magnets, attached to rocker mass
Rocker mass
Rotational arm rests on Euler springs and is suspension point for next stage
Euler springsBottom of springs is clamped
to suspension tube
Integrated 3D isolator stageIntegrated 3D isolator stage
Progress at Progress at AIGOAIGO
Assembly of two complete vibration isolators in progress at the AIGO test facility.
Optical cavity differential motion testing in AIGO east arm planned late 2005.
The endThe end
Please visit the lab if you haven’t already done so!
Deleted Scenes
Roberts linkage
-0.05 0 0.0520
30
40
50
60
70
80
90
Suspension point height (m)
Isol
atio
n F
loor
(dB
)
Isolation LimitResonant frequency
-0.05 0 0.050
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Res
onan
t Fre
quen
cy (
Hz)
0.1 0.2 0.3 0.4 0.520
40
60
80
100
120
Radius of gyration of tuning mass (m)
Isol
atio
n F
loor
(dB
)
Isolation LimitResonant frequency
0.1 0.2 0.3 0.4 0.50.0294
0.0295
0.0296
0.0297
0.0298
0.0299
Res
onan
t Fre
quen
cy (
Hz)
Al web rigidly clamped to the suspension tube
Copper plates attached to Al web, rigid with respect to
suspension tubeMagnets, attached to
rocker mass
Rocker massVertical stage
One pendulum stageAl web rigidly clamped to the suspension tube
Copper plates attached to Al web, rigid with respect to
suspension tubeMagnets, attached to
rocker mass
Rocker massVertical stage
One pendulum stage
pivotM M
L
4 L
pivotM M
L
4 L
Copper plates
Viscous damping
Pivot
Suspension wire
Rocker mass, high moment
of inertia.
2D flexuresRocker mass
magnets
Pin connection
Vertical spring stage
(a) (b)
Copper plates
Viscous damping
Pivot
Suspension wire
Rocker mass, high moment
of inertia.
2D flexuresRocker mass
magnets
Pin connection
Vertical spring stage
(a) (b)
