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TutorialSelection of Vibration Isolators
Masaki HosodaDec. 7, 2009
OPTI 521
Dec. 7, 2009 OPTI 521 2
Contents
PurposeMotivationTwo types of Vibration Isolation
Passive Vibration IsolationActive Vibration Isolation
Summary
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Purpose of this presentation
Let you knowhow vibration isolation workshow to select vibration isolatorsexamples of application
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Motivation
Vibration Isolation is important forOptical measurementsOptical fabricatons
From Zygo, GPI serieshttp://www.zygo.com/?/met/interferometers/gpi/flashphase/
From TMC, STACIS
http://www.techmfg.com/appnotes/SematechAppnote.htm
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Two types ofVibration Isolation
Passive Vibration IsolationMass, Spring, and DamperCan isolate high frequency (5Hz~)
Active Vibration IsolationMass, Spring, Damper, and Feedback or FeedforwardCan isolate low frequency (~5Hz)+ high frequency
From TOKKYOKIKIhttp://www.tokkyokiki.co.jp/technology/technology_a.html
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Passive Vibration Isolation2
1 12n
C
k Cfm Cπ
⎛ ⎞⎛ ⎞⎜ ⎟= − ⎜ ⎟⎜ ⎟⎝ ⎠⎝ ⎠
C/CC is Critical damping ratio CR
•You want fd/fn•fd is defined.•Then fn should•C/CC should•k should•m should
Advantage•Low costDrawback•Amplification Region•Not stable.
From Barry isolators selection guide.pdf
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Selection ofPassive Vibration Isolator
Determine fd (Disturbing frequency)and Min. fn
2d
nff =
Use direct measurementor Rule of Thumb
From Yoder
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Example ofPassive Vibration Isolator
From THORLAB
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Active Vibration Isolation
Advantage•No Amplification RegionDrawback•Cost•algorism•Need reference
Feedback
Feedback + Feedforward
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Selection ofActive Vibration Isolator
Need correct referenceNeed correct model
Fast responseFeedforward+ Feedback
Slow responsedurable for unexpected disturbance
Feedback
DrawbackAdvantage
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Example ofActive Vibrartion Isolator
Vibration isolation platform
1. Pressure (Force)2. Position3. Velocity
Lithography Stage by Canon
S. Wakui, “Active vibration isolator, exposure apparatus, exposure method and device manufacturing method”United States Patent 6,286,644 B1 (2001)
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Summary
Two types of Vibration IsolationPassive Vibration Isolation
Low cost, works for high frequencyHave amplification region, Not stable
Active Vibration IsolationNo amplification region, works for low freq.Need Algorism and reference
