nonlinear energy harvesting from vibrations - … floor tiles–there is much interest in harvesting...
TRANSCRIPT
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
Embedded sensor nodes
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
Embedded sensor nodes
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…
Acceleration amplitudeFrequency Spectrum…
TYPICAL EH ARCHITECTURE SCHEMATIZATION
The general architecture of a Vibration Energy Harvesting system …
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…
Acceleration amplitudeFrequency Spectrum…
TYPICAL EH ARCHITECTURE SCHEMATIZATION
The general architecture of a Vibration Energy Harvesting system …
40January 21, 2016
Vibrationalsource
Couplingmechanical
structure
Mechanical-to-electricalconversion
LinearNonlinear…
PiezoelectricElectrostaticElectromagnetic…
Electricalenergyoutput
“Direct powering” “batteries recharging” ?
Acceleration amplitudeFrequency Spectrum…
TYPICAL EH ARCHITECTURE SCHEMATIZATION
The general architecture of a Vibration Energy Harvesting system …
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
Displacement x of the central mass along X-axis from initial position [mm]
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.
ENERGY STORAGE AND POWER MANAGEMENT
51January 21, 2016
ENERGY STORAGE AND POWER MANAGEMENT
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
supercapacitors94µF
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]
supercapacitors47µF
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
supercapacitors94µF
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).
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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
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
]
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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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FEM (Finite Element Method) Analysis in Ansys®
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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FEM (Finite Element Method) Analysis in Ansys®
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
Displacement along X-axis from stable states [mm]
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
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
]
-15 -12 -9 -6 -3 0 3 6 9 12 15-100
-50
0
50
100
Displacement along X-axis from stable states [mm]
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
Displacement x of the central mass along X-axis from initial position [mm]
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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InkJet Printed– Snap Through Buckling Harvester
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
InkJet Printed– Snap Through Buckling Harvester
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)
InkJet Printed– Snap Through Buckling Harvester
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Layout
IDT electrodes realized by inkjet printing
PZT layer
InkJet Printed– Snap Through Buckling Harvester
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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
ΔY=1 mm and Accmax=49.7 m/s2 @6Hz
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
)
AccelerometerSTB Harvester
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
ΔY=3 mm and Accmax=38.2 m/s2 @6Hz
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
)
AccelerometerSTB Harvester
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)
AccelerometerSTB Harvester
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
ΔY=3 mm and Accmax=34.4 m/s2 @6Hz
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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
Electrical Behavior of the IJP - STB Harvester
6 Hz8 Hz
10 Hz
12 Hz14 Hz
6 Hz8 Hz 10 Hz
12 Hz
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Electrical Behavior of the IJP - STB Harvester
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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