Overview of ACIGA high performance vibration isolator

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.

112233

44

55

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)