Section 18 Survey of Microgravity Vibration Isolation Systems · Microgravity vibration isolation systems are required to provide an environment conducive to world-class science research

March 2-4, 2004 MEIT-2004 / Section 18 / Page 1

Survey of Microgravity Vibration Isolation Systems

Section 18Survey of Microgravity Vibration Isolation Systems

Dr. Mark WhortonPrincipal Investigator for g-LIMIT

NASA Marshall Space Flight Center



Outline:• Review of Vibration Isolation Technology• Survey of Flight Systems• Future Trends• Flight System Availability on ISS



Nomenclature

• COTS – commercial off-the-shelf• MVIS – Microgravity Vibration Isolation System• ISPR – International Standard Payload Rack• MSG – Microgravity Science Glovebox• DOF – Degree of Freedom



The ISS will provide a world-class research facility for microgravity science

Microgravity vibration isolation systems are required to provide an environment conducive to world-class science research

The acceleration environment is expected to significantly exceed acceptable levels

0.1

1

10

100

1000

104

105

0.01 0.1 1 10

D AC-8 (non-iso lated )D AC-8 (w ith SM erg .frequency var ia tion )System R equirement

RM

S A

ccel

erat

ion

(µg)

Frequency (Hz)50

SM Ergomtr

Crew Induc ed

Lab System

Vents S PP

RS

TRRJ

SSP-MG99-074A March 30, 2000



Why is Vibration Isolation Necessary for ISS?

Transmissibility

0.01Frequency (Hz)

0.1 1 10 100

1

0.1

0.01

0.001

0.1

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10

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1000

104

105

0.01 0.1 1 10

DAC-8 (non-iso lated )DAC-8 (w ith SM erg .frequency var ia tion )System Requirement

RM

S A

ccel

erat

ion

(µg)

Frequency (Hz)50

SM Ergomtr

Crew Induc ed

Lab System

Vents S PP

RS

TRRJ

0.1

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1000

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105

0.01 0.1 1 10

DAC8 (withot ARIS)DAC8 (with ARIS)System Requirement

RM

S A

ccel

erat

ion

(µg)

Frequency (Hz)50

SM ErgomtrLab Ergomtr

Crew Induced

Lab System

Vents SPP

RS

TRRJ



PositionControl Law

ReferencePositionCommand

+-

• Low Frequency Position Control Loop:• Maintains Centering• Allows quasi-steady accel estimation

AccelerationControl Law

ReferenceAccelerationCommand

-

• High Frequency Acceleration Control Loop:• Cancels Inertial Motion of the Platform• Allows “Good Vibrations”

QA-3000Accelerometers

accelerations

Isolation SystemPosition Sensor

relativepositionsVibration



•Low Cost•Low Maintenance•Reliable•No Power

•Isolate only higher freq ( > 1-10 Hz)•Typically requires large volume•Cannot mitigate payload induced vibrations•Resonance vs attenuation trade

Comparison of ApproachesType Advantages Disadvantages

Passive

Active Rack Level

(ARIS)

Active Sub-Rack Level

(g-LIMIT, STABLE, MIM)

•Low freq attenuation via large mass•Least power & volume (mult. payloads/single unit)•standard user interface

•Cannot mitigate payload induced vibrations•requires payloads to be “good neighbors”•highly sensitive to crew contact•Potential high maintenance

•Low freq attenuation via highgain feedback•Mitigates payload induced vibration•can be optimized for individual user

•More power & volume than rack-level (single payload/single unit)



• To date, three microgravity vibration isolation systems have been flight tested in orbit:

• STABLE (Suppression of Transient Accelerations By LEvitation)

• ARIS (Active Rack Isolation System)

• MIM (Microgravity Vibration Isolation Mount)

• Each system will be surveyed using data provided by each investigation team

Introduction



• Payload-level Isolation System• Developed jointly by NASA MSFC and Boeing (formerly MDAC)

• Flown on STS-73/USML-02, October 1995

• A Faster/Better/Cheaper approach• 4.5 months from ATP to delivery

• Utilized COTS components

• Necessitated robust control design

• Supported a fluid physics experiment

The STABLE Vibration Isolation System



Integration of Payload into STABLE Locker



STABLE Flight Unit



Payload Specialist Dr. Fred Leslie operating STABLE



UmbilicalDynamics

IsolatedPlatformActuator

AccelerationController

AccelerometerElectronics

PositionSensors

PositionController

-

BaseAcceleration

AccelerometerBias + Noise

STABLE Control System Block Diagram



STABLE: Typical Active Isolation Time Response



STABLE: Typical Active Isolation Frequency Response

Frequency (Hz)0.01 0.1 1 10 100



STABLE: Typical Active Isolation Attenuation



MIM Background

• The Microgravity Vibration Isolation Mount (MIM) has been developed over the past 10 years by CSA under the direction of Bjarni Tryggvason

• 2 MIM versions have been produced to date:

• First version of MIM is known as MIM-1:

- In operation for two years onboard Russian Mir space station since May 1996;

- accumulating over 3000 hours.



MIM Background• Second version of MIM is known as

MIM-2:- Flown onboard the Space Shuttle during mission

STS-85 with Canadian Astronaut Bjarni Tryggvason;- MIM-2 acquired a total of 100 hours of operations.



MIM-2 Description:• 8 wide gap Lorentz force actuators(magnets on flotor & coils on stator);• 3 light emitting diodes imaged on 3 position sensitive devices (PSD);• 6 accelerometers for monitoring stator & flotor acceleration



MIM-2 Summary for STS-85

0 5 10 15 20 25 303000

2000

1000

0

1000

2000

3000

T im e (seconds)

Acc

eler

atio

n (µ

g)A cceleration L evels of the Space Shuttle and M IM ’s Isolated P latform

Space shuttle (stator), non-iso lated

M IM iso lated platform (flo tor) X A xis2 H ertz C utoff

Data filtered by a 100 Hz low-pass filter and sampled at 1000 samples per second

F lo to r X A c c e le r a t io n

0 5 1 0 1 5 2 0 2 5 3 0

0

2 5

5 0

T im e (S e c o n d s )

Acc

eler

atio

n (µ

g)

2 H e r tz C u to ffM e a n R e m o v e d

-2 5

-5 0

Scale=60 times



MIM-2 Summary for STS-85

Data filtered by a 100 Hz low-pass filter and sampled at 1000 samples per second

0.1 1 10 100 1 .1031.10 4

1 .10 30.010.1

110

1001 .1031 .1041 .1051 .1061 .107

Frequency (Hz)

psd

(µg2

/Hz)

Power Spectral Densities for Stator and Flotor Z Accelerations

Stator

Flotor 0.3 Hertz Cutoff

0.1 1 10 100 1 .10350

40

30

20

10

0

10

Frequency (Hz)

Gai

n (d

B)

Transfer Function Between Stator and Flotor Z Accelerations

Model

Actual

0.3 Hertz Cutoff



MIM-2 summary for STS-85

• MIM has shown the capability to isolate down to 0.3 Hertz with that limit related to the PSD case material

• Models indicate that with current umbilical and replacement of PSDs, isolation cutoff frequencies of approximately 0.04 Hertz can be achieved

• To reach 0.01 Hertz, improvements to the umbilical are required



Fluid Core Element (FCE) MVIS Electronic Unit

FCE / ISPR Mounted Items

MVIS EU Box

MVIS: MicrogravityVibration Isolation System



MVIS Hardware



0.01 0.1 1 10 100 1 .103100

90

80

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10

Simulation ResultsTheoretical

Frequency [Hz]

Isol

atio

n Tr

ansf

er F

unct

ion

Gai

nPredicted Isolation Transfer Function



0.01 0.1 1 10 100 1 .1030.01

0.1

1

10

100

1 .1031 .1041 .1051 .106

1 .1071 .1081 .109

DAC6 Predicted Acceleration for Non-Isolated RackISS Acceleration Specification - Achieved Only With IsolationFCE Acceleration with MVIS

FSL Acceleration Environment

Frequency (Hz)

Pow

er S

pect

ral D

ensi

ty (m

icro

g^2/

Hz)

Isolation Performance Predicted for MVIS



MIM Base Unit Configuration

Water Cooled Shroud

MIMBU

51.59 cm(20.312”) 4

6.04 c

m

(18.12

5”)

55.5 cm(21.882”)

The water Quick Disconnect(QD), though not shown on this drawing, is part of the shroudand will be located at the lowerright or left front corner of the shroud (see 6.2.3.5).



MIM Base Unit: Two Stage Isolation to Allow Investigation of G-Jitter Effects



MIM Base Unit

Intermediate Flotor

Top Flotor

Base



MIM Base Unit Isolation Performance

1 .10 3 0.01 0.1 1 10 100100

50

0

One StageTwo Stage-3 dB Natural Isolation one-stageNatural Isolation two-stage

Isolation TF

Frequency [Hz]

TF G

ain

[dB

]



MIM Base Unit:Driven Accelerations on Top Flotor



Reaction Force to ISS in Driven Mode Operation



Schedule

MVIS is currently being manufactured• FCE mounted component were delivery to ESA in early

November for vibration testing

• Flight harness will be delivered to ESA in December

• Remaining flight hardware to be delivered to ESA by mid 2003

MIMBU configuration is complete• Work is on hold until MVIS is completed

• Launch is expected in 2005



• Rack-level Isolation System• Developed by Boeing• Flown on RME 1313 / MIR Spacehab STS-79, August 1996

• Over 1700 test runs for Isolation Characterization Experiment completed since June 2001

• Planned Utilization:• EXPRESS Racks• Fluid Combustion Facility• Materials Science Research Facility

The Active Rack Isolation System (ARIS)



• Dua l P roce s s or : De couplingimple me nte d in controlle r a llowsfre e dom to pla ce a ctua tors a nds e ns ors . P a yloa ds ha ve e xte ns ivecomma nd, da ta a cquis ition, a ndcontrol options .

• 3 S e ns or Ele ctronic Units :P rogra mma ble a na log filte rs & ga ins& 16 bit a na log-to-digita l conve rte rs .

• Acce le rome te r He a ds : Built s ma ll tofit in ra ck corne rs . 2 Tri-a xia l(Bottom), 1 Bi-a xia l (Top)

• 8 Actua tor Drive rs : P uls e widthmodula tion us e d to re duce powe rcons umption

• 8 Actua tors : Voice coil rota rya ctua tor us e d to re duce profile a ndpowe r cons umption.

• 8 P os ition S e ns ors : In te gra te d witha ctua tors .

• Ha rd s top Bumpe rs STATION UMBILICALSTANDOFF STRUCTURE

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YZ

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Boeing Active Rack Isolation System (ARIS)



ARIS-ICE Express Configuration

ICE-POP

SAMS ICU

S4



ARIS ICE 1/3-Octave Band Acceleration Measurements



ARIS ICE Isolation Performance



ARIS EXPRESS Predicted Performance at Assembly Complete



g-LIMIT A Vibration Isolation System for the Microgravity Science Glovebox

• Designed & built in-house by MSFC• Characterized as a MSG Glovebox

Investigation• Manifested for launch: LF1 Mission • 15 Days Characterization testing • Payload support operations after

characterization



g-LIMIT Flight Unit

Dimensions:~ 14” x 16” footprint~ 10” tall



Bumpers (3)

Power & InformationProcessor (PIP)

Isolator Module (IM)•Platform subsystem (TASC*)•Base subsystem (Base)•3 units

UmbilicalInterfacePlate (UIP)

Payload MountingStructure (PMS)

g-LIMIT System Assembly



g-LIMIT in MSG



Isolation Module (IM)

Electronics Boards(3)

2-AxisAccelerometer

Block

BackironActuatorPaddle

Magnets (2)



Isolator Module (IM):2 Accels

2 Posn Sensors2 Actuators

IM IM

IMInertially Isolated

PIP

Power & Information Processor (PIP):

266 MHz Pentium IIPC104 Architecture1 GB Data Storage2 PCMCIA Slots2 RS 232 slots2 RS 422 slotsVideo/Keyboard/MouseEthernet

Station Fixed

CrewLaptop

GroundStation



g-LIMIT 6DOF, Acceleration Time Response (X-axis)



• Baseline classical controllers (Jackson, Kim, Whorton)

• Fixed Order H2 / µ designs (Whorton)

• H∞ designs (Whorton)

• H2 designs (Hampton, Calhoun, Whorton)

• Interval Model Controller (Tantaris, Keel)

• Student classical designs

• Adaptive controllers (pending software update)

Controllers Technologies to be Testedusing g-LIMIT



Summary of Flight Systems Availability:

STABLE:• No current plans to fly on ISS

MIM-2, et.al.: • Use on ISS coordinated through CSA

ARIS:• In operation on ISS

g-LIMIT:• To be utilized in MSG



Further Reading:1. Grodsinsky C. and Whorton, M., “Survey of Active Vibration Isolation Systems

for Microgravity Applications,” Journal of Spacecraft and Rockets, Vol. 37, No. 5, Sept. – Oct. 2000.

2. Bushnell, G. S., and Becraft, M. D., “Microgravity Flight Characterization of an International Space Station Active Rack Isolation System,” AIAA Paper # TBD, Presented at the 2002 World Space Congress...

3. Nurre, G. S., Whorton, M. S., Kim, Y., Edberg, D. L., and Boucher, R., “Performance Assessment of the STABLE Microgravity Vibration Isolation Flight Demonstration,” submitted for publication to Journal of Spacecraft and Rockets.

4. Tryggvason, B. V., Stewart, B. Y., DeCarufel, J., and Vezina, L., "Acceleration Levels and Operation of the Microgravity Vibration Isolation Mount (MIM) on the Shuttle and Mir Space Station", AIAA Paper No. AIAA-99-0578, presented at the 37th AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, January 11-14, 1999.

5. Jackson, Kim, Whorton, “Design and Analysis of the g-LIMIT Baseline Vibration Isolation Control System,” AIAA Paper No. 2002-5019, Presented at the 2002 AIAA Guidance, Navigation, and Control Conference, Monterey, CA, August 5-8, 2002.

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Section 18 Survey of Microgravity Vibration Isolation Systems · Microgravity vibration isolation systems are required to provide an environment conducive to world-class science research

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