nonlinear energy harvesting from vibrations - … floor tiles–there is much interest in harvesting...

1January 21, 2016

Vincenzo MarlettaDIEEI

University of Catania – Italy

Nonlinear Energy Harvesting from vibrations

2January 21, 2016

•The Energy Harvesting issue

•Non linear EH vs linear EH

•The proposed solutions & the Real LabScale Prototypes

The mechanical characterization

The electrical performances

Outline

3January 21, 2016

A WSN consists of:

Sensors and actuators

Microcontroller (μC)

Radio

Power

sim

ple

vis

ion

of

a W

SN n

od

es

THE ENERGY HARVESTING ISSUE

Development of solutions aimed at powering wireless nodes by exploiting the energyscavenged from their operating environment in order to reduce (or eliminate) the need ofperiodic replacements of batteries (environmentally friendly).

4January 21, 2016

Benefits:Maintenance free – no need to replace batteries

The technologies employed, variously convert

Solar radiation (PV)Wind Human power Body fluidsHeat differencesVibration or other movements RFVegetationUltravioletVisible light or Infrared …. more options coming along

to electricity (DC current).

WHAT IS ENERGY HARVESTING?

Requires expertise from all aspects of physics, including:

Energy capture (sporadic, irregular energy

rather than sinusoidal)

Energy storage

Metrology

Material science

Systems engineering

Energy harvesting or scavenging is a process that captures small amounts of energy that would otherwise be lost asheat, light, sound, vibration or movement, to provide electrical power for small electronic and electrical devices makingthem self-sufficient (replace batteries).

Improve efficiency – eg computing costs would be cut significantly if waste heat were harvested and used to helppower the computer

Enable new technology – eg wireless sensor networks (WSN)Environmentally friendly – disposal of batteries is tightly regulated because

they contain chemicals and metals that are harmful to the environment and hazardous to human health

Opens up new applications – such as deploying EH sensors to monitor remote or underwater locations

5January 21, 2016

Autonomous sensors

Embedded sensor nodes

Recharging the batteries

Smart systems

Autonomous WSN

NEEDS

Remove the expense, inconvenience and pollution that results from frequent replacement of batteries in small devices Environmental savings Needs of the Third World (education and lighting) Needs in developed countries

Sou

rce

Sou

tha

mp

ton

Un

iver

sity

Ho

spit

al U

K

Source: IDTechEx report “Energy Harvesting and Storage for Electronic Devices 2009-2019”

6January 21, 2016

POWER REQUIREMENTS OF ENERGY HARVESTING

Source: IDTechEx report “Energy Harvesting and Storage for Electronic Devices 2009-2019”.

Sensors typically require 1 to 50 mW. It is impractical or extremely expensive to change batteries in sensors in most of the envisaged locations. The same is true of active RFID but with a wider range of required power.

7January 21, 2016

POTENTIAL ENERGY HARVESTING MARKETS

Sou

rce:

IDTe

chEx

rep

ort

“En

erg

y H

arv

esti

ng

an

d S

tora

ge

for

Elec

tro

nic

Dev

ices

20

09

-20

19

”.

Global market value of energy harvesting for small electronic and electrical devices in 2014

8January 21, 2016

RESEARCH DEVELOPMENTS

Tame batsA surveillance bat that will employ solar, wind, vibration and “other sources” to recharge its battery ($22.5 million)

COM-BAT surveillance bat

Sou

rce

Un

iver

sity

of

Mic

hig

an

15 centimeter, one watt robotic spy

Invisible harvestingMany new printed electronic devices are transparent including metal oxide transistors.

Transparent, flexible printed battery that charges in one minute

Sou

rce

Wa

sed

aU

niv

ersi

ty

Electricity for underwater electronicsSource Ocean Power Technologies

a flag-like structure that moved with the tides to generate electricity

Vortex Hydro EnergyVIVACE converter: a hydrokinetic power generating device, which harnesseshydrokinetic energy of river and ocean currents. It uses the physical phenomenon ofvortex induced vibration in which water current flows around cylinders inducingtransverse motion. The energy contained in the movement of the cylinder is thenconverted to electricity.

Patent of University of Michigan

9January 21, 2016

New healthcare harvestingA wearable battery-free wireless 2-channel EEG system integrated into a device resembling headphones has been developed, powered by a hybrid power supply using body heat and ambient light.

New polymer and metal alloy capabilitiesOther promising approaches involve organic piezoelectric or electroactive polymers, possibly exhibiting electret properties as well.

People powerImplanted defibrillators and pacemakers powered electrodynamically from the human heart that they administer

Biobatteries harvest body fluids

Nantennas

Source Idaho National Laboratory

Nantenna array harvesting infrared

RESEARCH DEVELOPMENTS

Solar cells that work in the darkphotovoltaics that can convert infrared as well as light into electricity

MEMSMicrominiature versions of favourite EH technologies (electrodynamics, thermoelectrics, piezoelectrics and photovoltaics), often with exotic new materials.

10January 21, 2016

Energy scavenging from wasted ambient energy sources: light, heat, vibrations, RF radiation, etc..

Energy Harvesting sources

courtesy of ZhejiangSolar Panel

courtesy of PerpetuaPower Source Technologies

cou

rtes

y o

f b

cp-e

ner

gia

Princeton University

Wireless Sensor andenergy harvester

courtesy of SolarBotanic

Source: Georgia Tech

11January 21, 2016

•Piezoelectric materials Mechanical stress ↔ electrical signalHuman motion, low-frequency vibrations, and acoustic noise are just some of the potential sources that could be harvested by piezoelectric materials.Examples of piezoelectric EH:

Battery-less remote control – the force used to press a button is sufficient to power a wireless radio or infrared signal

Piezoelectric floor tiles – there is much interest in harvesting the kinetic energy generated by the footsteps of crowds to power ticket gates and display systems

Car tyre pressure sensors – EH sensors attached inside the tyres continuously monitor the pressure and send the information to a display on the dashboard

•Thermoelectric materials Temperature differences across the material ↔ electric voltageA temperature across a thermoelectric crystal (i.e. one side is warmer/cooler than the other), it causes a voltage across the crystal.Example of thermoelectric EH:

Road transport – Cars and lorries equipped with a thermoelectric generators (TEG) would have significant fuel savings (especially with the increasing cost of petrol). In 2009, VW demonstrated this proof of concept. The thermoelectric generator of their prototype car gained about 600W from running on a highway, reducing fuel consumption by 5%

TYPES OF ENERGY HARVESTING MATERIALS

•Pyroelectric materials Change in temperature ↔ electric chargeAs the temperature of a pyroelectric crystal changes, it generates an electrical charge. Example of pyroelectric EH:

The pyroelectric effect is used in some sensors, but it is still some way from commercial energy harvesting applications

12January 21, 2016

Energy scavenging from wasted ambient energy sources: light, heat, vibrations, RF radiation, etc..

ENERGY HARVESTING SOURCES

courtesy of ZhejiangSolar Panel

courtesy of PerpetuaPower Source Technologies

cou

rtes

y o

f b

cp-e

ner

gia

Princeton University

Wireless Sensor andenergy harvester

courtesy of SolarBotanic

Source: Georgia Tech

vibrations

13January 21, 2016

Courtesy of Perpetuum

Courtesy of Pavegen

Courtesy of University of Pennsylvania

Courtesy of Christian Croft Courtesy Seiko Watch Corporation

Sustainable Dance Club

Courtesy of SUNY

Ambient vibrations come in a vastvariety of forms…

AVAILABLE MECHANICAL SOURCES

POWERLeap system

Patent of University of Michigan

14January 21, 2016

ORDERS OF POWER

15January 21, 2016


1400 kW

20 W

T. Krupenkin and J. A. Taylor, Nature Communications 2011

2.4μW

fabricated at Imperial College London

hybrid transduction mechanism.Hybrid energy harvesters could

power handheld electronics, 18 October 2010, SPIE Newsroom

180μW

1.4μW

fabricated at TIMA - EPFL

60μW

fabricated at IMEC

Macro-scale centimeter-scale MEMS

CONVERSION MECHANISM

16January 21, 2016


1400 kW

20 W

T. Krupenkin and J. A. Taylor, Nature Communications 2011

2.4μW

fabricated at Imperial College London

hybrid transduction mechanism.Hybrid energy harvesters could

power handheld electronics, 18 October 2010, SPIE Newsroom

180μW

1.4μW

fabricated at TIMA - EPFL

60μW

fabricated at IMEC

Macro-scale centimeter-scale MEMS

CONVERSION MECHANISM

17January 21, 2016

TRADITIONAL APPROACH

• In the vast majority of cases the ambientvibrations come in a vast variety of forms.

• The energy distributed over a wide spectrumof frequencies, typically confined in a maximalbandwidth of few thousand of Hz.

A classical transduction mechanism is based on vibrating mechanical bodies(linear systems).

MEMS

P0Vib.

Output

PZT

Linear System

18January 21, 2016

LINEAR APPROACH

Typ

ical

en

erg

y h

arve

ste

rp

rin

cip

le

MEMS

P0Vib.

Output

PZT

19January 21, 2016

<

LINEAR APPROACH

… some issues with linear resonant harvesters …

Linear systems exhibit a resonantbehaviour (i.e. resonance frequency).

Transfer function presents one ormore peaks corresponding to theresonance frequencies and thus it isefficient mainly when the incomingenergy is abundant in that regions.

Narrow frequency bandwidth: the generator must be designed for specific vibration sourcesand applications.

Require resonance frequency matching with vibrational sources.

20January 21, 2016

Linear and nonlinear Strategies… some issues with linear resonant harvesters …

Linear resonant structuresRequire frequency matching with sources.Poor performance out of resonance.Difficulties in scaling and tuning at micro/nano scale.

Suitability only with narrow band vibrations (e.g. from

rotating machines).

Frequency band matchingissues in MEMS and NEMS

technologies.Wideband vibrations below 500 Hz(about the 90 % of vibrationalsources) require a different strategyto efficiently harvest energy

Whishlist for the ‘’perfect’’ vibration harvester:1) Harvesting energy over a wide frequency band2) No need for frequency tuning3) Harvesting energy at low frequency (below 500 Hz)

How to increase efficiency of energy harvester?

LINEAR APPROACH

21January 21, 2016

SOTA - WIDE BAND HARVESTER

35January 21, 2016

A Wireless Sensor Node Powered by NonLinear Energy Harvester

36January 21, 2016

The general architecture of a Vibration Energy Harvesting system …

Vibrationalsource

Acceleration amplitudeFrequency Spectrum…

TYPICAL EH ARCHITECTURE SCHEMATIZATION

37January 21, 2016

Vibrationalsource

Couplingmechanical

structure

LinearNonlinear…




38January 21, 2016

Y

X

System has two stable equilibrium states (S1 and S2), separated by unstable equilibrium state (U).

The device switching between its stable statesallows for improving the efficiency of theenergy conversion, from mechanic to electric

Fixed-Fixed BeamLinear Beam

The vertical moviment of the masscaused by vibrations creates the strainin the beam. The piezoelectric materialconvert this strain in a voltage.

Stable equilibrium position n°1

Stable equilibrium position n°2

Instable equilibrium position

Neutral equilibrium position

S2

U

S1

LINEAR VS NON LINEAR

39January 21, 2016

Vibrationalsource

Couplingmechanical

structure

LinearNonlinear…

Mechanical-to-electricalconversion

PiezoelectricElectrostaticElectromagnetic…




40January 21, 2016

Vibrationalsource

Couplingmechanical

structure

Mechanical-to-electricalconversion

LinearNonlinear…

PiezoelectricElectrostaticElectromagnetic…

Electricalenergyoutput

“Direct powering” “batteries recharging” ?




41January 21, 2016

DOUBLE PIEZO – SNAP THROUGH BUCKLING HARVESTER

Schematization of the bistable nonlinear harvester

Top view

RF transmitterTI eZ430 – RF2500

10 cm

The DP-STB-NLH Piezoelectric transducers Mide'sVolture™ V21bl

PET (PolyEthylene Terephthalate) beam 6 cm x 1 cm x 100 µm

Linear Technology LT3588-1 + input/output storage capacitors

42January 21, 2016

Flexible precompressed PET beam + suitable proof mass implementing the bistable mechanism

Two piezoelectric vibration energy harvesters V21BL (Volture) connected in a parallel configuration

DOUBLE PIEZO – SNAP THROUGH BUCKLING HARVESTER

X

Y

ΔX

ΔY/2

Cantilever

ΔY/2

F

t

Piezoelectric

Proof mass

6 c

m

Piezoelectric on both faces

Cantilever

6 c

m

3.5

6 c

m

3.5

cm

2.5

cm

Max tip-to-tip displacement = 0.46 cm

fixed-fixed PET beam

Inertial mass (3g)

Pre-compression ΔY= 2 mm

Specifications - v21bl Device size (cm): 9.04 x 1.7 x 0.08Device weight (g): 3.26Active elements: 1 stack of 2 piezosPiezo wafer size (cm): 3.56 x 1.45 x 0.02

43January 21, 2016

The STB harvester can be modeled as a classical second order mass-damper-spring system, with anadditive nonlinear term related to the bistable potential energy function

MECHANICAL BEHAVIOR OF THE STB-NON LINEAR HARVESTER

24

2

1

4

1)( xbxaxU

-10 -8 -6 -4 -2 0 2 4 6 8 10-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

Displacement x of the central mass along X-axis from initial position [mm]

Ela

stic

Po

ten

tial E

ne

rgy

U(x

) [N

*mm

]

)(3 tFxbaxxdxm

44January 21, 2016

STATIC CHARACTERIZATION OF THE BEAM BEHAVIOR

Goal: measurement of the minimum acceleration required to implement the switchingmechanism between the two stable states of the device.Methodology: Experiments consisting of loading the pre-compressed beam with referencemasses (forces) until switching occurs .

Acceleration required to make the beam switch between itsstable states, with different proof masses loading the beam.The continuous lines denote interpolation models.

acceleration values are compatible with standard sources

14 16 18 20 22 24 261

2

3

4

5

6

7

Distance between stable equilibrium positions X [mm]

Accele

ration [

m/s

2]

mproof

=6g

mproof

=12g

mproof

=18g

1 2 3Pre-compression Y [mm]

45January 21, 2016

-10 -5 0 5 10-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

Displacement along X-axis from stable states [mm]

Re

actio

n forc

e a

lon

g X

-axis

[m

N]

Observed

Predicted

-10 -5 0 5 10-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05


Ela

stic

Po

ten

tial E

ne

rgy U

(x)

[N*m

m]

STATIC CHARACTERIZATION OF THE BEAM BEHAVIOR

Reconstruction of the reaction force )(xThe pre-compressed beam was stressed by a controlled force applied orthogonally to the beam center.A load cell (Transducer Techniques GSO-10) was used to independently measure the force.

2

2

real

predreal

F

FFJ

2 / 4U b a

To fit the observed behavior, a Nelder Mead optimization algorithm was implemented through a dedicated Matlab script exploiting the following minimization index:

Parameters estimated (in case of pre-compression ∆Y of 3 mm ):a = 1.039e-4 kg/m2s2,b= 0.0098 kg/s2

24

2

1

4

1)( xbxaxU

46January 21, 2016

4 6 8 10 12 14 162

4

6

8

10

12

14

16

18

frequency [Hz]

RM

S A

cce

lera

tion

[m

/s2]

Dynamic mechanical characterization of the DP-NLH device in case of a beam pre-compression of 3 mm and a proof mass of 6g.

The envisaged broadband operation of the proposed bistable architecture emerges via the possibility of inducing switching events by slightly supra-threshold acceleration values for the entire frequency range of interest.

THE DYNAMIC MECHANICAL CHARACTERIZATION

Goal: estimation of the minimum acceleration (vs stimulus frequency) able to make the device switchbetween its stable states.Methodology: the beam was subjected to several repeated cycles of a periodic sine mechanicalstimulation in the range [4 - 15] Hz applied via a standard shaker. A reference laser system (BaumerOADM 12U6430/S35A) was used to obtain an independent quantification of the beam switching whilethe analog accelerometer (Freescale Semiconductor MMA7361L) was used to independently measure theacceleration applied.

47January 21, 2016

ELECTRICAL CHARACTERIZATION OF THE NONLINEAR HARVESTER

Goal: Investigation of the electrical performances of the DP-STB device in terms of electrical powergenerated for different values of acceleration, pre-compression, proof mass and resistive load.Methodology: the device was subjected to several repeated cycles of a periodic sine mechanical stimulationin the range [4 - 10] Hz applied via a standard shaker .

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-6

-4

-2

0

2

4

6

8

time [s]

Vp

iezo

[V

]

-4.18

-2.78

-1.39

0

1.39

2.78

4.18

5.57

Va

cc [V

]

Piezoelectrics

Accelerometer

aRMS

= 9.81 m/s2

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-10

-5

0

5

10

15

time [s]

Vp

iezo [V

]

-4.12

-2.06

0

2.06

4.12

6.18

Va

cce

l [V

]

Piezoelectrics

Accelerometer

aRMS

= 11.24 m/s2

f= 4 Hz – Rload = 1MΩ

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-30

-20

-10

0

10

20

30

Vpie

zo [

V]

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-6

-4

-2

0

2

4

6

Vacc [

V]

time [s]

Piezoelectrics

Accelerometer

aRMS

=16.81 m/s2

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-60

-40

-20

0

20

40

60

time [s]

Vpie

zo [V

]

-10.35

-6.90

-3.45

0

3.45

6.90

10.35

Vaccel [

V]

Piezoelectrics

Accelerometer

aRMS

= 28.66 m/s2

f= 10 Hz – Rload = 1MΩ

48January 21, 2016

Frequency [Hz] Power [µW]

4 284.8

5 296.3

8 309.4

10 313

Electrical power produced by the DP-NLH device as been evaluated as

R/V 2RMS

where VRMS is the RMS voltage measured across the load R (0.1 – 100 kΩ)

ELECTRICAL CHARACTERIZATION OF THE NONLINEAR HARVESTER

aRMS = 16.81 m/s2 R = 5 kΩ

frequency broad band operation 102

103

104

105

0

50

100

150

200

250

300

350

Load resistance []

Po

we

r [

W]

f=4Hz

f=5Hz

f=8Hz

f=10Hz

aRMS

= 16.81 m/s2

aRMS

= 12.11 m/s2

aRMS

= 11.43 m/s2

aRMS

= 9.81 m/s2

49January 21, 2016

Batteries or capacitors

LTC3588-1 Piezoelectric Energy Harvesting Power Supply

Up to 100mA of Output Current Selectable Output Voltages of 1.8V, 2.5V, 3.3V, 3.6V

ENERGY STORAGE AND POWER MANAGEMENT

50January 21, 2016

Energy source Energy Harvester Storage

Load

Load to supply

LTC3588-1 supercapacitor

The LTC3588-1 has an internal full-wavebridge rectifier accessible via the differentialPZ1 and PZ2 inputs that rectifies AC inputssuch as those from a piezoelectric element.The rectified output is stored on a capacitorat the VIN pin and can be used as an energyreservoir for the buck converter.


51January 21, 2016


52January 21, 2016

NLH + LTC3588-1

Investigation of the capability of the NLH to generate power to supply electronic.

The device was subjected to several repeated cycles of a periodic sine mechanical stimulation at 10Hz.

The time for first activation of the output, the time required for consecutive activations and the timeassuring a high Vo, have been evaluated.

VcVO

Supercapacitors

CSTORAGE = 47 µFaRMS =9.81 m/s2

Rload = 100 kΩ

t’ tonVo tonPGOOD t’

CSTORAGE = 94 µFaRMS =9.81 m/s2

Rload = 100 kΩ

Δt

PGOOD enable pin

53January 21, 2016

LOAD[Ω]

t’[s]

∆t[s]

tonPGOOD

[s]tonVo[s]

supercapacitors47µF

560 38.19 13.90 0.01 0.06

1.1k 38.80 14.30 0.02 0.1

2.2k 39.50 14.07 0.02 0.2

5k 39.37 15.00 0.1 0.51

10k 39.00 13.90 0.19 0.94

100k 39.79 14.95 2.25 9.25


560 61.99 21.87 0.03 0.07

1.1k 79.31 29.59 0.05 0.13

2.2k 78.49 30.57 0.09 0.26

5k 81.21 31.72 0.22 0.64

10k 72.09 26.30 0.44 1.27

100k 70.87 26.2 5.3 12.52

LOAD[Ω]

t’[s]

∆t[s]

tonPGOOD

[s]tonVo[s]


560 23.68 8.58 0.02 0.07

1.1k 25.20 7.97 0.02 0.11

2.2k 22.85 8.32 0.04 0.23

5k 24.59 8.62 0.09 0.52

10k 24.90 8.41 0.19 0.94

100k 25.19 8.89 2.61 9.98


560 43.09 15.27 0.02 0.07

1.1k 50.49 17.16 0.04 0.14

2.2k 52.40 18.11 0.09 0.28

5k 50.17 17.28 0.22 0.61

10k 49.40 17.86 0.44 1.21

100k 48.72 17.54 5.85 12.97

aRMS = 9.81 m/s2 fs=10Hz aRMS = 11.43 m/s2 fs=10Hz

NLH + LTC3588-1

54January 21, 2016

102

103

104

10510

15

20

25

30

35

Load resistance []

t [s

]

aRMS

=9.81 m/s2

aRMS

=11.34 m/s2

aRMS

=12.11 m/s2

102

103

104

105

0

1

2

3

4

5

6

7

Load resistance []

t onP

GO

OD [s]

aRMS

=9.81 m/s2

aRMS

=11.43 m/s2

aRMS

=12.11 m/s2

102

103

104

10515

20

25

30

35

40

Load resistance []

t' [s

]

aRMS

=9.81 m/s2

aRMS

=11.43 m/s2

aRMS

=12.11 m/s2

102

103

104

1055

10

15

Load resistance []

t [s

]

aRMS

=9.81 m/s2

aRMS

=11.43 m/s2

aRMS

=12.11 m/s2

102

103

104

105

35

40

45

50

55

60

65

70

75

80

85

Load resistance []

t' [s

]

aRMS

=9.81 m/s2

aRMS

=11.43 m/s2

aRMS

=12.11 m/s2

102

103

104

1050

0.5

1

1.5

2

2.5

3

3.5

Load resistance []

t on

PG

OO

D [s]

aRMS

=9.81 m/s2

aRMS

=11.43 m/s2

aRMS

=12.11 m/s2

CSTORAGE = 47 µF CSTORAGE = 47 µF

CSTORAGE = 47 µF

CSTORAGE = 94 µF CSTORAGE = 94 µF CSTORAGE = 94 µF

DP-STB + LTC3588-1

55January 21, 2016

NLH + LTC3588-1 + RF-TX

aRMS

[m/s2]t’[s]

∆t[s]

tonPGOOD

[s]ton-PIN6

[s]

tPGOOD

-PIN6

[s]

supercapacitor47µF

9.81 28.82 11.57 0.01 0.03 0.005

11.43 18.95 5.96 0.02 0.02 0.005

12.11 11.99 5.12 0.02 0.03 0.005

supercapacitor94µF

9.81 55.12 21.39 0.03 0.03 0.01

11.43 46.30 15.04 0.05 0.02 0.005

12.11 29.06 9.25 0.09 0.02 0.01

CC2500Pushbutton

18 Accessible Pins

Chip Antenna

two LEDs

MSP430F2274

Producer Texas Instruments

Max Frequency 16MHz

Communication USB/2.4GHz

Power supply 1.83.6V

Board Power Consumption (max values)

Only processorActive mode 390µAStanby mode 1.4µA

RF TransceiverRX mode 18.8mATX mode 21.2mA

PIN6 is a digital output pin on the RF receiver (RX)

Goal: Investigation of the capability of the DP-STBdevice to power a RF - TX

56January 21, 2016

0 20 40 60 80 100 120

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

time [s]

Voltage

[V

]

acceleration

VC

Enable

RX digital output

-55.82

-44.66

-33.50

0

33.50

44.66

55.82

acce

lera

tio

n [

m/s

2]

t' t t

77 77.05 77.1 77.15

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

time [s]

Vo

lta

ge

[V

]

acceleration

VC

Enable

RX digital output

-55.82

-44.66

-33.50

0

33.50

44.66

55.82

acce

lera

tio

n [

m/s

2]

0 10 20 30 40 50 60 70

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

time [s]

Volta

ge

[V

]

-81.35

-65.09

-48.81

0

48.81

65.09

81.35

acce

lera

tio

n [

m/s

2]

acceleration

VC

Enable

RX digital output

t tttt'

Signals have been acquired by a Lecroy 6050AWaveRunner digital oscilloscope

The Enable pin, is logic high when theoutput voltage is above 92% of the targetvalue (set to 3.3 V).

The node is able to scavenge energy fromwideband vibrations to transmit data by theSimpliciTI® network protocol @ 2.4 GHz.

NLH + LTC3588-1 + RF-TX

57January 21, 2016

ConclusionsA batteryless wireless node powered by a nonlinear bistable energy harvester has beendiscussed. The node is able to scavenge energy from wideband vibrations to transmit data@ 2.4 GHz. Results obtained encourage the use of proposed nonlinear harvesters topower wireless sensor nodes.

Future works

• Characterization of the behavior of the device with a noisy input stimulation• Development of an analytical model including the mechanical to electrical conversion.

ACKNOWLEDGMENT

The authors gratefully acknowledge support from the US Office of Naval Research (Global), and the US Army International Technology Center (USAITC).

Smart&Authonomous Sensing Systems @SensorLab

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InkJet Printed– Snap Through Buckling Harvester

The STB beam is implemented via a PET (PolyEthylene Terephthalate) substrate

Development of Low Cost Printed Devices for Energy Harvesting from Environmental Vibrations(CSP06N1EJEPC30), 2012-2013

DEPARTMENT OF THE ARMYARMY MATERIAL COMMAND

RESEARCH, DEVELOPMENT AND ENGINEERING COMMANDINTERNATIONAL TECHNOLOGY CENTER-ATLANTIC UNIT (ITC-AC)


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The proposed approach: Snap Through Buckling Harvester

Main challenges:•The low cost mechanical structure implementing the non linear switching mechanism ;

•The technology to realize electrodes, sensors, readout systems and functional layers;

•The mechanic-electric conversion.

Solution: a two-end clamped PET beam exploiting “snap-through buckling” approach, low cost COTS devices and direct printing methodologies.

X

Y

ΔX

ΔY/2

Stablestate

Stablestate

ΔY/2

F

tProof mass

Z


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The STB harvester can be modeled as a classical second order mass-damper-spring system, with an additive nonlinear term related to the bistable potential energy function

Mechanical Behavior of the STB-Non Linear Harvester

+ − + =

where: m is the mass of the cantilever beam, d is the damping coefficient, , and are the acceleration, the velocity and the displacement of the cantilever beam, respectively() is the stochastic source modeling the external input mechanical vibrations,cx is the term ruling the linear behavior of the device. () is the restoring force which is linked to the potential energy function U(x) via

= −()

24

2

1

4

1)( xbxaxU

-10 -8 -6 -4 -2 0 2 4 6 8 10-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05


Ela

stic

Po

ten

tial E

ne

rgy

U(x

) [N

*mm

]


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Static characterization of the beam behavior

Goal: measurement of the minimum acceleration required to implement the switchingmechanism between the two stable states of the device.Methodology: Experiments consisting of loading the pre-compressed beam with referencemasses (force) until switching occurs .

Acceleration required to make the beam switch between itsstable states, with different proof masses loading the beam.The continuous lines denote interpolation models.

acceleration values are compatible with standard sources


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1

MN

MX

X

Y

Z

Forza_2

-.149E-06.780E-03

.001561.002341

.003121.003902

.004682.005463

.006243.007135

NODAL SOLUTION

STEP=1SUB =32TIME=1UX (AVG)RSYS=0DMX =.007135SMN =-.149E-06SMX =.007135

S2

S1

Input: External force, Fest

Output: Displacement ΔX

1

MNMX

X

Y

Z

Forza

-.908E-08.657E-03

.001314.001972

.002629.003286

.003943.0046

.005258.006009

NODAL SOLUTION

STEP=5SUB =11TIME=5UX (AVG)RSYS=0DMX =.006009SMN =-.908E-08SMX =.006009 S1

S2

Fest<f2-1 the beam

doesn’t switch

FEM (Finite Element Method) Analysis in Ansys®

1

MN

MX

X

Y

Z

Forza_2

-.00799-.007116

-.006243-.005369

-.004495-.003621

-.002747-.001873

-.999E-03.434E-07

NODAL SOLUTION

STEP=1SUB =15TIME=1UX (AVG)RSYS=0DMX =.00799SMN =-.00799SMX =.434E-07 S1

S2

1

MN

MX

X

Y

Z

Forza_2

-.149E-06.780E-03

.001561.002341

.003121.003902

.004682.005463

.006243.007135

NODAL SOLUTION

STEP=1SUB =32TIME=1UX (AVG)RSYS=0DMX =.007135SMN =-.149E-06SMX =.007135

S2

S1

Fest>f2-1 the beam

switches from the state S2 to the state S1

S1 and S2 are the stable equilibrium states estimated when the force is null f1-2 e f2-1 are the static forces allowing the commutation between two stable states.


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To improve performances of FEM predictions the following correction model has been estimated

FFEMF bFaF

where F denotes the force required to switch the beam estimated by model starting from the simulated values, and aF = 0.8 and bF = 0.008 N are fitting parameters obtained by applying a least mean squares minimization algorithm.

1 2 325

30

35

40

45

50

55

Pre-compression Y [mm]

Re

act

ion

Fo

rce

[m

N]

FEM

Observed

Estimated

Static force required to make the beam switch between its stable states. Comparison betweenobservations, FEM simulations, and estimations obtained by model for different pre-compression values, are shown.


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The model adopted to describe the relationship between the minimum acceleration am

enabling the beam switching, and ∆X as a function of the proof mass m, is

mmXXmXma iiimi

22

where:

mi (i=6 g, 12 g, 18 g) represents the proof mass

= 6.7639e-4 m4·kg6/s2

= -0.0244 m4·kg3/s2

= 0.2683 m4/s2

= 0.0107 m·kg6/s2

= -0.3824 m·kg3/s2

= 4.1885 m/s2

fitting parameters estimated by applying the Nelder–Mead nonlinear simplex optimization algorithm with the following functional J

gg

gi

i

predm

realm

Ni

N

aaJ ii

18312261

:3

1

2


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Investigations of dynamic performance of the IJP-STB harvester

Goal: estimation of the minimum acceleration (vs stimulus frequency) able to make the device switchbetween its stable states.Methodology: the beam was subjected to several repeated cycles of a periodic sine mechanicalstimulation in the range [4 - 20] Hz applied via a standard shaker. A reference laser system (BaumerOADM 12U6430/S35A) was used to obtain an independent quantification of the beam switching whilethe analog accelerometer (Freescale Semiconductor MMA7361L) was used to independently measurethe acceleration applied.

0 2 4 6 8 10 12 14 16 18 200

5

10

15

20

25

30

35

40

Frequency [Hz]

Acc

ele

ratio

n [

m/s

2]

Y=1mm

Y=3mm

Minimum acceleration assuring the switching mechanism asa function of the stimulus frequency and the beam pre-compression. A proof mass of 6 g was used to load thebeam.


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Investigations of dynamic performance of the IJP-STB harvester

0 0.5 1 1.5 2 2.5 3 3.5 4-15.9

-7.95

0

7.95

15.9

time [s]

Dis

pla

cem

en

t [m

m]

0 0,5 1 1,5 2 2,5 3 3,5 4-19.05

-9.52

0

9.52

19.05

time [s]

Acc

ele

ratio

n [

m/s

2]

laser

accelerometer

0 1 2 3 4

-12.9

0

12.9

time [s]

Dis

pla

ce

me

nt

[mm

]

0 1 2 3 4-47.62

-23.81

0

23.81

47.62

time [s]

Acc

ele

ratio

n [

m/s

2]

laser

accelerometer

ΔY= 1 mm ΔY= 3 mm

laser

accelerometer

PSD of the laser output signal

Example of time series of signals output in case of sinusoidal solicitation at 6Hz with the strength close to the minimum value assuring the beam switching between its stable states


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Fitting observed behavior by the model

+ − + =

= −()

24

2

1

4

1)( xbxaxU

Experimental set-up for the estimation of thepotential form U(x).

The applied force was independently measured by the load cell (Transducer Techniques GSO-10)

In order to fit the observed behaviors by model (*), a Nelder Mead optimizationalgorithm was implemented through a dedicated Matlab script exploiting the followingminimization index:

+ + − = (*)

where =b-c

2

2

2

2

real

predreal

real

predreal

F

FF

x

xxJ

xreal and xpred refer to the measured and predicted displacement of the bistable deviceFreal and Fpred refer to the measured and predicted force


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-8 -6 -4 -2 0 2 4 6 8-40

-30

-20

-10

0

10

20

30

40


Rea

ctio

n f

orc

e a

lon

g X

-axi

s [m

N]

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-10

-8

-6

-4

-2

0

2

4

6

8

10

time [s]

Dis

pla

cem

en

t x

alo

ng

X-a

xis

[mm

]

Measured displacement

Predicted displacement

-10 -8 -6 -4 -2 0 2 4 6 8 10-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05


Ela

stic

Po

ten

tial E

ne

rgy

U(x

) [N

*mm

]

-15 -12 -9 -6 -3 0 3 6 9 12 15-100

-50

0

50

100


React

ion forc

e a

long X

-axi

s [m

N]

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-15

-10

-5

0

5

10

15

time [s]

Dis

pla

cem

ent x

alo

ng X

-axis

[m

m]

Measured displacement

Predicted displacement

-15 -10 -5 0 5 10 15-1.5

-1

-0.5

0

0.5


Ela

stic

Pote

ntia

l Energ

y U

(x)

[N*m

m]

ΔY= 1 mm

ΔY= 3 mm

Estimated parameters: a = 2.567e-4 kg/m2s2, b=0.017, = -8.462 kg/s2 and d=1.0e-4 kg/s

Estimated parameters: a=1.893e-4 kg/m2s2, b=0.031, = -8.742 kg/s2 and d=1.0e-3 kg/s


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PBH1-1

PBH1-2

Printed Bistable Harvester

A set of parallel and InterDigiTed (IDT) electrodes with different dimensions has been designed and realized to test the proposed technology


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1 c

m

10 cm

Sub

stra

teID

Tel

ectr

od

es

Act

ive

Mat

eria

lPZ

T


A PZT layer has been screen printed to convert strains due to the beam switches (induced by external vibrations) between its two stable states into an output voltage.


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PZT Deposition and poling(Department of Information Engineering (DII) University of Breascia)

MaterialDepositated

Depositiontechnology

Thickness Sinteringtemperature

Poling

IDT electrodes

PiezokeramicaAPC 856

Screen Printing

50µm 100°C for

10 minutes

100V130°C

(10 min)

Parallelelectrodes

PiezokeramicaAPC 856

Screen Printing

50µm 100°C for

10 minutes

100V130°C

(10 min)



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Layout

IDT electrodes realized by inkjet printing

PZT layer



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Electrical Behavior of the IJP - STB Harvester

Goal: characterization of the electrical performances of the inkjet printed snap through bucklingharvester.Methodology: the beam was subjected to several repeated cycles of a periodic sine mechanicalstimulation in the range [4 - 20] Hz applied via a standard shaker. A reference proof mass is placed inthe middle of the beam in order to reduce the required acceleration to make the device switchingbetween its stable states. A reference laser system (Baumer OADM 12U6430/S35A) was used to obtainan independent quantification of the beam switching while the analog accelerometer (FreescaleSemiconductor MMA7361L) was used to independently measure the acceleration applied.

proof mass

IJP-STB harvester


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Electrical Behavior of the IJP - STB HarvesterExamples of the experimental behavior of the device

ΔY=1 mm and Accmax=28.9 m/s2 @6Hz

0 1 2 3 4 5-96.8

-72.6

-48.4

-24.2

0

24.2

48.4

time (s)

Acce

lera

tion (

m/s

2)

AccelerometerSTB Harvester

-0.5

0

0.5

1

1.5

2

2.5

Voltag

e (

V)

0 5 10 15 20 25 30 35 40-95

-80

-60

-50

Frequency (Hz)

Po

we

r/fr

eq

ue

ncy (

dB

/Hz)

0 5 10 15 20 25 30 35 40-95

-80

-60

-40

-20

Frequency (Hz)

Po

we

r/fr

eq

ue

ncy (

dB

/Hz)

Accelerometer

STB Harvester


0 1 2 3 4 5-116.95

-93.05

-69.15

-47.8

-23.9

0

23.9

47.8

69.15

time (s)

Acce

lera

tio

n (

m/s

2)

-1

-0.5

0

0.5

1

1.5

2

2.5

3

Vo

lta

ge

(V

)


5 10 15 20 25 30 35 40

-80

-60

-40

-20

Frequency (Hz)

Po

we

r/fr

eq

ue

ncy (

dB

/Hz)

0 5 10 15 20 25 30 35 40

-100

-80

-60

-40

Frequency (Hz)

Po

we

r/fr

eq

ue

ncy (

dB

/Hz)

Accelerometer

STB Harvester


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Electrical Behavior of the IJP - STB HarvesterExamples of the experimental behavior of the device


0 1 2 3 4 5

-125.3

-77.7

-29.5-17.5

0

17.529.541.4

65.2

time (s)

Acce

lera

tio

n (

m/s

2)

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

Vo

lta

ge

(V

)


5 10 15 20 25 30 35 40-80

-60

-40

-20

Frequency (Hz)

Po

wer/

frequ

en

cy (

dB

/Hz)

5 10 15 20 25 30 35 40-80

-60

-40

-20

Frequency (Hz)

Po

wer/

freq

ue

ncy (

dB

/Hz)

Accelerometer

STB Harvester

0 1 2 3 4 5

-125.7

-64.7

-40.9

-17.1

0

17.1

40.9

64.7

time (s)

Accele

ratio

n (

m/s

2)

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

Voltag

e (

V)


0 5 10 15 20 25 30 35 40-80

-60

-40

-20

Frequency (Hz)

Pow

er/

freq

uency (

dB

/Hz)

0 5 10 15 20 25 30 35 40-80

-60

-40

-20

Frequency (Hz)

Pow

er/

frequen

cy (

dB

/Hz)

Accelerometer

STB Harvester



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0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.00

0.005

0.01

0.015

0.02

0.025

AccRMS

[m/s2]

VR

MS

norm

[V

]

0.0 7.9 15.9 23.9 31.9 36.6 40.1 43.6 51.2

Accmax

[m/s2]

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.00

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

AccRMS

[m/s2]

VA

v P

eak

[V]

0.0 7.9 15.9 23.9 31.9 36.6 40.1 43.6 51.2

Accmax

[m/s2]

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.00

0.02

0.04

0.06

0.08

0.1

0.12

0.14

AccRMS

[m/s2]

VR

MS

norm

[V

]

0.0 8.5 16.9 25.4 33.9 36.4 43.6 46.8 49.9 53.4 59.3

Accmax

[m/s2]

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.00

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

AccRMS

[m/s2]

VA

V P

ea

k [V

]

0 8.5 16.9 25.4 33.9 36.4 43.6 46.8 49.9 53.4 59.3

Accmax

[m/s2]

ΔY= 1 mm

ΔY= 3 mm

normRMSV

AvPeakVand values as a function of the accelerations applied to the device for the two values of the pre-compression


6 Hz8 Hz

10 Hz

12 Hz14 Hz

6 Hz8 Hz 10 Hz

12 Hz


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RV PeakAV /2

PeakAVV

An evaluation of the electrical power produced by the STB device has been performed by

where is the average of the of the piezoelectric output voltage peaks measured across the load R=1MΩ

Powers in the order of 102 nW have been experimentally estimated


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nonlinear energy harvesting from vibrations - … floor tiles–there is much interest in harvesting...

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