Mais conteúdo relacionado Semelhante a Synched E Harvesting Wireless Sensors For Sensors Expo 2009 Dist (20) Synched E Harvesting Wireless Sensors For Sensors Expo 2009 Dist1. Synchronized Energy Harvesting
Sensor Networks
S.W. Arms*, J.H. Galbreath, C.P. Townsend,
D.L. Ch hill N
D L Churchill, Nam Ph ^
Phan^
* President, CEO ^Division Head (Acting) Structures
MicroStrain,
MicroStrain Inc Structures Division - AIR 4 3 3 2
4.3.3.2
Williston, Vermont Naval Air Systems Command
www.microstrain.com Patuxent River, Maryland
swarms@microstrain.com.
Proc. Sensors Expo, Rosemount, IL, June 9h, 2009 © microstrain, inc. 2009 all rights reserved
2. Sensing
the Future
Wireless sensors, in the billions, will become
deeply embedded within structures &
machines.
Sensed information will be automatically
compressed & forwarded for condition
based maintenance.
© microstrain, inc. 2009
5. Solution:
• Harvest & store energy from strain
strain,
vibration,
vibration, motion, thermal gradients,
light, electromagnetic fields
light
• Use power management to balance the
energy “checkbook”
“checkbook”
• Use embedded processors to compress
data,
data compute fatigue life
© microstrain, inc. 2009
6. Bell M412 Installation
Strain energy
harvesting wireless
pitch link installed on
Bell M412 Feb 2007
(1st time ever)
Patents pending © microstrain, inc. 2009
7. Flight
Test
Results
• Passed
– in-flight EMI evaluations
in-
– rotor track & balance verification
• Data were collected wirelessly on board the
aircraft with no indication of data loss
Patents pending © microstrain, inc. 2009
8. Objective: Demonstrate a synchronized,
energy harvesting, wireless structural health
harvesting
monitoring & reporting system for helicopters
© microstrain, inc. 2009
Patents pending
9. Detailed
D t il d
Objectives
• Develop a wireless data aggregator (WSDA), capable of
synchronizing wireless/hard-wired sensor networks and
wireless/hard-
aggregating data with open architecture communications
to HUMS
HUMS.
• Document time synchronization accuracy
• Develop a high sample rate wireless sensor node for
helicopter gearbox apps.
• Demonstrate system compatibility with a scalable
network of active RFID
t k f ti RFIDs.
11. MicroStrain’s Wireless Sensor Networks
(IEEE 802.15.4)
( 802.15.
Time Division Multiple Access Frequency Division
(
(TDMA) &
) Multiple Access (FDMA)
Carrier Sense
Multiple Access (CSMA)
© microstrain, inc. 2008
12. How many nodes will this
low power TDMA system
support?
Aggregate sample rate (Hz):
~10,000/total no. sensor channels
10 000/total no
i.e.: ~100 single ch nodes can
i 100 i l h d
transmit data at 100 samples/sec
Patents pending © microstrain, inc. 2008
14. Previous Work
• Le Cam, V., “Synchronization of Wireless Sensors:
Review of Methodologies, Experience Feedback of the
Very Precise GPS Solution”, Third European Workshop
Solution
on Structural Health Monitoring, July 5-7, Granada,
5-
Spain, July 5-7, 2006
5-
Placed GPS receivers at each wireless node
to achieve absolute precision of 1
microsecond
15. Data Aggregator collects
gg g
time synchronized data
w/ 4 GB removable flash memory
All wireless nodes use precision nano-power real time clock
p p
(RTC) with +/- 3 ppm (-40 to +85 deg C) time reference.
Wired inertial sensor uses same time reference as Data
Aggregator.
Data Aggregator’s RTC uses Global Positioning System
’ C Gl b l S
(GPS) as time reference. Data Aggregator sends beacons to
update time sensing node’s time keepers
p g p
Patents pending © microstrain, inc. 2009
16. Timing Engine Overview
• Timing
Ti i engine provides th
i id the
following:
GPS
• 1pulse per second Receiver
CAN
CAN Nodes
CAN Nodes
CAN Nodes
CAN Nodes
(PPS) Synch Clock Controller
• Trigger Line Timing
Ti i
Wireless Wireless Nodes
• Extremely accurate Engine
Controller
Wireless Nodes
Wireless Nodes
Wireless Nodes
absolute time keeper
• The 1 PPS synchronization
y Wireless Wireless Nodes
Wireless N d
Wi l
clock is distributed to CAN Controller Wireless Nodes
WirelessNodes
Nodes
and 802.15.4 network
802.15.
controllers. (green) µP Core
running
Linux USB Node
SYNCH CLK & TRIG
• In turn, network controllers
turn USB N d
Node
CAN Synch Mechanism
propagate the 1PPS clock to
nodes through a high-priority
high- RS-232 Node
Wireless Synch Beacon
broadcast beacon packet. RS-232 Node
(blue and orange)
Patents pending © microstrain, inc. 2009
18. Vibration vs. Strain Energy Harvesters:
gy
Gearbox Resonant Energy
G b R tE
Harvester Output: 37 mW
Volume: 4.3 cc
Weight: 38 grams
Flexible Strain Harvester Output:
~14 uW per sq cm (90 uW per sq in)
@ 200 uE p-p, 4.3 Hz
p p,
On Bell 412 Pitch Link 12 patches
delivered ~ 1 uW/lb (200-400 uW)
Weight: 4.3 gr/patch*12 patches = 52 gr
Patents pending © microstrain, inc. 2009
19. Sensing strain
strain,
force, pressure,
force pressure
torque, vibration,
torque vibration
temperature
Wirelessly
20. MicroStrain’s embedded firmware
optimized for strain gauges
• Wireless offset adjust
• Wireless gain adjust
• Wireless co t o o sa p e rates
e ess control of sample ates
• Wireless shunt cal – bits to microstrain
• Low tempco’s:
tempco s
tempco’s:s:
offset: -.007%/C , span: .015%/C
015%/C
• Mux’d, pulsed & regulated bridge excitation
Mux dd,
Patents pending © microstrain, inc. 2009
21. Wireless Pitch Link Strain
& Load Sensing Nodes
Fractal antennas
Shear-Link ™
© microstrain, inc. 2009
Patents Pending
22. Pitch Link Consumption for Various
Operating Modes:
O ti M d
• Mode 1: Wait until stored energy crosses threshold: nanoamp
threshold:
comparator turns circuit “on”. Predetermined amount of data
transmitted. Consumption varies with available energy, timekeeper
draws 9 microwatts.
• Mode 2: Data logged to memory: Download at end of test.
Consumption @ 32 samples/sec: ~100 uwatts
• Mode 3: Transmit if energy allows: Log 100 samples, check stored
energy, transmit if possible. Consumption with 32 samples/sec: ~250
uW,
uW, drops to 100 uW without radio transmission.
• Mode 4: Real Time Transmission: Log 100 samples, then transmit.
Consumption with 32 samples/sec: ~250 uwatts.
uwatts.
© microstrain, inc. 2009
Patents pending
24. High Speed Wireless Node
• Programmable sample rates,
g p
offsets,
offsets, gains, & anti-aliasing
anti-
filters
• A/D resolution: 16 bits
• 100 KHz A/D sampling rate (3
ch,
ch, simultaneous, full diff)
• Event consists of 125,000
samples (or 0.4 seconds at
100 KHz sample rate)
• Stores 1 million samples on 2
MB embedded, non-volatile
memory
Patents Pending © microstrain, inc. 2009
26. Powering down between
g
samples greatly reduces
power consumption
Patents pending © microstrain, inc. 2009
27. Embedded routines allow
microelectronics to
adapt to
the
th amount of available
t f il bl
energy
© microstrain, inc. 2009
Patents pending
28. Average power consumption
g p p
(mW) for 50 kSPS data
mW)
acquisition
i iti
Acquisition Interval
Sample 1 min 10 min 1 hour 1 day
y
duration
(sec)
0.1 1.67 0.22 0.09 0.06
0.5 8.09 0.86 0.19 0.07
1.0
10 16.1
16 1 1.66
1 66 0.33
0 33 0.07
0 07
© microstrain, inc. 2009
30. Broadcast Synchronization
Results (4 nodes)
• Waveform at right shows
g Scope traces
4 captured waveforms
representing the start of
sampling for each of the 4
p g
nodes.
• Note that each node
starts sampling at slightly
different times. In this
specific case the last
case,
node started sampling
~3.4 microseconds (µsec)
after the first node
node.
© microstrain, inc. 2009
31. Broadcast Synchronization
Results
Scope traces
• After repeating the
broadcast trigger
command 250 times, the
d ti th
timing differences are
bound within an envelope
of ±4 µsec. This
represents the initial
synchronization accuracy
for the group of nodes.
© microstrain, inc. 2009
33. Saw tooth Input, room temp.
2 nodes, 2 h
d hours @ room t
temperature,
t
clock drift: ~325 us (45 ppb) between the two sensor nodes
Timing beacon sent once – at start of test only.
Node 1 & Node 2
Sensor Data Overlay
3
2.5
ensor Input (V)
2
1.5
1
Se
0.5
0
7199.94
7199 94 7199.96
7199 96 7199.98
7199 98 7200.00
7200 00 7200.02
7200 02 7200.04
7200 04 7200.06
7200 06 7200.08
7200 08
Time (seconds)
© microstrain, inc. 2009
34. Saw Tooth Input, -40 to +85 deg C
2 nodes 2 hours w/ 10 Hz Sawtooth: clock drift 5.71 msec (793 ppb)
nodes, hours, 5 71
w/ 1 Hz Sawtooth: clock drift 5.04 msec (700 ppb)
Timing beacon sent once – at start of test only.
Node 1 & Node 2
Sensor Data Overlay
3
2.5
Sensor Input (V)
2
1.5
1
0.5
0
7199.70 7199.72 7199.74 7199.76 7199.78 7199.80 7199.82 7199.84
Time (seconds)
© microstrain, inc. 2009
35. Timing Results Summary
• Synch beacon sent once - at start of test only - provided
~5 ms timing accuracy over 2 hours, subjected to -40 to
+85 C.
• Synch w/ periodic (60 sec) beacon provided +/- 50 us
timing accuracy over 13 hours, subjected to -40 to +85 C.
g y , j
• Conservative approach: send resync beacon every 5
minutes to achieve sub millisecond timing accuracy when
sub-millisecond
temperatures are extreme and changing rapidly.
© microstrain, inc. 2009
36. Conclusions
• Accurate time synch developed for wireless
sensor nets that doesn’t require GPS.
• System supports high sample rate (50 KHz)
sensor nodes, and active RFID tags
• Provides open architecture interface to HUMS
to eliminate wires and enable reductions in
weight and complexity.
Patents pending © microstrain, inc. 2009
37. Conclusions (continued)
• High sample rate nodes can operate
perpetually, without batteries, from gearbox
vibration alone.
• Supports remote reporting over mobile phone
networks (satellite reporting currently under
development).
development)
• These capabilities, coupled with appropriate
wireless security methods, will enable critical
structural sensor data to be managed remotely,
securely, and automatically.
Patents pending © microstrain, inc. 2009
38. Need More Info?
• Sensors Expo Booth 1005
• www.microstrain.com
• www.microstrain.com/customer-docs.htm
www.microstrain.com/customer-
• swarms@microstrain.com
@
40. References:
• M.J. Hamel et al., Energy Harvesting for Wireless Sensor Operation and Data
Transmission, US Patent Appl. Publ. US 2004/0078662A1, filed March 2003
• D L Churchill et al., Strain Energy Harvesting for Wireless Sensor Networks,
D.L. Ch hill l S i E H i f Wi l S N k
Smart Structures and Materials, SPIE, vol. 5005, pp. 319–327, 2003
• S.W. Arms et al., Shaft Mounted Energy Harvesting System for Wireless
g g
Sensor Operation and Data Transmission, US Patent Appl. Publ. US
d l bl
2005/0017602A1, filed Jan 2004
• S.W. Arms et al., Wireless Strain Measurement Systems for Aircraft Test,
, y Test,
Aerospace Test Expo, Anaheim, CA, Nov 2006
• S.W. Arms et al., Energy Harvesting Wireless Sensors for Helicopter Damage
Tracking, American Helicopter Society Annual Forum, Phoenix, AZ, May 2006
g, p y , , , y
• S.W. Arms, C.P. Townsend, D.L. Churchill, M. Augustin, D.Yeary, P. Darden,
Augustin, D.Yeary,
N. Phan, Tracking Pitch Link Dynamic Loads with Energy Harvesting Wireless
Sensors, AHS 63 d Annual Forum, Virginia Beach, VA, May 2007
S 63nd A lF Vi i i B h VA M