Vibration Energy Harvesting using Multi-Frequency and...

Vibration Energy Harvesting usingMulti-Frequency and Nonlinear

Piezoelectric ConvertersVittorio FerrariDepartment of Information EngineeringUniversity of Brescia - ITALY

Davide Alghisi Marco BaùSimone DalolaMarco Demori

Acknowledgments and credits to:

Marco Ferrari Michele GuizzettiDaniele MarioliEmanuele Tonoli

V.Ferrari London, March 28, 2012

ContentsIntroductionMulti-frequency piezoelectric harvester arraysNonlinear piezoelectric harvestersConclusions


vibrations

Vibration Energy Harvesting

Energy

CONDITIONING LOAD

Electrical domain

CONVERSION

The load can be sensors with wireless communication: → Autonomous Sensors

If available power is insufficient for continuous operation → Intermittent operation

PiezoelectricConverter

Rectifier andStorage element

Comparator andtriggered switch

Sensor andInterface electronics

RF Transmitter

Energy management

PiezoelectricConverter

Rectifier andStorage element

Comparator andtriggered switch

Sensor andInterface electronics

RF Transmitter

Energy management

vibrations1/15


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 = -

ram

rXmP x

88

2222

lim ==&&

A maximum exists to the power that can be extracted by an ideal converter, irrespective of the conversion principleThis power limit occurs at resonance and for a converter with a purely resistive mechanical impedance adapted to r:

leA

=αl

A

F, X

V

I


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 = -

r

at resonance

A maximum exists to the power that can be extracted by an ideal converter, irrespective of the conversion principleThis 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).


Limitations with Resonant Converters

This is problematic to guarantee with frequency-varying vibrations and is considerably sub-optimal for broadband and random vibrations 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


Broadband Approaches

Resonance tuningMulti-modal/multi-frequency harvestersFrequency-up conversion Nonlinear


Multi-Frequency Converter ArrayMultiple differently-tuned 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

]

31 2

Measured frequency response.

m3

m2

m1 V2

V3

Conductive base

V1

Bimorph commercial cantilevers (RS 285–784): 15 mm×1.5 mm×0.6 mm, m1 = 1.4 g, m2 = 0.7 g, m3 = 0.6 g.

Mechanical Vibrations

SENSOR

Switched-Supply

Unit

MultiFrequency Converter Array

Impedance-Controlled Oscillator RF Transmitter

VOSC

Measured voltage acrossthe storage capacitor.

0123456789

0 10 20 30t [s]

V Cb

[V]

2ALL

tswitching

tswitching

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


L

W

W = 18 mmL = 31 mmFilm Thickness = 125 µm

Screen-Printed Piezoelectric Films

parameter BULK CERAMIC THICK FILM rel. permittivity εΤ/εo 4100 100density ρ [g/cm3] 7.5 4.5 piezoelectric coeff. d33 [pC/N] 590 < 10

Alumina substrate

Harmonic steel substrate

Lead zirconate titanate (PZT) powder in polymeric binderCuring: (10 min @ 150°C)

Electrodes: Ag polymeric inkPoling: (10 min @ 4 MV/m @130°C)

W

LC

LP

W = 5 mmLC = 35 mmLP = 30 mm

W

LC

LPW

LC

LP

W = 5 mmLC = 35 mmLP = 30 mm

Top electrode (20µm)

Steel shim (200µm)

PZT (100µm)

Piezokeramica-APC 856 powder (soft material)


Steel Implementation of a MFCA

Open-circuit voltages @ 1 gpk acceleration

Converter 1 Converter 2 Converter 3

VP (V

)

Steel cantilevers (40 mm×5 mm×0.5 mm)Cured thickness of PZT film: 75 µmSeries bimorph configuration

Internal impedance:400 pF || 20 MΩ @ 100 Hz


Output Combinations in a MFCA

Parallel-like combination:Rectified currents are fed to a single capacitor

Series-like combination: Rectified voltages on different capacitors are summed

m 3

m 2

m 1 V 2

V 3

V 1

8/15


Output Combinations in a MFCA 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

The storage capacitor is charged prevalently by the converter with the highest instantaneous levelThe voltage is determined by the dominant converterUnder wideband excitation, all the converters contribute to shorten the charging time

R L

SW

9/15

Series

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

Each storage capacitor is charged by the corresponding converterThe voltage is given by the sum of the single voltagesInactive converters worsen energy transfer to the load due to charge redistribution upon switching

Parallel

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


Experimental Results on Steel MFCA

Converter 1 Converter 2 Converter 3

VP (V

)

Series-like configuration

Parallel-like configuration

The series-like configuration outputs a higher voltage at parity of excitationThe series-like configuration reaches the threshold to trigger the RF transmission

10/15M. Ferrari et al., Proc. SENSORDEVICES-2010, (2010).


MEMS Implementation of a MFCA

500 ? m500 ? m500 ? m500 µm

Design: University of BresciaFabrication: CNM, BarcelonaPZT paste: MEGGIT/Ferroperm

Screen-printed PZT filmIDT electrodes (d33 mode)


New Designs of MEMS MFCAsDesign: University of BresciaFabrication: CNM, Barcelona

BE-SOI process (10 mm × 10 mm) dieCantilever resonant frequencies: 4.5÷9 kHz - 3.5÷6.5 kHz

Array of straight and tapered cantilevers


Deposition of Piezoelectric Film

PZT paste: MEGGIT/Ferroperm

Sputtered Cr bottom electrode (tCr ≅ 0.5 µm) Screen-printed PZT film (tPZT ≅ 30 µm)

1 mm

1 mm


Top Electrode and PolingTop electrode: direct writing* of Ag polymeric inkPoling: 120 V @100°C, 10 min

* Manual artwork in the first prototype


Preliminary Results

-0.25-0.20-0.15-0.10-0.050.000.050.100.150.200.250.30

0 0.002 0.004 0.006 0.008Time [s]

Am

plitu

de [V

]

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

0.001 0.0012 0.0014 0.0016 0.0018 0.002Time [s]

Am

plitu

de [V

]

f = 9787 Hz-0.50-0.40-0.30-0.20-0.100.000.100.200.300.400.50

0 0.002 0.004 0.006 0.008Time [s]

Am

plitu

de [V

]

-0.50-0.40-0.30-0.20-0.100.000.100.200.300.400.50

0.001 0.0012 0.0014 0.0016 0.0018 0.002Time [s]

Am

plitu

de [V

]

f = 9298 Hz

Internal impedance @ 10 kHz:CP = 7÷10 pF; RP = 10 ÷30 MΩ

Impulse response tests:


Preliminary Results

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

-0.1 0.0 0.1 0.2 0.3 0.4 0.5Time [ms]

Volta

ge [V

]

R2_2R2_7R2_8Sinusoidal excitation of

the shaker (apk ≈ 1 g) Measurement of open-circuit voltage

Brüel & KjærPower amplifier

type 2719

Brüel & KjærVibration exciter

type 4808Agilent Waveform generator 332200A

LeCroyDSO LT374M


type 2719


type 2719


type 4808


type 4808Agilent Waveform generator 332200AAgilent Waveform

generator 332200A

LeCroyDSO LT374M

LeCroyDSO LT374M


Nonlinear ConverterBistability is exploited to amplify displacement induced by broadband vibrations

For decreasing values of d:Quasi linearityNonlinearity Bistability

Collaboration with Univ. Catania (S. Baglio) and Univ. Perugia (L. Gammaitoni)



Nonlinear Converter: ExperimentBimorph cantilever beam fabricated with:

Stainless steel substrate (thickness 200 µm)Low-curing-temperature PZT films

White-noise excitation filtered in the bandwidth 1-100 Hz



Nonlinear Converter: ResultsFor suitably low gap d, jumps occur between stable statesThe output voltage spectrum broadens and VPrms increases

-15

-10

-5

0

5

6 9 12 15Time [s]

Out

put v

olta

ge V

P [V

]

-10

-5

0

5

10

15

20

25

30

35

Bea

m d

efle

ctio

n [m

m]

Stable states

d = 2.5 mm

Out

put v

olta

ge V

P [V]

Tip

disp

lace

men

t x [m

m]

0.0001

0.001

0.01

0.1

1

10

1 10 100Frequency [Hz]

FFT

mod

ule

mag

nitu

de

25mm8mm5mm2.5mm

Distance d [mm] rms output voltage VPrms [V]25 4.27

5 6.112.5 7.99

arms = 0.3 g


Complex dynamics, see: S.C. Stanton et al., Physica D 239, 640-653 (2010).


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

-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

decreasing d

3xxFAv βα −= kxFel −= 42

42)()( xxkxU βα

−−

=


xd

Permanent magnet

Input mechanical excitation

N S

VP

PZT film

FA

FAh

Ferromagnetic cantilever

t

Fel


Mechanically-Induced BistabilityAn elastic beam compressed up to buckling shows bistability and double-well potentialPZT layers on the beam perform enhanced energy conversion from bending vibrations

F. Cottone et al., Smart Mater. Struct., 21, 035021 (2012).

Collaboration with Univ. Paris-Est (F. Cottone) and Univ. Perugia (L. Gammaitoni)


Experimental Results

PZT films screen printed on steel shims (f0 = 220 Hz)Shaker driven by Gaussian noise: autocorrelation time τ = 1 ms; acceleration 1÷3 grms

F. Cottone et al., Smart Mater. Struct., 21, 035021 (2012).

Collaboration with Univ. Paris-Est (F. Cottone) and Univ. Perugia (L. Gammaitoni)


Impact-Enhanced Multi-Beam EHTop piezo

beam

Bottom piezo beam

Driver beam (nonpiezo

high compliance)

Base excitation

PZT parallel bimorph on flexible steel

Beam dimensions: (45×19×0.58) mm3

Internal impedance @ 100Hz: CP = 270 nF; RP = 20 kΩ


Modelling: Noninteracting Beams

T, B and D beams operate independently as uncoupled oscillatorsThe outputs of T and B peak at the respective resonant frequenciesPoor response at low frequency

sY

E 1 / k

V

I

C

S

α : 1

m

F y

Z L

1/k R m

F y mX = 2 s

Bottom piezo (B)

Toppiezo (T)

Driver (D)

m

F y F

y mX ω 2 = -

1/k R m

sY

d T d B

y

D

y

T

y

B

x

sY

E 1 / k

V

I

C

S

α : 1

m

F y

Z L

1/k R m

F y mX = 2 s


Modelling: Interacting Beams

sY

E 1 / k

V

I

C

S

α : 1

m

F y

Z L

1/k R m

F DT

F y mX = 2 s

Bottom piezo (B)

Toppiezo (T)

Driver (D)

m

F y F

y mX ω 2 = -

1/k R m

sY

Assumptions:Impulsive impact of D on T/BZero engaging time No effect on D by T/B

( )⎪⎩

⎪⎨⎧

=

>=

0

0 0

,,

,,

BTDBDT

BTDBDT dyf

dF

&

d T d B

y

D

y

T

y

B

x

sY

E 1 / k

V

I

C

S

α : 1

m

F y

Z L

1/k R m

F DB

F y mX = 2 s

T/B voltage

off-resonance response

resonant decaying response


Experimental ResultsEH mounted on the shaker (Brüel & Kjær Vibration exciter type 4808)Swept-frequency excitation of the shaker (apk = 1 g @ 50 Hz)

0

1

2

3

4

5

6

7

8

9

10

0 25 50 75 100 125Frequency [Hz]

rms

volta

ge [V

]

Top

Bottom

Noninteracting beams

0

1

2

3

4

5

6

7

0 25 50 75 100 125Frequency [Hz]

rms

volta

ge [V

]

Top

Bottom

Quadratic sum

Interacting beams

Power on matched load: 1÷2 mW



Handheld EH intentionally shaken RF transmissions start after 10 to 15 s and repeat every few seconds under moderate to forcible shaking

RF Receiver Piezoelectric Converter

Rectifier and storage capacitor

Sensing and switching

Voltage regulator

Oscillator

RF Transmitter

DC

Temperature & angular position

sensors

433 MHz OOK

F. CeriniD. Roncali University of Brescia


Nonlinear MultiFrequency Array

N S Base

Beam 3

Beam 4

Piezo-ferromagnetic beam 1

Beam 2

MFCA and NL concepts merged into a compact configurationThe beams have different frequency responses

Parameter Beams 1, 3 Beams 2, 4 Steel thickness [µm] 200 100Tip mass no yesRes. frequency [Hz] 150 30

Electrodynamic shaker (Bruel & Kjaer 4808)

Converter

-1.5

-1

-0.5

0

0.5

1

1.5

0 5 10 15 20Time [s]

Acc

eler

atio

n [g

]

D. Alghisi et al., Proc. Conv. Nazionale Sensori, (2012).



-1

-0.5

0

0.5

1

1.5

0 0.1 0.2 0.3 0.4 0.5Time [s]

Am

plitu

de [V

]

MagnetNo magnet

Beam 1

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 0.1 0.2 0.3 0.4 0.5Time [s]

Am

plitu

de [V

]

MagnetNo magnet

Beam 2

-1

-0.5

0

0.5

1

1.5

2

0 0.1 0.2 0.3 0.4 0.5Time [s]

Am

plitu

de [V

]

MagnetNo magnet

Beam 3

-3

-2

-1

0

1

2

3

4

5

0 0.1 0.2 0.3 0.4 0.5Time [s]

Am

plitu

de [V

]

MagnetNo magnet

Beam 4

Typical responses with and without the magnet

Complex dynamics: quasi linear, nonlinear, bistable In all cases the magnet increases the rms output



Experimental ResultsTypical responses with and without the magnet

Complex dynamics: quasi linear, nonlinear, bistable In all cases the magnet increases the rms output

0

0.1

0.2

0.3

0.4

0.5

0 1 2 3 4 5Shaker driving level [V]

Out

put r

ms

ampl

itude

[V]

No Magnet

Magnet

Beam 1



Summing UpLinear MFCA harvesters: Bandwidth is not amplitude-sensitive

Good performances with multi-tone excitationsBandwidth is limited by the

resonances of the array elements

m 3

m 2

m 1 V 2

V 3

V 1

Nonlinear (NL) harvesters Bandwidth exceeds the range

of linear resonancesGood performances with random excitationsSufficient amplitude is needed for bandwidth expansion

NL- MFCA harvesters: Benefits of both classes Triggering of nonlinearity/bistability

by mutual interactions among converters and magnet(s)

N S


ConclusionsPiezoelectric elements and PZT thick films on different substrates investigated for energy harvestingPromising approaches studied for energy harvesting from broadbandvibrations:

Multi-Frequency converter arraysNonlinear convertersNonlinear converter arrays

m 3

m 2

m 1 V 2

V 3

V 1

T. Zawada and M. Guizzetti at MEGGIT-Ferroperm (DK):collaboration on the piezoelectric materials.P. Colombi at CSMT - Brescia for providing sputtering.MIUR:

Projects PRIN 20078ZCC92 (2008-2010); PRIN 2009KFLWJA (2011-2013).

Acknowledgments

Vibration Energy Harvesting using Multi-Frequency and...

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