INTELLIGENT STRUCTURES: AN INTRODUCTION · intelligent structures: an introduction 1. ... electrostrictive strain ... application in other engineering fields 1. civil engineering

ACTIVE MATERIALS AND INTELLIGENT STRUCTURES

PAOLO GAUDENZI

UNIVERSITA DI ROMA LA SAPIENZA

PART 1

INTELLIGENT STRUCTURES: AN INTRODUCTION1. FOREWORD2. TRADITIONAL AND INTELLIGENT STRUCTURES3 ACTIVE MATERIALS3. ACTIVE MATERIALS4. ACTUATION MECHANISMS5. SENSING MECHANISMS6. CONTROL, MANUFACTURING ASPECTS7. APPLICATION IN SPACE8 A CA O S O G G S8. APPLICATIONS IN OTHER ENGINEERING FIELDS9. COMMERCIAL APPLICATIONS10 ONGOING RESEARCH

P.GAUDENZI − ACTIVE MATERIALS AND INTELLIGENT STRUCTURES − PART 1

10. ONGOING RESEARCH11. REFERENCES

1. FOREWORD

IN RECENT YEARS MANY EFFORTS HAVE BEEN PRODUCED TOWARDS ANEW TECHNOLOGY WHICH MIGHT INFLUENCE, ALSO IN THE NEXT FUTURE,THE DEVELOPMENTS OF SCIENCE AND THE PROGRESS IN ENGINEERINGPRACTICE.

THE TECHNOLOGY OF ACTIVE MATERIALS AND OF INTELLIGENT (SMART)STRUCTURES AIMS AT INCORPORATING INTELLIGENCE AND LIFEFEATURES INTO THE MICROSTRUCTURE OF THE MATERIAL SYSTEM TOFEATURES INTO THE MICROSTRUCTURE OF THE MATERIAL SYSTEM TOREDUCE MASS AND ENERGY AND PRODUCE ADAPTIVE FUNCTIONALITY.

SUCH ENGINEERING SYSTEMS WHICH SHOULD BE ABLE TO PERFORM ASSUCH ENGINEERING SYSTEMS, WHICH SHOULD BE ABLE TO PERFORM ASTHE BIOLOGICAL SYSTEMS ALREADY PRESENT IN NATURE, SHOULD BEABLE TO OPERATE SEVERAL FUNCTIONS: SENSING, ACTUATION, CONTROL.

OF COURSE THEY ALSO SHOULD BE ABLE TO RESIST EXTERNAL ACTIONSAND KEEP THEIR GEOMETRY IN THE FRAME OF ASSIGNED LIMITS.


1. FOREWORD (2)

THE SENSORIAL AND ACTUATION CAPABILITY SHOULD BE PERFORMED BYACTIVE MATERIALS SUCH AS PIEZOCERAMICS, SHAPE MEMORY ALLOYS ORMAGNETOREOLOGICAL FLUIDS.

SUCH MATERIALS ARE ABLE TO ESTABLISH INTERACTIONS BETWEEN THEMECHANICAL FIELD AND ANOTHER FIELD OF THEIR PHYSICAL BEHAVIORMECHANICAL FIELD AND ANOTHER FIELD OF THEIR PHYSICAL BEHAVIOR(AS THE ELECTRIC OR THE MAGNETIC ONE).

BY MEANS OF THIS INTERACTIONS BOTH ACTUATION AND SENSINGBY MEANS OF THIS INTERACTIONS BOTH ACTUATION AND SENSINGCAPABILITIES CAN BE STIMULATED BY MEANS OF EXTERNAL (NOTMECHANICAL) ACTIONS.

THE PRESENT COURSE AIMS AT DESCRIBING AND INVESTIGATING ABOUTTHESE FUNDAMENTAL MECHANISMS AND THEIR POTENTIAL APPLICATIONSIN ENGINEERING PRACTICE BY MEANS OF THE ILLUSTRATION OF EITHERIN ENGINEERING PRACTICE BY MEANS OF THE ILLUSTRATION OF EITHERTHEORETICAL ANALYSES AND EXPERIMENTS PERFORMED ON MATERIALSTHEMSELVES AS WELL AS ON INTELLIGENT STRUCTURES IN WHICH THEMATERIAL PLAYS THE ROLE OF THE ACTIVE PART OF THE SYSTEM


MATERIAL PLAYS THE ROLE OF THE ACTIVE PART OF THE SYSTEM.

1. FOREWORD (3)

QUESTIONS TO BE ANSWERED AND PROBLEMS TO BEADDRESSEDADDRESSED:

1. WHAT ARE INTELLIGENT STRUCTURES?

2. WHY ARE THEY IMPORTANT IN ENGINEERING PRACTICE?

3. WHICH ARE THE MAIN CONSTITUENTS (ELEMENTS) OF ANINTELLIGENT STRUCTURE?

4. WHAT ABOUT POSSIBLE APPLICATIONS OF INTELLIGENTSTRUCTURES IN SPACE? HAVE THEY FLOWN YET? (ABOUT ONSTRUCTURES IN SPACE? HAVE THEY FLOWN YET? (ABOUT ONORBIT EXPERIMENTS)

5. WHAT ABOUT APPLICATIONS IN CIVIL, MECHANICAL OR OTHER,FIELDS OF ENGINEERING?

6. ARE THERE COMMERCIAL APPLICATIONS AVAILABLE?


2. TRADITIONAL AND INTELLIGENT STRUCTURES

2.1 TRADITIONAL CONCEPT OF ˆSTRUCTURE˜ˆSTRUCTURE˜

CAPABILITY OF RESISTING EXTERNAL ACTIONS AND TRANSFERRINGLOADS WITHOUT ATTAINING THE FAILURE OF THE MATERIAL.

RESPECTING KINEMATIC AND DYNAMIC CONSTRAINTS.

DESIGN, ANALYSIS, CONSTRUCTION, MAINTENANCE AND REPAIR OF ASTRUCTURE ARE USUALLY VIEWED WITHIN THE ABOVE FRAME.

SAFETY AND RELIABILITY, CONSIDERED VERY IMPORTANT, ARE DEALTWITH BY MEANS OF THE FACTOR OF SAFETY CONCEPT.

THE ˆTRADITIONAL˜ STRUCTURE IS USUALLY PASSIVE (SAME CONSTANTCHARACTERISTICS OF RESPONSE) AND HAS NO MEANS OF DETECTING ITSOWN STATE OR THE EXTERNAL ACTION


OWN STATE OR THE EXTERNAL ACTION.

2. TRADITIONAL AND INTELLIGENT STRUCTURES (2)

2.2 INTELLIGENT STRUCTURES IN NATURE: AN EXAMPLE

THE MUSCULAR SYSTEM OF THE HUMAN BODY HAS:

ADAPTIVITY: CAPABILITY OF MODIFYING ITS CHARACTERISTICS BY MEANSADAPTIVITY: CAPABILITY OF MODIFYING ITS CHARACTERISTICS BY MEANSOF SOME ACTUATION MECHANISM.THE MUSCLES CAN VARY THE ˆSTIFFNESS˜ THAT THEY OFFER TO ANEXTERNAL ACTION IN FACT THEY CAN BE STIFF OR SOFTEXTERNAL ACTION. IN FACT THEY CAN BE STIFF OR SOFT.

SENSORIALITY: CAPABILITY OF GETTING INFORMATIONS ABOUT THEVALUE OF THE EXTERNAL LOAD AND ITS OWN STATUS AS WELL.THE HUMAN BODY IS INDEED CAPABLE OF ESTIMATING EXTERNAL LOADS.

A RATHER COMPLICATED AND MOSTLY UNKNOWN SYSTEM PROVIDES ALSOTHE POSSIBILITY OF CREATING A CONTROL ACTION BY PUTTINGTOGETHER IN AN OPTIMAL FASHION BOTH ACTUATION AND SENSING.


TOGETHER IN AN OPTIMAL FASHION BOTH ACTUATION AND SENSING.


2.2 INTELLIGENT STRUCTURES IN NATURE: AN EXAMPLE (2)

ALSO AT A FIRST DEGREE OF APPROXIMATION A VERY DETAILED MODELFOR SUCH MECHANISMS THAT ARE PRESENT IN OUR MUSCLES SHOULD BESET UP. THE ROLE OF THE SKELETON AND OF THE NERVOUS SYSTEMSHOULD BE POINTED OUT.

ANYWAY A HIGH LEVEL OF INTEGRATION BETWEEN ALL THE DIFFERENTCITED FUNCTIONS AND THE PART OF THE MUSCLES THAT AREPERFORMING THEM CAN BE OBSERVED.

OF COURSE OUR BODY AS ALL LIVING SYSTEMS TRIES TO PERFORM ITSOF COURSE OUR BODY, AS ALL LIVING SYSTEMS, TRIES TO PERFORM ITSFUNCTIONS KEEPING THE REQUESTED POWER AT THE LOWEST LEVELPOSSIBLE, IN OTHER WORDS MINIMIZING THE ENERGY.

SUCH CONCEPTS LEARNT FROM NATURE COULD GIVE US VERYINTERESTING HINTS FOR MAKING MORE CLEAR THE CONCEPT OFINTELLIGENT STRUCTURE


INTELLIGENT STRUCTURE.


2.3 INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES

ADAPTIVITY INTELLIGENTADAPTIVITYSENSORIALITYCONTROL AND ACTIVITYHIGH INTEGRATION LEVELS

INTELLIGENTSTRUCTURES(WADA, FANSON, CRAWLEY)

HIGH INTEGRATION LEVELSTHEY ARE NO MORE PART OF THE SYSTEM, THEY ARE THE SYSTEMITSELFMAIN FEATURES:AUTONOMOUS INTERACTION WITH THEIR ENVIRONMENTCHANGE OF THEIR SHAPEMONITORING THEIR OWN HEALTHVIBRATION CONTROLBEHAVE LIKE MATERIALS THEY ARE NOTBEHAVE LIKE MATERIALS THEY ARE NOT

MAYBE NO ARTIFICIAL INTELLIGENT STRUCTURE HAS ALREADY BEENCONSTRUCTED. MANY PROFITS CAN HOWEVER BE FIGURED OUT JUST


CONSIDERING SOME OF THOSE FEATURES AS APPLIED TO A REALSTRUCTURE.

3. ACTIVE MATERIALS

ACTIVE MATERIALS ARE ABLE TO PRODUCE A MECHANICAL EFFECT BASED ON A

NON−MECHANICAL CAUSE (ACTUATION CAPABILITY). THE NON MECHANICAL

STIMULUS COULD BE OF ELECTRIC MAGNETIC THERMAL CHEMICAL NATURESTIMULUS COULD BE OF ELECTRIC, MAGNETIC, THERMAL, CHEMICAL, ... NATURE.

ELECTRIC

PIEZOCERAMICSPIEZOPOLYMERSELECTRIC

FIELDELECTROSTRICTORSELECTRORHEOLOGICAL FL.

MAGNETOSTRICTORS

MAGNETIC FIELDMAGNETOSTRICTORSMAGNETORHEOL. FLUIDSSHAPE MEMORY ALLOYS

MECHANICALFORCE,

THERMAL ENERGY

SHAPE MEMORY ALLOYSSHAPE MEMORY CERAMICSSHAPE MEMORY POLYMERS

DISPLACEMENT

LIGHT

CHEMICAL ENERGY

SPECIAL GELS

IONIC POLYMERIC GELS


CHEMICAL ENERGY

COMPOSITES

3.ACTIVE MATERIALS (2)

ACTIVE MATERIALS ARE ABLE TO PRODUCE A NON−MECHANICAL EFFECT BASED ON

A MECHANICAL CAUSE (SENSING CAPABILITY). THE NON MECHANICAL EFFECT

COULD BE OF ELECTRIC, MAGNETIC, THERMAL, CHEMICAL, ... NATURE.

PIEZOCERAMICSPIEZOPOLYMERS

ELECTRIC VARIABLES

PIEZOPOLYMERSELECTROSTRICTORSELECTRORHEOLOGICAL FL.

(RESISTANCE,CAPACITY,CHARGE)ELECTROMAGN

MECHANICALFORCE,DISPLACEMENT

MAGNETOSTRICTORSMAGNETORHEOL. FLUIDS

SHAPE MEMORY ALLOYS

ELECTROMAGN. VARIABLES (RESISTANCE, INDUCTANCE)DISPLACEMENT SHAPE MEMORY ALLOYS

SHAPE MEMORY CERAMICSSHAPE MEMORY POLYMERS

RESISTANCE

OPTICAL FIBERS

IONIC POLYMERIC GELS

LIGHT INTENSITY

CONCENTRATION(Ph)


COMPOSITES(Ph)

FROM ANDERSON

4. ACTUATION MECHANISMS

ACTUATION STRAIN

ACTUATION STRAIN IS ALL THE STRAIN WHICH IS NOT DUE TOACTUATION STRAIN IS ALL THE STRAIN WHICH IS NOT DUE TO MECHANICAL STRESS

å = + Ëdxdu

σ σå: TOTAL STRAIN (IN 1D å= )

å = + Ë

TOTAL STRAIN MECHANICAL STRAIN ACTUATION STRAIN

E E: MECHANICAL STRAIN

Ë ACTUATION STRAINTOTAL STRAIN= MECHANICAL STRAIN+ACTUATION STRAIN

SEVERAL ORIGINS AND REASONS FOR Ë

Ë : ACTUATION STRAIN

Ë = åT+åM+åP+åE+åMG+åSM+...

åT: THERMAL STRAINåM MOISTURE STRAIN

εT = α ΔTåM: MOISTURE STRAINåP: PIEZOELECTRIC STRAINåE: ELECTROSTRICTIVE STRAINåMG

εP = d31 E3


åMG: MAGNETOSTRICTIVE STRAINåSM: SHAPE MEMORY INDUCED STRAIN

4. ACTUATION MECHANISMS (2)

THE CONVERSE PIEZOELECTRIC EFFECT: A SOURCE FOR ACTUATIONz COVERING ELECTRODE

APPLIED

COVERING ELECTRODE+

POLING DIRECTION

DEFORMED SHAPE

FIELDEz

y

x

POLING DIRECTION

PIEZOELECTRIC CAUSES DEFORMATION WHEN VOLTAGE IS APPLIED

PIEZOELECTRIC STRAIN ENTERS EQUATIONS IN A MANNER SIMILAR TO

x−

PIEZOELECTRIC STRAIN ENTERS EQUATIONS IN A MANNER SIMILAR TOTHERMAL STRAIN

HIGH BANDWIDTH WELL INTO STRUCTURAL ACOUSTIC RANGEHIGH BANDWIDTH, WELL INTO STRUCTURAL ACOUSTIC RANGE

TYPICAL MATERIALS FOR STRUCTURAL APPLICATIONS:− PIEZOCERAMIC PZT LEAD ZIRCONATE TITANATE Pb(Zr,Ti)O3


( , ) 3

− POLYMER PVDF POLI VINILE FLUORIDE


INDUCED STRAIN ACTUATORSAN ACTUATOR WHICH DEVELOPS STRAIN IN RESPONSE TO A STIMULUSOTHER THAN A MECHANICAL LOAD.

− THE INDUCED STRAIN CAN BE DUE TO:THERMAL EXPANSION

ACTUATOR EXPANDS

− THERMAL EXPANSION− PIEZOELECTRICITY− MAGNETOSTRICTION

V

SUBSTRATE

− SHAPE MEMORY ALLOYS

THE INDUCED STRAIN IS THE MECHANISM BY WHICH INDUCED STRAINACTUATORS INDUCE STRAIN IN THE SUBSTRATE AND THEREFORE

ACTUATOR CONTRACTSV

ACTUATORS INDUCE STRAIN IN THE SUBSTRATE AND THEREFOREREALIZE CONTROL.

IN THE ABOVE PICTURE A STATE OF BENDING IS PRODUCED THEIN THE ABOVE PICTURE A STATE OF BENDING IS PRODUCED. THEAMOUNT OF INDUCED CURVATURE IS A FUNCTION OF:− BENDING STIFFNESS OF THE OVERALL STRUCTURE (DEPENDING UPON

E E t t )


Eact, Esub, tact, tsub)− ACTUATION STRAIN Ë


EULER BERNOULLI BEAM MODEL x

z

EULER BERNOULLI BEAM MODEL

GOVERNING EQUATIONS

x

l

h

ta

ts

KINEMATICS

CONSTITUTIVE RELATION

εx(z)= ε0+kz

σ s=cs ε STRUCT

GOVERNING EQUATIONS l

CONSTITUTIVE RELATIONσx =c 11 εx STRUCT.

σxa= ca

11(εx-Λ) ACTUAT.

INDUCED DEFORMATION

MEMBRANE MODE ΛΨ2

2ε0 += s

a

s11

tt

CC

Ψ =

BENDING MODE

Ψ2 + a11 tC

Λt2

812

)T1

1(σk

+= s

tt

T =


BENDING MODE tT8

T12Ψσ S

2+++ at


EULER BERNOULLI BEAM MODEL

0.8

1

Λ2kts

NORMALIZED CURVATURE 0.4

0.6

0.8

PIN FORCE

EULERBERNOULLI

Λ2

THICKNESS RATIO T0

0.2

0 5 10 15 20

BERNOULLI

s

tt

T =

THERE IS AN OPTIMUM VALUE FOR T THAT MAXIMIZES THE INDUCEDCURVATURE. BELOW THIS VALUE, AS T 0 THE THICKNESS OF THE

THICKN SS RATIO T0 5 10 15 20at

ACTUATOR IS LARGER AND LARGER WITH RESPECT TO THE THICKNESS OFTHE STRUCTURE, THE ACTUATION BENDING MOMENT INCREASES LESSRAPIDLY THAN THE OVERALL BENDING STIFFNESS OF THE STRUCTURE(SUBSTRATE+ACTUATORS).

THIS EFFECT IS NOT CAPTURED BY THE PIN−FORCE MODEL SINCE IT DOESNOT ACCOUNT FOR THE CONTRIBUTION OF ACTUATORS TO THE GLOBAL


NOT ACCOUNT FOR THE CONTRIBUTION OF ACTUATORS TO THE GLOBALBENDING STIFFNESS.


TWO−D AND THREE−D INDUCED STRAIN ACTUATION SYSTEMS GENERIC LIFTING SURFACE

a aCROSS−SECTION A−A

a a

PROTECTIVE COVERINDUCED STRAIN ACTUATORELASTIC LOAD BEARING STRUCTURE

APPLICATIONS: SHAPE CONTROL OF AEROELASTIC STRUCTURESREFLECTOR OR MIRROR CONTOUR CONTROLPOINTING OF PRECISION INSTRUMENTSACOUSTICAL CTRL OF STRUCTURE BORNE NOISE

KIRCHOFF−LOVE LAMINATED PLATE MODEL

GOVERNING FORCE AND MOMENT EQUATIONS

⎥⎤

⎢⎡

−⎥⎤

⎢⎡⎥⎤

⎢⎡

=⎥⎤

⎢⎡

Λ0NεBAN ∫= t dzσN ∫= tΛ dzΛQN

dQQ=ELASTIC

COEFF


⎥⎦

⎢⎣

⎥⎦⎢⎣⎥⎦⎢⎣⎥⎦

⎢⎣ Λ

MkDBM ∫= t zdzσM ∫= tΛ zdzΛQM COEFF.


STATIC VERSUS DYNAMIC MODELING OF INTERACTION MECHANISM

DOES FREQUENCY OF ACTUATION AFFECT INDUCED FORCE OR MOMENT?DOES FREQUENCY OF ACTUATION AFFECT INDUCED FORCE OR MOMENT?

DOES DENSITY OR MASS OF THE MECHANICAL SYSTEM AFFECT THEINDUCED FORCE OR MOMENT?INDUCED FORCE OR MOMENT?

IS STRUCTURAL DAMPING PLAYING A ROLE EITHER?

THE EFFECT OF THE ACTUATOR DYNAMICS ON THE PERFORMANCE OF ATHE EFFECT OF THE ACTUATOR DYNAMICS ON THE PERFORMANCE OF ACONTROLLED STRUCTURE CAN BE SUBSTANTIAL. STATIC MODELS CAN BEINSUFFICIENT FOR AN ACCURATE MODELING.

MAMS

ks

ca

⊄

STRUCTURE ACTUATOR

kacs


LUMPED DYNAMIC MODEL

STRUCTURE ACTUATOR

5. SENSING MECHANISMS

PIEZO SENSORx3

SENSOR EQUATION: [ ] [ ]⎭⎬⎫

⎩⎨⎧

=TE

dξDx1

D ξ E +d T (SIMPLIFIED VERSION)

+x1 +x2

D3= ξ3E3+d31T1 (SIMPLIFIED VERSION)

D3: CHARGE DENSITY ON ELECTRODESE3: ELECTRIC FIELDE3: ELECTRIC FIELDT1: NORMAL STRESS ALONG x1 (ó11)ξ3: DIELECTRIC CONSTANTd : PIEZOELECTRIC COUPLING COEFFICIENTd31: PIEZOELECTRIC COUPLING COEFFICIENT

WE MIGHT ALSO ASSUME:

S S (h)


S1 PIEZO ≅ S1(h)BEAMS1: NORMAL STRAIN ALONG x1 (å11)

5. SENSING MECHANISMS (2)

SENSOR EQUATION (2)

FOR BENDING CASES S1(h) = -hw”CHARGE MEASUREMENTS

w: TRANSVERSE DISPLACEMENTd w: TRANSVERSE DISPLACEMENT

w˜: CURVATURE 2

2

xw

∂∂

d

''hwfd

D11

313 −=

dx''hbwfd

)t(q 2

1

x

x11

31∫ −= b: WIDTH OF THE PIEZO PATCH (b=b(x))

q: CHARGE ON THE ELECTRODESd q: CHARGE ON THE ELECTRODES∫−= 2

1

x

x11

31 dx''bwhfd

)t(q

CURRENT MEASUREMENTS ∫−== 2

1

x

x11

31 dx''wbhfd

)t(i)t(q &&


6. CONTROL MANUFACTURING ASPECTS

SINGLE−CHIP MICROCOMPUTER CONTROL EXPERIMENT (CRAWLEY−MIT)

AMPL.

DATA ACQUISITION SYS.

DISTURBANCE PIEZO

CONTROL PIEZOCONTROL PIEZO

ALUMINUM BEAM

SIGNAL CONDIT.

FILTER

AMPL.DISPLAC. SENSOR

D/ASINGLE CHIP MICROCOMP. A/D

CONTROL ISSUES:LUMPED OR DISTRIBUTED CONTROL STRATEGIESOPTIMAL CONTROL−CHOICE OF OBJECTIVE FUNCTION


CONTROL ALGORITHMS

6. CONTROL, MANUFACTURING ASPECTS

EMBEDDING PIEZOELECTRIC SENSORS IN A COMPOSITE STRUCTURE(CRAWLEY−MIT)

SLOT FOR LEAD

KAPTON FILM PIEZOELECTRIC

INSULATIONFIBER

DIRECTION

KAPTON FILM PIEZOELECTRIC

PIEZO LEADS

ACRYLIC EPOXY LEADS

HOLE AND SLOTS FOR PIEZOELECTRIC AND LEADS CUT OUT OF

STACKING SEQUENCE

HOLE AND SLOTS FOR PIEZOELECTRIC AND LEADS CUT OUT OFCOMPOSITE PLIES.

PIEZOELECTRICS CANNOT BE INSERTED DIRECTLY INTO GRAPHITE/EPOXY


PIEZOELECTRICS CANNOT BE INSERTED DIRECTLY INTO GRAPHITE/EPOXYWITHOUT ELECTRICALLY SHORTING THE ACTUATORS.

7. APPLICATION IN SPACE

ADAPTIVE STRUCTURES FOR SPACE WERE DEVELOPED TO CONTROLLARGE PRECISION STRUCTURES, THEY PROVIDE POTENTIAL SOLUTIONS TOMANY OTHER CHALLANGES OF FUTURE LARGE PRECISION AND SMALLINEXPENSIVE SPACE STRUCTURES

1 ROBUST DESIGN1. ROBUST DESIGNRELAX THE CRITICALITY OF CONTROLLING AN OVERWHELMING NUMBEROF PARAMETERS BY PROVIDING A DESIGN ADJUSTABLE DURING THEMISSION TO MEET THE MISSION REQUIREMENTS

2. GROUND TESTINGSS S SALLEVIATE THE NECESSITY OF PRECISELY MEASURING THE ACCURACY OF

THE STRUCTURE IN SPACE THROUGH GROUND TESTING BY PROVIDING THECAPABILITY TO ADJUST THE STRUCTURE TO ITS REQUIREMENTS DURINGITS OPERATION IN SPACE

3. DEVELOPMENT AND SPACE CONSTRUCTION


USE ACTIVE MEMBERS TO INCREASE DEPLOYMENT RELIABILITY

7. APPLICATION IN SPACE (2)

4. SYSTEM IDENTIFICATIONRELAX THE CRITICALITY OF CONTROLLING AN OVERWHELMING NUMBEROF PARAMETERS BY PROVIDING A DESIGN ADJUSTABLE DURING THEMISSION TO MEET THE MISSION REQUIREMENTS

5 STATIC ADJUSTMENT5. STATIC ADJUSTMENTOPTIMAL STATIC CORRECTION OF SURFACE ERRORS; OPTIMAL LOCATIONOF ACTIVE MEMBERS TO CORRECT ANTICIPATED STRUCTURALDEFORMATION. THE STRUCTURE CAN LEARN THE CHANGES WITH TIMEAND ADJUST USING FEEDFORWARD APPROACHES

6. VIBRATION ATTENUATION, ISOLATION, SUPPRESION, STEERING ANDPOINTING (VISSP)PROVIDE A VERY QUIET ENVIRONMENT AND STEER OR POINTPROVIDE A VERY QUIET ENVIRONMENT AND STEER OR POINTINSTRUMENTS MOUNTED ON A ˆNOISY AND IMPRECISELY CONTROLLED˜SPACE PLATFORM OR SPACECRAFT.



ˆWITHIN THE PAST FEW YEARS, ADVANCEMENTS IN ADAPTIVESTRUCTURES ARE RESULTING IN FLIGHT EXPERIMENTS ANDAPPLICATIONS. IN ALMOST ALL ACTIVITIES, THE ADAPTIVE STRUCTURESASPECTS OF THE FLIGHT EXPERIMENTS ARE VERY SUCCESSFUL.˜

HAVE THEY FLOWN YET? YES! ON ORBIT EXPERIMENTSHAVE THEY FLOWN YET? YES! ON ORBIT EXPERIMENTS:

1.(LAWRENCE, 1990) ADDING DAMPINGDAMPING WAS INCREASED IN THE DYNAMICS OF A 12 MT LONG TRUSSDAMPING WAS INCREASED IN THE DYNAMICS OF A 12 MT LONG TRUSSSTRUCTURE DURING 15−20 SECS OF ˆZERO˜ GRAVITY (NEAR ZERO) AS AKC−135 AIRCRAFT PERFORMS MULTIPLE PARABOLIC TRAJECTORIES.

2.(FANSON, 1993) HUBBLE SPACE TELESCOPEREPLACEMENT OF THE WIDE FIELD PLANETARY CAMERA (WFPC−2): TOASSURE THE PROPER ANGLE OF THE ARTICULATING FOLD MIRROR (AFM)ASSURE THE PROPER ANGLE OF THE ARTICULATING FOLD MIRROR (AFM)THE CAPABILITY OF ACTIVELY ADJUSTING THE TILT POSITION OF THEAFM IN SPACE WAS ADDED. ELECTROSTRICTIVE ACTUATORS ARE THE


PRIME MOVERS OF THE AFM.


3.(MILLER, 1996) MIT/NASA MACEFLEW IN THE SPACE SHUTTLE IN MARCH 1995 THE OBJECTIVE IS TOFLEW IN THE SPACE SHUTTLE IN MARCH 1995. THE OBJECTIVE IS TODEMONSTRATE HIGH AUTHORITY ACTIVE STRUCTURAL CONTROL OFFLEXIBLE STRUCTURES IN ZERO GRAVITY CONDITIONS BASED ONANALYSIS GROUND TESTING AND ON ORBIT CONTROL RE DESIGNANALYSIS, GROUND TESTING AND ON−ORBIT CONTROL RE−DESIGN.

4.(BOUSQUET, 1995) CNES/MIRTHE ˆCHARACTERIZATION OF STRUCTURES IN ORBIT˜ (CASTOR) MET ITSOBJECTIVES OF ADDING DAMPING TO TRUSS STRUCTURES USING AXIALACTIVE MEMBERS. THE EXPERIMENT WAS CONDUCTED ON THE MIRSTATION IN THE LATER HALF OF 1996.

FROM WADA


8. APPLICATION IN OTHER ENGINEERING FIELDS

1. CIVIL ENGINEERING : SEISMIC ISOLATION, HEALTHMONITORED STRUCTURES (E G BRIDGES)MONITORED STRUCTURES (E.G. BRIDGES)

2. MECHANICAL ENGINEERING: VIBRATION REDUCTION INGENERAL ROBOTICS AUTOMOTIVE APPLICATIONS PUMPSGENERAL, ROBOTICS, AUTOMOTIVE APPLICATIONS, PUMPS

3. NAVAL ENGINEERING: ACOUSTIC REDUCTION (E.G. FORSUBMARINES)SUBMARINES)

4. TELECOMUNICATIONS: SMART SKIN ANTENNAS

5. ELECTRONICS: SMART ELECTRONICS AND MEMS

6 AERONAUTICS: SMART WINGS AND BLADES (AIRPLANES6. AERONAUTICS: SMART WINGS AND BLADES (AIRPLANESAND HELICOPTERS)


9. COMMERCIAL APPLICATIONS (1)

SMART MATERIALS HAVE ALSO A WIDE VARIETY OF COMMERCIAL APPLICATIONS:

− SMART−SHOCK FOR MOUNTAIN BIKES

− OMNICOM MULTIFUNCTION TRANSDUCEROMNICOM MULTIFUNCTION TRANSDUCER(PROVIDES VIBRATION, TONE ALERT

AND HANDS−FREE LOUDSPEAKER FUNCTIONS IN ONE COMPONENT)

− SMART BASEBALL BATS

FUNCTIONS IN ONE COMPONENT)

− PIEZOELECTRIC FLAT SPEAKER TECHNOLOGY FOR COMPUTER SYSTEMS

PIEZOELECTRIC ACTUATORS FOR PNEUMATIC VALVES


− PIEZOELECTRIC ACTUATORS FOR PNEUMATIC VALVES

COMMERCIAL APPLICATIONS (2)

− ELECTRONIC WATER−SKIS

(O’BRIEN INTERNATIONAL)(O’BRIEN INTERNATIONAL)

AS SEEN BELOW, THE ACX DAMPER REDUCES THE AMPLITUDE OFTHE FIRST MODE VIBRATION BY ROUGHLY 30%.


COMMERCIAL APPLICATIONS (3)

− PIEZO−DAMPED SKIS AND SNOWBOARDSTHE ACX PIEZO CONTROL MODULE IN THE SKI IS AN ELECTRONIC SHOCKABSORBER THAT CONVERTS MECHANICAL VIBRATION ENERGY INTOABSORBER THAT CONVERTS MECHANICAL VIBRATION ENERGY INTOELECTRICAL ENERGY. IT IS MADE OF PIEZOELECTRIC CERAMICS ANDELECTRONIC CONTROL CIRCUITRY (THE "BRAIN"). THE PIEZOELECTRICSDETECT UNWANTED MECHANICAL ENERGY FROM VIBRATION AND SHOCK ANDINSTANTANEOUSLY CONVERT IT INTO USEFUL ELECTRICAL ENERGY. THISENERGY IS THEN APPLIED ACROSS A "SHUNT" CIRCUIT, WHICH DISSIPATESTHE ENERGY AND REDUCES THE VIBRATION. BY DAMPING THE VIBRATIONS,PERFORMANCE AND CONTROL ARE GREATLY ENHANCED.

ACX’S FIRST VIBRATIONCONTROL MODULE ISCONTROL MODULE ISTARGETED AT THEFIRST VIBRATION MODE,EXPERIENCED BY MOSTTRECREATIONAL SKIERS


K2 FOUR (#1 SELLING SKI IN THE US FOR 1996/97) $600

10. ONGOING RESEARCH

SMART MATERIALS AND STRUCTURES INTEREST DIFFERENT FIELDS OF RESEARCH:

− ACTIVE NOISE CONTROLGeneralized acoustic structure with local

− ACTIVE VIBRATION CONTROL

− PRECISION MACHINING AND MICROPOSITIONING

panel actuation

− AEROELASTIC CONTROL

− BIOMECHANICAL AND BIOMEDICAL (ARTIFICIAL MUSCLES, VALVES)

− PROCESS CONTROL(ON/OFF SHAPE CONTROL OF SOLAR REFLECTORS)

ACTIVE DAMAGE CONTROL− ACTIVE DAMAGE CONTROL(DETECTION AND CONTROL OF DELAMINATION GROWTH INCOMPOSITE BEAMS)

SEISMIC MITIGATION− SEISMIC MITIGATION

− CORRECTIONS IN OPTICAL SYSTEMS

− DISCRETE AND DISTRIBUTED ACTUATION AND CONTROL


− ULTRASONIC MOTOR

11. REFERENCES OF PART I

1. B.K.WADA, J.L.FANSON, E.F.CRAWLEY, ÂDAPTIVE STRUCTURES˜,ADAPTIVE STRUCTURES ASME AD VOL 15 WINTER ANNUAL MEETING SANADAPTIVE STRUCTURES, ASME AD, VOL.15, WINTER ANNUAL MEETING, SANFRANCISCO, CA, 1989

2 B K WADA ÔVERVIEW OF ADAPTIVE STRUCTURES FOR SPACE˜ ICAST2. B. K. WADA, ÔVERVIEW OF ADAPTIVE STRUCTURES FOR SPACE˜, ICAST97, WAKIYAMA, JAPAN, OCT.29−31, 1997, PP.16−26

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