1day piezo training 2010

Overview on piezoelectric actuators, mechanisms & motors with their related driving electronics:

Technology & Applications

04/06/2010 1 Day Piezo Training 2010 2

Topics overview

1 / Piezo materials for actuators

1.1/ Piezo theory & properties

1.2/ Multilayer ceramic 1.2.1 /current properties, trends, perspectives,1.2.2 / Reliability aspects,

2 / Piezo actuators & mechanisms

2.1/ Internally & externally leveraged piezo actuators,2.2/ Piezo mechanisms,

3 / Driving and control of piezo actuators

3.1 / Basic of amplifiers 3.2 / Static & Dynamic conditions

4 / How to choose an actuator & its related electronics ?

4.1 Exercises

4.2 Demonstration

5/ Piezomotors5.1 / Inchworm and Inertial step motors5.2 / Resonant structure

5.2.1 / example of motors5.2.1 / modelling techniques

5.3 / Tribology of piezo motors5.4 / Driving of piezo motors

6 / Applications & references


Piezoelectricity Theory & Properties


Piezoelectricity : an overview

Materials aspectsEquationsMaterials constantsTechnological aspectsIllustrative exampleElectromechanical analogy

Piezo electric ceramics & magnetostrictive alloys


Various effects in materials

Charge current Magnetisation Strain Temperature Light

Electrical field

Permittivity Conductivity

Elec-mag effect

Inverse piezo effect

Elec. Caloric effect

Elec. Optic effect

Magnetic field

Mag-electric effect

Permeability Magneto-striction

Mag.caloric effect

Mag.optic effect

Stress Direct Piezo-electric effect

Direct Piezo-magnetic effect (biased mat.)

Elastic constant

_ Photoelastic effect

Heat Pyroelectric effect

_ Thermal expansion

Specific heat

_

Light Photovoltaic effect

_ Photostriction _ Refractive effect

"Smart" materials refer to materials having a non - diagonal effect (sensing or actuating functions).


Active strains of active materials

Applying a field (E or H) on an free sample, it deformsSmall deformation in the elastic domainStrain = relative expansion : S = δL / L

Expansion = positive strain / Contraction = negative strainsUnits : ppm= 10-6 or % = 10-2

Typical active free strains are S= 1000ppm = 0.1%Stroke : u = δL = S . L

Example : L = 100mm, S = 1000ppm => u = δL = 0.1mm = 100µm

L δL

E


Active stress of active materials

Blocked Stress of active materialsStress = force par unit of surface : T = - F / A

Compression is positive stress ; Traction is negative stressUnits : MPa = N /mm2

Typical active blocked stresses are T= 20MPa = 20 N /mm2

Ex. A = 1cm² ; T = 20MPa => F = 2000N = 2kN

Stress from electromagnets T = B²/2µo = 0.4 MPa with B=1T

A- F F


Active materials properties

Active materials offer small strains (ie small displacement) & high forces density compared with electromagnetic actuators

Field E Field / H Field

Strain Stress Young’s modulus

Coupling factor

Relative permitivity / permeability

Curie temp.

Density

E (MV/m) H (MA/m)

(ppm) (MPa) (Gpa) (%) - (°C) (kg/m3)

Piezo-electrics Bulk

PZT - 7 E +- 0.5 +- 70 +- 5 72 67 425 350 7.7

Bulk PZT - 4

E + - 0.5 +- 150 +- 10 66 70 1300 325 7.6

Bulk PZT - 5

E +- 0.5 +- 300 +- 15 48 75 3400 195 7.5

MLA E +- 2.6 + 1 250 + 40 30 70 2100 180 8.0 Magnetostrictives

Terfenol-D H + 0.16 + 1 800 + 50 25 70 4 380 9.1 Mag. Shape Mem.

NiMnGa H + 0.5 + 60 000 (6%)

+ 2


Piezoelectric effects

Piezoelectric material = non centro-symmetric crystal belowthe Curie temperature

Direct effect: sensing Inverse effect: actuation

Courtesy of APC

D ~ d T S ~ d Ed: piezo coefficient E: Electrical fieldS: Strain; D: Electric displacementT: Stress


Pyroelectricity & Electrostriction

Pyroelectric material = piezoelectric + polar material=> ∆P = p ∆T

P: Polarisation; T: Temperature; p: pyroelectric coefficient

Pure electrostrictive material = non piezoelectric material=> S = M E2 = Q P2

M & Q: cofficients of electrostriction; S: strain; E: electric field

Pyroelectricity & electrostriction are disturbing effects on piezoelectric response

Actually, piezo strain combines all effects in a more or lessextend :

S = d E + M E2 + α ∆T


Ferroelectric materials

PZT “lead Titanium –Zirconate”:Ferroelectric material under the Curie temperature.A poling process gives the material its remanent polarization. During the

poling process, the material is subjected to a high electric field at the Curie temperature.

If the material is subjected to a temperature that is greater than its Curie point, it’s no longer piezoelectric but it can be repoled again in some conditions.

Std 80°C but 150°C on request


Ferroelectric materials

Origin of poling in ferroelectric materials :Crystal structure, + & - charge centres may not coincide, even if

E = 0.Ferroelectric = material whose direction of poling can be reversed

by an electric field.

Characteristic of a ferroelectric material : high relative permittivity

D E P ED electric displacementP polarization

relative permittivity

= + =ε ε ε

ε

0 0.: ,: ,:


Interpretation of poling in PZT crystal structures

Perovskite structure in PZTDifferent shapes of the crystal structure

Courtesy of Tokin

Sub solidus phase diagram of PZT Ceramics(B. Noheda & al)


Intrinsic / Extrinsic piezoelectricity

Intrinsic piezoelectric effect : strain of the crystal lattice

Extrinsic piezoelectric effect : domain reorientation

=> Hysteresis


Hysteresis butterfly cycle

Courtesy of Tokin Repoling process in the domains


Piezo ceramic vs Single Crystal

PZT Piezo ceramicsIndustrial materials produced by sintering of powderCompatible with multilayer technique to get low voltagesLinear strain response

Single crystalsNew material obtained by crystal growthLarge strains with large E-fieldNot compatible with multilayer so need large voltagesNon linear (electrostrictivecontribution)


Piezo ceramics : Manufacturing process of bulk materials

Mixing oxyde powders Zr02, Ti02, PbO, with a binderSintering at high temperature (1200°C),Cutting & Grinding at the correct size,External electrodes deposition (Screen printing, PVD, …)Poling operation :

room temp. / 2 kV/mm for soft - type,120°C, 5 kV/mm, in oil for hard type.


General constitutive law of piezoelectric body

No electrostriction & pyroelectric effectsChoosing T and E as independent variables

S s T d E

D d T E

En n

m m mnT

n

α αβ β α

β β ε

= +

= +α β, , . . . ,

, , ,==

1 61 2 3m n

sE : Compliances at constant fieldd : Piezoelectric strains per unit of fieldeT : Permittivity at constant stress

S : Strain T : Stress D : Induction E : Field

1

2

3

P4

6

5


Constitutive law of PZT ceramicsPTZ ceramic : 6 mm class

SSSSSS

DDD

s s s d

s s s d

s s s d

s d

s d

s

d

d

E E E

E E E

E E E

E

E

E

T

1

2

3

4

5

6

1

2

3

11 12 13 31

12 11 13 31

13 13 33 33

44 15

44 15

66

15 11

15

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0 0 0

0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0

0 0 0 0

⎡

⎣

⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢

⎤

⎦

⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥

+

ε

0 0 0

0 0 0 0 011

31 31 33 33

1

2

3

4

5

6

1

2

3ε

ε

T

Td d d

TTTTTT

EEE

⎡

⎣

⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢

⎤

⎦

⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥

⎡

⎣

⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢

⎤

⎦

⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥

.=


Electromechanical coupling effect

Materials show 3 coupled deformation due to non-zero coefficients d33 d31 d15

1

2

3

P4

6

5

In static : S3=d33 E3

31 : Transverse mode 15 : Shear mode33 : Longitudinal modeIn static : S1=d31 E3 In static : S5=d15 E1



Materials properties are characterised by intrinsic coupling coefficients

Longitudinal coupling factor k33

Transverse coupling factor k31

Shear coupling factor k15

k332 = d33

2 / s33E ε33

T

k312 = d31

2 / s11E ε33

T

k152 = d15

2 / s44E ε11

T



Meaning of the coupling coefficient: Coupled energies in a usual magnetic transformer

U12 = Mutual Energy U1 = Energy in the Primary U2 = Energy in the Secondary

Transformer coupling factor

In an electromechanical deviceUem = Mutual Electromecanical Energy Ue = Electrical EnergyUm = Mecanical Energy

kem2 = Uem

2 / Ue .Um

k2 = U122 / U1 .U2


Physical properties of piezo materials

Courtesy of Nava Seter (ABC of piezoelectricity, Interlaken conference, feb. 2002)


Constitutive law of PZT ceramics

Simplification for a length - expansion mode (33-mode)

T T T T T S S SE E D D

1 2 4 5 6 4 5 6

1 2 1 2

0 00 0

= = = = = = = == = = =

;;

S S s T d E

S s T d E

D d T E

E

E

T

1 2 13 3 31 3

3 33 3 33 3

3 33 3 33 3

= = +

= +

= +

.

.

. ε

3


Laws of Piezo actuators

Simplification for a length - expansion bar (33-mode)A : active area L : active length

∆u u u L SF A TV L EQ A D

= − == −==

2 1 3

3

3

3

..

..

A

L

+ V0 0

U 2U 1

{k A s L

N d k

C A L

E E

E

T T

=

=

=

/

.

. /

33

33

33ε

VCFkNQ

VkNF

ku

TE

EE

..

..1

+−=

+−=∆


Laws of Piezo actuatorsSimplification for a length - expansion bar (33-mode)

A

L

+ V0 0

U 2U 1

{

∆uk

FNk

V

QNk

F C V

E E

T

= − +

= − +

1. .

. .

S S s T d E

S s T d E

D d T E

E

E

T

1 2 1 3 3 3 1 3

3 3 3 3 3 3 3

3 3 3 3 3 3 3

= = +

= +

= +

.

.

. ε

k332 = d33

2 / s33E ε33

T = N2/kE.CT



kN

C kC C k

eff T E

s Teff

22

21

=

= −( )

VCuNQVNukF

S

E

...

+∆=

+∆−=F

NVk

u

NV

Generalisation



Generalisation – Characteristic curve of a piezo actuator

NV = Max Force without displacement @ V

If V = Vmax = 150 V => Max Force = Blocked Force (Fb)

∆ u max = NV/K = Max Displacement @ V

If V = Vmax = 150 V => ∆ u max is the max stroke

∆u = (NV-F)/K∆ u max

Fb

V=50V

V=150V

Slope 1/K = elasticity

Stroke

Force


Additional effects in static applications

Hysteresis:



Creep effect:

Actuator's displacement (µm) - Record of the creep effectusing a capacitive displacement sensor

0,00

20,00

40,00

60,00

80,00

100,00

120,00

140,00

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Disp

lace

men

t (µm

)



Displacement with load: 2 casesStiffnessGravity

May be accounted in equivalent circuits

(b) (a) (c)


Application parameters that influence the piezo actuators

Spring Gravity

Force

Displacement

Load characteristics

Spring stiffness

Working point

Displacement

Force

No-load charac. curve

Shifted curve



Displacement with load: 2 cases


Laws of Piezo actuators - Equivalent circuit

Equivalent electromechanical circuit : Dynamic aspects

∆v v v j uI j Q

c k E

= − ==

=

2 1

1

ω∆ω

/

V NV F

1 : N

Cs

I ∆vc

Fj c

v N V

I N v j C Vs

= − +

= +

1ω

ω

∆

∆

Electrical Branch Motional Branch

Motional capacitance = 1/ Stiffness

Current

speed

CS = Blocked capacitance


Electro-mechanical analogy

FForcePotentialV

V = du/dt = jω.uSpeedCurrentI = dQ/dt = jω.Q

uDisplacementElectrical chargeQ

rmDampingResistanceR

MMassInductanceL

e = 1/k (k=stiffness)ElasticityCapacitanceC

SymbolMechanicsElectricSymbol


Equivalent circuits & related data

Same equivalent circuit but …: Boundaries conditions

Free-free configuration: The same mass each side of the piezo actuator: The stroke is divided by 2 and the resonant frequency is higher.

Blocked-free configuration: Blocked on the back side of the actuator the stroke in the front is the full stroke & the frequency is lower than the free free configuration.

Blocked-Blocked configuration: the piezo actuator is rigidly fixed on each side. The actuator generates force when voltage is applied.


Losses in equivalent circuit

Dielectric LossesDielectric loss angle : tg d => Ro

Mechanical lossesMechanical quality factor : Qm => rm

Ro V NV F

1: N

Cs

I ∆vrm c


Masses in equivalent circuit

Masses effectIn blocked-free condition,

Blocked side : v1 = 0 Free side, loaded with a mass M : F = j.ω.M.v2

In free-free conditions, with M1 and M2

Equivalent mass M = M1 . M2 / (M1 + M2)

Ro V NV F

1: N

Cs

I ∆vrm cM


Transfer functions

Vibration speed & displacement vs voltage

)1(//

)1(//

)/1(/)/1(.

2

2

cMcrjcNVu

cMcrjcNjVv

MjrcjNVvMjrcjvNV

m

m

m

m

ωω

ωωω

ωωωω

−+=∆

−+=∆

++=∆++∆=

Ro V NV F

1 : N

Cs

I ∆vrm cM


Transfer functions

Vibration speed & displacement vs voltageMechanical resonance frequency & Mode quality factor :

mr

E

mr

E

r rk

crQ

Mk

cM ωωω ====

11

Ro V NV F

1 : N

Cs

I ∆vrm cM

))/(/1(// 2rrQjcNVu ωωωω −+=∆

))/(/1(// 2rrQjcNjVv ωωωωω −+=∆


Transfer functions

Vibration speed & displacement vs voltageAt low frequency : Free displacement

At resonance : Amplified displacements

At high frequency : Blocked force

Ro V NV F

1 : N

Cs

I ∆vrm cM

cNVu =∆ / cNjVv ω=∆ /

cNQVv rω=∆ /0)/.(/ =∆==∆ ωVuQQcNVu

NVF =/


Equivalent circuit & associated data

Example APA200M+Mass M=40gr (Blocked-Free)Low Frequency f << fr

No opposing force from the Mass‘Free’ displacement : uLF = N/k. V

Resonance f = frfr = 1/2pi (k/M)0.5

Amplification by Qm : Mec. Quality factorDisplacement : uRes = Qm. N/k. V = Qm. uLF

3dB Bandwidth : df / Qm = fr /df

High Frequency f >> frMass opposing force = ‘Blocked’ force : FHF= N.V



Example APA200M+Mass=40gr (Blocked Free)Low Frequency f << fr

‘Free’ disp. : uLF = N/k.V => uLF/V= N/k u=230µm@V=150V => uLF/V= 1.3µm/V

Resonance f = frk=0.32N/µm ; M=0.04kg ; Qm = 10 fr = 1/2pi (k/M)0.5 => fr = 0.4kHzDispl. : uRes = Qm. uLF => uRes/V= 13µm/V 3dB Bandwidth : df = fr / Qm => df = 40 Hz

High Frequency f >> fr‘Blocked’ force : FHF= N.V => FHF/ V = NF=73N@150V => FHF/ V = N = 0.43N/V



APA200M+Mass=40gr (B.F.) / displacement per volt vs freq.

Controllable displacement :

Displ. Amplitude & Phase = Constant if :

f < fr/3

fr

Displacement generation

uLF/V = N/k0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

16,00

0,000 0,100 0,200 0,300 0,400 0,500 0,600 0,700 0,800 0,900Frequency [kHz]

[µm/V]

-200

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

Mod(u) [µm/V]Phase(u) [°]

[°]

© Cedrat Technologies - COMPACT v4.33


0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

16,00

0,000 0,100 0,200 0,300 0,400 0,500 0,600 0,700 0,800 0,900Frequency [kHz]

[µm/V]

-200

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

Mod(u) [µm/V]Phase(u) [°]

[°]



APA200M+Mass=40gr (B.F.) / displacement per volt vs freq.

fr

Qm

uLF/V = N/k

ures/V = Qm. N/k

Vibrations : Non Controllable displacements(Phase varies)

Amplitudes are amplified by Qm

Vibration generation


0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

40,0

0,0000 0,1000 0,2000 0,3000 0,4000 0,5000 0,6000 0,7000 0,8000 0,9000-180,00

-160,00

-140,00

-120,00

-100,00

-80,00

-60,00

-40,00

-20,00

0,00

Mod(v1) [mm/s/V]Phase(v) [°]

Frequency [kHz]

Mod(v) [mm/s/V]


Phase [°]


APA200M+Mass=40gr (B.F.) / speed per volt vs freq.

Vibrations : Controllable Speed Amplitude

3dB Bandwidth : df = fr / Qm

fr

Vibration generation

df = fr / Qm


0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

0,0000 0,1000 0,2000 0,3000 0,4000 0,5000 0,6000 0,7000 0,8000 0,9000Frequency [kHz]

Forc

e [N

/V] Mod(Fa) [N/V]



APA200M+Mass=40gr (B.F.) / Force per volt vs freq.

Controllable Dynamic Forces

Force Amplitude & Phase = Constantif

f >1.5 fr

fr

Dynamic Force generation

FHF/V = N = force factor


Admittance from equivalent circuit

Transferring motion branch in the electrical branchMotional capacitanceMotional resistanceMotional inductance

Ro V

Cs

I im Rm Cm Lm

2

2

2

/

/

.

NML

NrR

NcC

m

mm

m

=

=

=


0,00E+00

2,00E-03

4,00E-03

6,00E-03

8,00E-03

1,00E-02

1,20E-02

1,40E-02

1,60E-02

1,80E-02

2,00E-02

0,0000 0,1000 0,2000 0,3000 0,4000 0,5000 0,6000 0,7000 0,8000 0,9000Frequency [kHz]

[S]

-20

0

20

40

60

80

100

Mod(Y) [S]Phase(Y) [°]

[°]



APA200M+Mass=40gr (B.F.) / Admittance vs frequency

fr fa

Free capa. : CT

Blocked capa. : CS

Motion Cap : CmCm=CT-CS

Effective couplingkeff2 = 1 - fr2/fa2

=1-CS/CT

CS

CT


Equivalent circuits & related data

Effective coupling coefficient : keff

2 = 1 - fr2/fa2 = Cm / (Cm+Cs)

Electrical Resonance frequency : fr2 = (1/4π2) k/m = (1/4π2) / CmLm

Electrical Antiresonance frequency : fa2 = (1/4π2) [(Cs+Cm)/LmCsCm]

Mechanical quality factor :Qm = 1/(2πfrCmRm)



3 Frequency regionsLow frequency f < fr/3

Positioning applicationsFast actuation: injection valves, shutters …

Resonance f = fr Sonic and ultrasonic transducersAcoustic generators …

High frequency f> frStructure exciters in health monitoringProof mass dampers …



Displacement Transient response for a step voltageOvershot effects & Stabilisation time

=> Dynamic effects occur even on static applications=> High fr and low Q is better for static applications

Step response

0

1

2

0 1 2 3 4 5 6 7 8t / T

u / u

0

High QLow Q

T = 1 / fr

Tmin (open loop) = T/4

Tmin (Closed loop) = T/3

1/4


Additional effects in dynamic applications

Multiple vibration modesMulti modes electromechanical model:

VoltageSpeed


Electromechanical circuits : summary

Lumped representation,Electromechanical transduction means a «strong»coupling effect,Basic representation, widely used in measurements, semi active control, switching electronic design,A common basis for piezoactive actuators description.


Conclusion

Piezoelectricity : strong electromechanical coupling effect,The materials are characterised through 3 types of constants (s,d,ε),Wide use of the electromechanical analogy,An electrical scheme can be derived for simple cases and measured.


Piezoelectric Multi-layer Ceramics


Introduction

Basic architectureProcessInternal & external electrodesBehaviour, failure modesFuture of MLA


Bulk Piezoelectric Stack

StructureAssembled stack made of thick piezo plates & external electrodes electrically connected in parallel with alternative poling and electrodes

P

P

P

P

+ -

E

E

E

E


Piezoelectric multilayer actuators

StructureMonolithic Stack made of thin piezo layers & internal electrode electrically connected in parallel with alternative poling and electrodes & external electrodes

P E

P E SS


Piezoelectric Multilayer actuator : technological aspects

Green tape (mixture of oxydes (Zr02, Ti02, Pb0) with an organic binder),Indexing and screen printing of internal electrodes,Laminating operation (tape, stacking),Sintering operation,Cutting, grinding at the correct size,External electrodes deposition,Insulation,Poling operation.


Bulk Piezo Ceramic: Manufacturing process


Piezo Multilayer actuator : Manufacturing process

Courtesy of Ceramtec


Piezo Multilayer components : technological aspects

Technical difficulties :compatibility between the internal electrodes material and the sintering operation,shrinking during sintering (15 - 20 %).

850°C 1150°C 1250°C

Nickel, Copper Palladium Platinium


Piezoelectric multilayer actuators : internal & external electrodes

Internal and external electrodes influence the materials properties ; example of electrodes configurations :



Fully open internal electrodes :indexing operation, thermal mismatch, capability to deal with several sizes are easy,external insulation (esp. on the external electrodes) is tricky,subjected to ion migration,patented by Tokin (J).



Semi-open internal electrodes :thermal mismatch is medium,indexing operation is medium,need for an insulating coating,subjected to ion migration,



Buried internal electrodesthermal mismatch & stress relieving are tricky,no needs for external insulation coating,current density is limited,non poled ceramic tends to clamp the component.



Special design internal electrodes :claimed advantage : stress relieving during the sintering operation is easier,performances depend on the clamped region,1st special geometry patented by Siemens (D).


Piezoelectric multilayer components : technologies for external electrodes

Sputtered Ag-Pd external electrodes : bad solderability,

Ni-Au electro-deposited + Pb-Ag solder :better behaviour, subjected to fatigue effects,

Ni-Au electro-deposited + brazed mesh :good fatigue behaviour, patented by Ceramtec (D), subjected to failures with thermal shocks.


Coating technologies

Required dielectric strength : 80 kV/mm,Stability of the electrical insulation with temperature, humidity, …Compatibility with aggressive media,Relative independence of the elastic behaviour with temperature, ageing, …Easiness of application (viscosity, ..).


Functional performances

Standard materials (PZT5H) gives 1000 - 1300 ppm @ 1.5 - 2 kV/mm,On-going development of PZT5A materials :

high Curie Temp. (300 °C),1300 ppm @ 1.5 - 2 kV/mm,not necessarily commercially available.

Hard - type material (PZT4) may give 2000 ppm when driven at the mechanical resonance :

subjected to high cost of the internal electrodes.


Functional performances

Static strain levelDielectric lossesCTEDriftHysteresis


FMECA analysis

Process errors are expected to be discovered at the poling operation or through an over- voltage test,

Electrical breakdown is the most current problem :loss of insulation (failure in the coating due to humidity or excessive temperature),excessive stresses, crack propagation,Ag+ ion migration under humidity combined with high DC field.

Mechanical failure is often meet in dynamic conditionsPiezo ceramic are fragile in tensional forcesSee Prestressed-actuator section


MLA tested in APA : Lifetime tests

1010 cycles are achieved on a APA200M-NM ! Prestressed Actuator

Test conditions : 0-150 V @ 625 Hz, continuous

101 cycles 109 cycles



Electrical admittance evolution vs number of cycles.

Cyclage APA200M

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

3300 3400 3500 3600 3700 3800 3900f( Hz)

Admittance (S)

-80

-60

-40

-20

0

20

40

60

80

100Phase(°)

Mag 0 [S]Mag 1e6 [S]Mag 1e7 [S]Mag 1e8 [S]Mag 1e9 [S]Phase 0 [°]Phase 1e6 [°]Phase 1e7 [°]Phase 1e8 [°]Phase 1e9 [°]



Fatigue effects of the external electrodes after 4 109 cycles


Leakage current test under high humidity

Electrical DC field under humidity ⇒Ion migration ⇒Increase of leakage current ⇒Increase of temperature ⇒Electrical breakdown

Leakage current test

-1.40E-02

-1.20E-02

-1.00E-02

-8.00E-03

-6.00E-03

-4.00E-03

-2.00E-03

0.00E+00

2.00E-03

0 200 400 600 800 1000 1200 1400

Time (hours)

Curr

ent (

A)

0.00E+00

4.00E+01

8.00E+01

1.20E+02

Rela

tive

hum

idity

(%)

APA50S_01011APA50S_00060APA50S_00059PCT1PCT 2T1T2T3APA150M_01003TCMELRel. Humidity (%)

Failure

Failure


Reliability aspects

Arc over is the most important source of failure,Expertise of failed components.

High porosity Void probably after the arc over ?Acoustic tomography

Optical microscope view


Future of MLAs

Most advanced factories produce 100,000 units to 1,000,000 units/ year.Demonstrating the reliability in a given applications :

Arrhenius laws, Hass-halt tests,

Correct functional behaviour with a low sintering temperature,Use of the internal electrodes materials as dopants for the PZT material.


Piezoactive actuators : introduction

Material properties,Advantages and drawbacks of piezoactive actuators,Conventional mechanical amplifiers,

internally leveraged actuatorsexternally leveraged actuators

Amplified Piezo Actuators = Innovative solutions,Design methodology & Performances,Mechanisms = multi axis actuationConclusion.


Active materials : properties

Field E Field /H Field

Strain Stress Young’smodulus

Couplingfactor

Relativepermitivity /permeability

Curietemp.

Density

E (MV/m)H (MA/m)

(%) (MPa) (Gpa) (%) - (°C) (kg/m3)

Piezoelectrics

PZT - 7 E +- 0.5 +- 0.007 +- 5 72 67 425 350 7.7

PZT - 4 E + - 0.5 +- 0.015 +- 10 66 70 1300 325 7.6

PZT - 5 E +- 0.5 +- 0.030 +- 15 48 75 3400 195 7.5

CMA E +- 2.6 + 0.125 + 40 30 70 2100 180 8.0

Magnetostrictives

Terfenol-D H + 0.16 + 0.18 + 50 25 70 4 380 9.1


Active properties

MATERIALS Controlfield

E electricH magnetic

Max S-cstdielectric /magneticenergydensity

(kJ/m3)

Max field-cst elastic

energydensity

(kJ/m3)

OptimalMechanical

quality factor

(Qm)opt

Maxdissipated

energydensity

on (Qm)opt

(kJ/m3)

Max dissipatedenergy density

on Qm =2

(kJ/m3)

MASSIVE PIEZOELECTRICSPZT - 8 E 0.6 16.9 6.1 2.8 0.9PZT - 7 E 0.3 17.4 9.1 1.9 0.4PZT - 4 E 0.7 19.0 5.2 3.7 1.4PZT - 5 E 1.6 26.0 3.5 7.4 4.2

MULTILAYERED PIEZOELECTRICSSoft type E 8.0 26.7 1.9 14.3 13.3Hard type E 12.6 25.0 1.9 13.3 12.5

MAGNETOSTRICTIVESTERFENOL-D H 8.2 50.0 2.5 19.8 15.8


New European classification : example of material

Type 100 Type 200 Type 300 Type 600

Property Symbol

Unit Hard PZT Soft PZT Very hard PZT Very soft PZT

Free relativepermittivity

εT33

1100 - 1600 1600 - 2500 800 - 1100 2500 – 4000

CurieTemperature

Tc °C 300 300 250 180

Mechanicalquality factor

Qm 300 100 800 100

Piezoelectricchargecoefficient

d33 PC/N 300 400 250 600

Example ofmaterial

Ceramtec SP4Ferroperm PZ26Matroc PZT4DChannel 5400

Ceramtec SP5Ferroperm PZ27Matroc PZT5AChannel 5500

Ceramtec SP8Ferroperm PZ28Matroc PZT8Channel 5804

Ceramtec SP51Ferroperm PZ29Matroc PZT5HChannel 5700


Piezoelectric actuators and mechanisms


Advantages & drawbacks of piezoelectric actuators

Fast responseUnlimited positioning resolutionLarge forceNon-magnetic operation & no magnetic field generated

Limited displacementsSubjected to fatigue effect (depends on the design)Temperature dependant (Curie temperature)


Piezoelectric Multi-Layer Actuators (MLA)

History of piezo ceramics1880 : Quartz (P.Curie)1922 : Langevin Transducers1960 : PZT ceramics

∆L/L = 0,3mm/m @ ∆V= 2000V

1990 : MLA components∆L/L = 1,2mm/m @ ∆V=200V

Structure of a MLAPiezo layers (PbZrTi)Internal Electrodes (Pt or AgPd)External Electrodes Insulation (Coating or ceramic)

The naked MLA ceramic bar is fragile to tensile force...


Internally leveraged Actuators (stack)

Direct Piezo ActuatorsTwo different prestress

serial parallel

Belleville washers

DPA30

Piezo stack

… that is why we pre-stress it to increase its life time


Preload / Prestress of Piezo Ceramic

Stress – Strain DiagramThanks to an optimum

static Preload,the strain is symmetricin traction & in compressionThe dynamic strain & stress range issymmetric and muchmore increased thanwithout preload

S = Strain

F/A = StressPiezo Ceramic is fragile in tensile stress

Elastic limit in traction

Elastic limit in compression

Optimum level of static preload / compression pre-stressing force

Dynamic range without preload

Dynamic range with preload


Direct piezo actuators can be prestressed through an external frame.

The design of the parallel spring is dependant on the applied prestress.

Stress analysis of the pre-stress frame of the

PPA (I-DEAS computation

of half the frame)

Internally leveraged Actuators (stack)

PPA60L


Pre-load effect - short & open circuit


Internally Leveraged Actuators (bender)

Courtesy of Midé (ACX) & CeraNova

Quick Pack 10ni



Courtesy of PI



Ring Bender CMB-R - Courtesy of NOLIAC


Internally Leveraged Actuators (unimorph)

Courtesy of Aura Ceramics Inc.


Internally Leveraged Actuators (unimorph)

Courtesy of Face international

Thunder TH 8-R


Internally Leveraged Actuators (building block)

Courtesy of Michigan University & MSI


Externally leveraged actuators (hydraulic amplification)


Use of flexural hinges and pivots

Mechanical Efficiency η = (FActuator*uActuator) / (FMLA*uMLA) = 10%

MLA piezo ceramic

Externally leveraged actuators (lever arm)

Hertzian pivots

flexure pivots


Externally leveraged actuators (flextensional)


Externally leveraged actuators (flextensional & others)


Amplified piezoelectric actuators

magnification of the MLA displacements using an elastic amplifier,

reduction of the blocked force,

optimisation of the overall efficiency

Includes a high prestress to get good dynamic properties


Amplified piezoactive actuators

Use of the flextensional principle (uniform distribution of flexure pivots along the shell),The elastic amplifier is used to prestress the active material.


Amplified Piezo Actuators

Finite element deformations (ATILA software)


Amplified piezo actuatorsRange of APAs



Smallest APAs to largest APAs

APA 40µXS , APA35XS, APA500XXL


APA static properties

APA DeformationsAPA strain : Sa = ua / hPiezo strain : Sp = up / L

h

L

ua

up/2 up/2


Actuators type APA APA APA120ML 400M 900M

Actuator dataFree displacement µm u a 130 400 916

Max Blocked force N F a 1 400 40 16Stiffness N/µm 10,8 0,1 0,017Actuator Height cm h 4,5 1,4 1,1

Actuator free strain % S a 0,29 2,9 8,3

Active material dataLength cm 6 4 4Section cm2 1 0,25 0,25No-load strain ppm S p 1000 1000 1000Blocked stress MPa 40 40 40No-load displacement µm u p 60 40 40

Blocked force N F p 4000 1000 1000

Amplifcation analysisDisplac. amplification factor A u 2,2 10,0 22,9

Strain amplification factor A s 2,9 28,6 83,3Force disamplification factor 2,9 25,0 63,5Actuator mechanical efficiency % η 76% 40% 36%


APA DeformationsAPA strain :

Sa = ua / h

Piezo strain :Sp = up / Lp











APA amplificationDisplacement amplification:

Ad = ua / up

Strain amplification: As = Sa / Sp











APA amplificationamplification efficiency:

η = (ua Fa) / (up Fp)


APA dynamic properties

Prestress of Piezo Ceramic :Needed as it cannot bear tensile stress

APA stress budget considered at the design :prestress stress : static stresses from the prestress process.actuation stress : stresses produced in the shell when the ceramic is supplied. external force stress : stresses due to external vibrations or shock or applied forces.

⇒ No weak point in APAs :No hinges, elastic pivot...



APA amplificationamplification efficiency:

η = (ua Fa) / (up Fp) Use of a genetic algorithm with the following objective :

free displacementefficiency η as high as possiblestresses < 0.75*Re.

0

5

10

15

20

100 110 120 130 140

Stroke (µm)

Stiff

ness

(N/µ

m)

Stress >=700MPaStress >=600MPaStress <600MPa56% Eff CurveAPA120ML

Example of a genetic run for the APA120ML


Performances comparison

Actuator namesP844.60 PPA90L APA120ML APA230L APA500L APA500L-

SVAPA750XL-

SVActuatorActuator Mass gr 204 147 155 275 200 170 600Actuator Height cm 13.7 10.7 4.5 8.5 5.5 4.9 7.0Actuator Volume cm3 43 43 36 74 48 41 91

No-load free displacement µm 90 90 120 236 500 560 1150Stiffness N/µm 33 39 11.7 5.7 1.14 1.39 0.8Blocked force N 2 970 3 510 1 400 1 345 570 778 920Stored elastic energy J 0.134 0.158 0.084 0.159 0.143 0.218 0.529Output elastic energy mJ 33 39 21 40 36 54 132

Performances ratioFree deformation along active axe % 0.07 0.08 0.27 0.28 0.91 1.14 1.64Output Energy / actuator volume J/dm3 0.78 0.91 0.59 0.54 0.74 1.31 1.45Output Energy / actuator mass J/kg 0.16 0.27 0.14 0.14 0.18 0.32 0.22

Some CEDRAT products : Standard & customised

Best actuator in 1998 according to US specialists before Cedrat product launching



APA force limitsCeramic Prestress : typically designed to about half blocked stress of the piezo ceramicforce limit at the actuator level Fmax : half the max actuator blocked force Fa :

Fmax = Fa/2

This criteria is used to analyse the limitation of the actuator in dynamic conditions, including resonance



Prestress of Piezo Ceramic :Needed as it cannot bear tensile stress

APA stress budget considered at the design :prestress stress : static stresses from the prestress process.actuation stress : stresses produced in the shell when the ceramic is supplied. external force stress : stresses due to external vibrations or shock or applied forces.

⇒ No weak point in APAs :No hinges, elastic pivot..



APA force limitsCeramic Prestress : designed to half blocked stress of the piezo ceramicforce limite at the actuator level Fmax : half the max actuator blocked force Fa :

Fmax = Fa/2

This criteria is used to analyze the limitation of the actuator in dynamic conditions, including resonance



APA120ML in blocked-free with M=180g & Q=10

Static propertiesFree displacement : ua = 130µm @170VDisplacement per volt : u/V = 0,76µm/VBlocked force : Fa = 1400N @150V

Dynamic limitsMax voltage : Vmax = 170Vpp = 85Vp

Max dynamic force due to prestress : Fmax = 700N

Analysis with COMPACT tool based on eq circuit




Voltage limit Force

limit




Voltage limit

Force limit



APA120ML in blocked-free with M=180g & Q=10Thanks to prestress : Fmax = 700N

umax > 120 µm between 0 and 1000Hz

If low prestress : Fmax = 70Numax > 100 µm between 0 and 200Hzumax = 15 µm at 1000Hz

⇒ Prestress allows to get high displacements in a large bandwidth

⇒ Advantage for dynamic applications such as scanning, active damping, vibration generators ...


Mechanical integration issues

Type Pre-stress Mechanical interfacesfor actuator ‘s fixing

Mechanical interfacesfor payload ‘s fixing

Mountingtechniques

Quick Pack NO NO NO GlueBimorph NO NO NO GlueRing Bender NO NO NO GlueThunder YES YES NO Glue / ScrewDPA YES YES (Threaded Hole) YES (TH) Glue / ScrewPPA YES YES (TH) YES (TH) Glue / ScrewAPA YES YES (TH) YES (TH) Glue / Screw


Conclusion about APAs

Use of Ceramic Multilayer Actuators

Use of an elastic amplifier with amplification ratio in the range 2 - 10

Optimization of the efficiency using FEM

Includes a high prestress to get good dynamic properties


Mechanisms

Multi axis actuation


Mechanims

At least one active axis : Possibility of several degrees of freedom (dof)

Linear motion, rotation motion, combinations

Passive axis controlled by guidingActive axis could be geared


XY orthogonal stages

Courtesy of PI

Neither mechanically centred nor thermally compensated

Stack of 2 linear stages

• slow response time

• risk of orthogonality error

• No axis runout compensation

Monolithic but nested module

• No axis run out compensation

Monolithic but nested module

• Run out & cross talk

compensation in closed loop


This stage, [+/-100µm]x[+/-100µm], is mechanically & electrically centred and thermally compensated

Active Control of Position :Symmetric XY stage XY200M

XY orthogonal stages


XY micro sanner piezo stage : Improvement of Camera Sensor Resolution

ApplicationsEmbedded IR cameras

> 100 THALES cameras> 400 piezo actuators

Future space missionsIR cameras / telescopes

XY microscanners for improving resolution of Infra Red cameras

Push-pull stage based on APA25XS


Piezo Mechanisms with several dof

Hexapode HEX100M

Tx = Ty = 65 µm; Tz = 57 µm

Rx=Ry= 2.7 ; Rz= 1.1 mrad (+/-)

XYZ200M-SG

Tx=Ty= +/- 100 µm ; Tz = 200 µm


Single axis - linear stage

X60SMPush pull configuration

Mechanically & electrically centred

Thermally compensated

Very low parasitic motions

stroke = 60 µm


The tip-tilt mechanisms are the most simple structures that can perform one or two rotations, plus a vertical (z) actuation :

Space qualified DTT35XSCourtesy of CNES Pharao project

one rotation: +/- 0.5° two rotations: +/- 2mrad

TT50S

Tilt Mechanisms


Objective Piezo Positioner

References Unit OPP120SMNotes Preliminary dataSensors option ECLActive axis TZMax. No-load displacement µm 90Max. parasitic X Y rotations µrad 140Voltage range V -20 … 150Resolution nm 9Stiffness N/µm 1,11Heigth mm 50,0Dimensions mm 65 * 40Mass g 170Unloaded resonance frequency (in the actuation's direction) Hz 450

Response time ms 1,11Loaded resonance frequency (in the actuation's direction) load = 200 g Hz 285

Loaded response time ms 1,75Capacitance (per electrical port) µF 3,15

Mechanical interfaces (payload) object ive interface to be specif ied

Mechanical interfaces (frame) tbd

Electrical interfaces 1 RG178B/U coaxial cable


Fast Piezo Shutter FPS200M

Technical Features with dedicated SP75 driving electronics :

Aperture > 300 µm; response time < 2 ms; Overshoot < 10%; low jitter;


Conclusion about mechanisms

Combinations of several dofPush pull configuration to cancel thermo- mechanical issueGuiding and closed loop needed to compensate or cancel parasitic motionsCompatibility in option with severe environment (UHV, Cryogenic, Non magnetic, Space …)


Driving & control electronics for piezoelectric actuators & mechanisms


Introduction

Specifity of piezoelectric loads, different cases (static, quasistatic, resonant),Basics of amplifiers,Practical implementations,Control of piezoelectric actuators,Conclusion.


Introduction – load & frequency

Piezoelectric actuators constitute capacitive resonant loads: pretty high stress generated in the active switches Different types of applications :

Static : load of a capacitance; compensation of dielectric losses,

Dynamic : reactive load, I = jωC.V (out side resonance)

Resonance : Complex load

0,00E+00

2,00E-03

4,00E-03

6,00E-03

8,00E-03

1,00E-02

1,20E-02

1,40E-02

1,60E-02

1,80E-02

2,00E-02

0,0000 0,1000 0,2000 0,3000 0,4000 0,5000 0,6000 0,7000 0,8000 0,9000Frequency [kHz]

[S]

-20

0

20

40

60

80

100

Mod(Y) [S]Phase(Y) [°]

[°]


Admittance Curve Y=I/V


Introduction – driving signal

Definition of the output signals voltage&CurrentDC, sine or square signal


Linear amplifier for static / dynamic applications

For a given amplifier, having a given current limitation, Bandwidth varies with the actuator capacitance

Bandwidth using a 40W Vcc source

Frequency Response of the LA75 Linear Amplifieragainst various Capacitive Loads

020406080

100120140160180200

1 10 100 1000 10000Frequency (Hz)

Volta

ge ra

nge

(V)

C = 0,7 µFC = 2,2 µFC = 24,0 µF


Dynamic applications : example with a linear amplifier

V = -R1 / R2 VinRequired electrical power

Electrical current i = 2π f V Cbf

Electrical power dissipated in the amplifier, P = 4V2 f Cbf

Numerical example : Cbf = 1 µF, V=100V, f = 2 kHzi = 1.3 A, P = 80 W


Example of dynamic application: APA500L

Standard APA500L features:

Displacement = 500 µm

Blocked force = 560 N

Resonant Freq. = 460 Hz

C = 40 µF

Peak Amplitude vs frequency

Displacement = 500 µm @ 100 Hz

Driven by a LA75C-1 from Cedrat T.


Noise in static / dynamic applications

Noise in static applications : 80 mV/ @ 50V = 0.16 %80 dB signal to noise ratio can be obtained through a correct shield.100 dB signal to noise ratio obtainable at the expense of a reduced bandwidth


Amplifiers for static applications 2 principal classes:

The linear amplifier, A, B or AB classes,The switching amplifier D classes and Co,

Characterised by:Output current,Output voltage,Bandwidth,Gain,Capacity to drive reactive loads,THD,SNR,Protections


Basics of amplifiers

Use of a the traditional linear amplifier

PZTRg

R1

R2

Vin

Cbf



Class A amplifiers : dynamic behavior around the static polarisation point,

Low efficiency on a resistive load : 25 %,



Class B amplifiers :The characteristics is influenced by the non – linear characteristics of the transistors around the static point => pretty high distortion.



Resulting distortion of the Class B amplifier,Efficiency on a resistive load = 78 %


Basics of amplifiersClass A-B amplifiers : cancellation of the distortion through diodes or junction multipliers


Basics of amplifiersClass D (switching) amplifiers : high frequency on / off operations and filtering,Half-bridge and Full bridge topologies (depending on load) :

Half bridge is used for capacitive load,Full bridge is used for inductive load.



Class D (switching) amplifiers :On-off control through PWM in open loop,Filtering function is often necessary to reduce to output voltage ripple.


Basics of amplifiers : Synthesis

HighLowLowLowMaximal power

LowImportantImportantImportantDimensions(for a given load)

HighMediumMediumVery lowEfficiency

HighLowLowLow Noise

LowLowMediumLowDistortion

High (require high frequency switching)

High High High Bandwidth

HighBipolartransistor

HighHighHighVoltage

Class DCommentsClass ABClass BClass A

Switching AmplifierLinear AmplifierCriteria


Amplifiers for Dynamic applications

Linear amplifier : high reactive load,design of heat sinks necessary,

Switching amplifier : More complex control strategy,Possibilities for energy recovery.


Dynamic applications

Schematic of a switching amplifier



Schematic of a switching amplifier



Basic circuit



Switching strategy including energy recovery


Dynamic applications : Conclusion

Energy recovery and precise charging results from a compromise,Switching strategy should be monitored through a numerical controller.Monitoring the charge (and the resulting displacement) may be used as an alternative strategy.


Introduction - control

Static & dynamic : controller (PID) to remove the hysteresis,Charge controlled versus voltage controlled amplifiers,


Control in static applications

Very high position accuracy can be obtained with piezoelectric actuatorSensors for a closed-loop system

strain gaugecapacitive displacement sensorEddy current sensor


Control in quasi-static applications

Typical structure of an analogue controller :PI + Filter topology

Typical step response


The Strain gauges are the most simple sensor :Use of a complete Wheastone bridge bonded on the MLA to achieve the best sensitivity.Example of a APA50S with strain gauges :

Control in quasi-static applications


Static applications

Removal of the creep effect (process of repoling)

Actuator's displacement (µm) - Record of the creep effectusing a capacitive displacement sensor

0,00

20,00

40,00

60,00

80,00

100,00

120,00

140,00

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Disp

lace

men

t (µm

)


Static applications

Removal of the hysteresis

Removal of the piezoelectric actuator hysteresis using a displacement sensor

0

1

2

3

4

5

6

7

8

9

0 2 4 6 8 10

Order (Volts)

disp

lace

men

t mea

sure

men

t (Vo

lts)

closed loop off

closed loop on


Static applications

Alternative hysteresis removal method by using an electrical charge control,The control is more complex.


Static applications

Charge amplifier:


Conclusion

Piezo actuators constitute mainly capacitive loads ; it can differ for resonant applicationsThe reactive power requires attentionQuasi static applications & use of MLA can use PWM driver, without step-up transformer


SP75 : Switching Power for driving Actuators in fast on-off motion

Options available: PID and Micro Controller for feedback and monitoring through a PC, via USB or RS-232 .

Driving Electronics for Piezo Actuators & Mechanisms

CA45 & LA75A : Linear Amplifier for driving Actuators with low noise for precise & quasi-static motion

LA75B & LA75C: Linear Amplifier for driving Actuators in power demanding dynamic motion

See technical data sheets in the “Piezo Products catalogue”


How to choose the right actuators and driving electronics ?


How to chose the right actuator ?

Depending on the type of applications, several parameters govern the selection of the actuator :

Static Dynam ic Im pulse

Param eters ofthe actuatorStroke X X X

Stiffness

Bandwidth X XElectricalcapacitance

X X

Param eters ofthe applicationPayload m ass X X

Parallel stiffness X X X

M ax. current ofthe driver

X X


How to chose the right actuator ?

Frequency / response time considerations in dynamic applications

Controllable frequencies : f< fmax = fr/3Impulse response : tmin = 1/(3*fr) =T/3

fr= device resonance frequency



Displacement Transient response for a step voltageOvershot effectsStabilisation time

Step response

0

1

2

0 1 2 3 4 5 6 7 8t / T

u / u

0

High QLow Q


Arrangement of piezo-actuators

Parallel arrangement adds force Serial arrangement adds displacement


Deriving the electrical circuit from the actuator ’s properties

Stiffness k, modal mass m, unloaded resonance frequency fr, capacitance CBF, force factor N, voltage V, blocked force F, payload mass M, motional capacitance Cm, clamped capacitance C0, m = k/(2πfr)2 ; N = F/V ; Cm = N2/kC0 = CBF - Cm Loaded fr = 1/2π (k/(m+M))1/2


Exercices

How to select piezo actuators, associated mass and electronics ?Analytical modelsFinite element models

COMPACT tool Excel tool based on an analytical modelFree ware, download from Cedrat webFast way for pre-dimensioning or selecting components


Exercice 1: Slow positioning of an optic

A summary of the specifications is given in the table beside :

Application is optic positioning in lab environment

5Max Frequency(Hz)

400Max Displacement

(µm)

1000Payload Mass (g)

RequiredSpecs


Exercice 2: Fast positioning of a tool


Application is oval piston machining

100Max Frequency(Hz)

100Max Displacement

(µm)

2000Payload Mass (g)

RequiredSpecs


Exercice 3: Ultrasonic vibrations


Application is ultrasonic glass cutting

20 000Frequency (Hz)

6Displacement(µm)

3Payload Mass (g)

RequiredSpecs

With PiezoactuatorAssistance

Without Piezoactuator Assistance

Courtesy of Schott


Example 4: Pulsation force Generation


Application is Anti-vibration for a turbo-engine aircraft cabin (ATR42)

100-500Frequency (Hz)

8-10NForce (N)

100 KqPayload Mass (g)

RequiredSpecs


Example 5: Fast response


Application is Piezo injectors for fuel injection

<1msResp.time (ms)

>60µmStroke (N)

0,015 KqPayload Mass (g)

RequiredSpecs


Illustration of limitations in dynamic applications

Current limitation of the driving electronics (working frequency)Force limitation of the piezo actuator (Payload mass & working frequency)Self heating limitation of the piezo ceramic (Duty cycle)

=> Computations and curve analysis (Cedrat Technologies Excel sheets - COMPACT tool)


Current limitation

APA120ML + 1 kg in blocked free condition (Resonant Freq = 0,5 kHz) driven by a LA75A-1 (Imax peak = 90 mAmps)


Power and Force Limitations

APA120ML + 1 kg in blocked free condition (Resonant Freq = 0,5 kHz) driven by a LA75C-1 (Imax peak = 2,4 Amps)


Adiabatic Self Heating

APA120ML + 1 kg + LA75C-1

APA120ML + 1 kg + LA75A-1


Piezo Motors Overview


Different types of piezoactive motors

‘INCHWORM’ motors : high resolution, low speed.Inertial Step Motors (ISM) : simple structure, multiple degrees of freedom, high potential for micronization.Ultrasonic motors (USM) : large torque at low speed and at rest,silent and nonmagnetic operation, excellent dynamic characteristics.


‘Inchworm’ motors

Use of active grips and active member along a rail & combination of activations of grips and active member.


‘Inchworm’ motors

Linear inchworm CIMMS Virginia Tech M.Vaughan ,D.J.Leo from US Center for Intelligent Material Systems & Structures, Integrated piezoelectric linear motor for vehicule applications, Proc IMECE02/TTRST-32942, ASME Symp., New Orlean US, Nov.17-22, 2002,, 9p.

Inchworm with APA120ML


CEDRAT piezo motor stepping solution

Use of at least two Amplified Piezo Actuators

Anchor point

(a) driving stage

(b) return stage

Slider (or rotor) Driving direction


LISA Laser Interferometer Space Antenna

High Pointing Precision Piezo MotorPrinciple

Normal displacement : same voltage supply Tangential displacement : opposite voltage supply

Anchorpoint

MLA-1 MLA-2

Anchorpoint

Amplified Piezo Actuators APA with the piezo ceramics driven : in phase (left) / in opposition (right)


LISA Laser Interferometer Space Antenna

High Pointing Precision Piezo MotorAccuracy <100nradresolution < 5nradnon magneticno lubricant

LISA HP Piezo Motor Breadboard (courtesy of ESA)


Inertial step motors (ISM)

Working principle:sudden contractio: inertia effectslow contraction: no inertia



reliability for multiple degrees of freedom motion : for instance, a piezoelectric XY micrometric stage



Rotating ISMNew Focus active screw = pico motor


CEDRAT New miniature linear piezo motors

SPA Stepping Piezo Actuator from CedratNew APA-based piezo motorsGolden Micron 2008 at MicronoraCedrat patent


SPA Stepping mode Principle4 components

Stick-Slip step excited by a saw tooth signalAccumulation of steps to get a long stroke (several mm)

SPA60SM Animated Principle (2 steps) One stick-slip step

Mass APA (piezo) Rod Clamp

CEDRAT New miniature linear piezo motors


New miniature linear piezo motors : SPA

SPA combined modes for Nano positioningStepping mode (M1)

Saw tooth signal Stick-slip of the rod in the clamp

Deformation mode (M2)Load fixed on the MassAPA deformation proportional to voltage

One stick-slip step (M1)

Long stroke combining Stepping (M1) and Deformation (M2) Modest

u1

M1 M2



SPA tests : Combined M1–M2 modes for Nano positioningAchieved precision : 60nm (due to sensor) Achieved resolution : 0.5nm (due to amplifier)

Long stroke combining Stepping (M1) and Deformation (M2) Modes, and associated electric excitation

SPA35XS bench with sensor



SPA AdvantagesSimple APA-based structure

Reliable, large heritage from APA

One channel electronicsScalable

Various APA size and forces

High degree of miniaturization

Cryogenic versionsNon- magnetic versions (MRI-compatible)

Firm connection between the load and the motor Fine positioning with nanometer resolution on a large range (due to the APA amplified stroke) Cost effective approach

SPA30uXS


New CEDRAT miniature linear piezo motors

SPA performances

References Unit SPA uXS-S SPA uXS-F SPA XS-S SPA XS-F SPA SM-S SPA SM-FNotes Preliminary Preliminary Preliminary Preliminary Preliminary PreliminaryBase APA30uXS APA30uXS APA35XS APA35XS APA60SM APA60SMLong stroke (M1) mm 4 4 10 10 20 20Stiffness (M1) N/µm 0,108 0,108 0,49 0,49 1,38 1,38Max speed (M1) mm/s 70 30 30 5 30 5Blocking force at rest (M1, M2) N 0,4 0,8 3 6 15 30Max actuation force (M1) N 0,1 0,3 1 2 5 10Short high resolution stroke (M2) µm 30 30 55 55 80 80Resolution (M2) nm 1,7 1,7 3,1 3,1 4,5 4,5Bandwidth (M2)** kHz 3,2 3,2 0,6 0,6 0,6 0,6Capacitance (M1, M2) µF 0,052 0,052 0,25 0,25 1,55 1,55Height along active axis mm 15 15 30 30 50 50Base size mm2 5 x 9 5 x 9 16 x 16 16 x 16 27 x 27 27 x 27Inertial mass gr 0,27 0,27 30 30 70 70Mass gr 2 2 50 50 120 120Max current consumption mA 60 60 60 60 350 350Holding current mA 0 0 0 0 0 0LA75 types compatibility A - B - C A - B - C A - B - C A - B - C B - C B - CCA45 compatibility yes yes yes yes no no


What are ultrasonic motors ?

Use piezoelectric material to produce a small elliptical displacement in the stator,Drive a moving member through friction forces.


Ultrasonic Motors : USM classification

Travelling Wave Ultrasonic Motors (TWUM)Standing Wave Ultrasonic Motors (SWUM)Hybrid Type Ultrasonic Motors (HTUM)Mode Conversion Ultrasonic Motors (MCUM)Multi Mode ultrasonic motors (MMUM)Mode Rotation Ultrasonic Motors (MRUM)


Travelling Wave Ultrasonic Motors (TWUM)

Excitation of a rotating flexural mode in an elastic ring.


Machining tolerance of contact surfaces

- Flatness

- Roughness

Geometric conformity of static contact


Mode Conversion Ultrasonic Motors (MCUM)

Newscale Technologies -> Squiggle motor

AF system


Design of multi-modeultrasonic motors

Working principle (patented Cedrat technology) :


Design of multi-mode ultrasonic motorsTwo vibrations modes

Flexural modeexcitation in phasenormal displacement

Translation modeexcitation opposite in phasetangential displacement


LPM20-3 using a LVDT position sensor


LPM20-3 Load characteristic

Perfomances of standard LPM20-3 measured in 1999


Friction layers’ properties

Thermal stabilityElasticity : dynamic interpenetration at the interfaceAbsence of noise generated by slidingSize of the third body particles Wear resistance : fibbers & powder reinforced polymer


Wear aspects in piezomotors

Critical role of the fibbers use to reinforce the polymer.Surface after 520,000 actuation's in vacuum :

polymer vibrating steel

Frictional directionFrictional direction


Wear aspects in piezomotors

A stable frictional coefficient of 0.45 is obtained after an adequate running procedure,No change of performances after 520,000 strokesView of the wear zone :


Conclusion for piezo motor tribology

Mechanism of preload applicationRunning aspects Stability of shift velocity accommodation mechanismsDebris evacuation device


Driving piezo motor

Inchworm / ISM => Standard electronics similar to piezo actuator drive,USM : resonant load

switched inverters are generally used,automatic frequency resonance tracking necessary,non linear behaviour of the USM for the automatic point of view.


Piezomotors : conclusion

Motors useful for positioning applications,Superior torque / mass ratio,Current applications in microelectronic, space,Difficult subject,Development require multidisplinary skillness (piezoelectricity, mechanics, tribology, electronic, automatic, …).


Applications using piezo actuators

CEDRAT TECHNOLOGIES REFERENCES


Applications for piezo actuators

Optics , Air & SpaceValvesActive damping ActuationMachine tools Telecom

Electrical generator Reclamation


Standard Actuators Products


Standard Drivers / Conditionners Products


Optics Air & Space

Identified ApplicationsActive vibration controls of electronics,instrumentsActive vibration controls in cameras, telescopesImprovement in CCD/CMOS cameras resolutionRefocusing of space telescopesActive optical filters, extended cavity lasers,Active Flaps of Helicopter blade, Missiles, DronesActive Flaps of Air plane (mock-up) flaps, Active shape control of wings Direct drive of Hydraulic jacks Scanning function in fine space instruments ...


Optics, Air & Space

Id. applications needs Actuators with:High output energy to mass ratioLow power consumptionResistance to severe environment (esp vibrations)High bandwidthHigh resolution

Cedrat Response:Piezo Actuators based on pre-stressed MLAMLA = low voltage multilayer piezo ceramicsDesign under ECSS standards + Qualification


Piezo Actuators & Electronics: Application for Space Telescopes

5 dof mechanism for telescope secondary mirror

BERTIN mechanism using CEDRAT APA120ML actuators & electronics


Piezo Actuators & Electronics: Space Qualification

‘FB-LA75A’ electronicsFly-Back DC-DC converter (from 20-50V to 150V) Linear Amplifier for Piezo ActuatorsStrain Gage conditionerAnalog Servo controller

Space qualificationEEE components analysisRadiation analysisThermal analysisEMC analysisMechanical analysisThermal-Vacuum tests

FB-LA75A space electronics for piezo actuators from CEDRAT

TECHNOLOGIES


• FM Piezo mechanism including SMA latch actuators

Flight model on board ROSETTA satellite, flying since Feb. 2004 displacement = [100*100*8] µm resolution = 4 nm successful commissioning !successful commissioning !

CAD view of XYZ piezo stage : 9 Piezos : 8 APA50S + 1 PPA10M

+ 2 SMA latch actuators + positions/check sensors

Dust analysis of the comet, heart of MIDAS AFM instrument (Courtesy of ESA, European Space Agency)

Active Control of Position (scanning):Space XYZ stage for ROSETTA/MIDAS


This stage, [+/-100µm]x[+/-100µm], is mechanically & electrically centred and thermally compensated

Space qualified model

( Courtesy of CNES, French Space Agency )

Closed loop options: Strain Gages or Capacitive Sensors

Normally centred piezo mechanisms:Symmetric XY stage XY200M


Application for Improvement of Camera Sensor Resolution

Over-sampling technique 4 successive pictures (n° 1 to 4) are merged. The distance between points correspond to 1/2 sensor pixel. The XY stage carries either a lens or the CCD itself.

Principle of the over – sampling

Lens motion produced by the XY micro scanner to perform over-sampling



Improvement provided by over-sampling technique

Improved images using over-sampling technique



Cedrat XY micro scannersPush-pull stages based on 4 APA25XSMonolithic designThermally compensatedStroke [-15µm +15µm]²Open loop controlQualified :

Operation in vibrationTemperature -40 +80°CLife time

XY microscanners manufactured by CEDRAT TECHNOLOGIES



Applications of Cedrat XY micro scanner piezo stageEmbedded IR cameras

> 1000 THALES cameras> 1000 Microscanners> 4000 piezo actuators

Future space missionsIR cameras / telescopes

THALES Catherine MP LWIR QWIP Camera

Courtesy of THALES OL


Normally centred piezo mechanisms: Tilt Mechanism for laser pointing

DTT35XS PHARAO Double tilt : a space MOEMSMOEMS = Micro Optical Electro Mechanical SystemControl of a mirror on 2 dof in rotation (Rx, Ry)Key Components:

1 Mirror 4 Hinges4 APA35XS Actuators 4 Strain Gages Sensors (bonded on PZT MLA)


DTT35XS PHARAO Double tilt : a space MOEMSMass = 15 gr (2gr per actuator)Rx, Ry = +/- 2mrad (Tz = 20µm is not used)Positioning Precision = 1µrad r msTemperature = -40°C / +75°CPassed qualifications :

Life timeVibrationShocksThermal Vacuum cyclingNon magnetism...



DTT35XS PHARAO Double tilt : a space MOEMSBatch of 10 Qualification Models of DTT35XS in casing delivered to EADS Sodern (Jan 2003) Batch of 8 Flight Models in production

Qualification Models of the PHARAO/MEF space piezomechanisms based on 4 APA35XS

(courtesy of EADS)



Normally centred piezo mechanisms:A Rz mechanism for despinning correction

Correction of the spinned movement of the GAIA spacecraft on the CCD of the RVS instrument

Breadboard for GAIA/RVS space piezo mechanism based on 2 APA400M

(courtesy of Obs. Meudon)


Fast Piezo Shutter FPS200M

Technical Features with dedicated SP75 driving electronics : Aperture > 300 µm; response time < 2 ms; Overshoot < 10%; low jitter;

Fast Piezo Shutter FPS200MQualification of 1 FPS200M (1 year test ) by ESRFBatch of 8 FPS200M delivered to ESRF


Refocusing mechanisms (1/3)

External laser cavity tuning by a PPA10M Parallel Pre-stress piezo Actuator.

10 Flight Models planned for the end of 2004

PHARAO/LCE space piezo mechanism

(courtesy of EADS / SODERN)



The dynamic refocusing of the 1st European LIDAR (ALADIN on board on ESA /AEOLUS).

The main difficulties are :

• The high bandwidth (> 2 kHz),

• The lifetime (4*1010 cycles).

4 QM/FM delivered before end 2004

ALADIN AEOLUS space refocusing piezo mechanism

(courtesy of GALLILEO Avionica)



The piezo actuator is used to refocus a laser beam

ALADIN Lidar

(courtesy of GALLILEO)


Piezo Actuators: Application for Helicopter Flap Control

Flap design proposed by CEDRATECHNOLOGIES in 1998



RPA Helicopter Project:Active trailing edge flaps on the main rotor for:

decrease BVI noise in descent flight improve the dynamic behaviour of the rotor throughout the largest possible flight domain

Work done by Onera (French Aircraft Design Inst.)Support of:

French Civil Aviation AuthorityMinistry of Defense (DGA)Eurocopter



Blade Vortex Interaction (BVI) noise:



Wind tunnel scale rotordiameter of the Mach-scaled rotor : 4.2 m the maximum blade chord : 140 mm the flap dimensions at wind-tunnel scale :

210 mm in span 21 mm in chord

geometrical reduction factor : 2.619



Requirements for the Mach-scaled rotor:− natural freq. of the flap/hinge axis : > 150Hz− min. flap deflection : ± 5°, 78 Hz, static moment of 1.22 Nm

for hinge centred at 0%− ideal flap deflection : ± 15°, 262 Hz, static moment of 4.9 Nm

for hinge centred at 0%− flap actuation frequencies : from 0 to 5-per-rev

with respect to rotor rotation speed − required energy/kg of actuators : > 150mJ/kg − maximum centrifugal field : 2300 g



Comparison of Actuators by ONERA for selection

⇒ Selection of the standard APAs from CEDRAT because of highest energy density

Maryland 1/7th scale blademodel

in-house fabricated

Maryland full scale bladePrototype

CEDRAT APA230For 1/ 2.62th modelmass production

CEDRAT APA500Lmass production

Actuatortechnology

Multi-layeractuator

configuration (8layers)

Piezostacks withL-L amplification

mechanism

Piezostacks inelliptic housing

Piezostacks in elliptichousing

Voltage ± 134V → ± 400 V 0-120 V 0- 200 V 0- 200 VMass of actuator 14 g 634 g 250 g 208 g

Blocked force ( F ) 8 N 20 N 1350 N 570 NMaximum stroke ( x ) 165 µm 889 µm 230 µm 500 µm

Stiffness 0.048 106 N/m 0.021 106 N/m 3.48 106 N/m 1.14 106 N/mResonance frequency above 150 Hz Above 150 Hz 800 Hz 450 Hznergy to weight ratio of

actuator24 mJ/kg 28 mJ/kg 310 mJ/kg 342 mJ/kg

Ratio of Energy.. /L-LEnergy..

0.44 1 5.86 6.45

Width (chord axis) 33 mm 71 mm 69 mm 55 mmLength (span axis) 60 mm 183 mm 140 mm 145 mm

Thickness 2 mm to 5 mm 19 mm 10 mm 10 mmPk-to-pk flap

deflection±11°.5 ±11°.5 ±4°.5 ±9°.5



Onera flap concept using APAs



ONERA Centrifugal tests rig

• APA actuator

• Dummy flap

• Strain gage

• Rotation sensor

• BRAVoS rig



ONERA Centrifugal tests results

Active flap based on the standard APA230L under 0g

Active flap based on the standard APA230L under 2000g



Selection between APA230L & APA500L

A c t u a t o r o p e r a t i o n c u r v e

-1,00

-0,50

0,00

0,50

1,00

-7 -5 -3 -1 1 3 5 7 9 11F l a p a n g l e ( ° )

Aer odynamic HingeMoment Envelope f orps i=0°-360°

H i n g e m o m e n t ( N m )

U = 0 V

U = 1 8 0 V

M +-7°0°+11°

Uppe r Sur f a c e

A P A 5 0 0 L

A P A 2 3 0 L

B loc king Mome nt

B loc king Mome nt

⇒ Selection of the APA500L for the aerodynamic test because of better performances



ONERA S3MA wind tunnel tests set-up

Accelerometers on flap and airfoil

Calibration on the model in the wind tunnel



ONERA S3MA wind tunnel tests results

Flap deflection versus Input Control Voltage (at Mach=0.3)


ONERA S3MA wind tunnel tests results

Max Flap Deflections versus Wing Incidence (at Mach=0.3)

-8

-6

-4

-2

0

2

4

6

8

10

-2 0 2 4 6

Wi ng i nci dence ( °)

F l a p a n g l e ( ° )Ri ght f l ap angl e

Cent r al f l ap angl e

Lef t f l ap angl e



New actuator APA750XL designed for ONERAStroke = 1150µmForce = 920NEnergy to weight : 441mJ/kg

APA750XL prototype for ONERA (scale 1 flap) from CEDRAT TECHNOLOGIES



ONERA conclusion & perspectivesNo breakdown & Encouraging performances

ONERA perspectivesImprovement of the flap mechanism foreseen to get less than 8% loss of stroke @2300gNew centrifugal tests of APA500L flap plannedScale 1 tests using the new actuator APA750XLActuator improvements using composite shells



Piezo Actuators: Application for Air Plane Flap Control

Flap control of Air plane mock-up (AWIATOR)reduction of slipstream of Airbus A340

need for specific flat actuatorsstroke : 500µmforce : 700Nheight : 60mmthickness : 9mm


Flap control of Air plane mock-up (AWIATOR)ONERA pre-selection : APA500L

stroke u= 500µmforce F= 560N => Pb / 700Nheight : 55mmthickness : 10mm => Pb / 9mmLength : 145mm

Standard APA500L-SG from CEDRAT TECHNOLOGIES



CEDRAT offer to ONERA : an APA500L-SV Customised product starting from the APA500L (SV = special version) Reduction of thickness : 10mm => 9mmOptimisation of the Force F, keeping constant the stroke u and the same PZT amount Reduction of capability to withstand external vibrations, noting that vibrations are smaller in this application than in space launching conditions



Results on APA500L-SV developed for ONERAActuator APA500L APA500L-SV GainThickness 10mm 9mm -9%Mass m 0.20 kg 0.17 kg -15% Stroke u 500 µm 560 µm +11%Force F 570 N 778 N +36%Emec=F.u/4 0.071 J 0.109 J +53%Emec/m 0.35 J/kg 0.64 J/kg +82%



ConclusionsAPA500L-SV is fully compliant with ONERA needsStandard APAs are designed for Space need and are not optimised for all applications (even if they possess highest power density on the market)APAs can be optimised for other needs than space, such as Aircraft applications, leading to significant improvements in energy densities



Application for Mini Helicoptere

Mufly project

Micro APA APAµXS for

wing orientation (0.2gr)

Mini BDLC motor for wing rotation

(3gr)


Piezo Actuators & Electronics: Application for proportional valves

Valve for micro thrusters : Implementation in a cold gas micro propulsion system


Valve for micro thrustersCold gas (Nitrogen)APA200M actuator placed outside the gas

Proportional Piezo Valve from CEDRAT TECHNOLOGIES



Valve for micro thrusters : Results

Flow control in open loop Flow control with a feedback loop



Piezo Actuators : Application for Aircraft Hydraulic jacks

Piezo-based EHA (Electro Hydrostatic Actuators)R&D works performed in co-operation with SABCA, ZFL, ALENIA, SAAB, ZIP ...Goal : Improving EHA with smart actuators :

piezoelectrics actuators piezomagnetics (biased magnetostrictives)

Expected improvementsMassPower consumption Bandwidth


Piezo-based EHA (Electro Hydrostatic Actuators)1 hydraulic jack2 actuated valves1 actuated pump1 accumulator(not shown)



Piezo-based EHA (Electro Hydrostatic Actuators)

Piezoelectric or magnetostrictive Valves & Pump for an EHA prototype designed by CEDRAT TECHNOLOGIES



Valve test bench

Flow meter

Pressure sensors

Output Input

Piezo

Valve

No leakage at 220 bars in closed position.



Valve resultsType Normally closedActuator APA500LPiston stroke 460 µmMaximal working pressure 100 barsMaxi. tested working freq. 400 Hz (power supply limitation)Max. theoretical working freq. 1000 HzOpen flow rate > 2.5 l/min.



Active Control of Fluids: Piezo Injectors for Automotive

short time responsecompact structurepotential for low cost

small piezo ceramic amountfew simple parts

Car Injectors based on an APA, according to

C.R.Fiat


Pneumatic Valve Prototype (designed by Cedrat Technologies ) based on the APA100S (Courtesy of ENS)

Active Control of Fluids:Proportional Pneumatic Valves


Piezo Actuators : Application for sound generation

Sound generator for urban water pipes localisationAPA230L + back mass + front membranepo < 10BarFr = 500 HzV < 10Vrms @Fru = 230µm @Frufront = 110µm @Fr

MADE Water Tracker sound emitter

Transducer based on APA230L


Active Control of Vibrations

Complete close loop electronics including :a linear amplifier a sensor of displacement, speed, accel., force ...a controler : PI, PID, Feed forward, Force feed back ….

in order to drive & control the actuator(s)


Active Control of Vibration: Damping of a truss by active tendons

Space Truss of ULB using an active tendon concept based on APA100Ms for active damping (Courtesy of Micromega Dynamics & ULB & ESA)

Truss vibration level after a shock excitation, without control (red curve)

& with control (blue curve)


Active Control of Vibration : 6 dof Stewart Isolation platform

Hexapod based on 6 APA50S

Courtesy of ULB & Micromega Dynamics


Active Control of Vibration : 6 dof Stewart Isolation platform

Experimental results

Courtesy of ULB & Micromega Dynamics


R&D works supported by CNES / ApplicationsSpace Telescope mirror, Space fine instrumentsAircraft embedded cameras

New Objectives for the electronics : 2 functionsMicro-positioning of a loadIsolation of the load from micro-vibrations

Electronics for Piezo Actuators:Micro-Positioning & Damping

Frequency (Hz)40Hz5Hz

Micro vibration IsolationPosition


Electronics for Piezo Actuators :Micro-Positioning & Damping

Set-up listAPA120ML actuator : load positioning&damping‘FB-LA Space’ electronics : driving the APAStrain Gage & Capacitive Sensors : position sensingAccelerometers : vibration sensingServo controller : closed loop controlLarge Magnetostrictive Actuator : Excitation



Set-up view

Excitator APA120ML Dummy load Electronics


Electronics for Piezo Actuators :Micro-Positioning & Damping

Closed loop

Pdrift

Préf Piezoε

K(p)

F(p) A(p) D(p)

H(p)

K1(p)H1(p)F1(p)

D(p), the piezo+load transfer function,A(p), the power amplification transfer function,F(p), the position corrector function,H(p), the low pass filter transfer function,

K(p), the position sensor transfer function,K1(p), the vibration sensor transfer function,H1(p), the filter of the control loop,F1(p), the vibration corrector function



Measured performances-40dB/decade roll off, the cut off frequency close to 50Hz,the over shoot 5dB@50Hz,the maximum attenuation : 10 dB

-14-12

-10

-8

-6

-4-2

0

2

46

0 50 100 150 200

Frequency (Hz)

Atte

nuat

ion

(dB

)


Active Control of Vibration: One axis flexure beam / Rossignol Ski

Control OFF Control ON Ski Rossignol


Active Tool Control:Oval Piston Machining

Courtesy of Entech (SP)PPA80L-SG


Courtesy of Entech (SP)

PPA80L + OEM LA75B inc. PI controler

C = 26 µF ; Imax = 1.2 A

Tool mass = 1 kg

Peak Amplitude vs frequency

Displacement = 70 µm @ 100 Hz

Active Tool Control:Oval Piston Machining


Active Control of Vibrations : One axis tool controlin machining

Mechanical structure

Chatter vib.

Piezo actuator

Force sensor

Guiding membrane

Tool holder

Elastic actuator pre-stress

Tool caseActuated sleeve

VDI-3425interface

Tool interface

cutting

feed

passive

Piezo actuator

Force sensor

Guiding membrane

Tool holder

Elastic actuator pre-stress

Tool caseActuated sleeve

VDI-3425interface

Tool interface

cutting

feed

passivecutting

feed

passive

mag

nitu

de [m

/s2 ]

0 500 1000 1500

Ha/38251 © IFW

cutting force direction

passive force direction6

43

7

5

210

frequency [Hz]

mag

nitu

de [m

/s2 ]

0 500 1000 1500

Ha/38251 © IFW

cutting force direction

passive force direction6

43

7

5

210

6

43

7

5

210

frequency [Hz]

Cooperation IFW - Cedrat (ACTUATOR 2004)


Active Control of Vibrations : One axis tool control in machining

Control by force feedback

forcesensor

actuator chargeamplif ier

Q

actuatoramplif ier

analogueintegrator

U

UU

Fd

Fp

Q

F

highpassfilter

~__+-

U

forcesensor

actuator chargeamplif ier

Q

actuatoramplif ier

analogueintegrator

U

UU

Fd

Fp

Q

F

highpassfilter

~__~__+-

U


Active Control of Vibrations : One axis tool controlin machining

Control by force feedback

Mag

nitu

de g

/N [d

B]

Frequency [Hz]

Ha/38253 © IFW-80

-40

-70

-60

-50

-74

-66

-56

-46

0 1024500200 700

Active damping off

Active damping onMag

nitu

de g

/N [d

B]

Frequency [Hz]

Ha/38253 © IFW-80

-40

-70

-60

-50

-74

-66

-56

-46

0 1024500200 700

Active damping off

Active damping onIFW - Cedrat


Active damping of Vibration of Rossignol Ski

Application : Launched Kilometer SkiVibration level of the Ski tip : 8cm pk-pkDesign configuration : APA120ML + pulling rod

Dynamic displacement divided : <120µm to the actuatorDynamic force transmitted < 1200N to the actuator

LK Ski of SKI Rossignol equipped with APA120ML for active damping


Active damping of Vibration of Rossignol Ski

Application : Launched Kilometer SkiFEM analysis to get Eq circuit Matlab simulinkTest results on snow : 32bB damping / 1st modeCedrat design patented by Rossignol


Other Machine Tools

PDP Glass cutting assistanceWire bondingLCD screen alignementChip testing on wafersActive damping on tools

APA100SCourtesy of Kammrath & Weiss


Telecom: stretching fibre

Active Fibber Bragg Gratings for DWDMTunable Laser Optical switchFibber alignment

APA50S + FBG for laser tuning


Electrical Power Generator



Basic configuration



APA-based Proof-massAPA400M_MD + MassMesema project end user :

EADS, Eurocopter

Out power & Effciency accounting for the electronics

APA400M proof mass



References Unit GPA60SM

Notespreliminary

datainput mechanical energy mJ 2Displacement µm pk-pk 11Output electrical energy mJ 0.1Load impedance kOhm 1.5Min. Voltage V 1.8Time to maintain the voltage ms 45

Courtesy of LEGRAND

Wireless switch based on APA60SM


Synthesis: typology of applications of Piezo products

Position controlOptical control Shape controlDriving control Reduction of noise, vibration Vibration controlFluid control Generation of noise, vibration Energy harvesting

1day piezo training 2010

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