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1 December 17, 2014
DIEEI University of Catania – Italy
Nonlinear Energy Harvesting from vibrations
2 December 17, 2014
•The Energy Harvesting issue •Non linear EH vs linear EH •The proposed solutions & the Real LabScale Prototypes
The mechanical characterization
The electrical performances
Outline
3 December 17, 2014
A WSN consists of:
Sensors and actuators
Microcontroller (μC)
Radio
Power si
mp
le v
isio
n o
f a
WSN
no
des
THE ENERGY HARVESTING ISSUE
Development of solutions aimed at powering wireless nodes by exploiting the energy scavenged from their operating environment in order to reduce (or eliminate) the need of periodic replacements of batteries (environmentally friendly).
4 December 17, 2014
Benefits: Maintenance free – no need to replace batteries
The technologies employed, variously convert
Solar radiation (PV) Wind Human power Body fluids Heat differences Vibration or other movements RF Vegetation Ultraviolet Visible 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 as heat, light, sound, vibration or movement, to provide electrical power for small electronic and electrical devices making them self-sufficient (replace batteries).
Improve efficiency – eg computing costs would be cut significantly if waste heat were harvested and used to help power 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
5 December 17, 2014
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”
6 December 17, 2014
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.
7 December 17, 2014
POTENTIAL ENERGY HARVESTING MARKETS So
urc
e: ID
Tech
Ex r
epo
rt “
Ener
gy
Ha
rves
tin
g a
nd
Sto
rag
e fo
r El
ectr
on
ic D
evic
es 2
00
9-2
01
9”.
Global market value of energy harvesting for small electronic and electrical devices in 2014
8 December 17, 2014
RESEARCH DEVELOPMENTS
Tame bats A 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 harvesting Many new printed electronic devices are transparent including metal oxide transistors.
Transparent, flexible printed battery that charges in one minute
Sou
rce
Wa
sed
a U
niv
ersi
ty
Electricity for underwater electronics Source Ocean Power Technologies
a flag-like structure that moved with the tides to generate electricity
Vortex Hydro Energy VIVACE converter: a hydrokinetic power generating device, which harnesses hydrokinetic energy of river and ocean currents. It uses the physical phenomenon of vortex induced vibration in which water current flows around cylinders inducing transverse motion. The energy contained in the movement of the cylinder is then converted to electricity.
Patent of University of Michigan
9 December 17, 2014
New healthcare harvesting A 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 capabilities Other promising approaches involve organic piezoelectric or electroactive polymers, possibly exhibiting electret properties as well.
People power Implanted 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 dark photovoltaics that can convert infrared as well as light into electricity
MEMS Microminiature versions of favourite EH technologies (electrodynamics, thermoelectrics, piezoelectrics and photovoltaics), often with exotic new materials.
10 December 17, 2014
Energy scavenging from wasted ambient energy sources: light, heat, vibrations, RF radiation, etc..
Energy Harvesting sources
courtesy of Zhejiang Solar Panel
courtesy of Perpetua Power Source Technologies
cou
rtes
y o
f b
cp-e
ner
gia
Princeton University
Wireless Sensor and energy harvester
courtesy of SolarBotanic
Source: Georgia Tech
11 December 17, 2014
•Piezoelectric materials Mechanical stress ↔ electrical signal Human 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 voltage A 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 charge As 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
12 December 17, 2014
Energy scavenging from wasted ambient energy sources: light, heat, vibrations, RF radiation, etc..
ENERGY HARVESTING SOURCES
courtesy of Zhejiang Solar Panel
courtesy of Perpetua Power Source Technologies
cou
rtes
y o
f b
cp-e
ner
gia
Princeton University
Wireless Sensor and energy harvester
courtesy of SolarBotanic
Source: Georgia Tech
vibrations
13 December 17, 2014
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 vast variety of forms…
AVAILABLE MECHANICAL SOURCES
POWERLeap system
Patent of University of Michigan
14 December 17, 2014
ORDERS OF POWER
15 December 17, 2014
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
16 December 17, 2014
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
17 December 17, 2014
TRADITIONAL APPROACH
• In the vast majority of cases the ambient vibrations come in a vast variety of forms.
• The energy distributed over a wide spectrum of frequencies, typically confined in a maximal bandwidth of few thousand of Hz.
A classical transduction mechanism is based on vibrating mechanical bodies (linear systems).
MEMS D
P0Vib.
Output
PZT
Linear System
18 December 17, 2014
LINEAR APPROACH
Typ
ical
en
erg
y h
arve
ste
r p
rin
cip
le
MEMS D
P0Vib.
Output
PZT
19 December 17, 2014
<
LINEAR APPROACH
… some issues with linear resonant harvesters …
Linear systems exhibit a resonant behaviour (i.e. resonance frequency). Transfer function presents one or more peaks corresponding to the resonance frequencies and thus it is efficient mainly when the incoming energy is abundant in that regions.
Narrow frequency bandwidth: the generator must be designed for specific vibration sources and applications. Require resonance frequency matching with vibrational sources.
20 December 17, 2014
Linear and nonlinear Strategies … some issues with linear resonant harvesters …
Linear resonant structures Require 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 matching issues in MEMS and NEMS
technologies. Wideband vibrations below 500 Hz (about the 90 % of vibrational sources) require a different strategy to efficiently harvest energy
Whishlist for the ‘’perfect’’ vibration harvester: 1) Harvesting energy over a wide frequency band 2) No need for frequency tuning 3) Harvesting energy at low frequency (below 500 Hz)
How to increase efficiency of energy harvester?
LINEAR APPROACH
21 December 17, 2014
SOTA - WIDE BAND HARVESTER
22 December 17, 2014
Linear and nonlinear Strategies … Nonlinear vibration energy harvesters …
Nonlinearity can be induced by: the geometry of the springs in the device; material nonlinearities or induced stress; mechanical coupling with other fields (magnetic and so on).
m and c are constant terms while
k(z) is a nonlinear function of the displacement z.
U(z) is the nonlinear Duffing Potential. a and b are coefficients depending on both the geometry of the device and the permanent magnets.
NONLINEAR MECHANISM – EXAMPLE 1
MEMS D
P0Vib.
Output
PZT
23 December 17, 2014
Linear and nonlinear Strategies … Nonlinear vibration energy harvesters …
m and c are constant terms while
k(z) is a nonlinear function of the displacement z.
NONLINEAR MECHANISM – EXAMPLE 1
24 December 17, 2014
Linear and nonlinear Strategies … Nonlinear vibration energy harvesters …
m and c are constant terms while
k(z) is a nonlinear function of the displacement z.
NONLINEAR MECHANISM – EXAMPLE 1
25 December 17, 2014
Prototype 1 and experimental setup
aluminum beam 53mm x 8.5mm
Δ=2mm
NONLINEAR MECHANISM – EXAMPLE 1
26 December 17, 2014
Input
System displacement
NONLINEAR MECHANISM – EXAMPLE 1
27 December 17, 2014
MICRO-MACHINED DEVICES (SOI TECHNOLOGY) – EXAMPLE 2
o Fabrication (SOI TECHNOLOGY):
• SOI wafer: 15 μm c-Si layer, 450 μm carrier substrate, 2 μm buried oxide
• Front and back side DRIE etching technique
• Fabrication: CNM, Barcelona, Spain
28 December 17, 2014
MICRO-MACHINED DEVICES (SOI TECHNOLOGY) – EXAMPLE 2
o Fabrication (SOI TECHNOLOGY):
• SOI wafer: 15 μm c-Si layer, 450 μm carrier substrate, 2 μm buried oxide
• Front and back side DRIE etching technique
• Fabrication: CNM, Barcelona, Spain
29 December 17, 2014
o Fabrication (PIEZOMUMPs TECHNOLOGY):
• A Silicon On Insulator (SOI) wafer based on 10 μm upper silicon layer and 400 μm thick of substrate with 1 μm of buried oxide has been used
• Front and back side DRIE etching technique
• Fabrication: MEMSCAP
MICRO-MACHINED DEVICES (PIEZOMUMPS TECHNOLOGY) – EXAMPLE 3
30 December 17, 2014
Micro-machined devices
o Bistable SOI and PIEZOMUMPs cantilever beam:
• After gluing a magnet, bi-stable behavior is obtained
• Displacement is electrically-measured through strain gauges
MICRO-MACHINED DEVICES (SOI/PIEZOMUMPS TECHNOLOGY)
31 December 17, 2014
Experimental Setup MICRO-MACHINED DEVICES (SOI TECHNOLOGY) – EXAMPLE 2
32 December 17, 2014
Experimental Setup
Output strain gauge
Permanent magnets stack
MEMS device
32
MICRO-MACHINED DEVICES (SOI TECHNOLOGY) – EXAMPLE 2
33 December 17, 2014
Results
∆=1.5 mm ∆=1.6 mm ∆=1.7 mm
∆=4.5 mm ∆=2.4 mm ∆=1.8 mm
o Positioning the permanent magnet
@ 0.88 g / σ=20 μN Measures on SOI device
MICRO-MACHINED DEVICES (SOI TECHNOLOGY) – EXAMPLE 2
34 December 17, 2014
Results o Response @ optimal distance of permanent magnet
@ 0.88 g / σ=20 μN
Maximum voltage≈16mV @ 1g RMS
Measures on PIEZOMUMPs device
MICRO-MACHINED DEVICES (SOI TECHNOLOGY) – EXAMPLE 2
35 December 17, 2014
A Wireless Sensor Node Powered by NonLinear Energy Harvester
36 December 17, 2014
The general architecture of a Vibration Energy Harvesting system …
Vibrational source
Acceleration amplitude
Frequency Spectrum …
TYPICAL EH ARCHITECTURE SCHEMATIZATION
37 December 17, 2014
Vibrational source
Coupling mechanical
structure
Linear Nonlinear …
Acceleration amplitude
Frequency Spectrum …
TYPICAL EH ARCHITECTURE SCHEMATIZATION
The general architecture of a Vibration Energy Harvesting system …
38 December 17, 2014
Y
X
System has two stable equilibrium states (S1 and S2), separated by unstable equilibrium state (U).
The device switching between its stable states allows for improving the efficiency of the energy conversion, from mechanic to electric
Fixed-Fixed Beam Linear Beam
The vertical moviment of the mass caused by vibrations creates the strain in the beam. The piezoelectric material convert 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
39 December 17, 2014
Vibrational source
Coupling mechanical
structure
Linear Nonlinear …
Mechanical-to-electrical conversion
Piezoelectric Electrostatic Electromagnetic …
Acceleration amplitude
Frequency Spectrum …
TYPICAL EH ARCHITECTURE SCHEMATIZATION
The general architecture of a Vibration Energy Harvesting system …
40 December 17, 2014
Vibrational source
Coupling mechanical
structure
Mechanical-to-electrical conversion
Linear Nonlinear …
Piezoelectric Electrostatic Electromagnetic …
Electrical energy output
“Direct powering” “batteries recharging” ?
Acceleration amplitude
Frequency Spectrum …
TYPICAL EH ARCHITECTURE SCHEMATIZATION
The general architecture of a Vibration Energy Harvesting system …
41 December 17, 2014
DOUBLE PIEZO – SNAP THROUGH BUCKLING HARVESTER
Schematization of the bistable nonlinear harvester
Top view
RF transmitter TI eZ430 – RF2500
10 cm
The DP-STB-NLH Piezoelectric transducers Mide's Volture™ V21bl
PET (PolyEthylene Terephthalate) beam 6 cm x 1 cm x 100 µm
Linear Technology LT3588-1 + input/output storage capacitors
42 December 17, 2014
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 c
m
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 0.08 Device weight (g): 3.26 Active elements: 1 stack of 2 piezos Piezo wafer size (cm): 3.56 x 1.45 x 0.02
43 December 17, 2014
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
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
44 December 17, 2014
STATIC CHARACTERIZATION OF THE BEAM BEHAVIOR
Goal: measurement of the minimum acceleration required to implement the switching mechanism between the two stable states of the device. Methodology: Experiments consisting of loading the pre-compressed beam with reference masses (forces) until switching occurs .
Acceleration required to make the beam switch between its stable 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 DX [mm]
Acce
lera
tio
n [
m/s
2]
mproof
=6g
mproof
=12g
mproof
=18g
1 2 3Pre-compression DY [mm]
45 December 17, 2014
-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 fo
rce
alo
ng
X-a
xis
[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 P
ote
ntia
l E
ne
rgy U
(x)
[N*m
m]
STATIC CHARACTERIZATION OF THE BEAM BEHAVIOR
Reconstruction of the reaction force )(x
The 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 aD
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
46 December 17, 2014
4 6 8 10 12 14 162
4
6
8
10
12
14
16
18
frequency [Hz]
RM
S A
ccele
ration
[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 switch between its stable states. Methodology: the beam was subjected to several repeated cycles of a periodic sine mechanical stimulation in the range [4 - 15] Hz applied via a standard shaker. A reference laser system (Baumer OADM 12U6430/S35A) was used to obtain an independent quantification of the beam switching while the analog accelerometer (Freescale Semiconductor MMA7361L) was used to independently measure the acceleration applied.
47 December 17, 2014
ELECTRICAL CHARACTERIZATION OF THE NONLINEAR HARVESTER
Goal: Investigation of the electrical performances of the DP-STB device in terms of electrical power generated 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 stimulation in 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
Vacc [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]V
pie
zo [V
]
-4.12
-2.06
0
2.06
4.12
6.18
Vaccel [
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
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
48 December 17, 2014
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 2
RMS
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
49 December 17, 2014
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
50 December 17, 2014
Energy source Energy Harvester Storage
Load
Load to supply
LTC3588-1 supercapacitor
The LTC3588-1 has an internal full-wave bridge rectifier accessible via the differential PZ1 and PZ2 inputs that rectifies AC inputs such as those from a piezoelectric element. The rectified output is stored on a capacitor at the VIN pin and can be used as an energy reservoir for the buck converter.
ENERGY STORAGE AND POWER MANAGEMENT
51 December 17, 2014
ENERGY STORAGE AND POWER MANAGEMENT
52 December 17, 2014
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 time assuring a high Vo, have been evaluated.
Vc VO
Supercapacitors
CSTORAGE = 47 µF aRMS =9.81 m/s2
Rload = 100 kΩ
t’ tonVo tonPGOOD t’
CSTORAGE = 94 µF aRMS =9.81 m/s2
Rload = 100 kΩ
Δt
PGOOD enable pin
53 December 17, 2014
LOAD
[Ω]
t’
[s]
∆t
[s]
tonPGOOD
[s]
tonVo [s]
supercapacitors
47µF
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
supercapacitors
94µF
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]
supercapacitors
47µF
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
supercapacitors
94µF
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
54 December 17, 2014
102
103
104
10510
15
20
25
30
35
Load resistance []
Dt [s
]
aRMS
=9.81 m/s2
aRMS
=11.34 m/s2
aRMS
=12.11 m/s2
102
103
104
1050
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 []D
t [s
]
aRMS
=9.81 m/s2
aRMS
=11.43 m/s2
aRMS
=12.11 m/s2
102
103
104
10535
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 onP
GO
OD
[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
55 December 17, 2014
NLH + LTC3588-1 + RF-TX
aRMS
[m/s2]
t’
[s]
∆t
[s]
tonPGOOD
[s]
ton-PIN6
[s]
tPGOOD
-PIN6
[s]
supercapacitor
47µF
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
supercapacitor
94µF
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
CC2500 Pushbutton
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 processor Active mode 390µA Stanby mode 1.4µA
RF Transceiver RX mode 18.8mA TX mode 21.2mA
PIN6 is a digital output pin on the RF receiver (RX)
Goal: Investigation of the capability of the DP-STB
device to power a RF - TX
56 December 17, 2014
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]
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]
t' Dt Dt
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]
Vo
lta
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
Dt DtDtDtt'
Signals have been acquired by a Lecroy 6050A WaveRunner digital oscilloscope
The Enable pin, is logic high when the output voltage is above 92% of the target value (set to 3.3 V).
The node is able to scavenge energy from wideband vibrations to transmit data by the SimpliciTI® network protocol @ 2.4 GHz.
NLH + LTC3588-1 + RF-TX
57 December 17, 2014
Conclusions A batteryless wireless node powered by a nonlinear bistable energy harvester has been discussed. 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 to power 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
MassIJP STB HarvesterClamping System
Substrate IJP electrodes PZT Clamping System
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 ARMY ARMY MATERIAL COMMAND
RESEARCH, DEVELOPMENT AND ENGINEERING COMMAND INTERNATIONAL 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
Stable
state
Stable
state
ΔY/2
F
t Proof 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
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 switching mechanism between the two stable states of the device. Methodology: Experiments consisting of loading the pre-compressed beam with reference masses (force) until switching occurs .
Acceleration required to make the beam switch between its stable 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=1
SUB =32
TIME=1
UX (AVG)
RSYS=0
DMX =.007135
SMN =-.149E-06
SMX =.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=5
SUB =11
TIME=5
UX (AVG)
RSYS=0
DMX =.006009
SMN =-.908E-08
SMX =.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=1
SUB =15
TIME=1
UX (AVG)
RSYS=0
DMX =.00799
SMN =-.00799
SMX =.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=1
SUB =32
TIME=1
UX (AVG)
RSYS=0
DMX =.007135
SMN =-.149E-06
SMX =.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 DY [mm]
Re
actio
n F
orc
e [
mN
]
FEM
Observed
Estimated
Static force required to make the beam switch between its stable states. Comparison between observations, 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
DDD 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
g
g
gi
i
pred
m
real
m
N
i
N
aaJ
ii
183
122
61:
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 switch between its stable states. Methodology: the beam was subjected to several repeated cycles of a periodic sine mechanical stimulation in the range [4 - 20] Hz applied via a standard shaker. A reference laser system (Baumer OADM 12U6430/S35A) was used to obtain an independent quantification of the beam switching while the analog accelerometer (Freescale Semiconductor MMA7361L) was used to independently measure the acceleration applied.
0 2 4 6 8 10 12 14 16 18 200
5
10
15
20
25
30
35
40
Frequency [Hz]
Acce
lera
tio
n [
m/s
2]
DY=1mm
DY=3mm
Minimum acceleration assuring the switching mechanism as a function of the stimulus frequency and the beam pre-compression. A proof mass of 6 g was used to load the beam.
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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
ce
me
nt
[mm
]
0 0,5 1 1,5 2 2,5 3 3,5 4-19.05
-9.52
0
9.52
19.05
time [s]
Acce
lera
tio
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]
Acce
lera
tio
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 the potential 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 optimization algorithm was implemented through a dedicated Matlab script exploiting the following minimization 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 device Freal 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]
Re
actio
n f
orc
e a
lon
g X
-axis
[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
ce
me
nt
x a
lon
g X
-axis
[m
m]
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 P
ote
ntia
l E
ne
rgy U
(x)
[N*m
m]
-15 -12 -9 -6 -3 0 3 6 9 12 15-100
-50
0
50
100
Displacement along X-axis from stable states [mm]
Reaction forc
e a
long X
-axis
[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 a
long 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 P
ote
ntial E
nerg
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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Printed Electronics: Inkjet Printed Sensors
Printed electronics is a set of printing methods
used to create electrically functional devices. Paper has been often proposed to be used as substrate but due the rough surface and high humidity absorption other materials such as plastic, ceramics and silicon has been applied more widely. Several printing processes have been piloted and printing preferably utilizes common printing equipment in the graphics arts industry
Printed Electronics
Printed Sensors
Inkjet Wearable electronics (Active clothing)
Smart Labels (RFID+sensors)
Disposable devices (biomedical) …
Low Costs/Low Performances
Flexible substrates
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Review of Printing technologies in pills…
Technology Advantages Drawbacks
Screen printing several materials masks low resolution time consuming high cost production
Desktop Inkjet printers good resolution low cost system low cost production
restricted number of conductive materials
Professional inkjet systems
high resolution several materials Low cost production
high cost system
Mixed Screen & Inkjet printing
good resolution several materials
Mask time consuming high cost
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Electronics Engineering
Chemistry
Printed Electronics: Inkjet Printed Sensors
Physics
MEMS & NEMS Technologies
Inks
Printing Systems
Substrates
C
H
A
L
L
E
N
G
E
S
Before entering the market various technological improvements are still needed.
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Printed Electronics: Inkjet Printed Sensors
Everyday desktop printer (ie Epson) Dimatix DMP 2800
www.dimatix.com
Microdrop inkjet system www.microdrop.de
Litrex M-Series inkjet system www.litrex.com
Printing systems designed
or optimized for the application
Precision and accuracy Throughput / speed and
productivity Maintenance and
reliability Electronic fluids
formulated to meet application standards
Ink jet print engine engineered for the
application Drop volume, velocity,
and placement control Robust and resistant to
electronic fluids High and precise drop
throw rate Wide range of substrates
and surface properties
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Precision and accuracy
Throughput / speed and productivity
Maintenance and reliability
Metalon JS-015 (black)
product by Novacentrix
PET Substrates
Printed Electronics: Inkjet Printed Sensors
EPSON® inkjet printer
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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
te
IDT
elec
tro
des
Act
ive
Mat
eria
l P
ZT
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)
Material Depositated
Deposition technology
Thickness Sintering temperature
Poling
IDT electrodes
Piezokeramica APC 856
Screen Printing
50µm
100°C for
10 minutes
100V 130°C
(10 min)
Parallel electrodes
Piezokeramica APC 856
Screen Printing
50µm 100°C for
10 minutes
100V 130°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 buckling harvester. Methodology: the beam was subjected to several repeated cycles of a periodic sine mechanical stimulation in the range [4 - 20] Hz applied via a standard shaker. A reference proof mass is placed in the middle of the beam in order to reduce the required acceleration to make the device switching between its stable states. A reference laser system (Baumer OADM 12U6430/S35A) was used to obtain an independent quantification of the beam switching while the analog accelerometer (Freescale Semiconductor MMA7361L) was used to independently measure the acceleration applied.
proof mass
IJP-STB harvester
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Electrical Behavior of the IJP - STB Harvester Examples 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
tio
n (
m/s
2)
Accelerometer
STB Harvester
-0.5
0
0.5
1
1.5
2
2.5
Vo
lta
ge
(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)
Accele
ration
(m
/s2)
-1
-0.5
0
0.5
1
1.5
2
2.5
3V
oltag
e (
V)
Accelerometer
STB Harvester
5 10 15 20 25 30 35 40
-80
-60
-40
-20
Frequency (Hz)
Pow
er/
freq
ue
ncy (
dB
/Hz)
0 5 10 15 20 25 30 35 40
-100
-80
-60
-40
Frequency (Hz)
Pow
er/
freq
ue
ncy (
dB
/Hz)
Accelerometer
STB Harvester
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Electrical Behavior of the IJP - STB Harvester Examples 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
17.5
29.541.4
65.2
time (s)
Accele
ration
(m
/s2)
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
Voltag
e (
V)
Accelerometer
STB Harvester
5 10 15 20 25 30 35 40-80
-60
-40
-20
Frequency (Hz)
Po
we
r/fr
eq
ue
ncy (
dB
/Hz)
5 10 15 20 25 30 35 40-80
-60
-40
-20
Frequency (Hz)
Po
we
r/fr
eq
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
ration
(m
/s2)
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3V
oltag
e (
V)
Accelerometer
STB Harvester
0 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 40-80
-60
-40
-20
Frequency (Hz)
Po
we
r/fr
eq
ue
ncy (
dB
/Hz)
Accelerometer
STB Harvester
ΔY=3 mm and Accmax=34.4 m/s2 @6Hz
Smart&Authonomous Sensing Systems @SensorLab
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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
ea
k [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
eak
[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
norm
RMSVAvPeakV and 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 Hz 8 Hz
10 Hz
12 Hz 14 Hz
6 Hz 8 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
Smart&Authonomous Sensing Systems @SensorLab
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