ACTIVE MATERIALS AND INTELLIGENT STRUCTURES

Transcription

1 ACTIVE MATERIALS AND INTELLIGENT STRUCTURES PAOLO GAUDENZI UNIVERSITA DI ROMA LA SAPIENZA PART 1 INTELLIGENT STRUCTURES: AN INTRODUCTION 1. FOREWORD 2. TRADITIONAL AND INTELLIGENT STRUCTURES 3. ACTIVE MATERIALS 4. ACTUATION MECHANISMS 5. SENSING MECHANISMS 6. CONTROL, MANUFACTURING ASPECTS 7. APPLICATION IN SPACE 8. APPLICATIONS IN OTHER ENGINEERING G FIELDS 9. COMMERCIAL APPLICATIONS 10. ONGOING RESEARCH 11. REFERENCES

2 1. FOREWORD IN RECENT YEARS MANY EFFORTS HAVE BEEN PRODUCED TOWARDS A NEW TECHNOLOGY WHICH MIGHT INFLUENCE, ALSO IN THE NEXT FUTURE, THE DEVELOPMENTS OF SCIENCE AND THE PROGRESS IN ENGINEERING PRACTICE. THE TECHNOLOGY OF ACTIVE MATERIALS AND OF INTELLIGENT (SMART) STRUCTURES AIMS AT INCORPORATING INTELLIGENCE AND LIFE FEATURES INTO THE MICROSTRUCTURE OF THE MATERIAL SYSTEM TO REDUCE MASS AND ENERGY AND PRODUCE ADAPTIVE FUNCTIONALITY. SUCH ENGINEERING SYSTEMS, WHICH SHOULD BE ABLE TO PERFORM AS THE BIOLOGICAL SYSTEMS ALREADY PRESENT IN NATURE, SHOULD BE ABLE TO OPERATE SEVERAL FUNCTIONS: SENSING, ACTUATION, CONTROL. OF COURSE THEY ALSO SHOULD BE ABLE TO RESIST EXTERNAL ACTIONS AND KEEP THEIR GEOMETRY IN THE FRAME OF ASSIGNED LIMITS.

3 1. FOREWORD (2) THE SENSORIAL AND ACTUATION CAPABILITY SHOULD BE PERFORMED BY ACTIVE MATERIALS SUCH AS PIEZOCERAMICS, SHAPE MEMORY ALLOYS OR MAGNETOREOLOGICAL FLUIDS. SUCH MATERIALS ARE ABLE TO ESTABLISH INTERACTIONS BETWEEN THE MECHANICAL FIELD AND ANOTHER FIELD OF THEIR PHYSICAL BEHAVIOR (AS THE ELECTRIC OR THE MAGNETIC ONE). BY MEANS OF THIS INTERACTIONS BOTH ACTUATION AND SENSING CAPABILITIES CAN BE STIMULATED BY MEANS OF EXTERNAL (NOT MECHANICAL) ACTIONS. THE PRESENT COURSE AIMS AT DESCRIBING AND INVESTIGATING ABOUT THESE FUNDAMENTAL MECHANISMS AND THEIR POTENTIAL APPLICATIONS IN ENGINEERING PRACTICE BY MEANS OF THE ILLUSTRATION OF EITHER THEORETICAL ANALYSES AND EXPERIMENTS PERFORMED ON MATERIALS THEMSELVES AS WELL AS ON INTELLIGENT STRUCTURES IN WHICH THE MATERIAL PLAYS THE ROLE OF THE ACTIVE PART OF THE SYSTEM.

4 1. FOREWORD (3) QUESTIONS TO BE ANSWERED AND PROBLEMS TO BE ADDRESSED: 1. WHAT ARE INTELLIGENT STRUCTURES? 2. WHY ARE THEY IMPORTANT IN ENGINEERING PRACTICE? 3. WHICH ARE THE MAIN CONSTITUENTS (ELEMENTS) OF AN INTELLIGENT STRUCTURE? 4. WHAT ABOUT POSSIBLE APPLICATIONS OF INTELLIGENT STRUCTURES IN SPACE? HAVE THEY FLOWN YET? (ABOUT ON ORBIT EXPERIMENTS) 5. WHAT ABOUT APPLICATIONS IN CIVIL, MECHANICAL OR OTHER FIELDS OF ENGINEERING? 6. ARE THERE COMMERCIAL APPLICATIONS AVAILABLE?

5 2. TRADITIONAL AND INTELLIGENT STRUCTURES 2.1 TRADITIONAL CONCEPT OF ˆSTRUCTURE CAPABILITY OF RESISTING EXTERNAL ACTIONS AND TRANSFERRING LOADS WITHOUT ATTAINING THE FAILURE OF THE MATERIAL. RESPECTING KINEMATIC AND DYNAMIC CONSTRAINTS. DESIGN, ANALYSIS, CONSTRUCTION, MAINTENANCE AND REPAIR OF A STRUCTURE ARE USUALLY VIEWED WITHIN THE ABOVE FRAME. SAFETY AND RELIABILITY, CONSIDERED VERY IMPORTANT, ARE DEALT WITH BY MEANS OF THE FACTOR OF SAFETY CONCEPT. THE ˆTRADITIONAL STRUCTURE IS USUALLY PASSIVE (SAME CONSTANT CHARACTERISTICS OF RESPONSE) AND HAS NO MEANS OF DETECTING ITS OWN STATE OR THE EXTERNAL ACTION.

6 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 MEANS OF SOME ACTUATION MECHANISM. THE MUSCLES CAN VARY THE ˆSTIFFNESS THAT THEY OFFER TO AN EXTERNAL ACTION. IN FACT THEY CAN BE STIFF OR SOFT. SENSORIALITY: CAPABILITY OF GETTING INFORMATIONS ABOUT THE VALUE 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 ALSO THE POSSIBILITY OF CREATING A CONTROL ACTION BY PUTTING TOGETHER IN AN OPTIMAL FASHION BOTH ACTUATION AND SENSING.

7 2. TRADITIONAL AND INTELLIGENT STRUCTURES (3) 2.2 INTELLIGENT STRUCTURES IN NATURE: AN EXAMPLE (2) ALSO AT A FIRST DEGREE OF APPROXIMATION A VERY DETAILED MODEL FOR SUCH MECHANISMS THAT ARE PRESENT IN OUR MUSCLES SHOULD BE SET UP. THE ROLE OF THE SKELETON AND OF THE NERVOUS SYSTEM SHOULD BE POINTED OUT. ANYWAY A HIGH LEVEL OF INTEGRATION BETWEEN ALL THE DIFFERENT CITED FUNCTIONS AND THE PART OF THE MUSCLES THAT ARE PERFORMING THEM CAN BE OBSERVED. OF COURSE OUR BODY, AS ALL LIVING SYSTEMS, TRIES TO PERFORM ITS FUNCTIONS KEEPING THE REQUESTED POWER AT THE LOWEST LEVEL POSSIBLE, IN OTHER WORDS MINIMIZING THE ENERGY. SUCH CONCEPTS LEARNT FROM NATURE COULD GIVE US VERY INTERESTING HINTS FOR MAKING MORE CLEAR THE CONCEPT OF INTELLIGENT STRUCTURE.

8 2. TRADITIONAL AND INTELLIGENT STRUCTURES (4) 2.3 INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES INTELLIGENT ADAPTIVITY SENSORIALITY STRUCTURES CONTROL AND ACTIVITY (WADA, FANSON, CRAWLEY) HIGH INTEGRATION LEVELS THEY ARE NO MORE PART OF THE SYSTEM, THEY ARE THE SYSTEM ITSELF MAIN FEATURES: AUTONOMOUS INTERACTION WITH THEIR ENVIRONMENT CHANGE OF THEIR SHAPE MONITORING THEIR OWN HEALTH VIBRATION CONTROL BEHAVE LIKE MATERIALS THEY ARE NOT MAYBE NO ARTIFICIAL INTELLIGENT STRUCTURE HAS ALREADY BEEN CONSTRUCTED. MANY PROFITS CAN HOWEVER BE FIGURED OUT JUST CONSIDERING SOME OF THOSE FEATURES AS APPLIED TO A REAL STRUCTURE.

9 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,... NATURE. ELECTRIC FIELD MAGNETIC FIELD THERMAL ENERGY LIGHT CHEMICAL ENERGY PIEZOCERAMICS PIEZOPOLYMERS ELECTROSTRICTORS ELECTRORHEOLOGICAL FL. MAGNETOSTRICTORS MAGNETORHEOL. FLUIDS SHAPE MEMORY ALLOYS SHAPE MEMORY ALLOYS SHAPE MEMORY CERAMICS SHAPE MEMORY POLYMERS SPECIAL GELS IONIC POLYMERIC GELS MECHANICAL FORCE, DISPLACEMENT COMPOSITES

10 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. ELECTRIC PIEZOCERAMICS VARIABLES PIEZOPOLYMERS (RESISTANCE, ELECTROSTRICTORS CAPACITY, ELECTRORHEOLOGICAL FL. CHARGE) MECHANICAL FORCE, DISPLACEMENT MAGNETOSTRICTORS MAGNETORHEOL. FLUIDS SHAPE MEMORY ALLOYS SHAPE MEMORY CERAMICS SHAPE MEMORY POLYMERS OPTICAL FIBERS IONIC POLYMERIC GELS COMPOSITES ELECTROMAGN. VARIABLES (RESISTANCE, INDUCTANCE) RESISTANCE LIGHT INTENSITY CONCENTRATION (Ph) FROM ANDERSON

11 4. ACTUATION MECHANISMS ACTUATION STRAIN ACTUATION STRAIN IS ALL THE STRAIN WHICH IS NOT DUE TO MECHANICAL STRESS du å: TOTAL STRAIN (IN 1D å= σ ) σ dx å= +Ë E E : MECHANICAL STRAIN TOTAL STRAIN= MECHANICAL STRAIN+ACTUATION Ë : ACTUATION STRAIN SEVERAL ORIGINS AND REASONS FOR Ë Ë = å T +å M +å P +å E +å MG +å SM +... å T : THERMAL STRAIN ε T = α ΔT å M : MOISTURE STRAIN å P : PIEZOELECTRIC STRAIN å E : ELECTROSTRICTIVE STRAIN ε P = d 31 E 3 å MG : MAGNETOSTRICTIVE STRAIN å SM : SHAPE MEMORY INDUCED STRAIN

12 4. ACTUATION MECHANISMS (2) THE CONVERSE PIEZOELECTRIC EFFECT: A SOURCE FOR ACTUATION + z COVERING ELECTRODE APPLIED FIELD E z x y DEFORMED SHAPE POLING DIRECTION PIEZOELECTRIC CAUSES DEFORMATION WHEN VOLTAGE IS APPLIED PIEZOELECTRIC STRAIN ENTERS EQUATIONS IN A MANNER SIMILAR TO THERMAL STRAIN HIGH BANDWIDTH, WELL INTO STRUCTURAL ACOUSTIC RANGE TYPICAL MATERIALS FOR STRUCTURAL APPLICATIONS: PIEZOCERAMIC PZT LEAD ZIRCONATE TITANATE Pb(Zr,Ti)O 3 POLYMER PVDF POLI VINILE FLUORIDE

13 4. ACTUATION MECHANISMS (3) INDUCED STRAIN ACTUATORS AN ACTUATOR WHICH DEVELOPS STRAIN IN RESPONSE TO A STIMULUS OTHER THAN A MECHANICAL LOAD. THE INDUCED STRAIN CAN BE DUE TO: THERMAL EXPANSION PIEZOELECTRICITY MAGNETOSTRICTION SHAPE MEMORY ALLOYS ACTUATOR EXPANDS SUBSTRATE ACTUATOR CONTRACTS THE INDUCED STRAIN IS THE MECHANISM BY WHICH INDUCED STRAIN ACTUATORS INDUCE STRAIN IN THE SUBSTRATE AND THEREFORE REALIZE CONTROL. IN THE ABOVE PICTURE A STATE OF BENDING IS PRODUCED. THE AMOUNT OF INDUCED CURVATURE IS A FUNCTION OF: BENDING STIFFNESS OF THE OVERALL STRUCTURE (DEPENDING UPON E act, E sub, t act, t sub ) ACTUATION STRAIN Ë V V

14 4. ACTUATION MECHANISMS (4) z EULER BERNOULLI BEAM MODEL t s h x GOVERNING EQUATIONS ε x (z)= ε 0 +kz σ s s x =c 11 ε x STRUCT. σ xa = c a 11(ε x -Λ) ACTUAT. l t a KINEMATICS CONSTITUTIVE RELATION INDUCED DEFORMATION MEMBRANE MODE BENDING MODE k 2 C11 ts ε 0 = Λ Ψ = 2 + Ψ a C t 11 a 1 σ(1 + ) T 2 t Λ T = 12 8 t Ψ + + S t 2 T T = s σ + a s

15 4. ACTUATION MECHANISMS (5) EULER BERNOULLI BEAM MODEL 1 kt s 0.8 2Λ NORMALIZED 0.6 CURVATURE 0.4 PIN FORCE EULER BERNOULLI t s THICKNESS T = RATIO T t a THERE IS AN OPTIMUM VALUE FOR T THAT MAXIMIZES THE INDUCED CURVATURE. BELOW THIS VALUE, AS T 0 THE THICKNESS OF THE ACTUATOR IS LARGER AND LARGER WITH RESPECT TO THE THICKNESS OF THE STRUCTURE, THE ACTUATION BENDING MOMENT INCREASES LESS RAPIDLY THAN THE OVERALL BENDING STIFFNESS OF THE STRUCTURE (SUBSTRATE+ACTUATORS). THIS EFFECT IS NOT CAPTURED BY THE PIN FORCE MODEL SINCE IT DOES NOT ACCOUNT FOR THE CONTRIBUTION OF ACTUATORS TO THE GLOBAL BENDING STIFFNESS.

16 4. ACTUATION MECHANISMS (6) TWO D AND THREE D INDUCED STRAIN ACTUATION SYSTEMS GENERIC LIFTING SURFACE CROSS SECTION A A a a PROTECTIVE COVER INDUCED STRAIN ACTUATOR ELASTIC LOAD BEARING STRUCTURE APPLICATIONS: SHAPE CONTROL OF AEROELASTIC STRUCTURES REFLECTOR OR MIRROR CONTOUR CONTROL POINTING OF PRECISION INSTRUMENTS ACOUSTICAL CTRL OF STRUCTURE BORNE NOISE KIRCHOFF LOVE LAMINATED PLATE MODEL GOVERNING FORCE AND MOMENT EQUATIONS N M = A B B ε 0 N D k M Λ Λ N = t σdz M = t σzdz N M Λ QΛdz QΛzdz Λ = t = t Q=ELASTIC COEFF.

17 4. ACTUATION MECHANISMS (7) STATIC VERSUS DYNAMIC MODELING OF INTERACTION MECHANISM DOES FREQUENCY OF ACTUATION AFFECT INDUCED FORCE OR MOMENT? DOES DENSITY OR MASS OF THE MECHANICAL SYSTEM AFFECT THE INDUCED FORCE OR MOMENT? IS STRUCTURAL DAMPING PLAYING A ROLE EITHER? THE EFFECT OF THE ACTUATOR DYNAMICS ON THE PERFORMANCE OF A CONTROLLED STRUCTURE CAN BE SUBSTANTIAL. STATIC MODELS CAN BE INSUFFICIENT FOR AN ACCURATE MODELING. k s c a M S M A c s STRUCTURE LUMPED DYNAMIC MODEL k a ACTUATOR

18 5. SENSING MECHANISMS x 3 PIEZO SENSOR SENSOR EQUATION: [ D] = [ ξ d] E T x 1 +x 1 +x 2 D 3 = ξ 3 E 3 +d 31 T 1 (SIMPLIFIED VERSION) D 3 : CHARGE DENSITY ON ELECTRODES E 3 : ELECTRIC FIELD T 1 : NORMAL STRESS ALONG x 1 (ó 11 ) ξ 3 : DIELECTRIC CONSTANT d 31 : PIEZOELECTRIC COUPLING COEFFICIENT WE MIGHT ALSO ASSUME: S 1 PIEZO S 1 (h) BEAM S 1 : NORMAL STRAIN ALONG x 1 (å 11 )

19 5. SENSING MECHANISMS (2) SENSOR EQUATION (2) FOR BENDING CASES CHARGE MEASUREMENTS D 3 = d f hw' ' S 1 (h) = -hw w: TRANSVERSE DISPLACEMENT 2 w w : CURVATURE 2 x d q(t) = x 2 31 hbw'' dx x 1 f b: WIDTH OF THE PIEZO PATCH (b=b(x)) d q(t) = f 11 x 2 31 h bw'' dx 11 x 1 q: CHARGE ON THE ELECTRODES CURRENT MEASUREMENTS q &(t) = i(t) = d f x 2 31 h bw' ' dx 11 x 1 &

20 6. CONTROL MANUFACTURING ASPECTS SINGLE CHIP MICROCOMPUTER CONTROL EXPERIMENT (CRAWLEY MIT) DATA ACQUISITION SYS. AMPL. DISTURBANCE PIEZO CONTROL PIEZO ALUMINUM BEAM FILTER AMPL. DISPLAC. SENSOR SIGNAL CONDIT. D/A SINGLE CHIP MICROCOMP. A/D CONTROL ISSUES: LUMPED OR DISTRIBUTED CONTROL STRATEGIES OPTIMAL CONTROL CHOICE OF OBJECTIVE FUNCTION CONTROL ALGORITHMS

21 6. CONTROL, MANUFACTURING ASPECTS EMBEDDING PIEZOELECTRIC SENSORS IN A COMPOSITE STRUCTURE (CRAWLEY MIT) FIBER DIRECTION SLOT FOR LEAD INSULATION KAPTON FILM PIEZOELECTRIC PIEZO LEADS ACRYLIC EPOXY LEADS STACKING SEQUENCE HOLE AND SLOTS FOR PIEZOELECTRIC AND LEADS CUT OUT OF COMPOSITE PLIES. PIEZOELECTRICS CANNOT BE INSERTED DIRECTLY INTO GRAPHITE/EPOXY WITHOUT ELECTRICALLY SHORTING THE ACTUATORS.

22 7. APPLICATION IN SPACE ADAPTIVE STRUCTURES FOR SPACE WERE DEVELOPED TO CONTROL LARGE PRECISION STRUCTURES, THEY PROVIDE POTENTIAL SOLUTIONS TO MANY OTHER CHALLANGES OF FUTURE LARGE PRECISION AND SMALL INEXPENSIVE SPACE STRUCTURES 1. ROBUST DESIGN RELAX THE CRITICALITY OF CONTROLLING AN OVERWHELMING NUMBER OF PARAMETERS BY PROVIDING A DESIGN ADJUSTABLE DURING THE MISSION TO MEET THE MISSION REQUIREMENTS 2. GROUND TESTING ALLEVIATE THE NECESSITY OF PRECISELY MEASURING THE ACCURACY OF THE STRUCTURE IN SPACE THROUGH GROUND TESTING BY PROVIDING THE CAPABILITY TO ADJUST THE STRUCTURE TO ITS REQUIREMENTS DURING ITS OPERATION IN SPACE 3. DEVELOPMENT AND SPACE CONSTRUCTION USE ACTIVE MEMBERS TO INCREASE DEPLOYMENT RELIABILITY

23 7. APPLICATION IN SPACE (2) 4. SYSTEM IDENTIFICATION RELAX THE CRITICALITY OF CONTROLLING AN OVERWHELMING NUMBER OF PARAMETERS BY PROVIDING A DESIGN ADJUSTABLE DURING THE MISSION TO MEET THE MISSION REQUIREMENTS 5. STATIC ADJUSTMENT OPTIMAL STATIC CORRECTION OF SURFACE ERRORS; OPTIMAL LOCATION OF ACTIVE MEMBERS TO CORRECT ANTICIPATED STRUCTURAL DEFORMATION. THE STRUCTURE CAN LEARN THE CHANGES WITH TIME AND ADJUST USING FEEDFORWARD APPROACHES 6. VIBRATION ATTENUATION, ISOLATION, SUPPRESION, STEERING AND POINTING (VISSP) PROVIDE A VERY QUIET ENVIRONMENT AND STEER OR POINT INSTRUMENTS MOUNTED ON A ˆNOISY AND IMPRECISELY CONTROLLED SPACE PLATFORM OR SPACECRAFT.

24 7. APPLICATION IN SPACE (3) ˆWITHIN THE PAST FEW YEARS, ADVANCEMENTS IN ADAPTIVE STRUCTURES ARE RESULTING IN FLIGHT EXPERIMENTS AND APPLICATIONS. IN ALMOST ALL ACTIVITIES, THE ADAPTIVE STRUCTURES ASPECTS OF THE FLIGHT EXPERIMENTS ARE VERY SUCCESSFUL. HAVE THEY FLOWN YET? YES! ON ORBIT EXPERIMENTS: 1.(LAWRENCE, 1990) ADDING DAMPING DAMPING WAS INCREASED IN THE DYNAMICS OF A 12 MT LONG TRUSS STRUCTURE DURING SECS OF ˆZERO GRAVITY (NEAR ZERO) AS A KC 135 AIRCRAFT PERFORMS MULTIPLE PARABOLIC TRAJECTORIES. 2.(FANSON, 1993) HUBBLE SPACE TELESCOPE REPLACEMENT OF THE WIDE FIELD PLANETARY CAMERA (WFPC 2): TO ASSURE THE PROPER ANGLE OF THE ARTICULATING FOLD MIRROR (AFM) THE CAPABILITY OF ACTIVELY ADJUSTING THE TILT POSITION OF THE AFM IN SPACE WAS ADDED. ELECTROSTRICTIVE ACTUATORS ARE THE PRIME MOVERS OF THE AFM.

25 7. APPLICATION IN SPACE (4) 3.(MILLER, 1996) MIT/NASA MACE FLEW IN THE SPACE SHUTTLE IN MARCH THE OBJECTIVE IS TO DEMONSTRATE HIGH AUTHORITY ACTIVE STRUCTURAL CONTROL OF FLEXIBLE STRUCTURES IN ZERO GRAVITY CONDITIONS BASED ON ANALYSIS, GROUND TESTING AND ON ORBITORBIT CONTROL RE DESIGN. 4.(BOUSQUET, 1995) CNES/MIR THE ˆCHARACTERIZATION OF STRUCTURES IN ORBIT (CASTOR) MET ITS OBJECTIVES OF ADDING DAMPING TO TRUSS STRUCTURES USING AXIAL ACTIVE MEMBERS. THE EXPERIMENT WAS CONDUCTED ON THE MIR STATION IN THE LATER HALF OF FROM WADA

26 8. APPLICATION IN OTHER ENGINEERING FIELDS 1. CIVIL ENGINEERING : SEISMIC ISOLATION, HEALTH MONITORED STRUCTURES (E.G. BRIDGES) 2. MECHANICAL ENGINEERING: VIBRATION REDUCTION IN GENERAL, ROBOTICS, AUTOMOTIVE APPLICATIONS, PUMPS 3. NAVAL ENGINEERING: ACOUSTIC REDUCTION (E.G. FOR SUBMARINES) 4. TELECOMUNICATIONS: SMART SKIN ANTENNAS 5. ELECTRONICS: SMART ELECTRONICS AND MEMS 6. AERONAUTICS: SMART WINGS AND BLADES (AIRPLANES AND HELICOPTERS)

27 9. COMMERCIAL APPLICATIONS (1) SMART MATERIALS HAVE ALSO A WIDE VARIETY OF COMMERCIAL APPLICATIONS: SMART SHOCK FOR MOUNTAIN BIKES OMNICOM MULTIFUNCTION TRANSDUCER (PROVIDES VIBRATION, TONE ALERT AND HANDS FREE LOUDSPEAKER FUNCTIONS IN ONE COMPONENT) SMART BASEBALL BATS PIEZOELECTRIC FLAT SPEAKER TECHNOLOGY FOR COMPUTER SYSTEMS PIEZOELECTRIC ACTUATORS FOR PNEUMATIC VALVES

28 COMMERCIAL APPLICATIONS (2) ELECTRONIC WATER SKIS (O BRIEN INTERNATIONAL) AS SEEN BELOW, THE ACX DAMPER REDUCES THE AMPLITUDE OF THE FIRST MODE VIBRATION BY ROUGHLY 30%.

29 COMMERCIAL APPLICATIONS (3) PIEZO DAMPED SKIS AND SNOWBOARDS THE ACX PIEZO CONTROL MODULE IN THE SKI IS AN ELECTRONIC SHOCK ABSORBER THAT CONVERTS MECHANICAL VIBRATION ENERGY INTO ELECTRICAL ENERGY. IT IS MADE OF PIEZOELECTRIC CERAMICS AND ELECTRONIC CONTROL CIRCUITRY (THE "BRAIN"). THE PIEZOELECTRICS DETECT UNWANTED MECHANICAL ENERGY FROM VIBRATION AND SHOCK AND INSTANTANEOUSLY CONVERT IT INTO USEFUL ELECTRICAL ENERGY. THIS ENERGY IS THEN APPLIED ACROSS A "SHUNT" CIRCUIT, WHICH DISSIPATES THE ENERGY AND REDUCES THE VIBRATION. BY DAMPING THE VIBRATIONS, PERFORMANCE AND CONTROL ARE GREATLY ENHANCED. ACX S FIRST VIBRATION CONTROL MODULE IS TARGETED AT THE FIRST VIBRATION MODE, EXPERIENCED BY MOST RECREATIONAL SKIERS K2 FOUR (#1 SELLING SKI IN THE US FOR 1996/97) $600

30 10. ONGOING RESEARCH SMART MATERIALS AND STRUCTURES INTEREST DIFFERENT FIELDS OF RESEARCH: ACTIVE NOISE CONTROL ACTIVE VIBRATION CONTROL PRECISION MACHINING AND MICROPOSITIONING AEROELASTIC CONTROL BIOMECHANICAL AND BIOMEDICAL (ARTIFICIAL MUSCLES, VALVES) PROCESS CONTROL (ON/OFF SHAPE CONTROL OF SOLAR REFLECTORS) ACTIVE DAMAGE CONTROL (DETECTION AND CONTROL OF DELAMINATION GROWTH IN COMPOSITE BEAMS) SEISMIC MITIGATION CORRECTIONS IN OPTICAL SYSTEMS DISCRETE AND DISTRIBUTED ACTUATION AND CONTROL ULTRASONIC MOTOR Generalized acoustic structure with local panel actuation

31 11. REFERENCES OF PART I 1. B.K.WADA, J.L.FANSON, E.F.CRAWLEY, ˆADAPTIVE STRUCTURES, ADAPTIVE STRUCTURES, ASME AD, VOL.15, WINTER ANNUAL MEETING, SAN FRANCISCO, CA, B. K. WADA, ˆOVERVIEW OF ADAPTIVE STRUCTURES FOR SPACE, ICAST 97, WAKIYAMA, JAPAN, OCT.29 31, 1997, PP E.F.CRAWLEY, J.DE LOUIS, ˆUSE OF PIEZOELECTRIC ACTUATORS AS ELEMENT OF INTELLIGENT STRUCTURES, AIAA, VOL.25(10), PP , 1987