piezoelectric devices for vibration energy harvesting devices for vibration energy harvesting...

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Piezoelectric Devices for Vibration Energy Harvesting

Vittorio FerrariDip. Ingegneria dell’InformazioneUniversità di Brescia - ITALY

NiPS Summer School 2010Energy Harvesting at micro and nanoscale

V.Ferrari Summer School: Energy Harvesting at micro and nanoscale, Aug. 1-6, 2010

Sensors and Electronic Instrumentation Laboratory

Activity:Sensors and instrumentation systemsAnalog and digital electronic circuits and systems for:

sensor interfacingsensor communication and networking measurement applications

Sensors, MicroSystems and Electronic Interfaces:Piezoelectric transducers, acoustic-wave and resonant microsensorsMEMS sensors and systemsContactless sensorsElectronic interfaces for sensor signalsEnergy harvesting for autonomous sensors

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ContentsIntroductionPiezoelectric effect for energy harvestingExamples of piezoelectric energy harvestersFrom “raw” harvested energy to “usable” power supplyPrototypes of battery-less autonomous sensor modulesConclusions



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Sensor Systems

network connectivity

communication capability

electronic board

microsystem/MEMS

sensor element

Sensor elements…into microsystems/MEMS…into packaged electronic modules …with wireless communication capability…and network connectivity


Systems of Systems



electronic board

microsystem/MEMS

sensor element





electronic boardelectronic board

microsystem/MEMSmicrosystem/MEMS

sensor elementsensor

element

“Pervasive sensing and computing”“Ambient intelligence”“The internet of things”



electronic board

microsystem/MEMS

sensor element








element



electronic board

microsystem/MEMS

sensor element








element

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General Architecture of a RF Sensor

Information flow requires exchange of energyAssuming the external readout unit is energeticallyself-sufficient …

the sensor needs power supply

sensor

information

external readout unit

environment/ system/ process

RF link


sensor

information



RF link

Power Supply Options: #1

Power supply internal to the sensor (on-board):BatteriesFuel cells…

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sensor

information



RF link


Power supplied by the external readout unit:“Passive” RFId devices (class 1 and 2)Passive telemetric sensorsChipless RFId sensors


sensor

information



RF link


Power extracted (harvested) from the surrounding ambient

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Present, FreePlay, wind-up radio.

Energy from Ambient: the idea is not new

Water- and windmills. 1770, A.L. Perrelet, self-winding watch.

1930, Jaeger-LeCoultre, Atmos clock powered by thermal fluctuations.

Present, Eolic generators.1956, Zenith, battery-less ultrasound remote.

Present, Motorola PVOT hand-crank phone.


Energy Harvesting (Scavenging)Principle: Energy is extracted from the surroundings

Surroundings

Energy

CONDITIONING LOADElectrical domain

CONVERSION

The load can be: - Electronic circuits and devices- Sensors with wireless communication

→ Autonomous Sensors- …

EnvironmentHuman body

Radiant KineticThermal

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Radiant Energy

Radiant Energy HarvestingPrinciple: Energy is extracted from the surroundings

Energy


CONVERSION

SolarRadio Frequency


Thermal HarvestingPrinciple: Energy is extracted from the surroundings

Energy


CONVERSION

thermal gradients

Thermal Energy

Thermoelectric effectPyroelectric effect

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Mechanical Energy

Mechanical Energy HarvestingPrinciple: Energy is extracted from the surroundings

Energy


CONVERSION


MechanoElectrical Conversion

Magnetic induction conversion

Electrostatic conversion

Piezoelectric conversion

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Magnetic induction conversion:

NightStar flashlamp







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www.enocean.com






Electrostatic conversion:

UCB, Berkeley, USA

UCB, Berkeley, USA

MIT, Boston, USA

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NEC -Tokin, Japan





Piezoelectric conversion:

F

F

31 mode33 mode

q

+

-

q

+

-

MIT, Boston, USA


Mechanical Energy HarvestingDirect deformation (strain)

E.g. piezoelectric fiber composites

Impact & transient loadsE.g. piezoelectric thin plates

VibrationsSeismic-mass inertial system

THUNDER®, Face International Corp, USA.

(approximated for piezoelectric converters) C.B. Williams, R.B. Yates,, Sens. Actuat. A 52, 8-11 (1996).

Unfavorable scaling with reducing dimensions

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The Piezoelectric EffectDiscovered in 1880-81 by the Curie brothersProperty of certain materials in which:

a mechanical stress induces an electric charge (direct effect)an electric field develops a mechanical strain (converse effect)

The effect is linear, as opposed to electrostriction

Direct effect:detection

Converse effect:generation

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Applications of PiezoelectricitySonic and ultrasonic wave generation and detection:

Sensors and transducersFilters and resonators

ElectroMechanical & MechanoElectrical conversion:ActuatorsTransformersGas ignitersMotors and machining toolsNebulizers and humidifiersEnergy harvesters

Quartz Piezofilm (PVDF)


Crystal Structure and PropertiesThe degree of structural symmetry affects the piezo and pyro properties of the material

21 non centrosyimmetrical

...

11 centrosymmetrical

32 classes(point groups)

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20 piezoelectric(stress-induced polarization)

quartz

...turmaline



Y

Si

O

X

Z

+

-

+

-

+

-

- - - -X

- - - -

++ +++ + + +

+-

+-

+

-

X

-- - -----

++++++++

+-

+-

+

-

Piezoelectricity in Quartz X axis: electrical axisY axis: mechanical axisZ axis: optical axis

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quartz

...turmaline

10 pyroelectric(polar with spontaneous polarization)

AlN

...ZnO







quartz

...turmaline

10 pyroelectric(polar with spontaneous polarization)

ferroelectric(pyroelectric with electrically-reversible polarization)

AlN

...ZnO

BaTiO3(PZT)

...PbZr/TiO3


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FerroelectricsMaterials in this class exhibit the strongest piezo e pyroeffects Monocrystals (e.g. Rochelle salt) or Polycrystals (e.g. PZT ceramics)

Dipoles are arranged in domains Above TCurie the domains are randomly orientedPoling:

an electric field is applied to orient the domains and set up a permanent polarization


Lead Zirconate Titanate (PZT)Ferroelectric polycrystalline ceramic made by a solid solution of two perovskite type oxides (ABO3):

PbZrO3PbTiO3

Above Curie temperature :cubic, nonpolar

Below Curie temperature :rhombohedral/tetragonal, polar

Large piezoelectric andpyroelectric effectsHigh coupling coefficientVarious compositions (PZT-4, PZT-5, PZT-5H Navy,…)Other commercial name: PXE

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Basics of Piezoelectricity (1)Interaction between Electrical and Mechanical domains described by linear piezoelectric constitutive equationsSeveral options depending on the chosen EM variablesIn the monodimensional simplified hypothesis:

⎩⎨⎧

ε+=

+=

EdTDdETsST

E

⎩⎨⎧

ε+−=

−=S

D

DhSEhDScT

⎩⎨⎧

ε+−=

+=T

D

DgTEgDTsS

⎩⎨⎧

ε+=

−=

EeSDeEScTS

E S = strain [m/m]

T = stress [N/m2]D = dielectric displacement [C/m2]E = electric field [V/m]

d, e, g, h = piezoelectric constants

[ ] [ ][ ] [ ]

[ ] [ ][ ] [ ]

heccdegcehhsdg

dcheesgd

EDST

DS

DT

ES

ET

+=+ε=ε===ε=

===ε====ε=

===ε=

; V/mN/C

Vm/Nm2/C

N/mVC/m2

m/VC/N

11

sX = elastic compliance [m2/N] @ constant X

εX = dielectric permittivity [F/m] @ constant X

cX =1/sX = elastic stiffness [N/m2] @ constant X


Examples of Piezoelectric Materials

TP238, Matroc Electroceramics.

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Making reference, for instance, to the formulation:

Piezoelectricity Modeling

… passing to global variables force F, displacement X, voltage V, and current I, an equivalent-circuit representation can be drawn:

⎩⎨⎧

ε+=

−=

EeSDeEScTS

E

F

jωX

V

I

C S

E 1 / k

l V eA

l jωX eA

l

l

A

F, X

V

I

⎪⎪⎩

⎪⎪⎨

⎧

ω+ω=

−=⇒

⎪⎪⎩

⎪⎪⎨

⎧

ε+=

−=

VCjXjl

eAI

Vl

eAXkF

VlAX

leAQ

Vl

eAXlAcF

S

E

S

E

F

jωX

V

I

C S

E 1 / k

α : 1

l eA l

α =

* DC-responding ideal transformer

*


⎪⎪⎩

⎪⎪⎨

⎧

ω+ω=

−=

VCjXjl

eAI

Vl

eAXkF

S

E

V

I

C S

Electrical capacitor

F

jωX E 1 / k

Mechanical spring

F

jωX E 1 / k V

I

C

S

α : 1

Piezoelectric element! Spring constant k(capacitance C) depends on electrical (mechanical) boundary conditions

Spring constant:EDE kkeh

lAk

XF

>=+=EkXF

=Electrically shorted

Electrically opened

Capacitance:STS CCed

lAC

VjI

>=+=ω

SCVj

I=

ωMechanically clamped

Mechanically free

Piezoelectricity Modeling

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Electro-Mechanical Coupling

The energy transfer between the EM domains can be expressed by the electromechanical coupling factor κ:

E

M

M

E

)energysupplied ()energystored (

)energysupplied ()energystored (2 ==κ

F

jωX E 1 / k V

I

C

S

α : 1

By reflecting the corresponding impedance through the transformer ports it results:

TESDSE sd

ce

Ck ε=

ε=

+αα

=κ22

2

22


Power Conversion from Vibrationsvibrating structure x

A vibrating structure is assumed to move with dynamic displacement x(t)with respect to a fixed reference

vibrating structure x

piezoelectric element

V I

m

A seismic equipment is used to convert the displacement x into an inertia force acting on the proof mass mThis in turn causes a relative displacement y(t) between the structure and the proof mass generating a stress in the piezo

vibrating structure

m

k r z

x

y

piezo

Z L A lumped-element model can be used to describe the system around resonance

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Piezoelectric Power Conversion

vibrating structure

m

k r z

x

y

piezo

Z L jωY

E 1 / k

V

I C

S

α : 1

m

F y r

1 / k

Z L F y mX ω 2 = -

In general, a maximum exists to the power that can be extracted by an ideal converterThis power limit occurs at resonance and for a converter with a purely resistive mechanical impedance adapted to r:

ram

rXmP x

88

2222

lim ==&&



vibrating structure

m

k r z

x

y

piezo

Z L jωY

E 1 / k

V

I C

S

α : 1

m

F y r

1 / k

Z L F y mX ω 2 = -

r

at resonance

In general, a maximum exists to the power that can be extracted by an ideal converterThis power limit occurs at resonance and for a converter with a purely resistive mechanical impedance adapted to r:

ram

rXmP x

88

2222

lim ==&& Same results as in:

C.B. Williams, R.B. Yates,, Sens. Actuat. A 52, 8-11 (1996).

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vibrating structure

m

k r z

x

y

piezo

Z L jωY

E 1 / k

V

I C

S

α : 1

m

F y r

1 / k

Z L F y mX ω 2 = -

Assuming ZL = R, the transfer function between Fy and Y is:

[ ]ES

S

y kkrjmRCjRjRCj

FY

++ω+ω−ω++αωω+

=22 )1(

1

[ ]ESyy kkrjmRCjRj

jYI

FY

FI

++ω+ω−ω++αωωα

==22 )1(

The transfer function between Fy and I is then:

V.Ferrari Summer School: Energy Harvesting at micro and nanoscale, Aug. 1-6, 2010R.D’hulst, J.Driesen, IEEE, 2556-2562 (2008).

[ ]

2

22

22

)1(22 ES

yE kkrjmRCjRj

jFRIRP

++ω+ω−ω++αωωα

==

The electrical power PE on a resistive load R is:

Popt is a function of frequency that maximizes at about the “short-circuit” natural frequency:

mkk E

sc+

=ω

PE is a function of R that maximizes to Popt at the optimal resistive load Ropt

Popt tends to Plim with increasing the electromechanical coupling factor κ


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vibrating structure

m

k r z

x

y

piezo

Z L jωY

E 1 / k

V

I C

S

α : 1

m

F y r

1 / k

Z L F y mX ω 2 = -

The energy balance gives:

dtyVdtyrykkymdtyF Ey &&&& ∫∫∫ α++++= 222 )(

21

21

The transferred energy is in turn:

dtVIVCdtyV S ∫∫ +=α 2

21

&

Elastic energy

Kinetic energy

Dissipated energy

Transferred energy

Electrostatic energy

Load energy



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Mechanical Energy from Vibrations


Nanoscale Energy ConvertersA single piezoelectric nanowire of BaTiO3excited by vibrations generates current

M.F. Yu et al., ScienceDaily, 28 September 2007.

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Nanoscale Energy ConvertersPiezoelectric nanowires of ZnO deflected by an AFM tip or excited by ultrasound waves generate current

Z.L. Wang et al., SPIE Newsroom, 25 March 2008.


Nanoscale Energy Converters

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Nanoscale Energy Converters


Microscale Energy ConvertersPiezoelectric MEMS under typical excitations generate in the order of 1 µW

D. Shen et al., Sens. Actuat. A 154, 103-108 (2009). D. Jeon et al., Sens. Actuat. A 122, 16-22 (2005).

Resonant frequency = 13.9 kHz.Resonant frequency = 184 Hz.

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Application to TPMSNext generation Tire-Pressure Monitor Systems (TPMS) will dismiss batteries and rely on energy harvesting MEMS converters can find their way in the field


Macroscale Energy Converters:commercial devices

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0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200f [Hz]

acce

lera

tion

[g]

L

T

W

W = 15mmL = 40mmT = 500µm

PZT: Piezokeramika 856d33 = 590pC/Nd31 = -260pC/Nεr = 4000

CP=151pF RP=363MΩ (A = 13.6V)

Resistive load RL

Capacitive load CL

02468

101214

0 1000 2000 3000 4000CL [pF]

VL

[V]

ComputedExperimental

0

0.4

0.8

1.2

1.6

2

0 1000 2000 3000 4000CL [pF]

PL

[ µW

]


0

0.5

1

1.5

2

2.5

0 20 40 60 80RL (MΩ)

PL

[ µW

]


0

2

4

6

8

10

12

0 20 40 60 80RL [MΩ]

VL

[V]


PIEZOELECTRIC LAYER

V i BEAM

F u

Macroscale Energy Converter

M.Ferrari et al., IEEE Trans. Instrum. Meas. 55, 2096-2101 (2006).


W

LC

LP

W = 5 mmLC = 35 mmLP = 30 mm

L

W

W = 18 mmL = 31 mmFilm Thickness = 125 µm

Film Properties

parameter BULK CERAMIC THICK FILM rel. dielectric const. εΤ/εo 4100 100 ± 10density ρ [g/cm3] 7.5 4 ± 0.1

Alumina substrate Harmonic steel substrate

-3

-2

-1

0

1

2

3

-15 -10 -5 0 5 10 15E [MV/m]

D [ µ

C/c

m2 ] -15

0

15

0 5 10 15 20time [ms]

E [M

V/m

]

@ room temperature

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Limitations with Resonant Converters

This is problematic to guarantee with frequency-varying vibrations and is considerably sub-optimal for wideband noise frequency f 0

frequency f 0

Lowering the converter quality factor increases the bandwidth, but worsens the peak response

Best harvesting effectiveness is when the converter operates at mechanical resonance

frequency f 0


Frequency Up-ConversionMechanical methods have been proposed to up-shift the vibration frequency where the converter is more responsive

D.G. Lee et al., Proc. Transducers & Eurosensors ‘07, 871-674 (2007).

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Frequency TuningAn adjustable axial tension changes the beam resonant frequency

The method is not self adaptiveElectrical automatic tuning can be used, but this requires extra energy

C. Eichhorn, F. Goldschmidtboeing, P. Woias, Proc. PowerMEMS 2008+microEMS2008 (2008).


MultiFrequency Converter ArrayMultiple converters combined to obtain a wider equivalent bandwidth:

-80

-70

-60

-50

-40

-30

-20

-10

0

0 100 200 300 400f [Hz]

Vo/V

i [dB

]

3 1 2

MFCA on the vibration exciter (shaker).

500 ? m500 ? m500 ? m500 µm

Silicon MEMS with PZT films:Design: University of BresciaFabrication: CNM, Barcelona, SpainIn collaboration with:

M. Ferrari et al., Sens. Actuat. A 142, 329-335 (2008).

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Multi-Frequency Converter ArrayMEMS Implementation

PZT low-curing-temperature filmIDT electrodes (d33 mode)Embedded piezoresistors

M.Guizzetti, PhD Thesis, University of Brescia (2010).


Multiple-Converter System Multiple converters are coupled into a single structure

Z. Chew, L. Li, Sens. Actuat. A 162, 62-92 (2010).

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Nonlinear Approach: TheoryBistability is exploited to amplify displacement induced by random vibrations due to stochastic resonance

M. Ferrari et al., Sens. Actuat. A, in press.

For decreasing values of d:Quasi linearityNonlinearity Bistability


Nonlinear Approach: ExperimentBimorph cantilever beam fabricated with:

Stainless steelLow-curing-temperature PZT films


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Nonlinear Approach: ResultsBehaviour in agreement with theory:



Nonlinear Single-Magnet ConverterA ferromagnetic substrate is coupled to a fixed magnet

M. Ferrari et al., Eurosensors 2010 and Procedia Engineering, in press.

-8-7-6-5-4-3-2-1012

14 14.2 14.4 14.6 14.8 15Time [s]

Tip

disp

lace

men

t x [m

m]

-3-2-101234567

Out

put v

olta

ge V

P [V

]Stable states

x d

Permanentmagnet

Input mechanical excitation

N S

VP

PZT film

FA

FAh

Ferromagnetic cantilever

t

Fel

decreasing d

3xxFAv βα −= kxFel −= 42

42)()( xxkxU βα

−−

=

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Average power into a resistive load RL:Sinusoidal regime at f0

Power Supplied to a Resistive Load

The power spectral density SVP( f ), commonly used as an indicator of signal power, is not sufficient to describe PThe weighting function H ( f ) should be also considered

Broadband between f1 and f2

∫∫ =π+

π=

2

1

2

1

1)()(121

2)( 22 f

f LV

f

f LLP

LPV df

RfHfSdf

RRfCjRfCjfSP

PP

V P

C P R L

I L

V L

L

Popt

CR

L

P

LP

LP

RVP

RV

RCfjRCfjP

PL 421

2 2

1

22

0

0

0

=⎯⎯⎯ →⎯π+

π=

ω=

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“Usable” Power in ElectronicsA large power into a resistive load does not necessarily mean a correspondingly high usable power

AC/DC converters, i.e. rectifier circuits, are required They in turn introduce nonidealities and losses, and pose requirements on the voltage levels to operate properly

This is because power into a resistive load is associated to AC voltage (current)Electronic circuits and microsystems usually need DC power supply


AC/DC Circuits in Sinusoidal StateAC and DC driving of a resistive load:

AC-driven load

DC-driven load

Synchronized Switch Harvesting on Inductor (SSHI) technique:

D.Guyomar et al., IEEE Trans. on UFFC, 52, 584-595 (2005).

Voltage has the same sign of velocity

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SSHI for AC load driving:

SSHI for DC load driving:

AC/DC Circuits in Sinusoidal State



Power comparison under weak EM coupling

AC/DC Circuits in Sinusoidal State


Power comparison versus the EM coupling

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Intermittent Operation

Surroundings

Energy


CONVERSION

CONVERSION STORAGE SWITCHING LOAD

Intermittent operation

If available power is insufficient for continuous supply of the system

Differences with respect to load driven under sinusoidal steady state arise when energy must be accumulated



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RF Receiver

VR+

VR-

VP VC

PiezoelectricConverter

Rectifier andstorage capacitor

Sensing andswitching

Voltage regulator

Cb

RF Transmitter

DC

Autonomous Module with RF LinkThe converted energy is stored and intermittently used to trigger a radio-frequency (RF) transmitter

vibrations

How a sensor can be inserted into the system ? ...considering that:

the power budget is quite restrictivevoltage and current levels are poorly definedsuitable resolution should be granted

! No battery, no internal power sources !


Autonomous Sensor ModuleThe converted energy is stored and intermittently used to trigger a radio-frequency (RF) transmitter

vibrations

sensor

The sensor (R or C) is inserted into an oscillatorThe oscillator frequency modulates the envelope of the RF carrierThe measurement information is carried in the time domain

RF Receiver

VR+

VR-

VP VC




Voltage regulator

Cb

Oscillator

RF Transmitter

DC

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SSOSC CRR

f)2(

44.1

1 +=

RF Receiver

VR+

VR-

VP VC




Voltage regulator

Cb

Oscillator

RF Transmitter

DC

vibrationssensor

Resolution: CCkHz

HzS

RT

T °=°

== 023.03.1303σ

Sensitivity: CkHzST °≈ 3.1

Hz10≈σStandard deviation (30 repetitions):

NTC Epcos K164/10k

Thermistor response curve

Autonomous Temperature Sensor


Autonomous Temperature Sensor

Piezo bimorphSignal conditioning and RF transmission

Energy conditioning and storage

Piezoelectric vibration-powered module for temperature sensing and transmission of the reading over a RF link

vibrations

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Autonomous Multi-Sensor ModuleThe piezo harvester powers a module comprising 2 sensorsEnergy is sequentially switched between the sensorsSignals are transmitted in time multiplexing

Cb

RF Transmitter

VC

Piezoelectric converter

Rectifier and storage capacitor

Sensing and switching

Voltage regulator

Mechanical Vibrations

SENSOR 2 Impedance Controlled Oscillator 2

SENSOR 1 Monostable

DC

RF Receiver

Impedance Controlled Oscillator 1

SPDT switch


The piezo harvester powers a module comprising 2 sensorsEnergy is sequentially switched between the sensorsSignals are transmitted in time multiplexing

Cb

RF Transmitter

VC

Piezoelectric converter

Rectifier and storage capacitor

Sensing and switching

Voltage regulator


SENSOR 2 Impedance Controlled Oscillator 2

SENSOR 1 Monostable

DC

RF Receiver

Impedance Controlled Oscillator 1

SPDT switch

0

1

2

3

4

5

6

7

8

0 2 4 6 8 10

Time [ms]

Vc,V

RX

[V]

-1.6

-1.3

-1

-0.7

-0.4

-0.1

0.2

0.5

0.8

A.U

.

Autonomous Multi-Sensor Module

A digital ID-code can also be transmitted for module tagging and tracking

M. Ferrari et al., Smart Mater. Struct., 18, 085023 (2009).

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Multi-Frequency Converter ArrayMultiple differently-tuned converters combined to obtain a wider equivalent bandwidth:

Cb

C

C

C

Rp1

Cp1

D

D

D

D

D

D

Rp3

Cp3

Rp2

Cp2

Vp2

Vp1

Vp3

D1

D2

D3

V1

V2

V3

-80

-70

-60

-50

-40

-30

-20

-10

0

0 100 200 300 400f [Hz]

Vo/V

i [dB

]

31 2

Measured frequency response.

m3

m2

m1 V2

V3

Conductive base

V1



Multi-Frequency Converter Array:experimental results

Wideband excitation:

0

5

10

15

20

25

0 10 20 30 40t [s]

V Cb

[V] 0

0.5

1

1 2 3Cantilever

3

1

ALL

2

fa

fb

-15

-10

-5

0

5

10

0 20 40 60 80 100t [ms]

V [V

]

3

2

1

Measured open circuit voltagesof the three converters.

Measured voltage across the storage capacitor.


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Multi-Frequency Converter Array:experimental results

Wideband excitation:


SENSOR

Switched-Supply

Unit

MultiFrequency Converter Array

Impedance-Controlled Oscillator RF Transmitter

VOSC

Measured voltage across the storage capacitor.

0123456789

0 10 20 30t [s]

V Cb [

V]

2 ALL

tswitching

tswitching


Output Combinations in a MFCAParallel-like combination:

Rectified currents are fed to a single capacitor

m3

m2

m1 V2

V3

Conductive base

V1

I1 ICb

VP1

CP1

RP1 D

D C

VP2 D

D C

VP3 D

D C

Cb

CP2

RP2

CP3

RP3

VCb

V1

V2

V3

I2

I3

M. Ferrari et al., Proc. SENSORDEVICES-2010, (2010).

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Output Combinations in a MFCASeries-like combination:

Rectified voltages on different capacitors are summed

m3

m2

m1 V2

V3

Conductive base

V1

VP1

CP1

RP1 D

D C

VP2 D

D C

VP3 D

D C

Cb2

CP2

RP2

CP3

RP3 Cb3

Cb1

VCb

V1

V2

V3

VCb1

VCb2

VCb3



Output Combinations in a MFCAExperimental results:


Converter 1 Converter 2 Converter 3

VP (V

)

Series-like configuration

Parallel-like configuration

The series-like configuration reaches the threshold to trigger the RF transmissionIt is especially suitable for arrays of low-voltage MEMS converters

8/7/2010

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Final CommentsEnergy harvesting for sensors is a fast-growing area evolving from gadgets to enabling technology in such fields as:

Industrial control and automationTransport, automotive, avionicsPower plants & distributionStructural monitoringMedical and healthcareSecurity and military

University of Brescia is active in the field with: Applied research programsProjects in cooperation with industrial Partners

Università di Brescia:Acknowledgments

Michele GuizzettiDaniele MarioliEmanuele TonoliStefano Zaiba

Marco BaùSimone DalolaMarco DemoriMarco Ferrari

piezoelectric devices for vibration energy harvesting devices for vibration energy harvesting...

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